A Modulation Scheme to Suppress Common-Mode Voltage of Four-Level Dual Inverter

The dual-inverter system can achieve multilevel operation with only two two-level converters. It can generate up to five levels with appropriate DC-link voltage configurations. Yet, the dual inverter system suffers from the common-mode voltage issue which generates zero-sequence currents and thereby deteriorates the load performance. To address this issue, this paper proposes a novel modulation scheme to suppress the common-mode voltage for the dual inverter. The four-level configuration is taken as an example since it performs better than the three-level and is simpler than the five-level. Firstly, the operation principle of the dual-inverter system is introduced, and the mathematical model is established. Secondly, the space vector modulation method based on line voltage vector is presented, and the modulation area is classified, so that the number of line voltage levels output by the dual-inverter system changes with the size of the load. Thirdly, by analyzing the expression of common-mode voltage, a method for suppressing common-mode voltage of the four-level dual inverters is proposed. Finally, the simulation results in Matlab/Simulink are provided to verify the effectiveness of the proposed method.