Research on Melting Scheme for Overhead Line of Flexible DC Grid Without Power Failure

Ice coating caused by ice and snow disasters is extremely harmful to DC power grids. Therefore, the research and application of ice melting technology is of great significance for DC grids to combat ice disasters. According to the advantages and limitations of a variety of DC transmission line melting methods, the paper decided to select the two types of operation modes, namely, power flow control and converter station bipolar parallel connection, to analyze the ice melting of overhead lines. Firstly, the paper calculates the minimum ice-melting current of the overhead line and the corresponding ice-melting time of different ice-melting currents. Then the ice-melting analysis is performed on two typical overhead lines using the power flow control method, and one of the overhead lines is melted. For another line, the ice-melting is implemented using the bipolar parallel operation method. On this basis, the paper proposes a switching operation scheme for switching to bipolar parallel operation. Finally, it is concluded that the power flow control method and the bipolar parallel operation of the converter station can improve the current of the transmission line, thus achieving the melting of the overhead line of the four-terminal flexible DC grid.