Multi-Disturbance Factors Analysis and Suppression Strategy of Sub-Synchronous Oscillation on DFIG Grid-Side Converter

This paper focuses on the power grid oscillation of grid-side converter (GSC) in doubly-fed induction generator (DFIG) caused by grid sub-synchronous oscillation (SSO), and designs a measure to improve the output power quality of GSC. Firstly, the influence mechanism of multipath disturbance of GSC under SSO is sorted out, and the disturbance factors and action modes are clarified. Secondly, the influence of SSO on the output estimation of phase-locked loop (PLL) in the control strategy and power calculation process is analyzed. Furthermore, the mathematical model of GSC output power considering the influence of PLL is established. At the same time, the key factors of SSO for GSC power oscillation suppression strategy are determined by analyzing the oscillation suppression effect of quasi-resonant controller when SSO amplitude, frequency and phase change. Based on the above theoretical analysis and research, the resonant controller is used to eliminate the estimation error of the PLL; at the same time, an adaptive algorithm is designed according to the mechanism analysis of SSO characteristic changes to improve the fixed resonant frequency of the quasi-resonant controller, and a DFIG-GSC sub-synchronous power oscillation suppression strategy based on the adaptive quasi-resonant controller is proposed, thus eliminating the influence of SSO on the multipath disturbance of GSC and improving the power quality of its output. Finally, the effectiveness of the proposed suppression strategy is verified by simulation and experimental results.