EXCITATION CONTROL-SYSTEM FOR USE WITH SYNCHRONOUS GENERATORS

An optimal excitation control strategy for a synchronous generator is derived using Lyapunov's direct method and the nonlinear system equati ons. The control strategy requires neither phase compensation nor wash -out circuits characteristic of standard power system stabilisers (PSS ). By using a nonlinear system model, the control strategy is optimal over a wide range of rotor angle and swing frequency changes. The exci tation control system required to implement the control strategy is hi erarchical and has a different structure to the traditional excitation control system with PSS. In the proposed structure a primary controll er damps quickly any power swings using the synchronous EMF as the fee dback signal. A secondary controller maintains constant generator volt age by adjusting the reference value of the synchronous EMF fed to the primary controller to that required by the actual operating condition s. The proposed excitation control system has been tested on a single generator-infinite busbar system with the simulation results showing e xcellent damping of power swings over a wide range of operating condit ions whilst retaining good voltage control.