Dead-band controller for balancing individual dc capacitor voltages in cascade multilevel inverter based STATCOM

This paper presents a dead-band controller for balancing individual dc capacitor voltages in a three-phase cascade multilevel inverter based static synchronous compensator (STATCOM). The design of the feedback control is based on the detailed small-signal model. The proposed dead-band controller can stabilizes the phase shift of H-bridge voltages, and then reduces the risk of unnecessary switching of power semiconductors. The controller can balance individual dc capacitor voltages when H-bridges run with different switching patterns and have parameter variations. Moreover, it is shown that the controller can work well in all operation regions. Experimental results verify the performance of the controller.