Research On Adaptive Control Strategy Of Multivariable Thermal System

With the development of national economy, once-through boiler generating unit has become the main unit of large thermal power plants for its advantages as like as high efficiency, strong load adaptability and so on. Boiler and turbine coordinated control system is a multivariable control system which has complex and strong coupling characteristics and it is the main control system of once-through boiler generating unit. It is associated with the unit’s safety, steady and economy. Therefore, it has theoretical significance and application value to research once-through boiler and turbine coordinate system control strategy, and to optimize the coordination system dynamic performance.This paper studies the control object, which is three inputs and three outputs control model of a600MW unit, its inputs are fuel, turbine valve opening and feed water quantity; the outputs are turbine pressure, power and intermediate point enthalpy. Firstly the paper verifies the model accuracy by doing disturbance experiment in the unit model and uses feed forward compensation to achieve dynamic decoupling. Then according to the decoupling control object model, it presents a pole-zero placement adaptive PID control algorithm, which is applied to the unit model, the experimental results show that the system output responses have improved considerably. But it’s very difficult to analyze its stability and the object parameter identification needs a lot of calculation; so it further researches a Narendra model reference adaptive control algorithm which is based on the Lyapunov Stability Theory and carries on simulation verifications by Matlab/Simulink software separately. The simulation results show that when the unit model doesn’t change, the adaptive control effect is almost as well as the traditional PID control; when it changes in a small range, the adaptive control effect is obvious better than the traditional PID control; it has smaller overshoots, quicker response speed and stronger adaptive ability. Finally, it simply analyzes the anti-jamming problems of the control system by adding external disturbances. The conclusion is drawn that the adaptive control system can withstand disturbances with certain intensity, and has strong anti-interference ability.