Enhancing Frequency Response Characteristics of Low Inertia Power Systems Using Battery Energy Storage

This paper investigates the use of a battery energy storage system (BESS) to enhance the frequency response characteristics of a low-inertia power system following a disturbance or active power mismatch. A simple control strategy of the BESS is proposed to improve the inertia response and primary frequency response of the system. The effectiveness of the proposed control strategy is evaluated on two test systems, which have been modified by replacing some fossil fuel-based generators with solar photovoltaic (PV) systems to create low inertia systems. A BESS is then added to provide additional system inertia. The DigSILENT PowerFactory software is used to model these modified systems with the BESS and to generate the corresponding frequency response characteristics under various power imbalanced conditions. Simulation results indicate that the BESS, with the proposed control strategy, can improve the system rate-of-change of frequency (ROCOF), frequency nadir (minimum frequency), and final steady-state frequency. In the 3-machine system, replacing a traditional power plant with a solar PV farm decreases the frequency nadir from 49.34 Hz to 48.69 Hz following a sudden load increase of 60 MW. However, adding a 30 MW BESS improves the frequency nadir to 49.48 Hz, which is better than the original system. In the 4-machine system, replacing two traditional power plants with solar farms increases the initial ROCOF to 0.55 Hz/s, exceeding the acceptable limit of 0.50 Hz/s for a severe disturbance. However, incorporating a BESS reduces the initial ROCOF to 0.44 Hz/s.