Maximum power point tracking with capacitor identifier for photovoltaic power system

A perturbation and observation method with a capacitor identifier is prcscnted for 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 powcr 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% tolerance of its iioniinal value. If the variation of duty ratio is determined based on its nominal value, the performancc of the MPPT is degraded. T~LIwSe, must change tlic variation of the duty ratio accordingly, based on its actual value. In the systcm presented, the model reference adaptive system is adapted to identify thc capacitor, so the capacitance can be accurately cstimated and the variation of the duty ratio can be corrccted by the estimated value. As a result, the high performancc of the MPPT may be obtained. Experimental rcsults are presented using a proposed power inverter using buck-boost choppcr circuits.