Research On Tension Control For Coating Production Line Of Thin-Film Solar Cell

The photovoltaic film cell is an important branch and development direction in solar photovoltaic industry of new enegy field, so the invention of Copper Indium Gallium Selenide(CIGS) ink makes the manufacture of CIGS solar film cell achieving to an efficient production process of printing. With the roll-to-roll process flow, in CIGS film cell printing process, nanoscale CIGS ink containing special material ratio is coated on a flexible material such as metal foil by the method of slit coating, finally winded into ordering mold to achieve the purpose of producting solar cell rapidly. Tension and coating process in the process of production directly affect the performance of the finished film cell.In the CIGS film cell coating process, tension control of the material throughout the whole production chain. As the tension fluctuation can lead to coating thickness of film cell, its control accuracy is an important factor of qualified rate of film cell product. Large tension may make the cell material become thinner even broke while small tension could make the material become thicker even loose, affect the production efficiency and product quality. In order to improve the product quality and production efficiency, doing research on reliable tension control system is a prerequisite of manufacturing solar film cell coating system. Currently, CIGS film cell fabricated by roll-to-roll coating technology has not been popular in the domestic, and compare the traditional CIGS film cell production technology with the advanced printing and coating technology, the efficiency is too low and the cost is too high.This paper did research on continuous process and control technology of non-stop roll exchanging based on the analysis of coating production process of solar film cell. To realize the accurate tension control in continuous production process, a new compound tension control strategy is proposed. System change the given velocity by the calculation of Tension-Velocity model, and compare the adopted real-time tension with the setted value, put the difference value into speed loop for correction, so indirect control the material’s drawing tension, achieve precision tension control in coating process flow. In order to achieve the roll exchanging without stopping the whole system, retractable rotary shaft and cutter for cutting materials are applied in the unwinding and winding part, and take the exact position angle and the rotation speed sensor to make the motors driving shaft holder and cutter realize high-precision position closed-loop control. Winding and unwinding motors follow the speed of main traction motor to ensure the speed control mode with tension constant.Finally, a useful solar film cell coating non-stop tension control system is designed, when meeting the production process of the production line speed at 120m/min and the width of film cell at 1m, the steady-state tension fluctuation is lower than ±1%, and the maximum dynamic fluctuation is lower than ±5%. Both the dynamic performance and steady-state precision of new system meet the requirement of production process.