Combined Control Strategy for Proportional Current Sharing in DC Microgrid Clusters

The integration of adjacent dc microgrids (MGs) results in the formation of a dc MG cluster which can increase the system power supply capacity. This article proposes a control strategy for dc MG clusters which combines communication-free control and distributed fixed-time control to simultaneously achieve current sharing and voltage regulation with excellent transient characteristics. Firstly, a communication-free control, which presents greater flexibility than the distributed control, is used in the dc MG layer. Subsequently, the distributed fixed-time control is used in the dc MG cluster layer to balance the output current of each MG. The optimal control parameters are obtained by using the zero-pole distribution diagram and establishing a small-signal model of the dc MGs; the stability of the proposed control strategy is also verified. Different scenarios are considered to validate the plug-and-play capability and controller performance by using a dc MG experimental prototype. Real-time hardware-in-the-loop verification containing three MGs is conducted using two RT-boxes to prove the scalability of the proposed cluster control.