In view of optimization of the microgrid energy storage system（ESS） capacity allocation

in order to ensure that the planned storage capacity has a better adaptive ability for future system operation

the optimal economic operation of microgrid with energy storage is considered

and the battery life loss in microgrid operation is also evaluated quantitatively. Then an optimization model of double-layer energy storage capacity which takes both the battery life and operational economy of microgrid into account is proposed. Since there are both operation variables and planning variables in the model

and it is difficult to mathematically describe the relationship between operating costs and energy storage capacity

a two-stage solving strategy based on MADS（Mesh Adaptive Direct Search） black box optimization algorithm and improved particle swarm optimization algorithm（IPSO） is presented to solve the problem. Comparison in various operational scenes shows that the proposed storage capacity allocation scheme can prevent the ESS from in-depth charging or discharging and extend the battery life of ESS while ensuring the economical operation of microgrid

therefore has a higher overall economic efficiency. The two-stage solving strategy effectively reduces the computational scale and solving difficulties

and the computational efficiency is greatly improved. The simulation results prove the validity of the model and the solving method

and provide an important reference for the microgrid energy storage capacity configuration.