Supervisory Control developed for a Solar Tracking Prototype based on PV-Technology

This paper implements a supervisory control to a solar tracking prototype with two degrees of freedom (DOF). The tracker is motorized by two step motors controlled automatically by a Siemens S7-300 PLC (Programmable Logic Controller). Specific function modules are used to communicate with the step motors (FM350-1), as well as with the encoders (FM 353). The communication between the tracker and the users are performed on two levels: i) Local control implemented on an industrial Operator Panel (HMI – Human Machine Interface) and ii) Remote Control implemented on a SCADA system (Supervisory Control And Data Acquisition). The system supervision and control can be performed remotely through internet as the developed SCADA application is web enabled. This paper describes the operational methodology used to implement the supervisory control to the prototype. This solar-tracker shows great advantages when compared to other similar devices, available in the market, as the control variable is exactly the measured variable. In fact the sensor used to measure the solar radiation is a PV-cell supplying directly the electric power produced (VxI). The electric power is therefore exactly the control variable to be maximized in a traditional Solar-PV tracking system. The laboratorial prototype structure was developed in collaboration with the Mechatronics Engineering Centre from the University of Évora.