Distributed photovoltaic grid transformers

Title:

Personal Author:

Shertukde, Hemchandra Madhusudan, author

Publication Information:

Boca Raton, F.L. : CRC Pr., 2014

Physical Description:

xix, 257 pages, 16 unnumbered pages of plates : illustrations ; 24 cm.

ISBN:

9781466505810

Abstract:

"The demand for alternative energy sources fuels the need for electric power and controls engineers to possess a practical understanding of transformers suitable for solar energy. Meeting that need, Distributed Photovoltaic Grid Transformers begins by explaining the basic theory behind transformers in the solar power arena, and then progresses to describe the development, manufacture, and sale of distributed photovoltaic (PV) grid transformers, which help boost the electric DC voltage (generally at 30 volts) harnessed by a PV panel to a higher level (generally at 115 volts or higher) once it is inverted to the AC voltage form by the inverter circuit. Packed with real-life scenarios and case studies from around the globe, Distributed Photovoltaic Grid Transformers covers the key design, operation, and maintenance aspects of transformers suitable for solar energy. Topics include islanding, voltage flicker, voltage operating range, frequency and power factor variation, and waveform distortion. Multiple homework questions are featured in each chapter. A solutions manual and downloadable content, such as illustrated examples, are available with qualifying course adoption"--provided by publisher

Subject Term:

Electric inverters

Photovoltaic power systems -- Equipment and supplies

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Library	Item Barcode	Call Number	Material Type	Item Category 1	Status
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Summary

The demand for alternative energy sources fuels the need for electric power and controls engineers to possess a practical understanding of transformers suitable for solar energy. Meeting that need, Distributed Photovoltaic Grid Transformers begins by explaining the basic theory behind transformers in the solar power arena, and then progresses to describe the development, manufacture, and sale of distributed photovoltaic (PV) grid transformers, which help boost the electric DC voltage (generally at 30 volts) harnessed by a PV panel to a higher level (generally at 115 volts or higher) once it is inverted to the AC voltage form by the inverter circuit.

Packed with real-life scenarios and case studies from around the globe, Distributed Photovoltaic Grid Transformers covers the key design, operation, and maintenance aspects of transformers suitable for solar energy. Topics include islanding, voltage flicker, voltage operating range, frequency and power factor variation, and waveform distortion. Multiple homework questions are featured in each chapter. A solutions manual and downloadable content, such as illustrated examples, are available with qualifying course adoption.

Author Notes

Hemchandra Madhusudan Shertukde holds a B.Tech from the Indian Institute of Technology Kharagpur, as well as an MS and Ph.D in electrical engineering with a specialty in controls and systems engineering from the University of Connecticut, Storrs, USA. Currently, he is professor of electrical and computer engineering for the College of Engineering, Technology, and Architecture (CETA) at University of Hartford, Connecticut, USA. He was also senior lecturer at the Yale School of Engineering and Applied Sciences (SEAS), New Haven, Connecticut, USA. The principal inventor of two commercialized patents, he has published several journal articles and written two solo books.

Dr. Shertukde is the recipient of the 2017 IEEE EAB/SA Standards Education Award, 2017 IEEE-PES CT Chapter Outstanding Engineer Award, and the 2016 IEEE Award as the Chair of the Working Group C.5.159. He continues to be in leadership positions for several other Working Groups enabling IEEE-TC to publish different standards and User's Guides for Electrical Power Transformers.

Preface	p. xv
Acknowledgments	p. xvii
The Author	p. xix
1 Introduction	p. 1
1.1 Introduction to Distributed Photovoltaic (DPV) Grid Power Transformers	p. 1
1.2 Voltage Flicker and Variation	p. 3
1.3 Harmonics and Wave Form Distortion	p. 3
1.4 Frequency Variation	p. 4
1.5 Power Factor (PF) Variation	p. 4
1.6 Safety and Protection Related to the Public	p. 4
1.7 Islanding	p. 5
1.8 Relay Protection	p. 5
1.9 DC Bias	p. 5
1.10 Thermo Cycling (Loading)	p. 6
1.11 Power Quality	p. 7
1.12 Low-Voltage Fault Ride-Through	p. 7
1.13 Power Storage	p. 7
1.14 Voltage Transients and Insulation Coordination	p. 8
1.15 Magnetic Inrush Current	p. 8
1.16 Eddy Current and Stray Losses	p. 8
1.17 Design Considerations: Inside/Outside Windings	p. 10
1.18 Special Tests Consideration	p. 10
1.19 Special Design Consideration	p. 11
1.20 Other Aspects	p. 11
1.21 Conclusions	p. 12
Bibliography	p. 12
2 Use of Distributed Photovoltaic Grid Power Transformers	p. 15
2.1 DPV-GT Solar Converter Step-Up Transformers	p. 15
2.2 Transformers for Solar Power Solutions	p. 18
2.2.1 Photovoltaic Power Plants	p. 18
2.2.2 Concentrated Solar Power	p. 19
2.2.3 PV Distribution Transformers	p. 19
2.3 Concentrated Solar Power (CSP) Transformers	p. 20
2.4 Medium Power Transformers	p. 20
2.5 Concentrated Photovoltaic (CPV) Systems Transformers	p. 21
Bibliography	p. 22
3 Voltage Flicker and Variation in Distributed Photovoltaic Grid Transformers	p. 25
3.1 Flicker	p. 25
3.2 Voltage Fluctuations	p. 26
Bibliography	p. 27
4 Harmonics and Waveform Distortion (Losses, Power Rating) in Distributed Photovoltaic Grid Transformers	p. 29
4.1 Definition of Harmonics	p. 30
4.2 Factors That Cause Harmonics	p. 35
4.3 Effects of Harmonics	p. 36
4.4 Reducing the Effects of Harmonics	p. 36
4.5 Eddy Current Loss	p. 38
4.6 K-Factor	p. 38
4.7 Summary	p. 38
4.8 Power Factor Control	p. 39
4.9 Shunt Filter	p. 39
4.10 Series Filter	p. 40
4.11 Harmonic Mitigation	p. 40
4.12 Broadband Filters	p. 42
Bibliography	p. 42
Chapter 4 Problems	p. 43
5 Frequency Variation, Power Factor Variation in Distributed Photovoltaic Grid Transformers	p. 45
5.1 Under- or Over-Frequency	p. 45
5.2 Power Factor Control	p. 45
5.3 Under-Frequency Concerns	p. 45
5.4 Over-/Under-Voltage (OVP/UVP) and Over-/Under-Frequency (OFP/UFP)	p. 46
5.5 Frequency Variation due to Electromagnetic Compatibility (EMC)	p. 47
5.6 Conducted High-Frequency Phenomena	p. 48
5.7 Frequency Problems Related to Large Grid Tied DPV-GT Impedance and PV Inverter Interaction	p. 48
5.8 Power Factor Correction (PFC)	p. 49
Bibliography	p. 50
6 Islanding Effects on Distributed Photovoltaic Grid Transformers	p. 53
6.1 EN61000-3-2 European Standard Regulating Harmonic Currents	p. 54
6.2 Scoping Consistency	p. 55
6.3 Methods for Detecting Islanding with DPV-GTs That Are Grid-Tied	p. 56
6.3.1 Over-/Under-Voltage (OVP/UVP) and Over-/Under-Frequency (OFP/UFP)	p. 56
6.3.2 Voltage-Phase Jump Detection (PJD)	p. 57
6.3.3 Detection of Voltage Harmonics	p. 58
6.3.4 Detection of Current Harmonics	p. 59
6.3.4.1 Impedance Measurement	p. 59
6.3.4.2 Detection of Impedance at a Specific Frequency	p. 60
6.3.4.3 Slip-Mode Frequency Shift (SMS)	p. 61
6.3.4.4 Frequency Bias (Active Frequency Drift or Frequency Shift Up/Down)	p. 62
6.3.4.5 Frequency Shift	p. 62
6.3.4.6 Voltage Shift (VS)	p. 62
6.3.4.7 Frequency Jump (FJ)	p. 63
6.3.4.8 ENS or MSD (Device Using Multiple Methods)	p. 63
6.3.4.9 Impedance Insertion	p. 63
6.3.4.10 Power Line Carrier Communications (PLCC)	p. 64
6.3.4.11 Supervisory Control and Data Acquisition (SCADA)	p. 65
Bibliography	p. 65
7 Relay Protection for Distributed Photovoltaic Grid Power Transformers	p. 69
7.1 Distributed Photovoltaic Grid Transformer (DPV-GT), Protection	p. 69
7.2 Application of Protective Scheme	p. 71
7.2.1 Fault Primary Backup	p. 71
7.2.2 Monitoring True Load	p. 71
7.2.3 Direct Transfer Trip (DTT) Communication Requirements	p. 71
7.3 Protection Relays	p. 71
7.4 Photovoltaic System Ground-Fault Protection	p. 72
7.4.1 Islanding Considerations	p. 73
7.4.2 Relay, Fuse, and Line Closer Methodology for Protection of DPV	p. 74
7.4.3 Impact on Fuse Saving Schemes	p. 74
Bibliography	p. 74
Chapter 7 Problems	p. 75
8 DC Bias in Distributed Photovoltaic Grid Power Transformers	p. 77
8.1 DC Injection into the Grid	p. 77
8.2 Effects of DC Currents on DPV-GTs	p. 79
Bibliography	p. 80
9 Thermocycling (Loading) and Its Effects on Distributed Photovoltaic Grid Transformers	p. 81
9.1 Gradient in Windings with No Directed Oil Flow	p. 83
9.2 Some Commercially Available Epoxy Materials and Their Advantages for DPV-GTs	p. 86
9.3 Some Commercially Available Products and Their Applications	p. 88
10 Power Quality Provided by Distributed Photovoltaic Grid Power Transformers	p. 89
10.1 Power Quality Requirements	p. 89
10.1.1 Power Conditioning	p. 92
10.1.2 Smart Grids and Power Quality	p. 92
10.1.3 Power Quality Challenges	p. 93
10.1.4 Raw Data Compression	p. 93
10.1.5 Aggregated Data Compression	p. 94
10.2 Power Quality in Grid Connected Renewable Energy Systems	p. 94
10.3 Power Quality Issues (DG)	p. 95
10.4 Grid integration of Renewable Energy Systems-Power Quality Issues A Solar Photovoltaic Systems	p. 96
10.5 Mitigation of PQ Problems	p. 97
10.6 Role of Custom Power Devices	p. 97
10.7 Effects of irradiance in a Solar Photovoltaic Systems	p. 99
References	p. 100
11 Voltage Transients and Insulation Coordination in Distributed Photovoltaic Grid Power Transformers	p. 103
11.1 Insulation Coordination	p. 103
11.2 Data Required for Insulation Coordination Study	p. 104
11.3 Insulation Coordination Standards	p. 104
11.4 Voltage Flicker Concerns	p. 105
11.5 Effect of Voltage Variation on Power Flow in Grid-Tied DPV-GT Systems	p. 106
11.6 Voltage Variation Mitigation	p. 106
Bibliography	p. 106
Chapter 11 Problems	p. 108
12 Inverter Circuit Coordination with a Distributed Photovoltaic Grid Power Transformer	p. 111
12.1 Inverter Definition	p. 111
12.2 Inverter History	p. 111
12.3 Inverter Technology	p. 112
12.3.1 Variable Speed Drive versus Solar Inverter	p. 113
12.3.2 Solar Inverters-Grid Tied versus Non-Grid Tied	p. 113
12.3.3 Solar Inverter Features and Characteristics (Grid-Tied)	p. 113
12.3.4 Solar Inverters-Maximum Power Point Tracking	p. 114
12.3.5 Solar Inverters-Power Monitoring	p. 114
12.4 DC Bias Caused by Inverters	p. 115
12.5 Typical DPV Generation Systems and Their Specifics in Relation to the Transformers	p. 115
12.6 Types of Converter Topologies	p. 116
127 Inverter Technology	p. 117
12.8 Solar Inverters-Anti-Islanding	p. 117
12.8.1 Anti-Islanding (Grid-Tied Systems)	p. 117
12.8.2 Anti-Islanding Exception	p. 118
12.9 Grid-Tie Inverter or Synchronous Inverters	p. 118
12.9.1 Typical Operation	p. 119
12.9.2 Technology	p. 121
12.9.3 Characteristics	p. 121
12.10 Solar Micro-Inverter	p. 123
12.11 String Inverters	p. 124
12.12 Micro-Inverters	p. 125
12.13 Central, Module-Oriented or Module-Integrated, and String Inverters	p. 129
12.13.1 Power Injected into Grid	p. 131
12.13.2 Demands Defined by the Photovoltaic Module	p. 132
12.13.3 Maximum Power Point Tracker Characteristics	p. 132
12.13.4 High Efficiency	p. 133
12.13.5 Reliability	p. 133
12.13.6 Topologies of PV Inverters	p. 133
12.13.6.1 Centralized Inverters	p. 133
12.13.6.2 String Inverters	p. 133
12.13.6.3 AC Module	p. 134
12.13.7 Future Topologies	p. 136
12.13.7.1 Multistring Inverters	p. 136
12.13.7.2 AC Cell Configuration	p. 136
12.13.7.3 Classification of Inverter Topologies	p. 137
12.13.7.4 Power Decoupling	p. 138
12.13.7.5 Capacitors	p. 138
Bibliography	p. 139
Chapter 12 Problems	p. 140
13 Magnetic Inrush Current in Distributed Photovoltaic Grid Power Transformers	p. 143
13.1 Transformer Inrush Current Protection	p. 143
13.2 Protection of the Transformer	p. 144
13.2.1 Selection Criteria #1: Energy	p. 145
13.2.2 Selection Criteria #2: Steady-State Current	p. 146
13.3 Magnetic Inrush Currents due to Geomagnetic-Induced Currents (GICs)	p. 146
14 Eddy Current and Stray Loss Calculations of Distributed Photovoltaic Grid Power Transformer	p. 151
14.1 Eddy Current Loss (ECL) in DPV-GT	p. 151
14.2 Alternate Method for ECL in Windings	p. 152
14.3 Calculation of Stray Losses	p. 153
15 Design Considerations-Inside/Outside Windings for a Distributed Photovoltaic Grid Power Transformer	p. 155
15.1 Design of Windings	p. 155
15.2 Kinds of Windings	p. 156
15.2.1 Pretransposed Strip Conductor	p. 159
15.2.2 Transposed Conductor Proportions	p. 161
15.2.3 Rotary Transposition for Helical or Spiral Windings for Core-Type DPV-GTs	p. 164
15.3 Typical Conductor Transposition Examples in Spiral Windings Used in DPV-GTs	p. 168
15.3.1 Transposition of Bunched Conductors	p. 170
15.3.1.1 Stage 1	p. 170
15.3.1.2 Stage 2	p. 171
15.3.2 Forces on Windings	p. 171
15.3.3 Forces between Two Coils in Series	p. 173
15.3.4 Forces in Concentric Coils	p. 174
15.3.5 Mechanical Strength of Copper	p. 175
15.3.6 Backup Strength of Outer Turns	p. 175
15.3.7 Compression Force on Inner Coil	p. 175
15.3.8 Axial Displacement of Coils and Resultant Axial Forces	p. 176
15.3.9 Calculation of Axial Forces	p. 176
15.3.10 Short-Circuit Currents and Short-Circuit Capability	p. 176
15.4 Core Design	p. 177
15.4.1 Selection Process	p. 180
15.4.2 Application of the Unit	p. 184
15.4.3 Choice of Liquid-Filled or Dry Type	p. 185
15.4.4 Environmental Concerns	p. 187
15.4.5 Liquid Dielectric Selection Factors	p. 187
15.4.6 Cast Coil Insulation Systems	p. 187
15.4.7 Choice of Winding Material	p. 189
15.4.8 Use of Low-Loss Core Material	p. 189
15.4.9 Amorphous Cores	p. 190
15.4.10 Protection from Harsh Conditions	p. 191
15.4.11 Insulators	p. 191
15.4.12 Regulation	p. 192
15.4.13 Voltage Taps	p. 192
15.4.14 Life Expectancy	p. 193
15.4.15 Overloading	p. 194
15.4.16 Insulation Level	p. 195
15.4.17 Liquid-Filled Temperature Considerations	p. 195
15.4.18 Dry-Type Temperature Considerations	p. 196
15.4.19 Losses	p. 196
15.4.20 k-Factor	p. 197
15.4.21 Shielding	p. 198
15.4.22 Placing Transformers Near the Load	p. 199
15.4.23 Accessories	p. 200
15.4.24 New Techniques of Analysis and Design of DPV-GTs for Photovoltaic Solar Conversion	p. 201
15.4.25 Design of Magnetic Circuit	p. 202
15.4.26 Impedance, Accessories, and Loading	p. 206
15.5 Design Procedure	p. 206
15.5.1 Design Process	p. 207
References	p. 213
Chapter 15 Problems	p. 213
16 Special Tests Consideration for a Distributed Photovoltaic Grid Power Transformer	p. 215
17 Safety Protection and Shipping and Dispatch for Distributed Photovoltaic Grid Transformers	p. 221
17.1 Islanding Detection Methods for Safety Monitoring and Control	p. 222
17.2 Safety, Protection, and Monitoring	p. 222
17.2.1 DPV-GT Specific Controls and Related Protections	p. 223
17.2.2 Maximum Power Point Tracking (MPPT)	p. 223
17.2.3 Protection from DC Bus Over-Voltage	p. 224
17.2.4 Protection from DC Bus Over-Current	p. 224
17.2.5 Protection from Reverse DC Bus	p. 224
17.2.6 Protection from Ground Faults	p. 224
17.3 Potential Operations and Management (O&M) Issues	p. 225
17.4 Solar Power Wiring Design	p. 227
17.5 Solar Power System Wiring	p. 228
17.6 Solar Power System Design Considerations	p. 230
17.7 Shipping and Dispatch Considerations for a DPV Grid Power Transformer	p. 231
References	p. 232
Appendix A MATLAB® Program for a Three-Limb Core Design [16]	p. 235
Suggested Reading	p. 245
Appendix B Standards, Codes, User's Guides, and Other Guidelines	p. 247
Index	p. 251

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