考虑充放电能量不均衡的双电池系统状态评估与控制策略

电池使用寿命是风电场功率波动平抑场景中影响储能系统经济性的重要因素。为了延长电池使用寿命,基于充放电任务分开执行的双电池系统运行模式,建立了给定最佳放电深度运行的双电池储能系统充放电数学模型,讨论了该运行模式下因充放电能量不均衡出现的极端运行情况。针对储能系统的实时运行状况和风电功率的波动情况,提出了能够表征双电池储能系统运行能力的充放电饱和能力指标和充放电运行平稳度指标,进而设计了模糊控制策略以自适应调节低通滤波器时间常数,优化控制储能电池的荷电状态,避免系统进入因充放电能力不足的不稳定运行区间。利用MATLAB/Simulink仿真平台,从荷电状态优化控制效果和波动平抑效果两方面对所提控制策略进行了仿真分析。仿真结果表明,所提模糊控制策略能够维持双电池储能系统长期稳定运行,并保证了波动平抑效果。

State Evaluation and Control Strategy of Dual-battery System Considering Unbalance of Charging and Discharging Energy

The lifetime of battery is an important factor affecting the economics of battery energy storage system(BESS)for smoothing wind power fluctuation. To extend the BESS lifetime, the charging or discharging model of dual-battery energy storage system(DBESS)with the most appropriate depth of discharge(DOD)is established based on the DBESS operation principle of separately charging or discharging. And the extreme operating conditions are studied due to the unbalanced energy between the process of charging and discharging. According to real-time status of DBESS and wind power fluctuations, the charging and discharging saturation index and stability index of DBESS are listed. To avoid DBESS operating in the unstable regions with less charging and discharging capacity, the fuzzy control strategy is adopted to adaptively adjust the time constant of low-pass filter so that the battery state of charge(SOC)status can be optimized. Finally, the proposed control strategy is simulated and analyzed on MATLAB/Simulink simulation platform. The results show that the proposed fuzzy control strategy can not only maintain the long-term stable operation of DBESS but also ensure the suppression effect.