Negative-sequence current injection of dispersed generation for islanding detection and unbalanced fault ride-through

Power electronic interface of dispersed generation play a very important role in connecting a dispersed generation itself with utility grid. A power electronic interface not only controls the amount of active and reactive power injecting into a grid but also implements other importance stuffs as well. In this paper, negative-sequence current injection has been fulfilled in power electronic interface for two important duties. The first one is for islanding detection, and the other one is to enhance unbalance-fault ride-through ability of dispersed generation. This paper introduces a mechanism of negative-sequence injection based on controlling two separate coordinates of dq control and explains the effective of negative-sequence injection in limiting the unbalanced currents. Using Adaptive Notch Filter as a signal processing unit, negative-sequence components are observed. Control system performance is evaluated based on time domain simulations in PSCAD/EMTDC environment.