Abstract
This paper presents a novel nonlinear adaptive controller (NAC) for the co-ordinated control of generators and thyristor-controlled series compensators (TCSCs) in multimachine power systems. Discussions begin with power system de-coupling which is achieved by Lie differentiation. For each subsystem, the nonlinear adaptive control strategy is, at first, investigated based on the input/output feedback linearizing control. In this strategy, a fictitious state is defined to represent the combined effect of system nonlinearities, uncertainties and external disturbances and an extended-order sliding mode observer is employed to estimate the states and the fictitious state of the subsystem, which allows the NAC to be designed without requiring the knowledge of system nonlinearities and parameters. The NAC is then implemented locally, involving the external dynamics of the subsystem, which is estimated by the observer, for the co-ordinated control of generators and TCSCs in the multimachine power system. Simulation studies are undertaken based on a three-machine power system to evaluate the effectiveness of the NAC. The simulation results show that the locally installed NACs can coordinate each other to improve the power system stability.