A simple current-balancing method for a three-phase 5-level current-source inverter

Whether the intermediate inductor current can be kept balanced or not is vital to the output performance of multilevel current-source inverters (CSI´s). This paper begins by introducing the operational principle of a three-phase 5-level CSI topology. In such a 5-level CSI system, control of the 1/2-level intermediate DC-link current is identified as a key problem. In order to keep the intermediate DC-link current well balanced, the mechanism of current balancing is analyzed in detail. By identifying the value of the inductor current and the positive-negative polarity of the voltage across the intermediate inductor, a simple implementation method for current balancing control is proposed on the basis of the carrier phase-shifted SPWM technique in this paper. Simulation and experimental prototypes have been built to verify this 5-level CSI system with the proposed current balancing control method.