基于动态小波分解的混合储能系统平滑控制策略

为平抑分钟级的功率波动,使风电功率满足并网标准,基于小波分析提出功率分配数动态变化的混合储能系统(hybrid energy storage system,HESS)控制策略。设计了功率分配数根据风电功率超短期预测结果和HESS的荷电状态(state of charge,SOC)动态调整的分频方法,从而改变并网的低频目标功率和需要蓄电池、超级电容平抑的中、高频功率;建立兼顾HESS控制成本、功率平滑度的多目标优化函数,并应用改进的NSGA-Ⅱ算法对功率分配数进行滚动优化,从而达到最优控制;针对基本NSGA-Ⅱ算法在维持种群多样性、均匀性上的不足,以及种群规模大的问题,对精英保留策略进行了改进。最后,通过美国某州风电场实际观测数据进行实例验证,结果表明,所提控制策略能充分发挥不同类型储能的优势,经济、快速地平抑风电功率波动。

A Hybrid Energy Storage Smoothing Control Strategy Based on Dynamic Wavelet Transform

To smooth minute-level wind power fluctuation and make wind power satisfy the grid standard, this paper proposes a control strategy of hybrid energy storage system (HESS) with the power allotment levels adjusting dynamically based on wavelet analysis.And this paper designs a method of frequency division that the pwer allotment levels adjust according to the result of wind power short-term prediction and the state of charge (SOC) of HESS, which can change the low-frequency target power into power grid, as well as the middle and high frequency power absorbed by battery and super capacitor respectively.Then, this paper establishes a multi-objective optimization function considering the control cost and smoothness of HESS, and applies improved NSGA-Ⅱ algorithm to achieve rolling optimization, calculate the optimal power allotment levels and obtain the optimal control strategy.This paper improves elitism strategy to overcome the shortage of basic NSGA-Ⅱ algorithm in maintaining population diversity, the lack of uniformity and large population size problem.Finally, case studies through the actual observation data of a wind farm in the United States demonstrate that the proposed control strategy takes advantage of different types of energy storage and smooths the fluctuation quickly and economically.