四电平非对称飞跨电容逆变器的混合PWM技术和电容电压平衡控制

This paper proposes a novel hybrid PWM technique for the four-level (4L) asymmetrical hybrid flying capacitor (AHFC) inverter, a variant of the HFC topology. This technique combines level-shifted and phase-shifted PWM methods to achieve natural voltage balancing for flying capacitors under ideal and steady-state operating conditions. To maintain balanced DC-link capacitor voltages, a control strategy based on zero-sequence-voltage injection is developed. Moreover, a comprehensive analysis of the 4L-AHFC inverter is performed, comparing it to other 4L inverter topologies in terms of component count, cost, total harmonic distortion (THD), and power losses. A 2-kV/1-MVA 4L-AHFC inverter system offers a 10% lower in total standing voltage (TSV) and a 20% cost reduction compared to the conventional HFC circuit. Furthermore, the 4L-AHFC inverter with the proposed PWM method exhibits lower THD at medium-to-high modulation indices and reduced power losses compared to the HFC inverter. Finally, the effectiveness of the proposed PWM scheme and capacitor voltage balancing control has been validated through experimental results for a 3-kVA hardware prototype.