An Enhanced Virtual Impedance Optimization Method for Reactive Power Sharing in Microgrids

To solve the reactive power sharing issue of the conventional droop control method, communication is commonly used, especially in networked microgrids. However, there are still many occasions where communication has not been established in advance. In such cases, the wireless reactive power sharing strategy based on the virtual impedance optimization can be applied. By designing and optimizing the controller of virtual impedance, the global reactive power sharing error of the microgrid can be minimized. Thus, the reactive power sharing performance of the droop control method is improved accordingly. However, the original optimization method has not considered the different capacities of distributed generation (DG) units, and it is subject to the number of network nodes. In this paper, an enhanced virtual impedance optimization method is proposed to solve the two issues. First, the reactive power estimation method used in the fitness function is modified to adapt to the system that contains DG units with different capacities. Second, a network simplification step is added before the optimization to deal with the system with more nodes. With these improvements, the application scope of the virtual impedance optimization method is greatly extended. Finally, the effectiveness of the enhanced method is verified through a 38-bus system in MATLAB simulation.