Robust control for maximum power point tracking in photovoltaic power system

This paper presents a robust control for the maximum power point tracking (MPPT) in a photovoltaic power system. A perturbation and observation method is adapted to the MPPT, the maximum power point is tracked by increasing or decreasing the duty ratio of on-state of switching device. The variation of duty ratio is determined by considering its circuit parameters. However, it is known, that actual capacitance of an electrolytic capacitor in parallel with the photovoltaic array has 50% tolerance of its nominal value. If the variation of duty ratio is determined based on its nominal value, the performance of MPPT is degraded. Thus, accordingly one must construct a robust system. In the authors´ system, they adopt a robust controller for the MPPT, then one can control the voltage of the photovoltaic array accurately. As a result, one may obtain high performance MPPT. Experimental results are shown using an inverter using back-boost chopper circuits