A Simple Decentralized Islanding Microgrid Power Sharing Method Without Using Droop Control

In this paper, a modified double-loop voltage controller is developed to enhance the power sharing control of islanding microgrid, without the involvement of conventional droop control concept. Unlike the conventional double-loop voltage control, where the inner and outer control loops are both implemented in the distributed generation (DG) unit local controller, the proposed method has an outer voltage control loop implemented in the microgrid central controller as secondary control to directly regulate the point of common coupling (PCC) voltage with reduced harmonics and magnitude/frequency variations. At the same time, an accurate power sharing is achieved by a modified inner control loop with internal impedance at DG unit local controllers. In contrast to the conventional series external virtual impedance for power sharing enhancement that can affect PCC voltage regulation, the internal impedance here can be very large but without affecting the control accuracy of PCC voltage. Furthermore, the overall control scheme has low computational load and the parameter design is straightforward. To reduce the communication burdens between PCC central controller and DG unit local controller, the DG unit fundamental line current is utilized as a novel synchronizer. With the use of ahovementioned control method, a proper power sharing and nearly zero PCC voltage control error can be achieved.