Four-Wire Active Power Filter Based on Asymmetric Cascaded H-Bridges

This article studies a four-wire active power filter composed of three H-bridges, a four-wire three-phase converter, and four dc-links. The first three dc-links with the same voltage values, and the other assumes twice or half voltage. These asymmetrical conditions (dc-link voltage ratio 1:2 and 2:1) and adding a fourth interface inductor are investigated. These aspects affect the minimum dc-link voltage required, quality of waveforms, and compensation capacity. A new control strategy of the dc-links voltages that reduces its voltage ripple is presented in this article. The circuit model, level-shifted PWM strategy, simulation and experimental results, and comparisons in terms of efficiency, ratings of power switches and quality of waveforms are also addressed.