Multi-objective optimization control of a four-level hybrid-clamped inverter

Four-level hybrid-clamped (4L-HC) inverter is a newly proposed topology which is suitable for high-performance medium-voltage drives. This paper proposes a multi-objective optimization strategy for this 4L-HC inverter. The central DC-link capacitor and flying capacitor voltages are regulated by a modified phase-shifted PWM. The upper and lower capacitor voltages are balanced by zero-sequence voltage injection. The relationship of zero-sequence voltage and common-mode voltage is also investigated. By properly limiting the injected zero-sequence voltage, the peak value of common-mode voltage can be suppressed to less than 30% of the DC-link voltage. Simulation results are presented and a low power experimental prototype is built to verify the validity of this method.