Optimal design of the solar tracker used for a photovoltaic string

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This paper approaches the optimal design of the mono-axial tracking system used for a string of photovoltaic (PV) modules. The tracking mechanism is designed in a CAD (Computer Aided Design) environment (SolidWorks), the solid model being then transferred in the dynamic analysis and optimization environment (adams/View). The control system is designed with adams/Controls and matlab/Simulink, in mechatronic concept, by integrating the mechanical device and the control system at the virtual prototype level. The control method is based on a single-open-loop model with PID (Proportional-Integral-Derivative) controller, having as input the daily angle of the PV string. The output from the control system (i.e., the input in the mechanical device model) is the motor torque developed by the rotary actuator that drives the system. The tracking program has been developed by using an empirical model of the solar irradiation, obtaining the optimal angular field for the daily motion, the number of motion steps, and the actuating time. The optimization purpose is to minimize the tracking error, the design objective's value being the root mean square during simulation. The specific parameters of the PID controller are used as design variables in the optimization process. The investigation strategy is based on a design of experiments technique, obtaining the appropriate regression function. Finally, the physical prototype is developed and tested in real environment, the experimental results being used to validate the virtual prototyping-based simulation.