Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Doctor of Philosophy

Program

Electrical and Computer Engineering

Supervisor

Dr. Jing Jiang

Abstract

The past decade has seen a significant rise in proliferation of roof-top photovoltaic (PV) systems with storage units at residential sites. This has affected the way power system engineers and researchers have previously studied distribution systems as passive networks. With the introduction of these local distributed energy resources, a distribution system has become part of an active network. This modernization of the power distribution network, brings along with itself a number of key issues that need to be pro-actively tackled by the local utilities.

In North America, with family-owned roof-top PV systems, storage devices and electric vehicles, the concept of central generation has transformed to local distributed generation (DG). With this phenomenon reshaping the current perspective of distribution networks, the local generation and storage capacities, with their respective controllers, allow for these DG units to be grouped together to form single-phase microgrids most commonly referred to as residential microgrids. This thesis looks into the two key issues pertaining to residential microgrids i.e. accommodating multiple embedded generation and energy storage units while balancing the generation and loading in each phase to achieve overall three-phase system balance.

A benchmark distribution system model is proposed in this thesis to study residential microgrids both in grid-connected and islanded modes. Limitations in existing distribution network models have been identified along with possible architectures for these residential microgrids. The configuration parameters of the benchmark model have been carefully selected after consultation with the London Hydro (local power utility in London, Ontario). Several case studies have been presented to show that the proposed benchmark model can be used to represent a particular architecture of the residential microgrids.

Mathematical foundations of balancing residential microgrids through back-to-back converters have been developed in this thesis, which lay the foundation stone of the subsequent contributions with regards to this thesis. An online toolkit is developed in LabVIEW from the derived mathematical formulations.

Two power management strategies for single-phase residential microgrids, namely intra-phase and inter-phase power management strategies have been proposed which cater for the coordinated control of these single-phase microgrids to balance generation and loading in all of the three-phases seen from a primary feeder.

An operational control strategy has been later studied for optimal selection of power surplus phase(s) to mitigate the deficit(s) in other phase(s). This allows the system to transfer power from the surplus phase(s) to power deficient ones to achieve an overall balance, despite diverse load demand profiles in each phase.

An experimental validation of the proposed control strategies has been carried out with laboratory-scale design and development of the back-to-back converter along side single-phase sources, loads and a control platform to mimic a typical residential microgrid. From the experimental results, it is concluded that phase imbalance can be mitigated by the transfer of surplus power from a phase to the power deficit phase.

This work on power balancing single-phase residential microgrids can potentially open up new areas of research in the field of microgrids, especially with an unprecedented growth of roof-top PV panels.

Summary for Lay Audience

In North America, with roof-top PV systems, storage devices and electric vehicles, the concept of central generation has transformed to local distributed generation. With this phenomenon reshaping the current distribution networks, the local generation and storage capacities with their respective controllers allow for these generation units to be grouped together to form single-phase microgrids most commonly referred to as residential microgrids. The thesis looks into the two key issues pertaining to residential microgrids i.e. accommodating multiple embedded generation and energy storage units while balancing the generation and loading in each phase to achieve overall three-phase system balance. An experimental validation of the proposed control strategies has been carried out with laboratory-scale design and development of the back-to-back converter and a control platform to mimic a typical residential microgrid. This work on power balancing single phase residential microgrids can potentially open up new areas of research in the field of microgrids.

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