SoC threshold optimization for battery storage in frequency regulation considering uncertainty of SoC measurement and automatic generation control fatigue loss of thermal power system

The min/max state of charge (SoC) thresholds of battery storage (BS), which challenge the economics of frequency regulation (FR), have a certain degree of uncertainty and need to be artificially re-calibrated after a period of operation time. To tackle this challenge, a SoC threshold optimization method is proposed for joint FR by thermal power (TP) and battery storage (BS) by comprehensively considering the automatic generation control (AGC) fatigue loss cost of TP and the aging degradation cost of BS. The proposed method consists of three parts: 1) the AGC fatigue loss cost of TP is computed by considering motion loss cost (e.g., steam turbine rotor, oil servo-motor, steam gate valve stem) and static loss cost (e.g., steam drum, cylinder); 2) the aging degradation cost of BS is formulated by considering also the uncertainty of SoC; 3) the min/max SoC operation thresholds of BS are optimized through the surrogate Lagrangian relaxation (SLR) method by comprehensive considering of the AGC fatigue loss and aging degradation cost of FR. Results of extensive simulation tests have clarified and verified the economic effectiveness of proposed min/max SoC threshold optimization method for the joint frequency regulation by thermal power and battery storage.