Aiming at the application scenario of short-term high-power output of VSC-HVDC converter, a new sub-module structure based on the principle of level reduction is studied. That is, in the case of short-term high-power output, the bypass switch is used to realize the structural change from the full-bridge sub-module to the half-bridge sub-module, so as to reduce the rated capacity of half of the full-bridge sub-module. At the same time, for the traditional inertia support control method of the grid-following converter, the fast output of the inertia support power of the grid-following converter is realized by increasing the feedforward channel of the frequency loop. Finally, the correctness and feasibility of the proposed control strategy are verified by PSCAD/EMTDC simulation. In the application scenarios of new energy island transmission and regional power grid interconnection, the VSC-HVDC converter based on the new full-bridge sub-module structure has better applicability to new functional requirements such as inertia support and grid-forming control.