A novel six-phase inverter system for high-power synchronous motor drives

Load commutated inverters with multiple three-phase configurations are widely used in high-power synchronous motor drives due to its robustness and reliability. However, harmonic problems, poor starting performance and the limited upper frequency are the issues to be addressed. In this paper, a novel six-phase inverter system, consisting of two main three-phase inverters and an additional five-level reinjection circuit, is proposed. The reinjection circuit which generates five current steps is introduced in this study. To note, the lowest current level is zero to ensure the zero current switching of the main inverters. Therefore, the starting performance and torque quality of the synchronous motor are greatly improved. Moreover, the limit of upper frequency is raised since the mutual interaction between stator windings is eliminated during commutation.