Three phase active filter topology based on a reduced switch count voltage source inverter

Active filters are being proposed as an effective solution to reducing harmonic pollution. However, cost and efficiency are some of the main drawbacks. This paper proposes a low cost three-phase active filter based on a PWM voltage structure with a reduced number of switches. Operation, cost, rating and practical issues are considered and compared with the conventional six switch PWM-VSI. The paper also investigates the unbalance in the voltages of the two capacitors and discusses a new control scheme to eliminate the voltage difference. The analytical results are verified through simulation. Results show that good harmonic attenuation of line harmonic current can be obtained with the proposed filter