基于线路观测器的孤岛运行微电网改进下垂控制策略

Improved Droop Control Strategy Based on Line Impedance Observer in Islanded Microgird

在孤岛运行的微电网中,因微电网中各设备等效线路不匹配性,导致采用下垂控制的分布式电源(DG)难以按其各自的容量对功率进行合理分配,为此,提出了一种基于线路阻抗观测器的改进下垂控制策略。首先,基于本地测量信号设计了线路观测器以辨识线路阻抗参数,并添加电压观测器来抑制电压扰动带来的影响;其次,基于所得线路阻抗的观测值,提出一种改进下垂控制策略来降低分布式电源功率的功率分配偏差;最后,通过Matlab/Simulink搭建模型来进行仿真。仿真结果表明,在不同线路阻抗工况下,所设计的线路阻抗观测器能够准确辨识等效线路阻抗值,基于其辨识值的改进下垂控制策略可有效补偿不匹配线路所引起的电压降,从而大幅降低微电网中不同DG无功功率分配的偏差,使得无功功率功率在不同DG间得到合理分配。因此所提出的改进下垂控制具备良好的动态和稳态性能,且保证了DG单元的即插即用性。

In islanded operation mode of microgrid, it is difficult for the distributed generation（DG） units with conventional droop control to share the load according to their rated capacities, due to the mismatched line impedance of different units. Consequently, we propose an improved droop control scheme on the basis of the line impedance observer. Firstly, an observer is designed to identify the parameters of line impedance based on local measurement; it also adds a voltage observer to eliminate impact caused by the external voltage disturbance. Secondly, based on the estimated value of line impedance, an improved droop control is proposed to reduce the power sharing error among different distributed generation units. Finally, the simulation model is built on MATLAB/Simulink. The simulation results demonstrate that the real value of line impedance is able to be accurately estimated by the observer designed in this paper. The proposed droop control based on the estimation result of line impedance can effectively compensate the voltage drop caused by the mis- matched line impedance, and greatly reduces the sharing error among the different DGs, which make DG to share the reactive power in a reasonable way. The proposed droop control has good dynamic and steady performances and ensures the capability of DG＇s plug-and-play.