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

Abstract

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 NPC 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 (LUT). 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.