Module Power and Loss Balancing through Carrier-reassignment PWM in a 17-level CHB Inverter

Cascaded H-bridge (CHB) multilevel inverters are well-suited for medium-voltage charging stations because of their inherent modularity, scalability, and efficient voltage conversion capability. However, conventional level-shifted PWM (LSPWM) schemes often lead to uneven distribution of active and reactive power among individual modules. This imbalance produces non-uniform semiconductor losses, increases thermal stress, and accelerates premature failures in overstressed modules. Alternative methods, such as space-vector modulation and switching-angle adjustment, can mitigate these issues, but their computational complexity becomes prohibitive for higher-level CHB topologies. Carrier-reassignment PWM strategies, including First-In-First-Out (FIFO), provide simpler implementations but still fail to achieve complete power and loss balancing. This paper contributes to the state of the art in two key ways. First, it extends carrier-reassignment PWM, previously demonstrated only for 9-level CHBs, to a 17-level CHB inverter, introducing two new reassignment strategies: Type-A and Type-B. The Type-A scheme enables highly uniform real-power sharing under a unity power factor. At the same time, the Type-B approach achieves balanced loss distribution across the full power-factor range and effectively eliminates circulating power at zero power factor, surpassing existing rotation-based methods. Second, the paper proposes a comprehensive validation framework that integrates analytical loss modeling of CoolSiCTM devices with hardware-in-the-loop (HIL) experiments, employing an OP4510 digital simulator and a PED-Board controller. Experimental results confirm that the proposed schemes substantially enhance both power and loss distribution, while also reducing current total harmonic distortion (THD) compared to conventional approaches. Overall, the proposed methods provide a practical pathway toward more reliable and efficient CHB converters for electric vehicle charging and medium-voltage applications.