Multiphase Parallel Winding Current Source Inverter With High Maximum Modulation Index

Current source inverter (CSI) has received more and more attention in recent years because it is suitable for driving low inductance machine and has better reliability. It's universally acknowledged that the maximum modulation index is one of the most important factors to evaluate the performance of CSI. A higher maximum modulation index represents that the output current can be higher under a constant DC-link current. Nevertheless, the maximum modulation index of traditional CSI with star-connected winding will decrease gradually with the increase of phase number, which is analyzed by phasor method in this paper. Three-phase parallel winding current source inverter (PWCSI) has direct carrier-based pulse width modulation (CBPWM) and excellent fault-tolerant performance. In order to improve the maximum modulation index, this paper proposes the multiphase PWCSI. By using phasor method, the optimized winding connection sequence (WCS) of multiphase PWCSI can be analyzed. Under the proposed optimized WCS, the maximum modulation index of multiphase PWCSI is almost as high as 1, which is much higher than the one of CSI with star-connected winding. Experimental results are presented to compare the maximum modulation index between CSI with star-connected winding and PWCSI.