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High switching loss remains a predominant issue in conventional finite control set model predictive control (FCS-MPC) for voltage source inverter, aside from the uneven distributed loss between upper switches and lower switches. While maintaining the inherent simplicity and effective reference tracking capability of conventional FCS-MPC, a new FCS-MPC is proposed to acquire substantial improvement in switching loss reduction by choosing the optimal zero vector and two active vectors. Selection of the two active vectors is performed by considering two legs that have maximum and minimum output voltage at particular sampling instant, while the selection of the optimal zero vector is based on the switching states of the previous sampling instant. The proposed method also ensures uniformly distributed loss in each phase as well as between upper switches and lower switches. Further switching loss reduction by selecting the appropriate weighting factor in the cost function is investigated for both the conventional and proposed methods as well. A loss model is constructed in MATLAB/SIMULINK for analyzing quantitative switching loss, conduction loss, total harmonic distortion, and number of switching. The proposed method ensured its superior performance under different load angles and sampling periods, and all the results are verified through simulation.
This paper proposes a novel method for determining optimal arrangements of overhead double-circuit power line conductors aimed to reduce electric and magnetic field emissions. Extremely low frequency electric and magnetic field optimization problems have multiple objectives. Multiple-objective optimization allows the simultaneous optimization of two or more conflicting objectives and determination of mutually non-dominated solutions. The multi-objective optimization technique used in this paper is based on Genetic Algorithm to obtain a set of mutually non-dominated solutions (Pareto optimal set) for the two objectives: the electric and magnetic field strengths near overhead double-circuit power line. Also, additional assessment criteria were defined for the selection of several decision scenarios from the Pareto optimal set. The results and practical aspects of the proposed methodology are demonstrated on two typical 400-kV double-circuit overhead power lines. The efficiency of the proposed multiple-objective optimization method is compared with the existing one based on single-objective optimization function. Copyright © 2016 John Wiley & Sons, Ltd.
Low-frequency oscillation occurs easily in a hydropower system with weak connected grid. Some oscillation behaviors cannot be explained by linear analysis method. According to unexplained oscillation frequency of hydropower stations, second-order oscillation mode of complex hydropower stations with weak grid is studied based on linear elastic model and modal series analysis method in this paper. Firstly, detailed hydropower station models with hydro-mechanical-electrical coupling are introduced. Especially, a new linear elastic model is used to model hydraulic conduit system. Secondly, hydro-mechanical-electrical coupling characteristics of hydropower stations are studied based on the whole model. Finally, the second-order oscillation mode and associated index of hydropower stations are calculated and studied by modal series method. Through numerical simulation of a single unit finite bus system, some useful results are achieved. Copyright © 2016 John Wiley & Sons, Ltd.
The paper proposes a novel time-domain statistical method to separate and analyze harmonics based on single channel analysis and principal component analysis. The proposed method separates the fundamental wave and harmonics to provide specific time-domain information. Two identification methods are proposed to estimate the number of harmonics within the power system signal, even with high noise. This paper validates the effectiveness of the proposed method through mathematical deduction and studies the selection of Euclidean embedding dimension. The robustness of the proposed method is tested on several simulated synthetic signals and a real-world signal. Simulation results show that the proposed method can detect harmonics with small amplitude in the presence of noise and has better separated waveform and less execution time than wavelet-packet transform and empirical mode decomposition. It is also shown that the proposed method can detect sudden voltage changes and separate disturbances.
The coil is used to detect partial discharge (PD) in the 3.3-kV motor. Because of the noise issue, most studies detect PD of the motor at the power bus or at neutral. However, we use three coils inserted in the slot of three motor frames to detect PD. This conflicts with conventional thought. For safety, the motor frame is always grounded to the earth. In addition, most people think it is impossible to detect PD on the grounded motor frame. Most researchers say we measure noise or high-frequency current on the motor frame. In this paper, we design an experiment to prove that what we measure is the induction magnetic field of PD. From the amplitude variation of the PD signal, the imperfect motor can be identified. Moreover, by measuring the PD signal and the three-phase 60-Hz waveform, we can determine the phase at which PD occurs. Copyright © 2016 John Wiley & Sons, Ltd.
This paper proposes the new concept of preplanned microgrid islanding (PMI) in the smart distribution system. PMI is a special form of controlled islanding that can be used to provide demand-side service for electrical users under the scheduled distribution operation, especially for the preventive maintenance. A simulation-based multi-objective optimization framework is developed to decide the starting time and duration of PMI. The optimization objectives include the minimization of load curtailment, operating cost, and pollutant emission. On one hand, the stochastic short-term simulation method is developed to assess the performance of candidate PMI schemes considering multiple uncertainties and optimal scheduling of microgrid operation. On the other hand, the weighted-sum approach is used to compromise the conflicting objectives according to the decision preferences of users. Furthermore, the response surface methodology is adopted to improve the efficiency of scheme selection with the help of experimental design technique and regression analysis. Finally, the effectiveness and high efficiency of the proposed method is verified in case studies. Sensitivity analysis is also performed to investigate the impact of decision preference, season scenario, and sizing alternative on optimization result. Copyright © 2016 John Wiley & Sons, Ltd.
This paper proposes and investigates the online application of generator-derived real-time voltage stability assessment indices in large interconnected power systems. The indices are based on synchrophasor measurements from synchronous generators and are used in the prediction of the system's margin to voltage collapse in real-time. Comparative analyses are carried out between the newly proposed indices, an existing effective generator reactive power reserve index, and two line-based indices. Results obtained from testing the proposed indices on the New England 39-bus test system show that the proposed indices are simple to implement, more responsive to system dynamics and provide a more accurate estimation of the system's margin to voltage collapse compared with the existing indices.
Furthermore, the suitability of the proposed indices for small disturbance voltage instability and large disturbance voltage instability conditions were demonstrated. In addition, the proposed indices are subsequently deployed on a programmable logic controller for real-time closed-loop testing with the real-time digital simulator. Copyright © 2016 John Wiley & Sons, Ltd.
This contribution presents a time-domain methodology for harmonic state estimation of power systems with nonlinear loads based on the extended Kalman filter (EKF). The output variables measurements to be used in the state estimation algorithm are selected from the simulation of the propagated harmonics in the system with an under-determined condition of the measurement matrix. The state estimation results are compared against the actual time-domain system response; both results closely agree hence verifying the effectiveness of the EKF to solve the time-domain power system state estimation. Several sampling frequencies and measurement noise are applied to assess the effects on the state estimation process, the error covariance matrix, residuals and on the execution time. Copyright © 2016 John Wiley & Sons, Ltd.
If sensitive loads are connected to the point of common coupling (PCC), compensation should be carried out in order to reduce PCC voltage harmonics. In this case, compensation is performed by the interface converters of distributed generation (DG) units. In this paper, a novel method is proposed for voltage harmonics compensation in islanded microgrids. The proposed method is capable of adjusting compensation percentage in proportion to the existing level of distortion at PCC. Also, this controller provides a proper sharing of compensation workload, considering the nominal capacity of DGs, which will improve the sharing of nonlinear load. Also, to decrease the asymmetry among phase impedances of microgrid, a novel structure is proposed to generate virtual impedance. At fundamental frequency, the proposed structure for the virtual impedance improves the control of the fundamental component of the power, and at harmonic frequencies, it acts to adaptively improve nonlinear load sharing among DG units. In the structures of the proposed harmonics compensator and the proposed virtual impedance, a self-tuning filter is used for separating the fundamental component from the harmonic components. This self-tuning filter decreases the number of the phase-locked loops. The simulation results in MATLAB/SIMULINK environment show the efficiency of the proposed approach in improving load sharing and decreasing voltage harmonics. Copyright © 2016 John Wiley & Sons, Ltd.
Optimal placement of parking lots with optimal scheduling in power systems to maximize the benefit, considering different peak load states and different electricity prices for each state, is studied in this paper. The effectiveness of the proposed technique is tested on the IEEE 33-bus distribution test system with considering the power system constraints and using genetic algorithm. This algorithm selects the optimal sites and sizes (number of electric vehicles) of these parking lots and shows the optimal results. The results of these simulations with genetic algorithm demonstrate that the economic problem of parking lots placement depends on many items such as number of the electrical vehicles (EVs) in each parking lot (capacity of parking lot), state of charge of EVs, as well as the electricity price in peak/off-peak periods. Moreover, it is suggested that the existence of parking lots, considering adequate incentives for EVs owners, has economic benefit for distribution network operators, reduces total power loss, and can improve the distribution system voltage profile. Also, the number of parking lots to be allocated in a distribution system supports the distribution system at peak load hours because it is more interesting from economic point of view to install more parking lots.
With the development of wind energy, many wind turbines have been fed into the distribution system. Considering that many wind turbines have the capability of reactive power support, which are represented by the doubly fed induction generators, a reactive power optimization model of the distribution with wind turbine is proposed. In order to solve the combinatorial optimization problem, an improved self-adaptive differential evolution algorithm is developed. In the algorithm, the mutation direction is guided by elite group, which can greatly improve the algorithm convergence rate. Then a self-learning strategy that self-adaptively adjusts the individual mutation rate and crossover rate is introduced in the process of individual evolution; the robustness of algorithm is increased. To avoid the difficulty in selecting penalty function coefficient, Deb criteria is used to deal with the constraint limits. The effectiveness of the model and algorithm has been verified on modified Institute of Electrical and Electronics Engineers (IEEE) 33-node system and PG&E 69-node system. Copyright © 2016 John Wiley & Sons, Ltd.
The recently proposed techniques for detection and classification of different faults are amenable to statistical-based methods such as correlation or alienation coefficients. In this paper, an improved alienation coefficient-based classification algorithm is proposed. In the method, a modified alienation coefficient formula is suggested, by which different faults could be identified more accurately. Switching of heavy loads is also considered in the proposed algorithm. The performance of the method is evaluated by simulation of a typical power system in different conditions. The results confirm high capabilities of the proposed method for detection and classification of different faults. Furthermore, the results are verified using a low-scale test bench system in the laboratory. Copyright © 2016 John Wiley & Sons, Ltd.
In an islanded microgrid mode, the use of conventional power flow method is not effective as the voltage of slack buses and the frequency of the microgrid is assumed to be constant. Such assumption fails to consider the real characteristics of an island microgrid as all distributed generations (DGs) are involved in providing the demand of active and reactive power as well as in maintaining the frequency of the microgrid. In this paper, a novel algorithm for the power flow problem in an island microgrid is proposed. The problem is modeled without any slack bus by considering the steady state frequency as one of the power flow problem variables. To model different control modes of DGs, such as droop, PV and PQ, in an islanded microgrid, a new formula for power flow equations is developed. A hybrid optimization method is developed, by adopting imperialist competitive algorithm (ICA) and genetic algorithm (GA), to minimize the objective function including total active and reactive power mismatch in an island microgrid. Copyright © 2016 John Wiley & Sons, Ltd.
The paper is aimed to analyse the influence of the degradation, in the course of time, of pipelines insulating coating in the frame of power frequency electromagnetic interference generated by power lines on buried metallic pipelines. To our knowledge, such an issue is generally not considered when evaluating induced voltage and current along the pipe-earth circuit; on the contrary, such a phenomenon should be taken into account because under certain conditions, the level of the electromagnetic interference can significantly vary during the pipeline life (some tens of years). In the paper, we propose an empirical law to describe the degradation in the course of time of the pipe insulation resistance to soil, and we show, by means of simple examples of interference calculation, why such a degradation should be taken into account. Copyright © 2016 John Wiley & Sons, Ltd.
Deregulation in power systems has created new uncertainties and increased the previous ones. The presence of these uncertainties causes the transmission network to remain monopoly and the private investors not being interested in investing in this section. This paper presents a new merchant-based transmission expansion planning (TEP) formulation from the viewpoint of private investors. The information-gap decision theory (IGDT) is used to model the inherent uncertainties associated with the estimated investment cost of candidate lines and the forecasted system load and NSGAII is utilized to solve the multi-objective optimization problem. This algorithm helps private investors to select the best lines for investment in the presence of uncertainties. In order to verify the effectiveness of the proposed method, it has been applied to the IEEE RTS 24-bus system and the simplified Iranian 400-kV transmission system. Copyright © 2016 John Wiley & Sons, Ltd.
The dynamic economic emission dispatch (DEED) of power system occupies a decisive position in the process of energy conservation and emissions reduction. DEED incorporating valve point effect of generator units is a dynamic multi-objective non-convex optimization problem with the characteristic of nonlinearity, strong-constraint, and multi-peak. This paper proposed a new modified non-dominated sorting genetic Algorithm-II with selection based on dynamic crowding distance and new controlled elitism to solve DEED, which can guarantee the diversity of population under the premise of elitism of population. A deep analysis about blocked evolution produced by heuristic operation which is used to handle the complicate constraints is executed, and a modified heuristic operation based on forward search operator has been firstly implemented to solve the problem. A new membership function has been defined to describe the superiority–inferiority of the individuals in the Pareto set, from which the best compromise solution is selected. Finally, case studies were carried out with the classic 10-units test system. The simulation results demonstrate the better global search and better results acquirement capability of the proposed modified non-dominated sorting genetic Algorithm-II comparing with existing non-dominated sorting genetic Algorithm-II. Copyright © 2016 John Wiley & Sons, Ltd.
Ground fault in the rotor winding of generators can cause serious damage to the generators and consequently, to the power plant. This paper proposes a practical online technique to determine the ground fault location in the rotor winding of a synchronous generator. The proposed technique is based on the analysis of the measured voltage and input/output currents of the rotor winding. The main distinguishing feature of the proposed technique is that, contrary to the existing technique, it is applicable to various types of excitation system. The accuracy and applicability of the proposed technique is demonstrated through both computer simulations and experimental tests. The experimental tests have been carried out using a new device which works based on the proposed technique. The results show that the proposed technique can determine ground fault locations with a higher accuracy compared with the existing techniques. Copyright © 2016 John Wiley & Sons, Ltd.
Electrification of heating and cooling of residential and commercial buildings is one of the key solutions in decreasing consumption of fossil fuels and emission of greenhouse gasses. One of the main equipments that plays an important role in this regard is the heat pump, which has the efficiency of more than 100%. In this paper, the effect of using electrical heat pump (EHP) in generation scheduling of an energy hub for supply of cooling, heating, and electrical loads of a building is investigated. Also, the effect of cooperation of EHP and co-generation system in improvement of energy performance of the energy hub is evaluated. The goal of presented mixed-integer nonlinear programming model that plans the energy hub for the next 24 h is minimization of operation costs. In order to scrutinize the role of EHP and the performance of presented model, six cases are considered for the energy hub in two sample summer and winter days in which the energy hub supplies cooling and heating loads via electricity only, fuel only and their combination. The results show that the presence of EHP whether in cooling section or heating section plays an important role in decreasing costs and fuel consumption. Furthermore, operation work points of co-generation system and variations of the combined heat and power operation scheme with the presence of EHP in the energy hub are precisely investigated. Copyright © 2016 John Wiley & Sons, Ltd.
Effective phasor measurement unit (PMU) placement is a key to the implementation of efficient and economically feasible wide area measurement systems in modern power systems. This paper proposes a pragmatic approach for cost-effective stage-wise deployment of PMUs while considering realistic constraints. Inspired from a real world experience, the proposed approach optimally allocates PMU placement in a stage-wise manner. The proposed approach also considers large-scale wind integration for effective grid state monitoring of wind generation dynamics. The proposed approach is implemented on the Danish power system projected for the year 2040. Furthermore, practical experience learnt from an optimal PMU placement project aimed at PMU placement in the Danish power system is presented, which is expected to provide insight of practical challenges at ground level that could be considered by PMU placement software developers as well as for future research in this field. Copyright © 2016 John Wiley & Sons, Ltd.
The physical phenomenon of electromechanical disturbance propagation has been modeled in the form of a wave. Usually wave has dispersion features while propagating with a nonlinear medium. In this paper, the dispersion relation of discrete- and continuum-model for the power system is derived. And then, the influences on dispersion characteristics of different factors (such as generator internal reactance and transmission line resistance) are studied. The relationships of the propagation velocity and attenuation characteristics of disturbance with the power grid's parameters are revealed. Finally, this paper shows simulations based on a chain system and a New England benchmark system to help to validate the rationality and accuracy of the theoretical analysis. This work is helpful to analyze the electromechanical oscillations of power systems and control the propagation of disturbance. Copyright © 2016 John Wiley & Sons, Ltd.
In this paper, the impact of surge arresters and ferromagnetic ring on the magnitude as well as the steepness of lightning overvoltages in gas insulated substation (GIS) are investigated. This investigation is carried out through modeling of a typical 380-kV GIS using ATP/EMTP for very fast transient overvoltages. Two scenarios of lightning strikes, backflashover and shielding failure are considered. Also, the impact of ferromagnetic ring on the surge arrester performance is evaluated. The evaluation is carried out considering surge arresters located at entrance, and at transformer terminals of GIS. Finally, the effect of ferromagnetic ring parameters on the arresters performance is evaluated and discussed. The obtained results show that the presence of ferromagnetic ring can affect the rating selection of GIS surge arresters. Copyright © 2016 John Wiley & Sons, Ltd.
This paper proposes a solution methodology for optimal allocation and sizing of renewable based DG units in radial distribution systems. The objectives are to minimize total power losses, to minimize system's investment cost and to improve voltage stability. The multi-objective genetic optimization algorithm is used to generate the optimal Pareto front and a fuzzy decision making function is used, as a hybrid function, to obtain the best compromise solution. The proposed technique is applied to typical IEEE bus systems including 33-bus system, 69-bus system and 119-bus system. This technique is implemented using different scenarios including all possible combinations of renewable DG units; to prove the effectiveness of the proposed methodology. The effect of DG based renewable energy allocation on the most sensitive buses to collapse is also carried out considering different load models. Copyright © 2016 John Wiley & Sons, Ltd.
This article presents a method to consider the probabilistic nature of load impedance and harmonic currents by designing a multi-step inductive-capacitive (LC) compensator consisting of switchable units thus assuming that a single unit is not sufficient to ensure satisfactory results. The proposed algorithm divides the time period into sub-regions according to the scheduled number of switchable units over which the multi-step LC compensator is optimized through different performance criteria; maximizing the power factor (PF), minimizing the transmission loss (TL) or minimizing the voltage total harmonic distortion (VTHD); as objective function resulting in lower variance, and hence, the more accurate expectation is obtained. Genetic algorithm (GA) is used to estimate that steps while holding the performance quantities at the corresponding desired values and constraining the compensator values which would create resonance. Also, the manufacturer's standard values for power shunt capacitors with/without equal steps are considered. GA is a search mechanism based on the principle of natural selection and population genetics. The contribution of the proposed procedure is demonstrated in examples taken from previous publications. Finally, simulated results show that the multi-step LC compensator provides a considerable improvement in the performance in case of the probabilistic condition. Copyright © 2016 John Wiley & Sons, Ltd.
Utilization of AC/DC distribution networks has become more reasonable because of the recent developments in power electronic devices and increasing employment of DC electronic loads. In this paper, load flow calculation problem in AC/DC distribution networks is addressed. Because a large number of load buses in both AC and DC parts and high R/X ratios in the AC part of these networks can lead to the divergence of recent Jacobian matrix based methods, in this paper, a new direct approach based on backward forward sweep algorithm is presented. Comprehensive investigation considering weakly meshed and different types of converters and their control strategies is also carried out. The presented algorithm is applied to the test systems equipped with different types of converters. The results demonstrate the validity and capability of the proposed method.
A new method to identify the location and nature of the harmonic generating sources in a distribution system has been proposed. The method is based on wavelet decomposition of voltage and current signals at the point of measurement. Detail reactive power at level 1 of wavelet decomposition has been used. A harmonic generating load is identified by extracting its characterizing harmonics in the power system signals. The pseudo-frequency for the wavelet decomposition at level 1 is set at the characteristic frequency of the load, and the sampling frequency is so chosen that the desired harmonic information can be extracted at the detail level 1. Power systems signals are, however, captured at a higher sampling frequency. For the identification of the disturbing source, the required sampling frequency for level 1 decomposition is obtained using downsampling on the captured data. Applicability of the method has been demonstrated for both radial and non-radial power system networks.
The role of Demand Side Management programs in maximizing the benefits of electricity market participants is underlined in recent decades. After power system restructuring, Demand Side Management has been divided into Demand response (DR) and energy efficiency programs. Developing Demand Bidding (DB) program enables the widespread participation of smart customers and usually is implemented as a market-driven program while Emergency Demand Response Program (EDRP) is usually implemented as a reliability-driven program. The impacts of employing these DR programs, that is, EDRP and DB, on market clearing price have been investigated in this paper. A nonlinear model for DR program is proposed considering both EDRP and DB program. The effectiveness of the proposed model is evaluated on the Garver network and Institute of Electrical and Electronics Engineers (IEEE) 30-bus test system through running a numerical study.
In this paper, design and prototyping of two-speed capacitor-run single-phase axial-flux induction motor (AFIM) for direct-drive applications is presented. The proposed structure has single stator-single rotor configuration with high magnetic pull between the stator and rotor, which may compel rotor to lock. Although the most efficient method to overcome this problem is using a second rotor or stator in the mirror with the first one, it is not applicable in low-cost applications. So, in this paper, two new and fast construction techniques are proposed to fabricate an AFIM with extra low air-gap length and minimum cost. Beside design and optimization process, a thermal equivalent circuit considering radial and lateral heat transfers is proposed. Then different losses and thermal resistances are exactly calculated to estimate the temperature rise of different motor parts and the maximum specific magnetic and electric loadings. Then, motor performance is evaluated using three-dimensional time-stepping finite-element analysis. Finally, a comprehensive fabrication algorithm for AFIMs is presented, and a prototype of the studied motor is fabricated and tested. The experimental results validate the design, optimization, thermal model, and finite element simulations.
In recent years, wind energy has a remarkable growth, and the power systems tend to increase the integration of wind power source. However, the existing power systems are not compatible with the effects resulted by the highly integrated wind power sources. Because of the transmission congestion, available produced wind power is not able to be fed into the grid. This paper presents the application of flexible AC transmission system (FACTS) devices for mitigating the wind power curtailment. A framework of multi period optimal power flow problem (MPOPF) is derived for a wind integrated power system. FACTS devices are utilized in such a way that the total wind curtailment during a specific time horizon is reduced. The proposed MPOPF is tested on modified IEEE 30-bus load flow test system. It is shown that the amount of curtailed wind power is significantly reduced when FACTS devices are optimally allocated.
In this paper, a novel Multi-objective Modified Binary Particle Swarm Optimization (MBPSO) algorithm is used to solve the transmission expansion planning (TEP) problem. Minimization of total investment cost and power loss are the objective functions of this problem, which are modeled by fuzzy sets. The problem is transformed into a mini-max case with an improved human–machine interface. According to the technical merits of HVDC system, HVDC links is introduced as a candidate solution for TEP problem. Finally, the proposed algorithm is tested on two test systems, and the HVDC links effects on TEP problem are investigated. The simulation results demonstrate that these lines play an important role in the reduction of network loss and subsequent investment costs.
An alternative solution for power regulation of doubly fed induction generators is proposed in this work by a proper combination of passivity-based controllers with algebraic approaches for online estimation of system parameters and mechanical torque. Our proposal shows that the stability property of the original closed-loop system is preserved, without the restriction of explicitly knowing the parameters and mechanical torque of the induction generator. A performance evaluation study is performed on the passivity-based power control scheme considering typical/normal operation conditions for the electrical power generation system, namely active power generation with either demanded or delivered reactive power. Analytical and numerical results prove the effectiveness of the power control scheme combined with the proposed real-time estimators of parameters and torque.
This paper proposes a dual timescale active power coordinated scheduling framework to accommodate large scale wind power integration. This framework is composed of rolling scheduling, real-time scheduling and storage control. The optimization model of rolling scheduling policy is presented, which is activated every 30 min using the renewed forecast to modify the day-ahead scheduling curve. Also the optimization model of real-time scheduling is put forward, which is triggered every 15 min using the renewed forecast to modify the output of balance generators. In addition, the optimal storage control strategy is presented. The efficiency of the dual timescale active power coordinated scheduling framework is verified via the IEEE RTS bus system. Copyright © 2016 John Wiley & Sons, Ltd.
A new Wide-Area Monitoring System (WAMS) application for monitoring inter-area oscillations, based on the Newton-type algorithm is presented in this paper. The core of this novel WAMS application is a numerical algorithm for the real-time estimation of the dominant inter-area oscillation mode, which processes Global Positioning System synchronized information obtained from Phasor Measurement Units installed in the power system. The parameter model is a highly nonlinear function, making this a particularly difficult challenge. Two data sets were tested using the new algorithm, one based on simulated models and the other based on real-life data records. The computer simulated model was based on a known architecture with signals obtained using a dynamic simulation of a multi-machine power system. The real-life data records used information collected on the FlexNet Wide-Area Monitoring System (FlexNET-WAMS) installed in the Great Britain power grid. Copyright © 2016 John Wiley & Sons, Ltd.
The increasing penetration of flexible AC transmission system devices and renewable generation resources within existing conventional power system networks has necessitated the relook into protective relaying schemes for ensuring grid security and integrity. This paper investigates the impact of a unified power flow controller (UPFC) on Zones 1 and 2 (with infeed current) of the conventional distance relay and pilot protection schemes. Using both analytical and detailed simulation techniques, these schemes have been very thoroughly assessed. The protection impacts for four functions of UPFC are compared with each other comprehensively. The infeed current effect for existing distance relay, as represented by standard MHO characteristics, has been adapted to factor the effect of source and line impedances. In addition, a proposed modification procedure highlights the main reasons for the impedance trajectory changes during faults at Zones 1 and 2 resulting due to the presence of the UPFC. A detailed model of UPFC and six measuring units of distance protection have been developed in the MATLAB/Simulink environment. The accuracy of compensated network and impedance measuring units are verified using Opal-RT's RT-LAB real-time engineering emulator.
Integrated volt/Var control (IVVC) is an important tool to optimize voltage and VAR resources and improve energy efficiency and, therefore, plays an important role to support the smart grid vision. This paper investigates the application of support vector machines (SVMs) to control switched capacitor banks and voltage regulators of distribution systems in order to minimize system losses and maintain acceptable voltage profile. The objective is to develop an approach that can use voltage/current measurements provided by active and reactive monitors to IVVC control without the need to perform retraining or repeat optimization simulations. The performance of the SVM scheme for different input selection (i.e., active and reactive power and node voltage) is discussed. Moreover, the generality of the proposed SVM scheme is investigated under noisy environment as well as under network reconfiguration. Studies on a typical distribution system show that the proposed approach has been able to achieve satisfactory results. Copyright © 2016 John Wiley & Sons, Ltd.
This paper presents a novel multi-objective energy management method for a microgrid that includes renewable energy, diesel generators, battery storage, and various loads. The fluctuation of the grid tie-line power flow is regarded as one of the optimal objectives in order to decrease the power exchange between the microgrid and the main grid caused by intermittent and variable renewable resources. The uncertainty of renewable energy and loads is also considered in this paper. Stochastic optimization method is implemented for the output of renewable resources and controllable loads. Using the ε-constrained and weighted sum method, the multi-objective operation optimization problem, which includes the minimum microgrid operation costs, fluctuations of the grid tie-line power, and the risk management, is converted to a single-objective mixed-integer linear optimization problem. The scheduling is achieved for controllable units such as diesel generators, batteries, controllable loads, and grid tie-line power under various weights. The main contribution of the study is to achieve the energy management for a microgrid with regulation of the grid tie-line power fluctuations and peak shaving. Copyright © 2016 John Wiley & Sons, Ltd.
In this paper, a new sensitivity-based approach is proposed to minimize the load curtailment by optimal placement of series controller of the Unified Power Flow Controller (UPFC) in the power system. The proposed sensitivity factors are derived in terms of change in load curtailment with respect to change in UPFC series control parameters. The effectiveness of the proposed method has been investigated by formulating an optimal power flow problem with an objective to minimize the load curtailment. Results have been obtained on IEEE 14-bus and IEEE 30-bus systems. It has been shown that required load curtailment drastically reduced with placement of UPFC and could be effective in various operating conditions of power system. With this technique, a large amount of power curtailment could be avoided, hence, saved from revenue loss, social disobedience, and customer service interruption. Copyright © 2016 John Wiley & Sons, Ltd.
A single-phase cascade multilevel inverter is able to synthesize AC output voltages with considerably reduced harmonic distortion, which results in reduced size output filters. In addition, the amplitude of the output voltage in the cascade multilevel inverter topology is usually higher than in a single H-Bridge inverter, which makes possible the power injection into the grid without a voltage boost stage. These benefits make cascade multilevel inverter a suitable topology for PV applications. However, cascade multilevel inverters may exhibit large leakage ground current in a grid-connected PV transformerless system, which is caused by a variable voltage across the stray capacitances formed between the PV panel and ground. In this paper, a modulation strategy for the cascade multilevel inverter is proposed to deal with leakage ground currents arising in transformerless PV applications. Numerical and experimental results are performed to assess the effectiveness of the proposed modulation strategy in the reduction of leakage ground currents and improving the topology efficiency. Copyright © 2016 John Wiley & Sons, Ltd.
This paper presents a new stochastic security-constrained optimal power flow (SSCOPF) model to capture the uncertainties associated with transmission network failures. In the proposed framework, the uncertainties are modeled explicitly using scenarios and then managed through preventive actions (first-stage decisions) and corrective actions (recourse or second-stage decisions). The suggested model determines the optimal operating point considering the scenario weights, i.e., their probabilities. Both preventive and corrective actions are simultaneously optimized through the proposed SSCOPF approach. To reduce the dimensions of the SSCOPF model for large-scale power systems, an efficient iterative solution method is also presented. The effectiveness of the proposed approach is shown on the well-known IEEE 118-bus and 300-bus test systems. Copyright © 2016 John Wiley & Sons, Ltd.
The present paper deals with design, modeling and characteristics of a biomedical system. The involved biomedical system is a syringe pump generally used for continuous drug infusion. The syringe pump consists of a linear switched reluctance motor (LSRM) coupled to a syringe plunger. In order to determine the axial force to control the syringe plunger, it was necessary to begin by evaluating the thrust force. For that purpose, an analytical approach is developed to evaluate the different forces and pressures involved. In addition, an experimental bench was conceived to determine the thrust force and validate the analytical model of the syringe. Consequent results constituted the key element for designing and modeling the LSRM with the help of finite element methods (FEM). The final step is reserved to predict the dynamic performances of all the biomedical system with and without saturation. Copyright © 2016 John Wiley & Sons, Ltd.
This paper presents a virus-evolutionary differentiated-particle swarm optimization approach for short-term generation scheduling with uncertainties consideration. Different from the traditional power generation scheduling problems, the paper considers the characteristics of the change of atmospheric flow at day and night. This paper also considers the uncertainties in the load demand, available water in the reservoir, wind speed, and radiation. This paper studies on the best dispatch both economic and emission, which include two objective functions of generation cost and emission cost at different time periods. The proposed method that combines differentiated-particle swarm optimization with virus-evolutionary technique can expand the scope and increase the diversity of search. The study system comprises 10 thermal units, seven hydro units (including one pumped-storage hydro unit), one equivalent wind energy system, and one equivalent solar energy system. The results from the proposed method are compared with those from other intelligent algorithms. The test results show that the proposed method can indeed obtain a better solution. Copyright © 2016 John Wiley & Sons, Ltd.
A typical hybrid dual-infeed high-voltage direct current (HVDC) system includes two types of links—line-commutated converter (LCC) HVDC and voltage-source converter (VSC) HVDC in proximity. When faults occur in the LCC-HVDC side, the VSC-HVDC link sufficiently can compensate power to the LCC-HVDC system; thus, voltage fluctuation is suppressed. In recent years, the modular multilevel converter (MMC) has been a promising type of VSC. This paper presents a novel hybrid dual-infeed HVDC system consisting of an LCC-HVDC link and an MMC-HVDC link, and the two links are interconnected through a tie line between buses in the inverter side. The positive contribution of the MMC-HVDC link to the LCC-HVDC link in the area of commutation failure immunity index, effective short circuit ratio, voltage sensitivity factor, temporary overvoltage, and DC line fault recovery are investigated. Investigations show that the stability of system has been enhanced significantly with MMC, and the contributors are physical structure change and the control strategy of the MMC-HVDC system. The modelling and simulation of the steady state and transient performance of hybrid HVDC system are conducted in PSCAD/EMTDC. Finally, the simulation results verify the enhancement in sensitivity and stability of the dual-infeed HVDC system. Copyright © 2016 John Wiley & Sons, Ltd.
This paper presents the vibration reduction strategy of large-size pitch-controlled variable-speed wind turbine based on pitch control and torque control. First, the torque control below the rated operating area and the pitch control above rated operating area are presented, and the control method to reduce the coupling between torque control and pitch control is discussed. Then the vibration mechanism and the modal analysis of the main components (the blade, tower and drive train) of wind turbine are studied. In terms of alleviating the blade flap-wise vibration and drive train torsion vibration, the individual pitch control strategy and torque damping control strategy are proposed to reduce the fluctuations of blade flap-wise load and add damping to the drive train torsion vibration mode. Finally, simulations were conducted using the GH Bladed 1.5-MW wind turbine, and the results show that the proposed vibration reduction strategy can effectively alleviate the blade flap-wise vibration and drive train torsion vibration. Besides, because of the coupling relationship of blade/tower/drive train vibration modes, the proposed strategy can also mitigate the tower fore-aft and side-side vibration. Copyright © 2016 John Wiley & Sons, Ltd.
It is meaningful to study the wind power curtailments and absorption potentiality by considering different system states and time-varying characteristics. In this research, a wind power restriction analysis model and a maximum wind power connection (WPC) analysis model are developed to assess the wind power curtailments subject to different constraints and explore the potential of wind power absorption. A Monte Carlo simulation-based algorithm is utilized to evaluate the WPC in a hybrid power system. The proposed algorithms are solved by a MATLAB program with YALMIP and CPLEX. Based on two proposed models, advanced indices are proposed to measure the penetration level, the power curtailment, the potential of wind power absorption, and the utilization efficiency of wind power. The effectiveness of the proposed approach and indices is validated by a case study. The results indicate that the proposed method can discover the bottleneck of WPC and estimate the potential of absorbing additional wind power generation capacities in different buses, which is meaningful to determine ratings and locations for future wind farms. Copyright © 2016 John Wiley & Sons, Ltd.
With the increasing penetration of unregulated solar energy, a load service entity (LSE) can exert an externality cost to guide the charging behaviors of electric vehicle (EV) users and level the Duck Chart. This paper introduces a dynamic Stackelberg game model between LSE and EV users to analyze consumer behavior, and a complete information static game model to help LSEs increase profits by gaining share of the EV market. These dynamic and static game models are incorporated into a novel theoretic algorithm with mixed integer programming. A case study shows that the models and the proposed algorithm can level the Duck Chart and guarantee an LSE's share of the EV market. Copyright © 2016 John Wiley & Sons, Ltd.
With the tendency to move toward automated home energy management systems, the cooperative capacity of the smart grid "SG" became more and more significant. Distributed generation "DG", in addition to the novel patterns of electricity production, enabled the two-way energy flow. The concern of this paper is on introducing an automated control technique for optimizing the operational performance of the DG units within the residential applications. This problem is formulated in a constrained-nonlinear optimization structure based on a detailed economic system. Genetic algorithm "GA" technique is used to solve this problem by defining the optimal settings of the DG units. Availability of two-way communication and the use of smart meters will enable online implementation and facilitate data collection within a fully automated system. Based on certain tariffs and realistic load curves, many scenarios of operation are analyzed and assessed. The results show that using optimization technique in cooperative with advanced smart meters can enhance the economic situation of the overall grid significantly. Copyright © 2016 John Wiley & Sons, Ltd.
The paper presents a novel detection method based on feature extraction discrete wavelet transform (DWT) combined with artificial neural network (ANN) for identification of islanding condition in distributed generation (DG) system. Islanding detection methods can be classified into two major categories as active and passive methods. The main disadvantages of the passive methods are determined threshold value and related to their large non-detection zone. The emphasis of the proposed approach is eliminating the aforementioned drawbacks. The DWT allows revealing various hidden features of the signal. The aim of this paper is to determine the best wavelet basis function in order to identify islanding occurrence with higher accuracy and lower decomposition level. The proposed approach requires the measure rate of change of frequency at the DG's terminal, and various features are extracted from DWT then these features used as input into ANN. Also, the performance of the different structures of ANN such as feed-forward neural network, radial basis function, and probabilistic neural network are compared for islanding detection purpose. The proposed method is simulated and tested in various operation conditions such as islanding conditions, motor starting, capacitor bank switching, and nonlinear load switching. The test results showed that the proposed method correctly detects the islanding operation and does not mal-operate in the other situations. Copyright © 2016 John Wiley & Sons, Ltd.
Condition monitoring of vacuum circuit breaker is one of the important factors to determine its life time. This is through a close monitoring of the internal pressure of vacuum interrupter for vacuum circuit breaker conditioning. The rise of internal pressure exceeding a certain threshold value causes loss of current switching capability and electric insulating properties. In recent decades, many methods of determining internal pressure have been investigated to evaluate the influences of different parameters. Although most of them are based on experimental tests, none of them was satisfying and reliable to provide enough information about residual vacuum pressure. Thus, the field emission current is modeled and simulated in this paper using plasma modeling by particle in cell method in order to determine the correlation between current and vacuum pressure. The simulation results demonstrate that a more precise value of internal vacuum pressure is given by applying magnetic field with impulse current simultaneously in order to determine residual vacuum pressure. Copyright © 2016 John Wiley & Sons, Ltd.
With introducing demand response aggregator (DRA) in smart paradigm, small customers can actively participate in price and incentive-based demand response programs. This new matter can significantly affect many factors of power system such as transmission network security. Accordingly, it is notably useful to define an adjusted framework for transmission expansion planning in smart environment. A long-term market simulation is performed using a tri-level iterative framework to find the best expansion decisions for transmission company (TransCo) in a pool-based market. The TransCo's investment decisions are made by a merchant approach consistent with transmission network security and smart environment. The effects of smart environment on future network configuration, strategic bidding of generators in the market operation, and contingency analysis are considered during planning process. The effectiveness of proposed method is examined on the IEEE 24-bus system with one DRA, one TransCo, and two generation companies under the independent system operator's supervision. Copyright © 2016 John Wiley & Sons, Ltd.
Because of the capacity of satisfying the quality of service requirements of each traffic service in smart distribution networks, Ethernet passive optical network (EPON) technology is one of the primary technologies for establishing communication systems in smart distribution networks. This paper presents an improved weighted interleaved polling with adaptive cycle time (IW-IPACT) algorithm according to the quality of service requirement of different traffic classes, especially the requirement of the new protection and control technique. During a polling cycle, a virtual weighted buffer queue that meets the bandwidth requirements of the EPON was constructed. Thus, strict priority scheduling was used for the expedited forwarding service, and the weighted fair queuing scheduling was applied for the other services. In addition, to evaluate the real-time performance of the IW-IPACT algorithm, the upper bound for the packet delay of each traffic class was derived by using the network calculus method. The evaluation results indicate that the bandwidth utilization of the EPON was improved by using the IW-IPACT algorithm. In addition, the calculus and OPNET simulation results also show that the EPON can meet the real-time requirements of relay protection. Copyright © 2016 John Wiley & Sons, Ltd.
Asset management is one of the key components in a transforming electric power industry. Electric power industry is undergoing significant changes because of technical, socio-economical and environmental developments. Also, because of restructuring and deregulation, the focus has been on transmission and distribution assets that include transmission lines, power transformers, protection devices, substation equipment and support structures. This study aims to provide a detailed exposure to asset management classification, various interesting maintenance methods and theories developed. The work encompasses the issue of data management in recent years. Because of the use of various smart metering devices, large amounts of information are being collected. The advent of data-mining techniques has changed the asset management scenario, and it has been covered in this survey paper. In the end, it also discusses various risk assessment techniques in asset management developed and used for academic research and industries. It is accompanied with survey results from pan-European Transmission System Operator (TSOs) on various aspects in asset management. Copyright © 2016 John Wiley & Sons, Ltd.
This paper presents an analysis of three typical microgrid operation modes. First is the analysis of the grid-connected mode, in which the main goal is to optimize the microgrid operation (in terms of economics, carbon emissions and/or reliability) when it is connected with the main grid. Second is the analysis of the planned island mode, in which the main goal is to provide a stable and smooth transition from grid-connected to island mode while keeping both the frequency and the voltages within the required limits. Finally, the paper presents the analysis of the emergency island mode, which occurs after sudden islanding, in which the main goal is to maintain the energization of critical customers. The objectives and the operation strategies of microgrid management are different in each operation mode. This paper proposes a novel, centralized, multi-agent-based, microgrid controller architecture, which provides the coordination of all three operation modes and enables the easy configuration/combination of optimization goals that are subject to a given set of operational constraints. The microgrid controller consists of a real-time agent (responsible for closed loop control and maintenance of the system's frequency), an operation planning agent [responsible for near-term (15 minutes up to 24 hours) and short-term (1 to 7 days) optimization] and a state agent (responsible for overall monitoring, management and coordination of the other two agents). A microgrid controller with the aforementioned agents has been developed and tested. The simulation results are presented for a typical microgrid test example. Copyright © 2016 John Wiley & Sons, Ltd.
This paper presents a new control method for a stand-alone wind-based induction generator system with constant frequency and adjustable output voltage. The proposed generator system consists of a six-phase cage-rotor induction machine with two separate three-phase stator windings and a three-phase static synchronous compensator (STATCOM). The first stator winding is fed by STATCOM and is used to excite the machine, while the second stator winding is connected to the generator external load. The main frequency of STATCOM is determined to be constant and equal to load-requested-frequency. Because the frequency of the induced emf in the second stator winding is same as this constant frequency, the generator output frequency is independent of the load power demand and rotor speed. The conventional PI controllers are used to regulate both the generator output terminal and STATCOM dc-link voltages. Some simulation and experimental results are presented to prove the validity and effectiveness of the proposed control method. Copyright © 2016 John Wiley & Sons, Ltd.
The need to reduce greenhouse effect using distributed energy resources has significantly increased in recent years, particularly with the advent of deregulated market. Climate changes cause large swings in output power of renewable resources and the resulting fluctuations in frequency in the islanded microgrid (MG). To increase performance for a wide range of power system operating conditions, an energy management system is proposed based on a fuzzy fractional order proportional–integral–derivative (PID) (FFOPID) controller. It is able to analyze and simulate the dynamic behavior in grid-connected MGs. This controller is proposed in the MG encompassing distributed generation resources with "plug and play" ability. The performance of FFOPID controller is verified for frequency control purposes and to support internal bus voltage in both islanded and grid-connected operating modes in accordance with the failure time. Energy storage is used to improve the system dynamic response, reduce the distortion, and provide damping for frequency oscillations caused by renewable resources. Energy storage overload capacity is utilized for rapid initial control of frequency in MG. To achieve this goal, energy management system based on fuzzy decision mechanism combined with a PID controller and FFOPID is implemented according to the characteristics and limitations of overloading and state of charge. The obtained results show good performance of FFOPID controllers by improving the transient stability following a fault that has caused the islanded operation. Simulation results have validated the effectiveness of FFOPID controllers in the system under several scenarios with superior stabilization and more robustness in comparison with the fuzzy logic PID (FLPID) controller and PID controller. Copyright © 2016 John Wiley & Sons, Ltd.
This paper investigates the operation of a smart distribution system comprised of multiple microgrids during emergency conditions. It proposes a two-stage hierarchical scheme for outage management in such a system to enhance the security of supply during contingencies. This goal is achieved through sharing the available generation and storage capacities among different microgrids. In doing so, a well-organized framework is devised in order to introduce the roles and tasks of each player in operation stage of a multi-microgrids system. Based on this framework, the general optimization model that needs to be evaluated at each stage of the proposed outage management scheme is formulated. In this regard, a model predictive control (MPC)-based approach is proposed to determine the optimal scheduling policy of microgrids in the first stage. In the second stage, distribution system operator (DSO) as an independent entity coordinates the operation of different microgrids and schedules their unused generation/storage capacities for minimizing load curtailments in the whole system. This method captures the inherent uncertainties of outage duration and significantly increases the resilience of resulting schedule against prediction errors of load and renewable resources. Various features of this scheme are studied through implementation on a test system. The results verify the effectiveness of the proposed scheme in enhancing the reliability of distribution systems and demonstrate the benefits it will bring to both customers and DSOs. Copyright © 2016 John Wiley & Sons, Ltd.
A coordinated design of power system stabilizer and power oscillation damping controller for generator and STATCOM voltage regulators is presented. Because fuzzy logic has the potential to overcome the inherent limitations of conventional and analytical model-based design approaches, simple fuzzy logic controllers operating as power system stabilizer and power oscillation damping controller are used in this work to enhance power system stability. The coordinated design of these fuzzy supplementary controllers (FSCs) is formulated as a constrained optimization problem with a time-domain based cost function. The optimal set of controller parameters is determined by applying a simultaneous tuning approach based on bat algorithm optimization. Simulations of a two-area power system under several operating conditions and perturbations are carried out to validate the effectiveness of the proposed alternative in damping system oscillations. Performance of the proposed coordinated FSCs is compared with other coordinated and uncoordinated design approaches, including coordinated FSCs using genetic algorithm and particle swarm optimization. Copyright © 2016 John Wiley & Sons, Ltd.
The present work deals with social welfare maximization for energy scheduling. The parties involved in this study are a utility company, a distribution system operator and residential end-users. It allows the different participants to share a common electrical grid, without violating network constraints. A smart grid, equipped with a two-way communication system on a district level, is considered. For this purpose, each participant exchanges information, in order to establish a power consumption schedule that optimizes its own objectives, within the grid constraints. This strategy is illustrated on a district level to avoid overloading the distribution network. The consumption profiles of end-users consist of background consumption; some end-users are equipped with a heat pump and/or an electric vehicle, each of which is capable of responding to price variations. The impact of several tariff structures on the stability of the grid is explored. First of all, flat and day/night tariff structures are considered, and it is shown that price variation provokes load synchronization and leads to network overloads. Next, a real-time pricing tariff structure is used. If each end-user optimizes its behaviour to minimize personal costs, the grid is unable to supply all power during peak moments. In conclusion, if power constraints are imposed, the same grid can be stabilized, even if power demands increase by a factor of three or four.
In a final example, the impact of imbalance costs is examined. The cluster can be guided to maximize profits for the utility company from the imbalance mechanism. Copyright © 2016 John Wiley & Sons, Ltd.
Electrical type tests are a key step to verify the design of voltage source converter valves for a specific modular multilevel converter (MMC) high-voltage direct current (HVDC) project. For a high-power handling capability of modern insulated gate bipolar transistor (IGBT), it is very difficult to balance between type test quality and test rig investment. In compliance with IEC 62501 and CIGRE 447 requirement, this paper presents a kind of synthetic test circuits (STCs), consisting of a steady-state test circuit, an IGBT overcurrent turn-off test circuit, and a short-circuit current test circuit, used for operational tests on MMC-based IGBT valve sections. Using the STCs, the current stress, the voltage stress, the junction temperature, di/dt, the performance of the valve's electronic circuits, and the protection capability of the parallel thyristor can be validated. Further, the parameters of the test circuits can be adjusted with the number of submodules of the MMC test valve. Thus, the STCs are an economical alternative for testing a representative part of an MMC valve. The paper describes and discusses the type tests, completely performed with the three test circuits, on MMC valves for a Xiamen MMC HVDC scheme, which is rated at 1000 MW/±320 kV. Copyright © 2016 John Wiley & Sons, Ltd.
Introduction of smart grid has changed different paradigms in power industry. System-wide demand participation in power system operational planning is one of such influenced paradigms. To comply with these influenced paradigms, generation maintenance scheduling (GMS), as one of the operation planning processes, should be modified to adapt to the new changes. This paper proposes a new model to consider demand response (DR) in the GMS problem. The proposed GMS problem is modelled as a mixed integer linear programming problem and solved for the two known test cases, namely IEEE reliability test system and IEEE 118-bus test system. The results show that considering DR leads to more dispersed and uniformed generation unit maintenance schedules and lower overall system operation cost in comparison with the case in which DR is not considered. Copyright © 2016 John Wiley & Sons, Ltd.
This paper presents the technical aspects, theoretical analysis, and comparisons of two new permanent magnet synchronous generator (PMSG) grid-interfaced models named PMSG boost and PMSG rectifier-inverter. The exact feedback linearization (EFL) control scheme is used for the effective design and stability analysis of the aforementioned models. The complexity of the EFL control laws is discussed in the light of the nonlinear coordinate transformations and linearization (local and global) of the PMSG models. We also discussed the effectiveness of the EFL control over the output Direct Current (DC) link voltage of the PMSG during the electrical grid faults and the mechanical perturbations. Moreover, we compared the aforementioned models and concluded that the stability of the PMSG rectifier-inverter is higher compared with the PMSG boost during the variation of wind speed values from minimum to maximum. Furthermore, the robustness of the EFL control scheme for the PMSG rectifier-inverter is compared with the conventional proportional and integral controller and state-feedback controller. The EFL controller reports a faster output response, better accuracy, and quicker settling time of the output DC link voltage as compared with the proportional integral controller. Copyright © 2016 John Wiley & Sons, Ltd.
In this research study, Type-1 and Type-2 fuzzy logic controller-based model reference adaptive system speed estimator for direct torque and flux control with space vector modulation of a speed sensorless induction motor drive is proposed to replace the conventional proportional-integral controller. Initially, Type-1 fuzzy logic controller is developed, which is used to achieve high performance sensorless drive in both transient as well as steady state conditions. However, the Type-1 fuzzy sets are certain and unable to work effectively when higher degree of uncertainties in the system which can be caused by sudden change in speed or different load torque disturbances, process noise, etc. Therefore, a new Type-2 fuzzy logic controller-based adaptation scheme is proposed to better handle the higher degree of uncertainties along with enhancing the performance and also robust to various load torque and sudden change in speed conditions respectively. The detailed performances of various control schemes are carried out in MATLAB/SIMULINK with speed sensor and sensorless modes of operation when an induction motor drive is operating under different conditions, such as no-load, load, sudden change in speed and low speed respectively. To validate the different control approaches, an experimental prototype is developed and adequate results are reported for its validation. Superior performance has been obtained using the Type-2 fuzzy logic controller scheme in speed sensor and sensorless modes of operation compared with Type-1 fuzzy logic controller and proportional-integral controller based adaptation schemes respectively. Copyright © 2016 John Wiley & Sons, Ltd.
No abstract is available for this article.]]>
Ground impedance measuring elements (ground elements), which are responsible for removing single-phase-to-ground faults in distance relays, are highly prone to underreach when facing a significant resistance in the fault path. This paper proposes a new ground element with ensured dependability in high fault resistance conditions for the first-zone digital distance relaying of parallel lines. The proposed ground element functions on the basis of the fault distance and fault resistance it estimates, online during the faults, through the equation derived from the voltages and currents of the distributed-parameters line model. Hence, it will be particularly applicable to the parallel lines of long length in which the distributed parameters effect is significant. The proposed element requires only the data acquired at the relaying location. Further, its function is independent of the structural configuration of the system. Unlike conventional ground elements, the proposed element preserves its security in case of irrelevant-circuit as well as external faults. Simulation studies conducted in MATLAB and PSCAD/EMTDC examine the proposed ground element in a variety of influencing situations, and the results reveal that it accurately trips the faults in the first zone with no incidence of underreach in case of high resistance faults. The accuracy of the proposed element is over 99.4% and its tripping time within 0.3–1.3 cycles. Copyright © 2015 John Wiley & Sons, Ltd.
A phasor measurement unit (PMU) provides positive sequence components of bus voltage and currents of all lines connected to the bus. Current transformers (CTs) are connected to PMUs to scale down the current signals to an allowable level. At severe faults, the current may saturate the core of the CT leading to secondary current not proportional to the primary. It results in incorrect current phasor estimated by the PMU which may be substantially lower than the expected value. This will create problem when PMU data are used for online control/protection applications or offline analysis/diagnosis of power systems. In this paper a solution to CT saturation problem of PMU is proposed where currents of other lines are used to estimate the faulty line current (where saturation is expected). Different configurations are considered in the simulations to evaluate the performance of the method. Copyright © 2015 John Wiley & Sons, Ltd.
In extra/high-voltage power systems, electromagnetic transient phenomena (e.g. from switching events) are analysed by time-domain simulation based on Electromagnetic Transient Program-type simulation tools. For the particular combined power cable–overhead line studied in this paper, it can be time-consuming especially if the effect of design parameters are studied systematically. A tailored solution based on solving the system's impedance and admittance matrix in frequency domain can serve as alternative approach. It also allows for including design details, which can be hard to implement in Electromagnetic Transient Program-type simulation tools designed for general application. The method is applied to analyse transient behaviour (upon no-load energising and no-load switching surge response) of a mixed double circuit connection including a section with essentially four parallel cables per phase, regularly cross-bonded over a length of 10.8 km. It is validated by comparison with pscad/emtdc simulation. Copyright © 2015 John Wiley & Sons, Ltd.
Development of wind farms clustering exerts significant influence on secure operation of power grid and also puts forward new requirements for the capacity of peak regulation and frequency adjustment. When power grid frequency is higher than 50.2 Hz, active power output of wind farm should be reduced gradually according to the command from control center of power grid. To study urgent wind power curtailment in frequency adjustment level, math formula of frequency adjusted sensitivity index is deduced, which determines wind generator tripping strategy if the lopsided active power has occurred. Typical frequency adjustment time intervals are selected according to the relationship between frequency overshoot time and load variation as wind power gets curtailed. The annual wind energy curtailment in frequency adjustment level is estimated by selecting the most appropriate wind generator tripping and comparable with wind energy curtailment in peak-load regulation level on the basis of unit commitment model. Based on DIgSILENT/PowerFactory software, the effectiveness and feasibility of the proposed method are verified by taking China's a certain regional power network planning of 2020 as computational examples. Copyright © 2015 John Wiley & Sons, Ltd.
This paper analyzes the operation characteristics of the modular multilevel converter when the arms are asymmetrical with different sub-module number caused by sub-module faults. The research reveals the problems caused by asymmetrical arms, including the asymmetrical capacitor voltages, the asymmetrical direct current (dc) components of the arm currents, the asymmetrical circulating currents, the dc current fluctuation, and the voltage offset at the dc or alternating current (ac) side. Then, it is demonstrated by the theoretical analysis that the series of problems can be solved by rebalancing the fundamental frequency components of the upper arm voltage and the lower arm voltage. Therefore, a fault-tolerant control strategy is proposed by introducing a fundamental frequency resonant controller to the traditional second-order frequency proportional resonant circulating current controller. Besides, the research shows that the coordination of the proposed control strategy and the negative sequence current suppressing control can keep the output voltages of the three phases balanced. A 201-level modular multilevel converter–high-voltage direct current time-domain simulation model is established based on PSCAD/EMTDC, and the simulation studies confirm the efficiency of the proposed controller under balanced and unbalanced ac grid conditions. Copyright © 2015 John Wiley & Sons, Ltd.
The soil ionization phenomenon effectively reduces the grounding electrode resistance. The existing methods to determine the soil ionization effect on the transient resistance of a grounding electrode are valid only for homogeneous soils. However, most soil structures are non-homogeneous. Realizing the importance of the issue, this study proposes a hybrid method to incorporate the soil ionization effect on the transient resistance of a grounding electrode located in non-homogeneous soil condition. The electromagnetic field approach is utilized to compute the ionized soil volume around the electrode to determine the equivalent radius of the electrode. A circuit-based method of computing the grounding resistance of the electrode in non-homogeneous soil conditions is proposed based on the per-unit-length distributed parameter method. The proposed method is validated by using an electromagnetic field-based numerical solution for the non-homogeneity effect of the soil on grounding electrode resistance. Copyright © 2015 John Wiley & Sons, Ltd.
This paper proposes a bilinear robust state estimator (BRSE), which includes a linear programming problem and a quadratic programming problem with a nonlinear transformation in between. The main advantages of BRSE are threefold: (i) it can automatically suppress bad measurements in the estimation process effectively, thus possessing good robustness; (ii) it is globally convex, theoretically guaranteeing a global optimization for state estimator; and (iii) because no nonlinear iterative algorithms are required to solve the linearized model, there is no convergence problem. To further improve BRSE's ability to inhibit leverage bad measurements, this paper also proposes a robust weighted least absolute value estimation with optimal transformations, which can be directly used in BRSE. Simulations are conducted on a rudimentary 3-bus system for validating the proposed methodology and algorithm. Furthermore, benchmark systems including IEEE 9, 14, 30, 39, 57, 118, and 300-bus systems are tested to demonstrate the efficiency and reliability of our methodology and algorithm. Copyright © 2015 John Wiley & Sons, Ltd.
The increase of the scale and complexity of interconnected power systems leads to power system oscillations. Therefore, the electric network needs to be improved to be more stable. One type of flexible AC transmission system devices, namely, the thyristor-controlled series compensator (TCSC), can be placed in the transmission line to increase stability margins and dampen power oscillations by means of adjusting the impedance of the compensated line. The efficiency and robustness of TCSC controller depend on its optimal location in network. Hence, finding the optimal placement for TCSC has become a key issue. In this paper, a novel method based on a two-step approach is proposed to find the optimal location for TCSC. First, the energetic approach based on the combination of the controllability Gramian with the balanced realization reduction technique is applied to search feasible locations, and then the transient stability analysis is performed to compare and determine the optimal location through various test cases. The effectiveness of the proposed method has been demonstrated on the IEEE 39-bus England network. Copyright © 2015 John Wiley & Sons, Ltd.
In this paper a new model of radial basis function (RBF) neural network based on a novel stochastic search algorithm is presented for short-term load forecast (STLF). STLF is an important operation function in both regulated and deregulated power systems. Accurate STLF is effective for area generation control and resource dispatch as well as electricity market clearing. The proposed STLF method optimizes the structure of the RBF-based forecasting engine. Random selection of the number of hidden neurons may cause overfitting or underfitting problem of the network. For this purpose, a new stochastic search algorithm is presented to find the optimum number of neurons for the hidden layer. To demonstrate the effectiveness of the proposed STLF approach, it is tested on three real-world engineering case studies, and the obtained results are compared with the results of several other recently published STLF methods. These comparisons confirm the validity of the developed approach. Copyright © 2015 John Wiley & Sons, Ltd.
This paper proposes a methodology to model the external characteristics of a wind farm in service or in planning stage. For system operators, the interested external characteristics of a wind farm are mainly the aggregated available output that the wind farm can feed into power system. In order to accurately and efficiently model the wind production, the wind speed spatiotemporal distribution is characterized. The proposed model takes wake effect and time delay into account, which can improve the spatiotemporal resolutions of the input data provided by numerical weather prediction (NWP). In addition, the layouts and the mechanical characteristics of wind turbine generators (WTGs) are considered in the wind farm output model. How the operational statuses of WTGs influence the wind farm output is discussed. The proposed methodology is validated using the measurements and NWP data of an actual wind farm in China. The results demonstrate the effectiveness of the proposed method for modeling the external characteristics of a wind farm. The wind farm outputs provided by the proposed model can be used as the references for the generation scheduling or for planning of new wind farms. Copyright © 2015 John Wiley & Sons, Ltd.
A number of power quality issues such as poor power factor, harmonics, and unbalancing of load occur commonly at the distribution level. These power quality problems can be alleviated using a three-phase distribution static compensator (DSTATCOM). This paper presents the least mean square (LMS) based control algorithms for DSTATCOM for fixed and variable step sizes. Variable step-size LMS (VSSLMS) based algorithm involves the calculation of weights corresponding to the fundamental components of active and reactive powers. These weights are utilized to estimate reference supply currents from distorted load currents. It is shown that VSSLMS-based algorithm performs better than fixed step-size LMS in terms of static error and convergence. It is also shown by simulation and experimental results that VSSLMS-based algorithm provides satisfactory performance under various operating conditions such as dynamics of change in load and unbalancing. Copyright © 2015 John Wiley & Sons, Ltd.
Solving unit commitment (UC) problem is one of the most critical tasks in electric power system operations. Therefore, proposing an accurate method to solve this problem is of great interest. The original bacterial foraging (BF) algorithm suffers from poor convergence characteristics for larger constrained optimization problems. In addition, the stopping criterion used in the original BF algorithm increases the computation burden of the original algorithm in many cases. To overcome these drawbacks, a hybridized adaptive BF and genetic algorithm (HABFGA) algorithm is proposed in this paper to solve the UC problem with ramp rate constraint. The HABFGA algorithm can be derived by combining adaptive stopping criterion, BF algorithm and genetic algorithm; therefore, the drawbacks of the original BF algorithm can be treated before employing it to solve the complex UC problem. To illustrate the effectiveness of the HABFGA algorithm, several standard and real test systems with different numbers of generating units are used. The results of HABFGA algorithm are compared with the results obtained using other published methods employing same test systems. This comparison shows the effectiveness and the superiority of the proposed method over other published methods. Copyright © 2015 John Wiley & Sons, Ltd.
The goal of this paper is to optimize energy consumption, with minimum consumer interaction, and least impact on his/her life style, comfort and convenience. In the literature different demand side management (DSM) schemes are employed for consumer demand management. Till now, to the best of our knowledge none of researchers considered the consumers preferences, priorities, ease of use, grid stability, deviation minimization, demand curve flattening and implantation cost, collectively in a single management scheme. In this paper we proposed an innovative, cost-effective solution, to overcome most of the shortcomings of the previous solutions. In addition, it would also provide consumers' privacy as it would mask the energy usage pattern that combines psychological incentives in addition to economic benefits. The proposed Smart Energy-consumption Management System Considering Consumers' Spending Goal (SEMS-CCGS) can be used for optimized electricity consumption at any premises (residential, enterprise, commercial, etc.). The preliminary simulations showed 25.6% of electricity cost saving using SEMS-CCGS. The proposed system is appraised valuable by the utility companies whose focus is to shave peak loads. It also plays an important role in grid stability by improving the diversity factor and deviation of consumers load profile from available load curve. The simulation shows that deviation is minimized up to 45%. Copyright © 2015 John Wiley & Sons, Ltd.
This paper presents a risk-constrained model for large consumers to determine the optimal energy acquisition framework and the participation level in load-reduction programs based on the real-time pricing scheme. Additionally, the proposed pricing framework for the load-reduction enables the system operator to control the consumers' load reduction levels, according to energy prices. In competitive electricity markets, the uncertainty of hourly energy prices is the main problem faced by large consumers. Therefore, the information gap decision theory approach is addressed to manage the financial risk arising from uncertain prices. In this work, instead of profit maximization, the optimal robust framework is specified in a way that guarantees the desired profit. The robustness of the optimal procurement strategy is demonstrated by determining the variation interval of uncertain prices such that the profit associated with this strategy will be more than an acceptable threshold, which is defined by consumers. The performance of the presented model is analyzed via a case study. Copyright © 2015 John Wiley & Sons, Ltd.


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Pro Kabaddi League: Bengaluru Bulls edge past Bengal WarriorsBengal Warriors crashed to yet another defeat as they lost to Bengaluru Bulls 25-27 in the fourth season of the Pro Kabaddi League here at the Netaji Subhash Chandra Bose Indoor Stadium last evening. With this defeat Bengal Warriors hopes of making ... Business Standard, 1 week ago
Warriors come home - The Telegraph, 2 weeks ago
India Art & Gems Fair 2016 India's premier festival for art and jewellery - This Week Bangalore, 1 month ago
5 images for warriors in bangalore
Serjeant At Arms reigns supreme
Serjeant At Arms (A. Sandesh up) won the Kingfisher Ultra Derby Bangalore, the chief event of the races held here on Sunday (July 10). The winner is owned by Five Stars Shipping Co. Pvt. Limited represented by Mr. & Mrs. K.N. Dhunjibhoy and Mr. & ...The Hindu, 2 weeks ago Serjeant at Arms for Kingfisher Ultra Derby Afternoon Despatch & Courier, 3 weeks ago
RCB, RPS, Mumbai Indians agree to play IPL in United States: Report
Virat Kohli could soon be seen playing in front of the US crowd. Pictured: Virat Kohli of Royal Challengers Bangalore celebrates his century during an IPL match between Royal Challengers Bangalore and Kings XI Punjab at M Chinnaswamy Stadium in ...International Business Times India, 2 months ago IPL 2016: 'If Kohli doesn't get you De Villiers will,' Twitter bows down to ABD DNA India, 2 months ago Centurions De Villiers, Kohli go on record breaking spree Sify, 2 months ago De Villiers, Kohli hammer Lions as RCB win by record 144 runs Deccan Herald, 2 months ago
RM addresses unified Commanders Conference in New Delhi
Previous story: President meets scholars of IITs, IISc-Bangalore & IISERs attending In-Residence programme at Rashtrapati Bhavan Next story: Puducherry CM calls on Dr Jitendra Singh New Delhi; The Defence Minister Shri Manohar Parrikar has ...APN News, 1 month ago
Bangalore track: Anantara impresses
Anantara, Secret Dimension, Sea Fairey, Proserpine, Fresh Start and I Told You Know impressed when the horses were exercised here on Tuesday morning (June 21). Inner sand: 600m: Possimpossible (rb) 40. Moved well. 1,000m: Masada (S.K.The Hindu, 1 month ago
Cameron for Chief Justice Cup
BANGALORE RACES TODAY — CARD & SELECTIONS BANGALORE: There will be keen competion among John, Suraj Narredu and Sandesh. I feel Suraj is likely to do better than others. He has good mounts: In the Chief Justice Cup, Suraj Narredu on Cameron and ...Afternoon Despatch & Courier, 1 month ago Millrose with S. John up can win again Afternoon Despatch & Courier, 1 month ago
Thunder lead Warriors 3-1; updates from the French Open
Is the summer heat sapping you of your energy? Not in the mood to go through the sports news in detail, but can't quite get yourself to do away with it either? Here's what we have to offer: read on to get a summary of all the main sports events that ...The Hindu, 2 months ago Thunder thump Warriors; Suarez injured The Hindu, 2 months ago
Water warriors battle privatisation in thirst for justice
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Sevilla win Europa League; Warriors draw level with Thunder
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Challenging Bangalore royally
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Official Twitter account of Vancouver International Airport(YVR)
Face Tags
Fishy characters at YVR's international terminal keep an eye on holiday travellers
Look who was spotted shopping at the Duty Free in YVR, as he gets ready to fly North
The DJ is getting the party started for Vegas-bound pax today! Win tix to Vegas for 2, enter online at www.yvr.ca
Check out our snow clearing machines hard at work today. Things are running smoothly at YVR. www.yvr.ca
It took 611 balloons to lift Elvis off the ground! We're donating $5 per balloon to @QuestExchange
Elvis takes off from Van Art Gallery - look for him @yvrairport today. Thanks @AC_webSaver & @WestJet
Elvis is getting closer to 'lift off'. Guess how many balloons it will take. Check Van Art Gallery @ noon today.
Turn the heat on. Come get your party started with YVR outside the Vancouver Art Gallery.
There was intense comp. at YVR's pumpkin carving contest! Congrats to Michael Valeroso from UPS for 1st!
Monk's Grill bar is now open! After security in the Domestic Term. Welcome to the YVR family @MonkMcQueensVan
Photo Friday's are always better when they come before a long weekend! Kick off yours at YVR's newest Spot.
Ahoy, it's photo Friday! Any hunches on where these architectural hulls are located at YVR?
Photo Friday: This beast roams the runways eating FOD. Can you guess what FOD stands for?
Last day of #RoutesYVR, Here's a picture of where the magic happens and new routes are created
Photo Friday: Can you make head or tails of this pic? What three airlines are represented in this photo?
Friday's Photo: Have you ever seen the Northern Lights? Tell us where in YVR this photo was taken
Photo Friday: Tell us where you can find 6-tons of glass which create an ocean worth wading into.
The iconic green alligator sets up shop at YVR! Lacoste opens tomorrow in C Pier
Larry Berg, Stockwell Day, Gordon Campbell at YVR welcomes first Chinese tourists with approved destination status
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AMD A6-3500 APU with AMD Radeon 6530 HD Graphics 2.1/2.4GHz Socket FM1 65W Triple-Core Processor - Retail AD3500OJGXBOX
- Enter your model number to make sure this fits.
- Unrivaled, discrete-level DirectX 11-capable graphics and powerful AMD processor technology combined on a single chip.
- Unlike the competition, AMD A-Series APUs discrete-level graphics cores stay on when paired with select AMD RadeonTM HD 6000 series graphics cards.
- Dual-graphics capability enables improved speed, enhanced resolution and fast frame rates.
Customers Who Viewed This Item Also Viewed
Product Description
Customer Reviews
Top Customer Reviews
I was worried at first that the stock heatsink/fan would be too loud for an HTPC, but I was wrong. Even under full load, this thing is quiet and cool (I can barely hear it unless I put my head right next to the case). I think this is in part due to the fact it is only 65W TDP. Having the three cores is a nice bonus (would have bought the 4-core with 65W TDP if I could find it for sale...), but the three cores are more than enough for all multimedia, browsing the Internet, decompressing files, etc. Blu-Ray playback is butter-smooth as is all multimedia I've thrown at it.
All in all, a perfect processor/GPU combination for a great price that does everything I wanted it too very smoothly.
My HTPC build for those who are curious:
APEX DM-317 mATX Case w/275Watt PSU
ASUS F1A75-M Pro Motherboard
AMD A6-3500 APU (these APUs are perfect for HTPCs...get the lower TDP ones like the 65W to keep things cool and quiet)
Crucial 64GB m4 SSD (not really necessary, but the boot time is literally like 10 seconds)
2x Old MAXTOR 160GB SATA drives (RAID 0)
LG Blu-Ray Burner (not sure which model, I bought it like 2.5 years ago)
8GB Kingston HyperX 1600Mhz DDR3 (for 64bit Windows 7 Pro)
Enermax UC-8EB 80mm silent case fan
As regards productivity I have had no issues with APU performance. All of my office utilities load up lightning fast and I have had no crashes. Driver support is flawless in Windows 7. Just make sure to go online and install the latest drivers / Catalyst software directly from the AMD website; there is no need for third-party driver download software. As regards image software, I use GIMP for graphics editing, and this APU works wonderfully. Web browsing is fast, and DirectX support is up to date. Picasa software works lightning fast - no complaints here.
As for videos and entertainment, please note that I am not a gamer. I do watch 720p and 1080p h264 and x264 videos, though.Read more ›
Most Recent Customer Reviews
I bought this to fit into my HTPC since it was a good price. Decent speed, easy to install, and again a great price.Published on January 8, 2014 by brownsfan68
Very powerful APU! This is the heart of the HTPC I built to run XBMC on top of Windows. Runs Windows 7 without skipping a beat! Read morePublished on November 3, 2013 by SouthernHeaven
The product was received as ordered,sealed, promptly, and secure, very satisfied, I would recommend to all my friends and familyPublished on May 14, 2013 by Juan Cruz
This is my running my NAS system. It has been going great for the past couple months. The NAS is always on and is active quite a bit. This thing has kept up without missing a beat. Read morePublished on April 7, 2013 by J. S
Works great for a low budget htpc build. Running for about two months with no problems. Bought several more for simple work builds. Stock fan works fine but a little noisy.Published on January 23, 2013 by Amazon Customer
It works despite what is thought about it and it is faster as well. It is very dependable to say the least despite its cheaper construction.Published on January 22, 2013 by Amazon Customer
I was looking for a low power CPU and ended with this APU that says 65 watts. It runs very cool and under Windows 8 the speed while idle is just 0.80 GHz !!! and goes up to 2. Read morePublished on December 23, 2012 by Ernesto Ortiz Montella
I bought this to run an ESXI host on the cheap for some test virtual machines. It is currently running a 2012 server, 2008r2 file server, windows 7, and a pfsense box without any... Read morePublished on December 18, 2012 by Brian Buresh
I bought this to build a HTPC and was hoping that I'd be able to get a SteamBox out of it as well. I didn't get a SteamBox, but I got a great HTPC. Read morePublished on November 13, 2012 by Amazon Customer


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This post and giveaway were made possible by iConnect and Dreft. I was compensated for my participation in this campaign, but all opinions are 100% mine. If you have read recent posts here at Mama Bee Does you saw that my blog contributor, KC, is pregnant with her third child, this one, a little girl…. Continue Reading
Baby registry must haves #Amazinghood #giveaway
DC Super Hero Girls $100 Visa #giveaway
My boys have always loved watching their super hero cartoons and movies. Super heroes aren't just for the boys though. I'm glad to see DC Super Hero Girls bringing more girl power to the tv screen. If your kids are looking for action-packed girl power, look no further than DC Super Hero Girls. DC Entertainment's… Continue Reading
Domestic violence awareness month with HopeLine from Verizon #giveaway #HopeLine
Love shouldn't hurt. It can bring on a lot of emotions being in a relationship but fear and pain should not be words used to describe any relationship. I have had some cruddy experiences with relationships. I dated a guy who yelled at me all the time and made me feel like I was worthless…. Continue Reading
Warner Bros & DC Kids (5) $50 mystery gift baskets #giveaway
If you ask my boys what their favorite cartoons are I would bet my coffee supply that they would list Scooby Doo, Batman Unlimited, and DC Super Friends in their top 5 favs. I find myself watching the shows off the dvr even after the boys are off to school. I'm a bit of a… Continue Reading
Win a wardrobe of Karina Dresses $500 giveaway (US/CA) #dresstacular #frockstar #fashion
I am a frockstar ambassador for Karina Dresses. As part of that partnership I join my fellow frockstar bloggers in a giveaway twice a month for 6 dresses for our fans. Karina Dresses believes that they offer dresses for every body. I know they work for my body. I feel "average" but the fashion world… Continue Reading


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