Minimum Capacitor Current (MC²) Three-Vector Modulation for Three-Phase Inverter

This article presents a novel modulation for a three-phase inverter designed to achieve minimum dc-link capacitor rms current across the entire power factor (PF) angle and modulation index range. The generalized calculation model for the capacitor rms current is analyzed, followed by a mathematical comparison of all possible three-vector PWM schemes to find the minimum ones. An intuitive time-domain waveform analysis method is also introduced to assess whether the rms current is minimized. A scalar PWM approach using zero sequence injection is implemented, which not only minimizes switching loss but also reduces the complexity of the modulation. Conclusive experimental validation on a 100 kHz silicon carbide prototype confirms that, under unit PF, the proposed modulation technique can reduce capacitor rms current by 43% compared to traditional space vector pulsewidth modulation, and increase efficiency by 0.6% at full modulation index, validating the accuracy of the theoretical calculations and effectiveness of the proposed method.