An Optimal Variable Structure Stabilizer for Power System Stabilization

A technique for designing an optimal variable structure stabilizer is presented for improving the dynamic stability of power systems by increasing the damping torque of the synchronous machine in the system. The proposed variable structure stabilizer is optimal in the sense of minimizing a quadratic performance index in the sliding mode operation. A characteristic feature of this paper is that a systematic approach based on the linear optimal control theory is developed for the selection of the switching hyperplane of the variable structure stabilizer. The dynamic responses following a step disturbance by digital simulation are obtained by means of three types of controllers: the conventional power system stabilizer, the linear optimal stabilizer and the optimal variable structure stabilizer. Simulation results show that the optimal variable structure stabilizer yields better system dynamic performance than the others in the sense of having larger damping in response to a step disturbance.