Three-phase unbalanced-voltage compensators

In this paper, three-phase unbalanced-voltage compensators using ac choppers are proposed. The proposed three-phase unbalanced-voltage compensators are made up of three single-phase ac choppers and transformers for unbalanced-voltage compensation and output voltage regulation. The proposed compensators use ac choppers which solve the commutation problem, limit the switch voltage stress to the maximum line voltage, and also raise efficiency using regenerative de snubbers. Compared with previous unbalanced-voltage compensators that use complex voltage source inverters, the proposed unbalanced-voltage compensators use ac choppers and utilize source or output line voltages in 30 degrees phase shift with the phase voltages as the input of the ac chopper. Then, the proposed compensators give high efficiency, fast dynamics, simple power circuit, and reduced control circuit. It is also shown via some simulation and experimental results that the presented unbalanced-voltage compensators give good dynamic and steady state performances.X11sciescopu