Active protection for photovoltaic DC-boosting integration system during FRT

Abstract

Compared with traditional photovoltaic (PV) power plants, PV DC-boosting integration system faces serious DC-bus overvoltage problem due to its special structure during the fault ride-through (FRT). Based on the unique power-output features of PV array, the authors describe a design of coordinated control strategy for the converters in the PV DC-boosting integration system to maintain a stable DC voltage during FRT process. In addition, existing FRT control scheme ineluctably lowers the performance of the line protection; thus, a combination strategy of the system control and the line protection is proposed to enhance the fault discrimination ability (especially the interphase fault). A detailed model of the PV DC-boosting integration system is created in PSCAD/EMTDC; the simulation results show that the proposed method not only realises the smooth FRT process with a stable DC bus voltage but also can reliably identify the voltage sag caused by the transmission line faults.