基于奇异摄动法的降阶模型对系统稳定性的影响

电力系统含有大量非线性高阶的数学模型,电力系统稳定性分析时,不可避免地要采用简化的系统模型,文章首先对电力系统动态负荷模型和发电机模型进行了研究并进一步推导变形,然后采用奇异摄动法中多重时间尺度的思想将非线性的电力系统负荷模型分解成不同时间尺度下的几个子系统,并将高阶模型降阶为低阶模型,最后通过仿真得到一系列数据验证了奇异摄动法降阶后的模型更接近完整模型,所得结果偏差更小。摄动法使模型降阶有了依据,避免了经验降阶带来的较大误差。     

逐步多元回归法在负荷模型扩展中的应用

为了在仅已知负荷组成比例时求取该点的负荷模型,将统计学里的逐步多元回归法引入到负荷模型的扩展当中,首先通过少数已知负荷点的实测模型和负荷组成比例建立模型回归函数,然后通过此函数和待求负荷点的负荷组成概况推导出此负荷点的模型,在模型回归函数变量筛选时采用了逐步回归法,此方法克服了向前引入法和向后剔除法固有的缺点,由此方法建立的模型回归函数弥补了模型向量基法在负荷模型拓展时对实测负荷点个数要求过多的缺陷,为负荷模型的大范围推广提供了借鉴,实际负荷数据验证了该方法的有效性。     

动力锂电池最优等效电路模型研究

可靠的等效电路模型能够精确的模拟动力电池的充放电特性,是建立各种状态估计方法的基础。首先建立了锂电池Thevenin模型、DP模型,并采用带遗忘因子最小二乘法进行在线参数辨识,利用电路原理进行离线参数辨识。其次,在MATLAB/Simulink中结合实验数据对模型辨识精度和运算速度进行仿真验证。最后,基于辨识精度和运算速度建立模型评价方法,得出在线辨识过程DP模型相比于Thevenin模型能够在精度和速度方面取得更好的平衡;离线辨识过程,Thevenin模型能够取得更好的平衡。     

基于系统调用的手机APP能耗漏洞检测

针对传统研究中APP能耗漏洞模型存在尾部能耗与应用对象限制的问题,构建基于系统调用的能耗漏洞模型。首先使用集合交叉递归特征消除法选择影响每个类别APP能耗的重要系统调用作为特征,提高特征细化粒度。然后为每个类别APP构建多个回归模型,通过比较不同模型的平均绝对误差与决定系数,选择线性核支持向量机回归作为分类APP的能耗模型。最后基于测试集比较集合交叉递归特征消除法与交叉递归特征消除法所构模型的平均绝对误差,结果表明集合交叉递归特征消除法所构模型精度最多提高4.4%,同时基于测试集比较分类模型与未分类模型的平均绝对误差,结果表明分类模型精度最多提高6.7%,并且分类模型能准确检测出APP历史版本的能耗漏洞。     

动力锂电池最优等效电路模型研究

可靠的等效电路模型能够精确的模拟动力电池的充放电特性,是建立各种状态估计方法的基础。首先建立了锂电池Thevenin模型、DP模型,并采用带遗忘因子最小二乘法进行在线参数辨识,利用电路原理进行离线参数辨识。其次,在MATLAB/Simulink中结合实验数据对模型辨识精度和运算速度进行仿真验证。最后,基于辨识精度和运算速度建立模型评价方法,得出在线辨识过程DP模型相比于Thevenin模型能够在精度和速度方面取得更好的平衡;离线辨识过程,Thevenin模型能够取得更好的平衡。     

10kV城市配电网可靠性基础参数预测方法分析

介绍了灰色模型预测法和非线性回归模型预测法的预测模型,分析了这两种预测方法的特点,在此基础上提出应根据历史数据的特点合理选择各种配电网可靠性基础参数的预测手段。以某地区配电网设备的故障率和预安排停电率为算例,阐述了各种预测方法的具体运用。算例预测结果表明:在样本容量小的情况下,当历史数据较平滑时灰色模型预测法有较大的优势;在存在不准确历史数据的情况下,采用非线性回归模型预测法更加准确。     

基于Shapley组合模型及神经网络的电能表需求预测研究

针对电能表需求预测问题,建立基于Shapley组合模型及神经网络的电能表合理优化分配模型,以提升需求预测精度.文章通过挖掘历史数据,采用Holt-Winters、BP神经网络和RBF神经网络模型对电能表需求分别进行预测、对比和分析,并且引入Shapley法对三类预测模型进行组合建模,求取相应模型的权重,获取最优的生产调度方案.仿真实验结果表明,RBF神经网络模型预测精度要高于BP神经网络和Holt-Winters模型.相较于单一模型,Shapley法组合模型具有更好的效果和实用性,有助于国家电网公司建立高效、科学的生产调度计划.     

超声波电机转速控制的动态模糊建模

超声波电机动态模型是实现其高性能转速控制的前提。设计基于模糊逻辑的辨识建模方法,建立了超声波电机系统动态模糊模型。在设计实验获取建模所需数据的基础上,采用等分区间法确定了模型结构,进而利用最小二乘法辨识得到了模型中的待定参数。模型输出与实验数据的对比表明,所建模糊模型精度较高,反映了驱动电压幅值、频率与电机转速之间的非线性动态关系,可以用于超声波电机性能分析与转速控制器设计。     

雷电屏蔽模型在线路雷击分析中的应用

绕击是输电线路雷击跳闸的主要原因,研究雷电屏蔽模型对线路雷电绕击计算及分析具有重要意义。详细阐述了几何法、电气几何模型法和物理模型法在绕击计算中的特点和应用条件,并对220 kV输电线路典型杆塔进行了绕击耐雷性能计算分析和比较。结果表明,几何法来源于小模型试验,与实际应用有一定差距;电气几何模型和物理模型计算得到的结果基本一致,都具有较强的工程应用性。     

基于差分进化法的锂电池模型参数辨识算法研究

基于二阶RC等效电路模型,采用差分进化法对模型参数进行离线辨识.相比于传统的最小二乘法辨识电池模型参数模型,差分进化法的鲁棒性好、辨识精度高,因此被广泛应用于求解优化问题.     

TLM法在线性动态电路中的应用

详细介绍了采用TLM法求解线性动态电路的过程 ,指出了TLM法具有物理概念清晰 ,计算稳定、快捷等优点     

TLM modelling using an SIMD computer

A major limitation of the transmission-line matrix (TLM) method used to solve Maxwell's equations is the long computation time required. The TLM scattering calculations involved can, however, be viewed as parallel in nature. This paper describes an effort to reduce computational time by using an SIMD, DAP multiprocessor computer employed to solve a two-dimensional TLM electromagnetic field formulation. A parallel algorithm based on the TLM scattering algorithm is designed and implemented using FORTRAN- PLUS Enhanced on an AMT DAP 510 machine. Here the connectivity of the DAP is exploited to simulate the intrinsic scattering behaviour on which the TLM algorithm relies. The results show that parallel processing on an SIMD machine such as the DAP is advantageous, especially for higher-order mesh sizes.     

Two-dimensional FDTD and TLM

Applying the method of moments to Maxwell's equations, Yee's two-dimensional FDTD scheme with central difference approximations and the two-dimensional TLM method are dervied from first principles of field theory. By comparing the eigenvalues of the two methods, the differences between two-dimensional FDTD and TLM are illustrated.     

TLM modelling of the diffusion approximation of queuing system

This paper provides an application of the TLM method to any queuing systems that can be approximated as a diffusion process. The TLM node has been extended in order to take into account the variables associated with the diffusion approximation of the queue, which is presented in Harrison, Patel, Performance Modelling of Communication Networks and Computer Architectures, Addison‐Wesley: Reading, MA, 1994. The analytical solution is compared with the TLM numerical results. Copyright © 2001 John Wiley & Sons, Ltd.     

Use of the two-dimensional TLM method in the electromagnetic simulation of thin semiconductor samples

A two-dimensional lossy shunt TLM node is incorporated into a TLM system and adapted to model for the first time the Maxwell field equations in thin semiconductor samples. Both the characteristics of the node and the TLM system itself are fully described. By considering a parallel-plate structure containing a thin GaAs sample, driven by a voltage source, it is shown, with an example, that this TLM technique can simulate the response of non-stationary electromagnetic fields in a semiconductor to applied excitations.     

Substructuring of space and time in TLM diffusion applications

A simple method is described for spatial substructuring of meshes used in TLM diffusion routines in such a way as to enable discontinuous mesh lines to be used. A method of operating TLM diffusion routines using different timesteps in different spatial regions is also described. For both aspects, results are compared with those derived using standard TLM techniques.     

Boundary conditions in TLM diffusion modelling

The connection algorithms used in transmission‐line matrix (TLM) modelling of diffusion processes for describing boundary conditions in both link‐line and link‐resistor nodal configurations have been derived. The new algorithms regarding the inhomogeneous Robin condition enhance the capability of the TLM method in simulating thermal or particle diffusion phenomena. A number of boundary treatments in the existing literature have been found to be special cases of our results. The Dirichlet‐type boundary condition is also discussed. TLM numerical results using the new algorithms, particularly with the link‐resistor model for achieving signal synchronization, are shown to be in excellent agreement with the available analytical solutions. Copyright © 2006 John Wiley & Sons, Ltd.     

A method for algebraic analysis of the TLM algorithm

An analogy is described between the TLM algorithm and discrete state-space control theory. The analogy is used to derive the characteristic equations corresponding to parametrized model structures. Characteristic equations corresponding to several widely used node structures are derived by this means and found to be consistent with the observed behaviour of corresponding TLM models. An example is given of the use of the analogy in teh predictive mode.     

The calculation of radar cross-section (RCS) using the TLM method

The calculation of the radar cross-section (RCS) of complex bodies using the symmetrical condensed TLM method is presented. The technique is based on a near-to-far field transformation of the TLM calculated near fields. Several two-dimensional examples are presented which validate the method. The main advantage of utilizing techniques such as TLM for RCS computation lies in the ability to model arbitrary bodies with complex material compositions.     

An investigation of the different TLM configurations used in the modelling of diffusion problems

The commonly used transmission-line modelling (TLM) network of one-dimensional diffusion problems often results in unwanted oscillations. Two different TLM configurations (line boundary (LB) and resistance boundary (RB)), are investigated with some techniques necessary to reduce the oscillations. Comparisons between the various LB and RB models addressed in this paper, indicate that, in general, two-dimensional TLM models produce consistently more accurate results.