Enhanced voltage control and load compensation for DFIG-based wind energy systems using a stator-side series converter

Abstract

The increasing deployment of doubly-fed induction generator (DFIG)-based wind energy systems (WESs) requires effective voltage regulation and power-quality enhancement under varying operating conditions. This paper proposes a coordinated voltage regulation and load-compensation technique using a rotor-side converter (RSCR) and a stator-side series converter (SSSCR). The RSCR provides two-directional slip-power control through cascaded voltage and current control loops, while the SSSCR provides series voltage injection for voltage regulation and load compensation. The proposed system is developed in MATLAB/Simulink and validated using an OPAL-RT OP4512 real-time platform under variable wind speed, unbalanced and non-linear loading, and voltage sag/swell conditions. Quantitative results show reductions in overall current total harmonic distortion (THD) of 25.34% and 36.78% under non-linear and unbalanced load conditions, respectively. The voltage regulation error is reduced from 9% to 3%, while the settling time decreases from 0.24 s to 0.12 s under non-linear loading. The proposed configuration also reduces the voltage overshoot from 2.61% to 0.02% during speed transition. These results demonstrate the effectiveness of the coordinated RSCR-SSSCR configuration for simultaneous voltage regulation and load compensation.