Eight-switch converter for power quality conditioning

Aiming a cost reduction, this paper presents an eight-switch power conditioner for current harmonic compensation and voltage sag mitigation derived from the nine-switch converter. The nine-switch converter has some restrictions in the total attainable amplitude at its outputs, depending on the phase shift between its two terminal sets. However, with an appropriately designed control scheme, the nine-switch converter is shown to favorably raise the overall power quality, justifying its role as a power conditioner at a reduced semiconductor cost. The proposed power conditioner presents a transformerless hybrid filter based on a four-switch two-leg inverter and a six-switch dynamic voltage restorer. The conditioner has good harmonic compensation capability and voltage sag mitigation with the advantage of having a reduced number of switches, respect to a conventional back-to-back converter (eight, instead of twelve). Experimental results for the conditioner prototype demonstrate the effectiveness of the proposed topology.