不平衡电网下储能系统直流纹波分析及抑制策略

DC-side Low Frequency Ripple Analysis and Active Suppression Strategy of Energy Storage Inverter Under Unbalanced Grid

针对微电网中三相逆变器接不平衡负荷在储能变流器直流侧引入低频纹波的问题展开研究。通过建立三相两电平变流器开关函数等效模型,分析了低频电流纹波的产生原因,指出直流电流的低频分量主要由不平衡负荷的负序分量引入,且与微网内三相负荷的不平衡度成正比。为降低低次谐波对系统振荡的影响,提高微电网运行的可靠性,提出一种基于重复+比例积分复合控制的Buck-Boost型直流电力弹簧的低频电流抑制方法,并根据建立的电力弹簧小信号频域模型,利用小增益原理对所提出的复合控制策略的稳定性进行了分析,并对重复控制关键环节及参数进行设计。最后,利用Matlab/Simulink仿真模型及2 kV•A实验样机验证了所提方法的有效性。

Aiming at the problem of introducing low-frequency current ripple on the DC side when the threephase inverter in the microgrid is connected to the unbalanced load was studied.By establishing the equivalent model with the switching function,the causes of the low-frequency current ripple were analyzed.It was pointed out that the low-frequency component of the DC current is mainly introduced by the negative sequence phase current caused by the unbalanced load and is related to the imbalance coefficient of the three-phase load.A low-frequency current suppression method based on the Buck-Boost DC energy spring(DCES)with advanced hybrid controller was proposed.Based on the equivalent model of energy spring,the stability of the proposed hybrid control strategy was analyzed using the small gain principle,and the compensation function in the repetitive control was designed.Finally,the simulation model was built in Matlab/Simulink.The simulation results demonstrate the effectiveness of the proposed method.