With the access of a large number of renewable resources

the voltage support strength of the new-type power system (referred to as "system strength") is gradually reduced

resulting in an increase in the risk of system instability. In order to improve the stability of the new-type power system

large-scale access to energy storage systems (ESSs) based on grid-following (GFL) converters is taken into consideration. Due to the asymmetric network structure of the actual system and the variable operating conditions of the renewable energy equipment

the improvement effects on the system stability are different at the different access locations of the ESSs. Furthermore

the system strength under actual non-rated operating conditions (referred to as "actual operating conditions") may be weaker than that under rated operating conditions

and the ESS location method based on rated operating conditions may have poor effect on improving the system strength under the worst actual operating conditions. Therefore

aiming at optimizing the location of ESSs to improve the multi-infeed system strength under actual operating conditions

firstly

we solved the subsystem of the renewable energy multi-infeed system with ESSs under actual operating conditions based on the eigensubspace perturbation theory

which can approximately characterize the system strength of the original system. Thereby

the mechanism of the effect of the ESS on the renewable energy multi-infeed system strength is revealed. On this basis

in view of the worst possible conditions

an optimization method and process of ESS location based on sensitivity index are proposed. Finally

a numerical example is given to verify the effectiveness of the proposed method. The proposed sensitivity index can reflect the influence of renewable energy equipment at different nodes on system strength under actual operating conditions

and can be used to accurately locate key equipment. The ESS optimization location method based on this index can better improve the multi-infeed system strength.