LIDAR-Assisted Exact Output Regulation for Load Mitigation in Wind Turbines

Optimising wind turbine performance involves maximising energy harvesting while seeking to minimise load fatigues on the tower structure, blades and rotor. To improve turbine control performance, wind preview measurement technologies such as Light Detection And Ranging (LIDAR) have been a point of interest for researchers in recent years. In this paper, we explore the application of a classical control methodology known as Exact Output Regulation (EOR) for improving the control performance of a LIDAR-enhanced wind turbine. The EOR controller is designed to achieve the rejection of known input disturbances, while also ensuring the system output tracks a desired reference signal. The controller is comprised of a state feedback controller together with a feedforward gain. The LIDAR wind preview information is used to obtain a low-order exosystem for modeling wind dynamics. This wind exosystem is used to obtain the feedforward gain matrix that enables the EOR controller to effectively reject the input disturbance and achieve the desired reference tracking. Extensive simulations of the EOR controller with a broad range of wind speeds in both partial load and full load operating regions are performed on the full nonlinear aero-elastic model of the National Renewable Energy Laboratory (NREL) 5 MW reference wind turbine. For performance comparisons, we also implement a baseline torque controller and a commonly used feedforward control method known as Disturbance Accommodation Control (DAC). The results show that, in comparison with a baseline and DAC controller, the EOR controller can provide substantially improved reduction of fatigue loads and smoother power output, without compromising energy production levels.

[1]  Po-Wen Cheng,et al.  Optimization of a feed-forward controller using a CW-lidar system on the CART3 , 2015, 2015 American Control Conference (ACC).

[2]  Robert Schmid,et al.  Nonovershooting and nonundershooting exact output regulation , 2014, Syst. Control. Lett..

[3]  Amin Mahdizadeh,et al.  Comparison between the NMPC and EOR control of wind turbines using LIDAR wind measurements , 2018, Journal of Physics: Conference Series.

[4]  Karl Stol,et al.  Disturbance Tracking and Blade Load Control of Wind Turbines in Variable-Speed Operation , 2003 .

[5]  Po-Wen Cheng,et al.  Direct Speed Control using LIDAR and turbine data , 2013, 2013 American Control Conference.

[6]  O Hugues-Salas,et al.  Wind turbine control applications of turbine-mounted LIDAR , 2014 .

[7]  Brian R. Mace,et al.  Wind turbine blade optimisation with individual pitch and trailing edge flap control , 2017 .

[8]  D. Oetomo,et al.  Fatigue load mitigation in multi-megawatt wind turbines using output regulation control , 2017, 2017 21st International Conference on System Theory, Control and Computing (ICSTCC).

[9]  B. Jonkman.  Turbsim User's Guide: Version 1.50 , 2009 .

[10]  Alan Wright,et al.  Adding feedforward blade pitch control to standard feedback controllers for load mitigation in wind turbines , 2011 .

[11]  Kathryn E. Johnson,et al.  Comparison of Strategies for Enhancing Energy Capture and Reducing Loads Using LIDAR and Feedforward Control , 2013, IEEE Transactions on Control Systems Technology.

[12]  F. Dunne,et al.  LIDAR Wind Speed Measurement Analysis and Feed-Forward Blade Pitch Control for Load Mitigation in Wind Turbines , 2011 .

[13]  Mahmood Mirzaei.  Wind Turbine Control: Robust Model Based Approach , 2012 .

[14]  Jason Jonkman,et al.  FAST User's Guide , 2005 .

[15]  Kathryn E. Johnson,et al.  Lidar-assisted wind turbine feedforward torque controller design below rated , 2014, 2014 American Control Conference.

[16]  N. Kelley.  A Case for Including Atmospheric Thermodynamic Variables in Wind Turbine Fatigue Loading Parameter Identification , 1999 .

[17]  Jie Huang,et al.  3. Nonlinear Output Regulation , 2004 .

[18]  Denny Oetomo,et al.  Enhanced energy capture of wind turbines by exact output regulation , 2017, 2017 IEEE 56th Annual Conference on Decision and Control (CDC).

[19]  Ali Saberi,et al.  Control of Linear Systems with Regulation and Input Constraints , 2000 .

[20]  J. Jonkman,et al.  Definition of a 5-MW Reference Wind Turbine for Offshore System Development , 2009 .

[21]  Junichi Arai,et al.  Frequency control with dead band characteristic of battery energy storage system for power system including large amount of wind power generation , 2013 .

[22]  David Schlipf,et al.  Lidar-assisted control concepts for wind turbines , 2016 .

[23]  Kathryn E. Johnson,et al.  Lidar-enhanced wind turbine control: Past, present, and future , 2016, 2016 American Control Conference (ACC).

[24]  David Schlipf,et al.  Nonlinear model predictive controller design for extreme load mitigation in transition operation region in wind turbines , 2015, 2015 IEEE Conference on Control Applications (CCA).

[25]  Susumu Shimada,et al.  Can LiDARs Replace Meteorological Masts in Wind Energy , 2019 .

[26]  Mark J. Balas,et al.  Periodic Disturbance Accommodating Control for Blade Load Mitigation in Wind Turbines , 2003 .

[27]  A. D. Wright,et al.  Modern Control Design for Flexible Wind Turbines , 2004 .

[28]  Alan Wright,et al.  Combining Standard Feedback Controllers with Feedforward Blade Pitch Control for Load Mitigation in Wind Turbines , 2010 .

[29]  David Schlipf,et al.  Field Testing LIDAR Based Feed-Forward Controls on the NREL Controls Advanced Research Turbine , 2013 .

[30]  Eduard Muljadi,et al.  Pitch-controlled variable-speed wind turbine generation , 1999, Conference Record of the 1999 IEEE Industry Applications Conference. Thirty-Forth IAS Annual Meeting (Cat. No.99CH36370).

[31]  Jie Huang,et al.  Nonlinear Output Regulation: Theory and Applications , 2004 .

[32]  Darrell F. Socie,et al.  Simple rainflow counting algorithms , 1982 .

[33]  Gijs van Kuik,et al.  The Lanchester-Betz-Joukowsky Limit , 2007 .

[34]  Kathryn E. Johnson,et al.  Advanced Control Design and Field Testing for Wind Turbines at the National Renewable Energy Laboratory , 2004 .

[35]  Alan Wright,et al.  Field Testing of Feedforward Collective Pitch Control on the CART2 Using a Nacelle-Based Lidar Scanner , 2014 .

[36]  Kiyotsugu Takaba.  A tutorial on preview control systems , 2003, SICE 2003 Annual Conference (IEEE Cat. No.03TH8734).

[37]  L.Y. Pao,et al.  Control of variable-speed wind turbines: standard and adaptive techniques for maximizing energy capture , 2006, IEEE Control Systems.

[38]  David Schlipf,et al.  Nonlinear model predictive control of wind turbines using LIDAR , 2013 .

[39]  Koji Yamashita,et al.  Development of frequency stabilizing scheme for integrating wind power generation into an isolated grid , 2012 .

[40]  David Schlipf,et al.  Prospects of a collective pitch control by means of predictive disturbance compensation assisted by wind speed measurements , 2008 .

[41]  Martin Kühn,et al.  Prospects of optimization of energy production by LIDAR assisted control of wind turbines , 2011 .

[42]  Mark J. Balas,et al.  Disturbance Tracking Control Theory with Application to Horizontal Axis Wind Turbines , 1998 .

[43]  Harry L. Trentelman,et al.  Control theory for linear systems , 2002 .

[44]  Alan Wright,et al.  Blade Pitch Control with Preview Wind Measurements y , 2010 .

[45]  A. D. Wright,et al.  Advanced Control Design for Wind Turbines; Part I: Control Design, Implementation, and Initial Tests , 2008 .

[46]  Mark J. Balas,et al.  Testing State-Space Controls for the Controls Advanced Research Turbine: Preprint , 2006 .

[47]  Kaman Thapa Magar,et al.  Adaptive Tracking Control of Partially Known Signals with Application to Large Wind Turbines In Region II Operation , 2011 .