Under the background of the global accelerated green low-carbon technology facilities layout, the energy structure has undergone a historic change, the new energy consumption and transmission of new energy has given rise to a huge demand for a new type of power system, which also provides a broad application scenario for the application of flexible DC transmission technology. The application of integrated gate commutated thyristor (IGCT) devices in the field of flexible DC transmission can effectively reduce the transmission loss rate, improve the reliability of the system operation, and at the same time can also reduce the project cost. This paper firstly introduces the topology and main parameters of the flexible module based on 4.5 kV IGCT device, then describes the typical fault conditions in the flexible DC transmission system, and elaborates the fault protection capability of the IGCT flexible power module, and finally verifies the extreme fault protection capability of the IGCT-MMC submodule through experiments, which shows that the flexible power module based on 4.5 kV IGCT device can effectively reduce the transmission loss rate and improve the system operation reliability, as well as reduce the project cost. The results show that the 4.5 kV IGCT-based flexible power module can complete the protection action during extreme faults without affecting the normal operation of the system.