The Research Of Power System Low Frequency Oscillation Suppression With FACTS Devices

With the development of inter-area connection, the scale of power system is becoming larger with its structure more complicated. Its operation mode is closer to limit than ever before and this has brought some problems to the safe and stable operation of power system. The low frequency oscillation is an important one among them and is getting more and more attention.The inter-area connection of modern power system and the problems brought by low frequency oscillation were described in this paper. In the terms of occurring mechanism, analysis method and suppression measures, the research situation of low frequency oscillation was introduced. FACTS were introduced in details, including the official definition, the working principle as well as the research and the application situation of three kind of FACTS.The low frequency oscillation suppression with FACTS voltage modulation and power modulation was researched. The eigen-analysis of low frequency oscillation was introduced, and based on eigenvalue assignment, the principles of voltage modulation and power modulation was explained. An eigenvalue assignment algorithm based on states decoupling was proposed. In the algorithm, the state values of the original system was decoupled, and a dynamic feedback system with a symmetrical structure of the decoupled original system was designed. The feedback system parameters calculation method was also proposed in this algorithm. Experiment result on single-machine infinite-bus system has indicated the effectiveness of this algorithm.Aiming at the parameter design of practical FACTS, an parameter optimization method based on Prony analysis was proposed. An optimization mode was established, in which the dominant mode damping ratio derived from Prony analysis was introduced as the optimization objective and the modes amplitude ratio constraint was included. To solve the nonlinear optimization model, the improved PSO was proposed, in which to prevent the algorithm from being trapped into local optima, a chaos operation was introduced to improve the population diversity. To verify the effectiveness of the optimization method, simulation was done on IEEE4-machine-11-bus system. The results indicated that FACTS with optimized parameters can suppress the low frequency oscillation effectively.