the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Feedforward pitch control for a 15-MW wind turbine using a spinner-mounted single-beam lidar
David Schlipf
Alfredo Peña
Abstract. Feedforward blade pitch control is one of the most promising lidar-assisted control strategies due to its significant improvement in rotor speed regulation and fatigue load reduction. A high-quality preview of the rotor-effective wind speed is a key element to control benefits. In this work, a single-beam continuous-wave or a pulsed lidar system is simulated in the spinner of a bottom-fixed IEA 15 MW wind turbine. The single-beam lidar can rotate with the wind turbine rotor and scan the inflow with a circular pattern, which mimics a multiple-beam nacelle lidar at a lower cost. Also, the spinner-based lidar has an unimpeded view of the inflow without intermittent blockage from the rotating blade. The focus distance and the cone angle of the spinner-based single-beam lidar are optimized for the best wind preview quality based on a rotor-effective wind speed coherence model. Then, the control benefits of using the optimized spinner-based lidar are evaluated for an above-rated wind speed in OpenFAST with an embedded lidar simulator and virtual four-dimensional Mann turbulence fields considering the wind evolution. Results are compared against those using a single-beam nacelle-based lidar. We found that the optimum scanning configurations of both CW and pulsed spinner-based single-beam lidars lead to a lidar scan radius of 0.6 of the rotor radius. Also, results show that a single-beam lidar mounted in the spinner brings much more control benefits (i.e., better rotor speed regulations and higher reductions of the damage equivalent loads on the tower base and blade roots) than the one based on the nacelle. The spinner-based single-beam lidar brings similar performance as a 4-beam nacelle lidar when used for feedforward control.
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Wei Fu et al.
Status: open (until 06 Oct 2023)
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RC1: 'Comment on wes-2023-94', Alan Wai Hou Lio, 18 Sep 2023
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The paper presents a comprehensive study of a spinner-mounted single-beam LiDAR and its application for feedforward control. The authors demonstrate that the spinner-mounted LiDAR shows a higher measurement coherence bandwidth (MCB) compared to a nacelle-based single-beam LiDAR. Furthermore, they highlight that its feedforward control advantages surpass those of a nacelle-based single-beam LiDAR and may even be on par with a nacelle-based four-beam LiDAR system.
The paper is very well-written and the structure is well-organised. The subject matter is highly relevant to the readers of Wind Energy Science. I found it enjoyable to read. I have only a few minor technical corrections to share.
- “In this work, a single-beam continuous-wave or a pulsed lidar system is simulated in the spinner of a bottom-fixed IEA 15 MW wind turbine.” - Maybe rephrase this because, from my understanding, both continuous-wave and pulsed lidar were considered in this work.
- Page 11. “(in our case 0.025 Hz)” How did you know this number?
- Page 11. Equation 31. Please state the assumptions. For example, it is a direct-drive design (no gearbox ratio), with no electrical conversion efficiency.
- Page 11 Line 279. “Thus, a feedforward pitch rate θ˙FF can be calculated using the derivation of the static pitch curve (see Schlipf, 2016… )” I think in David’s work, he computed the pitch rate using the derivative (d \theta/dv) and the derivative of the wind speed, and also imposed a limit on the d\theta/dv. Did you do the same in this article?
- Page 12. Line 297. “… for frequencies lower than 0.04 Hz …” How did you end up in this number? Can you elaborate?
- Page 12. Equation 33 and 34. The integral bound is “t” and the variable of integration is also “t” as in the symbol “dt”, which is not right. Maybe change the differential of the variable to “d\tau”.
- Page 12, Line 290. “…kp is the proportional gain, KI the integral gain…” Why is it that one is capitalised while the other is not?
- Page 12 Line 290. “ΔΩ = ΩG,rated−ΩG” It should be \Delta Omega = Omega_G - Omgea_G,rated, unless the Kp and Ki are negative.
- Section 4. This optimisation of LiDAR configuration was only conducted for one turbulence intensity? and one mean wind speed with 21 seeds?
- Page 15. Line 366. “GΩuLL is the closed-loop transfer function from the REWS to the rotor speed,” Is the transfer function obtained from OpenFAST or just a simplified 1DOF drive-train/rotor model with the PI controller? If it’s from OpenFAST, does it include all the structural dynamics and how many system states are there?
- Section 5. Regarding the simulation, was the LiDAR implementation considered the blockage of rotating blades in OpenFAST, which was stated as the benefit of the proposed LiDAR in the abstract? I wonder how much having a clear view (without the blockage) would influence the MCB.
Citation: https://doi.org/10.5194/wes-2023-94-RC1
Wei Fu et al.
Wei Fu et al.
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