Advanced frequency control strategy for power systems with high renewable energy penetration: A battery energy storage system approach

This study proposes an optimal control strategy for battery energy storage systems to support frequency regulation in power systems with high renewable energy penetration. The algorithm generates a sinusoidal reference signal for the pulse-width modulation scheme of the direct current/alternating current converter, adjusting it based on voltage magnitude and phase set points. The control system integrates multiple loops to manage frequency, voltage, active and reactive powers, charge, and current controllers on the d- and q-axes. It limits frequency deviations and improves the rate of change of frequency. An adaptive nonlinear droop control method, combined with state-of-charge (SOC) feedback, regulates active power-frequency control to enhance grid stability. The SOC feedback mechanism enables dynamic charge and discharge operations, ensuring that frequency remains within operational limits. Simulation results, validated using modified Vietnamese Tay Nguyen 500/220 kV and IEEE 39-bus systems with DIgSILENT/PowerFactory, show that the proposed method outperforms the conventional CBEST model in scenarios involving sudden generation outages or fluctuating renewable energy output. This method meets the frequency stability requirements set by the Circular No. 25/2016/TT-BCT of the Vietnamese Ministry of Industry and Trade, ensuring that the system operates within a stable frequency range of 49.5–50.5 Hz under 120 s and recovers to 49.8–50.2 Hz within 300 s.