Experimental Investigation On A Novel Two-axis Solar Tracking System With High-precision For Concentrating Photovoltaic Cells

Photovoltaic technology(PV)can directly convert solar energy into electrical energy,and its performance is reliable and easy to be commercialized.At present,there is a trend of low-cost power generation and large-scale promotion,so it is developing rapidly.Although PV technology currently accounts for 0.1% of global power generation,the International Energy Agency(IEA)predicts that PV technology will generate 5% in 2030 and continue to grow to 11% in 2050.Concentrating photovoltaic cells technology(CPV)is an important application direction of PV technology and is considered to be the most promising solar solution.However,the current low-cost and high-precision solar tracking system needs further research.At the same time,The accuracy of the solar tracking technology used in CPV technology is mostly the direct experimental method measurement and lacks the theoretical calculation basis.Although this method can accurately measure the system accuracy,due to the complexity and diversity of different mechanical systems,the establishment of a general system error model plays an important role in the optimization design of the mechanism and the optimization of the control strategy.In this paper,a high-precision two-axis solar tracking system for concentrating solar cells is designed for the above problems.The hardware structure of the tracking system(including structure and hardware peripheral circuits)and software(including error correction algorithm,control logic and PID controller)are designed and optimized.Finally,the effectiveness of the proposed scheme is verified by the prototype.In the system structure and hardware design,the whole structure adopts the vertical two-axis structure,the transmission mechanism adopts the design of high-precision worm gear and eccentric bushing with large transmission ratio,the photoelectric sensor adopts the self-designed four-quadrant silicon photocell sensor,and the two-phase hybrid stepping motor is selected as the power device.The main control chip is based on ATmega2560,and the peripheral hardware circuit design adds GPS module and IMU module.In the system control design,the high-precision ENEA astronomical algorithm is selected as the main algorithm,and the control strategy of hybrid tracking(algorithm tracking & sensor tracking)is adopted.At the same time,the system error correction algorithm is established based on robot kinematics.The algorithm adds four typical system error parameters.The systematic error of equipment initial position and posture,processing and assembly is eliminated.The calculation error of this algorithm is0.0376 °.The mathematical model of the stepping motor is deduced,and the PID controller design is carried out,which shortens the system response time and improvesthe system stability.Finally,the system error chain is established,and the theoretical error value of the system is 0.1076°.Finally,the prototype of the solar tracking system is manufactured,which is verified by the method of image processing with the error calibration device.The experimental results show that the tracking error of the system is 0.188°.