Voltage Balancing of a Modular Neutral-Point-Clamped Converter With a Carrier-Based Modulation Scheme

The five-level modular neutral-point-clamped (5L-MNPC) converter is realized by connecting two three-level neutral-point-clamped modules in series. For five-level operation, each dc-bus capacitor voltage of the modular neutral-point-clamped topology should be regulated at one-fourth of the net dc-bus voltage. In this letter, a simple voltage-balancing approach based on the carrier-based modulation scheme is proposed to achieve the above objectives. The proposed approach uses the redundancy switching states along with the current direction and the instantaneous value of the dc-bus capacitor voltage to achieve the voltage balancing in the 5L-MNPC topology. The dynamic performance of the 5L-MNPC topology with the proposed voltage-balancing approach is verified experimentally.