Three-phase unbalanced-voltage compensators

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