Contents

**Preface XI**


Chapter 4 **Designing Mu Robust Controller in Wind Turbine in Cold Weather Conditions 59** Tahere Pourseif, Majid Taheri Andani, Hamed Pourgharibshahi, Hassan Zeynali and Arash Shams

Chapter 5 **Dual Robust Control of Grid-Connected DFIGs-Based Wind-Turbine-Systems under Unbalanced Grid Voltage Conditions 81** Kamel Djamel Eddine Kerrouche, Lina Wang, Alex Van Den Bossche, Azzedine Draou, Abdelkader Mezouar and Larbi Boumediene

#### **X** Contents


Preface

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

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

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