Impact of Hybrid Distributed Generation Allocation on Short Circuit Currents in Distribution Systems

214 Pages·2017·2.88 MB·English

Impact of Hybrid Distributed Generation
Allocation on Short Circuit Currents in
Distribution Systems

A thesis submitted for the degree of Doctor of
Philosophy

By
Sara Nader Afifi
Supervisor: Dr Mohamed Darwish

Brunel Institute of Power Systems (BIPS)
Department of Electronic and Computer Engineering
College of Engineering, Design and Physical Sciences
Brunel University London
March 2017
Abstract
The rapid development in renewable generation technologies and flexible
distribution networks requires current infrastructure to be modified and developed to
adapt high penetration levels of distributed generation. Existing distribution
networks were not initially designed and anticipated to accommodate generators on
large scale. Short circuit studies ensure the effectiveness of protection equipment
settings and coordination is maintained in case of short circuit, despite any additional
distributed generation is connected to the distribution network. This research aims to
study and compare the different network fault situations for wind energy systems
with induction generators, photovoltaic energy systems, and diesel generators
connected to distribution networks. The simulation study will be conducted on the
existing IEEE case study systems including 13 bus and 30 bus distribution test
systems, using ETAP software. Short circuit analysis will be performed twice to
include the ANSI/IEEE and the IEC methods for short circuit currents calculation.
Simulated results showed that the wind energy systems have significant impact on
the short circuit currents, whereas the photovoltaic energy systems are found to have
inconsequential effect. The most moderate solution is found to be a distributed
generation mix.

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Acknowledgment
First, I would like to express my deepest gratitude to my supervisor Dr Mohamed
Darwish for his guidance, support, and encouragement throughout this research.
I would like to thank Prof. Gareth Taylor for his advice and secondary supervision at
some stages of this PhD.
A special acknowledgment must go to my dearest husband Dr Ahmed Zobaa who
believed in my potentials and skills, who encouraged me to approach this degree.
Also, his generous care, love and support throughout this journey are the main keys
to my success.
I would like to thank my parents and dearest sister for their encouragement and their
unconditional support to me and to my little family throughout my PhD. Also, I must
acknowledge my dearest friends who believed in my dream and inspired me.
Last, I gratefully thank my little boy Noah, who was born at the beginning of this
journey, and became the real motivation to continue and achieve my PhD.
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Declaration of Authorship
The work described in this thesis has not been previously submitted for a degree in this
or any other university and unless otherwise referenced it is the author’s own work.

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Table of Contents
1 Introduction .......................................................................................................... 1
1.1 Background ................................................................................................... 1
1.2 Distributed generation definition ................................................................... 2
1.3 Aim and objectives ........................................................................................ 6
1.4 Methodology ................................................................................................. 7
1.5 List of publications conducted from this PhD ............................................... 9
1.6 Thesis outline .............................................................................................. 10
2 Literature Review ............................................................................................... 12
2.1 Introduction ................................................................................................. 12
2.2 Challenges of increased penetration of DG in distribution network ........... 13
2.3 Technical impacts of distributed generation on the distribution systems ... 14
2.4 Simulation in literature review .................................................................... 21
2.5 Optimal allocation issues ............................................................................. 26
2.6 Gap in research ............................................................................................ 26
2.7 Summary ..................................................................................................... 29
3 Technology Overview ........................................................................................ 31
3.1 Introduction ................................................................................................. 31
3.2 Electrical power system arrangement .......................................................... 31
3.3 Overview of DG technologies ..................................................................... 35
3.4 Short circuit and short circuit currents ........................................................ 41
3.5 Summary ..................................................................................................... 47
4 Short Circuit Calculations .................................................................................. 49
4.1 Introduction ................................................................................................. 49
4.2 Short circuit calculations according to IEC standards ................................. 49
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4.3 Short circuit calculations according to ANSI/IEEE standards .................... 65
4.4 ANSI/IEEE standard vs IEC standard ......................................................... 71
4.5 Summary ..................................................................................................... 72
5 IEEE 13 Bus Distribution Test System .............................................................. 74
5.1 Introduction ................................................................................................. 74
5.2 System under study ..................................................................................... 74
5.3 IEEE-13 bus distribution test system case studies ...................................... 76
5.4 Simulated results for ANSI calculations ..................................................... 77
5.5 Analysis of simulated results for IEC calculations ..................................... 87
5.6 Comparison between ANSI and IEC simulated results ............................. 100
5.7 Summary ................................................................................................... 101
6 IEEE 30 Bus Distribution Test System ............................................................ 103
6.1 Introduction ............................................................................................... 103
6.2 System under study ................................................................................... 104
6.3 IEEE-30 bus distribution test system case studies .................................... 105
6.4 Simulated results for ANSI calculations ................................................... 108
6.5 Analysis of simulated results for ANSI calculations ................................. 109
6.6 Analysis of simulated results for IEC calculations ................................... 125
6.7 Differences between ANSI and IEC results .............................................. 127
6.8 Summary ................................................................................................... 136
7 Conclusions and Future Work .......................................................................... 137
7.1 Future work ............................................................................................... 140
References ................................................................................................................ 141
Appendix A .............................................................................................................. 151
Appendix B .............................................................................................................. 154
Appendix C .............................................................................................................. 157
Appendix D .............................................................................................................. 159
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List of Figures
Figure 3.1 Distribution System Configuration ......................................................... 32
Figure 3.2 Block diagram of a fundamental photovoltaic power generation system
[97] ........................................................................................................................... 37
Figure 3.3 Schematic diagram of Type 3 WTG [100] ............................................. 39
Figure 4.1 - Schematic diagram of short circuit current of a far-from-generator short
circuit with constant AC component [112] .............................................................. 51
Figure 4.2- Schematic diagram of short circuit current of a near-to-generator short
circuit with decaying AC component [112] ............................................................. 51
Figure 5.1. The worst cases during 3-ph fault for ANSI calculations ...................... 83
Figure 5.2. The worst cases during LL-G fault for ANSI calculations .................... 84
Figure 5.3 The minimum short circuit currents during 3-ph fault for ANSI
calculations ............................................................................................................... 85
Figure 5.4 The minimum short circuit currents during LL-G fault for ANSI
calculations ............................................................................................................... 85
Figure 5.5 Penetration level vs 3-ph short circuit currents for diesel hybrid mix
located at bus 675 for ANSI calculations ................................................................. 86
Figure 5.6 The worst cases during 3-ph fault for IEC calculations.......................... 97
Figure 5.7 The worst cases during LL-G fault for IEC calculations ........................ 97
Figure 5.8 The minimum short circuit currents during 3-ph fault for IEC
calculations ............................................................................................................... 98
Figure 5.9 The minimum short circuit currents during LL-G fault for IEC
calculations ............................................................................................................... 99
Figure 5.10 Penetration level vs 3-ph short circuit currents for diesel hybrid mix
located at bus 675 for IEC calculation ..................................................................... 99
Figure 6.1 The IEEE30 bus system ....................................................................... 104
Figure 6.2. Short Circuit versus different DG penetration level for Three-phase fault
at bus 7 ................................................................................................................... 104
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Figure 6.3 Short Circuit current versus different DG penetration level for LG fault
at bus 7 ................................................................................................................... 112
Figure 6.4 Short Circuit current versus different DG penetration level for LL fault
at bus 7 ................................................................................................................... 112
Figure 6.5 Short Circuit current versus different DG penetration level for LLG fault
at bus 7 ................................................................................................................... 113
Figure 6.6 Short Circuit current versus different DG penetration level for Three-
phase fault at bus 26 ............................................................................................... 114
Figure 6.7 Short Circuit current versus different DG penetration level for LG fault
at bus 26 ................................................................................................................. 114
Figure 6.8 Short Circuit current versus different DG penetration level for LL fault
at bus 26 ................................................................................................................. 115
Figure 6.9 Short Circuit current versus different DG penetration level for LLG fault
at bus 26 ................................................................................................................. 116
Figure 6.10 Short Circuit current versus different DG penetration level for Three-
phase fault at bus 29 ............................................................................................... 117
Figure 6.11 Short Circuit current versus different DG penetration level for LG fault
at bus 29 ................................................................................................................. 117
Figure 6.12 Short Circuit current versus different DG penetration level for LL fault
at bus 29 ................................................................................................................. 118
Figure 6.13 Short Circuit current versus different DG penetration level for LLG
fault at bus 29 ......................................................................................................... 118
Figure 6.14 Short Circuit current versus different DG penetration level for Three-
phase fault at bus 30 ............................................................................................... 119
Figure 6.15 Short Circuit current versus different DG penetration level for LG fault
at bus 30 ................................................................................................................. 119
Figure 6.16 Short Circuit current versus different DG penetration level for LL fault
at bus 30 ................................................................................................................. 120
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Figure 6.17 Short Circuit current versus different DG penetration level for LLG
fault at bus 30 ......................................................................................................... 120
Figure 6.18 Short Circuit current versus different DG penetration level for Three-
phase fault at buses 7 and 29 .................................................................................. 121
Figure 6.19 Short Circuit current versus different DG penetration level for LG fault
at buses 7 and 29 .................................................................................................... 121
Figure 6.20 Short Circuit current versus different DG penetration level for LL fault
at buses 7 and 29 .................................................................................................... 122
Figure 6.21 Short Circuit current versus different DG penetration level for LLG
fault at buses 7 and 29 ............................................................................................ 122
Figure 6.22 Short Circuit current versus different DG penetration level for Three-
phase fault at buses 26 and 30 ................................................................................ 123
Figure 6.23 Short Circuit current versus different DG penetration level for LG fault
at buses 26 and 30 .................................................................................................. 123
Figure 6.24 Short Circuit current versus different DG penetration level for LL fault
at buses 26 and 30 .................................................................................................. 124
Figure 6.25 Short Circuit current versus different DG penetration level for LLG
fault at buses 26 and 30 .......................................................................................... 124
Figure 6.26 The worst cases for ANSI calculations ............................................... 125
Figure 6.27 The worst cases for IEC calculations .................................................. 126

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List of Tables

TABLE 2.1: Voltage Levels Classification in Distribution Networks [31] ............. 15
TABLE 3.1:Type Of Interface for Different Distributed Generation Sources ........ 35
TABLE 4.1: Voltage Factor [112] ........................................................................ 52
Table 5.1: Different scenario𝐶𝐶s examined.................................................................. 76
Table 5.2: ANSI Simulated Results for scenario 1 with no DG installed (kA) ....... 77
Table 5.3: ANSI Simulated Results for Scenario 2 .................................................. 79
Table 5.4: ANSI Simulated Results for Scenario 3 .................................................. 79
Table 5.5: ANSI Simulated Results for Scenario 4 .................................................. 79
Table 5.6: ANSI Simulated Results for scenario 3 at different penetration levels and
Diesel Hybrid mix located at Bus 675 ..................................................................... 79
Table 5.7: Three-phase short circuit current magnitudes (kA) and percentage of the
total short circuit current .......................................................................................... 80
Table 5.8: Comparison of DG units contribution on the short circuit current level at
S2 .............................................................................................................................. 82
Table 5.9: Comparison between DG units contribution on the short circuit current at
S3 .............................................................................................................................. 82
Table 5.10: IEC Simulated Results for Scenario 1- No DG..................................... 88
Table 5.11: IEC Simulated Results for Scenario 2 - Wind ...................................... 88
Table 5.12: IEC Simulated Results for Scenario 3 - Wind ...................................... 88
Table 5.13: IEC Simulated Results for Scenario 4 - Wind ...................................... 89
Table 5.14: IEC Simulated Results for Scenario 2 - PV .......................................... 89
Table 5.15: IEC Simulated Results for Scenario 3 - PV .......................................... 89
Table 5.16: IEC Simulated Results for Scenario 4 - PV .......................................... 90
Table 5.17: IEC Simulated Results for Scenario 2 - Hybrid .................................... 90
Table 5.18: IEC Simulated Results for Scenario 3 - Hybrid .................................... 90
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