供水系统模型辨识与动态特性分析

为掌握离心泵供水系统在不同工况下转速突变时的动态模型结构、运行情况及其特性,通过改进水泵供水系统的出口端阀门结构,搭建了新的离心泵调速供水试验系统.通过试验台的改进在试验中实现系统的阶跃输入扰动,较为准确地反映系统工况的变化并进行调速工况下的模型辨识试验.试验中使用虚拟仪器和高频电参数测量仪搭建测量系统,对供水系统中所需数据进行测量采集.试验基于阶跃响应辨识原理,采用最小二乘法,通过Matlab系统辨识工具箱对数据进行预处理并确定其传递函数,绘制所得传递函数的零极点图和阶跃响应曲线.对比分析发现,系统运行在升频的工况下时,其超调量和震荡情况明显大于系统运行在降频工况下.结果表明,离心泵供水系统是最小相位系统,数学模型为二阶惯性加时滞结构.其模型参数会随着工况的变化而改变,实时辨识和实时变参数控制更为适合该系统.

Model identification and dynamic characteristics analysis of water supply system

In order to study the dynamical model and characteristics of the process in which the motor speed of the centrifugal pump water supply system suddenly changes at different operating points, the experiment of model identification under speed regulation operating condition is conducted based on the design of centrifugal pump water supply experimental system with speed regulating which optimizes the outlet valve structure in water supply system. The new experiment system implement step disturbance as input signal and present the changes of operating points logically. Virtual instrument and high frequency electrical parameter measuring instrument are used for data collection. The experiment is designed based on the step response method, and the model structure is obtained from prior knowledge about this system, the model parameters are estimated in Matlab system identification tool box using the method of least squares. Based on the pole-zero diagrams obtained by Matlab, the changes on dynamical model parameters and characteristics of the system running at the speed-up condition and the speed-down condition are analyzed and compared. It is concluded that model parameters of this system change while the system runs at different operating points, the estimated model is minimum phase and stable, mathematical model for the system is second order inertia and lag structure. Real-time variable parameters identification and real-time control is more suitable for the system.