检索结果-内蒙古大学图书馆

Local basis function representations of thermodynamic surfaces: Water at high pressure and temperature as an example

引用

FLUID PHASE EQUILIBRIA 2018年 463卷 18-31页

作者： Brown, J. Michael Univ Washington Dept Earth & Space Sci Box 35-1310 Seattle WA 98195 USA

A flexible numerical framework using local basis function is developed in order to better represent thermodynamic properties of fluids as a function of pressure temperature and composition. A new equation of state for water to 100 GPa and 10,000 K is presented. Conventional equations of state are typically based on complex sets of global basis functions that are unique to each application. The use of series expansions in positive and negative powers of the independent variables (with additional exponential/log/trig. factors in some cases) is common and recent accurate equations of state are assembled from collections of such arbitrary terms. These individually crafted representations do not always fit data within uncertainties, can be difficult to implement, and are not easily modified to account for newer data. Multivariate (tensor) b splines overcome these shortcomings. The underlying basis functions are local, orthonormal and complete. Data can be represented to arbitrary precision and the relationships between model parameters and observational constraints are uncomplicated. The fittings of new data in more extended regimes of the thermodynamic space do not require modifying parameters in previously constrained regions. Models are transportable and easily implemented since robust and efficient standardized routines for evaluation of b splines are available in modern numerical environments. Because a local basis function representation can flexibly fit any surface, the articulation of a priori constraints (associated with expected physical and chemical behavior) is appropriately necessary and explicit during model construction. Basic tools are demonstrated in applications to thermodynamic properties of water where the modified equation of state matches a prior formulation below 1 GPa while providing an excellent fit to measurements at much higher pressures. (C) 2018 Elsevier B.V. All rights reserved.

关键词： b spline Local basis functions Equation of state Fluid thermodynamics regularized parameter estimation Water

来源：评论

学校读者我要写书评

暂无评论

Dependency Analysis and Improved parameter estimation for Dynamic Composite Load Modeling

引用

IEEE TRANSACTIONS ON POWER SYSTEMS 2017年第4期32卷 3287-3297页

作者： Zhang, Kaiqing Zhu, Hao Guo, Siming Univ Illinois Dept Elect & Comp Engn Urbana IL 61801 USA

Dynamic load modeling by fitting the input-output measurements during fault events is crucial for power system dynamic studies. The WECC composite load model (CMPLDW) has been developed recently to better represent fault-induced delayed-voltage-recovery (FIDVR) events, which are of increasing concern to electric utilities. However, the model nonlinearity and large number of parameters of the CMPLDW model pose severe identifiability issues and performance degradation for the measurement-based load modeling approach using the classical nonlinear least-squares (NLS) objective. This paper will first present a general framework that can effectively analyze and visualize the parameter dependence of complex dynamic load models with large numbers of parameters under FIDVR. Furthermore, we propose to improve the parameter estimation performance by regularizing the NLS error objective using a priori information about parameter values. Effectiveness of the proposed dependence analysis and parameter estimation scheme is validated using both synthetic and real measurement data during faults. Albeit focused on CMPLDW, the proposed approaches can be readily used for composite load modeling in general.

关键词： Dynamic load modeling measurement-based approach nonlinear system identification parameter sensitivity and dependency analysis regularized parameter estimation

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：