Slope Optimization Of Multi-SVCs And Steady-state Impedance Simulation Of TCSC With Dual TCRs

Flexible AC Transmission Systems (FACTS) are adopted for load flow control,var compensation, stability control, transfer capacity improvement, and oscillationdamping. The fulfill of the expected function depends on controllers’ performanceand their coordination. As the typical variable-impedance FACTS devices, SVC andTCSC are widely applied in different power systems.This dissertation studies the FACST from different levels. The upper layer ofSVC is studies to corordinate their voltage control effect. The middle layer ofTCSC is studies and the dual-TCR TCSC is proposed to satisfy the bulk current ofextra high voltage transmission lines. The main contributions are outlined asfollowing:(1) Voltage control effect of the slope of the SVC is analyzed. Acoording tothe capacity and available margin, slope coordination for multiple SVCs are studiedusing time-domain simulation. The controller parameters are coordinated to controlthe var output. The coordination effect with different fault locations and loadingconditions are verified.(2) The time domain and the electromagnetic transient models of the dual-TCRTCSC are given, whose circuit characteristic is analyzed to quanfiy the impact ofthe firing angle on the branch current and fundamental impedance, and propose theimpedance table for the middle layer control.(3) Different control strategies for impedance tracking and current sharing aredesigned for various control variables. The impedance tracking model for TCSCwith dual TCRs is set up. The impedance curve with different control strategies areanalyzed to investigate the control law and improve the control strategy. Bycomparing the step response indices (including the rising time, the falling time,overshoot and the setting time, et al) of the impedance curve, the optimal controlstrategy is recommended. Detailed simulation is performed for the best controlstrategy.