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基于PI-DMC的发电机组主蒸汽温度串级前馈预测控制策略

Cascade Feedforward Predictive Control Strategy for Main Steam Temperature of Generator Units Based on PI-DMC

  • 摘要: 针对发电机组主蒸汽温度控制系统惯性大、时滞长、扰动大的特点,结合比例积分微分(PI)控制和动态矩阵控制(DMC)的优点,提出一种基于PI-DMC的发电机组主蒸汽温度串级前馈预测控制策略。以控制量为燃料量、被控量为主蒸汽温度,利用遗忘因子递推最小二乘法对主蒸汽温度控制系统模型参数进行辨识;通过对模型施加单位阶跃信号得到预测模型,并通过反馈校正在线修正预测值;对目标函数实时滚动优化得到当前时刻控制量,并设定控制权重对PI和DMC进行优化组合。仿真结果表明:与串级PID和DMC控制相比,提出的控制策略在模型适配且施加干扰时,调节时间约20 s、超调量仅6.47%;在模型失配且施加干扰时,调节时间约30 s、超调量为6.03%。工程应用结果表明:相较于工业现场原控制策略,提出的控制策略控制精度提高了66.91%,同时汽包液位的控制精度提高了47.23%,符合现场设计要求。

     

    Abstract: Aiming at the characteristics of large inertia, long time delay, and large disturbance in the main steam temperature control system of power generation units, combined with the advantages of PI control and DMC, a PI-DMC based cascade feedforward predictive control strategy for the main steam temperature of power generation units was proposed. Using the control quantity as the fuel quantity and the controlled quantity as the main steam temperature, the forgetting factor recursive least squares method was used to identify the model parameters of the main steam temperature control system. By applying a unit step signal to the model, a predictive model was obtained, and the predictive value was corrected online through feedback correction. Real time rolling optimization of the objective function was performed to obtain the current control amount, and control weights were set to optimize the combination of PI and DMC. The simulation results show that compared with cascade PID control and DMC control, the proposed control strategy has a tuning time of about 20 s and an overshoot of only 6.47% when the model is adapted and interference is applied; When the model is mismatched and interference is applied, the adjustment time is about 30 s and the overshoot is 6.03%. The engineering application results show that compared to the original control strategy in the industrial field, the control accuracy of the proposed control strategy has increased by 66.91%, while the control accuracy of the drum liquid level has increased by 47.23%, which meets the on-site design requirements.

     

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