Reserach On BCS Correction System For Pole-axis Heliostat

In a tower photothermal power generation system,the heliostat in the concentrating subsystem is used to reflect the sunlight to the specified position of the heat absorber.In the heliostat system,the most commonly used heliostat includes the column heliostat and the polar shaft heliostat.The steel consumption of the column heliostat is far greater than that of the polar shaft heliostat because of the thick beam,resulting in the manufacturing cost of the polar shaft heliostat is less than that of the column heliostat.Therefore,this paper mainly studies the tracking accuracy of the polar shaft heliostat.How to evaluate and improve the tracking accuracy of polar-axis heliostat is very important for the field of tower photothermal heliostat.In this paper,the motion law of the polar axis heliostat is studied,and seven error parameters affecting the tracking accuracy of the polar axis heliostat are analyzed.In order to correct these errors,the BCS correction system of the polar axis heliostat is established in this paper.Because the BCS method can only correct one heliostat each time,resulting in low correction efficiency,the heliostat scheduling software is designed.It can realize the function of correcting the multi-surface heliostat within one day,so as to improve the efficiency of error correction.The specific research work of this paper is as follows:(1)The measurement method of tracking accuracy of heliostat is proposed.The center position of the spotlight of several heliostats is analyzed by probabilistic statistics method.The tracking deviation angles of horizontal direction and vertical direction are calculated to evaluate the tracking accuracy of the heliostats to be corrected.(2)Put forward the image processing scheme of the actual concentrating spot of the heliostat.The image processing method is used to carry out elliptic fitting to the shape of the concentrating spot,and calculate the characteristic information parameters related to the spot,which provides practical data support for evaluating and improving the tracking accuracy of the pole-axis heliostat.(3)The correction scheme of dynamic tracking error of heliostat is proposed,and the tracking Angle formula of heliostat is derived.Firstly,seven tracking error sources of heliostat are analyzed.Secondly,the dynamic tracking error model of heliostat is established,and then the tracking Angle formula of heliostat containing tracking error is derived.Finally,the nonlinear least squares mathematical model was established,and the L-BFGS algorithm was used to calculate the seven tracking error parameters in the model.Finally,the tracking Angle of the heliostat was calculated.The heliostat could accurately reflect the sunlight to the specified position of the heat absorber by tracking and running at this Angle.Meanwhile,a heliostat scheduling system is established to improve the efficiency of error correction.The pole-axis heliostat BCS correction system established in this paper has the advantages of high efficiency and accuracy.Through the verification of theoretical and practical data,this method can measure and calculate the accurate tracking error,which can be applied to practical projects to improve the power generation efficiency of tower photothermal power generation system.