For the primary frequency regulation of thermal power assisted by energy storage systems

a proper and reliable control mode was proposed to optimize the primary frequency regulation performance of energy storage systems

as a guide of engineering design and application. Firstly

the control model combined with virtual droop control and virtual inertia control were analyzed by introducing the sensitivity theory of power regulation coefficient. Next

by taking the Grid data of Central Area of China as the case

the calculation method for primary frequency regulation was assessed and the simulation was conducted in different scenarios of energy storage system project applications

to figure out the selection principles of control modes. Finally

it was concluded that

for assistant energy storage systems

the control mode should be virtual inertia control or virtual droop control according to the disturbances

and for independent energy storage systems

the control mode should combine virtual inertia control with virtual droop control based on the actual demand of frequency regulation.