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The More Electric Aircraft The More Electric Aircraft
Why Aerospace Needs Power Electronics Why Aerospace Needs Power Electronics
Prof Pat Wheeler
University of Nottingham, Nottingham, UK
Tel. +44 (0) 115 951 5591 Email. [email protected]
The More Electric Aircraft The More Electric Aircraft
Why Aerospace Needs Power Electronics Why Aerospace Needs Power Electronics
Prof Pat Wheeler
University of Nottingham, Nottingham, UK
Tel. +44 (0) 115 951 5591 Email. [email protected]
Introduction Introduction
l The More Electric Aircraft – a step in the direction of a more energy efficient aircraft • The More Electric Aircraft concept • History of more electrical systems in Civil Aircraft • Motivations and systems
l Regeneration onto the Aircraft Power System • Power converters and actuation systems • Benefits and issues • Potential solutions • Simulation results
l The next steps • The Clean Sky JTI project
Introduction Introduction
a step in the direction of a more energy efficient aircraft The More Electric Aircraft concept History of more electrical systems in Civil Aircraft
Regeneration onto the Aircraft Power System Power converters and actuation systems
Power Sources Power Sources “Conventional” Aircraft “Conventional” Aircraft
Jet Fuel
Electrical
Gearbox driven generators
High pressure air “bled” from engine
Pneumatic 200kW 1.2MW
Total “nonthrust” power
Power Sources Power Sources “Conventional” Aircraft “Conventional” Aircraft
Jet Fuel
Propulsion Thrust (≈ 40MW)
Gearbox driven hydraulic pump
Hydraulic
Fuel pumps and oil pumps on engine
Mechanical 240kW 100kW
thrust” power ≈ 1.7MW
• Electrical » Avionics » Cabin (lights, galley, inflight entertainment etc) » Lights, pumps, fans » 115V, 400Hz AC
• Pneumatic » Cabin pressurisation » Air conditioning » Icing protection
• Hydraulic » Flight control surface actuation » Landing gear extension/retraction and steering » Braking » Doors
• Mechanical » Fuel and oil pumps local to engine
Power Sources Power Sources “Conventional” Aircraft “Conventional” Aircraft
flight entertainment etc)
Landing gear extension/retraction and steering
Power Sources Power Sources “Conventional” Aircraft “Conventional” Aircraft
“More Electric Aircraft” “More Electric Aircraft” Concept Concept
Engine driven generators
Existing electrical loads
Electrical system power
Rationalisation of power sources and networks
“Bleedless” engine
Flight control actuation Landing gear/ Braking
ELECTRICAL Cabin pressurisation Air conditioning Icing protection
Jet Fuel
“More Electric Aircraft” “More Electric Aircraft”
Expanded electrical network
Engine driven generators
Electrical system power ≈ 1MW New electrical loads
ELECTRICAL Flight control actuation Landing gear/ Braking
Doors
ELECTRICAL Fuel pumping
Engine Ancillaries
Jet Fuel
Propulsion Thrust (≈ 40MW)
“More Electric Aircraft” “More Electric Aircraft” Some Motivations Some Motivations
l Removal of hydraulic system • reduced system weight • ease maintenance
l “Bleedless” engine • improved efficiency
l Desirable characteristics of electrical systems • controllability
» power on demand
• reconfigurability » maintain functionality during faults
• advanced diagnostics and prognostics » more intelligent maintenance
» increased aircraft availability
l OVERALL • Reduced operating costs
• Reduced fuel burn
• Reduced environmental impact
“More Electric Aircraft” “More Electric Aircraft” Some Motivations Some Motivations
Desirable characteristics of electrical systems
maintain functionality during faults
advanced diagnostics and prognostics
More Electric Aircraft More Electric Aircraft
l Airbus A380 • 4 x 150kVA Wideband VF on turbofan engines
• Flight Control Power – 2 H + 2 E
• Actuator Configuration Ø Combination of Hydraulic and Electrical Actuation
More Electric Aircraft More Electric Aircraft
4 x 150kVA Wideband VF on turbofan engines
Combination of Hydraulic and Electrical Actuation
More Electric Aircraft More Electric Aircraft
l Vickers VC10 • Electrical System – 4 x 40kVA Generators
• Flight Control Power – 2 H + 2 E
• Actuator Configuration Ø Combination of Hydraulic and Electrical Actuation
• Built 50 Years before the Airbus A380
More Electric Aircraft More Electric Aircraft
4 x 40kVA Generators
Combination of Hydraulic and Electrical Actuation
Built 50 Years before the Airbus A380
More Electric Aircraft More Electric Aircraft
l Boeing 787 • 4 x 250kVA Primary Channel Starter Generators
» 500kVA per channel
• 230VAC VF Primary Power Generation
• Electrical Starter/Generators rated at 250/225kVA
• Electric ECS, pressurisation and wing anti
• Removes need for bleed air from engines
S/G6 S/G5
S/G1
Electrical Power Distribution System
S/G4 S/G3 S/G2
230 VAC 3Phase
VF
230 VAC 3Phase
VF
230 VAC 3Phase
VF
250kVA 250kVA 250kVA 250kVA
225kVA 225kVA
230 VAC 3Phase Loads
115 VAC 3Phase Loads
28 VDC Loads
More Electric Aircraft More Electric Aircraft
4 x 250kVA Primary Channel Starter Generators
230VAC VF Primary Power Generation
Electrical Starter/Generators rated at 250/225kVA
Electric ECS, pressurisation and wing antiIcing
Removes need for bleed air from engines
More Electric Aircraft More Electric Aircraft
l Joint Strike Fighter • 270V DC Power System
• Electric actuation systems
• 80kW, 2 channel, switched reluctance generator
• Reduces cost, size and weight of whole aircraft
• Relies on Power Conversion technologies » Harsh environment
» Efficiency
» Reliability
More Electric Aircraft More Electric Aircraft
80kW, 2 channel, switched reluctance generator
Reduces cost, size and weight of whole aircraft
Relies on Power Conversion technologies
More Electric Aircraft More Electric Aircraft
A Possible MEA DC Power System Layout Source: Virginia Polytechnic
More Electric Aircraft More Electric Aircraft
A Possible MEA DC Power System Layout
Typical Power Levels Typical Power Levels for Electrical Loads for Electrical Loads
Power User Comments
Air Conditioning ECS Flight Controls Primary and secondary
Fuel pumps Wing Ice Protection Thermal mats or similar Landing Gear Retraction, steering and braking
Engine starting May be used for additional applications
Typical Power Levels Typical Power Levels for Electrical Loads for Electrical Loads
Comments Typical Power level
4 x 70kW+ Primary and secondary 3 kW to 40kW
often short duration at high
loads about 10kW
Thermal mats or similar 250kW+ Retraction, steering and braking 25kW to 70kW
short duration May be used for additional applications
200kW+ short duration
AC Power Generation AC Power Generation
l Mechanical Constant Frequency Gen. [traditional]
• Mechanical gearbox creates a constant speed shaft from a variable speed input
• Constant speed shaft drives the Generator » Voltage control used for the generator » 400Hz voltage supply – fixed frequency
• Expensive to purchase and maintain » Single source due to patents
Constant Speed Mechanical Drive
[Gearbox]
Constant Speed Shaft Variable speed
Engine Shaft
AC Power Generation AC Power Generation
Mechanical Constant Frequency Gen. [traditional]
Mechanical gearbox creates a constant speed shaft from a
Constant speed shaft drives the Generator Voltage control used for the generator
fixed frequency
Expensive to purchase and maintain Single source due to patents
Generator
Constant Speed Shaft 3phase
400Hz, 115V
AC Power Generation AC Power Generation
l Variable Frequency Generation [new aircraft]
• Generator provides variable frequency supply » Voltage control around generator
• Direct connection between generator and power bus » Simple and reliable generation
• Nearly all aircraft loads will require power converters for control » Good News for Power Electronics Engineers!
Generator Variable speed Engine Shaft
AC Power Generation AC Power Generation
Variable Frequency Generation [new aircraft]
Generator provides variable frequency supply Voltage control around generator
Direct connection between generator and power bus Simple and reliable generation
Nearly all aircraft loads will require power converters
Good News for Power Electronics Engineers!
3phase 320Hz to 800Hz 230V or 115V
Actuation Systems Actuation Systems
• Elimination of hydraulics » ElectroMechanical Actuator » 30kW matrix converter » integrated with ballscrew housing/heatsink
• Holistic design of motor/load/power converter » Maximise system efficiency » Minimise system weight
• Advanced thermal management » Copes with intermittent operation
Example of an Actuation System
Matrix Converter
PM Motor
Control
Ram Position 250Hz sampling rate 2Hz bandwidth
Motor Current 12.5kHz sampling rate 200Hz Bandwidth
Motor Speed 1.25kHz sampling rate 20Hz bandwidth
Supply 360Hz to 800Hz
Resolver LEMs
Supply Voltage
Ram Position Demand
Voltage transducers Filter
Actuation Systems Actuation Systems
integrated with ballscrew housing/heatsink
Holistic design of motor/load/power converter
Actuator
Ram Position 250Hz sampling rate 2Hz bandwidth
1.25kHz sampling rate
LVDT
Regeneration: Converters Regeneration: Converters
3Phase Supply
3Phase Load
Energy dissipation in the DC Link
Traditional Solution:
• DC link chopper and resistor in DC link used to dump regenerative energy
• Lowers system efficiency and increase size and weight of equipment
• Measure DC link voltage and operate chopper when DC link voltage above a set level
• Resistor and associated cooling can double volume and weight of the power converter
Regeneration: Converters Regeneration: Converters
3phase supply
Bi directional switch
Load
Long Term Solution:
• Allow regeneration onto aircraft power system
• Use a Direct [Matrix] Converter or a controlled rectifier
• Energy returned to supply giving a smaller, lighter power converter
Motor Speed Reversal Motor Speed Reversal Motor Speed Reversal Motor Speed Reversal
Motor shaft speed (rpm)
qaxis current
Phase A current
Phase B current
Phase C current
Torque (Nm)
Motor Speed Reversal Motor Speed Reversal
REGENERATION
Motor Speed Reversal Motor Speed Reversal
Motor shaft speed (rpm)
qaxis current
Phase A current
Phase B current
Phase C current
Torque (Nm)
Options for Regenerative Options for Regenerative Energy Management Energy Management
l Regeneration will save considerable weight and volume
• Regenerative energy must be handled correctly to maintain Power Quality
l Eight methods have been identified for safe electrical regenerative energy management
• Centralised Energy Storage
• Centralised Energy Dissipation
• Local Voltage Control
• Return Energy to Source
• Separate Bus for Regenerative Energy
• Local Energy Dissipation
• Local Energy Storage
• Hybrid Structures with Local Dissipation
Options for Regenerative Options for Regenerative Energy Management Energy Management
Regeneration will save considerable weight and volume
Regenerative energy must be handled correctly to maintain
Eight methods have been identified for safe electrical regenerative energy management
Separate Bus for Regenerative Energy
Hybrid Structures with Local Dissipation
Options for Regenerative Options for Regenerative Energy Management Energy Management
• Local Energy Dissipation
Generator
Bus Control
Control Recovery Advantages
Local to load No Existing solution
• do not allow regeneration onto the aircraft bus
• ensure that each item of equipment has energy dissipation if required
• today’s solution
Options for Regenerative Options for Regenerative Energy Management Energy Management
Local Energy Dissipation – existing solution
Converters
Regenerative Loads
Energy Dissipation eg. Resistor with break
chopper
Advantages Disadvantages
Existing solution Size and weight of equipment, sub
optimum system design
ensure that each item of equipment has
Options for Regenerative Options for Regenerative Energy Management Energy Management
• Return Energy to Source Control Recovery Advantages
Centralised Yes No large additional hardware
Generator
Bus
Enhanced Control
• allow regeneration onto the aircraft bus • use the generator as a motor if required
• the regenerative power would be returned to the engine inertia • only possible if there is no auxiliary gearbox
Options for Regenerative Options for Regenerative Energy Management Energy Management
Return Energy to Source Advantages Disadvantages
No large additional hardware
Possible change to existing generator control methods
Converters
Regenerative Loads
allow regeneration onto the aircraft bus use the generator as a motor if required
the regenerative power would be returned to the engine inertia only possible if there is no auxiliary gearbox
Impact of Regeneration Impact of Regeneration
• Modelling study performed in SABER
• Sudden change of total actuator power from 40kW motoring to 55kW regeneration
• Simulation for given for a fully preloaded generator
• voltages at HVAC Bus 230V and at AC Bus 115V are kept within the envelopes according to MIL STD704F
Impact of Regeneration Impact of Regeneration
Sudden change of total actuator power from
voltages at HVAC Bus 230V and at AC Bus 115V are kept within the envelopes according to MIL
Generator Torque reduces
MIL_STD704F envelope for transients
Conclusions Conclusions
• Power Electronics can offer advantages in aerospace applications • System efficiency, • Size and weight • Flexibility
• There are challenges for Power Electronics in this environment • Losses • Reliability • Integration
• Future projects will take these area forward
Power Electronics can offer advantages in aerospace
There are challenges for Power Electronics in this
Future projects will take these area forward
Clean Sky JTI Clean Sky JTI
l Total project budget – €1.6B • Duration – 7 years
l Clean Sky JTI work is split into six “ITDs”
l Led by 12 companies [Members] • Thales, Liebherr, Airbus, Dassualt, Alenia, SAAB, Rolls Royce, Safran, EADS, ….
l Each ITD then has 5 or 6 other organisations [Associate Members]
l 25% of funding reserved for Calls for Proposals
• See www.cleansky.eu now for first call and get involved
Clean Sky JTI Clean Sky JTI
l The University of Nottingham is an Associate member
• Systems for Green Operations ITD • We are the only University which is an Associate Member in our own right
• Budget of about €10M