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Background

Research and testing of lidar-assisted control started at University of Stuttgart in 2008 and since then experience on advanced control technologies involving processed lidar measurements has been built up. David Schlipf, head of the Lidar Technology at sowento, has played an important role in the evolution and development of lidar in wind energy applications. Through his research and leading activities in the IEA Task 32, he made his research results public to a broad community and build up a worldwide network. His pioneering work in the field of lidar-assisted control has shaped sowento and is a key business of the company.

Floating wind research is one of the key fields at Stuttgart Wind Energy (SWE). Frank Lemmer, the head of Floating Wind at sowento, was part of these research activities from the early beginnings. His work on reduced-order modeling, integrated design, and controller design for floating wind turbines was awarded in 2019 by the European Academy of Wind Energy. With sowento he continues his work on floating wind turbines on an industrial level.

Controller Design and Implementation

Using Lidars for Wind Energy Control

Current advances in lidar technology provide opportunities to take a fresh look at wind turbine control. The wind is not only the main energy source but also the major disturbance to the control system. Thus, knowledge of the incoming wind is valuable information for optimizing energy production and reducing structural loads. Due to the measurement principles and the complexity of the wind, the disturbance cannot be measured perfectly. This forms a challenging task for estimation and control.

The early beginning of lidar-assisted control

We started our investigations in this area in 2008 within national and European research projects to reduce the structural loads and also to increase the energy yield of wind turbines, both of which make wind energy more competitive. The key challenges have not only been to develop appropriate feedforward control methods applicable to an industrial feedback controller, but also to investigate turbulence characteristics and to derive lidar measurements techniques to provide a usable preview signal. The combination of these findings made the world’s first proof-of-concept of lidar-assisted control possible:

  • Field Testing 2012 together with NREL on the CART3 at NWTC using a commercial lidar system (pulsed, 3 Beams).
  • Field Testing 2012 together with NREL on the CART2 at NWTC using the scanning lidar system developed at SWE.

Advanced field-testing of lidar-assisted control

Since then we refined our experience in several other campaigns:

  • Field Testing 2013 on a commercial wind turbine together with KENERSYS using the scanning lidar system developed at SWE.
  • Field Testing 2013 on the CART3 together with DNV GL, NREL and ZephIR using a continuous-wave lidar system.
  • Field Testing 2015 on the CART2 together with NREL and Avent using a commercial lidar system (pulsed, 5 beams).

If you are interested in our lidar-assisted control expertise, please contact David.

Resources

Contact

David Schlipf, schlipf@sowento.com

Wind Farm Control

With increasing size of wind turbines and the large number of wind farms, nowadays, wind farm control application gets more and more important in reducing the levelized cost of energy (LCOE) from an operational point.  Currently, applying control methods on wind farm level has shown promising results in increasing energy yield but also to provide services for grid applications, like active power control, or derating strategies.

We aim for close collaborations in the field of wind farm control because we think that with our knowledge we can help your project to succeed.

Experiences in wind farm applications

  • design and analysis of field testing campaigns
  • proving concepts
  • realizing of conceptual methods

Lidar measurements in a wind farm

A lidar measurement scan through a wind farm. The wake deficit can be clearly observed in the measurements. (c) Stuttgart Wind Energy, University of Stuttgart

Research projects

During our work at University of Stuttgart we have been part of a EU funded H2020 wind farm control project, CL-Windcon. We have gained experience in simulating wake impingments, designing open-loop and closed-loop controller for flow control and in reduced order modelling of the flow field.

We further participated in a utility-scale wake redirection measurement campaign at the National Renewable Energy Laboratory (NREL) in the US.

If you want to know more, Steffen is looking forward to answering your questions.

Resources

Contact

Steffen Raach, raach@sowento.com

Lidar Applications

New remote sensing techniques like lidar enable new applications in wind energy. We have been constantly involved in leveraging the benefits of the lidar technology. During our academic work we have been heavily involved in leveraging the benefits of remote sensing techniques like lidar in wind energy.

We have been part of several national funded lidar projects during our time at University of Stuttgart . In those we have gained experience in designing meaningful measurement campaigns, developed a research lidar scanner, and investigated wind field reconstruction methods to best leverage lidar data depending on the application.

Measurement campaigns

With pioneering field testing campaigns in lidar-assisted control and the usage of lidar systems in wind energy, we provide a full measurement service to our customers. The main points are:

  • consulting for the selection of lidar devices
  • planning of measurement campaigns
  • data analysis service

Lidar measurements in a wind farm

A lidar measurement scan through a wind farm. The wake deficit can be clearly observed in the measurements. (c) Stuttgart Wind Energy, University of Stuttgart

Lidar Data Processing

Our experience in lidar systems and lidar measurement campaigns enables us to provide data analysis and post-processing services. We provide consulting for lidar data analysis to our customers. Further, input to the interpretation of the measurement results is provided.

With our work our customers get reliable feedback on validity of the measurement campaign and the results.

Floating Wind

Our vast experience in the field of integrated design, optimization and control of floating solutions paves the road to reliable and cost-efficient concepts of the future. Our vision has been a lightweight floating platform built in a modular way to be adapted to various sites.

The photo was taken at the DTU-USTUTT-CENER Triple Spar test campaign at DHI in 2016

  • DTU Wind Energy
  • Danish Hydraulic Institute (DHI)
  • Paper: Yu, W., Lemmer, F., Bredmose, H., Borg, M., Pegalajar-Jurado, A., Mikkelsen, R. F., Azcona, J. (2017). The TripleSpar Campaign: Implementation and Test of a Blade Pitch Controller on a Scaled Floating Wind Turbine Model. In Energy Proceedia.

Integrated design and concept development

Our tools for integrated analyses, control design and optimization allow for a design, adapted to the wind and wave environment, for a rejection of the loads and high damping and stability. We have already designed different controllers and implemented them for real-time testing on experimental models. The results have shown that integrated solutions offer the prospect of significant extreme and fatigue load reductions in operational conditions, especially of the tower and floater structure. The controllers we design do not require more than the standard sensors on an offshore wind turbines and the actuators do not need to be re-designed.

If you are interested in our services, please contact Frank.

Contact

Frank Lemmer, lemmer@sowento.com

References

Since 2009 the team has published a large number of conference and journal publications  in the fields of lidar-assisted control, wind farm control, and floating wind turbine integrated design, optimization and tailored control.

We have participated in several national and international founded research projects and worked together with the international wind energy community on creating innovations and new technologies.

Publications

An excerpt of the publication list is shown below.

Lidar-assisted control:

D. Schlipf, “Lidar-assisted control concepts for wind turbines,” Ph.D. dissertation, University of Stuttgart, 2016. doi: 10.18419/opus-8796.

D. Schlipf, E. Simley, F. Lemmer, L. Y. Pao, P. W. Cheng, Collective Pitch Feedforward Control of Floating Wind Turbines Using Lidar, Journal of Ocean and Wind Energy (JOWE), vol. 2, no. 4, pp. 223-230, 2015, DOI: 10.17736/jowe.2015.arr04.

D. Schlipf, F. Haizmann, N. Cosack, T. Siebers, P. W. Cheng, Detection of Wind Evolution and Lidar Trajectory Optimization for Lidar Assisted Wind Turbine Control, Meteorologische Zeitschrift, vol. 24, no. 6, pp. 565-579, 2015, DOI: 10.1127/metz/2015/0634.

D. Schlipf, J. Mann, P.W. Cheng, Model of the Correlation between Lidar Systems and Wind Turbines for Lidar Assisted Control, Journal of Atmospheric and Oceanic Technology, vol. 30, no. 10, pp. 2233–2240, 2013, DOI: 10.1175/JTECH-D-13-00077.1.

D. Schlipf, P. W. Cheng, Adaptive Feed Forward Control for Wind Turbines, at – Automatisierungstechnik, vol. 61, no. 5, pp. 329-338, 2013, DOI: 10.1524/auto.2013.0029.

D. Schlipf, D. J. Schlipf, M. Kühn, Nonlinear Model Predictive Control of Wind Turbines Using LIDAR, Wind Energy, vol. 16, no. 7, pp. 1107–1129, 2013, DOI: 10.1002/we.1533.

More see here.

Floating wind turbine control:

Lemmer, F., Schlipf, D., & Cheng, P. W. (2016). Control design methods for floating wind turbines for optimal disturbance rejection. Journal of Physics: Conference Series, 753. http://dx.doi.org/10.18419/opus-8906

Lemmer, F., Raach, S., Schlipf, D., & Cheng, P. W. (2015). Prospects of Linear Model Predictive Control on a 10MW Floating Wind Turbine. In Proceedings of the ASME 34th International Conference on Ocean, Offshore and Arctic Engineering. St. John’s/Canada. http://dx.doi.org/10.18419/opus-3959

More see here.

Lemmer, F., Schlipf, D., & Cheng, P. W. (2016). Control design methods for floating wind turbines for optimal disturbance rejection. Journal of Physics: Conference Series, 753. http://dx.doi.org/10.18419/opus-8906

Lemmer, F., Amann, F., Raach, S., & Schlipf, D. (2016). Definition of the SWE-TripleSpar platform for the DTU10MW reference turbine. http://www.ifb.uni-stuttgart.de/windenergie/downloads

Lemmer, F., Raach, S., Schlipf, D. and Cheng, P.W. Parametric wave excitation model for floating wind turbines. Energy Procedia, 2016, link.

Lemmer, F., Raach, S., Schlipf, D., & Cheng, P. W. (2015). Prospects of Linear Model Predictive Control on a 10MW Floating Wind Turbine. In Proceedings of the ASME 34th International Conference on Ocean, Offshore and Arctic Engineering. St. John’s/Canada. http://dx.doi.org/10.18419/opus-3959

More see here.

Awards

The PhD thesis “Lidar-Assisted Control Concepts for Wind Turbines” by David Schlipf was awarded for the best European PhD thesis in 2016 and the 1. Price of Otto F. Scharr Fundation for Energy Technology 2016.

The PhD thesis “Low-Order Modeling, Controller Design and Optimization of Floating Offshore Wind Turbines” by Frank Lemmer was awarded for the best European PhD thesis in 2019.

Resources

Projects

In our research at University of Stuttgart, at Stuttgart Wind Energy (SWE), we participated in several research projects, an excerpt is listed below:

  • EU-projects
    • UpWind
    • FP7-INNWIND.EU
    • H2020-LIFES50+
    • H2020-CL-Wincon
  • national projects
    • Lidar 1&2
    • Baltic
    • Anwind

Resources