基于动态虚拟阻抗的多并联逆变器间环流抑制控制策略

Control strategy based on dynamic virtual impedance to suppress circulating current between multiple parallel inverters

孤岛微电网中基于下垂控制的各分布式电源逆变器并联运行,其参数差异会引发系统环流。为此提出一种基于动态虚拟阻抗的环流抑制策略。首先分析了采用下垂控制的逆变器并联时所产生环流的组成成分,得出无功环流占主导以及线路阻抗不匹配造成无功环流的结论。其次在虚拟阻抗中引入无功反馈项,实现无功精确分配,从而抑制无功环流。通过在电压控制方程中加入电压补偿项以消除线路压降,对传统的下垂控制策略进行改进,进一步抑制无功环流。最后在MATLAB/Simulink中搭建了3台逆变器并联的微电网模型,仿真实验结果表明,动态虚拟阻抗控制策略可以消除线路阻抗的影响,实现逆变器间无功功率的精确分配,解决多并联逆变器间的环流问题。

Inverters of distributed power generation are operated in parallel in islanding microgrid,which causes the circulating current by the difference of their parameters.Therefore,a circulating current suppression strategy based on dynamic virtual impedance is proposed.Firstly,the composition of the circulating current based on droop control is analyzed,and it is concluded that the reactive circulating current is dominant,and the mismatch of line impedance causes the reactive circulating current.Secondly,the reactive power feedback term is introduced into the virtual impedance to realize the accurate distribution of reactive power,so as to suppress the reactive circulating current.Meanwhile,the traditional droop control strategy is improved,and the voltage compensation term is added into the voltage control equation to eliminate the line voltage drop and further suppress the reactive circulating current.Finally,a microgrid model with three inverters in parallel is built in MATLAB/Simulink.Simulative results show that the dynamic virtual impedance control strategy can eliminate the influence of line impedance,realize the accurate distribution of reactive power among inverters,and solve the problem of the circulating current among multiple parallel inverters.