基于虚拟阻抗的低压微电网功率均分控制策略

Power Sharing Control Strategy for Low-Voltage Microgrid Based on Virtual Impedance

在低压逆变器并联系统中,各逆变器之间存在线路阻抗不匹配的情况,针对传统下垂控制策略无法实现无功功率的精确均分,且会产生较大环流的问题,提出一种基于虚拟阻抗技术的改进下垂控制策略。该控制策略中,首先采用虚拟阻抗技术使等效线路呈感性,以实现功率完全解耦;其次在无功-电压下垂控制的基础上,采用电压补偿的方法解决无功功率无法均分和系统环流较大的问题;最后搭建逆变器并联系统仿真模型进行验证分析。结果表明,该方法能够很好地实现无功功率的精确均分,补偿因虚拟阻抗而产生的电压降落,同时减小了逆变器系统间的无功环流量,加快其动态响应速度,提高了系统的稳定性和可靠性。

In view of the mismatching of line impedance between the inverters in the low-voltage inverter parallel system,as well as the failure of the traditional droop control strategy to achieve the accurate equalization of reactive power,thus leading to a large circulating current problem,an improved droop control strategy based on virtual impedance technology has thus been proposed.This control strategy uses the virtual impedance technique to make the equivalent circuit inductive for a realization of the complete power decoupling.Secondly,on the basis of reactive power voltage droop control,the method of voltage compensation is adopted to overcome the failure of the reactive power to be divided equally and the flaw of a large system circulation.The results show that this method can realize the accurate distribution of reactive power,the compensation of the voltage drop caused by virtual impedance,the reduction of the reactive power flow between inverter systems,the acceleration of the dynamic response speed,as well as the improvement of the stability and reliability of the system.