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Power Conversion Technologies for Improved System Performance Kaz Furmanczyk Crane Aerospace & Electronics
2009 Join Service Power Expo May 4-7, 2009 – New Orleans, Louisiana
2©Crane Aerospace and Electronics
Introduction
Background
New Challenges for Power Conversion Equipment on Airplanes
Review of Technology Options for Powering Motors that Meet Aerospace Requirements
Implementing Modeling and Simulations for Design Optimization - Example
Conclusions
Summary of Hardware Performance
3©Crane Aerospace and Electronics
Background
Traditional constant frequency power sources (400 Hz) on airplanes are being replaced by variable frequency generators (typically 360-800 Hz)
Pneumatic and hydraulic systems are being replaced with electrical devices – most of which are using electric motors
More electrical equipment is being added to airplanes – power quality becoming an issue
4©Crane Aerospace and Electronics
Challenges
This creates new challenges, which need to be resolved:
Challenge #1 – Speed of inductive motors varies with frequency solution: replace inductive motors with DC brushless motors• However, direct rectification of AC into DC generates high
current distortion – exceeding acceptable power quality limits
Challenge #2 – Find effective solution for converting AC into DC with good power quality
5©Crane Aerospace and Electronics
Power Quality
Effect of power conversion is reflected back onto the aircraft AC bus
The smoother the current waveform ---> the better the “Power Quality”
18-pulse, 30-pulse and active PFC approaches represent good power quality
~ ~~ =+
-Aircraft
Generator
PowerConverter
ElectronicLoads
AC DC
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6-pulse
12-pulse
18-pulse
30-pulseActive PFC
Pow
er Q
ualit
y im
prov
es
6©Crane Aerospace and Electronics
Power Quality
Power quality requirements from leading OEMs (examples):• Boeing: 787B3-0147 • Airbus: AMD-24
Recent, DO-160, Rev. F Document imposed power quality requirements for aerospace products powered from an aircraft AC power systemThe most significant requirement is on restriction of individual harmonics generated by user equipment rated 35 VA or moreThe harmonic limits requirement makes direct rectification obsolete• Practically, all motor drivers, which are using direct rectification need
to be replaced or upgraded• Majority of traditional TRU units can not meet new current limit
requirements – improved designs or larger filters are needed
7©Crane Aerospace and Electronics
DO-160F Current Harmonics Limit
Each current harmonic, up to 40th harmonic has specified limit
8©Crane Aerospace and Electronics
Existing Approach
~ M
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1 4 7 10 13 16 19 22 25 28 31 34 37 40
Harmonics
[%] H. Limits
6-p Rect.
Traditionally, 6-pulse rectification provides DC power for motors However, input current harmonics exceeded DO-160F limits New - more advanced technology - is required to convert AC into DC
Current waveform
Harmonics
THD = 30.7%
9©Crane Aerospace and Electronics
Technology Options
The following power conversion technologies are capable of meeting the new power quality requirements: • High frequency switch mode conversion (active
conversion)• Multiphase power conversion (passive conversion)• Other harmonic correction techniques, based on:
• Harmonic injection• Active filter implementation
10©Crane Aerospace and Electronics
High Frequency Switch Mode Conversion
~ M
6-pulse rectifier being replaced by
3-phase switch mode converter
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THD < 5%
Input Current meets power quality
Switch Control
11©Crane Aerospace and Electronics
High Frequency Switch Mode Conversion
Two practical solutions, based on:
Boost Converter
Regulated DC Output Voltage:• 320 Vdc minimum (with 115 Vac input) - for boost converter• 230 Vdc maximum (with 115 Vac input) - for buck converter
Meets Input Current Harmonic LimitsSoft Start AbilityPower Factor: 0.994–0.998Efficiency: 95–97 %
Buck Converter
DC Output
Three-Phase AC Input
DC Output
Three-Phase AC Input
12©Crane Aerospace and Electronics
Multiphase Power Conversion
~ M
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Input Current meets power quality
6-pulse rectifier being replaced by ATRU (18-pulse)
THD = 6.4%
CB
A
13©Crane Aerospace and Electronics
Multiphase Power Conversion
3-phase to n-phase autotransformer
3-phase n-phase
Three-PhaseAC Input
DC Output
1 2 n
Output Voltage: 270 Vdc nominal (with 115 Vac input); passive regulationMeets Input Current Harmonic LimitsPower Factor: 0.980-0.990 Efficiency: 96-98%Simplicity: low parts count; no need for energy storage components (C or L)
DesignApproach
Output Voltage Ripple[% p-p]
Input Current THD[%]
6-pulse
14 28-33
12-pulse
3.4 9-14
18-pulse
1.52 6-9
30-pulse
0.55 2.5-3.5
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14©Crane Aerospace and Electronics
Design Example - Multiphase Power Converter
Some of available 18-pulse autotransformer options:
It is almost impossible to analyze topology and optimize design without converter modeling and running simulations
A
C
B
A
C
B
A
CB
Option A Option B Option C
TA4.I1 [A] TA2.I2 [A] TA1.I2 [A] TA5.I2 [A] TA3.I2 [A] TA6.I2 [A]
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18-pulse autotransformer topology meets new harmonic limits – if designed correctly
Current waveforms in transformer windings become very complex
Autotransformer converts 3-phase input voltage into 9-phase output
voltages (spaced 40 degrees from each other)
15©Crane Aerospace and Electronics
Design Example - Multiphase Power Converter
ATRU Schematic.ssh
®
Simulation properties:Step width maxStep width minSimulation end time 5
NC4
NC1
EA
NC2
NC3
NC5
NC6
NB4
NB1
NB2
NB3
NB5
NB6
NA4
NA1
NA2
NA3
NA5
NA6
EB
EC
D1
D2
D3
D4
D5
D6
D7
D8
D9
D10
D11
D12
D13
D14
D15
D16
D17
D18
R1
R6
R8
R7
R3
R5
R4
R9
R2
18-pulse ATRU Non-Linear Model
ICA:
Input Parameters Control Equations
EQU
RW1:=2.1m*1.5
LPCT:=0.0005*1
N3:=11
Lg:=0.00075*2*2.54
FREQ:=400
RW4:=38.5m*1.5
N6:=15
RW3:=4.5m*1.5
N1:=6
Lmean_length:=18.09
LM:=16m
N2:=13
PHI0:=0
N4:=37
RW5:=4.4m*1.5
Acore:=21.2
RW2:=4.1m*1.5
N5:=13
RW6:=4.7m*1.5
X Y
NL NL NL
I I I
BH Curve 2
NL A NL B NL C
B A
VM1_prim.V
B B
VM2_prim.V
B C
VM3_prim.V
G
B
C
IA
IB
IC
G
B
C
B
G
C
Coil A Coil B Coil C
Magnetic Core
Output Filter
RB
RA
RC
RLOAD
Power Transformer
P_Load:=135*1
C1220u
R100.3
C2220u
R110.3
R1249.9k
R1349.9k
R1449.9k
R1549.9k
Rectifers
R18
C3
R16
C4
R17
C5
C6 R19
L6
RA1
RB1
RC1
L4
L5
C70.33u
R220.03
C80.33u
R230.03
3.3n
3.9
3.3n
3.9
3.3n 3.3n 3.3n 3.3n 3.3n 3.3n 3.3n
3.3n
3.9 3.9 3.9 3.9 3.9 3.9 3.9
3.9 3.9 3.9 3.9 3.9 3.9 3.9 3.9 3.9
3.3n 3.3n 3.3n 3.3n 3.3n 3.3n 3.3n 3.3n
Power Source Input Filter
Load
16©Crane Aerospace and Electronics
Design Example - Multiphase Power Converter
Transformer construction challenges:• Choosing winding material (copper, aluminum) • Selecting conductor shape (round wire, square wire, foil)• Defining and optimizing core geometry and aspect ratio• Optimizing interactions between windings (leakage
inductance, proximity effects)
It is not practical to build and test each considered option
Therefore, design iterations and optimizations need to be performed on computers
17©Crane Aerospace and Electronics
Design Example - Multiphase Power Converter
Define core geometry and winding configuration
Simulate performance
Convert geometry and materials into electrical parameters
Core LossesWinding LossesLeakage InductanceRegulation
Adjust and optimize
Transformer Construction Optimization:
18©Crane Aerospace and Electronics
Design Example - Multiphase Power Converter
A
CB
Simulate converter performance and verify power quality
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First Completed DesignPower Quality not met; several current harmonics exceed limits
Input Current WaveformsAutotransformer Configuration
Optimized DesignAll current harmonics within
specification plus margin
Completed HardwarePerformance correlates very closely with optimized design
Interactive Optimization
Fabrication
Design
19©Crane Aerospace and Electronics
Performance Summary of Existing Hardware
Parameter Design APassive
(12-pulse)
Design BPassive
(18-pulse)
Design CPassive
(30-pulse)
Design DActive(Boost)
Design EActive(Buck)
Output Power 4.5 kW 1.6 kW 8.6 kW 15 kW 5 kW
Input Voltage (nominal) 230 Vac 115 Vac 115 Vac 115 Vac 460 Vac
Output Voltage (nominal)
270 Vdc 270 Vdc 320 Vdc 400 Vdc 460 Vdc
Power QualityMeeting DO-160E
….Current THDCurrent Waveform
Yes11%Picture A
Yes6.4%
Picture B
Yes3.3%
Picture C
Yes3%
Picture D
Yes3%
Picture E
Power Factor 0.986 0.992 0.998 .990 .990
Output Ripple 15 Vp-p 12 Vp-p 7 Vp-p 3 Vp-p 10 Vp-p
Efficiency 95% 96% 97% 97.5 % 96 %
EMI Filter No Yes No Yes Yes
Size 6” x 4.6” x 3” 7” x 2.6” x 2” 9” x 6” x 3.4” 11” x 15” x 3” 13.7” x 3.6” x 4”
Weight 5.5 lb 3.1 lb 10.2 lb 20.8 lb 6.7 lb
20©Crane Aerospace and Electronics
Input Current Waveforms of AC/DC Converters
A) Passive, 12-pulse B) Passive, 18-pulse C) Passive, 30-pulse
D) Active, Boost E) Active, Buck
21©Crane Aerospace and Electronics
Comparison between Active and Passive Approaches
Active Harmonic Reduction (Switch Mode)
Passive Harmonic Reduction (Multi-Phase)
Input Voltages 115 or 230 Vac 115 or 230 Vac
Output Voltages 150 - 230, 320 – 600 Vdc (without use of additional DC/DC converter)
Is regulated over variations in line and load
150 – 600 Vdc (set by adjusting transformer turns ratio)
Varies with line voltage and load
Harmonics THD 3 – 7% THD 3 – 12% (dependent on topology)
Power Factor 0.980- 0.998 0.980 – 0.998
Output Ripple Dependent on output filter Dependent on output filter
Efficiency 95 – 97% 96 – 98%
Soft Start Available with existing design Needs to be added on
Over-current Protection Available with existing design Needs to be added on
Cooling Method Conduction, liquid or air Conduction, liquid or air
Advantages Precise output voltage regulationOutput voltage can be adjustedBuilt in soft-startBuilt in over-current protection/current limitingThe same unit can operate at 400Hz or 60HzSignificantly lower weight at 60 Hz
SimplicityNo need for energy storage devices or controlHigh reliabilityTypical MTBF - 250,000 hoursRobust – accepts high overloadsLower weight at 400 Hz applicationsLower cost
Disadvantages Lower reliabilityHigh energy storage capacitor needed(Aluminum electrolytic)No overload capabilitiesHigher costGap in output voltage setting -Additional DC/DC converter is needed to obtain
Voltage between 230 Vdc and 320 Vdc
No output voltage regulation Input voltage variations are passed to the output, plus
about 4% voltage drop from no load to full loadAdditional DC/DC converter is needed to obtain full
voltage regulationPresence of inrush current - basic designAdditional circuitry is needed to shape input current
22©Crane Aerospace and Electronics
Existing Hardware Examples
4 kW Converter -230Vac/270Vdc
135 kW Converter - 230Vac/540Vdc(Liquid cooled)
5 kW Converter - 230Vac/540Vdc 8 kW Converter - 115Vac/300Vdc(Fan cooled)
15 kW Converter -115Vac/270Vdc
1 kW Converter - 115Vac/270Vdc
23©Crane Aerospace and Electronics
Conclusions
Demands for electrical power on today’s airplane are increasingTraditional, constant frequency power systems are being replaced by variable frequencyDC brushless motor becoming the motor of choice on new airplanes – it requires DC power to operateNew power conversion technologies are needed to fully meet recent power quality requirements – creating new challengesEffective simulation and optimization tools are critical in successful development of new generation aerospace power converters Two groups of technologies, capable of meeting new power quality requirements, are emerging: passive and active approachWhen unregulated DC voltage can be tolerated, multiphase conversion has a good fit in aerospace applications
24©Crane Aerospace and Electronics
More Information
Crane Aerospace & Electronics, Power Solutions, designs, manufactures and supports products and capabilities via our brands: ELDEC, Interpoint and Keltec. We provide both Standard Power Products and Custom Power Products.
• Standard Power Products consist primarily of our DC-DC converter and filter modules sold under the Interpoint brand.
• Custom Power Products consists of our custom and semi-custom low voltage and high voltage power products and subsystems.
• Our Power solutions meet the current and future needs of our customer’s applications:• Power for Electronic Systems – Our full range of standard and custom products delivers
compliant product performance, low cost of ownership and ease of integration thereby providing the lowest risk comprehensive solutions (Ex. Embedded low voltage power supplies)
• Power Distribution – Low weight, high power quality and high efficiency platform power conversion, management and distribution. We can provide significant weight and volume savings through integrated power conversion, bus control and power control. (Ex. TRUs, ATRUs, etc.)
• Electronic Warfare & Radar – Solid-State or traveling wave tube (TWT) based low/high voltage, high power products and subsystems for mission critical defense platform and payload applications (Ex. TWT amplifiers, high power / high voltage power supplies, etc)
• Energy Storage – Delivering safe integration of energy storage devices into electrical systems while providing the longest maintenance interval and service life at the lowest weight. (Ex. Battery systems, battery charger/controller, batteries, etc.)
• Motor Power Conversion and Control – High power quality ac-dc converters as standalone solutions or as part of an integrated electric drive motor package (Ex. ATRUs, active PFC converters, etc.)
Information: www.craneae.comTechnical assistance: Kaz Furmanczyk, Principal Engineer
• Tel. 425-743-8106; e-mail: [email protected]
25Crane Aerospace and Electronics Proprietary Information
Crane Power SolutionsCrane Power Solutions