Abstract
In this paper, we analysed the growing penetration of generating units from renewable energy sources in transmission power systems. Among the possible effects of the interaction of distributed generation (DG) with transmission systems, we considered the abnormal operating conditions caused by short circuits in the transmission systems and the resulting voltage sags that occur in the network. A systematic method is presented for analysing the voltage sag behaviour of any transmission system in which large DG units are connected to the transmission system by means of High Voltage/Medium Voltage (HV/MV) stations. The method proposed for obtaining the voltage sags is the fault position method (FPM), from which we derived a graphical visualization of the during-fault voltage (DFV) matrix as a valuable tool to obtain an immediate measure of the propagation of voltage sags in the network. The results obtained were based on a portion of a real transmission system. The system that we considered is an actual portion of the Italian transmission system, and all of the quantities we used were obtained from the data of the Transmission system operator (TSO).
Highlights
The increasing penetration of generating units from renewable energy sources is expanding the boundaries of power system studies
An important feature of this paper is that the system we considered is a portion of the Italian transmission system, and all of the quantities we used were obtained from the data of the Transmission system operator (TSO)
This study provides a systematic method for analysing the behaviour of voltage sags in any transmission system in the presence of large distributed generation (DG) units connected to the transmission system by means of High Voltage/Medium Voltage (HV/medium voltage (MV)) stations
Summary
The increasing penetration of generating units from renewable energy sources is expanding the boundaries of power system studies. A graphical color scheme was proposed to obtain immediate information on the voltage-sag performance for the entire system obtained by the FPM [19,24] This graphical visualization allows one to immediately ascertain where changes in the external condition occurred and whether they affected the electrical power system’s ability to maintain the severity of the sags at assigned levels. We compare the during-fault voltage in generic node k due to the fault in f before increasing the short-circuit power of node f (V(k, f )) with the same quantity after the change (V new (k, f )). It is not always possible to neglect the resistances in an actual electric power system, so the considerations in Table 1 should be verified by considering the terms of the Zsc (k, f ) matrix rather than the terms of the Xsc (k, f ) matrix, as will be shown in the numerical application in which an actual transmission system is analyzed
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