Alternative Energy in Power Electronics

Muhammad H. Rashid

• Publisher: Butterworth-Heinemann
• Year: 2014
• ISBN:
  9780124095342
• Topic: Technology & Engineering
• Subtopic: Electrical Engineering & Telecommunications
• Index: Technology & Engineering

This new resource is a practical overview of designing, testing and troubleshooting power electronics in alternative energy systems, providing you with the most important information on how power electronics components such as inverters, controllers and batteries can play a pivotal role in the successful implementation of green energy solutions for both stand-alone and grid-connected applications. You will learn how to choose the right components for diverse systems, from utility-scale wind farms to photovoltaic panels on single residences, how to get the most out of existing systems, and how to solve the tough challenges particular to alternative energy applications. Whether you are a renewables professional who needs to understand more about how power electronics impact energy output, or a power engineer who is interested in learning what new avenues the alternative energy revolution is opening for your work, start here with advice and explanations from the experts, including equations, diagrams and tables designed to help you understand and succeed.

• Provides a thorough overview of the key technologies, methods and challenges for implementing power electronics in alternative energy systems for optimal power generation
• Includes hard-to-find information on how to apply converters, inverters, batteries, controllers and more for stand-alone and grid-connected systems
• Covers wind and solar applications, as well as ocean and geothermal energy, hybrid systems and fuel cells

Chapter 1

Power Electronics for Renewable Energy Sources

C.V. Nayar; S.M. Islam; H. Dehbonei; K. Tan Department of Electrical and Computer Engineering, Curtin University of Technology, Perth, Western Australia, Australia

H. Sharma Research Institute for Sustainable Energy, Murdoch University, Perth, Western Australia, Australia

Abstract

This chapter focuses on solar photovoltaic and wind power. Stand-alone PV energy system requires storage to meet the energy demand during periods of low solar irradiation and nighttime. Blocking diodes in series with PV modules are used to prevent the batteries from being discharged through the PV cells at night when there is no sun available to generate energy. Two of the main factors that have been identified as limiting criteria for the cycle life of batteries in PV power systems are incomplete charging and prolonged operation at a low state of charge. The power output of the PV array is sampled at an every definite sampling period and compared with the previous value. Voltage source inverters are usually used in stand-alone applications. They can be single phase or three phase. There are three switching techniques commonly used: square wave, quasi-square wave, and pulse width modulation. Centrifugal pumps are used for low-head applications especially if they are directly interfaced with the solar panels. Centrifugal pumps are designed for fixed-head applications and the pressure difference generated increases in relation to the speed of pump.

Keywords

Power electronics

Renewable energy sources

Photovoltaics

Wind

Solar

Chapter Outline

1.1 Introduction 2

1.2 Power Electronics for Photovoltaic Power Systems 3

1.2.1 Basics of Photovoltaics 3

1.2.2 Types of PV Power Systems 6

1.2.3 Stand-alone PV Systems 9

1.2.3.1 Battery Charging 9

1.2.3.2 Inverters for Stand-alone PV Systems 15

1.2.3.3 Solar Water Pumping 18

1.2.4 Hybrid Energy Systems 25

1.2.4.1 Series Configuration 26

1.2.4.2 Switched Configuration 27

1.2.4.3 Parallel Configuration 28

1.2.4.4 Control of Hybrid Energy Systems 30

1.2.5 Grid-connected PV Systems 32

1.2.5.1 Inverters for Grid-connected Applications 33

1.2.5.2 Inverter Classifications 33

1.2.5.3 Inverter Types 34

1.2.5.4 Power Control through PV Inverters 40

1.2.5.5 System Configurations 45

1.2.5.6 Grid-compatible Inverters Characteristics 47

1.3 Power Electronics for Wind Power Systems 49

1.3.1 Basics of Wind Power 51

1.3.1.1 Types of Wind Turbines 53

1.3.1.2 Types of Wind Generators 54

1.3.2 Types of Wind Power Systems 58

1.3.3 Stand-alone Wind Power Systems 58

1.3.3.1 Battery Charging with Stand-alone Wind Energy System 58

1.3.3.2 Wind Turbine Charge Controller 58

1.3.4 Wind-diesel Hybrid Systems 59

1.3.5 Grid-connected Wind Energy Systems 60

1.3.5.1 Soft Starters for Induction Generators 61

1.3.6 Control of Wind Turbines 62

1.3.6.1 Fixed Speed Wind Turbines 62

1.3.6.2 Variable Speed Wind Turbines 65

1.3.6.3 Discretely Variable Speed Systems 66

1.3.6.4 Continuously Variable Speed Systems 67

1.3.6.5 Types of Generator Options for Variable Speed Wind Turbines Using Power Electronics 70

1.3.6.6 Isolated Grid Supply System with Multiple Wind Turbines 73

1.3.6.7 Power Electronics Technology Development 74

References 75

1.1 Introduction

The Kyoto agreement on global reduction of greenhouse gas emissions has prompted renewed interest in renewable energy systems worldwide. Many renewable energy technologies today are well developed, reliable, and cost competitive with the conventional fuel generators. The cost of renewable energy technologies is on a falling trend and is expected to fall further as demand and production increases. There are many renewable energy sources (RES) such as biomass, solar, wind, mini hydro and tidal power. However, solar and wind energy systems make use of advanced power electronics technologies and, therefore the focus in this chapter will be on solar photovoltaic and wind power.

One of the advantages offered by (RES) is their potential to provide sustainable electricity in areas not served by the conventional power grid. The growing market for renewable energy technologies has resulted in a rapid growth in the need of power electronics. Most of the renewable energy technologies produce DC power and hence power electronics and control equipment are required to convert the DC into AC power.

Inverters are used to convert DC to AC. There are two types of inverters: (a) stand-alone or (b) grid-connected. Both types have several similarities but are different in terms of control functions. A stand-alone inverter is used in off-grid applications with battery storage. With back-up diesel generators (such as photovoltaic (PV)/diesel/hybrid power systems), the inverters may have additional control functions such as operating in parallel with diesel generators and bi-directional operation (battery charging and inverting). Grid interactive inverters must follow the voltage and frequency characteristics of the utility generated power presented on the distribution line. For both types of inverters, the conversion efficiency is a very important consideration. Details of standalone and grid-connected inverters for PV and wind applications are discussed in this chapter.

Section 1.2 covers stand-alone PV system applications such as battery charging and water pumping for remote areas. This section also discusses power electronic converters suitable for PV-diesel hybrid systems and grid-connected PV for rooftop and large-scale applications. Of all the renewable energy options, the wind turbine technology is maturing very fast. A marked rise in installed wind power capacity has been noticed worldwide in the last decade. Per unit generation cost of wind power is now quite comparable with the conventional generation. Wind turbine generators are used in stand-alone battery charging applications, in combination with fossil fuel generators as part of hybrid systems and as grid-connected systems. As a result of advancements in blade design, generators, power electronics, and control systems, it has been possible to increase drama...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Contributors
• Preface
• Chapter 1: Power Electronics for Renewable Energy Sources
• Chapter 2: Energy Sources
• Chapter 3: Photovoltaic System Conversion
• Chapter 4: Wind Turbine Applications
• Chapter 5: High-Frequency-Link Power-Conversion Systems for Next-Generation Smart and Micro Grid
• Chapter 6: Energy Storage
• Chapter 7: Electric Power Transmission
• Index