Preface

**Section 2 Assessment, Reliability and Prospects of Wind Turbines 101**

Chapter 6 **Evaluation and Stability Analysis of Onshore Wind Turbine**

Chikako Fujiyama, Yasuhiro Koda and Noriaki Sento

Satya Kiran Raju Alluri, Devender Gujjula, Krishnaveni B, Dhinesh Ganapathi, S.V.S. Phanikumar, M.V. Ramanamurthy and M.A.

Chapter 7 **Estimation Method to Achieve a Noise Reduction Effect of Airfoil with a Serrated Trailing Edge for Wind**

**Supporting Structures 103**

Jaeha Ryi and Jong-Soo Choi

Chapter 8 **Offshore Wind Feasibility Study in India 147**

Chapter 9 **Reliability Analysis of Wind Turbines 169**

Caichao Zhu and Yao Li

**Turbine Rotor 121**

Atmanand

**VI** Contents

This book contains three sections. Section 1 Stability Control and Reliable Performance of Wind Turbines – Modelling, Stability, and Control of Wind Turbines and Section 2 Stability Control and Reliable Performance of Wind Turbines – Assessment, Reliability and Prospects of Wind Turbines. Many authors with sound academic and industrial experience in the field of wind turbine technology have contributed to this book, which it is hoped will foster the knowledge and information for engineering applications, academia, and industries.

Section 1 contains five chapters. Chapter 1 gives an introduction to the book by exploring the current state of the art of wind turbine technology. This chapter covers the following: renewable energy, overview of wind energy and wind turbine technology, types of wind turbine, wind turbines and the operational grid requirements (grid codes) for stability con‐ trol, structure of wind turbines, onshore and offshore wind farms, global wind turbine in‐ stallation capacity, and wind turbine manufacturers and market trends. Chapter 2 describes power oscillation inter-area damping considering a permanent magnet synchronous genera‐ tor (PMSG) wind turbine. Different buses of the IEEE-30 model were connected to the PMSG, with a scenario that an H-infinity design controller is proposed to regulate the power variations of the grid network. The chapter presents the effectiveness of a wind generator in enhancing the damping of the system. In Chapter 3, the impact of power quality and system stability in the penetration of renewable energy sources in a distribution network is investi‐ gated. Shortcomings relating to the quality and reliability of the electric power fed into a grid-connected network will be analyzed based on grid requirements. The chapter further states that the presence of renewable energy sources modifies the short-circuit fault level in a grid-connected system, and thus the ability of protective apparatus in the distribution net‐ work will be affected. The integration of a wind farm system on the Libyan distribution net‐ work, considering various penetration conditions, is analyzed technically to understand the impact on the power quality and voltage profile of the system. The exact model of the wind turbines is uncertain, and because of this wind turbines are classed as nonlinear complex systems. Consequently, there are challenges in controlling this system, since many wind tur‐ bines work in extreme weather conditions. Chapter 4 presents a Mu robust controller in wind turbines in severe cold weather conditions. In this chapter, the wind turbine blades are assumed to be iced, thereby making the model unreliable. A robust controller is proposed to control the pitch angle of the wind turbine. Chapter 5 presents a dual robust control strategy for doubly fed induction generator (DFIG) grid-connected wind turbines attending to unbal‐ anced grid conditions. In this chapter, the low-voltage ride-through (LVRT) capability of the DFIG wind generator is investigated using hardware and software solutions. A low-cost ef‐ fective LVRT scheme based on the dual sequence decomposition technique and Lyapunovbased robust control theory is proposed. The salient benefit of this proposed scheme is that it effectively removes oscillations of active and reactive power exchanged between the gen‐ erator and the grid, in addition to symmetrical and sinusoidal grid current injection. Thus, the proposed scheme will reduce torque, stator power, and current pulsations compared to the traditional vector control strategy of the single control scheme.

Section 2 has four chapters. Evaluation and stability analysis of onshore wind turbine sup‐ porting structures is presented in Chapter 6. The findings of the effect of stability of a sup‐ porting structure on onshore wind turbine foundations considering field measurements, finite element analysis, and laboratory validations are presented in this chapter. The models considered employ three-dimensional nonlinear finite element analyses for examining the damage processes of reaching failure and the limited state of foundations that are individu‐ ally based on the fatigue limit state of the concrete. As a result, assessment of the existing structure will consider the stress number of cycle diagram obtained from experiment and analysis, respectively. In Chapter 7, an estimation method is proposed to obtain a noise re‐ duction effect from an airfoil with a serrated trailing edge for a wind turbine rotor. A wind tunnel experiment is used to investigate the changes in the aerodynamic performance of a wind turbine caused by a two-dimensional airfoil with a serrated trailing edge designed to mitigate noise from the rotor blade of the turbine. The study in this chapter was carried out based on Howe's theory, which is a key theory of the study of noise reduction effects ema‐ nating from a serrated trailing edge. An empirical noise prediction formula that changes the boundary layer thickness of a two-dimensional airfoil is proposed. The use of offshore wind energy is on the rise, because more energy can be extracted from offshore winds than on‐ shore winds. Chapter 8 presents an offshore wind feasibility study in India. Offshore wind provides a scalable alternative to conventional resources. This chapter provides an insight into the Ministry of Earth Science's various activities for offshore wind power realization in India. The assessment results in this chapter show high offshore potential areas, levelized cost of electricity, and internal rate of return on investment. The port facilities along the Gu‐ jarat and Tamil Nadul coastline are assessed and the methodology of the installation is de‐ veloped based on marine spread along the Indian coast. With the rapid development of the wind power industry, it is imperative to research the reliability of wind turbines. In Chapter 9, the failure models and research progress of wind turbine reliability is analyzed. The chap‐ ter emphasizes a number of failure modes, failure causes, and detection methods of some key components in wind turbines. Furthermore, some frequently used approaches to relia‐ bility analysis and wind turbine reliability research status are analyzed. The chapter also covers methods and measures to improve wind turbine reliability, condition monitoring and assessment process, supervisory control, and data acquisition, respectively. The chapter rec‐ ommends that it is paramount to mitigate the cost of operation and maintenance and im‐ prove the safety of wind turbines.

#### **Dr. Kenneth Eloghene Okedu**

**Section 1**

**Modelling, Stability, and Control of Wind**

**Turbines**

National University of Science and Technology (Glasgow Caledonian University) Muscat, Oman **Modelling, Stability, and Control of Wind Turbines**

it effectively removes oscillations of active and reactive power exchanged between the gen‐ erator and the grid, in addition to symmetrical and sinusoidal grid current injection. Thus, the proposed scheme will reduce torque, stator power, and current pulsations compared to

Section 2 has four chapters. Evaluation and stability analysis of onshore wind turbine sup‐ porting structures is presented in Chapter 6. The findings of the effect of stability of a sup‐ porting structure on onshore wind turbine foundations considering field measurements, finite element analysis, and laboratory validations are presented in this chapter. The models considered employ three-dimensional nonlinear finite element analyses for examining the damage processes of reaching failure and the limited state of foundations that are individu‐ ally based on the fatigue limit state of the concrete. As a result, assessment of the existing structure will consider the stress number of cycle diagram obtained from experiment and analysis, respectively. In Chapter 7, an estimation method is proposed to obtain a noise re‐ duction effect from an airfoil with a serrated trailing edge for a wind turbine rotor. A wind tunnel experiment is used to investigate the changes in the aerodynamic performance of a wind turbine caused by a two-dimensional airfoil with a serrated trailing edge designed to mitigate noise from the rotor blade of the turbine. The study in this chapter was carried out based on Howe's theory, which is a key theory of the study of noise reduction effects ema‐ nating from a serrated trailing edge. An empirical noise prediction formula that changes the boundary layer thickness of a two-dimensional airfoil is proposed. The use of offshore wind energy is on the rise, because more energy can be extracted from offshore winds than on‐ shore winds. Chapter 8 presents an offshore wind feasibility study in India. Offshore wind provides a scalable alternative to conventional resources. This chapter provides an insight into the Ministry of Earth Science's various activities for offshore wind power realization in India. The assessment results in this chapter show high offshore potential areas, levelized cost of electricity, and internal rate of return on investment. The port facilities along the Gu‐ jarat and Tamil Nadul coastline are assessed and the methodology of the installation is de‐ veloped based on marine spread along the Indian coast. With the rapid development of the wind power industry, it is imperative to research the reliability of wind turbines. In Chapter 9, the failure models and research progress of wind turbine reliability is analyzed. The chap‐ ter emphasizes a number of failure modes, failure causes, and detection methods of some key components in wind turbines. Furthermore, some frequently used approaches to relia‐ bility analysis and wind turbine reliability research status are analyzed. The chapter also covers methods and measures to improve wind turbine reliability, condition monitoring and assessment process, supervisory control, and data acquisition, respectively. The chapter rec‐ ommends that it is paramount to mitigate the cost of operation and maintenance and im‐

**Dr. Kenneth Eloghene Okedu**

Muscat, Oman

National University of Science and Technology (Glasgow Caledonian University)

the traditional vector control strategy of the single control scheme.

VIII Preface

prove the safety of wind turbines.

**Chapter 1**

**Provisional chapter**

**Introductory Chapter: Stability Control and Reliable**

**Introductory Chapter: Stability Control and Reliable** 

Energy is essential for the growth and socio-economic development of any economy. Recently, the use of renewable energy sources for energy generation is on the raise. Wind energy is one of the renewable energy sources that is indigenous in nature and could help in mitigating fossil fuels dependency [1]. Presently, about 87% of total energy in the world is obtained from traditional fossil fuels (coal, oil and natural gas), while 6% is obtained from nuclear plants and the remaining 7% is generated from renewable sources (especially hydropower, wind and solar) [2]. Unfortunately, the amounts of fossil fuel and nuclear power resources are limited. Based on the current estimates given in the literature, natural uranium used for nuclear power technology will last only about 50 years; oil, no more than 100 years; natural gas, 150 years;

Due to the fact that fossil and nuclear fuels are highly depended upon for energy generation, there are environmental pollution and safety challenges, which are now becoming dominant issues in the society and international world. Recently, there was a Paris climate agreement in France. "The agreement is within the United Nations Framework Convention on Climate Change (UNFCCC), dealing with greenhouse gas emissions mitigation, adaptation and finance, commencing in the year 2020" [3, 4]. The terms of the agreement was deliberated by 196 representatives during the 21st Conference of the UNFCCC in Paris and on December 12, 2015, it was adopted by consensus. The world is drastically focusing on clean and safe renewable energy sources due to the effects of environmental pollution on global warming. In the

long run, the resulting change of climate has disastrous consequences on the planet.

There are enormous resources of wind energy, and it has been estimated in the literature that if 10% of the wind energy could be barely tapped, the electricity needs of the world could be

> © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

DOI: 10.5772/intechopen.80237

**Performance of Wind Turbines**

**Performance of Wind Turbines**

Additional information is available at the end of the chapter

Kenneth Eloghene OkeduAdditional information is available at the end of the chapter

Kenneth Eloghene Okedu

http://dx.doi.org/10.5772/intechopen.80237

**1. Renewable energy sources**

and coal, 200 years.

#### **Introductory Chapter: Stability Control and Reliable Performance of Wind Turbines Introductory Chapter: Stability Control and Reliable Performance of Wind Turbines**

DOI: 10.5772/intechopen.80237

Kenneth Eloghene Okedu Kenneth Eloghene Okedu

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.80237
