Common-Mode Voltage Reduction for MMC With Consideration of Dead Zone and Switching Delay

Modular multilevel converters (MMCs) are widely used due to their superior performance. However, the rapid switching of power electronic devices will bring serious electromagnetic interference (EMI) into the system. Common-mode voltage (CMV) is the major EMI problem and affects the normal operation of electrical components, reducing system stability and safety. By using the zero common-mode voltage (ZCMV) modulation strategy, the CMV caused by modulation can be eliminated theoretically. However, due to the dead zone of the switch and the switching delay between the control signal and the final output voltage, there are still spikes in the CMV of the ZCMV modulation. This article has done an analysis of the dead zone and switching delay in MMC and their impact on CMV. Then, a new ZCMV modulation strategy based on the bridge arm current prediction is proposed in this article. The dead zone and delay of the switch are considered for compensating control. By achieving power pulse alignment to further reduce CMV, the experimental results show that ZCMV with dead zone compensation and delay compensation (ZCMV-CC) can eliminate spikes in the spectrum and reduce CM EMI obviously.