Long-term stable operation control method of dual-battery energy storage system for smoothing wind power fluctuations

Abstract

Since wind output power shows obvious fluctuations characteristics, direct grid-connection will bring great challenges to the safe and stable operation of the power system. In order to achieve better economic benefits, this paper adopts the dual-battery energy storage system (DBESS) operation mode which performs charge–discharge tasks separately considering the discharge depth and frequent charge–discharge conversion on battery life. However, the extreme operation will occur when considering the imbalance of charge and discharge energy of DBESS, which will make it difficult for DBESS to maintain long-term stable operation to smooth the wind output power. Besides this paper proposes a charge–discharge operational stability index for characterizing the system operation status, based on the real-time operating conditions of the energy storage system and wind power fluctuations. To ensure the DBESS long-term operation stability, the extreme operation problems caused by charge–discharge unbalanced energy in the long-term operating process must be solved. This paper used two proposed indicators as input factors and proposed a control strategy to adaptively fine-tune the first-order low-pass filtering time constant, to charge the battery throughput power in real-time and optimize two battery packs’ State of Charge (SOC). The effectiveness of the proposed control strategy is verified from two aspects by using MATLAB/Simulink software: the SOC optimizing control effect and the power fluctuation smoothing effect.