New Modulation Scheme for Three-Level Active Neutral-Point-Clamped Converter With Loss and Stress Reduction

This paper proposes a new modulation scheme for the three-level active neutral-point-clamped (ANPC) converter. This scheme yields new commutation loops for the three-level ANPC phase leg, which contain paralleled switching devices during commutation. The new commutation loops have better switching performance with smaller switching stress for some devices. There are also more evenly distributed loss and stress for each switching device on the phase leg. Moreover, the switching states of the new modulation scheme also reduce the conduction loss of the neutral current. In addition, the proposed modulation scheme needs less pulsewidth modulation (PWM) comparators per phase compared with the conventional scheme. The simple gate signal logic can be applied to any sinusoidal PWM or space vector modulation strategies. Double pulse tests for the new commutation loops show the improved switching characteristics under different load current cases. In addition, the quantitative analysis of the system loss breakdown and the phase leg loss distribution verifies the loss reduction and redistribution result. The proposed method is also applied on a 200-kW three-level ANPC converter for verification.