DC‐link capacitor voltage balance strategy of independent double three‐phase common bus five‐level NPC/H‐bridge inverter based on finite control set

Abstract

This study aims at the DC-link capacitor voltage imbalance problem of independent double three-phase common bus five-level neutral point-clamped/H-bridge inverter, which is applied to an electromagnetic launch system under instant highpower and high-current conditions. First, the traditional method of voltage balance strategy based on redundant vectors is described, and the key factors leading to the DC-link capacitor voltage fluctuation is analysed in detail. Second, the objective function is constructed to predict the variation trend of DC-link capacitance voltage difference. Third, an optimised voltage balance strategy is proposed. At first, the optimised strategy calculates the variation trends of the voltage difference for all threephase switch vector combinations. Then, the results make up a voltage balance finite control set. At last, compare the results in the set to select the vector combination corresponding to the minimum variation for output. Finally, tested by the semi-physical real-time simulation platform, and the proposed optimised voltage balance strategy is verified effective for improving DC-link capacitor voltage imbalance and inhibiting the voltage difference fluctuation.

Capacitor Voltage Balancing with Online Controller Performance-Based Tuning for a Switch-Sharing-Based Multilevel Inverter

“…As for DCMI, there are two possible solutions that can be adopted to overcome the unbalanced voltage problem. One solution is via the modification of the pulsewidth modulation (PWM) switching pattern [17][18][19][20][21]. The switching pattern is normally selected from the redundant switching states.…”