The Design Of Double-mode Control Strategy Of Superheated Steam Temperature For Ultra-supercritical Power Units

Currently, due to the increasing in electricity generating capacity led to more and more, while on the grid peaking requirements more stringent. Therefore, the unit is high quality automation system control requirements, and superheated steam temperature as an extremely important indicator of the quality of the thermal power plant to run its direct impact on the control of plant operation safety and economy. As the superheated steam temperature system of nonlinear, time-varying, large delay, large inertia, etc., and based on the conventional PID Cascade Control fixed mathematical model of weak anti-interference ability, adaptability to changes in the working conditions poor, the response is slow, difficult achieve satisfactory control effect.Currently internal model control algorithm has better control effect in superheated steam temperature control system in each plant. Internal model control system has a simple structure, regulate the precise performance, good steady-state performance, robustness and strong anti-interference ability and other characteristics, which in many industrial areas get the attention of experts and scholars, on the internal model control optimization research and practical application of work carried out in full swing. However, there are also their own internal model control deficiencies:When the controller model and the actual controlled object model mismatch control results in severe cases will decline. In addition to the internal model control, fuzzy control has been applied widely. Fuzzy Control is an intelligent control strategy does not rely on a mathematical model object, a strong argument variable conditions of high adaptability of the control algorithm. Fuzzy Control is extremely suitable for nonlinear, large delay, large inertia characteristics of the production of industrial objects, but due to fuzzy control of nonlinear proportional plus derivative control is similar, and therefore better control dynamic performance and steady-state performance is poor.Therefore, combining the advantages of the internal model control and fuzzy control, proposed two modal control strategy that, according to the deviation of superheated steam temperature setpoint and the actual value to switch control algorithm:if the deviation is large, the system switches to fuzzy control algorithm using fuzzy control dynamic performance, fast track and quickly reduced input bias deviation; when the temperature deviation is small internal model controller adjusts excellent performance, essentially eliminates static bias throughout the dynamic control process will be charged according to the actual object Characteristics to switch to the appropriate controller to ensure that the system has good control quality and stability.Following this strategy through matlab simulation experiments have good control effect, applied to a660MW ultra-supercritical thermal power units superheated steam temperature control unit during commissioning, use Guodian Zhishen DCS logic of the control strategy configuration and debugging. DCS commissioning results show that:the control strategy can be a good way to overcome the impact of changes brought about by the working conditions, anti-interference ability, reflecting the strong load adaptability and excellent control quality.