Control of a DC Microgrid

Master thesis (2018)

Authors

S. Sakkas Electrical Engineering, Mathematics and Computer Science

Contributors

P. Bauer (graduation committee member)
José L. Rueda (graduation committee member)
Faculty
Electrical Engineering, Mathematics and Computer Science, Electrical Engineering, Mathematics and Computer Science
Copyright: © 2018 Sotiris Sakkas
More Info
expand_more

Published Date

27-11-2018

Language

English

Reuse Rights

Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.

Faculty

Electrical Engineering, Mathematics and Computer Science

Abstract

The growth of distributed Renewable Energy share in the total electricity production as wells as technological advancements in power electronics and increase of DC loads, point towards the development of the DC microgrid (DCMG) concept as a valid model for future energy systems especially for operations and locations where the existing grid cannot satisfy.
A DC microgrid consist of distributed sources, load and storage connected to a DC bus through converters. The two main issues in a DCMG operation is the power balance between supply and demand and its implementation through the interfacing converters, who in turn must be able to facilitate these operations. Many grid control strategies can be used but whatever the strategy may be, control is achieved through regulation of the DC bus voltage.
In this thesis a decentralized primary controller is selected, analyzed and modelled for power balance operations in an islanded 48V-LVDC microgrid, consisting of a renewable energy source, an electronic load and storage capability. Control is achieved through dc bus voltage monitoring and control operations on the interfacing converters, based on predefined voltage set points. As an interfacing converter, a cascaded half bridge buck and boost converter is used and controlled. Two different control modes are implemented: buck operation for the start-up of the grid and a special constant frequency modulation for soft switching and increased efficiency of the converter.
Furthermore, its use as multi-purpose converter, its low level control schemes and the co-operation with the high-grid level control are studied. Physical switching models are used to account for the real operation of the converter, when operating under higher level control, aiming at grid stability and optimal power flow.