State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China
This work is supported by National Key R&D Program of China (No. 2018YFB0904600) and National Natural Science Foundation of China (No. 51777072).
The structure and operation modes of flexible DC grid are diverse, and there are strong coupling relationships among various power electronic devices. The fault characteristics are complex, coordination control is difficult, and active control of fault current still faces great challenges. Based on the development mechanism of fault current in flexible DC grid, the paper compares and summarizes the fault characteristics of AC and DC grids, and illustrates the necessity and possibility of active control of fault current in flexible DC grid. The basic scheme of active control scheme for fault current of flexible DC grid is determined. Domestic and foreign research results is summarized, active control schemes according to selectivity principle and suppression principle is classified. Taking several typical schemes as examples, the characteristics of different types of active control schemes is analyzed and simulated in PSCAD/EMTDC verification, the characteristics of different active control schemes is compared and summarized. The results show that the active control of fault current is coordinated by the source side and the network side equipment, which can isolate fault quickly, save the cost of line investment and recover quickly.