Control of Regenerative CHB Motor Drives at Fundamental Switching Frequency

To handle the high-power regeneration power in coal and mine industry applications, the regenerative version of the cascaded H-bridge (CHB) drives is made possible by replacing the diode-front-end rectifier with a three-phase IGBT-based active-front-end (AFE) rectifier in each power cell. However, the IGBT switching devices introduce extra switching losses to the system that must be properly handled due to the thermal constraints in high power medium voltage drive applications. In this article, a novel fundamental switching frequency control strategy is proposed for the AFEs in the regenerative CHB drive. With the proposed control strategy, the main harmonic contents generated by the AFEs are well-reshaped at a low-order harmonics range which can be further eliminated by the existing front-end phase-shifting transformer. This allows accomplishing the meeting of the IEEE std 519-2014 at the fundamental switching frequency fsw = 60. Moreover, with the proposed switching pattern, IGBTs can be turned off at zero current and therefore it can reduce switching losses simultaneously. The feasibility of the proposed control strategy is verified by experimental results on a seven-level regenerative CHB drive, which can be extended to regenerative CHB drives with any voltage levels.