Current reference strategy with explicit negative sequence component for voltage equalization contribution during asymmetric fault ride through

Abstract

SUMMARY The unbalanced voltage condition represents by far the most typical scenario of distribution power generation systems during faults. In fact, the different current reference generation strategies designed to meet the reactive power requirements of the grid codes during faults are influenced by this fault's characteristics. Nevertheless, in the current references strategies found in literature, there are still issues to be addressed, like clarifying the effect of reactive current injected in the negative sequence, how to best inject reactive power to help equalize the phase voltages while supporting the average grid voltage and how much negative sequence reactive current can or should be injected. This work presents a current reference strategy to achieve, or to contribute to, the equalization of the phase voltages at the point of common coupling through the injection of the reactive power with a proportion between the positive and negative sequence reactive currents determined by the fault characteristics. This strategy is derived from the idealized response of a synchronous machine to asymmetric faults. Simulation and experimental results obtained with the proposed method and others described in literature are presented and compared to provide insight into the advantages and limitations of the negative sequence reactive current injection. Copyright © 2014 John Wiley & Sons, Ltd.