Adaptive Over Current Protection of SPV Integrated Distribution Systems

The integration of solar photovoltaic (SPV) system to conventional grid causes various protection challenges in the distribution systems. These challenges arise due to modified network topologies, limited fault current contribution, and bidirectional power flows. The low fault current contribution of inverter-based resources is due to the thermal constraints of converter switches. The reduction in current contribution from inverter-based sources causes the maloperation of conventional over-current relaying schemes in the distribution system. Also, the varying load levels limit the operation of conventional voltage-restrained relays. In this paper, a new methodology is developed to mitigate the issues of existing over-current relays (OCRs). This approach uses local positive sequence current and voltage to modify the pickup current of the relay and makes it adaptive to different loading conditions. In this work, the SPV plant model is operated in voltage control mode where the SPV plant complies with grid codes, i.e., the fault ride-through (FRT) condition. The methodology developed is validated on an IEEE 9-bus system in PSCAD platform. Hardware-in-the-loop testing using Speedgoat real-time simulator as power system and Texas Instruments launchpad as relay validates the performance of the proposed method in real-time.