Superheated Steam Temperature Control System Design Based On The Multi-controller Switching Method

Thermal power plant steam temperature control is a well-developed and frequentlyinnovated researching field．On the one hand, the DCS(distributed control system)based oncascade PID control strategy for power plant has been a normative and well-developedsystem． On the other hand，the more high criterions have been required for power plantspower supply quality, security performances and economy because of the market. Andsince the proportion of large units such as sub-vertical and super-critical growing unitshave been applied. Thermal complicated and variable thermal characteristics brought by alarge-capacity, multi-parameter characteristics have been made the existing controlstrategies not easy to meet the control request under the new situation. Therefore, a newresearch and application of control theory and strategies for thermal power plant steamtemperature control have urgent practical significance.The boiler of thermal power plants is a complex object of nonlinear, strong coupling,large delay, multi-variable, and a wide range of operating conditions. Based on the NO.2steam temperature of600MW a certain power plant which had the problems of bad controlquality and surpassing temperature easily, design method of super-heated steamtemperature control system is proposed based on the switching multi-controller.Correspondingly, the controller has been designed for each different model. And throughreal-time monitoring of its deviation determine, it is to switch the implementation of thecontroller or not. It is time to choose traditional digital PID control scheme when the timelag is in certain range. If the time lag is too large, the generalized predictive controller issuitable. Simulation results show that the dynamic characteristics of the superheated steamtemperature control of boiler have been significantly improved through the multi-controllerswitching method.