A Study of 1MHz Multi-Sampling SVPWM Method for Low Carrier Three Phase Modular Multilevel Converter

The expansion of renewable energy systems has led to the widespread use of large-capacity converters, and the application of modular multilevel converters (MMC) is expanding. In large-capacity MMCs, the carrier frequency is limited by the switching device characteristics. Therefore, in steady-state response, the characteristics of MMCs output a smooth sinusoidal waveforms, but there is still a problem with the response to load fractuation. In this paper, a new space vector PWM (SVPWM) method that improves the transient response by 1MHz sampling between carriers and compensating the output vector in real time. The output vector is recalculated every 1us by using an FPGA based hardware controller, and the recalculation is immediately reflected to the current vector, which improves the output characteristics of MM Cs with low carrier frequency. The effectiveness of the proposed method is verified.