A voltage balancing controller with fuzzy logic strategy for neutral point clamped multilevel converter

Neutral-point-clamped (NPC) multilevel-converter (MLC) is very popular in high voltage converters with multilevel topology. However, the dc-link capacitor voltage unbalance of this topology is a key issue in the NPC applications, and which will cause distortion and asymmetry of the output voltages, and also increase the voltage stress of power switches. In this paper, the three-level (3L) NPC with unbalance capacitor voltages is analyzed. A capacitor voltage balancing control strategy based on fuzzy logic controller (FLC) for the 3L-NPC-MLC is studied and presented. A fuzzy membership function is ratiocinated and determined, and based of which a capacitor voltage control strategy to suppress the capacitor voltage imbalance is proposed. Finally, simulation results show that both the balancing strategy and the FLC are effective.