基于等效馈线的孤岛微网并联逆变器间环流抑制策略

The circulating current suppressing strategy based on equivalent feeder for parallel inverters in islanded microgrid

孤岛微网中,三相并联逆变器间会因输出电压偏差及线路阻抗不匹配而产生环流。本文综合考虑了外接电感、本地负载和线路阻抗对环流的影响,提出了基于等效馈线的并联逆变器间环流抑制策略。在下垂控制的参考电压中补偿等效馈线电压降,并通过动态虚拟复阻抗调节负载波动及逆变器间阻抗差异,以减弱线路阻抗固有阻性成分并提高其匹配精度。仿真研究表明,等效馈线阻抗计算能够反映网络参数的变化,含电压降补偿的下垂控制配合动态虚拟复阻抗调节,可有效抑制逆变器间环流,并提高功率分配精度。

In islanded mode microgrid, circulating current among parallel inverters due to the voltage differences and disproportionate line impedances cannot be neglected. In this paper, the influence of external inductor, local load and line impedance on circulating current is taken into consideration in the equivalent feeder calculation. The equivalent feeder voltage drop is calculated and added to the reference voltage of droop control as voltage compensation. Meanwhile, adaptive virtual complex impedance is adopted to provide quick responses to load change and the mismatch of line impedances, which can reduce the resistant part of line impedance and improve the line impedance proportional accuracy. Simulation results show that the equivalent line impedance calculation method can reflect the variation of grid parameters. The proposed control strategy can suppress the circulating current well and improve the accuracy of power proportional sharing.