Virtual Space Vector Overmodulation Strategy for NPC Three-Level Inverters With Common-Mode Voltage Suppression

To improve the utilization of the dc-bus voltage and solve the problem of neutral-point voltage (NP-V) unbalance and high common-mode voltage (CMV) in the overmodulation region of three-level neutral-point clamped inverters, a virtual space vector overmodulation (VSV-OVM) strategy considering NP-V balance and CMV suppression is proposed. Based on the hybrid vector correction method, the utilization of dc-bus voltage in the overmodulation region is improved, the computational burden of overmodulation algorithm is alleviated by means of fitting and establishing lookup table. Meanwhile, an effective active NP-V control method with switch states Misalignment protection is designed for the proposed VSV-OVM strategy. Furthermore, the implementation details of the proposed VSV-OVM strategy is elaborated. The experimental results verify that the proposed VSV-OVM has excellent NP-V balance and CMV suppression ability in the overmodulation region, and has higher dc-bus voltage utilization.