A new method to implement resampled uniform PWM suitable for distributed control of modular multilevel converters

Two existing methods to implement resampling modulation technique for modular multilevel converter (MMC) (the sampling frequency is a multiple of the carrier frequency) are: the software solution (using a microcontroller) and the hardware solution (using FPGA). The former has a certain level of inaccuracy in terms of switching instant, while the latter is inflexible with higher cost. In order to overcome these drawbacks, this paper proposes an alternative solution, which uses high frequency saw-tooth carrier and two independent comparators, usually available in microcontrollers, to create the proper switching instances needed for the resampling modulation technique. The software implementation of the proposed phase shifted PWM (PS-PWM) method, and its application in a distributed control system for MMC, are fully discussed in this paper. Simulation and experiment results show that the proposed solution can realize the resampled uniform PWM and provide high effective sampling frequency and low time delay, which is critical for the distributed control of MMC.