Peak Operation Mode-Matching Online Fast Frequency Response Capacity Estimation for Lithium-ion Battery Energy Storage System

Fast frequency response capacity (FFRC) is critical for frequency support performance and safe operation of battery energy storage system (BESS). Conventional methods fail to match the specific fast frequency response (FFR) requirements of the grid, leading to conservative assessment or inaccurate estimation-caused penalty. This letter proposes a peak operation mode (POM)-matching online FFRC estimation method for BESSs. An elastic resistor-based equivalent circuit model is developed to address modeling inaccuracy under strongly nonlinear impedance behavior during FFR-POM. Then, an impedance construction method is developed to obtain the continuous impedance curve, based on which online FFRC estimation is realized by iterative searching under multiconstraint. Experimental results prove the excellent estimation accuracy of the proposed method under various conditions.