Abstract: A novel structure of direct current（DC）step-up collection system for photovoltaic（PV）with consideration of impedance network concept has been proposed to cope with technical challenges to large-scale PV station.An impedance-source multi-module cascaded DC-DC step-up converter serves as the key device for the proposed collection system,which has an integrated function of multi-channel maximum power point tracking（MPPT）control and high-gain DC step-up conversion.The low-voltage DC bus and distributed MPPT devices can be forgone to make the system simple and reliable.The system structure is beneficial to internal fault isolation and unitary dynamic control at station level.The introduction of impedance network makes it possible to adjust the voltage gain flexibly as well as resist shoot-through of bridge arms,which can improve the operational adaptability against input power mismatch and reliability of the DC step-up collection system for PV.A detailed introduction of system architecture,key DC step-up converter,working principle and control/modulation strategy has been given.All theoretical results have been validated by system simulation under balanced and mismatched power inputs.The proposed DC step-up collection system has a potential application value in the future construction of large-scale PV stations.