An Improved PWM Strategy for “SiC+Si” Three-Level Active Neutral Point Clamped Converter in High-Power High-Frequency Applications

In this paper, an improved pulse width modulation (PWM) strategy is introduced for three-level active neutral point clamped (ANPC) converters configured by Silicon Carbide (SiC) MOSFETs and Silicon (Si) IGBTs. Compared with the existing PWM strategies in the literature, this improved PWM strategy only interfaces with small commutation loops, therefore the turn-off voltage overshoots caused by the parasitic loop inductance are much lower. Soft switching is achieved across the IGBTs. Also, the conduction loss at zero voltage output is reduced due to the turn-on of two parallel conduction paths for zero voltage output. Furthermore, this proposed PWM strategy can protect the body diodes of the SiC MOSFETs from carrying large load current. To verify all these benefits of the improved PWM strategy, a megawatt (MW) scale three-phase three-level ANPC inverter is developed and implemented, and the experimental results are presented to verify the efficacy and merits of this improved PWM strategy.