With the rapid growth of wind power, high wind curtailment rate is maintained because the power system lacks sufficient flexible capacity to cope with the wind power uncertainty. The minimum stable combustion rate of the boiler limits the operational flexibility of thermal power units. Steam extraction and thermal energy storage can adjust the power output of the unit without changing the combustion rate of the boiler. Therefore it is a promising choice to retrofit the existing thermal power units with steam extraction and thermal energy storage, so as to accommodate the high penetration of wind power in the power system, especially in a power system dominated by thermal power units. This paper studies the flexible operation of a thermal power unit retrofitted with steam extraction and thermal energy storage. First, a new linear operation model of retrofitted thermal power units is proposed considering the characteristics and technical constraints. Second, a model based on stochastic unit commitment and rolling economic dispatch is established to study the benefits of steam extraction and thermal energy storage in the power system with wind power. Finally, it is simulated in IEEE24-bus system. Simulation results show that the thermal power unit with steam extraction and thermal energy storage can effectively reduce wind curtailment and improve the operational economy of the power system. This work is supported by the National Natural Science Foundation of China (No. 51977054).