| At present, control of steam-gas exit temperature has high requirements and bad controllability in the process of superheated steam temperature control in power plant. There are very strict requirements to the quality of superheated steam temperature control in craftwork, which plays an important role in security and economy run of power plant. Due to the characteristics of super-heater such as great lag, nonlinear, time-varying, multivariable and self-balance, that how to improve the control quality of superheated steam temperature has become the significant research topic in thermal process control field.It analyzes the characteristic of super-heater which is the controlled object in the article, depicts cascade control in common use comparatively detailed, Smith predictive control and the system configuration and theory of fuzzy control. In addition, it also simulates cascade control of superheated steam temperature and Smith predictive control system after the mathematical model has been added into gas, steam disturbance and super-heater, the controlled object, changed, and indicates effect of object's mathematics model changed to both of the control process. So conclusion has certain limitation.Paper puts forward cascade fuzzy control strategy according to the characteristics of super-heater like great lag, nonlinear, time-varying, multivariable and the control requirements of superheated steam temperature in power plant. Its main objective is to make combination and complementary of advantages in order to explore the effective approach to improve the control quality of superheated steam temperature.Through analyzing the process of superheated steam temperature control in power plant practically and considering that leading segment temperature of super-heater in power plant can reflect superheated steam temperature's trend of insert segment exit of super-heater, power plant has no special requirements for leading segment temperature of super-heater, so it is the most ordinary control formula in fuzzy control to get leading segment temperature of super-heater and change rate as the input of fuzzy control, this reflects PD control rule in superheated steam temperature cascade fuzzy control system. And the control formula is beneficial to improve control performance of superheated steam temperature cascade fuzzy control system.The result of simulation indicates that superheated steam temperature cascade fuzzy control system is independent of mathematic model of controlled object and its control quality is better than superheated steam temperature cascade control system after being added into gas, steam disturbance and super-heater, the changed controlled object, which is beneficial to power plant to realize safe, economic, credibly, optimized, environmental requirements and it should have wide application foreground. |
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