Reactive Power Sharing Among Distributed Generation Sources in Islanded Microgrids to Improve Voltage Stability

Abstract

Extensive use of distributed generation (DG) resources in distribution systems and uncertainty of the daily active power of these sources have caused the connection bus voltage to deviate from the allowable limit. DG reactive power control is of one the solutions for this problem. The purpose of this paper, in addition to controlling the bus voltage, is to share reactive power between the DG resources and to maintain the maximum active power level produced by the DGs. Reactive power sharing issues are unavoidable due to the difference in impedance of the DGs feeders and the different classifications of the DG units in the conventional drop control scheme. In this paper, reactive power sharing among generation resources are used to improve voltage stability. Virtual impedance method has also been used as one of the methods of reactive power sharing between sources to show and compare reactive power sharing methods between DG sources. In order to show the voltage improvement in this paper, the stability index L_index has been used. The proposed L_index has been confirmed against the existing methods for evaluating voltage stability using the reactive power sharing method in this study. This study is carried out in conjunction with an islanded microgrid model IEEE 38-BUS, the voltage stability of the corresponding microgrid buses has been shown. Voltage stability is achieved by reactive power sharing among distributed generation sources and is demonstrated in this study.