低压微电网分布式储能系统负荷动态分配方法

Dynamic Load Sharing Method for Distributed Engergy Storage System in AC Low-voltage Microgrids

在孤岛运行的低压微电网中,因线路阻抗的不匹配性,导致传统下垂控制无法按照下垂增益精确均分有功功率,各分布式储能单元必然会出现荷电状态(SOC)差异,造成蓄电池过充电或过放电,缩短了储能单元的使用寿命。针对上述问题,提出了一种低压微电网分布式储能系统分级控制策略。首先通过功率平衡级动态调节虚拟阻抗,消除不匹配线路阻抗对有功分配精度的影响;然后,通过SOC平衡级控制,各个储能单元根据其SOC动态调节有功功率,使得SOC误差以e指数曲线下降,最终实现储能单元在放电过程中SOC均衡。采用动态一致性算法,可实现各分布式储能单元的信息共享,提高了系统的可靠性和灵活性。同时,基于小信号理论对所提控制策略进行了稳定性分析,并讨论加速因子对系统稳定性的影响。仿真对比结果验证了所提控制策略的有效性和可行性。

In the islanded AC low-voltage micro-grid,the accurate sharing of active power cannot be realized by droop gain of the traditional droop control,which is caused by the unmatched line impedance.Differences of state-of-charge(SOC)will exist inevitably in each distributed energy storage unit(DESU),which leads to overcharge or overdischarge and shorter service life of battery.Therefore,a hierarchical control strategy for distributed energy storage system(DESS)in AC low-voltage microgrids is proposed.The virtual impedance is obtained by the power balancing stage,which eliminates the influence of accurate sharing of active power caused by unmatched impedance.In the stage of SOC balancing,each DESU dynamically adjusts the output active power according to SOC,and SOC deviation decreases with e-index curve,ultimately achieveing SOC balancing of the DESUs during discharging process.The dynamic consensus algorithm is applied for information sharing between the DESUs.It can provide higher system reliability,expandability,and flexibility due to its distributed control architecture.The stability of proposed strategy is analyzed based on small signal theory and the influence of acceleration factor is discussed.The simulation comparison results verify the effectiveness and feasibility of the proposed control strategy.