Armstrong, Michael J. and Blackwelder, Mark and Bollman, Andrew and Ross, Christine and ...

270 Pages·2015·12.06 MB·English

NASA/CR—2015-218440 EDNS04000038188/002
Architecture, Voltage, and Components for a
Turboelectric Distributed Propulsion Electric Grid
Final Report
Michael J. Armstrong and Mark Blackwelder
Rolls-Royce North American Technologies, Inc. (LibertyWorks), Indianapolis, Indiana
Andrew Bollman and Christine Ross
Rolls-Royce Corporation, Indianapolis, Indiana
Angela Campbell
Georgia Institute of Technology, Atlanta, Georgia
Catherine Jones and Patrick Norman
University of Strathclyde, Glasgow, Scotland, United Kingdom
July 2015
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NASA/CR—2015-218440 EDNS04000038188/002
Architecture, Voltage, and Components for a
Turboelectric Distributed Propulsion Electric Grid
Final Report
Michael J. Armstrong and Mark Blackwelder
Rolls-Royce North American Technologies, Inc. (LibertyWorks), Indianapolis, Indiana
Andrew Bollman and Christine Ross
Rolls-Royce Corporation, Indianapolis, Indiana
Angela Campbell
Georgia Institute of Technology, Atlanta, Georgia
Catherine Jones and Patrick Norman
University of Strathclyde, Glasgow, Scotland, United Kingdom
Prepared under Contract NNC13TA77T
National Aeronautics and
Space Administration
Glenn Research Center
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July 2015
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Contents
1.0 Introduction ........................................................................................................................................... 1
1.1 TeDP Electrical System ................................................................................................................ 1
1.2 A Review of Current Voltage Standards ....................................................................................... 2
1.2.1 Grid Codes ........................................................................................................................ 4
1.2.2 Maritime Power Systems .................................................................................................. 8
1.2.3 Current Aircraft Voltage Standards ................................................................................ 11
1.3 Challenging in Creating DC Propulsion Standards ..................................................................... 12
1.4 TeDP Electrical System Voltage Standards ................................................................................ 13
1.4.1 Regulation, Protection, and Recovery: A Design/Engineering Perspective ................... 13
1.4.2 Operational Voltage Limits Category Definitions .......................................................... 14
1.4.3 Selection of the Optimal Operating Voltage ................................................................... 16
1.5 Introduction Summary ................................................................................................................ 19
2.0 Architecture Selection ......................................................................................................................... 20
2.1 Architecture Candidates .............................................................................................................. 20
2.1.1 Concept 1: Baseline Architecture.................................................................................... 20
2.1.2 Concept 2: Inner Bus Tie Concept .................................................................................. 21
2.1.3 Concept 3: 3-Bus Multifeeder Concept ........................................................................... 21
2.1.4 Concept 4: Cross-Redundant Multifeeder Concept ........................................................ 21
2.1.5 Concept 5: 4-Bus Inner Bus Tie Multifeeder Concept .................................................... 22
2.2 Architecture Evaluation and Selection ........................................................................................ 24
2.3 Weight Sensitivity and Deliverable Objectives .......................................................................... 25
2.4 Overview and Naming Convention for Selected TeDP Architecture ......................................... 27
3.0 Terrestrial Systems Benchmarking ..................................................................................................... 29
3.1 Power Transmission Superconducting Cable Installations ......................................................... 29
3.2 Future DC Power Transmission Installations ............................................................................. 30
3.3 Superconducting Fault-Current Limiter Installations and Prototypes......................................... 31
3.4 High Power Normally Conducting Solid-State Switchgear ........................................................ 31
3.5 Cryogenic Semiconductors ......................................................................................................... 32
3.6 Cryogenic Power Converter Prototypes ...................................................................................... 34
3.7 Superconducting Electric Machine Prototypes ........................................................................... 35
3.8 Study Voltage Range Conclusion ............................................................................................... 35
4.0 DC Protection Devices ........................................................................................................................ 37
4.1 Introduction ................................................................................................................................. 37
4.2 DC Electromechanical Circuit Breakers ..................................................................................... 38
4.2.1 Conventional DC EMCBs ............................................................................................... 38
4.2.2 EMCBs Applied to Superconducting Systems ............................................................... 39
4.3 Hybrid Circuit Breakers .............................................................................................................. 42
4.4 Solid-State Circuit Breakers........................................................................................................ 45
4.5 Summary ..................................................................................................................................... 47
5.0 Component Sensitivities and Sensitivity Modeling ............................................................................ 48
5.1 Component Sensitivity Overview ............................................................................................... 48
5.2 Rectifier and Inverter .................................................................................................................. 51
5.2.1 Model Overview ............................................................................................................. 52
5.2.2 Source-Side Converters ................................................................................................... 54
5.2.3 Source-Side Converters Trends....................................................................................... 67
5.2.4 Load-Side Converters ..................................................................................................... 73
5.2.5 Load-Side Converter Trends ........................................................................................... 75
5.3 Cables Model Overview.............................................................................................................. 80
5.3.1 Cable Layout ................................................................................................................... 80
NASA/CR—2015-218440 iii
5.3.2 Monopolar, Bipolar, Redundancy and Three Phase AC ................................................. 81
5.3.3 Superconducting Material ............................................................................................... 82
5.3.4 Applied Field .................................................................................................................. 83
5.3.5 Cryostat ........................................................................................................................... 83
5.3.6 Cooling ............................................................................................................................ 85
5.3.7 Losses .............................................................................................................................. 85
5.3.8 AC Losses ....................................................................................................................... 86
5.3.9 Dielectric ......................................................................................................................... 86
5.3.10 Mass and Efficiency Trends ............................................................................................ 87
5.3.11 DC Cable ......................................................................................................................... 89
5.3.12 AC Cable ......................................................................................................................... 90
5.3.13 Cable Losses ................................................................................................................... 91
5.4 Superconducting Magnetic Energy Storage ................................................................................ 92
5.4.1 Parameter Diagram ......................................................................................................... 93
5.4.2 Sizing Equations ............................................................................................................. 94
5.4.3 Power Electronics ........................................................................................................... 97
5.4.4 Cryocooling Weight Calculations ................................................................................... 98
5.4.5 SMES Sensitivity Study Parameters and Assumption Overview ................................... 98
5.4.6 Mass and Efficiency Trends ............................................................................................ 99
5.5 Circuit Breakers ........................................................................................................................ 105
5.5.1 Model Overview ........................................................................................................... 106
5.5.2 Mass and Efficiency Trends .......................................................................................... 108
5.6 Superconducting Fault Current Limiters ................................................................................... 116
5.6.1 Modeling Approach ...................................................................................................... 116
5.6.2 Geometry and Winding ................................................................................................. 117
5.6.3 Parameter Diagram ....................................................................................................... 119
5.6.4 Governing Equations..................................................................................................... 120
5.6.5 Quench Modeling .......................................................................................................... 120
5.6.6 Quench Cooling ............................................................................................................ 121
5.6.7 Induction Equations ...................................................................................................... 122
5.6.8 Mass Equations ............................................................................................................. 124
5.6.9 Assumptions Overview ................................................................................................. 124
5.6.10 Geometry Sensitivity..................................................................................................... 129
5.6.11 Efficiency Trends .......................................................................................................... 131
5.7 Generators ................................................................................................................................. 134
5.8 Cryogenic System ..................................................................................................................... 134
5.9 Component Sensitivity Modeling Summary ............................................................................. 134
6.0 Narrowed DC Voltage Range............................................................................................................ 135
6.1 Introduction ............................................................................................................................... 135
6.2 Architecture Assumptions ......................................................................................................... 135
6.3 Electrical System Mass Sensitivity to Voltage ......................................................................... 137
6.4 Electrical System Cooling Requirements Sensitivity to Voltage .............................................. 139
6.5 IGBT and Diode Switching and Conduction Losses ................................................................ 142
6.6 Cryocooler Mass ....................................................................................................................... 142
6.7 Narrowed Voltage Range .......................................................................................................... 144
7.0 GT Dynamic Model .......................................................................................................................... 147
7.1 Introduction ............................................................................................................................... 147
7.2 Superconducting Fault Current Limiter .................................................................................... 147
7.2.1 SFCL Modeling Overview ............................................................................................ 147
7.2.2 SFCL SimPowerSystems Model ................................................................................... 148
7.2.3 SFCL State-Space Model .............................................................................................. 153
NASA/CR—2015-218440 iv
7.3 Solid-State Circuit Breaker ....................................................................................................... 154
7.3.1 SSCB Modeling Overview ............................................................................................ 155
7.3.2 SSCB SimPowerSystems Model .................................................................................. 157
7.4 Energy Storage Model (SMES) ................................................................................................ 159
7.5 Power Converter Models .......................................................................................................... 161
7.5.1 Rectifiers ....................................................................................................................... 162
7.5.2 Inverters ........................................................................................................................ 172
7.6 System Modeling ...................................................................................................................... 177
7.6.1 Single Motor Model ...................................................................................................... 178
7.6.2 Fault Isolation Model .................................................................................................... 182
7.6.3 Nominal Recovery Model ............................................................................................. 182
7.6.4 Failure Scenarios ........................................................................................................... 182
7.6.5 Running the Models ...................................................................................................... 195
7.7 Summary and Future Studies .................................................................................................... 196
8.0 Conclusions ....................................................................................................................................... 197
8.1 Power Electronics ..................................................................................................................... 197
8.2 Protection .................................................................................................................................. 198
8.3 Energy Storage .......................................................................................................................... 198
8.4 Distribution ............................................................................................................................... 199
8.5 Dynamic Modeling ................................................................................................................... 199
Appendix A.—Acronyms and Abbreviations ........................................................................................... 201
Appendix B.—IGBT Data ........................................................................................................................ 203
Appendix C.—Dynamic Models .............................................................................................................. 205
Appendix D.—Strathclyde Report ............................................................................................................ 213
References ................................................................................................................................................. 252

NASA/CR—2015-218440 v

Architecture, Voltage, and Components for a Turboelectric
Distributed Propulsion Electric Grid
Final Report

Michael J. Armstrong and Mark Blackwelder
Rolls-Royce North American Technologies, Inc. (LibertyWorks)
Indianapolis, Indiana 46207

Andrew Bollman and Christine Ross
Rolls-Royce Corporation
Indianapolis, Indiana 46206

Angela Campbell
Georgia Institute of Technology
Atlanta, Georgia 30332

Catherine Jones and Patrick Norman
University of Strathclyde
Glasgow, Scotland, G1 1XQ, United Kingdom
1.0 Introduction
1.1 TeDP Electrical System
The development of a wholly superconducting turboelectric distributed propulsion system presents
unique opportunities for the aerospace industry. However, this transition from normally conducting
systems to superconducting systems significantly increases the equipment complexity necessary to
manage the electrical power systems. Due to the low technology readiness level (TRL) nature of all
components and systems, current Turboelectric Distributed Propulsion (TeDP) technology developments
are driven by an ambiguous set of system-level electrical integration standards for an airborne microgrid
system (Figure 1).
While multiple decades’ worth of advancements are still required for concept realization, current
system-level studies are necessary to focus the technology development, target specific technological
shortcomings, and enable accurate prediction of concept feasibility and viability. An understanding of the
performance sensitivity to operating voltages and an early definition of advantageous voltage regulation
standards for unconventional airborne microgrids will allow for more accurate targeting of technology
development.
Propulsive power-rated microgrid systems necessitate the introduction of new aircraft distribution
system voltage standards. All protection, distribution, control, power conversion, generation, and
cryocooling equipment are affected by voltage regulation standards. Information on the desired operating
voltage and voltage regulation is required to determine nominal and maximum currents for sizing
distribution and fault isolation equipment, developing machine topologies and machine controls, and the
physical attributes of all component shielding and insulation. Voltage impacts many components and
system performance.
NASA/CR—2015-218440 1
Figure 1.—Rolls-Royce TeDP System Architecture Concept.

Issues that must be considered for higher voltage operation are the following:

• Maximum and steady-state current ratings
• Fault current interruption for fault isolation and protection
• Partial discharge and corona protection
• Dielectric insulation life
• Safety procedures for testing, manufacturing, and maintenance

To assess the feasibility of unconventional airborne N+2/3 microgrid concepts more accurately, tools
and processes are necessary to estimate and govern the development of appropriate voltage regulation
standards for these unconventional concepts. An integrated system-level process for identifying the
desired voltage standards would allow for more accurate prediction of electrical system weight and
volumes, overall system reliability, and safety of technology concept. This influences the vehicle-level
feasibilities assessments, highlighting technology gaps where increased development is needed
(protection equipment). Once advantageous sets of standards are identified, these standards can be used to
assist in informing electrical technology development relating to expected systems interactions and
operational constraints.
A holistic approach to defining the appropriate standards is necessary to guide future technology
developments. Most current superconducting technology developments are subject to constraints imposed
by interfacing with normally conducting terrestrial systems. However, because the NASA N3-X
microgrid is wholly superconducting, many of the driving connection constraints are removed, and the
operating standards for a wholly superconducting system can be tailored to capture maximum benefit to
the entire system. Additionally, because this system must be airworthy and flight critical, operating
standards must be defined that lend specifically to aircraft environmental, safety, and performance
objectives.
1.2 A Review of Current Voltage Standards
Terrestrial systems have adopted multi-kilovolt (kV) standards for electrical power distribution.
However, the aerospace community typically operates well under the kV level. The highest accepted
power distribution voltage for conventional transport aircraft is ±270 Vdc. These common voltage
practices reflect the current aircraft electrical power systems paradigm. While increased voltages would
NASA/CR—2015-218440 2