Date of Award

12-2017

Degree Name

Doctor of Philosophy

Department

Electrical and Computer Engineering

First Advisor

Dr. Johnson A. Asumadu

Second Advisor

Dr. Massood Z. Atashbar

Third Advisor

Dr. Ala Al-Fuqaha

Abstract

Microgrids consist of many distributed energy sources (DERs) and the overall system is viewed as a number of subsystems. In this work, a finite control set model predictive control is proposed to control power converters in both grid and island modes of operation of the microgrid. Each subsystem is assigned a local controller that relies on measurements of common coupling point (PCC) and/or terminal quantities to provide accurate regulation of current or voltage components. This meets the local objective of each subsystem and contributes to the global objective of the microgrid.

In the first part of the work, a microgrid system is considered with linear loading conditions: balanced and unbalanced portions. The control is based on decomposing voltage and current quantities into positive and negative sequence components by using synchrouns reference frames. Components to be controlled are then extracted by Notch filters. These components are mathematically modelled so that future predictions can be facilitated. In grid mode of operation, current is controlled based on the per component approach. In island mode of operation, a subsystem is singled out to be controlled by a per component voltage strategy.

In the second part of this study, model predictive controllers are designed for the various converters for both linear and non-linear loading. For this purpose, multi-synchrouns reference frames are used to decompose converter and point of common coupling voltage and current quantities according to the needs of the control strategy. The cost function for each local controller extends to all components with an aim of regulating each component considered in the controls toward a set-out reference.

In the third part of this work, current components extractions under a non-ideal grid mode operation are investigated. Current components obtained from the multi-synchrouns reference frames are compared with those obtained by the current physical components theory. Several loading conditions at the point of common coupling are considered under the effect of a grid voltage that is contaminated with negative sequence fundamental and positive/negative sequence harmonic voltage components.

Results obtained throughout this study prove the feasibility of the individual component approach in providing regulation. In addition, with the obtained components, power quality improvements, in terms of negative sequence voltage content, can be easily implemented.

Access Setting

Dissertation-Open Access

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