Master's Theses

Date of Award

2017

Document Type

Thesis

Department

Engineering

First Advisor

Ahmed Mohamed

Keywords

Microgrid, Control, Communication, DC, State, Cluster, State Machine

Abstract

The U.S. electric power industry is undergoing unprecedented changes triggered by the growing electricity demand, and the national efforts to reduce greenhouse gas emissions. Moreover, there is a call for increased power grid resiliency, survivability and self-healing capabilities. As a result of these challenges, the smart grid concept emerged. One of the main pillars of the smart grid is microgrids. In this thesis, the technical merits of clustering multiple microgrids during blackouts on the overall stability and supply availability have been investigated.

We propose to use the existing underground distribution grid infrastructure, if applicable, during blackouts to form microgrid clusters. The required control hierarchy to manage microgrid clusters, and communicate with the Distribution Network Operator (DNO) has been discussed. A case study based on IEEE standard distribution feeders, and two microgrid models, has been presented. Results show that clustering microgrids help improve their performance and that the microgrid total rotating mass inertia has a direct impact on the overall stability of a microgrid cluster.

The design and control of individual microgrids have been given genuine attention in this thesis since they represent the main resiliency building block in the proposed clustering approach. Therefore, a considerable portion of this thesis is dedicated to present studies and results of designing, simulating, building and testing a direct current (DC) microgrid. The impact of various operational scenarios on DC microgrid performance has been thoroughly discussed. Specifically, this thesis presents the design and implementation of the City College of New York (CCNY) DC microgrid laboratory testbed. The experimental results verify the applicability and flexibility of the developed microgrid testbed. An autonomous communication-based centralized control for DC microgrids has been developed and implemented. The proposed controller enables a smooth transition between various operating modes. Finite state machine (FSM) has been used to

mathematically describe the various operating modes (states), and the events that may lead to mode changes (transitions). Therefore, the developed centralized controller aims at optimizing the performance of MG during all possible operational scenarios, while maintaining its reliability and stability. Results of selected drastic cases have been presented, which verified the validity and applicability of the proposed controller.

Since the proposed microgrid controller is communication-based, this thesis investigates the effect of wireless communication technologies latency on the performance of DC microgrids during islanding. Mathematical models have been developed to describe the microgrid behavior during communication latency. Results verify the accuracy of the developed models and show that the impact may be severe depending on the design, and the operational conditions of the microgrid just before the latency occurs.

We propose to use the existing underground distribution grid infrastructure, if applicable, during blackouts to form microgrid clusters. The required control hierarchy to manage microgrid clusters, and communicate with the Distribution Network Operator (DNO) has been discussed. A case study based on IEEE standard distribution feeders, and two microgrid models, has been presented. Results show that clustering microgrids help improve their performance and that the microgrid total rotating mass inertia has a direct impact on the overall stability of a microgrid cluster.

The design and control of individual microgrids have been given genuine attention in this thesis since they represent the main resiliency building block in the proposed clustering approach. Therefore, a considerable portion of this thesis is dedicated to present studies and results of designing, simulating, building and testing a direct current (DC) microgrid. The impact of various operational scenarios on DC microgrid performance has been thoroughly discussed. Specifically, this thesis presents the design and implementation of the City College of New York (CCNY) DC microgrid laboratory testbed. The experimental results verify the applicability and flexibility of the developed microgrid testbed. An autonomous communication-based centralized control for DC microgrids has been developed and implemented. The proposed controller enables a smooth transition between various operating modes. Finite state machine (FSM) has been used to mathematically describe the various operating modes (states), and the events that may lead to mode changes (transitions). Therefore, the developed centralized controller aims at optimizing the performance of MG during all possible operational scenarios, while maintaining its reliability and stability. Results of selected drastic cases have been presented, which verified the validity and applicability of the proposed controller.

Since the proposed microgrid controller is communication-based, this thesis investigates the effect of wireless communication technologies latency on the performance of DC microgrids during islanding. Mathematical models have been developed to describe the microgrid behavior during communication latency. Results verify the accuracy of the developed models and show that the impact may be severe depending on the design, and the operational conditions of the microgrid just before the latency occurs.

Available for download on Wednesday, November 29, 2017

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