DC-link capacitor voltage balancing technique for phase-shifted PWM-based seven-switch five-level ANPC inverter
The Five-Level Active-Neutral-Point-Clamped (5L-ANPC) inverters are receiving more attentions as one of preferred solutions for medium and high power applications because of the combination of the features of the conventional Flying-Capacitor (FC) type and Neutral-Point-Clamped (NPC) type inverters. This paper proposes a new DC-link capacitor voltages balancing technique for the Seven-Switch 5L-ANPC (7S-5L-ANPC) topology which is using Phase-Shifted PWM (PS-PWM) modulation method. Based on the power relationship between DC-link capacitors and FC, the proposed technique adjusts the duty cycles of redundant 1-level switching states to balance the DC voltage without changing the output performance. The proposed technique can be applied to any 5L-ANPC inverter topologies. A 1 kW single-phase 7S-5L-ANPC inverter experimental prototype is built to verify the effectiveness of the proposed DC-link capacitor voltages balancing technique.