Research On Dynamic Modeling And Control Of Ultra Supercritical Power Unit

With the increasing demand for electricity in China, Ultra supercritical units which have large capacity, high parameters and advance automation currently accounted for the major part in thermal power construction. The thermal power unit is a kind of multivariable nonlinear plant with large time delay, large inertia, strong coupling, time-varying parameters characteristics. With the implementation of the strategy of sustainable development in power industry, the power grid integrated automation system has put forward higher requirements to coordinated control system (CCS) of power unit. Therefore, building the power unit non-linear model and further research of its dynamic characteristics are the basis of coordinated control system optimization. This paper studies the dynamics modeling of ultra-supercritical once-through boiler, and linear ADRC will be introduced to decoupling control for thermal power unit coordinated control system.The main contribution of this dissertation are summarized as follows:According to the properties of water and steam within limits, Sparse kernel partial least squares (SKPLS) method was used for soft measurement of the thermal properties of the working medium in relevant subcooling, evaporating and superheating section. Under different working conditions the thermodynamic properties of water and steam varies greatly, especially in the region3of IAPWS-IF97, which shows strong nonlinearity. The method was applied to mechanism modeling of the once-through boiler.The heat storage of boiler and the coal-pulverizing system's inertia coefficient and time-delay were important affecting factors for boiler load instruction variation rate. The momentum and energy differential equations were coupled with the algebraic equations of properties of water and steam, approaches for solutions of the coupled algebraic and differential equations were presented, water and steam parameters profiles along it's journey were settled out. According to the boundary equations of IAPWS-IF97, the evaporating heating surface was divided into3sections,such as subcooling, evaporating and superheating section. The model of the evaporating heating surface and the superheater was built through the mechanism analysis, the calculation result shows that metal heat storage accounts for the main part of ultra supercritical boiler. The metal heat storage was substitute for the boilers' in the simplified model, the released heat was calculated by knowing the amount air and oxygen concerned, which was used to identified the inertia coefficient and delay time of coal-pulverizing system in closed loop.Studying the characteristic of various components of ultra-supercritical unit, according to the mass and energy balance to build up the mechanistic model,using the operating parameters in the vicinity of their units to simplify and fitting the model, and to obtain the analytic model of the form of expression. Through simulation experiments and comparative analysis of plant running data to verify the accuracy of the model.Research on linear ADRC for the typical thermal process--first order plus dead-time, the linear ADRC equivalent control system is presented, and analysis the Stability of the closed-loop system in the linear feedback control, the stability region of the controller parameters were determined on the basis of the improved D-partition approach. For MIMO nonlinear unit coordinated control system, the linear ADRC was introduced for each decoupled subsystem closed-loop controller design, the method is applied for1000MW ultra-supercritical unit coordinated system, simulation results show that the proposed coordinated control system is effective.