A Neutral-Point Voltage Balancing Algorithm for Six-phase H-Bridge Neutral-Point-Clamped Converter

Multiphase inverter are widely used in ship propulsion, because of it has good fault tolerance, high control freedom and high power output under low voltage. In order to use low voltage level semiconductor, the inverter adopting a multi-level topology. The neutral-point(NP) voltage balance is most important of this inverter. This article presents a novel modulation strategy with carrier-based PWM to keep neutral-point(NP) voltage balance for a six-phase H-bridge neutral-point-clamped (NPC) converter. The converter is used to drive a six-phase open winding PMSM. First, the basic modulation method was determined, then, analyzed the topology. Fine-tuning the duty cycle through proportional regulator in switching period, the deviation between the bus capacitors was reduced. The simulation results show that the proposed modulation strategy can effectively balance the NP voltage, and it has been verified in experiments.