Study On PSS Parameters Optimization Based On Hybrid Particle Swarm Optimization Algorithm

The size of power system network in China is still at its early stage. The connection between the areas is weak, the weak damping will appear under this circumstance, and low frequency oscillations are easy to be taken place. And this phenomenon threatens the safety operating of the whole system. The dimension of modern is becoming larger and larger, with the use of rapid high magnification excitation system low frequency oscillation has became one of the main problems of power system stability. Using power system stabilizers (PSS) in the power system, to suppress the low frequency oscillation, it is a beneficial method to solve the problem. As additional excitation, PSS handles the signals related to oscillation, and provides an additional signal to excitation system. Thus, generators will produce additional damping torque. It can compensate negative damping caused by oscillation. So, the low frequency oscillation will be suppressed, and the stability of power system will be improved.Once the parameters are not suitable, the control result will deviate from the optimal point decreasing the effect of PSS. PSS employed in power system, exists the condition that suppressing one main oscillation mode but worsening another at the same time, then deteriorating system further. Therefore, the optimization algorithms are needed to solve such problem, and coordinate the working state of PSS. Recently, various algorithms are used to optimize the PSS parameters, such as genetic algorithm, tabu search, and particle swarm optimization etc. But these methods have their defects in the process of application. To configure the parameters preferably, the paper chooses hybrid particle swarm optimization to concert PSS parameters.The article demonstrates the theory that how PSS suppresses low frequency, elaborates the mathematical model, optimization process and background of hybrid particle swarm optimization (HPSO). And then it uses HPSO to optimize PSS parameters. The model of optimization of PSS parameters are established in the thesis based on the model of single-machine with infinite-bus system and two-area four-machine system. Then simulation tests of the state of operating system are conducted by Matlab and results of various optimization algorithms compared in the paper. The results demonstrate that PSS using HPSO have better behaviors and can obtain the favorable performance under the disturbances and also can suppress the low frequency oscillation more effectively to maintain the system stability. Consequently, the validity and superiority of HPSO is proved.