Suppression Effect of TCSC on Sub-Synchronous Oscillation of Grid Integrated DFIG

Wind power resources are remotely distributed in China. The fixed series compensation (FSC) is one of the traditional methods to solve the problem of long-distance power transmission of the doubly-fed induction generators (DFIGs) based wind farm. The introduction of FSC will bring potential sub-synchronous oscillation (SSO) risks to the power system. With the development of flexible AC transmission system (FACTS), thyristor-controlled series compensation (TCSC) has become an effective substitute for FSC due to its suppression effect on sub-synchronous oscillation. This paper mainly studied the natural and active suppression effect of TCSC on sub-synchronous oscillation of grid integrated DFIG. Based on the frequency scanning method, the impedance characteristics of TCSC and DFIG were obtained to study the natural suppression effect of TCSC, and some key parameters were discussed. However, when the system was particularly weak, the natural suppression might not keep the system stable. Thus, an additional sub-synchronous oscillation damping control (SSDC) was proposed as active suppression of TCSC, which could further enhance the stability of system. The frequency scanning results showed that the SSDC could effectively improve system stability. Finally, the electromagnetic transient simulation results in PSCAD/EMTDC verified the above conclusions.