Optimal Coordination of Over-Current Relays in Microgrids Using Unsupervised Learning Techniques

Abstract

Microgrids constitute complex systems that integrate distributed generation (DG) and feature different operational modes. The optimal coordination of directional over-current relays (DOCRs) in microgrids is a challenging task, especially if topology changes are taken into account. This paper proposes an adaptive protection approach that takes advantage of multiple setting groups that are available in commercial DOCRs to account for network topology changes in microgrids. Because the number of possible topologies is greater than the available setting groups, unsupervised learning techniques are explored to classify network topologies into a number of clusters that is equal to the number of setting groups. Subsequently, optimal settings are calculated for every topology cluster. Every setting is saved in the DOCRs as a different setting group that would be activated when a corresponding topology takes place. Several tests are performed on a benchmark IEC (International Electrotechnical Commission) microgrid, evidencing the applicability of the proposed approach.

Application of Intelligent Systems in Volt-VAr Centralized Control in Modern Distribution Systems of Electrical Energy

“…The use of ANNs to solve electrical energy systems problems is an area of growing interest [20]. In turn, DTs correspond to multistage decision-making approaches, which are widely used in many applications [21]. One of the main DTs characteristics is the ability to divide a complex decision process into a simpler set of decisions, providing successful solutions similar to the desired objectives [22].…”

Automatic Overcurrent Protection Coordination after Distribution Network Reconfiguration Based on Peer-To-Peer Communication

“…The operation of this relay depends on its ability to detect a fault in its protection area, but it is limited because the current is the only measured parameter, which is sensitive to the system operating conditions and the network topology. The operation of an overcurrent relay depends on the following setting parameters: the current setting (I s ) or pick-up current, which activates the device, and the Time Multiplier Setting (TMS) or time dial, which is a tuning parameter that permits the setting of the time delay before the relay operates whenever the current (e.g., due to a fault) reaches a value greater than the current setting [6,14].…”

“…Consequently, it can be stated that the main objective of the adjustment of protection coordination problem consists of achieving selectivity with the maximum sensitivity and speed. Nevertheless, it is worth noting that these parameters are not independent, as two of them are more likely to decrease when the other one increases [6,25,41].…”

“…Within this background, if it is clear that ancillary services such as protection systems are mandatory on transmission and distribution grids, where protective systems are designed to ensure minimum loss of load, then it must take into account basic principles such as reliability, speed, selectivity, simplicity and cost [6,7]. Selectivity has been defined as the ability of the overall protection scheme to isolate the fault such that the minimum interruption occurs.…”

AC Microgrids Protection: A Digital Coordinated Adaptive Scheme

“…For instance, in the grid-connected mode, a large current amplitude contribution of the grid may lead to the malfunction of in-coordination of PDs of MG side including fully power electronic-based DGUs [15]. In the islanded mode, conventional PDs such as fuses and overcurrent relays (OCRs) may not properly operate [16], due to significant decrease in DGUs fault current in high penetrated power electronic converters [17] and current limitation block in the primary inner current control loop [18].…”