A simple voltage balancing method for modular multilevel converter

The modular multilevel converter (MMC) is one of the most promising converter topologies for medium/high-power applications. One of the technical challenges associated with the control of an MMC is the capacitor voltage balancing among arm capacitors. This paper presents a novel capacitor voltage balancing method combined with the carrier-phase-shifted pulse-width modulation (CPS-PWM) for MMC without measuring the arm current. The proposed method is based on a coordinated control of the pulse distribution and pulse rotation. In this way, the main drawbacks of the existing methods, such as redundancy switching actions, feedback delay, interference with output voltage, and intensive computation can be avoided. Experimental results verify the performance of the proposed capacitor voltage balancing method.