Design and implementation of a new three-phase four-wire active power filter with minimum components

This paper reports the development of a new three-phase four-wire active power filter which has no passive elements and only has four bidirectional switches. A new switching technique based on three dimensional vector treatment of unbalanced three phase circuits is used for the control of the APF. Experimental results from a prototype APF confirm the suitability of the proposed approach not only for the removal of harmonics, but also for the compensation of fundamental unbalance currents and reactive power consumed by the load. The experimental results show that current total harmonic distortion (THD) in each phase is reduced from 58% to less than 5% which is acceptable by most harmonics standards. The neutral current, including fundamental and harmonics, is reduced by a factor of 15.