Dynamic Transmission Response of a Hydrostatic Transmission Results measured on a Test Bench J. Schmitz, N. Diepeveen, N. Vatheuer 18.04.2012.

Dynamic Transmission Response of a Hydrostatic Transmission

Results measured on a Test Bench

J. Schmitz, N. Diepeveen, N. Vatheuer18.04.2012

5 10 15 200

100

200

300

2 of 19Dynamic Response of a Hydrostatic TransmissionJ. Schmitz, N. Diepeveen, N. Vatheuer

Englisch

Outline

Introduction

System design & Control strategy

Efficiency measurements

Dynamic measurements

Conclusion / Outlook


Englisch

Drive train is a key component in a wind turbine

Market is dominated by two concepts

Why developing a hydrostatic system?- Hydrostatic transmission is continuously variable

- No frequency converter required

- Compactness and good damping

Introduction

Radial piston pump Axial piston

motor

Efficient, robust andcost effective drive train


Englisch

Outline

Introduction






Englisch

Optimized configuration for 1 MW

generator 1

generator 2

generator 1

generator 2

generator 1

generator 2

321

Two hydraulic circuits

Three different modes of operation

Components- 2 pumps (70 & 280 kNm)

- 3 variable displacement motors

- 1 constant motor

- 2 generators

Single motors can beswitched off

Big pump and one generatorcan be switched off


Englisch

Integration into the test bench

Hydrostatic transmission

generator 1

generator 2

Hydrostatic transmission

motor 1

motor 2

Challenges- High torque at low speed

- Dynamic loads

- Limited electrical power

Test bench layout- Hydrostatic power feed-back

- Generators replaced by electrical motors and axial piston pumps

- Turbine simulated by radialpiston motor

- Controlled by variable displacement pumps


Englisch

Test bench drive Hydrostatic transmission

Test bench in the IFAS laboratory


Englisch

Optimal points of operation

Captured power can be optimized by adjusting the rotation speed

Optimal point of operation does not have the maximum torque

02.5

57.5

1012.5

15

010

2030

40

050100150200250300350

torq

ue [

kNm

]

02.5

57.5

1012.5

15

010

2030

40

0

200

400

600

800

1000

po

we

r [k

W]

Power Torque

For a given wind speed


Englisch

02.5

57.5

1012.5

15

010

2030

40

050100150200250300350

torq

ue [

kNm

]

02.5

57.5

1012.5

15

010

2030

40

050100150200250300350

torq

ue [

kNm

]

02.5

57.5

1012.5

15

010

2030

40

050100150200250300350

torq

ue

[kN

m]

windT loadT

Torque balance on the turbine‘s inertia

0 3 6 9 12 15wind speed [m/s]

05

101520253035

rota

tion

sp

ee

d [

rpm

]

0 50 100 150 200 250 300time [s]

0

5

10

15

win

d s

pe

ed

[m

/s]

0

5

10

15

05

1015

2025

3035

0

100

200

300

400

torq

ue

[kN

m]

accelerationdeceleration

ITT loadwind

Torque from wind Braking torque transmission

Braking torque is independent from wind speed


Englisch

Hydrostatic Transmission

motor

windT

RotorI

controller rotation speed

-

P

ω

controller load torque

Simulation of wind turbine environment

loadT

Real-Time Simulation

Test bench

Inertia of turbine is modelled in real-time simulation

Test bench drive transfers rotation speed to the test bench

Measured braking torque is applied on simulated turbine


Englisch

Outline

Introduction






Englisch

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32

rotation speed [rpm]

0102030405060708090

100ov

eral

l effi

cien

cy [%

]

Measurement result of overall efficiency

generator 1

generator 2

generator 1

generator 2

generator 1

generator 2

Procedure of measurement- Transmission controller set rotation speed

- Torque applied dependent on rotation speed

Results for different configurations


Englisch

Outline

Introduction






Englisch

Analysed load cases

Two different load cases- Torque step

- Gust of wind (Mexican hat)

Two different control strategies- Fixed displacement of motors

- Torque control depending on rotation speed

Torque files generated withindustry standard software“Bladed” by TU Delft


Englisch

Control enables the turbine to accelerate

Torque increases with rotation speed

Result of measurement with torque step

Constant motor displacement Torque controlled transmission

Torque increases rapidly

Rotation speed slightly increases due to increasing leakage


Englisch

Result of measurement result with gust of wind

Constant motor displacement Torque controlled transmission

Torque peak is smoothened

Inertia of turbine acts as flywheel

Torque curve follows torque from wind with short delay

Overshooting braking torque


Englisch

Outline

Introduction






Englisch

Conclusion

generator 1

generator 2

0 3 6 9 12 15wind speed [m/s]

05

101520253035

rota

tion

sp

ee

d [

rpm

]

0 50 100 150 200 250 300time [s]

0

5

10

15

win

d s

pe

ed

[m

/s]

0

5

10

15

05

1015

2025

3035

0

100

200

300

400

torq

ue

[kN

m]

accelerationdeceleration

Only pilot plant can convince developers and verify cost of energy

Hydrostatic drive train can be adapted toWEP power-curve

Optimal efficiency even at partial load

Variable transmission ratio No frequency converter required

Torque control based strategy provides compromise of- Adjusting rotation speed

- Robust and reliable operation


Englisch

Transmission on test bench Pilot plant

Outlook

VDMA

Research project funded by VDMA, Fluid Power Research Fund

Research Project

Self-sufficient operation on test bench

- Installation of required periphery

- Development of controller

Form consortium to realize pilot plant ( ~ 900 kW)

Hydraulic companies

Wind turbine manufacturer

Thank you for your attention.

Questions, Suggestions?

J. Schmitz, N. Diepeveen, N. Vatheuer18.04.2012

5 10 15 200

100

200

300


Englisch

Outlook: proposal for multi-megawatt turbine

Doubling the power four times more pump displacement

Hydraulic pumps are not available yet Approach: Upstream mechanical

transmission

Challenge with multi-megawatt transmissions

Mechanical ratio: 4.5 Four independent hydraulic modules 1.25 MW per module

5-MW-Concept

Combining the benefits of mechanical and hydraulic drive trains

Dynamic Transmission Response of a Hydrostatic Transmission Results measured on a Test Bench J. Schmitz, N. Diepeveen, N. Vatheuer 18.04.2012.

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