An accurate power control strategy for inverter based distributed generation units operating in a low voltage microgrid

In this paper, a power control strategy is proposed for a low voltage microgrid, where the mainly resistive line impedance, the unequal impedance among DG units and the microgrid load locations make the conventional frequency and voltage droop method unpractical. The proposed power control strategy contains a virtual inductor at the interfacing inverter output and an accurate power control and sharing algorithm with consideration of both impedance voltage drop effect and DG local load effect. Specifically, the virtual inductance can effectively prevent the coupling between the real and reactive power by introducing a mainly inductive impedance. On the other hand, based on the inductive impedance, the proposed accurate reactive power sharing algorithm functions by estimating the impedance voltage drops and significantly improves the reactive power control and sharing accuracy. Finally, considering the different locations of loads in a microgrid, the reactive power control accuracy is further improved by employing an on-line estimated reactive power offset to compensate DG local load effects. The proposed power control strategy has been tested experimentally on a low voltage microgrid prototype.