Conceptual survey of Generators and Power Electronics for Wind Turbines
Conceptual survey of Generators andPower Electronics for Wind Turbines L. H. Hansen, L. Helle, F. Blaabjerg, E. Ritchie, S. Munk-Nielsen, H. Bindner, P. Sørensen and B. Bak-Jensen. Risø National Laboratory, Roskilde, DenmarkDecember 2001Abstract
This report presents a survey on generator concepts and power electronic con-cepts for wind turbines. The report is aimed as a tool for decision-makers anddevelopment people with respect to wind turbine manufactures, utilities, and in-dependent system operators as well as manufactures of generators and power electronics. The survey is focused on the electric development of wind turbines and it yields an overview on: ·
State of the art on generators and power electronics.·
Future concepts and technologies within generators and power electron-ics.·
Market needs in the shape of requirements to the grid connection.This survey on generator and power electronic concepts was carried out in co-operation between Aalborg University and Risø National Laboratory, in thescope of the joint research programme Electric Design and Control.The report has been reviewed by:
__________________Anca Daniela Hansen ISBN 87-550-2743-1 ISBN 87-550-2745-8 (Internet)ISSN 0106-2840
_________________ Peter Hauge Madsen
Print: Pitney Bowes Management Services Denmark, 2002
Preface The present report is a result of the co-operation between Aalborg University and Risø National Laboratory within the scope of the research programme Elec-tric Design and Control (EDS, alias Elektrisk Design og Styring). The report has as an objective to compile and disseminate some of the knowl-edge on generators and power electronics for wind turbines, which now is at EDS’ disposal. In this work, the following persons have contributed to the re-port writing: ·
Birgitte Bak-Jensen.·
Henrik Bindner.·
Frede Blaabjerg. ·
Lars Henrik Hansen.·
Lars Helle.·
Stig Munk-Nielsen.·
Ewen Ritchie.·
Poul Sørensen. In order to focus the report towards the needs of the wind turbines manufactures a task group consisting of: ·
NEG Micon: Niels Vilsbøll.·
Vestas: Michael Kinch.·
ABB: Hans Christian Christensen.·
Siemens: Kim Eskildsen and Ulf Lindhard.have been asked to contribute to this report by valuable input – in specific on the concept evaluation criteria. Moreover, ABB and Siemens have kindly putpictures and drawings at disposal for this report. Finally, the four largest wind turbine gearbox manufactures have been asked to supply specific gearbox data. The following two: ·
Brook Hansen Transmission ·
Lohmann & Solterfoht.have contributed
with data which are used to point out trends on gearboxes.Frontpage picture has been supplied by Vestas
Risø-R-1205(EN)
Contents
Preface 3
Acronyms and abbreviations 7
1 Introduction 9
1.1Report outline 9
1.2State of the art 10
1.2.1 Concepts and wind turbine configurations 11
1.2.2 Market aspects 16
1.2.3 Trends in wind turbine design 18
2 Generic Generator Types 21
2.1Criteria for Assessment of Generator Types 21
2.2The Asynchronous Machine (Induction Machine) 21
2.2.1 Squirrel Cage Induction Generator 22
2.2.2 Wound rotor Induction Generator 23
2.2.3 Principle of Operation 24
2.2.4 Methods of Analysis 24
2.2.5 Operational Characteristics – Normal Duty 24
2.2.6 Operational Characteristics – Fault Conditions 25
2.2.7 Axial Flux Induction Machines 25
2.2.8 Efficiency of Induction Generators as a Function of Load and
Speed 25
2.2.9 Well-Established or New Technology 26
2.2.10 Gear or Direct Drive Multi-pole 26
2.3The Permanent Magnet Generator 26
2.3.1 Permanent Magnet Generator 28
2.3.2 Axial Flux Machines 29
2.3.3 Hybrid Permanent Magnet machines 30
2.3.4 Methods of Analysis of PMG 31
2.3.5 Methods of loading the PMG 32
2.3.6 Design Considerations 32
2.3.7 Experimental Results 34
2.3.8 Conclusion on PMG 36
2.4The Switched Reluctance Generator 37
2.4.1 Principle of operation 38
2.4.2 Operational Characteristics – Normal Duty 38
2.4.3 Comparison with other types of machine 39
2.4.4 Axial Flux Machines 39
2.4.5 Methods for modelling and analysis 40
2.4.6 Operational Characteristics – Fault Conditions 40
2.4.7 Efficiency of the SRG as a Function of Load and Speed 40
2.4.8 Well Established or New Technology 41
2.4.9 One off Price 41
2.4.10 Gear versus Multi-pole 41
2.4.11 Other Comments 41
2.4.12 Conclusion on SRG 41
2.5The Transverse Flux machine 41
2.5.1 Reported machine type designs 42
2.5.2 TFPM technology 43
2.5.3 TFPM basic design 43
2.5.4 Force production and calculation 45
2.5.5 Flux linkage calculation 46
2.5.6 Conclusion on TFPM Machine 46
2.6The Wound Rotor Generator 46
2.6.1 Description 47
2.6.2 Operation 50
2.6.3 Conclusion on Wound Rotor Synchronous Generator 50
2.7The High Voltage Machine 50
2.8Trends and perspectives 52
3 Power Electronic Concepts 56
3.1Criteria for concept evaluation 56
3.2Power converters 56
3.2.1 Soft starter 56
3.2.2 Capacitor bank 57
3.2.3 Diode rectifier 58
3.2.4 The back-to-back PWM-VSI 58
3.2.5 Tandem converter 59
3.2.6 Matrix converter 61
3.2.7 Multilevel Converter 63
3.2.8 Resonant converter 65
3.2.9 Comparison of the five frequency converters 68
3.3Park solutions 69
3.3.1 Reactive power compensation units 69
3.3.2 Power regulation and storage units 70
3.3.3 HVDC 71
3.4Trends and perspectives 73
4 Grid Integration Issues 75
4 Grid Integration Issues 75
4.1Grid Generics and Main Focus 75
4.2Power Quality and other Demands to Grid Connection 76
4.2.1 Categorisation and characterisation of disturbances in the grid 77
4.2.2 Equipment used to enhance the Power Quality. 80
4.2.3 On/off apparatus, switches 81
4.2.4 Stepwise controllable apparatus 81
4.2.5 Continuously controllable apparatus 81
4.2.6 Measures and indicators 83
4.3Standardised Grids 86
4.3.1 Basic grid properties 86
4.3.2 Various grid types 87
4.3.3 Off-shore wind farms on the transmission grid 88
4.4Power system integration 89
5 Summary 92
References 95
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