In recent years, a lot of distributed generations such as photovoltaic and wind power generations are going to be installed in power systems. However, the fluctuation of these generator outputs affects the system frequency. Therefore, introduction of battery system to the power system has been considered in order to level the fluctuation of the total power output of the distributed generations. This research aims at suppressing the system frequency fluctuation and the tie line power flow deviation due to short-period fluctuation of wind power output within a certain range by cooperative control of LFC generators and battery system. It is assumed that a TBC based small control area with a large penetration of wind power plants is interconnected into a FFC based large control area. In this paper, the fluctuations of the system frequency and the tie line power flow are analyzed and LFC signal dispatching methods for effective control of the LFC generators and the battery system are proposed. Then, the required battery capacity for suppressing the tie line power deviation within a given level is evaluated.