An analogous carrier‐based implementation of virtual space vector modulation with low common‐mode voltage and neutral‐point voltage oscillation elimination for three‐level NPC inverter

Abstract

Abstract Balancing control of neutral‐point voltage (NPV) and reducing common‐mode voltage (CMV) are crucial for a three‐level neutral‐point‐clamped (NPC) inverter. NPV oscillation can be inhibited by constructing virtual vectors and adding adjustment factors to eliminate stochastic disturbances that cause unbalanced NPV. However, the adjustment factors significantly increase computational complexity and introduce a dynamic sector split instead of the traditional static one. Moreover, constructing virtual vectors prompts a considerable rise in CMV. Therefore, this paper proposes a virtual space vector modulation strategy for the NPC inverter that eliminates NPV oscillation and reduces CMV. The study applies the idea of carrier‐based modulation (CBM), which reduces calculation time caused by the novel strategy of adding adjustment factors. A method to determine the maximum adjustment voltage is designed to evaluate NPV regulation ability, which is analysed. The novel method and the basic VSVM are theoretically compared, and it is proved that the novel method has better NPV regulation capability than the basic VSVM under high modulation ratio and high power factors, such as in motors systems.

Keywords

• AC motor drives
• DC‐AC power convertors
• electromagnetic compatibility
• PWM invertors