hybrid wave tank testing of floating wind turbines€¦ · wave tank testing of floating wind...

HYBRID WAVE TANK TESTING OF FLOATING WIND TURBINES

Vincent Arnal, Jean-Christophe Gilloteaux, Félicien Bonnefoy, Sandrine Aubrun

LHEEA, Ecole Centrale de Nantes, France

115th EAWE PhD Seminar - 31/10/2019


OUTLINE

• Wave tank testing of floating wind turbines

• Presentation of the hybrid testing system

• Ongoing and future wave tank tests

3

Wave tank testing of floating wind turbines

Why including aerodynamics loads ? Mean positions Influence of Controler Aerodynamic damping Additionnal excitation

Objective? Validation of the design (Floater, moorings, …) Validation and calibration of numerical models

𝐹𝑎𝑒𝑟𝑜


4

Wave tank testing of floating wind turbines


Drag diskGeometry

scaled rotorThrust matched

scaled rotor

100% physical

MeanThrustforce

Unsteadyaerodynamicforce

Test of Control strategies

Actuatorresponsetime

Scalability to large rotor (10-15 MW)

Porous Disk + + - - - - -

Geometry scaled rotor + - - ++ -

Thrust Match rotor ++ - - ++ -

Wind

Reynolds

Wave

Froude

Hybrid with actuators

Wind generation system performance at Ecole Centrale de Nantes

Blade Pitch control

Rotor Nacelle Assembly

5

Real-Time Hybrid model testing - Principle:

Physic → Numeric

Motions of

Platform and tower

Physic ← Numeric

Rotor Force (Aero, Gyro, Inertia...)

Full scale :Simulation of a wind turbine :Wind + Aero + Servo + ElasticAdapted OpenFAST

Model Scale:Waves + Platform + Tower + Moorings+ Actuators

Motions

RNA Force

©SINTEF Ocean (Thys, 2018)


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Wave tank hybrid testing of FWT : actuators


SINTEF Ocean 6 cables(Chabaud, 2016);(Sauder et al., 2016);...

SOFTWIND Project

Purpose: Development of an experimental platform based on a hybrid approach for the wave tank testing of floating wind turbines.

Objectives: • Accurate and robust experimental platform• Test of innovative control strategies developed by the SME D-Ice Eng

On-land

IH Cantabria 6 on-board fans(Urbán and Guanche, 2019); (Battistella et al., 2018)

On-board

Bandwidth ??

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SOFTWIND Hybrid system

Wave tank

2C Force transducer

Actuator (s)

Floater

Mast

ESC

Motion Capture system

Accelerometer

Host PC

Wind turbine Simulation

FAST code

NI CompactRIO controler

Actuator command

Data acquisition

Dry


6 DoF Hexapod

Dry

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TEST BENCH Validation of the methodology

Overall validated methodology1. Realistic FWT motions 2. Motions reproduced by Hexapod3. Motions capture4. Force computed in real-time by integrated

numerical code5. Actuator commanded to reproduce this force

Success Indicators :• The real-time computed force corresponds

to the load case we are reproducing.• The actuator reproduces with a sufficient

accuracy the setpoint force.

𝐻𝑠[m]

𝑇𝑝[s]

𝑈𝑤[m/s]

Mean thrust

[kN]

LC1 3 5 11.4 680

LC2 4 5 18 320

LC3 6 10 11.4 680

LC4 7 10 18 320

LC5 7 17 11.4 660

LC6 8 17 18 320

OC3 Hywind Spar – 5MW scale 1:30• Rigid blades and tower• Active controler

Name of FWT OC4_Semi OC3_Spar TripleSpar_10MW

Representative

picture

[14] [17] [15]

Wind Turbine NREL-5MW [18] NREL-5MW [18] DTU-10MW [19]


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OC3 Hywind Spar – 5MW at scale 1:30Waves conditions : Severe Sea State, 𝐻𝑠 = 8.6𝑚 𝑇𝑝 = 13𝑠;

Wind conditions : Normal Turbulence Model, 𝑈𝑤 = 18𝑚. 𝑠−1; 𝑇𝐼 = 14.6%;

3P

Waves

Improvement with the use of inverse dynamicsBut still 30 ms pure delay

TEST BENCH Validation of the methodology


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Calibration / characterization : • Modal frequency, • Structural damping• Stiffness

Challenge : Measure relative flexible towermotions (small amplitude and high frequency) Use Inertial Measurement Units and Motion Capture system (Kalman filters)

Structure to limite weight effectsof the cables

Moving to wave tank tests: 1. Flexible tower at scale 1:40

Flexible MAST


Qualysis markers

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Calibration / characterization : • Wind turbine tower modal frequency• Evaluation of structural damping• Evaluation of mast stiffness


Moving to wave tank tests: 1. Flexible tower at scale 1:40

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Floating fish farm with a 10MW turbine : (October 2019)

SPAR with the DTU 10MW RWT (Nov. – Dec. 2019)

Under construction!!


Moving to wave tank tests: 2. Ongoing experiments


CONCLUSION

• Development of a hybrid wave tank testingmethodology Implementation and validation of the

communication

• Actuators Selection Identification of performances Command improvements

• Wave tank tests Additionnal complexity with flexible mast Ongoing !


SOFTWIND project: Schedule

THANK YOU FOR YOUR ATTENTION

15th EAWE PhD Seminar - 31/10/2019 15

16

Loads acting on a RNA


𝐹𝑠𝑒𝑡 =

𝐹𝑎𝑒𝑟𝑜 𝑥𝐹𝑎𝑒𝑟𝑜 𝑦𝐹𝑎𝑒𝑟𝑜 𝑧0

𝑀𝑎𝑒𝑟𝑜 𝑦

𝑀𝑎𝑒𝑟𝑜 𝑧

+

000

𝑀𝑥 𝐿𝑆𝑆 𝑟𝑖𝑔𝑖𝑑

00

+

0000

𝑀𝑔𝑦𝑟𝑜 𝑦

𝑀𝑔𝑦𝑟𝑜 𝑧

+

𝐹𝐼𝑛𝑒𝑟𝑡𝑖𝑎 𝑓𝑙𝑒𝑥 𝑥

𝐹𝐼𝑛𝑒𝑟𝑡𝑖𝑎 𝑓𝑙𝑒𝑥 𝑦

𝐹𝐼𝑛𝑒𝑟𝑡𝑖𝑎 𝑓𝑙𝑒𝑥 𝑧

𝑀𝐼𝑛𝑒𝑟𝑡𝑖𝑎 𝑓𝑙𝑒𝑥 𝑥

𝑀𝐼𝑛𝑒𝑟𝑡𝑖𝑎 𝑓𝑙𝑒𝑥 𝑦

𝑀𝐼𝑛𝑒𝑟𝑡𝑖𝑎 𝑓𝑙𝑒𝑥 𝑧

Aerodynamics Aerodynamicsand free rotor

speed

Inertia Rotor –rotating= Gyro

Inertia Rotor - flexible

Rotor Nacelle Assembly

RNA Physical model Numerical modelGravityInertial | 6 DOF platformInertial | flexible towerInertial | flexible bladesInertial | rotating blades (gyroscopic)AerodynamicsFree rotor speed

ElastoDyn outputs fromOpenFAST v2.1

MethodologySpecifications of actuators setpoints :

Preliminary analysis of the characteristics of the aerodynamic tensor based on numericalsimulations of:

For Norm Design Load Cases of type 1.X (power

production)

Severe waves Normal Turbulence Model Wind-wave misalignment

3 different FOWTs: • OC4 semi submersible (5MW)• OC3 Hywind (5MW)• Triple Spar (10MW)

Analysis of the relative contributions of the different frequencies of interest=> Standard deviations of the aerodynamic load components by frequency bandwidth

15th EAWE PhD Seminar - 31/10/2019 17

hybrid wave tank testing of floating wind turbines€¦ · wave tank testing of floating wind...

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