States Reconstruction Of Combustion Process And Its Application To Optimization Of Coordinated Control System

In China, where power industry is the main cause of energy consumption and pollutants discharge, dominant status of thermal power will last for a long time. So the main status of thermal power must attract more interest to achieve the goal of energy conservation and emission dedution. For energy conservation in thermal power, optimization of measurement, control, operation, management should be considered. Coordinated control optimization was discussed in this thesis. As a precondition of stability for power unit, coordinated control system is the core of control optimization for energy conservation in the whole unit.A simplified dynamic nonlinear pressure-load model was chosen and linearized to deduce a model described as transfer function matrix. After determination of input-to-output relationship, assuming other variables as disturbances, open-loop transfer fuctions for fuel rate to pressure in boiler following mode and fuel rate to load in turbine following mode were deduced. Anaylsis showed that variation of operating point has little influence on transfer fuctions mentioned above. That is to say, coordinated control system can adapt load variation itself to a certain extent.A heat release signal reconstruction method using air flow rate and oxygen content was introduced. Taking the differential heat release signal as an inner feedback, a guidance differential coordinated control structure was proposed. Compensated tunning method combining with relative gain in multivariable system analysis was introduced to achieve parameters of the differentiator. Mathematical formula and simulation results showed that guidance differential coordinated control system can reduce disturbance of pulverizing system effectively and can reduce pressure fluctuation caused by load variation or fuel calorific heat change. In addition, simulation results verified that the control system preforms better in the model where pulverizing inertia and lag is severe.Boiler heat storage coefficient is an important parameter to construct DEB heat release signal. By mechanism analysis, combining with the concept of volume heat release coefficient, a boiler heat storage coefficient calculation method using design data and thermodynamic properties of water and steam was discussed. Calculation and comparison with relative references showed that boiler heat storage coefficient decreases as pressure increasing; normalized heat storage coefficient is tend to reduce as boiler capacity enlarging; the normalized coefficient is smaller in once-through boiler than in drum boiler.To sum up, the guidance differential coordinated control system proposed in this thesis can improve system perfomance and reduce influence caused by inner loop disturbance; Quantitative heat storage analysis of ultra supercritical once-through boiler provides an important parameter for once-through boiler modelling and control.