Co-ordinated control of synchronous generator excitation and static VAR compensator

The application of multivariable control to a synchronous generator excitation and static volt-ampere reactive (VAR) compensator system is described to design a coordinated excitation and firing angle discrete controller. It is based on a reduced-order linearized model, obtained by system identification, which represents the nonlinear dynamics around a specified operating point. The model structure was investigated by simulation studies indicating that a third-order representation was suitable. Direct comparisons of identified model responses with corresponding results from the nonlinear model show that accurate modeling can be achieved by this approach. Quantitative assessments also established that the models are satisfactory. The controller was evaluated by simulation of a nonlinear generator model, involving comparisons between the coordinated controller with several different controllers, over a wide range of operating conditions and disturbances. It is shown that the coordinated control arrangement can provide better stability, voltage control, and damping than the other schemes