A Consensus-Based Adaptive Virtual Output Impedance Control Scheme for Reactive Power Sharing in Radial Microgrids

This article presents a distributed secondary control scheme for accurate reactive power sharing in an islanded multibus radial microgrid. The scheme employs consensus control to adaptively tune the virtual output impedance (VOI) into achieving reactive power correction. The adaptive VOI-based control structure is essentially nonlinear. However, this work shows that the approximate range of stable coupling gain can be established by linearizing the problem about every probable operating point of the distributed energy resources (DERs). On the basis of islanding mode, it is also shown that only the dynamic VOI component is needed while the static component, which has been used extensively to date, can be nullified. It will also be shown that under the established gain tuning guideline, the virtual reactance typically results in quicker correction dynamics as compared to the virtual resistance. The proposed control scheme can realize an accurate power sharing among the DERs regardless of the microgrid topology, load condition, and communication delay (within the allowable limits defined by the consensus theorem). This study is carried out in conjunction with an islanded microgrid model modified from the IEEE 34 Node Test Feeder.