Adaptive and Optimal Protection System Framework for Inverter-based Distribution Networks

Integration of inverter-based resources (IBRs) into the distribution grid is expected to grow substantially more in the coming years. The fault response of an IBR differs vastly from traditional distributed generation (DG) such as synchronous generators. With increased penetration of IBRs in the distribution network, fault currents become bidirectional, and combined with the nonlinear fault response, traditional protection systems face challenges and are more at risk of misoperations. Two approaches which seek to improve the protection schemes under increased IBR penetration include optimal protection coordination (OPC) and adaptive protection. Optimal protection coordination seeks to coordinate relay settings through solving an optimization problem. Adaptive protection changes relay settings based on the prevailing network conditions. Some research has shown the schemes combined to create adaptive and optimal protection systems (AOPS), however the literature is limited and has only been applied to certain types of systems. In this work, a framework for a rolling window AOPS is developed for distribution networks with PV inverters. In addition to the rolling-window AOPS framework applied to PV inverters, three other main novel contributions are added. First, a grid-following PV inverter with nonlinear fault response is modeled and studied under the protection system. Next, improvement is made to the OPC formulation by including the short-time settings as optimization variables. Lastly, a case study on very-short-term load forecasting (VSTLF) is presented, to show the capability of load forecasting to be used as a prediction layer within the AOPS.