DFIG-based Wind Power Conversion System Connected to Grid

Table of Contents

CHAPTER 1: INTRODUCTION

1.1 GENERAL

1.2 BACKGROUND

1.3 WIND ENERGY

1.4 STATE OF ART

1.4.1 Classification of Wind Turbine

1.4.2 Types of Wind Generators

1.5 DOUBLY-FED INDUCTION GENERATOR

1.5.1 Advantages of DFIGs

1.6 POWER CONVERTERS

1.7 ENERGY STORAGE SYSTEMS

1.7.1 Advantages of ESS

1.7.2 Types of ESS

1.8 BUCK-BOOST CONVERTER

1.8.1 Main Advantage of Buck-Boost Converter

1.9 POWER SYSTEM INTERCONNECTION

1.9.1 Transformer

1.9.2 Advantages of Transformer in Rotor Circuit of DFIG

1.10 WIND POWER CHALLENGES

1.11 TECHNICAL CHALLENGES

1.12 PROBLEM FORMULATION AND METHODOLOGY

1.13 OUTLINE OF THESIS

CHAPTER 2: LITERATURE REVIEW

2.1 GENERAL

2.2 LITERATURE REVIEW

CHAPTER 3: MODDELING, OPERATION AND CONTROL OF DFIG

3.1 GENERAL

3.1.1 DFIG Based Wind Energy Conversion System

3.1.2 Steady-State Equivalent Circuit

3.2 REACTIVE POWER CONTROL

3.2.1 Reactive Power Sources

3.2.2 Optimum Reactive Power Distribution

3.3 TRANSIENT MODELS AND CONTROL OF DFIG

3.3.1 Power Converter Controls

3.3.1.1 Rotor Side Converter Control

3.3.1.2 Current Regulator Control

3.3.2. Grid Side Converter Control

3.3.2.1 The Simulink Model of Current Regulator Control and Dc Voltage Regulator

3.4 SPEED CONTROL

3.5 AC VOLTAGE REGULATION

3.6. DECOUPLED CONTROL OF ACTIVE AND REACTIVE POWERS

3.7 CONCLUSIONS

CHAPTER 4: INTERCONNECTION OF DFIG WITH DIFFERENT SUB-SYSTEMS

4.1 INTEGRATION OF ENERGY STORAGE SUB-SYSTEM

4.1.1 Energy Storage Sub-System

4.1.2 DFIG with Energy Storage Sub-System

4.1.3Simulink Based Model of DFIG with Battery Energy Storage Sub-System

4.1.4 Energy Storage Control

4.1.5 Grid Side Converter

4.1.6 Energy Storage System Characteristics

4.1.6.1 Operating Characteristics at Constant Wind Speed

4.1.6.2 Operating Characteristics at Variable Wind Speed

4.2 DFIG WITH BUCK/BOOST CONVERTOR

4.2.1 Series Compensation Concept

4.2.2 Buck and Boost Mode

4.2.3Simulink Based Model of DFIG with Buck-Boost Converter Sub- System

4.2.3.1 Buck-Boost Converter Control

4.2.4 Buck-Boost Converter Characteristics

4.2.4.1 Operating Characteristics at Constant Wind Speed

4.2.4.2 Operating Characteristics at Variable Wind Speeds

4.3 DFIG WITH TRANSFORMER IN ROTOR SIDE CIRCUIT

4.3.1 Simulink Based Model of DFIG with Transformer in Between Machine and Rotor Side Converter

4.3.2 Transformer Characteristics

4.3.2.1 Operating Characteristics at Constant Wind Speed

4.3.2.2 OPERATING CHARACTERISTICS AT VARIABLE WIND SPEEDS

4.4 DFIG WITH 3-WINDING TRANSFORMER

4.4.1 Simulink Model of DFIG with 3-winding Transformer

4.4.2 3-Winding Transformer Characteristics

4.4.2.1 Operating Characteristics at Constant Wind Speed

4.4.2.2 OPERATING CHARACTERISTICS AT VARIABLE WIND SPEEDS

4.4 CONCLUSIONS

CHAPTER 5: INTERCONNECTION OF DFIGS WITH GRID

5.1 GENERAL

5.2 INTERCONNECTION OF DFIGS

5.3 NORMAL WIND FARM OPERATION

5.3.1 Real Power Flow

5.3.2 Voltage Regulation

5.4 ANALYSIS OF TOTAL HARMONIC DISTORTION

5.5 EFFICIENCY OF DFIG WITH DIFFERENT SUB-SYSTEMS

5.6 CONCLUSIONS

CHAPTER 6: SUMMARY, CONCLUSIONS AND FUTURE WORK

6.1 SUMMARY AND CONCLUSION

6.2 FUTURE WORK

Objectives and Research Scope

This thesis aims to develop and verify a simplified electromechanical model of a Doubly Fed Induction Generator (DFIG) to analyze its performance under transient and short-term voltage stability conditions, while exploring various grid-support configurations to enhance power efficiency and reduce harmonic distortion.

• Electromechanical modeling of DFIG in MATLAB/SIMULINK environment.
• Integration of sub-systems including battery energy storage, buck-boost converters, and specialized transformers.
• Analysis of grid support capabilities through active and reactive power control under constant and variable wind speeds.
• Evaluation of Total Harmonic Distortion (THD) and system efficiency across different DFIG configurations.

Excerpt from the Book

Summary of Chapters

CHAPTER 1: INTRODUCTION: This chapter introduces the growing necessity of wind energy, its background, and the research objectives regarding DFIG-based systems.

CHAPTER 2: LITERATURE REVIEW: This chapter provides an up-to-date survey of research papers and existing techniques concerning DFIG modeling and control strategies.

CHAPTER 3: MODDELING, OPERATION AND CONTROL OF DFIG: This chapter details the steady-state modeling, transient control algorithms, and reactive power control strategies for the DFIG system.

CHAPTER 4: INTERCONNECTION OF DFIG WITH DIFFERENT SUB-SYSTEMS: This chapter evaluates the performance of the DFIG when integrated with battery storage, buck-boost converters, and various transformer configurations.

CHAPTER 5: INTERCONNECTION OF DFIGS WITH GRID: This chapter analyzes the impact of the DFIG system on grid stability and presents a comparative harmonic distortion and efficiency analysis.

CHAPTER 6: SUMMARY, CONCLUSIONS AND FUTURE WORK: This chapter synthesizes the research findings and outlines potential future improvements, such as cost reduction and optimized voltage regulation control.

Keywords

Doubly-Fed Induction Generator, DFIG, Wind Energy Conversion System, WECS, Battery Energy Storage System, BESS, Buck-Boost Converter, Grid Interconnection, Reactive Power Control, Total Harmonic Distortion, THD, Power Efficiency, MATLAB, SIMULINK, Voltage Regulation.

Frequently Asked Questions

What is the primary focus of this thesis?

The thesis focuses on modeling and analyzing the Doubly Fed Induction Generator (DFIG) to improve grid stability and power quality using various sub-systems such as battery storage and custom transformer configurations.

What are the key thematic areas?

The study covers DFIG modeling, control algorithms, reactive power management, harmonic distortion analysis, and system integration strategies for wind farms.

What is the core objective of the research?

The primary goal is to develop a simplified DFIG model in MATLAB/SIMULINK to study how the generator can provide grid support through precise control of active and reactive power.

Which scientific methodology is utilized?

The researcher employs numerical simulation using MATLAB/SIMULINK to build electromechanical models, perform harmonic analysis via FFT tools, and evaluate performance under variable wind conditions.

What topics are discussed in the main body of the text?

The main body examines steady-state and transient models, control structures for rotor and grid side converters, and the comparative performance of various integration techniques like buck-boost converters and 3-winding transformers.

Which keywords define this work?

The work is characterized by terms such as DFIG, WECS, BESS, Harmonic Distortion, Reactive Power Control, and Grid Interconnection.

How does the buck-boost converter affect the DFIG performance?

The buck-boost converter is used to manage DC-link voltage fluctuations, improving the system's ability to dispatch power and regulating output more effectively than a standard configuration.

Why is the 3-winding transformer highlighted in the results?

The research concludes that the DFIG with a 3-winding transformer achieves high efficiency (above 93%) and effective harmonic management compared to other tested sub-systems, despite the higher cost of implementation.