【作者】 曲亚鑫；

【导师】 刘吉臻；

【作者基本信息】 华北电力大学 ， 控制理论与控制工程， 2012， 博士

【摘要】 电站信息技术的大力发展,为基于数据驱动的运行优化研究提供了良好的平台,其中,基于电站实时／历史数据库中海量数据对复杂热力系统建模的方法已逐渐成为研究的热点课题之一。然而,运行数据不同于试验数据,有着许多不利于建模的特点,例如,变量间存在多重相关性、工况组合分布不均匀、过程存在非线性等,这些问题都严重阻碍着历史数据建模方法的发展和应用。针对这些问题,本文研究了基于偏最小二乘理论(Partial Least Squares projection to latent structures, PLS)的热工过程建模方法,较好地解决了上述问题。论文的主要内容和研究成果包括：1.分析了电站历史数据的特点,总结了基于历史数据建模方法的三个阶段,即数据准备、数据建模和模型验证。介绍了历史数据的常用预处理方法,常用的建模理论以及模型检验方法,阐述了拟合精度与预测精度的区别。2.回顾了PLS方法的发展历史及研究现状,介绍了PLS以特征提取思想解决变量间多重相关性的过程,并给出了利用交叉有效性确定提取成分个数以及PLS模型的常用辅助分析方法,最后总结了PLS的非线性建模方法。3.针对电站历史数据分布不均匀的特点,提出了建模样本选择的三点原则。借鉴于试验建模方法具有优质建模样本的思想,提出了以试验设计原理选择建模样本的方法。在分析比较了几种常见的试验设计方法后,确定了以均匀设计作为建模样本的选取原则,并给出了该方法的详细实现过程。最后通过仿真分析验证了建模样本均匀性对于提高模型精度的意义。4.以均匀设计为原则的建模样本选择方法在应用到实际热工过程时,会因变量间的多重相关性导致无法获得所要求的数据,针对这一问题,提出了先对原始数据进行PLS特征提取再进行均匀选择的方法,并分析了该方法的有效性。随后在此方法的基础上,提出了对原始数据进行正交信号修正(Orthogonal Signal Correction, OSC)的改进方法,进一步保证了均匀建模样本数据的获取。5.以热工过程中的再热汽温系统为例,介绍了基于历史数据的PLS建模方法应用过程。从能量平衡的原理出发,提出了以再热期望焓升(即单位流量蒸汽吸热能力)作为因变量的再热汽温建模方法,并对其影响因素进行了全面的定性分析,构建了火焰中心高度、入炉煤质等现场没有引入但却有着关键作用的中间变量。通过多组模型对比的方式验证了：1)以再热期望焓升作为因变量建模能有效地减轻再热汽温模型中的非线性成分,较好地反映汽温变化的本质；2)以均匀设计为原则的建模样本选择方法能有效地提高模型的预测能力。最后,给出了基于所建模型的再热汽温运行优化指导。更多还原

【Abstract】 Nowadays, the rapid development of information technology in power plant has provided a convenient platform for the study of data based operation optimization. In which, the modeling of complex thermodynamic system based on the huge amounts of data in the power plant real time/historical database is gradually becoming one of the hottest topics. However, the disadvantages of historical data seriously obstacle the development of modeling methods, such as variable multicollinearity, nonlinearity, non-uniformity distribution of working conditions and so on. To solve these issues, the dissertation studies thermal process modeling methods based on partial least squares projection to latent structures, which solves the problems above in a better way. The main contributions of this dissertation can be summarized as followings:1. The characteristics of the power plant historical data is analyzed, three stages of historical data modeling is summarized, namely, data preparation, modeling process and model validation. Some common pretreatments, modeling theories and model validation methods are introduced, and the difference between fitting precision and prediction precision is elaborated.2. The history of PLS development and current research situation are reviewed, the extraction process of PLS which solves multicollinearity is described, and the method of which determines the number of PLS extracted components by cross validation, some auxiliary analytical methods are introduced. Finally, PLS nonlinear modeling methods are summarized.3. With regard to the characteristic of uneven data distribution, three principles sample selection in historical data modeling are put forward and then method of modeling sample selection is also proposed. After the analysis of several common experimental design methods, the uniform design is determined as the principle of modeling sample selection. Finally, the significance of sample uniformity for improving prediction precision is verified through simulation.4. To solve the problem which no data can be required due to multicollinearity, method based on PLS transform and its improvement based on orthogonal signal correction are proposed, and both of their validity are analyzed through simulation.5. As an example of reheat steam temperature system in thermal process, PLS modeling method based on historical data is proposed. Starting from the energy balance principle, method with expected reheat enthalpy rise (which represents the heat-absorbing capacity of unit flow steam) as the dependent variable is put forward and its influencing factors are analyzed. Some variables which cannot be measured but really play a key role in the field are also constructed. The results show that:First, the model established with expected reheat enthalpy rise can effectively reduce the nonlinearity component of reheat steam temperature; Second, modeling sample selection based on uniform design principle can effectively improve the predictive precision of model.更多还原