novel pm generators for large wind turbines - sintef - … · 2014-11-17 · novel pm generators...

Novel PM generators for large

wind turbines

by Alexey Matveev

Wind Power R&D seminar - Deep sea offshore wind power, 20-21 January 2011, Trondheim, Norway

18.01.2011 2

Contents

• Drive train configurations

• State-of-the-art PMG-based solutions

• Integration: the path to win for direct drive

• SmartMotor in wind

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The general drive train scheme

G

Nacelle and tower

Grid

C TP

BGB

GB – gearboxB – brakeG – generatorC – converterT – transformerP - protection

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Basic drive train solutions

Configuration 1: gear + double-fed IG

Configuration 2: gear + IG

Configuration 4: gear + PMSG

Configuration 3: direct SG with wound rotor

Configuration 5: DD PMSG

Efficiency of different drive trains

• Components included: gearbox, generator, converter, transformer– Direct driven PM generator solution gives the best efficiency at speeds below rated

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Analysis performed in cooperation with Zhaoqiang Zhang, NTNU (supervisor Prof. Robert Nilssen)

LS – low speedMS – medium speedHS – high speed

PMSG – permanent magnet synchronous generatorDFIG – doubly-fed induction generatorEESG – electrically excited synchronous generatorSCIG – squirel-cage induction generator

60,00 %

65,00 %

70,00 %

75,00 %

80,00 %

85,00 %

90,00 %

95,00 %

100,00 %

3 5 7 9 11 13 15

MS_PMSG HS_PMSG

HS_DFIG MS_EESG

HS_SCIG HS_EESG

LS_PMSG LS_EESG

Wind Speed (rpm)

Eff

icie

ncy

• Direct drive is larger and heavier, but

• it doesn’t suffer gearbox-related problems

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Direct drive vs geared solution

Source: NTNU

turbine

gear

generator

• High-torque generator for direct drive is large. This is basically the only drawback of direct drive solution

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High-torque generator for direct drive

PM generator from Siemens. 3 MW, 17 rpm

• Drive trains with PM generators have the best efficiency– Especially without gear (direct drive) and 1-stage gear

• However, there are other characteristics to take into account:– Weight– Cost– Power factor– Lifetime– Reliability– Manufacturability– ...

• Design means finding a trade-off between various criteria

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Some conclusions

Efficiency

cos_fi

P/kg

T/kg

1/Length

Tan. tensionDesign 1

Design 2

Design 3

Design 4

Design 5

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...next part

• Drive train configurations

• State-of-the-art PMG-based solutions

• Integration: the path to win for direct drive

• SmartMotor in wind

18.01.2011 10

Available solutions with PMG

Low-speed PMG (DD) Medium-speed PMG (1-s.g.)

High-speed PMG (3-s.g.)

• Low-speed, medium-speed and high-speed generators

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Products of ABB and TheSwitch

<3.3 MW <300 rpm

<4.25 MW <20 rpm

<1 MW <2000 rpm

• Examples of medium-voltage (ABB) and low-voltage (TheSwitch) converters

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Commercial power electronics

ABB TheSwitch

Is it end of the story?

• Big companies have products and even complete packages up to approximately 5-7 MW. Is it end of the development?

NO!!!

• New concepts under investigation, for example:– Magnetic gears and Pseudo-direct drive

– Superconducting machines

• There are problems when going to powers higher then 5-7 MW. These are to be solved!

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• Magnetic gears, pseudo-direct drive (PDD), superconducting machines

• The concepts have not been proven yet for high-power WEC

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Examples of new concepts

Magnomatics Converteam/Zenergy

PDDMagnetic gears Direct drive using HTS superconductors

Technology frontier for PM generators

• State-of-the-art in generator weight (expressed via power and torque densities, each point corresponds to one generator design)

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0,00

50,00

100,00

150,00

200,00

250,00

300,00

350,00

400,00

450,00

1,00 10,00 100,00

<1.5 MW

1.5-2 MW

2-3 MW

3-4 MW

>4 MW

Superconducting

Some new designs

Po

wer

Den

sity

(W

/kg)

Torque Density (Nm/kg)

Area of state-of-the-art designs

TheSwitch 4,25 MW DDSiemens 3,6 MW DD

TheSwitch 3,3 MW geared

ABB 2 MW 3-stage gear

Analysis performed in cooperation with Zhaoqiang Zhang, NTNU (supervisor Prof. Robert Nilssen)

• Active parts make 30-40% of total weight

• Cooling system defines size of active parts, it may take considerable space

• Carrying structure is usually massive

16 16

~60

00

~1000-1500

<30000 kg

Active parts, cooling and carrying structure

TheSwitch

When going for higher powers...

• Weight of carrying structure grows disproportionally!

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Source: TU Delft

Enercon

• Drive train configurations

• State of the art PMG-based solutions

• Integration: the path to win for direct drive

• SmartMotor in wind

18.01.2011 18

...next part

Integration strategies

• For drive trains with gearboxes: integrate generator with gearbox (see examples below)

• For direct drive: integrate generator with the turbine! (examples will follow)

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TheSwitch ABB Magnomatics

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Direct-driven generator in the nacelle

• Just a few of numerous patented designs

• Popular concept: generator between blades and tower

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Direct-driven generator in the nacelle

MTorres

Northwind Mervento

Vensys

• Integration variants

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Direct-driven generator in the nacelle

Source: NREL

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Direct-driven generator outside the nacelle

Bearing

Outer rotor

Inner stator

Emergia

• No shaft• Single bearing common for generator and blades

• Different approaches to weight reduction

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Direct-driven generator outside the nacelle

Concept: light carrying structure of the generator

Concept: integration of generator with blades

Key to success for generator supplier

• Work in close contact with the turbine designers

• Provide best active parts– Lightest

– Most compact

– Giving high efficient energy conversion

– Segmented

– Easy to integrate

– Cheap in production

– With low cogging

– Medium- and low-voltage

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...next part

• Drive train configurations

• State of the art PMG-based solutions

• Integration: the path to win for direct drive

• SmartMotor in wind

18.01.2011 27

What is SmartMotor

• Established in 1996 in Trondheim, Norway

• One of the largest R&D groups in the world with focus on PM technology

Reference projects offshore

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• Low-voltage and medium-voltage machines of MW-class

1.1 MW tidal turbine of Atlantis Resource Corporation (delivered)

0.8 MW propulsion system for Rolls-Royce Marine (in operation)

10 MW offshore wind turbine of SWAY (under construction)

29

The technologies we believe in

• PM machines with concentrated winding and ironless machines

• Ideal for high-torque applications like wind turbines with direct drive

NTNU

Our technologies

• Concentrated winding technology is advantageous compared to distributed winding in high-torque applications due to– higher slot fill factor and consequently better cooling of the copper

Pre-shaping of the coil No insulation is needed between different phases

– segmentation with distributed winding leads to half-empty slots (10% loss in total slot filling), while with concentrated winding all slots are filled

– low cogging Competitors achieve this by shaping magnets SmartMotor apply patented slot/pole combinations

• Ironless technology is advantageous for machines with large diameter– There is no attracting force between rotors and stator– The structure is not sensitive to relative displacement of rotors and stator

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Our R&D directions

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• Shift PMG technology frontier by introducing new concepts

• Find new integration solutions together with wind turbine manufacturers

0

100

200

0 30 60

Pow

er p

er w

eigh

t [W

/kg]

Torque per weight [Nm/kg]

Enercon 4.5 MW

Siemens 3.6 MW

TheSwitch 4.2 MW

Siemens 3.0 MW

Vensys 1.5 MW

0

32

1

0

1

2

3

State-of-the-art

New active parts (NAP)

NAP+mech. integration

MAG-concept

Our R&D directions

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• Novel transformer-less concepts• ABB have developed concepts with direct high-voltage DC outputs based

on use of machines with high-voltage insulation• SmartMotor have developed similar concept where machine with low-

voltage insulation can be used (which means considerably more compact and cheap machine)

ABB concepts

18.01.2011 33

...the end)

Thank you!

Contact information: alexey@smartmotor.no, www.smartmotor.no