Improving the Performance of the Adaptive Virtual Impedance Method in the Island Microgrid

One of the main challenges in island microgrids is the distribution of reactive power between distributed generation sources. The use of adaptive virtual impedance has been introduced as a method of improving the distribution of reactive power between distributed generation sources. Although the use of adaptive virtual impedance improves the reactive power distribution between the distributed generation sources and reduces the circulating current, it causes a voltage drop and the output voltage range of the distributed generation unit is reduced. In this paper, a control strategy for improving the adaptive virtual impedance method is proposed. In the proposed control strategy, the voltage drop across the output impedance of the distributed generation units is compensated due to the use of increased virtual impedance, and the load supply voltage is adjusted to the nominal value. The proposed control method, in addition to maintaining the advantages of using adaptive virtual impedance such as appropriate distribution of active and reactive capacities between distributed generation units and reducing circulating current, compensates for the voltage drop in the output impedance. In the proposed method, the output reference voltage of the drop control method is adjusted within the allowable range in proportion to the load change. To evaluate performance and efficiency, the proposed control method is implemented on an island microgrid consisting of two distributed generation units. The simulation results show the performance and efficiency of the proposed method.