1. Photovoltaic, Wind and Geothermal Unit, National School of Engineering of Gabès, University of Gabès, Gabès 6072, Tunisia e-mail:
2. Department of Instrumentation and Control Engineering, Faculty of Mechanical Engineering, Czech Technical University Prague 166 07, Czech Republic e-mail:
3. Photovoltaic, Wind and Geothermal Unit, National School of Engineering of Gabès, Tunisia University of Gabès, Gabès 6072, Tunisia e-mail: