High-speed algorithm for renewable energy based microgrid fault detection and protective coordination

The microgrid concept was proposed as a way to facilitate the integration of distributed renewable energy resources. However, due to the use of distributed energy resources (DERs) microgrids face new protection challenges that need resolved. One of those challenges is that traditional protection methods, such as overcurrent protection, cannot be used mainly because of low fault currents, bi-directionality of power flow, and IEEE 1547 voltage ride-through requirements at the point of common coupling (PCC). Therefore, fault current and voltage magnitudes cannot be used as the protective indicators as they may cause breaker misoperation or longer trip times resulting in longer times to clear a fault. Additionally, knowledge of the fault location is a necessary element to properly protect the microgrid and avoid blinding or nuisance tripping. Change in the phase difference between voltage and current is an affective indicator that manifests on a short circuit in an islanded microgrid with inverter-based DERs. This paper explores the use of such an indicator and uses it as a foundation to propose a novel high-speed fault detection and fault direction detection method. A protective coordination algorithm is also proposed. The performance of the proposed solution is demonstrated in the PSCAD/EMTDC simulation environment.