Certification of Lidar-Assisted Control Applications
Date: 30. – 31. January 2018
Venue: DNV GL, Hamburg, Germany
Workshop leader: Nikolai Hille, DNV GL
Lidar-assisted control (LAC) of wind turbines (WTs) has been an active area of research for over a decade. Both simulation-based studies and field testing campaigns show promising reductions in structural loads as well as increases in energy production using feedforward control relying on preview measurements of the approaching wind field. However, LAC has not become widely adopted by the wind industry yet. One of the most significant barriers to the widespread adoption of the technology is that guidelines for certifying WTs with LAC have not been established. Without clear design standards for WTs using LAC, it is difficult for wind turbine manufacturers to fully assess the value creation of the control technology and move forward with including it in a commercial turbine design.
The workshop “Certification of Lidar-Assisted Control Applications” brought together lidar manufacturers, wind turbine manufacturers, research organizations, and certification bodies to develop suggestions for guidelines for type certification of WTs with LAC. Led by Nikolai Hille from DNV GL, supported by Eric Simley from Envision Energy and held at the DNV GL offices in Hamburg, the workshop was organized as a 2-day event. Day 1 began with an overview of type certification and how it is affected by LAC. The afternoon was devoted to presentations by the four stakeholder groups, all answering the question “what are the challenges for type certification with LAC?” On Day 2 the participants split into four working groups, rotating through four different stations, each hosted by an expert moderator, covering the following topics relevant to certification with LAC:
- The lidar system (Steffen Raach, sowento)
- Simulation models and load simulations (Claudia Meyer and Johan Olaison, DNV GL)
- Control and protection system (Reinhard Schleeßelmann, DNV GL)
- Prototype measurements (Andrew Scholbrock, NREL)
For each topic, the groups brainstormed and formulated ideas answering the question “how should we certify wind turbines with LAC?”
A variety of ideas were generated by the working groups along with new questions raised, with several themes emerging. One challenge highlighted is the certification of WTs using LAC for extreme load reduction. Because 100% lidar availability is unlikely, ensuring that either the lidar is functioning properly or the turbine is operating in a “safe mode” when extreme wind conditions occur is critical. Another topic addressed is how to reconcile site-specific lidar properties affecting LAC with more general WT type certification. Wind turbines are type certified for a specific wind class, but lidar availability, with implications for controller performance, depends on additional atmospheric conditions. Further themes addressed include the need for clarity in modeling lidar preview measurements in the extreme wind fields used for certain design load cases, as well as procedures for verifying the performance of the lidar and lidar-assisted controller during prototype testing. Lastly, one overarching point that was raised is that guidelines for certification of WTs with LAC should remain as general as possible and only address areas where LAC presents unique challenges not covered by existing design standards.
The ideas formulated during the workshop are being incorporated by some of the workshop participants into a document “Best Practices for Certification of Lidar-Assisted Control Applications,” which will be made available on the Task 32 website when complete. The content of this Task 32 document will be used by DNV GL as they create their guidelines on certifying WTs with LAC, planned for later in 2018.
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Photos by SWE and sowento.