Abstract: The state of charge (SOC) of distributed energy storage systems operating on the grid and participating in frequency regulation is not balanced, which affects the system stability and reduces the lifetime of energy storage modules. In order to take into account the frequency regulation performance, SOC stability and the equalization of each energy storage module, an SOC adaptive droop control is proposed firstly in this paper. Secondly, an improved equalization factor is introduced into the SOC adaptive control, which is able to reasonably allocate the input/output power of each energy storage module participating in the primary frequency regulation control, and further improves the SOC equalization speed and equalization accuracy. Thirdly, a relative capacity factor is introduced at the reference active power of the energy storage module to eliminate the influence of rated capacity on SOC equalization. Finally, a simulation model of a megawatt-level regional power grid containing energy storage modules is established, and the effectiveness of the proposed integrated control strategy is verified by simulation under step and continuous perturbations, respectively.