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Improving Shunt Hybrid Filter Performance Through Reducing Control System Time Delay

Abstract This paper presents a new control scheme for shunt hybrid power filters that provides the capability of harmonics mitigation and reactive power compensation. The control system includes two main loops. The first control loop, which is responsible for harmonic mitigation, generates harmonic component of the active power filter reference voltage. In this control scheme no harmonic extracting circuit is used and, hence, it offers better filtering performances as compared with conventional control schemes of hybrid power filters. The second control loop is designed for reactive power compensation of non-linear loads. The magnitude of the fundamental injected voltage is controlled to adjust the reactive current of passive filter according to the reactive demand of loads, thereby making the line current in-phase with the system voltage. Frequency response of the shunt hybrid power filter is investigated by mathematical analysis and it is shown that the reduction of controller time delay improves filtering characteristic at high order harmonic frequencies. Computer simulations results, carried out for a typical distribution system with two non-linear loads, are presented to show fine steady-state and dynamic performances of the proposed controller.