Input Current Source-Based Modular Multilevel Converter for Wound Field Synchronous Machine Drive With Improved Low-Speed Operation

This article proposes a new configuration of modular multilevel converter (MMC)-based wound field synchronous machine drive for high power applications. In this configuration, the MMC incorporates the field winding and delivers power to the three-phase stator windings of the synchronous machine. There is no need for a separate dc power supply for the field winding of the synchronous machine. The proposed control strategy of this drive ensures that the peak-peak ripple voltage of the submodule capacitor does not depend on the operating frequency of the drive. Thus, the problem of high peak-peak ripple voltage of the submodule capacitor at a low frequency of the drive is solved without overloading the machine and the MMC. The article analyses the operation of the drive and proposes a suitable control strategy for this drive. The operation of this drive has been verified using simulation in MATLAB/Simulink platform and a scaled-down proto-model developed in the laboratory.