基于权重因子和荷电状态恢复的储能系统参与一次调频策略

Primary Frequency Regulation Strategy with Energy Storage System Based on Weight Factors and State of Charge Recovery

电池储能可快速吞吐功率,被视为优质调频资源,但过度充放电会导致其调频能力不足。文中提出一种改善的储能系统参与一次调频效果的控制策略。首先,将储能调频死区设置在机组死区范围内,并结合电网频率特性分析储能调频死区变化对频率的影响。在此基础上,基于权重因子和荷电状态(SOC)恢复提出储能参与的一次调频策略:在频率波动超过储能调频死区时,为避免电池过度充放电提出储能调频系数计算方法,同时引入控制虚拟惯性和虚拟下垂出力比重随频率变化而调节的权重因子,进而设计了调频控制方法;在频率不超过储能调频死区时,兼顾储能恢复需求和电网承受能力,提出储能SOC恢复方法。仿真结果表明:所提策略能有效改善电网频率波动和储能SOC。

The battery energy storage is regarded as a high-quality frequency regulation resource because of its fast power throughput.However,excessive charging and discharging will cause insufficient frequency regulation capability of the energy storage.This paper proposes a control strategy to improve the performance of primary frequency regulation(PFR)with energy storage system.Firstly,the deadband of energy storage is limited within the deadband of units,and the impact of the deadband variation of energy storage on frequency is analyzed with the grid frequency characteristics.On the basis of this,the strategy of PFR with energy storage based on weight factors and state of charge(SOC)recovery is proposed.For the condition that the frequency fluctuation exceeds the deadband of the energy storage,a calculation method of frequency regulation coefficients for energy storage is proposed,which is used to avoid excessive charging and discharging of batteries.Meanwhile,two weight factors of the virtual inertia control and the virtual droop control are introduced,whose ratios vary with the frequency,and then the control method of frequency regulation is designed.For the opposite condition that the frequency fluctuation does not exceed the deadband of frequency regulation for the energy storage,a method of the SOC recovery is put forward,which takes the need of the energy storage recovery and the grid tolerance into account.Simulation results indicate that the proposed strategy can improve the frequency fluctuation of the grid and the SOC of the energy storage.