Electronic Theses and Dissertations

Date

2021

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Electrical & Computer Engineering

Committee Chair

Mohd Hasan Ali

Committee Member

Mohd Hasan Ali

Committee Member

Eddie Jacobs

Committee Member

John Hochstein

Abstract

Hybrid microgrids (HMGs) that incorporate the functionalities of both AC and DC load/generation systems are gradually evolving from the concept stage to real-world practice. HMGs can reduce power losses due to decreased requirement of conversions from AC to DC and vice versa. HMGs, particularly in islanded operations, are prone to instability and power fluctuations due to the intermittent nature of renewable energy sources (RES) and the stochastic behavior of the loads. It is imperative to damp system oscillations with faster dynamics and reliable controllers. Converter-interfaced energy storage systems (ESS) are well demonstrated to be the most reliable, technically feasible, and economically viable solutions to manage volt-age/frequency deviations and to enhance the dynamic performance of microgrids.The problem of control and power management of microgrids has been well studied in recent years, and various methodologies have been proposed. However, there are technological gaps in the HMGs are yet to be addressed. This dissertation aims to develop robust control solutions to enhance the resiliency and stability of hybrid AC/DC microgrids against grid disturbances.Among all ESS, the battery energy storage system (BESS) is the most cost-effective and widely accepted technology. This work explores the influence of the BESS operation and proposes novel methodologies to improve the fault ride-through (FRT) capability and disturbance resiliency of microgrids involving complex dynamics characteristics. In addition, this study proposes a novel bidirectional DC-DC converter for energy storage applications in DC and hybrid microgrids. The new converter has a symmetrical configuration that allows designing one controller for both directions. The design approach is based on the linearization and frequency response of the system.Furthermore, a new grid-connected photovoltaic-supercapacitor (PV-SC) energy storage system is proposed where a minimum number of power components are used to implement both functionalities. The proposed PV-SC system improves the dynamic performance of the connected grid system during the daytime, nighttime, and cloudy situations.Appropriate design methodologies and mathematical models have been developed in simulation environments with the maximum possible details to obtain the highest accuracy for linearized models. Simulation results demonstrate the validity and effectiveness of the proposed approaches and show better performance than conventional methods.

Comments

Data is provided by the student.

Library Comment

Dissertation or thesis originally submitted to ProQuest

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