A thermal power plant model for dynamic simulation of the Load Frequency Control (LFC) of electric power systems is presented. In the model, MW response of the thermal power plant is represented using two components. One is the slow component responding to the MW demand change from the LFC, and the other is the fast component due to the primary frequency (governor) control. For the former, demand rate limit, boiler response delay, and boiler steam sliding pressure control are considered. For the latter, turbine governor response, turbine load reference control and steam pressure change due to turbine control valve movement are considered.