A Carrier-Based DPWM for T-Type Three-Level Inverter with ZSV Injected by Searching Neutral Point Current

T-type three-level inverters have become the hotpot in the field of photo power generation with the advantages of low voltage harmonics, decreased current distortion and high efficiency, but the imbalance of neutral point voltage (NPV) is a major imperfection. By comparing with the traditional DPWMA strategy, this article proposes a suppressing common-mode voltage discontinuous pulse-width modulation (SCMVDWPM) strategy, which can also achieve the balance of neutral point voltage (NPV). Firstly, the neutral point current model (NPC) is built to figure out the relationship between NPC and zero-sequence voltage (ZSV). Then, an active method based on SCMVDPWM strategy is put forward to control the balance of NPV by injecting the most suitable ZSV. Besides, the self-balance ability of NPV is verified through theoretical calculation and the completeness of the proposed strategy is confirmed. Finally, the simulation results are carried out to prove the effectiveness of the proposed method.