A Novel Five-Level Carrier Phase Disposition Modulation Method for Parallel Three-Level Inverters Considering Circulating Current Suppression

Parallel operation of three-level inverters is an effective approach to achieve larger motor drive power. The interleaved operation can improve current distortion, but high-frequency circulating current inevitably emerges, reducing the power capacity and reliability of the system. To suppress circulating current, this paper proposes a five-level carrier phase disposition modulation method for parallel three-level inverters. Based on the carrier phase disposition modulation, the parallel three-level system can operate as a five-level inverter, and the pulse distribution is realized through the system state machine, which avoids complicated mathematical calculation. The simulation results verify that, compared with the interleaved operation, the proposed scheme has superior performance in term of circulating current suppression without increasing the output current harmonic.