Abstract: This paper focuses on large-scale photovoltaic power plants and its collection system. By analyzing the advantages and disadvantages of various connection methods in photovoltaic power plants, a new DC step-up collection system topology for large-scale photovoltaic power plants is proposed. Based on modular multilevel converter (MMC), the topology and control of high-ratio DC/DC and DC/AC converters are addressed. The DC step-up collection system is modeled in RT-LAB. According to the principle of DC faults in the model, the simulation results are analyzed and the fault characteristic is concluded. This paper is useful to explore the new design of the DC step-up collection system and the control of the multiple converters based on the MMC.

Key words: photovoltaic power plant, DC step-up collection, modular multilevel converter (MMC), converter topology, RT-LAB simulation