DESIGN AND ANALYSIS OF CONTROLLED SEPIC AND LLC CONVERTERS FOR PHOTOVOLTAIC SYSTEMS

Abstract

Solar photovoltaic (PV) energy, a nonconventional source, has been a good replacement and best utilized electric source which is clean, non-polluting, safe, and renewable. A power converter is needed to regulate and control the harvested solar power and achieve the required output voltage for various applications. In this paper, two power converters are presented and discussed for PV systems, which are SEPIC (single-ended primary inductor converter) and LLC resonant converters. Control systems are designed and developed to tune, regulate, and control the output voltage of the SEPIC and LLC converters under various conditions with respect to the load requirements. These proposed control systems are PID (proportional integral derivatives) and FLC (fuzzy logic controller) that are investigated for the nonlinear models of the power converters. MATLAB/SIMULINK is used to model and simulate the proposed PV systems, where the performance of the open loop and closed loop (PID/FLC) systems for the SEPIC and the LLC are analyzed with respect to solar radiation and load conditions. The system efficiency values for SEPIC and LLC for open loop model are 93.3% and 80.3%, respectively. The simulation results of the proposed PV systems show that the output voltage is controlled and stabled successfully to the required voltage for various loads/applications while the input power from the solar panel and the load applications are varying. The FLC system yields the faster and more robustness response than PID systems.