Number-Phase Quantization Scheme for L-C Circuit

For a mesoscopic L-C circuit,besides the Louisell's quantization scheme in which electric charge q andelectric current I are respectively quantized as the coordinate operator Q and momentum operator P,in this paperwe propose a new quantization scheme in the context of number-phase quantization through the standard Lagrangianformalism.The comparison between this number-phase quantization with the Josephson junction's Cooper pair number-phase-difference quantization scheme is made.

Number-phase quantization of a mesoscopic RLC circuit

With the help of the time-dependent Lagrangian for a damped harmonic oscillator, the quantization of mesoscopic RLC circuit in the context of a number-phase quantization scheme is realized and the corresponding Hamiltonian operator is obtained. Then the evolution of the charge number and phase difference across the capacity are obtained. It is shown that the number-phase analysis is useful to tackle the quantization of some mesoscopic circuits and dynamical equations of the corresponding operators.

Real-Time Method for Detecting Harmonic and Reactive Currents of Single-Phase Circuits

According to the characteristics of single-phase circuits and demand of using active filter for real-time detecting harmonic and reactive currents, a detecting method based on Fryze＇s power definition is proposed. The results of theoretical analysis and simula- tion show that the proposed method is effective in realtime detecting of instantaneous harmonic and reactive currents in single-phase circuits. When only detecting the total reactive currents, this method does not need a phase-locked loop circuit, and it also can be used in some special applications to provide different compensations on the ground of different requirements of electric network. Compared with the other methods based on the theory of instantaneous reactive power, this method is simple and easy to realize.

Analysis on the fault characteristics of three-phase short-circuit for half-wavelength AC transmission lines

Half-wavelength AC transmission(HWACT) is an ultra-long distance AC transmission technology, whose electrical distance is close to half-wavelength at the system power frequency. It is very important for the construction and operation of HWACT to analyze its fault features and corresponding protection technology. In this paper, the steady-state voltage and current characteristics of the bus bar and fault point and the steady-state overvoltage distribution along the line will be analyzed when a three-phase symmetrical short-circuit fault occurs on an HWACT line. On this basis, the threephase fault characteristics for longer transmission lines are also studied.

Method for Analog Circuit Soft-Fault Diagnosis and Parameter Identification Based on Indictor of Phase Deviation and Spectral Radius

The soft fault induced by parameter variation is one of the most challenging problems in the domain of fault diagnosis for analog circuits.A new fault location and parameter prediction approach for soft-faults diagnosis in analog circuits is presented in this paper.The proposed method extracts the original signals from the output terminals of the circuits under test（CUT） by a data acquisition board.Firstly,the phase deviation value between fault-free and faulty conditions is obtained by fitting the sampling sequence with a sine curve.Secondly,the sampling sequence is organized into a square matrix and the spectral radius of this matrix is obtained.Thirdly,the smallest error of the spectral radius and the corresponding component value are obtained through comparing the spectral radius and phase deviation value with the trend curves of them,respectively,which are calculated from the simulation data.Finally,the fault location is completed by using the smallest error,and the corresponding component value is the parameter identification result.Both simulated and experimental results show the effectiveness of the proposed approach.It is particularly suitable for the fault location and parameter identification for analog integrated circuits.

Phase-controlled coherent population trapping in superconducting quantum circuits

We investigate the influences of the-applied-field phases and amplitudes on the coherent population trapping behavior in superconducting quantum circuits. Based on the interactions of the microwave fields with a single A-type three-level fluxonium qubit, the coherent population trapping could be obtainable and it is very sensitive to the relative phase and amplitudes of the applied fields. When the relative phase is tuned to 0 or π, the maximal atomic coherence is present and coherent population trapping occurs. While for the choice of π/2, the atomic coherence becomes weak. Meanwhile, for the fixed relative phase π/2, the value of coherence would decrease with the increase of Rabi frequency of the external field coupled with two lower levels. The responsible physical mechanism is quantum interference induced by the control fields, which is indicated in the dressed-state representation. The microwave coherent phenomenon is present in our scheme, which will have potential applications in optical communication and nonlinear optics in solid-state devices.

A Subthreshold Low-Voltage Low-Phase-Noise CMOS LC-VCO with Resistive Biasing

This paper presents a low-phase-noise LC voltage-controlled oscillator (LC-VCO) with top resistive biasing in subthreshold region. The subthreshold LC-VCO has low-power and low-phase-noise due to its high transconductance efficiency and low gate bias condition. The top resistive biasing has more benefit with the feature of phase noise than MOS current source since it can support the low-noise characteristics and large output swing. The LC-VCO designed in 130-nm CMOS process with 0.7-V supply voltage achieves phase noise of -116 dBc/Hz at 200 kHz offset with tuning range of 398 MHz to 408 MHz covering medical implant communication service (MICS) band.

Observation of geometric phase in a dispersively coupled resonator-qutrit system

We present an experiment of observing the geometric phase in a superconducting circuit where the resonator and the qutrit energy levels are dispersively coupled. The drive applied to the resonator displaces its state components associated with the qutrit＇s ground state and first-excited state along different circular trajectories in phase space. We identify the resonator＇s phase-space trajectories by Wigner tomography using an ancilla qubit, following which we observe the difference between the geometric phases associated with these trajectories using Ramsey interferometry. This geometric phase is further used to construct the single-qubit It-phase gate with a process fidelity of 0.851± 0.001.

A monolithic distributed phase shifter based on right-handed nonlinear transmission lines at 30 GHz

The epitaxial material, device structure, and corresponding equivalent large signal circuit model of GaAs planar Schottky varactor diode are successfully developed to design and fabricate a monolithic phase shifter, which is based on right-handed nonlinear transmission lines and consists of a coplanar waveguide transmission line and periodically distributed GaAs planar Schottky varactor diode. The distributed-Schottky transmission-line-type phase shifter at a bias voltage greater than 1.5 V presents a continuous 0°–360° differential phase shift over a frequency range from 0 to 33 GHz. It is demonstrated that the minimum insertion loss is about 0.5 dB and that the return loss is less than-10 dB over the frequency band of 0–33 GHz at a reverse bias voltage less than 4.5 V. These excellent characteristics, such as broad differential phase shift, low insertion loss, and return loss, indicate that the proposed phase shifter can entirely be integrated into a phased array radar circuit.

基于新能源发电改进型移相全桥变换器研究

新能源发电中需要广泛使用移相全桥变换器,以实现软开关技术从而减小系统的开关损耗。而传统移相全桥直流变换器滞后臂在轻载时难以实现ZVS,导致系统大功率输出时效率降低以及系统换路时容易产生尖峰电压、电流等现象,针对这一问题,提出了一种改进的有源软开关移相全桥DC-DC变换器拓扑。系统首先提出了改进变换器的拓扑结构,在此基础上对其工作模态进行了研究分析,并合理优化相关器件的选型,最后通过系统仿真及试验平台进行了系统仿真和试验测试,结果表明,所设计的加入辅助电路改进型移相全桥直流变换器在轻载情况下,能够使变换器滞后臂达到软开关效果,同时,在大功率输出情况下,对器件发热、电压波形振荡均有较好的抑制作用,系统整体效率变高,同时可靠性、稳定性变强。

Fractional-order L_βC_a filter circuit network

In this paper we introduce the new fundamentals of the conventional LC filter circuit network in the fractional domain.First, we derive the general formulae of the impedances for the conventional and fractional-order filter circuit network.Based on this, the impedance characteristics and phase characteristics with respect to the system variables of the filter circuit network are studied in detail, which shows the greater flexibility of the fractional-order filter circuit network in design.Moreover, from the point of view of the filtering property, we systematically study the effects of the filter units and fractional orders on the amplitude–frequency characteristics and phase–frequency characteristics. In addition, numerical tables of the cut-off frequency are presented. Finally, two typical examples are presented to promote the industrial applications of the fractional-order filter circuit network. Numerical simulations are presented to verify the theoretical results introduced in this paper.

Self-Balanced Charge Pump with Fast Lock Circuit

A self-balanced charge pump （CP） with fast lock circuit to achieve nearly zero phase error is proposed and analyzed. The proposed CP is designed based on the SMIC 0.25μm 1P5M complementary metal oxide semiconductor （CMOS） process with a 2.5 V supply voltage, HSPICE simulation shows that even if the mismatch of phase/frequency detector （PFD） was beyond 10%, the charge pump could still keep nearly zero phase error, Incorporated fast lock circuit can shorten start-up time to below 300 ns.

基于MATLAB_App Designer电力电子虚拟仿真实验系统设计

根据MATLAB_App Designer提供的界面布局功能,运用MATLAB_Simulink搭建电力电子仿真模型,设计了一套人机交互式电力电子技术仿真实验系统。该系统包含典型的电力电子仿真模型和实例,可以帮助学生和工程技术人员学习电力电子电路的工作原理,分析和研究参数设置对电路电压、电流等波形的影响,有利于提高学习者对电力电子技术的研究和设计能力。

不同稳态工况对同步调相机单相短路后暂态温升的影响

同步调相机可在系统故障时为特高压直流换流站提供暂态无功支持,以保持系统电压稳定,防止直流换相失败,但调相机的高无功输出也会导致其温升增加,运行能力受限。系统故障前同步调相机的初始工况是影响其暂态温升和运行能力的一个重要因素,为研究系统低电压时调相机暂态温升与初始工况之间的关系,该文将调相机的电磁场、温度场与电网模型耦合,计算调相机不同稳态工况下的定转子损耗和温度分布;以线路单相短路故障引起的系统低电压为例,研究调相机初始工况对暂态温升的影响。在考虑各结构件最大容许温度的条件下,揭示调相机单相短路持续时间随初始工况的变化规律。研究结果为提升调相机在系统低电压下的暂态运行能力提供技术支持。

A Novel Fault Location Algorithmfor Double-Circuit Transmission Lines based on Distributed Parameter

Anewfault location algorithmfor double-circuit transmissionlines is described inthis paper.Theproposed method uses data extractedfromtwo ends of the transmissionlines andthus eliminates the effects ofthe source impedance andthe fault resistance.The distributed parameter model and the modal transformationare also employed.Depending on modal transformation,the coupled equations of the lines are converted intodecoupled ones.Inthis way,the mutual coupling effects between adjacent circuits of the lines are eliminatedandtherefore an accurate fault location can be achieved.The proposed methodis tested via digital simulationusing EMTP in conjunction with MATLAB.The test results corroborate the high accuracy of the proposedmethod.

面向残差评价的中点钳位型逆变器开路故障诊断方法

在基于解析模型的故障诊断系统中,为了显化残差信号所包含故障信息的能力,提出一种面向残差评价的中点钳位型三电平三相逆变器快速开路故障诊断方法。首先,构建诊断观测器获取三相电流观测值并通过观测矩阵计算电流残差;其次,通过引入基于范数的标准评价函数,计算残差性能指标与阈值,将残差转换为可用的特征信号并与阈值相比较实现高效实时的故障检测;再次,推导不同功率开关器件开路故障状态下的电流残差特性,并依据此特性实现精准的故障隔离;最后,在仿真平台及半实物实验平台上验证了该文所提算法的有效性与可行性。仿真与实验平台结果表明,相较于传统基于信号与知识的诊断方法,残差性能评价的引入使得诊断速度提高80%以上。针对NPC型三电平三相逆变器常见的四种开路故障情况,均可实现快速且精准的故障检测及定位。

无刷励磁机旋转整流器二极管开路故障的轴电压特征研究

内转子式三相无刷励磁机旋转整流器二极管单管开路故障发生频率较高且不易直接监测,可能诱发多个二极管故障的连锁效应,严重影响发电机组的安全可靠运行,根据故障在轴电压中形成的特征谐波进行在线监测是一种新型检测方法。首先分析了旋转整流器二极管单管开路故障时励磁机电枢磁动势特征,利用气隙磁导法得到交链电枢转轴交变磁通表达式,进而预测二极管开路故障后,励磁机轴电压中将出现Pωr/2π整数倍频率的谐波。最后以一台5.8 MW的三相无刷励磁机为例进行有限元仿真,结果与理论预期相符,证明了轴电压信号可用于内转子式无刷励磁机的旋转整流桥二极管开路故障在线监测。

基于输出电压轨迹的三相逆变器开关管开路故障诊断

开关管开路故障会让功率变换器的输出电压与电流产生严重畸变,因而降低了变换器输出的电能质量。开路故障出现后其余功率开关器件的损耗可能增加,所以容易在电路中引发二次故障。文中提出一种针对三相逆变器开关管开路故障的故障诊断方法。故障类型与故障器件的辨识通过分析三相逆变器在αβ平面上的输出电压轨迹实现,仅需要测量滤波后的输出线电压。所提出的方法易于实现,可以诊断三相逆变器的所有开关管开路故障情况。最后,通过仿真和实验验证所提出方法的可行性和准确性。

基于延边三角形接法的24脉波移相变压器设计与电磁特性分析

针对核心设备24脉波移相变压器,从移相原理出发进行设计,并建立场路耦合模型对电磁设计和绕组短路力进行核算,其中关键设计参数移相角与理论值最大偏差仅为0.53%。在此基础上加工实验样机进行实验,移相角度偏差最大仅为0.2°。综合仿真与实验结果,24脉波移相变压器设计有效,且场路耦合模型适用于多脉波移相变压器的电磁仿真。

一种基于锁相放大的谐振式密度传感器谐振频率测量系统设计

谐振式密度传感器测量密度的关键在于谐振频率的测量。现有的测频法、测周期法、FFT法等谐振频率测量方法因噪声、脉冲误差等因素限制了其精度。为了解决该问题,设计了一种以锁相放大器为核心的谐振频率测量系统,其检测电路将交流振动信号的测量转换为直流恒定电压的测量。利用实验中发现的谐振区域内该直流电压与激励频率呈近似线性关系,基于扫频思想提出并实现了一种谐振频率自动测量算法。在(20±0.05)℃环境下进行了密度标定实验,对密度传感器进行了温度补偿。实验结果表明,在密度为700 kg/m^(3)~1000 kg/m^(3)的测量范围内,测得谐振频率稳定性可达到0.002%,传感器的密度测量最大误差为0.48 kg/m^(3),最大综合测量误差为0.069%,验证了所提谐振频率测量方法的有效性、精确性。