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Frequency Derivative-Based Inertia Enhancement by Grid-Connected Power Converters With a Frequency-Locked-Loop

Renewable energy sources (RESs) have been extensively employed to replace fossil fuels for reducing carbon footprints. Since RESs are normally coupled to the power grid by fast-response power converters without providing any inertia, the power system inertia generated by synchronous generators continues to decrease, making modern power systems sensitive to frequency events. As a result, undesirable load-shedding, cascading failures, or even large-scale blackouts may occur under severe frequency events. To address the lack of inertia concern, this paper presents a frequency derivative-based inertia enhancement method for battery storage systems. Specifically, the method achieves inertia emulation by proportionally linking the time derivative of the grid frequency and active power references of power converters. The main contribution is to use a frequency-locked-loop to accurately estimate the frequency derivative signal, which avoids the high frequency noises introduced by differential operators. Simulation and experimental results are finally presented to validate the effectiveness of the proposed method.