Opportunities for power quality improvement through DG-grid interfacing converters

Power electronics technology is becoming an increasingly important aspect of today's power distribution system. It is the key interface to connect distributed energy resource (DER) to the utility and the local loads. With the increased penetration of power electronics based distributed generation (DG) systems, the power quality requirements are becoming more stringent. On the other hand, if controlled and regulated properly, the DG-grid interfacing converters are able to improve the system efficiency and power quality, in addition to the primary function of real power injection. This paper discusses the opportunities for power quality improvement through the DG-grid interfacing converters. While the harmonic voltage compensation is the focus of this paper, a number of other ancillary functions, such as unbalance voltage compensation, voltage sag mitigation and reactive power compensation, can be realized in a similar manner. Two alternative DG control methods, namely current controlled DG and voltage controlled DG, are considered and the associated power quality compensation strategies are developed. Simulation results and experimental results from a three-phase 5kVA laboratory DG prototype are provided.