Harmonic mitigation in back-to-back doubly-fed induction generator (DFIG) converters becomes particularly challenging when the machine-side switching frequency is reduced to minimize switching losses. In this study, the rotor-side converter's switching frequency is lowered from 3 kHz to 2 kHz, causing conventional space vector modulation (SVM) to violate grid-code harmonic limits. The application of sinusoidal periodic carrier frequency-SVM (PCF-SVM) fails to resolve this issue, as it merely redistributes spectral energy while increasing low-frequency distortion. To overcome this limitation, a resonant PCF-SVM strategy is proposed, wherein the carrier frequency modulation is synchronized with the fundamental frequency to induce resonant interactions between PCF sidebands and inherent SVM harmonics. When implemented on the machine-side converter, this approach effectively suppresses low-frequency harmonics and shifts spectral energy toward higher-frequency regions, where the grid-side inductance offers stronger attenuation. Simulation results demonstrate that Resonant PCF-SVM reduces the maximum grid-code violation of the generator current from approximately 240% to 93.6% of the limit, significantly enhancing compliance without the need for additional hardware.
Heidari et al. (2026) studied this question.