A simple method for common-mode voltage optimization in three-level three-phase four-leg inverters

Abstract

In response to the problem of large common-mode (CM) voltage magnitude and high-frequency variation under traditional modulation strategies for three-level three-phase four-leg (3L3P4L) inverters, this paper proposes a modulation strategy based on carrier combination and modulation wave splitting. Firstly, this paper establishes a CM model for the 3L3P4L inverter and derives mathematical expressions of the system’s CM voltage in terms of switch states and system parameters. Building upon this foundation, this paper explains the reasons for high-frequency variations in CM voltage under traditional schemes and provides a detailed introduction to the optimization process and principles of the proposed strategy. Finally, a simulation model is developed by using Matlab/Simulink software. Through comparison with traditional approaches, the effectiveness of the proposed strategy is validated.