Direct AC/AC voltage regulator using a 2-level modulated cascaded H-bridge converter

Voltage compensation for the utility grid can be realized by using tap changers or hybrid transformers. This paper proposes a generalized voltage regulator based on cascaded H-bridges that can be scaled to applications with various voltage ratings. A 2-level modulation scheme is implemented: the series- connected submodules are switched on and off simultaneously, and the converter behaves similarly to a half-bridge circuit. The submodule capacitors have nearly zero energy variations: they are mostly bypassed or block the ac source voltage. As a result, the proposed operation method requires much lower submodule capacitance compared to modular multilevel converters. During the dead time, the submodule capacitors can be charged from the grid. A control method is proposed for balancing the voltages, and is verified in a simulation model.