Accurate Current Sharing and PCC Voltage Restoration in LVDC Microgrid without Communication Network

Abstract

In this paper, a control strategy is proposed for both accurate current sharing among distributed generators (DGs) and the point of common coupling (PCC) voltage restoration in low voltage direct current (LVDC) microgrid by injecting a small AC signal to the output voltage of the DG. The small AC signal frequency changes proportionally to the per unit (pu) output current of the corresponding DG, and the DG output voltage is regulated to share every DG with the equivalent frequency in the steady state. Especially, for easy implementation, the reactive power of the AC signal is controlled to indirectly regulate the AC signal frequency. Moreover, the equivalent pu output current is used to determine the voltage shift-up in order to restore the PCC voltage. Because the proposed control scheme is developed with the fully distributed manner at local controller for each DG, it can be implemented economically without external communication network. The effectiveness of the proposed control method is proved by the simulation.