Abstract: This paper analyzes the technical points of evaluation and design of AGC frequency modulation project aided by energy storage system. When selecting the energy storage capacity configuration, it is recommended to use the energy storage system capacity with 0.5 h discharge time. The way of electrical connection is through the unit 6 kV or 10 kV high-voltage factory power supply. When the system is charging, the original protection does not need to be adjusted. When calculating the short-circuit current, it is necessary to consider the additional three-phase short-circuit current provided by the energy storage system under the most serious condition, and verify whether it exceeds the interruptible range of the circuit breaker. When the secondary design of the auxiliary power switch cabinet is carried out, the joint tripping interface for energy storage system could be added in the transformer protection and high voltage auxiliary power supply switching module. In the aspect of security evaluation, subsynchronous oscillation should be considered. The paper also introduces the renovation projects of DCS system and RTU system in thermal power plants.