基于改进下垂控制的微网孤岛运行研究

Research on Islanded Operation of Microgrids Based on Improved Droop Control

针对传统下垂控制不能稳定微网频率的缺陷,在有功-频率(P-f)下垂方程中引入Sigmoid函数,使微网的频率能自主限制在一定范围内,保证微网的频率稳定性。在多微源并联微网系统中,由于线路阻抗差异引起的无功功率分配问题,采用修正无功-电压(QV)下垂系数来补偿线路阻抗的压降,从而提高功率分配精度,并限定了电压的范围,使负荷点电压得到了保证。在PSCAD仿真软件中搭建了模型,仿真结果验证了引入Sigmoid函数和修正系数法的下垂控制,能使微网频率和负荷点电压自动保持在一定的范围内。改进的下垂控制策略适用于多微源微网在孤岛模式下的控制系统,可以提高微网运行的稳定性。

As traditional droop control couldnt stablize frequency of microgrids, Sigmoid function is introduced into the active power- frequency （ P - f） control, which enables the customization of the frequency limit within a certain range and ensures the stability of frequency in mierogrids. For multi -inverters parallel operation in microgrids, this paper corrects reactive power- voltage （Q -V） droop coefficients to compensate the voltage drop caused by the line impedance, whose difference could lead to the problem of the active power sharing. This method could improve the accuracy of power distribution and limit the range of load voltage to guarantee the voltage at the load. In this paper, the model is built in PSCAD simulation software. The simulation results show that the improved droop control with sigmoid function and the method of correcting coefficients could keep frequency and voltage in a limited range automatically. The im- proved droop control is suitable for control system in islanded microgrids with mutiple microsources, which could improve the stability of mierogrid system.