A Control and Protection Scheme of DC Collection Grid-Connected System for Solar Photovoltaic Plants

At present, solar photovoltaic plants mainly adopt AC collection grid-connected systems, with simple control methods and large transmission loss, which is not conducive to long-distance transmission of power. Meanwhile, the DC Collection Grid-Connected System (DCCGS) has flexible control modes and higher transmission efficiency. DCCGS consists of DC collection system and DC grid-connected system with different voltage levels, including multiple DC loops and various inverters. The existing AC or DC protection cannot be directly applied to DCCGS. It is necessary to analyse the fault characteristics of DCCGS and propose a new type protection. The DCCGS control and protection scheme proposed in this dissertation can effectively improve the operational reliability of solar photovoltaic plants, and lays a solid foundation for further research on DCCGS collaborative control.