The large-scale integration of wind power and the lack of rapid ramp-up capability of conventional coal-fired units pose a serious threat to the frequency stability of the system. Considering current power structure of China is dominated by the coal-fired units

it is an effective way to solve this problem by making rational use of the deep and fast load changing capability of thermal power units to improve the dynamic characteristic. However at present

its application in power systems mainly focuses on the dispatching. This paper presents a method to employ the deep and fast load changing capability of thermal power units to the frequency control of power systems containing wind farms. Based on the frequency analysis model of power systems containing wind farms

the method firstly makes a switching scheme for deep and fast load changing state of thermal power units according to the short-term prediction of wind power and the economic and safety conditions of the units at the prediction level. Then the system frequency control under real-time wind power excitation is operated according to the switching scheme. The proposed strategy is closely integrated with the traditional automatic generation control strategy

and is easy to implement in engineering. The simulation is done in the IEEE 10-machine 39-bus system

and the results show that the proposed method can effectively improve the frequency control capability of wind power system and can be applied to interconnected power grid with high-penetration wind power.