Estimation based Individual Pitch Control of Wind Turbine

Abstract

Original scientific paperThe use of wind power for generating electricity has experienced an uninterrupted and accelerating growth over last few decades and this growth is likely to continue. In order to enable even greater role of wind energy in power production it is necessary to increase the size and unit power of wind turbines. As wind turbines grow in size they are subjected to extreme loads and fatigue caused by nonuniform turbulent winds. Therefore, control algorithms that can assure load and fatigue reduction become a necessity. In this paper the individual pitch control for reduction of the periodic blade and hub loading is explored. To avoid problems related to the required blade loads measurements a method for their estimation based on other process variables is proposed. The performance of the individual pitch controller that uses such load estimations instead of measurements is tested and compared to the collective pitch control and the individual pitch control based on measured loads.Key words: Wind turbine, Collective pitch control, Individual pitch control, Load estimation Upravljanje pojedinačnim zakretanjem lopatica vjetroagregata zasnovano na estimaciji opterećenja. Korištenje energije vjetra za proizvodnju električne energije zadnjih je nekoliko desetljeća zabilježilo neprekidan ubrzan rast kojiće se po svemu sudeći nastaviti. Da bi se omogućila još veća uloga energije proizvedene iz vjetra u ukupnoj proizvodnji, potrebno je omogućiti proizvodnju većih vjetroagregata s većom jediničnom nazivnom snagom. Povećanjem dimenzija vjetroagregata značajno se povećavaju njihova strukturna opterećenja i zamor materijala uzrokovan nejednolikim turbulentnim vjetrovima. Stoga upravljački algoritmi koji osiguravanju smanjenje opterećenja i zamora materijala postaju neophodan dio sustava upravljanja suvremenih vjetroagregata. U fokusu je ovoga rada algoritam upravljanja pojedinačnim zakretanjem lopatica vjetroagregata kojim se postiže smanjenje periodičkih opterećenja lopatica i glavčine. Jedan od problema kod takvih algoritama upravljanja jest potreba za mjerenjem opterećenja lopatica što zahtijeva složenu i skupu mjernu opremu. Stoga je u ovome radu predložena estimacija opterećenja lopatica na osnovi drugih, lako mjerljivih i dostupnih procesnih veličina. U radu je prikazano upravljanje pojedinačnim zakretanjem lopatica zasnovano na estimiranim opterećenjima. Ponašanje vjetroagregata s upravljanjem zasnovanim na pojedinačnom zakretanju lopatica uz takav algoritam estimacije usporeeno je s upravljanjem zasnovanim na simultanom te pojedinačnom zakretanju lopatica uz upotrebu mjerenih opterećenja.Ključne riječi: vjetroagregat, upravljanje zakretanjem lopatica, simultano zakretanje lopatica, pojedinačno zakretanje lopatica, estimacija opterećenja

Individual pitch control of wind turbines: Model-based approach

“…Preview information was used for calculation of the high-performance derivative of the desired pitch angle. Note that the error model (11) for the pitch angle mismatch is exponentially stable in this case. The tilt moment which is plotted with a red line corresponds to the pitch control system (10) without derivative of the desired pitch angle (without preview information).…”

“…This type of loading is periodic due to the periodicity of the individual blade wind speeds. Similar models can be found in Van Engelen 4 and Jelavic et al 11 Finally, the tilt load can be calculated using the transformation between the rotating and fixed frames and the individual blade flapwise bending moments. Therefore, the contributions of the flapwise bending moments on the blades to the tilt moment M tilt on the fixed part of the wind turbine structure are calculated as follows …”

Two LQRI based Blade Pitch Controls for Wind Turbines

“…In this paper, the simple wind turbine model utilizes rigid rotor blades and drive-train, while tower is modeled by one mode of fore-aft motion and one mode of side-side motion [3,9,10]. Consider the blade coordinate system as shown in Figure 1(a), where the x-axis points in the direction along the main shaft, the z-axis points toward the blade tip, the y-axis forms right-handed rule, and its origin is at the blade root.…”

“…Individual pitch control has been investigated by a number of researchers and shown to be beneficial [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. However, individual pitch control can reduce only the oscillation of blade bending moment, not its steady-state value.…”

Effects of Yaw Error on Wind Turbine Running Characteristics Based on the Equivalent Wind Speed Model

“…To improve the utilization of wind energy and optimize the wind loads on the blades, the problems caused by steady-state and transient-state yaw error must be considered. Specific control strategies should be used for wind turbines, including pitch control and generator torque control to respond to wind aped fluctuations as well as active yaw control to cope with frequent changes in wind direction [1,2].…”