Multiobjective Retuning the Power System Stabilizer (PSS) of a Real Power Plant in Iran Grid

The safe operation of power system depends on its stability and security supply in all times. The dynamic instability (small signal instability) is one of phenomena that results in power system instability and has been discussed as a challenge in power system control and operation from a long time ago. Commonly the dynamic instability appears as undamped low frequency electromechanical oscillations or with insufficient damping. In order to damp these oscillations and improve dynamic stability, the use of Power System Stabilizer (PSS) in excitation systems is the most effective option. In this paper the impact of PSSs of various units of a real power plant on Iran grid dynamic stability is investigated and its performance is improved. In this way first the excitation system and PSS model of the power plant are identified and verified, and then the main parameters of PSSs are optimally retuned using the proposed method based on Particle Swarm Optimization (PSO) algorithm. In the following, power plant operation is considered in different disturbances with respect to the retuned PSSs, so that, the effect of optimal parameters on local and inter-area oscillation modes damping is taken into account, not only within time domain analysis, but also within frequency domain analysis. The results of proposed flexible and comprehensive analysis display the suitable performance of retuned PSSs.