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Nonlinear coordinated control of multi-machine power systems

This paper presents a novel observer-based nonlinear controller for the coordinated control of generators and thyristor controlled series compensators (TCSCs) in multi-machine power systems. The observer-based nonlinear control is basically on the input/output feedback linearizing control of a nonlinear system but using output feedback and perturbation estimation. A robust sliding mode observer is introduced to estimate system states and a fictitious state which is introduced to represent the combinatorial effect of system uncertainties and nonlinearities. The successful estimation of states and perturbation allows the input/output linearization of the nonlinear system without requiring an accurate system model. This constitutes a real-time compensation against the perturbations. Therefore, it is able to de-couple the global system into subsystems, include the external dynamics of subsystems for local control and provide satisfactory control performance in coordination with other machines or controlled equipment. Simulations studies are undertaken in a three-machine power system to evaluate the effectiveness of the proposed nonlinear controller. The simulation results show that the local controllers can coordinate each other to improve the power system stability.