Grid-forming energy storage system is expected to solve the problems like insufficient frequency modulation resources and disturbance resistance decline of large-scale new energy-based power grid. However

its active support ability is greatly limited due to its inherent power coupling characteristics

plus power overshoot

oscillation and even instability problems are most likely to occur with parameter variation. To solve this problem

a full-order small signal model for grid-forming energy storage system is developed

its frequency response characteristics are analyzed according to the output power state space model and its characteristic roots. On this basis

by analyzing the sensitivity and participation factors of the state space matrix parameters

the stable boundary of the grid-forming energy storage converter is given

and the influence of key parameters of the grid-forming energy storage converter on its dynamic power coupling

frequency support and other grid related characteristics is clarified. The simulation and semi physical experimental results have verified the correctness and feasibility of the theoretical analysis

providing a basis for the design of grid connected parameters and stable operation of grid-forming energy storage converters.