Application of Fractal Theory in Simulation of Ferromagnetic Elements' Hysteresis Loop in Transformer

The simulation of the transformer transient is one of the indispensable qualifications for improving the performance of transformer protection, the key technique of the transformer's transient simulation is the treatment of ferromagnetic elements' loop. Thus the shapes of the primary hysteresis loop and each internal secondary hysteresis loop in the identical magnetism conducting are analyzed, and then it is proposed that there are some fractal characteristics in the relation between them. The fractal phenomenon of the ferromagnetic elements' hysteresis loop in the transformer's transient simulation is first brought forward, the mutuality between the ferromagnetic elements' primary hysteresis loop and its secondary hysteresis loops is revealed in mechanism by using the fractal theory. According to the iterated function system of fractal theory, the secondary hysteresis loops can be generated by the iterative calculation of the primary loop. The simulation results show the validity of this idea.

Non Linear Magnetic Hysteresis Modelling by Finite Volume Method for Jiles-Atherton Model Optimizing by a Genetic Algorithm

This paper describes a generalization methodology for nonlinear magnetic field calculation applied on two-dimensional (2-D) finite Volume geometry by incorporating a Jiles-Atherton scalar hysteresis model. The scheme is based upon the definition of modified governing equation derived from Maxwell’s equations considered the magnetization M. This paper shows how to extract optimal parameters for the Jiles-Atherton model of hysteresis by a real coded genetic algorithm approach. The parameters identification is performed by minimizing the mean squared error between experimental and simulated magnetic field curves. The calculated results are validated by experiences performed in an SST’s frame.

A Nonlinear Observer Approach of SOC Estimation Based on Hysteresis Model for Lithium-ion Battery

In this paper, a state of charge U+0028 SOC U+0029 estimation approach for lithium-ion battery based on equivalent circuit model and the input-to-state stability U+0028 ISS U+0029 theory has been proposed. According to the electrochemical performance of lithiumion battery, the equivalent circuit model with two RC networks is established, which includes hysteresis characteristic in inner electrochemical response process. The nonlinear relation between open circuit voltage U+0028 OCV U+0029 and SOC is obtained from a rapid test. Exponential fitting method is used to identify the parameters of the model. A novel state observer based on ISS theory is designed for lithium-ion battery SOC estimation. The designed observer is tested on AMESim and Simulink co-simulation. The simulation results show that the proposed method has a high SOC estimation accuracy with an error of about 2 percent. © 2017 Chinese Association of Automation.

Magnetic hysteresis, compensation behaviors, and phase diagrams of bilayer honeycomb lattices

Magnetic behaviors of the Ising system with bilayer honeycomb lattice（BHL） structure are studied by using the effective-field theory（EFT） with correlations. The effects of the interaction parameters on the magnetic properties of the system such as the hysteresis and compensation behaviors as well as phase diagrams are investigated. Moreover, when the hysteresis behaviors of the system are examined, single and double hysteresis loops are observed for various values of the interaction parameters. We obtain the L-, Q-, P-, and S-type compensation behaviors in the system. We also observe that the phase diagrams only exhibit the second-order phase transition. Hence, the system does not show the tricritical point（TCP）.

Random crystal field effect on hysteresis loops and compensation behavior of mixed spin-(1,3/2) Ising system

Magnetic hysteresis and compensation behavior of a mixed spin-（1, 3/2） Ising model on a square lattice are investigated in the framework of effective field theory based on a probability distribution technique. The effect of random crystal field, ferromagnetic and ferrimagnetic exchange interaction on hysteresis loops and compensation phenomenon are discussed. A number of characteristic phenomena have been reported such as the observation of triple hysteresis loops at low temperatures and for negative values of random crystal field. Critical and double compensation temperatures have been also found. The obtained results are also compared to some previous works.

A Novel Fuzzy—Adaptive Hysteresis Controller Based Three Phase Four Wire-Four Leg Shunt Active Filter for Harmonic and Reactive Power Compensation

This paper presents a fuzzy logic based three phase four wire four-leg shunt active power filter to suppress harmonic currents. Modified instantaneous p-q theory is adopted for calculating the compensating current. Fuzzy-adaptive hysteresis band technique is applied for the current control to derive the switching signals for the voltage source inverter. A fuzzy logic controller is developed to control the voltage of the DC capacitor. Computer simulations are carried out on a sample power system to demonstrate the suitability of the proposed control strategy, for harmonic reduction under three different conditions namely, ideal, unbalance, unbalance and distorted source voltage conditions. The proposed control strategy is found to be effective to reduce the harmonics and compensate reactive power and neutral current and balance load currents under ideal and non-ideal source voltage conditions.

“Extreme utilization” theory and practice in gas storages with complex geological conditions

Based on more than 20-year operation of gas storages with complex geological conditions and a series of research findings, the pressure-bearing dynamics mechanism of geological body is revealed. With the discovery of gas-water flowing law of multi-cycle relative permeability hysteresis and differential utilization in zones, the extreme utilization theory targeting at the maximum amount of stored gas, maximum injection-production capacity and maximum efficiency in space utilization is proposed to support the three-in-one evaluation method of the maximum pressure-bearing capacity of geological body, maximum well production capacity and maximum peak shaving capacity of storage space. This study realizes the full potential of gas storage(storage capacity) at maximum pressure, maximum formation-wellbore coordinate production, optimum well spacing density match with finite-time unsteady flow, and peaking shaving capacity at minimum pressure, achieving perfect balance between security and capacity. Operation in gas storages, such as Hutubi in Xinjiang, Xiangguosi in Xinan, and Shuang6 in Liaohe, proves that extreme utilization theory has promoted high quality development of gas storages in China.

On the Damped Beams with Hysteresis

This paper discusses the hysteretic behavior of beams with external elements made from auxetic materials. The damping force is modeled by using the nonlocal theory. Unlike the local models, the damping force is modeled as a weighted average of the velocity field over the temporal and spatial domains, determined by a kernel function based on distance measures. The hysteresis operator is continuous and it is defined in con-nection with the Euler-Bernoulli equation. The problem is solved by reducing it to a system of differential inclusions.

Improved Control in Single Phase Inverter Grid-Tied PV System Using Modified PQ Theory

Grid-connected reactive-load compensation and harmonic control are becoming a central topic as photovoltaic(PV)grid-connected systems diversified.This research aims to produce a high-performance inverter with a fast dynamic response for accurate reference tracking and a low total har-monic distortion(THD)even under nonlinear load applications by improving its control scheme.The proposed system is expected to operate in both stand-alone mode and grid-connected mode.In stand-alone mode,the proposed controller supplies power to critical loads,alternatively during grid-connected mode provide excess energy to the utility.A modified variable step incremental conductance(VS-InCond)algorithm is designed to extract maximum power from PV.Whereas the proposed inverter controller is achieved by using a modified PQ theory with double-band hysteresis current controller(PQ-DBHCC)to produce a reference current based on a decomposition of a single-phase load current.The nonlinear rectifier loads often create significant distortion in the output voltage of single-phase inverters,due to excessive current harmonics in the grid.Therefore,the proposed method generates a close-loop reference current for the switching scheme,hence,minimizing the inverter voltage distortion caused by the excessive grid current harmonics.The simulation findings suggest the proposed control technique can effectively yield more than 97%of power conversion efficiency while suppressing the grid current THD by less than 2%and maintaining the unity power factor at the grid side.The efficacy of the proposed controller is simulated using MATLAB/Simulink.

根据Vrentas-Vrentas理论模拟小麦粉的水分吸附滞后:模型参数χ及k表示为Fermi函数的形式

水分吸附及其滞后现象广泛存在并对食品加工及食品品质具有重要影响。采用动态水蒸气吸附分析仪测定了小麦粉在3个温度条件下的吸湿、解吸平衡水分,然后基于Vrentas-Vrentas(VV)理论进行模拟分析。结果显示,小麦粉的水分吸附滞后程度随温度升高而减小,吸湿与解吸曲线在高水分区域重合,据此提出一个确定玻璃化转变水分的方法。不论吸湿还是解吸,其Flory-Huggins相互作用系数χ皆随水分体积分数而变化,本实验提出采用Peleg改进的Fermi函数表示这种关系。在根据吸湿的χ参数模拟解吸时,VV模型中的参数k随体积分数变化可以表示为Fermi函数的形式。

一种用于变压器直流偏磁状态下的改进型Jiles-Atherton模型

Jiles-Atherton(J-A)理论在半宏观磁滞建模领域应用广泛。但因存在仅包含交流分量、对偏磁状态下的磁滞曲线描述不完整等缺陷,致使基于其建立的变压器直流偏磁模型存在较大误差。首先对正常励磁状态下的J-A公式进行推导修正。基于此通过引入直流分量,改进了J-A理论在直流偏磁状态下的无磁滞磁化曲线和磁化强度的微分表达式,并对其牵制系数k进行修正。接着提出一种基于改进J-A公式的变压器直流偏磁模型。最后,用一台500 kV电网的算例变压器来验证改进J-A公式用于变压器直流偏磁时的准确性。经验证,修正模型仿真结果与实测数据误差更小,在不改变原J-A理论物理机制的前提下改进模型能得到偏磁状态下的非对称磁滞曲线且可以更加精确的描述励磁电流值。

An effective-field theory study of hexagonal Ising nanowire: Thermal and magnetic properties

By means of the effective-field theory （EFT） with correlations, the thermodynamic and magnetic quantities （such as magnetization, susceptibility, internal energy, specific heat, free energy, hysteresis curves, and compensation behaviors） of the spin-l/2 hexagonal Ising nanowire （HIN） system with core/shell structure have been presented. The hysteresis curves are obtained for different values of the system parameters, in both ferromagnetic and antiferromagnetic cases. It has been shown that the system only undergoes a second-order phase transition. Moreover, from the thermal variations of the total magnetization, the five compensation types can be found under certain conditions, namely the Q-, R-, S-, P-, and N-types.

复杂地质条件储气库“极限动用”理论与实践

针对复杂地质条件储气库,基于20余年的运行实践,结合储气库系列攻关成果,揭示了储气地质体承压动力学机制,发现了“多轮相渗滞后”和“分区差异动用”气水互驱渗流规律,提出了以“储气库储气最多、井注入产出能力最大、空间利用效率最高”为目标的复杂地质条件储气库“极限动用”理论,形成了储气地质体极限承压、井极限产能、储气空间极限调峰能力三位一体的评价方法。实现了储气地质体在上限压力条件下获得最大储气空间(库容)、充分发挥地层-井筒气体流动协调的井极限产能以及满足有限时率不稳定渗流条件的最佳井网密度,获得下限压力条件下的最大调峰能力,达到安全和能力的双重极限效果。新疆呼图壁、西南相国寺、辽河双6等地下储气库的运行实践证明,“极限动用”理论有力推动了中国储气库业务高质量发展。

考虑剩磁作用的中低速磁浮电磁力分析

为了探究悬浮电磁铁剩磁对EMS(electro-magnetic suspension)中低速磁浮列车垂向电磁力的影响,首先,分析了悬浮电磁铁相对磁导率变化规律,并基于等效磁路法建立单电磁铁悬浮模型;其次,根据Jiles-Atherton磁滞理论研究了悬浮电磁铁的极限磁滞回线状态,分析了悬浮电磁铁剩磁的动态作用;最后,通过电磁力台架试验开展垂向电磁力对比验证,并提出了最大化利用电磁效率的措施.研究结果表明:在线圈电流处于0~20 A时,悬浮电磁铁剩磁近似等于常量,垂向电磁力的主要影响因素是线圈电流;在线圈电流处于20~40 A时,悬浮电磁铁达到磁饱和状态,且由于处于极限磁滞状态使得悬浮电磁铁具有最大剩磁作用,最大差值约为1 kN,随着线圈电流进一步增加,悬浮电磁铁相对磁导率的降低使得剩磁作用逐渐减弱.

基于SAE模型和Play算子的矢量磁滞模型研究

构建精确的矢量磁滞模型对电工装备电磁场数值分析是必要的。本文基于深度堆叠自编码器(SAE)模型结合磁滞算子空间理论提出了一种矢量磁滞模型。在模型结构中利用多个Play磁滞算子构建算子空间,样本中的磁场强度数据输入算子空间生成高维磁化状态矢量数据。该数据作为SAE模型的输入,利用SAE模型表征磁化状态矢量数据与模型输出磁感应强度的复杂非线性关系。通过训练样本生成的数据构建训练集和训练模型,获得SAE模型的参数。对测试数据的拟合结果表明:构建的模型可以有效地描述铁磁材料在旋转磁化情况下的非线性特性和各向异性。同时,对模型施加螺旋励磁,输出表明构建的模型可以有效地体现材料的矢量磁化特性。

J-A磁化建模理论的质疑与修正方法研究

J-A理论在磁建模领域应用广泛,但因存在多种版本,致使应用时对分析结果的正确性难以甄别。从无磁滞磁化曲线表达、采用的能量守恒方程等方面出发,对描述材料磁滞现象的原J-A理论的数学描述提出了质疑,指出了其中的不合理及错误之处。基于材料的磁化物理机制,通过分析给出了正确的能量守恒等式,并藉此推导出J-A理论的修正表征形式。由非线性寻优算法求得模型参数后,针对不同材料样本开展了仿真研究,并与测量数据进行比较,结果表明:相比于原J-A模型,本文提出的修正模型的仿真结果与材料的实测磁特性数据吻合较好,可更准确地模拟磁材料的磁化物理过程。

基于对偶性原理的三相多芯柱变压器暂态模型

提出了一种基于对偶性原理的三相多芯柱变压器暂态模型；通过分析三相多芯柱变压器磁路模型并应用对偶性原理,建立了考虑电路与磁路耦合的变压器暂态计算模型,采用Jiles—Atherton铁磁磁滞模型来描述铁心模块的饱和以及磁滞效应,而涡流和杂散损耗用一个等值电阻替代,零序磁通用一个线性电感以及反映其涡流损耗的电阻代替；该模型可以计算分析直流偏磁和空载合闸等情况下变压器励磁电流以及铁心磁通等电气参数；算例分析结果与实验结果的对比证明了该模型的准确性。

弹性体摩擦的黏滞疲劳理论及实验研究

为了更好地解决弹性体摩擦学方面的问题,建立了弹性体摩擦的黏滞疲劳理论,阐明了弹性体摩擦是粘附的表面拉伸效应和迟滞的体积变形效应的综合作用,揭示了弹性体磨损的本质机理是周期性疲劳破坏,解释了弹性体在摩擦过程中的各种特征现象.实验论证了黏滞疲劳理论在摩擦和磨损方面的可行性和精确性.通过建立的公式计算了弹性体的摩擦系数和摩擦力,并控制误差在6%的范围内;计算了弹性体的表观单位磨损率,并控制误差在7%的范围内.

基于迟滞行为的2D-SiC/SiC复合材料组份力学性能分析

基于剪滞理论,建立了单向纤维增强陶瓷基复合材料的加卸载理论模型,分析了基体长碎块和短碎块对材料迟滞力学行为的不同影响.通过拉伸循环加卸载试验,获得了2D-Si C/Si C复合材料的迟滞应力-应变行为.依据材料基体损伤特点,将试验结果代入长碎块对应理论推导结果,计算得到了4个表征材料组份性能的参数:基体开裂应力为90 MPa,热残余应力为19 MPa,界面脱粘能为3.1 Jm2,界面滑移力为74 MPa.最后结合少量短碎块的存在对试验结果的影响,定性分析了计算结果的偏差.结果表明,获得的材料组分性能参数具有较小的分散性,并能够准确表征材料整体的力学行为.

基于分形理论的变压器磁滞回环拟合新方法

正确地模拟变压器铁磁材料的动态磁化过程,掌握变压器铁磁材料的动态磁化规律,是提高变压器暂态仿真准确性的关键。作者首次运用分形理论中的基本观点,证明了铁磁材料的磁滞回环族是一种分形图形,从本质上揭示了铁磁材料动态磁化过程中所遵循的规律,从机理上探讨了变压器主、次磁滞回环之间的关系。在此基础上,应用分形学中迭代函数系统的基本理论,对铁磁材料的次磁滞回环拟合提出了一种“变压缩因子”方法,通过对主磁滞回环进行线性迭代压缩计算来生成次磁滞回环。仿真结果验证了这种方法的正确性。