Carrier-based PWM design of multilevel ANPC-based converter through hierarchical decomposition

Traditional PWM design of multilevel active-neutral-point-clamped (ANPC) based converter is complex and lack of scalability especially when the voltage level increases. This is particularly true when considering loss distribution, waveform quality and control modularity in the PWM process. This paper firstly proposes a general PWM design approach for multilevel ANPC-based converter through hierarchical decomposition. Modified from decomposition theory, the hierarchical decomposition is introduced in this work to facilitate identification of different operation patterns for an arbitrary ANPC-based topology. Based on the proposed approach, simplified PWM schemes for various patterns are designed modularly through carrier-based methods (i.e. level-shift and phase-shift PWM). Experiments of ANPC-based topologies show the universality of the proposed method.