Inverter-Based Resource Plants Operation in Combined Transmission-Distribution Weak Grids: A Case Study

This study investigates the operation of inverter-based resource (IBR) plants in a bulk power system, under different grid-strength conditions and for various penetration levels of static and dynamic loads. For this purpose, Monte-Carlo EMT simulations have been performed on a combined transmission-distribution network in PSCAD/EMTDC software. The four active distribution feeders are connected at different locations of the bulk power system. Each active distribution feeder comprises three-phase static and induction motor loads, single-phase and three-phase average-model distributed energy resources. The results show that operating the IBR plants in weak transmission-distribution networks leads to short-term voltage instability. But by increasing the induction motor loads share of the active distribution feeders total gross load, this IBR-driven instability phenomenon has been mitigated. As a result, this can improve weak transmission-distribution network operations that accommodate a high share of grid-following IBR plants.