In traditional power systems, power electronic devices are predominantly governed by grid-following control. However, with the increasing share of renewable energy, new power systems face issues such as a lack of inertia and damping, which threatens the system stability. The grid-forming energy storage technology based on virtual synchronous generator (VSG) can simulate traditional synchronous generator and actively support the system voltage and frequency, thereby enhancing the system stability. As a result, this strategy has attracted widespread attention from scholars. At present, various VSG control strategies have been developed. However, different control strategies result in challenges in unified parameter tuning, and the grid-forming capability may not meet standard requirements in some cases. Firstly, on this basis, parameter tuning is carried out according to national and power industry standards, and an active/reactive power small-signal model is established to ensure that the designed parameters meet national grid-forming standards. Subsequently, grid-forming energy storage VSG need to have seamless switching functionality at the application level, so as to reduce the impact of grid-connected current. Then, a novel pre-synchronization strategy based on eliminating phase-angle jumps is proposed, featuring advantages such as simplicity and ease of engineering implementation. Finally, simulations and experiments validated the feasibility of the proposed parameter design, as well as the effectiveness of the seamless switching strategy.