Mechanism analysis and simulation for STATCOM damping subsynchronous oscillation

STATCOM exclusively for subsynchronous oscillation(SSO) mitigation use is presented in this paper, which is based on sinusiodal pulse width modulation(SPWM) for subsynchronous voltage. The fundermental principle and damping characteristic are analysed for STATCOM damping SSO by complex torque coefficient approach and frequency scanning method. The analysis result demonstrates that if the phase difference between system voltage of access point and voltage of STATCOM satisfies some condition, STATCOM can provide maximal positive damping. The controller of STATCOM is designed by dq transformation, which can mitigate SSO and maintain voltage on dc side of inverter by active and reactive power decoupled control. The simulation result reveals that this kind of STATCOM can mitigate SSO effectively.