Using BESS to Help Synchronous Generators Comply with RfG Fault Ride-Through Simulations: A Case Study on Enhancing Transient Stability in the Gas Turbines Located in Barsebäck

Sammanfattning

With the growing integration of renewable energy sources into the power grid, new challenges for system stability have emerged. To address this, the European Union has introduced a regulation called Requirements for Generators (RfG). This regulation sets specific performance standards, one of which is a minimum critical clearing time related to faults. Some production facilities with low inertial constants struggle to comply with this requirement. This thesis investigated how and to what degree a Battery Energy Storage System (BESS) connected to the generator terminal could enhance the transient stability of the gas turbines in Barseb¨ack. To do this, the thesis looked into what system and models should be used. Eventually, a single machine infinite bus (SMIB) system was simulated in DIgSILENT PowerFactory in accordance with RfG. In this simulation, a constant current configured Static Generator model was used to represent the BESS. The BESS was controlled using two constant power factors, during and after the fault. Each power factor defined the corresponding current reference. The most optimal power factors during and post-fault were determined by simulation results, which together provided the best overall control of the BESS. The results showed that for batteries in the 5–95 MVA range, the critical clearing time (CCT) increased up to 57 ms and indicated that the voltage profile could be improved through the use of a BESS. However, if the battery produced high reactive powers post-fault, it would result in voltage oscillations that have to be dealt with. Due to model design decisions, the CCT results are conservative, and it might be possible to increase the CCT even further by utilizing overload capabilities. Overall, this thesis demonstrates that a BESS can moderately enhance transient stability by minimizing acceleration and maximizing deceleration of the rotor. And by this, help meet RfG requirements regarding fault-ride-through simulations.