基于状态反馈-预测控制的1000MW机组主汽压控制方法

Main Steam Pressure Control Method for 1000MW Units Based on State Feedback Controller and Predictive Control

针对1000MW超临界机组锅炉大惯性和时滞性的特点,利用预测控制中滚动优化的局部最优控制功能,来加强主汽压的控制能力。1000MW超临界机组AGC运行方式,在机组安全的基础上,以汽轮机功率为调节的第一优先级,且汽轮机调节快速准确,为减小对工业控制器计算能力的依赖,1000MW超临界机组预测控制仅用于机组主汽压控制,汽轮机功率控制仍采用原来的PID控制。1000MW超临界机组AGC正常调节时,相比于锅炉和主汽压的长周期调节,汽轮机功率可认为仅与AGC负荷指令相关,不受锅炉运行状态影响;此时,锅炉总煤量变化(燃水比不变)对主汽压力的影响是一个纯积分不稳定过程,无法设计应用预测控制,需要利用状态反馈控制器和LQR理论,在低成本投入条件下将这一不稳定过程整定成渐稳系统。仿真结果显示:基于状态反馈控制器和预测控制的1000MW超临界机组主汽压控制方法,明显优于传统的PID与前馈结合的控制方案。

Aim at the characteristics of great inertia and time-delay of 1000MW supercritical unit boiler,the control ability of main steam pressure is strengthen by the local optimal control function of rolling optimization in predictive control.On the basis of turbine safety,the turbine power is the first priority to the regulation performance for AGC operation mode of 1000MW supercritical unit,and the regulation performance of turbine is fast and accurate.In order to reduce the dependence on the computing power of industrial controller,the predictive control of 1000MW supercritical unit is only used for main steam pressure control.The turbine power control still adopts the original PID control.When AGC operation mode of 1000MW supercritical unit is normally regulated,compared with the long period regulation of boiler and main steam pressure,the steam turbine power can be considered to be only related to the AGC load order and not affected by boiler operation state.At this time,the effect of the change of the total coal quantity of the boiler(constant Firing Rate to Feed Water ratio,FR/FW)on the main steam pressure is a pure integral unstable process,which cannot be designed and applied in predictive control.It is necessary to use the state feedback controller and LQR theory to set the unstable process into a asymptotically stable system under the condition of low cost input.The simulation results show that the main steam pressure control method for 1000MW supercritical unit based on state feedback controller and predictive control is obviously superior to the traditional control scheme based on PID and feed-forward.