A Case Study on Self Healing of Smart Grid with Islanding and Inverter Volt-VAR function

Development and integration efforts for smooth transition to a Renewable Energy (RE) rich green smart grid have drawn attention worldwide. Utilization of Volt-VAR functions of inverters to mitigate voltage violations have been introduced in recent grid integration standards in India. All the new grid connected non-synchronous generators are expected to provide a composite power delivery at continuous rated output power as well as they should participate in dynamic reactive power injection while maintaining the power factor within an acceptable range. The present case study is based on a voltage instability incident which has always been observed as one of the most censorious problems in complex power system network with many grid occurrences of complete black out of the system due to voltage collapse. The Kerala power system network has been simulated using real-time power grid data collected from PMUs/SCADA system for all 400kV and 220kV nodes in Kerala grid. The paper illustrates a self healing mechanism through islanding using generator coherency identification. An approach for employing Volt-VAR functionality of inverter based grid connected renewable resources, especially photovoltaic system to address the voltage instability issue that occurred during an actual abnormal condition in the conventional grid, is elaborated. The proposed method calls for a centralized control scheme as decentralized operation of inverter response functions have been studied to trigger potentially undesirable interactions. Real time contingency conditions that occurred in Kerala grid are simulated and practical solution for self healing is proposed incorporating the VAR support provided by the solar inverters.