Robust observer-based nonlinear control of multimachine power systems

A novel robust observer-based nonlinear controller (RONC) for excitation control of synchronous generators interconnected in a multimachine power system is presented. The RONC is developed based on a feedback linearising control strategy for nonlinear systems and it employs estimation of system states and perturbation. A sliding-mode observer is designed to estimate system states and perturbation which encompasses all the system nonlinearities and uncertainties. The successful estimates of states and perturbation are involved in the feedback control law, which enables a real-time compensation of system nonlinearities, to realise the feedback linearisation of the nonlinear power system. The RONC is robust in performance as its design does not require the exact knowledge of the power system. Moreover, the RONC is easy to implement as only one state is measured. The simulation study is carried out based on a three-machine power system. The results show that the RONC has better performance and robustness, under variations of power system operation conditions and disturbances, in comparison with a conventional nonlinear state feedback linearising controller (NFLC)