Split-Capacitor Self-Voltage Balancing Capability of Active-Damping Three-Phase Four-Wire Three-Level Inverters

Three-phase four-wire three-level (3P4W3L) inverters are widely employed in distribution networks. For their safe and stable operation, both the active-damping control strategy and the balance of the split-capacitor voltage are essential. However, existing studies have neglected the impact of active-damping strategies on split-capacitor voltage dynamics and the coupling between them. To address this issue, this paper first analyzes the self-voltage balancing capability of split capacitors under open-loop operation. Subsequently, the effects of different active-damping control strategies on this capability are investigated. The analysis reveals that the primary cause of the loss of self-voltage balancing is the positive-feedback characteristic of the split-capacitor voltage introduced by the active-damping control. Finally, experimental results are provided to validate the theoretical findings.