Abstract: In an offshore flexible DC transmission system, by installing a DC energy dissipation device between the positive and negative DC buses, the DC energy dissipation device can be used to absorb the differential power when a transient fault occurs on the AC side of the land side, so as to solve the fault ride-through problem of offshore wind power DC transmission of the system. We conducted an in-depth study of the DC energy dissipation device scheme based on the direct series connection of integrated gate commutated thyristor (IGCT) composite modules with concentrated resistance. First, the topology of the DC energy dissipation device and the control strategy were introduced. Secondly, the switching devices, power electronic valves, shunt capacitors, concentrated energy dissipation resistors and selection parameters of various components of the energy supply system were introduced. Finally, a 120 kV-level DC energy dissipation device engineering prototype was developed and an energy dissipation experiment platform was built. The equivalence of the test method was introduced in detail, and the prototype was prepared to verify the energy dissipation experiment. The research results show that the developed 120 kV DC energy dissipation device meets the design requirements of the absorption energy and absorption time under different duty ratios of 10%, 50% and 90%, which proves the rationality and reliability of the design scheme.