COORDINATED CONTROL OF SYNCHRONOUS GENERATOR EXCITATION AND STATIC VAR COMPENSATOR

This paper presents a new control approach for designing a coordinated controller for a synchronous generator excitation and static VAR compensator system. The objective is to extend the operational margins of stability, whilst satisfying control requirements by introducing an integrated multi- variable controller to control both the generator exciter and the firing angle of the thyristor-controlled reactor of TCR-FC compensator. The system dynamics are modelled in terms of measurable state variables and control inputs. This is achieved by using unbiased recursive least squares identification. On the basis of this identified model, the synthesis of a coordinated optimal controller is achieved by minimizing a quadratic performance index using dynamic programming techniques. This avoids the difficulties arising in coordination of static VAR compensator and synchronous generator. System behaviour under transient conditions is assessed by examining the response to three-phase short circuits, and dynamic transient stability boundaries. The results present comparisons of the system performance with different controllers, over a wide range of operating conditions and disturbances using a detailed non-linear simulation. It is shown the coordinated control arrangement can provide better stability, voltage control and damping than the other schemes.