Events at Department of Energy Technology

Fault detection and coordinated Protection system for AC Microgrids


13.09.2022 kl. 13.00 - 16.00


Noor Hussain, AAU Energy, will defend the thesis "Fault detection and coordinated Protection system for AC Microgrids"


Fault detection and coordinated Protection system for AC Microgrids


Noor Hussain


Prof. Josep M. Guerrero


Prof. Juan C. Vasquez


Associate Professor Sanjay Chaudhary


Associate Professor Amin Hajizadeh, AAU Energy Esbjerg (Chairman)
Associate Professor Nursyarizal Mohd Nor, Universiti Teknologi PETRONAS, Malaysia
Professor Ramon Blasco-Gimenez, Technical University of Valencia, Spain


The protection of AC Microgrids (MGs) has become a crucial issue to ensure the reliable and safe operation of modern power grids as the penetration level of converter-interfaced renewable energy sources (RESs) has increased. Many practical issues must be addressed in modern power grids in order to design a reliable protection mechanism. A number of the practical constraints, such as the operation mode of the MGs employed control strategy and the limitations of the power electronic converters, are what differentiate fault detection, classification, and coordination from the traditional grid protection algorithms. To that end, the first goal of this work is to present the most recent research and developments, as well as the challenges and issues in the field of AC MGs protection. A comprehensive overview of the available fault detection, classification, and location techniques for AC MGs protection and coordination is presented. Furthermore, the available methods are classified, and their benefits and drawbacks are discussed. Two different approaches have been used in this PhD research project for fast and reliable fault detection and to maintain proper coordination between Protection devices ((PDs) and MGs control devices. The first approach proposes a coordinated adaptive fault detection and protection method for various fault types and AC MGs operation modes. During a grid-connected mode, a two-stage characteristic curve is used to detect a high level of fault current; however, the second stage of the characteristic curve is used to detect a low level of the fault, including overload conditions. Based on the offline calculation of fault data collected by dynamic changes and operation modes such as gird connected and island mode, various group settings are used. In real-time, the proposed algorithm switches the group setting of PDs based on any change in network configuration. The fault detection threshold and trip time are set adaptively based on the fault level and system state. Furthermore, the overall trip time coordination of the primary and backup relays is set so that the primary and backup relay pair obtains proper coordination. Following that, a comprehensive coordinated adaptive protection scheme for AC MGs is presented, which can tune their protection setting based on system states and operation mode and can switch the PD setting. Various protective modules, such as directional overcurrent relays (DOCR), DOCRs for the negative sequence of current (NSC), DOCRs for voltage and current THD, differential relays (DFRs), and under-voltage relays (UVRs), are coordinatedly used in the derived adaptive digital fault detection and protection scheme to facilitate reliable and fast fault detection in a different mode of operation of MGs. In addition to the coordinated DOCRs, the NSC, THD, and UVR modules have been coordinated using appropriate time delays tuned by an adaptive algorithm, making the proposed method suitable not only for the grid-connected mode but also for the islanded mode of operation. This project overall conclusion reflects a fast, reliable, and coordinated fault detection and protection system for AC MGs.




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AAU Energy Aalborg


Pontoppidanstræde 105, 9220 Aalborg East, room 4.127