Modelling and control of static synchronous series compensator interfaced with DFIG-based wind farm using PSO for SSR alleviation

Abstract

Subsynchronous resonance (SSR) in wind turbine generators interfaced with series compensated transmission line has been explored in recent few years. Instead of torsional interaction (TI), the induction generation effect (IGE) prompts SSR in such systems. The mitigation of SSR using flexible ac transmission system (FACTS) devices like a thyristor-controlled series capacitor (TCSC), gate-controlled series capacitor (GCSC), static var compensator (SVC) and static synchronous compensator (STATCOM) has been researched in the literature. However, in wind turbine generators, the efficacy of static synchronous series compensator (SSSC) to mitigate SSR is relatively less explored. This paper presents mathematical modelling of SSSC and a study of hybrid series compensation of transmission line using SSSC and fixed series capacitor (FSC) to diminish the SSR effect in doubly-fed induction generator (DFIG)-based wind farm. The values of controller parameters of SSSC for SSR mitigation are identified using particle swarm optimisation (PSO) and compared with the Ziegler and Nichols (Z–N) method. Results obtained through PSO are more precise and finer than the conventional approach. The eigenvalue analysis and fast Fourier transform (FFT) analysis are shown to demonstrate the damping offered by SSSC to SSR oscillations along with transient simulations. The impact of SSR at different compensation levels and wind speed is examined, and the effectiveness of SSSC for SSR mitigation is illustrated using the hybrid compensation method. The risk of SSR is high at low wind speeds and a high compensation level. In such instances, it is shown that SSSC is capable of effectively alleviating SSR.