Active and Reactive Power Sharing in Inverter Based Droop-Controlled Microgrids

Accurate power sharing is essential for the successful operation of an islanded microgrid with droop-controlled inverters particularly at times when the total loads served in the system change significantly like during microgrid black start. In this paper, two paradigms for active power load sharing were derived: 1) load sharing by the proportion of active power limit set by the DC primer mover of DGs and 2) load sharing by the proportion of optimized reference active power. Further, a method was derived for approximate sharing of reactive power by choosing the coupling inductance of the droop-controlled inverters, which though not as precise as active power sharing, could be coordinated by a microgrid central controller to ensure good voltage regulation. The load sharing method was validated by a simulated black start test case with droop-controlled inverters and aggregated loads restored in sequence.