Active zero-sequence voltage injection modulation strategy for capacitor current suppression in dual sector PMSM systems

This article proposes an active zero-sequence voltage injection space vector pulsewidth modulation strategy (AZSV-SVPWM) to suppress capacitor current in the common DC-link capacitor of a dual three-phase inverter. Suppressing capacitor current is crucial to improve the power density and reliability of traction inverters, especially in a dual sector three-phase permanent magnet synchronous motor (PMSM) system, since this necessitates multiple sets of capacitors when arranged as multiple conventional three-phase inverters. The impact of the DC offset of zero-sequence voltage on output voltage and capacitor current is quantified based on double Fourier analysis and experimental verification. According to a frequency domain model for the common DC-link capacitor current, it can be concluded that an appropriate combination of the zero-sequence voltages of two sets of inverters can suppress the capacitor current. The AZSV-SVPWM is proposed and implemented by adjusting the distribution of two zero-vectors among the space vectors. With the application of the proposed method, the capacitor current RMS can be suppressed by up to 74.46%.