View
217
Download
0
Category
Preview:
Citation preview
Power Electronics Research at the University of Nottingham
Professor Pat Wheeler
Email: pat.wheeler@nottingham.ac.uk
Power Electronics, Machines and Control (PEMC) Research Group
UNIVERSITY OF NOTTINGHAM, UK
The University of Nottingham
Professor Pat Wheeler
Email: pat.wheeler@nottingham.ac.uk
Professor Pat Wheeler
Email: pat.wheeler@nottingham.ac.uk
Technology Development from the More Electric Aircraft
to All Electric Flight
UNIVERSITY OF NOTTINGHAM, UK
Introduction
• More Electric Aircraft: – why and technology progress– Aircraft electrical equipment, generators and
power Systems
• All Electric Aircraft – Technology requirements, – Progress to date and future prospects
• Electromagnetically assisted aircraft take-off– Technology and benefits
The More Electric Aircraft
What is a More Electric
Aircraft (MEA)?
Why is there so much
interest in MEA?
Why is Power Electronics
important?
Power Sources Conventional Aircraft
Total “non-thrust” power 1.7MW
Jet Fuel
Propulsion
Thrust ( 40MW)
Gearbox driven
hydraulic pump
Electrical
Gearbox driven
generators
Hydraulic
High pressure
air “bled” from
engine
Pneumatic
Fuel pumps
and oil pumps
on engine
Mechanical200kW 1.2MW 240kW 100kW
Figures for a typical civil aircraft
Total Electrical System Power 1MW
Rationalisation of
power sources and
networks
“Bleedless” engine
Expanded electrical network
Engine driven
generators
Existing electrical
loads
New electrical loads
ELECTRICAL
Flight control actuation
Landing gear/ Braking
Doors
ELECTRICAL
Cabin pressurisation
Air conditioning
Icing protection
ELECTRICAL
Fuel pumping
Engine Ancillaries
Jet Fuel
Propulsion
Thrust ( 40MW)
Power Sources More Electric Aircraft
• Removal of hydraulic system– reduced system weight– ease maintenance
• “Bleedless” engine– improved efficiency– simplified design
• Desirable characteristics of electrical systems– controllability
• power on demand – re-configurability
• maintain functionality during faults– advanced diagnostics and prognostics
• more intelligent maintenance• increased aircraft availability
More Electric AircraftMotivations
• Removal of hydraulic system– reduced system weight– ease maintenance
• “Bleedless” engine– improved efficiency– simplified design
• Desirable characteristics of electrical systems– controllability
• power on demand – re-configurability
• maintain functionality during faults– advanced diagnostics and prognostics
• more intelligent maintenance• increased aircraft availability
More Electric AircraftMotivations
The “Most” Electric Civil Aircraft Yet
• Boeing 787• Electric environmental control, cabin
pressurisation and wing anti-icing
• Removes need for bleed air from engines
• Still retains a hydraulic system for primary actuation etc
0
200
400
600
800
1000
1200
1400
1600
0 200 400 600 800Ele
ctr
ica
l Syste
m P
ow
er
(kW
)
Aircraft Weight (tons)Conventional aircraft
A380 – slightly
more electric
B787 – much
more electric
20202010200019901980197019601950
100
200
300
400
500
600
700
800
900
1000
VC10
B737
Concorde
Caravelle
A320
B747
A330
A340
A350
A380
B787
Power, kW
Year
B777B757
B767
20202010200019901980197019601950
100
200
300
400
500
600
700
800
900
1000
VC10
B737
Concorde
Caravelle
A320
B747
A330
A340
A350
A380
B787
Power, kW
Year
B777B757
B767
AC Power Generation
• Mechanical Constant Frequency Generation
• Variable Speed generator /Constant Frequency Output
• Variable Frequency Output
Variable speed
Engine Shaft
Generator
Constant Speed
Mechanical Drive
[Gearbox]
Constant
Speed Shaft3-phase
400Hz, 115V
Generator
Power Converter
[DC Link or Cyclo-
converter]
3-phase
400Hz, 115V
Variable speed
Engine Shaft
Generator
3-phase
320Hz to 800Hz
230V or 115V
Variable speed
Engine Shaft
Aircraft Actuation Systems
Flight Control Actuation Systems
PITCHElevators
YAWRudder
ROLLAilerons
Roll spoilers
Trailing Edge Flaps
High Lift / drag
Leading Edge Slats
High Lift (High angle of attack)
Ailerons
Elevators
Rudder
Trimming Tailplane
pitch attitude influence stabilizer
RH & LH Synchronisation
Airbrakes
lift dump + drag
Thrust Reversers
supplement to wheel brakes
Roll Spoilers
supplement ailerons
Electronic
Controllers
Flight Control
• Primary Actuation– Roll - Ailerons on trailing edges of wings
– Pitch - Elevators on trailing edge of tail-plane
– Yaw - Rudder
– Flight critical
• Secondary Actuation– Flaps - Trailing edge of wing
• Used for take off and landing – increase lift at low speed
– Slats - Leading edge of wing, used for same reason as Flaps
– Airbrakes - Spoilers and lift dumpers on wings to increase drag
– Not actually required for flight, but very useful!
Electrically Driven Actuators
• Electro Mechanical Actuator – EMA
• Actuator is moved as motor spins
– Each turn of the motor moves the actuator a fixed amount
– Direct connection between motor and actuator arm
• EMA issues
– Direct drive solution
– Any potential jamming failure modes must be addressed
– Potentially the most compact solution
Power Converter
Electric Motor
BallScrew
3-phase supply
Reduction gearbox
• Electro Hydrostatic Actuator – EHA
• Actuator is moved as motor spins using local Hydraulic system
– Each turn of the motor moves the actuator a fixed amount
– No direct connection between motor and actuator arm
• EHA Issues
– Benign failure modes
– Based on a familiar technology for aircraft component manufactures
– Hydraulic fluid may leak
Power Converter
Electric Motor
3-phase supply
Hydraulic Ram
Fixed Displacement
pump
Electrically Driven Actuators
PEMC Research GroupPEMC Research GroupPEMC Research Group
Electrically Driven Actuators
• EMA– Direct drive solution– Any potential jamming failure modes
must be addressed– Potentially the most compact solution
• EHA– Benign failure modes– Based on a familiar technology for aircraft
component manufactures– Hydraulic fluid may leak
All Electric Aircraft
• Airbus Electric 2-seater
• flies for just 20 minutes
• Solar Impulse
• PV powered Aircraft
• Flew ½ way around the world in 30 days!
All Electric Aircraft
Hybrid and All Electric Propulsion
Series Hybrid
Propulsion
Parallel Hybrid
Propulsion
All Electric
Propulsion
Targets for Aircraft Propulsion
Electrical Machines• Short term (5-10 years) 7-10 kW/kg • Mid Term (10 to 15 years) 10-20 kW/kg • Long Term ( >>15 years) 20 -50 kW/kg
• Longer term goals may have to be achieved through superconducting or newtechnologies.
• Short-Medium term goals likely to be achieved using “more conventional” machines with a strong level of innovation.
Power distribution network cables• Short term (5-10 years) 1 kg/km/A• Mid Term (10 to 15 years) 0,5 kg/km/A• Long Term ( >>15 years) 0,1 kg/km/A
State of the Art Enabling Technologies
• Drivetrain Integration– Mechanical– Power Electronics
• Materials (Devices, Magnetic, Electric, Thermal, Structural)– Exciting improvement using nano
materials
• Machine-drive topologies working at high frequency – High poles/high speed
• Manufacturing – automation, additive– New structures
• Advanced thermal management
Electrical and mechanical integration
High frequency
machines
20kW/L,
SiC converter
Thermal material
integration
Performance Limits
Hybrid Propulsion Systems
Modern Trends in Aircraft Electric Power Systems and in Onboard Electric Power Generation
Engine Propulsion
Fuel Energy Storage
EMEMEMEM EMEM EMEMEMEM EMEMEMEM
TurbineTurbine
Electric Propulsion Electric Propulsion
Electric Starter/Generators
Power Electronic Converters
Battery Electrical Energy Storage
Fuel Cell Electrical Energy Storage
Fast-Responce Electrical Energy
Storage (SuperCap)
Electric Loads (WIPS, EPS, EMA, etc)
EPS control and energy
management
TurbineTurbine
“Single-bus” approach is employed!
Potential TeDP EPS architecture:- gas turbines drive generators, and optionally may act as direct propulsion devices- distributed electrical machines drive propulsion devices- energy storage devices can be used to buffer energy- overall EPS control/energy management
Modern Trends in Aircraft Electric Power Systems and in Onboard Electric Power Generation
High-power machine design for hybrid platforms
- MW-class equipment
- Efficiency/losses become a critical design factor
- High speed gen-sets- Close Integration with GT- Very high power density requirement- Thermally/Mechanically challenged
- Low-speed propulsion motors- Very high torque density- Electromagnetically/Thermally
challenged
Generator
Gas Turbine
Propulsors
EM
EM
Converter
Case 1: Starter/Generator System
Aircraft Starter/Generator
Overall drive system – machine choice
Selected Solution• Slot-Pole Combination – 36-6
• 6 pole to limit switching
frequency loses
• distributed winding
• low rotor losses
• Solid rotor with a CF sleeve retention
• Stiff rotor
• Quasi Hallbach array
• Large airgap = low rotor loses & adoption
of a stator sleeve
8k rpm
19k rpm
32k rpm
motoring
generating
Aircraft Starter/Generator
Power Converter Selection
• Up to 1.6kHz electrical frequency at maximum speed
• Maximum current: 260Arms peak, 270V DC
• Low harmonic content to minimize rotor losses
• Air cooled – significant impact on heat sink weight
2 Level , fs = 20kHz 3 Level , fs= 16kHz Same output
current THD
High Power Density Starter Generator
3-Level NPC drive
Rotor assembly and Low loss laminations
Lightweight Housing Components
E-machine
Helicopter Swash Plate Actuation
Design ConceptSwashplate attachment and EMA arrangement
Jam-tolerant design required due to the jamming risk in ball screw
Redundant EMAs
Requirement to replicate hydraulic system space envelope
Arrangement of 2 EMAs side by side
Hydraulic swashplate actuator arrangement 6 EMAs, each pair
connected to output rods
• Models needed for all the parts of the system
– Reliability– Functional– scalable
Optimisation System Optimisation - models and tools
Parameter Lower Boundary Upper Boundary Unit
Airgap Diameter d 24 35 mm
Split Ratio SR = d/D 0.4 0.6 -
Tooth-width factor 0.5 0.7 -
Fin extension 1 8 mm
Fin thickness 1 3 mm
Fin pitch/thickness 2 8 -
Optimisation with Particle Swarm Optimisation algorithm:
• Simulates behaviour of bird flocks to find optimum of non-linear
functions
• Number of particles with random initial position and velocity
• At each iteration step velocity is
updated with attraction to personal
best particle position
• Efficient optimisation method for
electromechanical problems
• Optimisation with 6 parameters
applied for this design:
dD
L
Particle Projection Evolution of Drive Weight
Optimisation Detailed Design Optimisation
Hardware ConstructionActuator, Motor and Power Converter
Stator
Phase A1
Phase C1
Phase B1
Phase B2
Phase C2
Phase A2
Rotor
Completed Motor
PowerConverter
Short Circuit Motor Current and Drag Torque
Actuatorwith two motors, each motor has two independent stators
Electromagnetic Aircraft Launch Systems for Civil Aircraft
• Electromagnetic Launch (EML) system used
to replace steam catapults on the deck of
aircraft carrier.
• Steam catapult have a number of disadvantages
• Operate without feedback control
• Bulky and heavy
• Highly maintained
• Inefficient (4-6%)
• Adoption of EML in military application was slow
• Recently technical advances have been good for the technology:
• Pulsed power
• Power conditioning
• Energy storage
devices
• Advanced
controls
Electromagnetic Launch Systems
Requirements Data
Aircraft mass 73500 kg
Take-off speed 85.73 m/s
Acceleration 0.60 g
Peak Thrust 502.9 kN
Runway length 624 m
Take-off time 14.57 s
Minimum cycle time 90 s
Electromagnetic Launch Benefits 1
1) Runway length reduction
An acceleration of 0.6G was chosen - compliance with the maximum axial acceleration that a human body can comfortably withstand.
The runway length computed assuming a uniformly accelerated motion to the rotation speed VR plus a safety distance equal to the 25% of the acceleration path.
𝑽𝑹 = Τ𝟏. 𝟎𝟓 𝑽𝟐 𝟏. 𝟏𝟏
Electromagnetic Launch Benefits 2
2) Fuel consumption and exhaust emission reduction
Assume all the energy required to accelerate the aircraft can be saved.
Consider a CFM56-5B4 on the Airbus A320-200, the total fuel burnt during take-off can be computed as
𝐹𝑢𝑒𝑙 𝑏𝑢𝑟𝑛𝑡 = 2 𝑒𝑛𝑔𝑖𝑛𝑒𝑠 ∙ 1.166𝑘𝑔
𝑠∙ 42 𝑠 = 𝟗𝟕. 𝟗𝟒 𝑘𝑔
Considering an airport like Heathrow with 650 flights per day yields
𝐹𝑢𝑒𝑙 𝐵𝑢𝑟𝑛𝑡 𝐷𝑎𝑖𝑙𝑦 = 97.94𝑘𝑔
𝑡𝑎𝑘𝑒 𝑜𝑓𝑓∙ 650
𝑡𝑎𝑘𝑒 𝑜𝑓𝑓
𝑑𝑎𝑦= 𝟔𝟑𝟔𝟔𝟏
𝑘𝑔
𝑑𝑎𝑦
The NOx emission is equivalent of that of 80180 diesel car son daily base
HC CO NOx
Emission indices (g/kg) 0.1 0.5 28.7
Daily emission reduction (kg) 6.37 31.83 1827.07
Electromagnetic Launch Benefits 3
3) Noise Emission reduction
Aircraft engines usually take 4-5 seconds to accelerate from idle to maximum powercondition. The overall noise emission reduction at ground level is expected to be
𝑁𝑜𝑖𝑠𝑒 𝑟𝑒𝑑𝑢𝑐𝑡𝑖𝑜𝑛 =42 − 5 𝑠
42 𝑠∙ 100 = 𝟖𝟖. 𝟏 %
4) Engine size reduction
In the hypothesis of an EML system installation on a large number of airports, the enginerated thrust could be updated to that required during climbing or during emergencyprocedure (approximately 85% of the thrust required at take-off).
This would lead to reduced aircraft drag and weight
EML System Requirements
Requirements F-35C A320-200 Comments
Take-off speed [m/s] 78 70Data taken from references
Aircraft mass [kg] 37000 73500
Acceleration [G] 3.3 0.6F-35C launcher length is set by the dimensions of the aircraft
carrier and the launch acceleration is function of it. The
launcher acceleration for civil application is a requirement and
its length is later determined.Runway length [m] 94 535
Peak thrust [MN] 1.198 0.548 (0.455)Peak Thrust and Launch Energy of military launcher are
calculated considering only aircraft inertia, while those for the
civil application consider the contributions of aerodynamic
drag and ground friction. Inertia contribution is reported
between brackets.Launch energy [MJ] 113 210 (182)
Comparison of launcher requirements for F-35C and for an A320-200 .
Motor Technologies
Superconducting Permanent Magnet Induction
Complex design, costly and significant additional equipment
Linear Permanent Magnet has higher efficiency and
simpler and cheaper. The mover is more robust and lighter.
Expensive, efficiency savingsnot significant in this application
Lacks robustness, may incur magnets demagnetization
Lower efficiency, but this is a system with a low duty cycle
Superconducting linear motor
design
Permanent magnet linear motor performance
Permanent magnet and
induction motors
IntroductionEML?
• Electric Ground Aircraft Launch Systems
• Reduce engine requirements
• Extend maximum flight distances
• Save aviation fuel
• Increase payload
• A different way of thinking…
Landing
• More Electric Aircraft: – Still challenges to address– Flying aircraft a good way to test technology
• All Electric Aircraft – Technology requirements are demanding and
not possible today– Hybrid will be followed by true electric if we can
address all issues
• Electromagnetically assisted aircraft take-off– An out-of-the-box approach– Advantages are many– Infrastructure requirements are daunting!
Thank you!
Recommended