Optimizationl.pdf

7/27/2019 Optimizationl.pdf

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Dutch Wind Workshops, October 2010

COST OPTIMIZATION OF PERMANENTMAGNET DIRECT DRIVE GENERATORS

Ir. Anoop Jassal, Dr. H Polinder, TU Delft


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EPPElectrical Power Processing

CONTENTS

Introduction

Motivation

New Design Approach

Challenges

Solution

Conclusion


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1.Introduction


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More energy from wind required in near future

Energy Generators Many Types Possible

INTRODUCTION

DFIG Cheap/need gear box/partial converter Synchronous No gearbox/expensive/full converter/losses PMDD Efficient/reliable/big and expensive/full converter

Offshore ! !


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REQUIREMENTS FOR OFF-SHORE

Large single units Cost control

Low maintenance Accessibility

Cost effectiveness

DIRECT DRIVEENERGY

CONVERSION


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2.Motivation


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MOTIVATION

distribution of costing

29%

10%

1%3%

0%3%12%

25%

15%

2%0%

rotor :

drivetrain:

hydraulic:

nacelle:

cover :

yaw mechanism:

tow er:

generator:

E-system/converter:

transformer :

auxiliary equipment:

Generatorforms a bigpart of the

cost

Source www.elkraft.ntnu.no/norpie/10956873/Final%20Papers/068%20-%20Norpie%20paper.pdf

An Indicative Cost distribution in a Wind Turbine with PMDDGenerator


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MOTIVATION

Distributed Winding

Distributed Winding: Largenumber of coils

-Large Overhangs: Copper Losses

-Insulation is laborious

-High manufacture cost

Source:http://i170.photobucket.com/albums/u260/ben_eberle/IMG_0960.jpg

* PM Magnets are also very expensive* Research focus on only Winding part

Most Conventional machines use distributed windings


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3.New Design Approach


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SOME EXISTING CONCEPTS

Ironless Stator

Newgen Stator Clipper concept Magnetic Bearings

Dewind Variable speed Gearbox

Unison Multibrid

Enercon Direct Drive (Electromagnets)

Zephyros Direct Drive

(Permanent Magnets)


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DESIGN APPROACHES

COST

REDUCTION

Magnetic

Bearings

Reduce

Weight

Modular

Machine

New Gen

Concept

Ironless

Stator

Concentrated

Windings

Clipper Concept,

more no. of small

standard generators

Cooling

Maintenance,reliability

- Large Sizes Difficult to make

- Heat dissipation

- Futuristic

- Cost not evaluated

- Maintenance issues

- Reliability

Concentrated windings can be promising ! !


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1) Shorter overhangs - Less Copper needed and Low Copper Losses.2) Low Number of slots - Lamination cutting reduced.3) Winding Process automatic - Faster manufacture.4) Modular windings Faster Assembly5) Rugged Design

WHY CONCENTRATED WINDINGS ???

Magnets

Rotorback Iron

Stator

Winding

Coil Holder (beforewinding)

View of coil inside the stator.Coil is preformed, Slides on toeach tooth


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DESIGN APPROACH

Change from Distributed Windings to Concentrated Winding Scheme

Distributed Winding Concentrated WindingSource:http://www.theinventory.orconhosting.net.nz/smartdrives/DSC02061_2.JPG

Source:http://i170.photobucket.com/albums/u260/ben_eberle/IMG_0960.jpg


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4.Challenges


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Cogging because of wider teeth (Less slots).

- Machine fails to start- Torque Ripple

Eddy Current Losses in PM Rotor back Iron.- Excessive Heating

- Danger of Demagnetization

Cooling of Machine- If good, Gain More Power for Same Size

- If bad, overheating, reduced life, failure

WHAT DO WE PAY ??

Research Challenges with Concentrated Windings

Research Issue


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COGGING : PM Edge interacts with a tooth, experiences a pull,giving rise to Cogging Torque

Stator Teeth

PM Edge

Movement

CoggingTorqueElement

Rotor

Net Cogging Torque is sumof these cogging torque

elements


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EDDY CURRENT LOSSES : Harmonics and Sub-Harmonics

generated by currents in concentrated windings.

Non-Sinusoidal MMF - High Harmonic Content ! !


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5.Solution Accurate Loss Prediction


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Machine Field Modelinganalytically and then verificationwith Finite Element Method

Eddy Current loss modeling withFE method and Measurement of

these losses For Comparison

Application on various designsand optimize for cost.- Cost Comparison with areference machine

PROCEDURE


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ANALYTICAL MODEL

Magnets

Rotorback Iron

Stator

Winding

X

Y

Z

Region 2; Air with Permeability2

b

B2B4

B5Region 1; Iron with Permeability1

Region 4; Iron with Permeability 4

B1

B3

l

Region 3; Magnet region Permeability 3 and Remanant Flux Density of 1.2 T

B6

B7

ASSUMPTIONS

-Slot less Stator

-Winding = Current Sheet

-No Saturation

-No end effects

ADVANTAGES

-Very Fast

-Good for short-listing

potential designs

( , ) cos( )A x t A kx t


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ANALYTICAL MODEL

1 1 2 2

cosh sinh 0 0 0 0 0

3 3 3 3cosh sinh cosh sinh 0 0 0

4 4 4 4

3 3 3 3sinh cosh sinh cosh

4 4 4 40 0 0

0 0 cosh sinh cosh2 2 2

nkb nkb

nkb nkb nkb nkb

nkb nkb nkb nkb

nkb nkb nkb

2 2 3 3

3 3 4

sinh 02

sinh cosh sinh cosh2 2 2 2

0 0 0

0 0 0 0 cosh sinh sinh4 4 4

sinh cosh cosh4 4 40 0 0 0

nkb

nkb nkb nkb nkb

nkb nkb nkb

nkb nkb nkb

1

1

2

2 3 2

3

3

3 24

0

0

0

(2 )4

0

(2 )4

0

r

r

g

h

gn B

h

n kg

hn B

h n k

Solve some Nasty Equations ! ! !

Analytical Model Cross-Checked with Finite Element Method ! !


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COMPARISON FOR VALIDATION

Flux Lines

Distance along x-axis

Distancealongy-axis

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

Analytical

Finite Element


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ANALYTICAL RESULTS

Quantity Analytical COMSOL Error

Magnet Loss [W] 3224 3193 0.97 %

Back Iron Loss [W] 765 764.6 0.05 %


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FINITE ELEMENT (FE) MODEL

-Using COMSOL

MULTIPHYSICS 3.5a as FEsolver

-Complicated Geometries

Possible

-Motion Possible

-Material Saturation Possible

-Closer to real world scenario

TIME CONSUMING !!


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EXPERIMENTAL WORK

-Compare FE Models with the actual machines for model validation

-Check if we can predict losses with analytical calculation

Test Bench


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FUTURE WORK

Conducting Experiments

Comparison between Analytical-FE-Experimentalresults

Derivation of a cost model

Estimate of cost saving achievable by using newwinding topology

Some design proposals based on research work


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6.Conclusions


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PMDD machines are efficient and reliable but

expensive. One way to lower costs is using concentrated

windings.

Eddy current losses in solid parts of thesemachines are primary concern. Researchneeded for accurate prediction of theselosses.

If designed properly, PMDD generator can bemade cheaper than the conventional DirectDrive generators.


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EPP

STATEMENTS

- In many ways policy makers and economists decide whichproduct(s) dominates the market.

- Cost is of great importance when technology competes.

- Technically best product might not be the most useful product.

Thank you for your kind attention ! !

Documents

Optimizationl.pdf