关于对称三相电路无功功率测量的讨论

三相电路功率及其测量是电路教学中三相电路部分的重要内容.本文结合教学实践讨论了教科书中的对称三相电路无功功率测量的两种方法,指出这两种方法都与三相电路的相序及电路的接法有关.通过在三相电路中接入由电容构成的对称三相负载,给出了在未知三相电路相序的情况下用功率表测量相序的方法.进一步讨论了测量对称三相电路功率的方法,该方法有别于教科书所介绍的方法.     

“两表法测量三相电路有功功率”实验方案探讨

无论理论分析或工程实践都证明了用两表法测三相三线制电路有功功率时,两只单相功率表按接线原则正确接线仍可能发生一只功率表指针反偏(指示值为负)的情形。因此,在两表法测三相电路有功功率的实验教学中,应让学生观察到接线正确却仍有一表指针反偏的情形。     

三电平光伏逆变器的新型控制策略研究

光伏逆变器是光伏发电系统的核心部分,对光伏逆变器最大功率点跟踪(MPPT)至关重要,它的效率高低直接影响着整个并网系统的效率.从电气安全的角度考虑,逆变器需要采用三相四线制接线方式.文章针对这种三相四线制三电平光伏逆变器提出一种基于DSP2812的新型的控制方法.     

论低压三相四线有功表接线的计量影响及优化策略

三相四线有功表的主要应用范围为客户终端,属于目前常用的对电量进行有效计算的设备。一般而言,三相四线有功表主要在我国乡镇单位大面积使用,为了保障乡镇的用电安全,在对低压三相四线有功表进行安装调试时,应重点查看其接线位置,并及时校对计量的准确性和真实性,若相关技术人员没有依据当地的用电环境,盲目更换有功表或者随意接线,就很容易引发用电表故障甚至用电安全。本文针对上述问题,主要介绍了低压三相四线有功表的运作模式和计量方法,对其接线进行研究并探讨优化接线对电表工作的影响。     

基于Multisim的三相电路仿真

三相电路是日常生产和生活中应用广泛的电路,通过实验方法研究和分析三相电路的运行情况显得很有必要,但由于三相电路的实验有一定的危险性,而且某些故障性实验可能会对元件甚至整个电力系统造成破坏,因此三相电路的实验难以实施。通过三相负载对电路的影响的理论分析,阐述了供电系统中采用三相四线制的原因,并利用Multism仿真软件进行仿真。通过虚拟实验的方法验证了理论分析的结果,表明了运用Multism仿真是进行电路分析的一个有效手段。     

基于Multisim的三相电路仿真分析

在生产与生活中三相电路的应用最为广泛，针对三相电路运行工况的实验就显得重要而且必然，然而实际的三相电路实验不仅危险性较大，而且一些故障性试验较难进行。电路仿真软件Multisim提供了适用于三相电路仿真的各种元件模型及分析工具，利用该软件对三相电路的3种不对称短路故障进行了仿真分析，与理论分析比较的结果表明仿真软件效果理想。通过虚拟实验分析了负载变化对三相电路的影响，从而得出了照明线路为保持各相电压不变一般采用三相四线制的结论。两组实验表明利用Muttisim可以方便快捷地对三相电路进行各种实验分析。优点明显．适合在电工实验中推广。     

二瓦特计测量法的读数与无功功率的计算公式

有些电路教材证明了对称三相电路中,二瓦特计测量法功率表的读数,以及三相无功功率的计算公式,但是仅限于一种接表方法。本文归纳出利用对称负载的阻抗角,计算二瓦特计法表读数的一般规律。该规律不限于二瓦特计法,对仅用一块表来读数时也适用。然后导出了对称三相无功测量的计算公式。     

有源滤波器的三相四线制谐波检测新方法研究

基于瞬时无功理论的传统有源滤波器在三相四线制电路中不适用,文章针对这个问题,综合运用瞬时无功理论中的p-q方法和ipi-q方法,提出了一种新的基于瞬时无功理论的有效的三相四线制谐波检测新方法,将三相电流中的零序电流剔除,完善了p-q方法和ip-iq方法的不足,通过计算验证了该方法适用于任何三相电路,包括三相四线制电路,并且三相电压波形的畸变不影响检测结果的准确性。并用MATLAB仿真验证了该方法的准确性和有效性。该方法有效地解决了传统有源滤波器不适用于三相四线制电路的缺陷。     

PBL和LBL教学模式中二表法的体验

在“电路理论”课程中，三相电路功率测量的二表法是其中的一个难点。本文以学生的角度介绍在PBL与LBL教学模式下，对该内容的学习体会及对难题案例解决的自主学习探索。通过案例问题及伴随的新问题的解决，进一步加深了对课堂知识的理解，结合课堂外知识的学习，提高了学生应用知识综合解决问题的能力。     

三相四线制有源电力滤波器的设计与仿真

三相四线制有源电力滤波器能够很好地提高滤波器的滤波性能,实现在大功率场合下的谐波抑制和无功补偿。通过研究主电路拓扑结构,给出了主电路设计方法,包括触发电路的设计,IPM驱动电路的设计和同步信号电路的设计。综合运用瞬时无功理论中的p-q法和ip—iq法,提出了一种新的基于瞬时无功理论的有效的三相四线制谐波检测新方法,此方法能将三相电流中的零序电流剔除。最后文章利用Matlab／Simulink构建了仿真模型,设定了仿真模型中各部分的参数,仿真结果验证了该方法的准确性和有效性。     

Power-line impedance and the origin of the low-frequencyoscillatory transients

The three main issues discussed are the origin and characterization of flow-frequency transients, the determination of the impedance of power systems by deliberate switching of capacitors, and suggestions for remedies against these transients. The origin of low-frequency oscillatory transients is attributed to the connection of large capacitances across live wires of the distribution systems. Measurements based on the connection of capacitors of known capacitance across the line are demonstrated to be a natural, accurate, and reproducible means of probing the power-line impedance. This turns out to be constituted by resistance and inductance in the frequency range explored. A physically significant equivalent circuit can be derived, based on the consideration that the three-wire distribution system (phase, neutral, safety wire) consists of three mutually coupled loops. The measurement technique (V-terminal data) permits derivation of both common-mode and differential-mode components. Several conclusions are drawn on the basis of the results of the time-domain transient analysis. Essential quantities of the phenomenon (peak voltage, duration, spectral content) are derived, and corrective measures are suggested     

Copper-based hybrid fabrication of a 50 W, 5 MHz 40 V-5 V DC/DCconverter

A prototype 50 W, 40 V to 5 V DC/DC converter operating at 5 MHz and constructed with chip and wire hybrid techniques on a ceramic substrate with copper thick-film conductors is presented. A brief discussion of the thick-film process is given to point out the special issues concerning copper-based conductor systems. Some of the specific trade-offs that arise with regard to the construction of a power circuit with hybrid techniques are discussed. A method by which transformers may be fabricated to have very little leakage inductance, both internally and in their connection to rectifiers, is then described. The performance of a power circuit, the dual resonant forward converter is presented     

An overview of electrical characterization techniques and theory for IC packages and interconnects

This paper reviews current approaches to the electrical characterization and modeling of IC packages and interconnects. An overview of both frequency and time-domain measurement methods and summaries of equivalent circuit model selection and extraction methodologies are included. Additionally, an overview of numerical methods for electromagnetic modeling is included for completeness. Finally, relevant case studies from the literature are summarized to further supplement the discussed techniques. The focus is primarily on high-frequency signal related characterization and power integrity issues are not directly considered in this paper. This paper is presented in the context of the growing requirement for package and interconnection electrical models for high-speed and miniaturized systems.     

A Review of the State of the Art of Power Electronics for Wind Turbines

This paper reviews the power electronic applications for wind energy systems. Various wind turbine systems with different generators and power electronic converters are described, and different technical features are compared. The electrical topologies of wind farms with different wind turbines are summarized and the possible uses of power electronic converters with wind farms are shown. Finally, the possible methods of using the power electronic technology for improving wind turbine performance in power systems to meet the main grid connection requirements are discussed.      

Tiny-scale “stealth” current sensor to probe power semiconductor device failure

“Stealth” electric current probing technique for power electronics circuits, power device modules and chips makes it possible to measure electric current without any change or disassembling the circuit and the chip connection for the measurement. The technique consists of a tiny-scale magnetic-field coil, a high speed analog amplifier and a digitizer with numerical data processing. This technique can be applied to a single bonding wire current measurement inside IGBT modules, chip scale current redistribution measurement and current measurement for surface mount devices. The “stealth” current measurement can be utilized in the failure mechanism understanding of power devices including IGBT short circuit destruction.     

Reliability based hardware Trojan design using physics-based electromigration models

In recent years the concern over Hardware Trojans has come to the forefront of hardware security research as these types of attacks pose a real and dangerous threat to both commercial and mission-critical systems. One interesting threat model utilizes semiconductor physics, specifically aging effects such as Electromigration (EM). However, existing methods for EM-based Trojans rely on empirical Black's models can easily lead to performance degradation and less accuracy in Trojan activation time prediction. In this article, we study the EM-based Trojan attacks based on recently developed physics-based EM models. We propose novel EM attack techniques in which the EM-induced hydrostatic stress increase in a wire is caused by wire structure or layer changes without changing the current density of the wires. The proposed techniques consist of sink/reservoir insertion or sizing and layer switching techniques based on the early and late failure modes of EM wear-out effects. As a result, the proposed techniques can have minimal impact on circuit performance, which is in contrast with existing current-density-based EM attacks. The proposed techniques can serve as a trigger for the EM attack on power/ground networks and signal and clock networks. Furthermore, we also present two potential EM attack mitigation techniques, namely, the split fabrication and burn-in testing.     

射频/微波能量收集系统的整流电路研究进展

射频/微波能量收集系统以可持续、环保等优点在无线传感器网络、可穿戴设备等领域具有广泛应用前景。对近年来射频/微波能量收集系统的整流电路的研究进展进行了概述。分析并讨论了整流电路的技术指标和电路结构,分别从器件研究和电路设计两个方面对整流电路的研究进展进行分析、归纳。从原理、性能提升等方面分析具有低的零偏压电阻值的自旋二极管应用于微瓦量级信号整流电路的潜力;从微弱信号整流、宽输入功率范围信号整流、高功率转换效率整流、阻抗去敏感化4个方面分析了整流电路设计的关键问题,归纳出有效的解决途径并对整流电路的发展趋势进行了展望。     

Terminal-to-Terminal Hybrid Full-Wave Simulation of Low-Profile, Electrically-Small, Near-Ground Antennas

An investigation into the simulation and performance of low-profile, electrically-small antennas for unattended ground sensor (UGS) networks is featured in this study. Because UGS transceivers are intended for operation near the ground, ground proximity effects become extremely important for considerations related to antenna efficiency, input matching, radiation pattern, and the overall path loss between the transmitter and receiver nodes. While vertical wire antennas are shown to be less susceptible to path loss, a low-profile alternative is desired for UGS applications and is often required in the fabrication of low-cost, monolithic on-chip, miniaturized systems. In this work, the performances of different transceiver systems utilizing different types of near-ground antenna structures including the dipole, loop, ordinary circular slot, and cavity-backed circular slot are analyzed using a full-wave hybrid approach consisting of the moment method in conjunction with a near-ground asymptotic field propagation model. The figure of merit for comparison among the various configurations is identified as the efficiency factor calculated from the ratio of the input power at the transmitting antenna terminal to the received power at the receiving antenna terminal. The unique features of ground proximity effects as pertaining to near-ground operation are discussed and an optimal radiator is identified from the set of structures analyzed.     

功率电路电流检测方法及其应用

在功率电路设计中，经常涉及电流检测的问题。结合不同电路的设计特点，介绍了三种常用电流检测方法、检测传感器的物理实现及相关电路设计的特点，并对不同检测方法的优缺点进行了比较。