H_∞ Power System Stabilizer Design Based Swarm Particle Optimization Algorithm

With the development of the society, the size of power system is expanding. Heavy-load and long-distance transmission lines are increasing constantly, and the fast excitation system and AVR are widely used. All the development makes the problem of Power System Low Frequency Oscillation more and more significant. Therefore, it is important to study on how the low frequency oscillation influences the power system stability.Generator excitation control has always been paid close attention as the important method to maintain the system stable. Under this background, Power System Stabilizer (or PSS) is used as additional control of the excitation system. Most of the traditional power system stabilizers are designed according to a linearized power system operating point. While the operating point changes, the performance of the power system stabilizer which was designed by original operating point could be weakened.Based on this situation, this article focused on the research of following contents.(1) After the compare among several control methods which deal with nonlinear condition such as:robust control, adaptive, neural network and fuzzy control, the H∞control theory which has completed theory system in robust control theory was chosen as the theoretical basis to design power system stabilizer.(2) The small disturbance analysis model which is based on Heffron-Philips generator model was chosen as the designing model. Considering the system interference and the nondeterminacy of system, the mixed sensitivity problem was chosen as the designing objective of H∞control. The problem of the weighting function was solved through PSO optimization algorithm. The objective function of PSO optimization algorithm is based on the ITAE criterion which considered the system performance. The weighting function which was obtained by optimization and the small disturbance analysis model constituted the generalized controlled object of mixed sensitivity problem. H∞power system stabilizer was solved according to the generalized controlled object.(3) Established single machine infinite bus system simulation model based on MATLAB/Simulink to optimize the weight function parameters and test the performance of completed H∞controller through the model. This article simulated the situation such as:step disturbance on excitation voltage reference terminal, three-phase short circuit, three-phase broken circuit, power operation point changed. The simulation results indicated that power system stabilizer which was design through H∞theory can effectively increase damping to weaken low frequency oscillations in the simulation experiments and achieved good results with excellent robustness.