A collaborative suppression methodology for common-mode noise and neutral-line current in parallel-connected 3L-NPC inverters

Modular multilevel inverter parallel-connected systems have been widely adopted in the electrical industry owing to their configurable power scalability, redundancy-enhanced system reliability, and modular architecture facilitating streamlined manufacturing and maintenance. Nevertheless, high-frequency switching operations of power devices generate substantial voltage transients and current gradients, leading to exacerbated electromagnetic interference (EMI) emissions. To mitigate these interrelated challenges, this study proposes a collaborative suppression for common-mode noise and neutral-line current in three-level neutral-point-clamped (3L-NPC) inverters. A common-mode noise cancellation circuit is innovatively designed, coupled with comprehensive derivation of the inverter's equivalent circuit model incorporating parasitic parameters. The simulation results show that the method proposed in this paper achieves the common suppression of the common-mode noise on both the AC and DC sides of the inverter and reduces the neutral-line current.