基于间接能量平衡的锅炉汽温GPC-PID串级控制

针对电站锅炉汽温对象由于存在大惯性、大时滞、非线性和难以建立精确模型,使得传统串级PID控制算法在满足AGC负荷响应快速性和准确性方面存在较大不足等问题,基于直接能量平衡思想,提出一种间接能量平衡法(IEBM)。通过IEBM构造并预测整定出反映变负荷工况的导前汽温设定值,把原串级控制系统中副控制器的随动控制功能改变为定值控制,从而达到间接控制锅炉主汽温和再热汽温的目的。由于系统能及时"预测"到汽温迟延受不同负荷的影响,导前汽温成为控制的主体,采用广义预测控制策略(GPC),而主回路仍然采用PID控制器,构成新型基于多模型RBF神经网络离线辨识的IEBM-GPC-PID串级控制系统。经现场实测数据仿真结果表明,提出的方法能够明显地提升汽温的控制效果,改善控制系统的鲁棒性。

GPC-PID cascade control strategy based on indirect energy balance method for boiler steam temperature system

Due to steam temperature characteristics of great inertia,pure time-delay,non-linear and diffi-cult to establish accurate models at power station,the conventional cascade PID controller is faced with significant shortcomings with its rapidity and accuracy of AGC’ s ( Automatic generation control) load re-sponse.Based on the fundamental idea of direct energy balance ( DEB) ,an indirect energy balance meth-od ( IEBM) was proposed which can construct and predict the setting values of intermediate steam tem-perature that varies with the load’ s command.It changed the inner controller in cascade system from orig-inal servo system into a constant value system so as to indirectly achieve the control of superheated and re-heated steam temperature of the boiler.The system timely predicts the delays of steam temperature varied with the influence of different loads,the intermediate steam temperature is designed as the main body of the control system which is adopted by the strategy of generalized predictive control ( GPC) ,and the pri-mary loop is still controlled by PID controller.In view of above-mentioned idea,a new type of IEBM-GPC-PID cascade control system was proposed by multi-model off-line identification through RBF neural net-work.Simulation results of the real data on site show that the proposed method can considerably improve the control effect of the steam temperature and the robustness of the control system.