An enhanced decentralized reactive power sharing strategy for inverter-based microgrid

The conventional droop methods can not accurately share reactive power among DG units in an islanded Micro-Grid (MG) because of the mismatched line impedances. This paper proposes an enhanced decentralized control strategy for an MG with inverter-based voltage sources to improve reactive power sharing accuracy. This method is based on the conventional droop curves corrected following a change in the DGs' operating points. Thus, first, any significant load change, DG switching or mode-transfer of the MG as the main reasons for operating point variation is monitored to trigger the local correction process. Next, for each DG units, according to the injected real power disturbance, the reactive power sharing error is estimated. Simultaneously, an integration term is added to voltage droop control to eliminate the error within a transient period. The proposed local correction procedure modifies the slope or y-intercept of the Q-V curve to cancel the impedance mismatch effects and lead DGs to proper active and reactive power sharing. The simulations and experimental tests prove the accuracy of the proposed method. The MGs can easily be equipped with this technique to affordably improve the power quality and reliability of the network.