Maximum power point tracking with capacitor identifier for photovoltaic power system

This paper presents a perturbation and observation method with an identifier of capacitor for the maximum power point tracking (MPPT) in a photovoltaic power system. Usually, by increasing or decreasing the duty ratio of on-state of switching device, the maximum power point is tracked. 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% error 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 we must change the variation of duty ratio based on its actual value. In our system, we adapt the model reference adaptive system to identify the capacitor, then we can estimate the accurate capacitance and correct the variation of duty ratio. As a result, we may obtain the high performance of MPPT. Experimental results are shown using a proposed power inverter using buck-boost chopper circuits.