Series active power filter compensates current harmonics and voltage unbalance simultaneously

An active power filter connected in series to the power distribution system is presented and analysed, The series active power filter is implemented w ith a three-phase PWM voltage-source inverter and operates with a resonant LC passive filter connected in parallel to the power lines. The proposed sc heme is able to simultaneously compensate current harmonics, the fundamenta l negative and zero sequence voltage components generated by the voltage so urce unbalance, and also eliminates the zero sequence current harmonic comp onents that circulate through the neutral conductor. The active power filte r is discussed in terms of the principles of operation under steady-state a nd transient conditions. The design and implementation of the power and con trol circuits are reported. Key predicted results are verified experimental ly on a 5kVA prototype model.