Abstract: Large-scale grid-connected photovoltaic（PV） power stations have become the most important form of solar energy utilization of China. As the basic unit of a photovoltaic station, the I-U characteristic of PV arrays under all kinds of weather conditions is one of the most important issues for studying grid-connected PV station operation characteristics and its control algorithms. This paper analyzed the PV module operating status with bypass diode. On this basis, the implicit complementarity model of photovoltaic arrays was given with the corresponding algorithm which was based on the merit function algorithm. Simulation results show that the proposed model and algorithm have such advantages as high efficiency and accuracy, which are suitable for large PV station modeling, analysis and simulation under all kinds of shadow conditions.