Design of cascaded H-bridge rectifier for medium voltage applications

In this paper a new control method for voltage balancing of distinct do buses in cascaded H-bridge rectifier has been proposed. The voltage balancing will be guaranteed even if the load values aren't equal. This structure with the proposed control method is applicable for arbitrary number of series H-bridges, different voltage levels, and different power levels. For reducing current harmonics and distortion, the input current is programmed to be in sinusoidal form and in phase with the input voltage. Besides, it is possible to change the phase angle between input current and input voltage to transfer active or reactive power between load and mains. To confirm the new control method, a 7-levels prototype of cascaded H-bridge rectifier has been made and the results have been shown.