Study On Heliostat Tracking Correction Strategy Of Concentrating Solar Power Tower System

In a concentrating solar power tower system,heliostat is one of the most important components,which is the device that concentrate solar energy onto the concentrator.The concentrating efficiency of heliostats is crucial in the whole power generation process,which directly affects collecting efficiency of the concentrator,which affects the power generation of the power plant.The tracking accuracy of heliostat is an important indicator for evaluating its concentrating performance.The inaccurate tracking of heliostats will lead to the deviation of the solar reflection spot from the target position or even miss the target,and reduce the field collecting efficiency seriously.Improving the tracking accuracy of heliostats can reduce spot overflow rate and improve the accuracy of aiming point control system effectively.Therefore,how to improve the tracking accuracy of heliostats plays an important role in a concentrating solar power tower system.Aiming at the problem of tracking deviation of the azimuth-elevation heliostat and the problem of low correction efficiency caused by the long use of calibration board by existing correction methods,a two-step correcting method of heliostat tracking deviation based on a model of camera looking at the sun is studied.Firstly,the error factors in heliostat tracking system are analyzed,such as column tilt,non-orthogonal angle of two axes and zero positioning error.Secondly,a mathematical model is established for these errors,and a two-step correction scheme for heliostat is designed.(1)The eye-in-hand model of heliostat is established,the relationship between each error and camera tracking angle is analyzed,the mathematical model of camera tracking angle and tracking error parameters is established,and the calculation formula of camera tracking angle is deduced.A non-linear least squares mathematical model for tracking error parameters is established,and the least squares algorithm is given.(2)Aiming at the deflection between the optical axis of the camera and the normal line of the mirror center caused by the camera looking at the sun model,a reflection model of the heliostat is established,and the tracking error of the heliostat caused by the deflection is corrected by BCS method.Finally,a simulation verification method of the correctness of the eye-in-hand model of heliostat and the results of least squares algorithm is given.The experimental results show that the model is correct and the accuracy of the algorithm meets the requirements.A two-step correction strategy for heliostat based on the camera looking at the sun model effectively solves the problem of tracking deviation of heliostat and greatly improves the efficiency of field correction.The experimental verification is completed on the basis of the model establishment.The experimental results show that this method satisfies the system calibration accuracy requirements and can be further applied to the actual calibration work.