Assuring Security and Stability of a Remote/Islanded Large Electric Power System With High Penetration of Variable Renewable Energy Resources

The Ejina electric power system, located in the remote western reaches of Inner Mongolia, China, features high penetration of variable renewable energies, and relies on a single-circuit, 442 km radial 220 kV overhead line for connection to the main grid. This configuration poses stability challenges in grid-connected mode due to low system strength, and a high risk of blackout under the islanded operation mode due to the lack of an internal voltage source to establish the voltage and frequency for the entire region. To tackle these challenges, a 25MW/25MWh grid-forming battery energy storage system (GFM-BESS), together with the advanced energy management system (EMS) and high-speed stability control system are installed in the Ejina electric power system. The voltage source feature of the GFM-BESS guarantees the stability of Ejina electric power system in both grid-connected and islanded operation modes, as well as fulfilling N-1 security criteria. The outcomes of this real-world project demonstrate the feasibility of utilizing the GFM-BESS to stabilize the wide-area, remote/islanded electric power system with extremely high penetration (or even 100% penetration) of variable renewable energies. This paper intends to perform a detailed elaboration of this pioneering project, including system and functionality descriptions, as well as real-field testing results under various operating scenarios, which hopefully can shed a light on the extended application of GFM technology in the future bulk power system with high penetration of variable renewable energies.