Wind Energy Systems: Control Engineering Design (Hardback) book cover

Wind Energy Systems

Control Engineering Design

By Mario Garcia-Sanz, Constantine H. Houpis

© 2012 – CRC Press

631 pages | 375 B/W Illus.

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Hardback: 9781439821794
pub: 2012-02-02
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Presenting the latest developments in the field, Wind Energy Systems: Control Engineering Design offers a novel take on advanced control engineering design techniques for wind turbine applications. The book introduces concurrent quantitative engineering techniques for the design of highly efficient and reliable controllers, which can be used to solve the most critical problems of multi-megawatt wind energy systems.

This book is based on the authors’ experience during the last two decades designing commercial multi-megawatt wind turbines and control systems for industry leaders, including NASA and the European Space Agency. This work is their response to the urgent need for a truly reliable concurrent engineering methodology for the design of advanced control systems. Outlining a roadmap for such a coordinated architecture, the authors consider the links between all aspects of a multi-megawatt wind energy project, in which the wind turbine and the control system must be cooperatively designed to achieve an optimized, reliable, and successful system.

Look inside for information about the QFT Control Toolbox for Matlab, the software developed by the author to facilitate the QFT robust control design (see also the link at

The textbook’s big-picture insights can help students and practicing engineers control and optimize a wind energy system, in which large, flexible, aerodynamic structures are connected to a demanding variable electrical grid and work automatically under very turbulent and unpredictable environmental conditions. The book covers topics including robust QFT control, aerodynamics, mechanical and electrical dynamic modeling, economics, reliability, and efficiency. It also addresses standards, certification, implementation, grid integration, and power quality, as well as environmental and maintenance issues.

To reinforce understanding, the authors present real examples of experimentation with commercial multi-megawatt direct-drive wind turbines, as well as on-shore, offshore, floating, and airborne wind turbine applications. They also offer a unique in-depth exploration of the quantitative feedback theory (QFT)—a proven, successful robust control technique for real-world applications—as well as advanced switching control techniques that help engineers exceed classical linear limitations.


Garcia-Sanz and Houpis, who both have extensive expertise in major projects in North America and Europe, describe the latest science and technology in wind turbines … . The text includes a link to a free download for the CAD tool they utilize …

—SciTech News, Vol. 66, September 2012

Table of Contents


Broad Context and Motivation

Concurrent Engineering: A Road Map for Energy

Quantitative Robust Control

Novel CAD Toolbox for QFT Controller Design


Part I: Advanced Robust Control Techniques: QFT and Nonlinear Switching

Introduction to QFT

Quantitative Feedback Theory

Why Feedback?

QFT Overview

Insight into the QFT Technique

Benefits of QFT

MISO Analog QFT Control System


QFT Method (Single-Loop MISO System)

Design Procedure Outline

Minimum-Phase System Performance Specifications

J LTI Plant Models

Plant Templates of Pι(s), P( j_i )

Nominal Plant

U-Contour (Stability Bound)

Tracking Bounds BR(jω) on the NC

Disturbance Bounds BD(jωi)

Composite Boundary Bo(jωi)

Shaping of Lo(jω)

Guidelines for Shaping Lo(jω)

Design of the Prefilter F(s)

Basic Design Procedure for a MISO System

Design Example 1

Design Example 2

Template Generation for Unstable Plants

Discrete Quantitative Feedback Technique


Bilinear Transformations

Non-Minimum-Phase Analog Plant

Discrete MISO Model with Plant Uncertainty

QFT w-Domain DIG Design


Basic Design Procedure for a MISO S-D Control System

QFT Technique Applied to the PCT System

Applicability of Design Technique to Other Plants

Designing L(w) Directly

Diagonal MIMO QFT


Examples and Motivation

MIMO Systems—Characteristics and Overview

MIMO QFT Control—Overview

Nonsequential Diagonal MIMO QFT (Method 1)

Sequential Diagonal MIMO QFT (Method 2)

Basically Noninteracting Loops

MIMO QFT with External (Input) Disturbances

Non-Diagonal MIMO QFT


Non-Diagonal MIMO QFT: A Coupling Minimization Technique (Method 3)

Coupling Elements

Optimum Non-Diagonal Compensator

Coupling Effects

Quality Function of the Designed Compensator

Design Methodology

Some Practical Issues

Non-Diagonal MIMO QFT: A Generalized Technique (Method 4)


Translating Matrix Performance Specifications

Comparison of Methods 3 and 4

QFT for Distributed Parameter Systems



Generalized DPS Control System Structure

Extension of Quantitative Feedback Theory to DPS

Modeling Approaches for PDE


Nonlinear Switching Control Techniques


System Stability under Switching



Part II: Wind Turbine Control

Introduction to Wind Energy Systems


Birth of Modern Wind Turbines

Market Sizes and Investments

Future Challenges and Opportunities

Standards and Certification for Wind Turbines


Standards: Definition and Strategic Value

Standards: Structure and Development

Certification of Wind Turbines

General Concepts

Wind Turbine Control Objectives and Strategies


Control Objectives

Control Strategies

Control System

Aerodynamics and Mechanical Modeling of Wind Turbines


Aerodynamic Models

Mechanical Models

Electrical Modeling of Wind Turbines


Electrical Models

Power Electronic Converters

Power Quality Characteristics

Wind Farms Integration in the Power System

Advanced Pitch Control System Design


QFT Robust Control Design

Nonlinear Switching Multi-Objective Design

Nonlinear Robust Control Design for Large Parameter Variation

Experimental Results with the Direct-Drive Wind Turbine TWT-1.65


Variable-Speed Direct-Drive Torres Wind Turbine Family

Torres Wind Turbine Pitch and Rotor Speed Control Results

Wind Farm Grid Integration: Torres Wind Turbine Results

Voltage Dip Solutions: Torres Wind Turbine Results

Blades Manufacturing: MIMO QFT Control for Industrial Furnaces


Composite Materials

Industrial Furnace Description

Furnace Model

Estimation of Furnace Parameters

MIMO QFT Controller Design

Experimental Results

Smart Wind Turbine Blades


General Description

Some History

Offshore Wind Energy: Overview


History of Offshore Platforms

Offshore Wind Farms

Offshore Floating Wind Turbines

Airborne Wind Energy Systems


Overview of Airborne Wind Energy Systems

Eagle System

Appendix A: Templates Generation

Appendix B: Inequality Bound Expressions

Appendix C: Analytical QFT Bounds

Appendix D: Essentials for Loop Shaping

Appendix E: Fragility Analysis with QFT

Appendix F: QFT Control Toolbox: User’s Guide

Appendix G: Controller Design Examples

Appendix H: Conversion of Units


Answers to Selected Problems



About the Authors

Dr. Mario García-Sanz is Professor at Case Western Reserve University (CWRU), Ohio, the Milton and Tamar Maltz Professor in Energy Innovation, and Director of the Wind Energy and Control Systems Center at CWRU. As Senior Advisor for the President of the M.Torres Group and Professor at the Public University of Navarra, he played a central role in the design and field experimentation of advanced multi-megawatt wind turbines for industry. Dr. García-Sanz held visiting professorships at the Control Systems Centre, UMIST (UK, 1995); at Oxford University (UK, 1996); at the Jet Propulsion Laboratory NASA-JPL (California, 2004); and at the European Space Agency ESA-ESTEC (The Netherlands, 2008).

He holds 20 industrial patents, has done more than 40 large research projects for industry and space agencies, and is author or coauthor of more than 150 research papers, including the books “Quantitative Feedback Theory: Theory and Applications”, Taylor & Francis (2006), and “Wind Energy Systems: Control Engineering Design”, Taylor & Francis (2012).

Dr. García-Sanz is Subject Editor of the International Journal of Robust and Nonlinear Control, a member of IFAC and IEEE Technical Committees, and served as NATO/RTO Lecture Series Director and as Guest Editor of international journals (Robust control, QFT control, Wind turbine control, Spacecraft control). He was awarded the IEE Heaviside Prize (UK) in 1995 and the BBVA research award (Spain) in 2001. Professor García-Sanz's main research interest focuses on bridging the gap between advanced control theory and applications, with special emphasis in Energy Innovation, Wind Energy, Space, Environmental and Industrial Applications.

Subject Categories

BISAC Subject Codes/Headings:
TECHNOLOGY & ENGINEERING / Power Resources / Alternative & Renewable
TECHNOLOGY & ENGINEERING / Power Resources / Electrical