System Level-Based Voltage-Sag Mitigation Using Distributed Energy Resources

As the growing demand for battery energy storage systems (BESSs) generally follows the renewable energy sources (RESs) trend, the active management of BESS- and RES-based distributed energy resources (DERs) could effectively solve voltage-sag problems in active distribution systems (ADSs). DERs are typically interfaced with the grid through power-electronic inverters. They are considered power resources with adjustable active/reactive power injections that could contribute to the enhancement of the grid's performance. This article proposes a new framework for active/reactive power management of inverter-based DERs to mitigate voltage-sag problems in ADSs. The new framework utilizes a novel zonal-based voltage control algorithm for mitigating voltage-sag problems in ADSs. The algorithm identifies mitigation zones' virtual boundaries based on a proposed electrical influence intensity index that reflects the electrical connectivity of the network. A novel zone capability index (ZCI) ranks the mitigation zones according to DER capacity, zonal loading conditions, and the number of nodes within each mitigation zone. The voltage mitigation algorithm minimizes the energy injected from DERs’ inverters to achieve maximum voltage sag alleviation in each mitigation zone. This zonal-based mitigation algorithm is applied to the IEEE 33-bus distribution system under voltage-sag conditions to verify the proposed algorithm's feasibility and effectiveness.