Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Electrical and Computer Engineering

Supervisor

Dr. Amirnaser Yazdani

2nd Supervisor

Dr. Tarlochan Singh Sidhu

Joint Supervisor

Abstract

This thesis is mainly focused on (i) modeling and control of Electronically Coupled Distributed Energy Resources (EC-DERs) under severe network imbalances and transient incidents, and (ii) protection of active distribution networks and microgrids against different types of faults. In the first part, an enhanced control strategy is proposed to improve the performance of EC-DERs under faults and transient disturbances, in a multi-unit microgrid setting. With the use of proposed control strategy, the host microgrid can ride through network faults, irrespective of whether they take place within the microgrid jurisdiction or impact the upstream grid, and quickly reclaim its pre-fault operating conditions to improve post-fault recovery. Further, the proposed control scheme enables the host microgrid to retain its power quality for the duration of the faults, in both modes of operation, which is a desirable property for detection of certain classes of faults, as well as for sensitive loads.

In the second part of the thesis, appropriate strategies are proposed for protection of low- and medium-voltage microgrids in the islanded mode as well as the grid-connected mode of operation. The proposed protection strategies aim to detect and isolate the faults that impact the microgrid, in a selective manner. The proposed strategies can be implemented through programmable microprocessor-based relays which are commercially available; hence, the structure of new relays that enable the proposed protection strategies are also discussed in the thesis. In addition, the thesis investigates the operation of an existing distribution network as a microgrid. Thus, practical control and protection strategies that enable off-grid operation of the distribution network (considering the system constraints) are discussed. The effectiveness of the proposed control and protection strategies are demonstrated through time-domain simulation studies conducted in the PSCAD/EMTDC software environment.


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