Research On State-Observer-based State Feedback Control For Boiler Superheated Steam Temperature

In today's thermal power control field, superheated steam temperature(main steam temperature) is one of the important parameters of the boiler, therefore, its control requirements are very strict. However, the system has the characteristics of large time delay, large inertia and parameter serious degeneration, and with the increasing capacity of the units, superheater pipes have become longer, which have caused thermal inertia and regulation lag greatly increased, so that the controlled object's complexity and control difficulty increase accordingly. In particular, the operating parameters of large units and the value of its metal material limit get less and less, so maintaining stable steam parameters becomes more important, which is of great significance for the safety, stability and economy of power unit.Most large boiler steam temperature control is still using PID cascade control mode. Since the PID control is based on feedback principle, it can not adjust the large time delay object promptly, and often causes big overshoot. What's more, the fixed parameters of the controller in the changeable production environment often lead control effect not ideal.Taking into account the complex characteristics of the superheated steam temperature control system, two control schemes about state feedback control based on observer are applied to superheated steam temperature control system.(1) State feedback control based on observer with error integral feedback: in view of the model of the controlled object, the state observers with different orders are constructed, and the dynamic characteristics of the controlled object can be improved through state feedback control. Then introduce the integral feedback of the error to eliminate the steady state error. The simulation results show that the superheated steam temperature control system has better control performance and strong robustness when using state feedback control strategy based on observer with error integral feedback, and when the order of the observer is equal to the order of the controlled object, the control system work best.(2) State feedback control based on increment function observer(IFO-K?x): state feedback control based on increment function observer and PID control has been merged in the system.So it can both overcome the weakness that just using PID control an object with large time is not ideal, and also retain the advantage of PID control's strong robustness. The simulation results show that the proposed scheme has strong anti-interference and robustness, and the robustness of the incremental function observer is better than that of the full dimensional state observer when under the condition of choosing the same observer parameters.