Energy storage (ES) is an important support for building the new power system with an increasing proportion of renewable energy

which can effectively balance the fluctuation of generation side and electricity consuming side and provide damping support for power grid. Firstly

in order to reveal the physical mechanism of ES in improving the transient stability margin of regional power grid

the dynamic interaction process between ES and synchronous generator is analyzed

the influence of ES on synchronization capacity and damping level of power grid is explored

and the key factors of ES affecting the transient stability is obtained. And then

considering the impact of transient state of charge (SOC) deviation of ES on steady-state operation

a damping control strategy without changing the net interchange energy of ES is proposed

and its stability is proved based on the transfer function model. Finally

a simulation model is established based on the data of a regional power grid to validate and demonstrate the mechanism of enhancing the transient stability of power grid by ES

as well as the correctness of the proposed damping control strategy.