Reference current estimation for three-phase delta-connected active power filter

In the process of compensation current reference estimation for three-phase delta-connected active power filter (APF), fast dynamic response and high accuracy are required. Zero average active power in each phase must be obtained under asymmetric compensation currents because of the split dc-link capacitors of the H-bridge converters. In view of these problems, the transformation relation between the compensation current references and load currents is derived based on the theory of reactive compensation admittances network. Using this transformation, delta-connected APF can be decoupled into three single-phase systems. Accordingly, an integrated current extraction strategy can be achieved under imbalanced and/or distorted conditions. Results obtained verify the fast dynamic response and accuracy of this approach.