谐振式无线电能传输系统负载特性的分析与优化

研究谐振式无线电能传输系统的电阻负载特性以及对传输效率和输出功率的优化方案.在耦合系数、工作频率一定的前提下,通过理论推导得到传输效率、输出功率与系统负载关系.研究表明,谐振式无线电能传输系统的最大传输效率与最大输出功率所对应的系统负载之间存在最佳负载值,它是改善系统输出功率和传输效率的有效途径.最后,搭建一个小功率谐振式无线电能传输系统平台,实验结果与理论分析结论相一致.     

感应电能传输系统参数辨识与恒流控制

针对感应电能传输系统中激磁电流(谐振电流)的控制问题,本文提出一种基于参数动态辨识的恒流控制策略。该方法从能量分析的角度,建立了系统谐振回路中能量存储、供给与耗散函数,通过分别建立系统周期内与周期间的能量平衡关系,得到了系统反射阻抗的辨识函数。该方法提出了采用Buck变换器控制系统输入电压以实现谐振电流恒流的控制方案。基于系统输入电压与谐振电流峰值包络的函数关系,结合Buck变换器的输入输出函数关系,建立了系统的恒流控制律。通过实验验证了该控制方法的可行性。该方法的参数辨识环节仅需采样原边部分的谐振电流和电压过零采样数据,简化了系统的采样系统设计。而基于参数辨识的恒流控制律不需要复杂的算法计算,易于实现。     

感应电能传输系统环流抑制方法

感应电能传输技术是一种利用磁场耦合来实现电能以无接触的方式进行传输的技术。在系统中,由于开关管在谐振电容电压非零点切换会导致环流的出现。环流使谐振电容电压波形发生畸变,EMI增强,开关管损耗增大,严重影响系统的稳定性和传输效率 ［6］。通过分析指出谐振频率变化是环流产生的原因。通过分析开关管在谐振电压过零点之前和过零点之后切换时环流的特点以及开关频率与谐振频率之间的关系,提出一种通过实时检测环流方向,动态调节开关频率与谐振频率一致,以保证开关管在谐振电容电压过零点切换,从而抑制环流。给出了以FPGA芯片为载体的环流抑制系统的设计方案。通过搭建硬件电路验证了该控制方法的有效性。     

磁谐振无线电能传输功率关系及频率失谐分析

为了进一步了解磁谐振无线电能系统参数和传输特性之间的关系以及线圈固有谐振频率失谐和传输特性之间的关系,首先通过能量守恒定律对系统的功率关系进行了分析,接着通过定义线圈的广义失谐因子对磁谐振无线电能传输系统的失谐机理进行了分析,最后通过50 k Hz的无线传输系统对理论分析的正确性进行验证。研究结果表明,在传输距离为20 cm的情况下,当系统失谐时,其传输效率为74.79%,传输功率为271.27 W;当系统谐振时,其传输效率为80.08%,传输功率为285.66 W。磁谐振无线电能传输系统满足复功率守恒,且在线圈的固有谐振频率发生偏移时,其传输效率和传输功率均会降低。     

宽频磁耦合谐振式无线电能传输系统谐振器设计

为提高谐振式无线电能传输系统的工作频率范围并定量化设计谐振器的参数,首先根据谐振式无线电能传输原理,建立电路模型方程,研究了系统传输特性与谐振器线圈参数之间的关系,在指定谐振频率、传输距离、负载和接收功率情况下,实现线圈半径及匝数等参数的选取方法.同时在谐振器参数给定情况下,仿真分析了负载功率、发射线圈电流、传输效率等传输特性随传输距离的变化特性.最终,结合所设计研制的宽频磁耦合谐振式无线电能传输系统,通过试验对理论推导和仿真计算进行了进一步验证,试验结果与理论分析和仿真结果相吻合.      

具有恒流恒频恒压特性的IPT系统参数设计

针对传统恒流恒频恒压控制方法须额外增加开关电路和闭环控制存在的缺点,以谐振网络拓扑为原边并联-副边串联型(PS型)的感应电能传输(IPT)系统为研究对象,基于交流阻抗法,推导出原边谐振电流、系统谐振工作频率和负载输出电压近似恒定的约束条件.从而提出一种谐振网络参数的综合设计流程,使得系统在所设计的负载范围内,就能自然地保证原边谐振电流、系统谐振工作频率和负载输出电压同时近似恒定.该方法不加额外辅助开关电路便可同时实现恒流、恒频和恒压,具有良好的负载兼容性.仿真及实验结果验证了这种具有恒流恒频恒压特性的参数设计流程的正确性和有效性.     

电磁谐振无线能量传输系统参数研究

谐振线圈参数直接影响电磁谐振无线能量传输系统的效率,研究线圈参数与传输效率之间的关系,对无线传能系统的研究和设计有着非常重要的意义.推导了电磁谐振无线传能系统的数学模型,并利用Matlab对系统的频率、线圈半径、线圈匝数、线圈长度、线圈间距离等参数进行了仿真研究.研究结果指出了系统各参数变化时对系统效率影响,频率、线圈半径和线圈匝数等参数增大有利于提高传输效率,但增大到一定程度后对效率的影响不再明显;线圈长度和线圈间距离增加会降低系统效率,但可以通过提高系统频率来进行补偿.     

无线电能传输效率优化

基于无线电能传输系统模型,通过系统一次侧和二次侧的电压回路方程及引入的系统一次侧和二次侧频率漂移因子,给出了电源输入侧的系统阻抗表达式及系统总电能传输效率表达式。针对系统频率漂移影响电能传输效率的问题,设计了一种系统电能传输效率的优化方案。在系统负载范围内,计算出了系统的最优谐振频率及不同负载水平下的最佳电能传输效率。系统频率漂移时,通过调节相关参数使系统工作在最优电能传输效率状态。系统仿真结果表明,系统频率漂移时,根据本文提出的方法能够有效提升电能传输效率。     

压电换能器功率输出自动调节特征研究

为了研究换能器的工作安全性能、提高换能器的系统效率,根据压电换能器的工作原理,利用等效电路方法,分析了压电换能器在并联谐振频率附近工作时的频率特性,得出了在并联谐振频率附近的功率输出自动调节规律,应用该规律探讨了功率输出自动调节的频率范围,并对超声清洗换能器在不同负载时的功率输出进行了实验。结果表明:换能器在并联谐振频率附近工作时具有较好的功率输出自动调节功能,对提高换能器的系统效率有一定指导意义。     

电流型CPT系统传输功率调节方法

针对现有电流型CPT系统初级谐振回路能量调节存在的不足,提出了一种能够实现Buck和Boost两种工作模式的电路拓扑和控制方法,从而拓宽了系统传输功率调节范围.论文对改进后的拓扑进行了建模,推导了在两种模式下传输功率与占空比的函数关系,为系统的分析和设计提供了理论依据.使用Simulink和PLECS对PP型CPT系统进行仿真,仿真结论证实了理论分析结果.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with