LAUSR

Abstract An optimal strategy is presented to determine the combined control reference for the terminal and circulating currents of a shunt active power filter (APF) based on the delta-connected cascaded H-bridge (CHB) topology, hereby minimizing the operational power under ideal and non-ideal grid voltages, where the ideal grid voltages contain only the positive-sequence fundamental frequency component and the non-ideal grid voltages contain unbalance and/or harmonic components. The optimization is carried out to simultaneously satisfy the desired grid current distortion limits, the source current imbalance characteristics and the power factor as well as power balance requirement. By properly coordinating terminal current control and circulating current injection of the delta-connected CHB and taking possibly unbalanced and/or distorted grids the total power rating of the APF can be kept at minimum, leading to an economical operation. The optimization problem is formulated using a convex quadratic objective function and non-convex quadratic constraints and solved by an iterative procedure. The simulation results show that the proposed strategy is applicable and effective for reactive power and harmonic compensation with an optimal rating of the APF under ideal and non-ideal grid conditions.