Controller-in-the-Loop Validation for Virtual Impedance-based Fault Detection Method in Grid-Connected Inverters

The high penetration of distributed energy resources and grid-connected inverters creates operation and protection challenges in distribution networks which have led to a need for advanced fault protection methods. Therefore, a virtual impedance-based short-circuit fault detection algorithm is proposed in this paper for grid-connected inverters in distribution networks which determines a short-circuit fault through measurement of the spectral change in system impedance at each harmonic frequency. Moreover, a controller-in-the-loop platform is also developed in this paper for verifying the proposed detection algorithm without jeopardizing the operation of distribution networks. By using the developed platform, real-time simulation on both grid-connected inverter and distribution network is carried out. The results have proven the effectiveness of the proposed method and theoretical analysis.