Neutral-point potential balancing control of three-level ANPC converters based on zero-sequence voltage injection using PS-PWM

This paper presents a neutral-point potential balancing method for the three-level active neutral-point clamped (3L-ANPC) converter using phase-shifted pulse-width modulation (PS-PWM). With PS-PWM, all the switches are operated at the same constant switching frequency and the even distribution of switching losses can be achieved easily. The relationship between the neutral-point current and zero-sequence voltage is investigated and an optimum zero-sequence voltage can be calculated to regulate the neutral-point potential. Steady and dynamic experimental results are presented to verify the validity of this method.