The Scada system was developed over the platform Axeda Supervisor Wizcon for Windows & Internet V8.2 [16]. The SCADA system used to implement this monitoring and control strategy permits the selective access to the application, depending on the user’s responsibility degree. In this paper we developed three user levels: Operators, Supervisors and Administrators. Several SCADA menus were built. The main characteristic of a SCADA Menu is to be simple, explicit and quick on transmitting the information to the operator or to the System administrator.

One of the developed Graphical User Interfaces (GUI) is shown in fig 9. As this SCADA platform is web enabled, all the GUI displayed data is also on-line accessible through the internet.

In fig. 9 it is shown the developed main menu for the sun-tracker system. The on-line available information, referring actual data from the tracker unit is: actual position for both axis, actual PV — power generated, max. daily PV-power generated, actual efficiency ratio.

4. Conclusion

This paper proposed the optimization of the electric energy production by photovoltaic cells through the development of an intelligent sun-tracking system. The developed solution has many advantages in relation to similar existing devices, as this system is autonomous regarding the information needed to process the optimal orientation and is intelligent in a way that it performs on-line monitoring of the photovoltaic energy production.

An experimental prototype was built and field results have proven the good performance of the developed tracking system.

The observed increase in power generation, in relation to other PV-systems, without tracking devices, is of similar magnitude (ca. 25%) as for other usual tracking solutions. However, this system has a relative advantage, as it measures exactly the controlled variable: the actual PV — power generation.

Box0: After reset is activated, the system stores the PV — power generated in the actual position, Pactual, in the variable Pin. The system searchs its reference — null position. It moves until it finds the hardhome position (both external proximity sensors on). In this position the system assumes the absolute orientation angles for both axis equal zero (a1 = a2 = 0). The maximal Power, Pmax is set to zero. Both counters, C1, C2, are loaded;

Box1: After start is activated, the system iniciates the search for the maximal power generated in axis 1, with an angle increment a10. The system stores the power generated in variable P1.

Box2: If P1 < Pmax, the system goes to Box 4, and follows for a new position;

Box3: If P1 > Pmax, this position is stored in the variables: a 1max, a2max. The max. Power value, Pmax is actualized with the new Power value P1;

Box4: Counter for axis 1 is updated;

Box5: After all orientations for axis 1 are evaluated, regarding a fixed orientation for axis 2, axis 2 is positioned in a new position, with an angle increment a20, and axis 1 returns to its initial position a1=0. The system re-initiates the search for the optimal orientation of axis 1, regarding the new position of axis 2. The information flux returns to box 1.

Box6: After all orientations for axis 1 are evaluated, regarding all different positions of axis 2, the system compares the maximal power found (Pmax) with the initial Power generated, before the search process had begun (Pin). If the new Power value is greater than a pre-defined gain, this new correspondent orientation (a1max, a2max) is sent to all park panels. If the power gain is not enough, the new found position is not to follow by the other PV-panels.

Box7: After a pre-defined time interval (K) the tracker system initiates a new complete search process in both axis. The information flux returns to box 0.

Acknowledgment

This work was partially funded by the FCT through program POCTI-SFA-10-46-IDMEC, subsidized by FEDER and by the Project PETER — PIC Interreg IIIA SP6.E53/03.

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