In this paper, a novel principle of a power quality conditioner based on controllable impedance is proposed for high voltage ac power distribution systems application. A linear transformer is employed to act as controllable impedance under the control of power electronic inverter. On the one hand, the transformer can always exhibit nearly zero impedance to harmonic current. Thus, the harmonic current in ac power systems can be led to flow into the transformer branch. On the other hand, the transformer can also exhibit continuously adjustable reactance to fundamental current and form a novel static Var compensator (SVC) together with passive power filters. Thus, the performance of ac power systems can be improved by compensating reactive power. The operation principle, the control scheme, and the reference current operation method are discussed in detail. Finally, experimental results are presented to verify the effectiveness of the novel power quality conditioner.
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