To improve the sustainable running ability of the wind power generation and energy storage system

a modified phase-change energy storage and expander generating system(PESES)is proposed. The optimization method of the system capacity configuration is analyzed. Firstly

the historical annual mean wind power data are resolved based on the median-filtering algorithm. The difference between the stable component of the actual output in the wind farm and the dispatch order is calculated to formulate the fractional frequency control strategy. Secondly

the non-parametric estimation is used to calculate the optimal power level of the PESES under which the given wind power schedule ability confidence level is satisfied. The evaluation index of the sustainable operation capability for the energy storage system is defined. Meanwhile

the comprehensive economic evaluation function consists of the investment costs of the power exchanging

the energy supporting and the sustainable operation safeguard of the system. On the basis of the evaluation index and the evaluation function

the optimal energy capacity of the PESES is planned. Finally

an example of the operation and planning of a wind farm equipped with a steam-jet double-screw expander generating system is described.