Research On The Model And Control System Of Thyristor Controlled Series Compensator (TCSC)

Thyristor Controlled Series Compensator (TCSC) is the representative of the new technology of series compensators, and is the important composition of the Flexible Alternating Current Transmission System (FACTS) recent years. It can realize large-scale and smooth adjustment of the TCSC's impedance through changing the fire angle of the thyristors. So, under certain control strategies, TCSC can influence the electrical quantities of the line, such as the line power. Consequently, it can control the power flow, damp the power oscillation, improve transient stability and mitigate subsynchronous resonance of power systems.The fast and flexible line impedance adjustment function of TCSC offers good application opportunities for diversified advanced control theories. On account of several TCSC projects put into use at present still adopt traditional control strategies, the farther research should be made to investigate the influences of the different TCSC control strategies to the power system stability in order to make full use of TCSC.This thesis is devoted to the TCSC control system, an in-depth analysis and discuss are made on its layered model based on detailed research on TCSC module. It attempts to combine nonlinear optimal control and intelligent control as the TCSC control system in order to improve transient stability of power systems.Power system is a typically complicated, nonlinear and great system whose model can hardly be described accurately. Nonlinear control reflects the system's nonlinear and indeterminate characteristics. So, it has better flexibility, robustness and is suitable for TCSC system-layer control strategy as a global controller. Based on present research, the TCSC nonlinear optimal controller which has simple structure and uses local information is designed in this thesis according to the differential geometry theory. It doesn't need much calculation and remote control signals but can ensure the stability of the system after disturbances, which shows well dynamic quality.The performance of TCSC middle-layer controller affects the response speed and stability of the entire control system. Through simulation research, it is found that the conventional PID control, as the middle-layer controller, can basically follow and modify the ordering parameter, implement the impedance adjusting function. But, when the ordering parameter step greatly or the nonlinear relation between firing angle and ordering impedance become serious, the controller can't obtain well robustness. So, the composite control strategy with CMAC (Cerebellar Model Articulation Controller) and PID is introduced to TCSC middle-layer control in this thesis in order to improve the response performance of nonlinear inputs. The simulation results show that, because of the CMAC, the composite control strategy expedites the response speed, indicates the merits such as less error, better real time performance and robustness, and is suitable for nonlinear real time control in complicated dynamic circumstance.