An Improved DPWM Method for Single-Phase Five-Level ANPC Converters With Switching Loss Reduction and Capacitor Voltage Balance

Neutral-point (NP) voltage and flying capacitor (FC) voltage balance, and power loss reduction are important guarantees for the stable and high-efficiency operation of single-phase five-level active neutral-point clamped (5L-ANPC) converters. However, little reports about capacitor voltage balancing with the power loss reduction have been proposed for single-phase 5L-ANPC converters. In order to obtain the above merits, an improved discontinuous pulsewidth modulation (DPWM) method with capacitor voltage balance and power loss reduction is proposed. First, an optimized common-mode voltage is injected into the modulation waves to decrease the switching loss in each switching period. In particular, the calculation of the injected common-mode voltage is based on the analysis of the deviation of the NP voltage. Hence, a fast-dynamic response of the real-time NP voltage controlling is acquired in the meantime. Besides, in order to balance the FC voltage, the weight factors of NP voltage deviation and FC voltage deviation are compared to generate the selecting signals of redundant switching states. As a result, the capacitor voltage balance and power loss reduction are realized simultaneously. Finally, the simulation and experimental results validate the correctness and feasibility of the proposed DPWM method.