Comparative Study of High-frequency Injection Method and HMMC for Suppressing Capacitor Voltage Fluctuation of MMC

摘要

Modular multilevel converter (MMC) represents an interesting and emerging topology in medium-voltage motor drive applications. The main challenge of using such a topology in variable-speed drives is the large voltage fluctuation of submodule capacitors at low speeds. The most widely used method of suppressing the fluctuation of capacitor voltage is high-frequency injection method. In addition, a novel hybrid modular multilevel converter (HMMC) topology has received extensive attention due to its inherent ability to reduce capacitor voltage fluctuation. In this paper, a comparative study of high-frequency injection method and HMMC in terms of converter loss, current stress and capacitance was conducted. The results show that the use of HMMC topology leads to lower loss and current stress at low frequency. The comparative study will guide the application of MMC in the field of motor drive.