Optimal DC current control for four-wire current source active power filter

This paper proposes an optimal dc-link current control method for a four-wire current source active power filter. The proposed control method utilizes a hybrid energy storage in the dc-link. With the control method the size of the dc-link inductor can be considerably reduced. A small dc-link inductor enables fast dc-link current control according to the instantaneous current requirement and, thus, the average value of the dc-link current can be minimized. The performance and efficiency of the proposed system are studied with experimental tests using a microcontroller controlled four-wire current source active power filter prototype rated for a 5-kVA load. The results are compared to the experimental results of the four-wire current source active power filter with the conventional dc-link structure. The experimental results show that with the proposed control method the efficiency of the four-wire current source active power filter can be considerably improved.