Analysis And Modeling Of Steam Turbine System In Small Time Scale

With the development of China’s electric power system, the interaction between the regional power grid has been further strengthened. The impact of the power plant is much more significant in terms of the security and stability of power system. The safe operation of large grid power system requires for unified coordination, control and administration, in which plant grid coordinated operation and machine grid coordinated operation are put forward higher requirements.As the link connecting the grid and power plants, steam turbine and its control system play an important role in the grid frequency stability and grid load balance. At the same time, the research on steam turbine system dynamic model is one of the important aspects in the power system transient simulation and long-term dynamic simulation. So building and studying of turbine system model applied to power system stability analysis has a very important and practical significance.On the basis of the mechanism analysis, this paper deduced in detail transfer functions of steam turbine and digital electro-hydraulic control system. Through inputting step function, correctness of the mathematical model was verified. Two non-linear nodes (dead zone and saturation limit) were studied in the control system. And by inputting step function and sine, the effects of nonlinear characteristics of the electro-hydraulic control system were discussed.Finally, under the Matlab/Simulink environment, taking into account the characteristics of the actual unit’s dead zone saturation limit, the paper built a simulation model of a reheat steam turbine600MW overall system and discussed the turbine system power output characteristic and rotor speed characteristic, when the steam turbine was under load disturbance, main steam pressure disturbance and power set point disturbance. The simulation result verified the validity and correctness of the model. The research results of this thesis lay some foundations for the power system transient or long-term stability analyzing.