Why Aerospace Needs Power Electronics write up/Power... · The More Electric Aircraft Why Aerospace Needs Power Electronics Prof Pat Wheeler University of Nottingham, Nottingham,

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


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


flight entertainment etc)

Landing gear extension/retraction and steering


“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


4 x 150kVA Wideband VF on turbofan engines

Combination of Hydraulic and Electrical Actuation


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


4 x 40kVA Generators

Combination of Hydraulic and Electrical Actuation

Built 50 Years before the Airbus A380


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


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


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


80kW, 2 channel, switched reluctance generator

Reduces cost, size and weight of whole aircraft

Relies on Power Conversion technologies


A Possible MEA DC Power System Layout Source: Virginia Polytechnic


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


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


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


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


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


• 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


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


• 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


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

http://www.cleansky.eu/

Documents

Why Aerospace Needs Power Electronics write up/Power... · The More Electric Aircraft Why Aerospace Needs Power Electronics Prof Pat Wheeler University of Nottingham, Nottingham,