Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Engineering Science

Program

Electrical and Computer Engineering

Supervisor

Srikantha, Pirathayini

Abstract

Rising climate change concerns in recent years have instigated the emergence of sustainable sources to reduce dependence on high-emission, isolated bulk generation systems. The microgrid framework relies on integrating these distributed energy resources (DERs) to achieve regional energy independence that leads to a reliable and environment-friendly power grid. In this work, highly granular and decentralized coordination schemes are proposed that will enable fast computation of source dispatch set-points, thereby appropriately accounting for frequent changes in regional load-supply configuration of a microgrid. The mathematical models utilized in the study sufficiently represent the steady-state electrical interdependencies and feasibility limits in islanded or grid-connected operation modes. Applying alternating direction method of multipliers (ADMM) algorithm, the coordination process is transformed into a decentralized multi-agent problem involving minimal information exchange between subsystems. To overcome non-convexities typically present in optimization problem of microgrids, the two distinct convex relaxation techniques utilized are: 1) Linearization and 2) S-procedure. In separate coordination schemes, the former lends the advantage of extremely fast computation speed, while the latter exploits the hidden convexity in the decomposed coordination problem to deliver solutions with superior feasibility guarantee. Finally, the convergence, feasibility and scalability of the proposed coordination techniques are assessed with simulation studies performed on realistic microgrid parameters and several IEEE test systems.

Summary for Lay Audience

Rising climate change concerns in recent years have instigated the emergence of sustainable energy sources to reduce dependence on high-emission, isolated bulk generation systems. The grid is being segmented into small regional blocks named microgrids that are ideally self-sufficient due to the incorporation of distributed generation systems known as DERs. The combination of these independent blocks is redefining the structure of the modern electrical grid, which is aptly named as smart grid. The much required paradigm shift from conventional unidirectional structure to a dynamic and autonomous grid has improved the reliability and resiliency of energy delivery manifold. As the technology allows for a widespread energy penetration from potentially every single household, challenges arise as to making the process of energy sharing economical, whilst sustaining the technical integrity of the grid. To this end, this work contributes a decentralized scheme for optimizing power-sharing among the participating energy supply systems (DERs) in the microgrids, so as to ultimately minimize the cost of energy consumption for the energy consumers. The applicability of an individual scheme from the offered variety in this work would depend on the characteristics of the system loads and logistic limitations. The coordination scheme is foreseen to work in tandem with transient control mechanisms that deals with initial oscillations and abrupt changes in system model between two instances of coordination shot. Therefore, the combined source control system will be robust and economically-efficient in facilitating the seamless operation of a microgrid and as a whole, the smart grid system.

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