April 2010

April 2010

Load Transient Analysis Of Wind Turbine Drive Train Under Grid Disturbances

J.Sanz-Corretge, A.García-Barace, I.Egaña

Measurement and Simulation Advances. Hardware. T10.3

Presentation Outline

ACCIONA Windpower 2

1. IntroductionMotivation & Overview

2. Drive Train DescriptionGeneral drive train description

3. Drive Train ModelsFull dynamics & Reduced order models

4. Simulation ResultsVoltage dip simulation

5. Conclusions

Load Transient Analysis Of Wind Turbine Drive Train Under Grid Disturbances. J.Sanz-Corretge, A.García-Barace, I.Egaña

1. Introduction

ACCIONA Windpower 3

• Motivation: several manufacturers have experienced gearbox

failures in the past associated to electrical transient

phenomena.

• Consequence: homologation body (i.e. GL) & electric grid

operator require further analysis on HF dynamics.


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Field Measured Data under Voltage Dip

Frequency (Hz)

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log 1

0(G

en.S

pd)|

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Field Measured Data under Voltage Dip

Frequency (Hz)

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1. Introduction

ACCIONA Windpower 4

• The 2 DOF gearbox model:

• used by GH-Bladed up to now.

• model is a black box.

• does not allow assessment of internal gearbox loads.

• Simulations require the combination of electrical models, mechanical

models, and aeroelastic models, as well as the control system.

• Now, GH-Bladed offers user customizable gearbox model through

a DLL file.


1. Introduction

ACCIONA Windpower 5

• Acciona Windpower defines drive train requirements from

HF transient analysis.

• It takes advantage of

control systems for

mitigating HF loads.

• Current wind turbines:

- AW1500, AW3000

Quality Guarantee - Germanischer Lloyd has certified all the AW models.

AW-3000 Main Components


1. Introduction

ACCIONA Windpower 6

• This work presents:

* Models:

- a new drive train linear model taking into account 34 DOF up to 5 kHz.

- a modal projection-based reduced order model.

- a balanced truncation-based reduced order model.

* Simulation results.


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rotor & hub

clutch & generator

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(1)

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(1)

(15)

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(20)

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(3) (4)

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rotor & hub

clutch & generator

2. Drive Train Description

ACCIONA Windpower 7

• Drive train: all the devices that transmit power from rotor

to generator.

• Mechanical drive train

concept (shafts, gears,…).


2. Drive Train Description

ACCIONA Windpower 8

Features

• Variable speed control of the wind turbine for load mitigation.

• Power transmission with minimum losses.

• Change torque & speed to suitable magnitudes for the generator.

• Robust design due to high availability & low maintenance

requirements.


3. Drive Train Model

ACCIONA Windpower 9

• Desired drive train model must fulfill:

- multibody approach for the drive line in combination of the

rest of the modules.


rotordrive trainmodel DLL

Generator & Power

Electronics

Yaw System, Tower &

Foundation

wind

Externalcontroller

DLL

rotordrive trainmodel DLL

Generator & Power

Electronics

Yaw System, Tower &

Foundation

wind

Externalcontroller

DLL


ACCIONA Windpower 10

Full model

• NL state-space modelling,

• Linearisation around different operating points yield,

• Eigenvalues of A = Natural Frequencies

• Eigenfrequencies of A = Modal Vectors

uxy

uxx

,

,

g

f

uxy

uxx

DC

BA

34 DOF = 68 states, TIME CONSUMING SIMULATIONS!!!

3 days for a 10 min simulation




Full model analysis

Mode Shape, Kinetic Energy and Potential Energy (@160 Hz)


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16-0.2

0

0.2

0.4

0.6MODE SHAPE

DOF

RO

TA

TIO

N

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 160

0.2

0.4

0.6

0.8

1KINETIC ENERGY

DOF

NO

RM

ALI

ZE

D V

ALU

E

ROTOR PR1 PR2 PR3 PS1 PS2 PS3 BUSH SUN HOLLOW1HOLLOW2IMS MESH IMS1 IMS2 HSS MESH HSS COUPLING0

0.2

0.4

0.6

0.8

1POTENTIAL ENERGY

NO

RM

ALI

ZE

D V

ALU

E

Campbell diagram



MPM (Modal Projection-based reduced order Model)

• Modes of very HF are discarded.

• A new state transition matrix is defined from the significant

eigenvectors and eigenvalues.

• Complex damped model, where the state transition matrix

is,

DMKM

I0A

1-1-




MPM PROS (Modal projection-based reduced order model)

• Poles & modes from the original model are kept.

• Residualisation after the truncation leads to perfect steady-state

performance.

MPM CONS (Modal projection-based reduced order model)

• HF residual energy due to modal coupling.




BTM (Balanced Truncation-based reduced order Model)

• The energy of each eigenvector is analysed (Hankel singular

values).

• Only high energy eigenvectors are considered to build a new

state transition matrix.




BTM PROS (Balanced truncation-based reduced order model)

• Main I/O dynamics are kept since only low significant Hankel

values are removed.

• Error quantification.

BTM CONS (Balanced truncation-based reduced order model)

• It leads to slight steady-state errors.


4. Simulation Results



Modelling of the drive train – Gen. Torque to High Speed Shaft Angle

FRF of the MPM

FRF of the BTM

up to 300 Hz

up to 300 Hz




Modelling of the drive train – Gen. Torque to Intermediate Speed Shaft Angle

FRF of the MPM

FRF of the BTM

up to 300 Hz

up to 300 Hz




Modelling of the drive train – Gen. Torque to Planet Shaft Angle

FRF of the MPM

FRF of the BTM

up to 300 Hz

up to 300 Hz

Load Transfer Simulation under Voltage Dip – High Speed Shaft Torque

0

MPM

BTM

Full model

Time [s]







Load Transfer Simulation under Voltage Dip – Intermediate Shaft Torque

0 MPM

BTM

Full model

Time [s]




Load Transfer Simulation under Voltage Dip – Planet Shaft Torque

0 MPM

BTM

Full model

Time [s]




Results summary

Full model MPM BTM

Simulation time 1 1/72 1/72

Steady-state error

None None Yes

HF slope error None Yes None

5. Conclusions



• Fast & accurate load assessment for a parametrised grid

disturbances, with field test validation.

• Important for large wind turbines.

• AW drive train model integrated into the Bladed project allows any

dynamic analysis of the whole wind turbine.

• Lighter component oversizing in comparison with 2 DOF models

computation.

5. Conclusions


• Fast engineering concurrent process.

• Development of control strategies for HF load mitigation. For instance,

An output power limit or torque limit is applied taking into account

the maximum evacuable output power during a voltage dip so that

vibration dampening of the wind turbine transmission system is

feasible (patent pending).


April 2010

Documents

drive train requirements

desired drive train

drive line

new drive train linear

hf transient analysis

introductionacciona

grid disturbancesj

electrical transient