Energy storage system has the characteristics of superior quality frequency modulation power source.Using energy storage technology to assist power frequency modulation is not only beneficial to the overall operation of power grid

but also helpful to enhancing the economic and environmental benefits of power system frequency modulation. This paper analyzes the frequency control modes of power grid and the feasibility of energy storage participating in power system frequency modulation. Five application scenarios of energy storage participating in power system frequency modulation are proposed

and the operation boundary of energy storage system in different scenarios is analyzed. The equivalent model of three zones and eight units is built to verify the calculation method of the power regulated by the fixed unit and variable unit of primary frequency modulation

and the principle of area control error(ACE) signal distribution in multiple energy storage units in secondary frequency modulation.The simulation results show that

the value of the fixed unit regulation power K should be 5 under the condition of step load disturbance and 10 under the condition of continuous load disturbance. Among multiple energy storage units

the principle of power distribution based on state of charge(SOC) power function can realize the reasonable distribution of power.