PFC-PID串级控制在主汽温控制系统中的应用研究

针对火电厂主汽温控制系统大惯性，大迟延，慢时变以及扰动因素较多，常规串级PID控制难以取得满意的调节效果的特点，该文介绍并分析了预测函数控制（PFC）的基本原理和特点，给出了一阶加纯滞后系统的预测函数控制的具体算法，并将PFC和PID控制相结合，提出了PFC－PID串级主汽温控制策略，系统的内回路采用PID控制，内回路和主调节区对象构成PFC的广义被控对象，对广义被控对象进行拟合简化得到一阶加纯滞后对象，作为PFC的预测模型，算法简单；预测模型失配时，系统仍具有良好的控制品质，易于工程实现，具有较高实际应用价值，大量的仿真实验表明，采用PFC－PID串级控制策略的主汽温控制系统的动态品质明显优于采用PID串级控制策略的系统，具有较强的鲁棒性和抗干扰能力。

STUDIES AND APPLICATIONS OF PFC-PID CASCADE CONTROL STRAGETY IN MAIN STEAM TEMPERATURE CONTROL SYSTEM

Main steam temperature control system in thermal power plant is a system with large time constant, long time-delay, slow time-varying and various of disturbance factors, traditional PID control generally can't satisfy the performance requirement. This paper introduces and analyses the basic theory and properties of Predictive Functional Control(PFC). The algorithm of first-order plus dead-time system is provided particularly. PFC-PID cascade control strategy is given out by combining PFC with PID control, and applied to main steam temperature control system in thermal power plant. Internal loop of the system adopts PID control strategy, and internal loop and the super-heater high temperature plant constitute generalized control plant of PFC. The control algorithm is simple because predictive model of PFC is first-order plus dead-time model which is gained by matching generalized control plant. Furthermore, the system with unmatched model still has favourable quality. Therefore the strategy is easy to be realized in computer or distributed control system(DCS), so it has hopeful application prospect. Many computer simulation results show that the advanced control strategy has more favorable dynamic characteristics than PID cascade control strategy in main steam temperature system, disturbance rejection and robustness.