Advanced Hierarchical Control and Stability Analysis of DC Microgrids (Springer Theses)

✍ Scribed by Andrei-Constantin Braitor

• Publisher: Springer
• Year: 2022
• Tongue: English
• Leaves: 185
• Edition: 1st ed. 2022
• Category: Library

✦ Synopsis

This book introduces several novel contributions into the current literature. Firstly, given that microgrid topologies are paramount in theoretical analysis, the author has proposed a rigorous method of computing the network’s admittance matrix and developed to facilitate the stability analysis of DC microgrids supplying nonlinear loads. This unique approach enabled the factorisation of the admittance matrix in a particular way that facilitates a rigorous theoretical analysis for deriving the stability conditions.

Secondly, author has proposed a unified control structure at the primary control layer that maintains the widely accepted droop-based approaches and additionally ensures crucial current- and voltage-limiting properties, thus offering an inherent protection to distributed energy resources. He has formalised the control design proofs using Lyapunov methods and nonlinear ultimate boundedness theory, for both parallel and meshed microgrid configurations. Moreover, he has developed a distributed secondary controller using a diffusive coupling communication network, on top of the primary control, to achieve voltage restoration and improve the power sharing. In this way, the author has formulated the complete hierarchical control scheme.

In this high-order nonlinear setting, he has analytically proven closed-loop system stability of the overall system, for the first time, using two-time scale approaches and singular perturbation theory, by formulating rigorous theorems that introduce straightforward conditions that guide the system and control design and demonstrate system stability at the desired equilibrium point. In addition, the author has provided a straightforward algorithm for simple testing of system stability and explored from a graphical perspective by giving an interpretation to the effect of the nonlinear load onto the system performance and stability.

✦ Table of Contents

Supervisor’s Foreword
Abstract
Acknowledgements
Contents
List of Figures
List of Tables
1 Introduction
1.1 General Topic and Overview
1.2 Motivation and Scope
1.2.1 Challenges
1.2.2 Aims and Objectives
1.2.3 Contribution
1.2.4 List of Publications
1.3 Thesis Outline
References
2 Literature Review
2.1 Microgrid Components
2.1.1 Power Converters
2.1.2 DC Loads
2.2 Hierarchical Control
2.2.1 Primary Control
2.2.2 Secondary Control
2.2.3 Supervisory Control
2.3 Microgrid Stability
2.3.1 Stability of Droop-Controlled DC Microgrids
2.3.2 Stability of DC Microgrids under Secondary Control
2.4 Microgrid Protection
2.4.1 Overcurrent Protection
2.4.2 Overvoltage Protection
2.5 Gaps in the Current Literature
References
3 Notations and Theoretical Preliminaries
3.1 Vector, Matrix and Function Notations
3.2 Linear Matrix Analysis
3.3 Elements of Graph Theory
3.4 Nonlinear System Analysis
References
4 Admittance Matrix Computation and Stability Analysis of Droop-Controlled DC Microgrids
4.1 DC Microgrid System Modelling
4.2 Admittance Matrix
4.3 Stability of Droop Controlled Microgrids
4.3.1 Droop Control Design
4.3.2 Stability Analysis
4.4 Simulation Results
4.5 Conclusions
References
5 Control Design and Stability Analysis of DC Microgrids Consisting of Unidirectional DC/DC Boost Converters
5.1 Paralleled DC/DC Boost Converters Feeding a CIL
5.1.1 Proposed Current-Limiting Droop Controller
5.1.2 Simulation Results
5.2 Paralleled DC/DC Boost Converters Feeding a CIL, CCL or a CPL
5.2.1 Dynamic Model
5.2.2 Proposed Controller Design
5.2.3 Stability Analysis
5.2.4 Methodology for Testing the Stability Conditions
5.2.5 Simulation Results
5.2.6 Experimental Results
5.3 Conclusions
References
6 Stability Analysis of Parallel-Operated Bidirectional AC/DC and DC/DC Converters
6.1 Bidirectional DC/DC and Three-Phase AC/DC Converters Feeding a CIL
6.1.1 Nonlinear Model of the DC Microgrid
6.1.2 Problem Description and Objectives
6.1.3 Nonlinear Control Design and Analysis
6.1.4 Simulation Results
6.2 Bidirectional DC/DC and Three-Phase AC/DC Converters Feeding a CPL
6.2.1 Dynamic Model
6.2.2 Nonlinear Control Design and Analysis
6.2.3 Stability Analysis
6.2.4 Validation of Closed-Loop System Stability
6.2.5 Simulation Results
6.2.6 Experimental Results
6.3 Conclusions
References
7 Stability Analysis of DC Microgrids Under Decentralised Primary and Distributed Secondary Control
7.1 Dynamic Modelling of the DC Microgrid
7.2 Proposed Controller Design
7.2.1 Primary Control Steady-State Analysis
7.2.2 Secondary Control Design and Analysis
7.3 Stability Analysis
7.3.1 Closed-Loop System
7.3.2 Boundary Layer Stability Analysis
7.3.3 Reduced Model
7.4 Simulation Results
7.4.1 Communication Failure
7.5 Experimental Results
7.6 Conclusions
References
8 Droop-Controlled DC Microgrids with Overvoltage Protection
8.1 Parallel Configuration DC Microgrid
8.1.1 Proposed Control Architecture
8.1.2 Stability Analysis
8.1.3 Simulation Results
8.2 Meshed DC Microgrid
8.2.1 DC Microgrid Model
8.2.2 Proposed Control Architecture
8.2.3 Stability Analysis
8.2.4 Simulation Results
8.3 Conclusions
References
9 Conclusions
9.1 Summary
9.1.1 Discussions
9.1.2 Assumptions and Limitations
9.2 Future Work
References
Appendix A Schematic of the Texas Instruments DC/DC Boost Converter
Appendix B Schematic of the Texas Instruments 3-Phase Inverters