Research On Interaction Analysis Of SVC And TCSC Controllers In Power Systems

With the development of power industry, the technique of Flexible AC Transmission System (FACTS) has been widely applied. The Static Var Compensator (SVC) and Thyristor Controlled Series Capacitor (TCSC) are the two most important elements of FACTS family, and they are usually used together to enhance the power system stability. According to the research studied by some lecturer, there could be interaction between the FACTS controllers in the complicated power systems. These interactions may impose negative influence, or even make the controller unstable. At present, the research for impact of interaction among power system controllers, especially FACTS controllers, is on elementary stage. There still are many problems to be explored. Therefore, exploring the new theory, new technology and new method, for enhancing the level of the security of the power system, have enormous economic and project significance. This dissertation can be summarized as follows.In the first part, based on the working principle and mathematic models of SVC and TCSC, an extended Phillips-Heffron model of a large-scale multi-machines power system installed with multiple SVC and TCSC is built. Upon this model, the mathematic relationships between the variables can be easily obtained, which makes a foundation for the simulation and the analysis on the next steps.In the second part, the existence of the negative interaction between the SVC and TCSC is proved in a 4-machine power system using nonlinear time domain simulation. The relative gain array (RGA) combined with NI theory is applied to assess the interaction between SVC and TCSC controllers. The method can judge the interaction between the SVC and TCSC controllers and indicate the stability of the system. Based on the RGA-NI combined analysis method, the influence caused by the electrical distance and time constant of SVC's the voltage regulator between the two devices is investigated emphatically. The detailed simulation results accord with the analysis results by the method, which demonstrates the effectiveness of the method in analyzing interactions of FACTS controllers.In the third part, an analysis approach based on relative interaction array (RIA) is introduced to the analysis the interaction between the SVC and TCSC controllers in power systems. Compared with the RGA, it overcomes the fault that the RGA can't exactly reflect the interactions when the elements are small. The simulation results validate the approach.