Protection collaborative fault control for power electronic-based power plants during unbalanced grid faults

The controlled fault characteristics of power electronic-based power plant during unbalanced grid faults can heavily affect the proper operation of distance relay. In order to solve this issue, a fault control scheme is developed for the power electronic-based power plant, which is compliant with grid protection during unbalanced grid faults. Firstly, we analyze the essential problem of the distance relay on the transmission line connecting the power electronic-based power plant. Subsequently, we build the equivalent fault models of power electronic-based power plant in the sequence systems based on the reactive power supporting requirements defined in the modern fault-ride-through rules and the protection demands. From the analytic equation of apparent impedance in different fault loops, a novel protection collaborative fault control scheme to determine the proper current command angle of the power electronic-based power plant during unbalanced grid faults is deduced. Simulation results prove that the proposed fault control of power electronic-based power plant can improve the accuracy of reactance measurements in distance relay, which in turn reduces the malfunction risk of the relay.