Research On The Modeling And State Parameter Detection Of Thermal Power Generation Process

The thermal power will be a predominant way of electric energy supplies for years to come in China. Keeping the normal and efficient operation of thermal power units is important for realizing the indicators of energy saving and emission reducing. The state parameter detection and control optimization are the effective measures to achieve this goal. However, the thermodynamic systems in larger thermal power units are complicated, so some important state signals cannot be real-time measured or cannot be measured exactly, which is an important element affecting the control performance and safe and economic operation of units. According to the characteristics of research object, based on the flexible combination of mechanism analysis and data analysis, the main thermodynamic systems of units were researched. And some state signals, which were of explicit physical meaning, of practical application value and can reflect the real operation law of thermodynamic systems, were gained. The work can be presented as follows:1. The signal of coal heat value was constructed. Through analyzing the balanced relations of mass flow and energy flow in the process of electricity generation, using the pressure of the turbine first stage, calculation opening of governing valve, drum pressure and boiler feed coal flow, the signal of coal heat value was constructed. This signal has the advantages of finer dynamic performance and also has better practical value in control system engineering application.2. The boiler heat release signal was gained. Based on the analysis of the large amount of boiler operation data, the particular correlativity relation between boiler air flow, oxygen content in boiler flue gases and feed coal flow was discovered. And then, combining with the mechanism analysis, the cause and the law of this relation were explained, based on which, the boiler heat release signal was constructed. This signal has finer dynamic performance and enough accuracy for engineering application.3. The estimation signal for drum false water level was constructed. Through analyzing the balanced relations of mass flow and energy flow in boiler water-steam system, the model that can describe the real drum water level signal was constructed. This signal can reflect the change of real drum water level with finer dynamic performance, especially the false water level phenomenon. This signal can be applied in the control system optimization. Meanwhile, in the process of research on the above problems, some research achievements in terms of the inner operation law and theoretical study methods for thermodynamic system were gained. The main work can be presented as follows:(1) The dynamic model of positive pressure pulverizing system of medium speed mill direct firing was constructed. The change law of main parameters in the model was analyzed. And it is pointed out that the primary air rate is the key factor, which affects the inertia and delay of pulverizing system. (2) The concept of volume heat storage coefficient was presented, on the basis of which, a method for calculating the heat storage coefficient was brought forward. (3) The simplified non-linear dynamic model of furnace pressure, furnace temperature versus fuel flow and the entrance pressure of induced draft fan was constructed. And the inner interaction relation between furnace pressure and furnace average temperature was revealed. (4) The multivariable dynamic model with 3 inputs/3 outputs of drum boiler fuel, opening of governing valve and feed water flow versus unit load, throttle pressure and drum water level was constructed, which was gained in the form of differential equation. All the static parameters and dynamic parameters of this model have the explicit physical meaning. This model has more practical application value than the one of Astrom model, which was constructed in 2000 in the form of partial differential equation. (5) The model of turbine heat regenerative system was constructed, and the inner cause and law of how the condensate throttling affects units load was explained.