基于自适应虚拟阻抗的微网下垂控制策略

Droop Control Strategy with Adaptive Virtual Impedance in Microgrid

在微电网中,各个分布式发电(Distributed Generation,DG)单元的线路阻抗往往不相同,造成DG输出的无功功率不能准确分配。提出一种基于自适应虚拟阻抗的下垂控制策略,通过通信线路各个DG可以共享功率信息。在线路阻抗未知的情况,控制系统可以利用接受到的功率信息来对虚拟阻抗进行调整,使虚拟阻抗的值能够跟踪DG之间线路阻抗的差值。虚拟阻抗调整完成后,各个DG输出的无功功率能够按容量准确分配,只要线路阻抗不发生变化,通信系统不参与控制都能获得理想的控制性能。即使在虚拟阻抗调整过程中出现通信中断,该控制策略的性能也比传统的下垂控制更好。MATLAB仿真验证了该控制策略的有效性。

Unequal feed impedance among the distributed generation （DG） unit could resuh in poor power sharing in the islanded micro - grid. The influence of the feed impedance on output power is analyzed, and the droop control based on adaptive virtual impedance is proposed, which shares reactive power signal by communication link. When DG gets a power signal, the adaptive virtual impedance is designed to track the feeder impedance difference which causes the power sharing errors. Once the virtual impedance is adjusted, the DG output power will achieve accurate power sha- ring as long as the feed impedance remains unchanged. Even if communication interrupts during the virtual impedance being adjusted, the proposed strategy will still outperform the convention droop control. The simulation results verify the effectiveness of the proposed strategy.