Development and Performance Evaluation of Islanding Detection Schemes for Inverter based Distributed Generation Systems

Abstract

Induced by the augmenting prosperity in the developing nations, the demand for newlineenergy is set to rise distinctively. Hence, large numbers of DGs are connected to the newlineexisting electric power system at the distribution level. However, these penetrations call for newlinemany technical challenges in the existing electric distribution system. Among these newlinechallenges, detection of islanding condition is one. This thesis presents different islanding newlinedetection schemes for inverter based distributed generation system suitable for various newlineoperating scenario. Keeping in view the disadvantages of existing detection schemes, newlinefirstly, a modified reactive power control based active detection scheme is proposed.In case newlineof the existing reactive power control (RPC) based scheme, it has the limitation of injecting newlineunwanted reactive power during normal system operation, almost same detection time for newlinevarious percentage of unbalance in load and false detection of islanding for small newlinedisturbances when steady state frequency is close to its threshold limit. In the proposed newlinescheme, to overcome the demerit of unnecessary reactive power injection, the phase angle newline(and#952;) between the actual and the nominal point of common coupling (PCC) voltage is added newlineto the reference reactive power signal of the controller. Further, to achieve relatively faster newlinedetection speed for various percentages of unbalanced load conditions, the positive newlinesequence PCC voltage is used in the detection scheme.