Reduction in Ripple Current and Self‐Inductance by Using Electromagnetic Coupling of Reactor

To produce DC current by using a multiphase reversible chopper, smoothing reactors are needed. When smoothing reactors are employed, the chopper device becomes large and heavy, especially if electromagnetic interference is avoided. The reduction in the ripple current by electromagnetic coupling contributes to making the chopper device smaller and lighter. We deduced the relationships among the ripple current amplitude, duty factor, and electromagnetic coupling coefficient. To determine the loss and gain, we introduced the ratio of the amplitude of the ripple current in each phase and in the total combined current of the multiphase chopper system to that of the ripple current in a one‐phase chopper, A_ph, A_sum, respectively. This value indicates the reduction not only in the ripple current amplitude but also in the self‐inductance. The minimum value of the above‐mentioned ratio obtained analytically is accurately determined. We derived the minimum values and obtained the range within which reduction of the ripple current amplitude for both each phase and total combined is achieved. Finally, we applied an optimal electromagnetic coupling coefficient to the design of on‐board reactors of electric railway vehicles. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(2): 68–82, 2014; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22480     

Method for Diffusing Carrier Noise under Zero‐Speed Condition using a Zero‐Sequence Voltage

In this paper, a technique is proposed to reduce the carrier noise of pulse width modulation (PWM) inverters for a permanent magnet motor drive. The carrier noise is generated by the motor and the reactor driven by the inverter and affected by the switching frequency. When a motor rotates and drives a machine, the carrier noise is hidden by the machine noise. However, when the motor speed is approximately zero, the carrier noise becomes dominant and raucous. The typical method to reduce the noise employs a switching frequency higher than the audible frequency of human hearing. However, the increase in switching frequency results in the inverter suffering a higher switching loss and lower efficiency. In particular, when the permanent magnet motor operates at approximately zero‐speed and full‐load, for example, in the hill‐start conditions of electric vehicles and the start and stop conditions of elevators, the current flows in specific power devices and the switching loss further increases. The proposed technique uses a zero‐sequence voltage, which is generated randomly with the M‐sequence signal, and diffuses the frequency components of the ripple contained in the current. The technique is able to reduce the noise without increasing the switching frequency of the inverter when the motor speed is almost zero. Simulation and experimental results show that the proposed technique can diffuse the carrier noise and the cycle of the M‐sequence signal changes the diffusion effect of the carrier noise.     

Comparison Between Phase Number and Operation Mode of Multiphase Boost Chopper for Reducing Input Current Ripple

This paper describes the characteristics of a multiphase boost chopper on the basis of the difference between its phase number and operation mode. First, the paper presents a theoretical analysis of an input current ripple in a multiphase boost chopper controlled with CCM and DCM. For analyzing CCM, the input current ripple in an n‐phase boost chopper is expressed by a general formula using a duty ratio. This expression clarifies integrally the relations between the phase number and input current ripple. The current ripple in CCM is much lower than that in DCM for the tested four‐phase boost chopper. Furthermore, this paper presents a comparison between the converter efficiency and step response of a four‐phase boost chopper controlled in CCM or DCM. The efficiency in CCM is higher than that in DCM by 0.5%. The phase number affects the step response characteristics in CCM. However, it does not affect the step response characteristics in DCM. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 185(1): 57–66, 2013; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22398     

干式半心电抗器合闸涌流的计算

提出了用时步有限元法来模拟干式半心电抗器合闸涌流的动态过程。给出了将非线性时变电磁场有限元方程与电压源激励的电路微分方程相结合的三维场路耦合电磁计算模型。对两个实例进行了计算,证明了方法的正确性和有效性,并对干式半心电抗器合闸涌流特性进行了分析和讨论。     

单相可控电抗器的一种谐波抑制原理及实现

新型单相可控电抗器近年来在电气化铁路动态无功补偿、自动调谐消弧线圈等方面得到了应用。减小单相应用条件下可控饱和类电抗器产生的谐波颇为困难，通常采用LC并联滤波装置，但效果不甚理想。该文提出单相应用条件下，可控电抗器的一种谐波抑帛方法，该方法将两组工作于不同电磁参数的单相可控电抗器并联，通过实施协调控制，可使每个并联单元（可控电抗器）所产生的谐波相经补偿，从而单相并联电抗器组的谐波水平大大降低。理论分析和实验结果证明了上述方法的有效性和可行性。     

混合直流系统中基于平波电抗器与限流电抗器参数优化的限流策略

直流线路正常运行过程中,平波电抗器可以减小电流纹波。当直流线路发生故障时,限流电抗器的快速投入可以抑制故障电流的上升速度。因此,考虑限流电抗器与平波电抗器的协同,不仅可以抑制故障电流的上升速度,而且能够降低直流断路器的切断容量。然而,受到投资成本和系统动态特性的制约,平波电抗器与限流电抗器的电感容量需要保持在合理的范围内。因此,对直流输电系统中平波电抗器和限流电抗器的容量进行优化配置,在保证限流能力的同时降低投资是十分有意义的。首先,建立了交直流混联系统的故障等效模型,并分析直流线路发生双极性短路时两端故障电流的特性。其次,建立了平波电抗器和限流电抗器的优化配置数学模型。最后,基于MATLAB仿真试验对所提限流策略进行了验证。     

三电平悬浮斩波器性能研究

采用两电平控制技术的磁浮列车悬浮斩波器由于较大的输出纹波电流引起的悬浮力波动,影响了悬浮控制的精度和稳定性.提出了一种采用三电平控制的悬浮斩波器,分析了其主电路和工作原理,针对输出电流纹波、响应速度、输入电源电压对输出电流的影响等3方面进行了对比仿真分析,并给出了试验验证结果.     

基于多物理场耦合的特高压并联电抗器振动噪声仿真分析与实验研究

为全面研究特高压并联电抗器振动噪声特性及预测大小,考虑电抗器振动噪声产生机理,建立了基于多物理场耦合的电磁-结构-噪声全过程仿真电抗器模型。基于场-路耦合的电磁学理论,采用虚位移原理计算了电抗器电磁力;基于电磁-结构耦合的动力学理论,以电磁力为载荷,求取电抗器振动特性与振动速度;基于结构-噪声耦合的声学理论,以电抗器振动速度为载荷,分析了电抗器噪声分布;通过实验验证了模型的准确性。研究结果表明:油箱表面振动信号可反映电抗器内部运行状态,送电瞬间电抗器从暂态过渡到稳态需1.5个电流周期,电抗器振动以100 Hz为主振频率,噪声集中于100 Hz为中心频率的1/3倍频带,最大噪声为83.2 dB。分析研究结果为电抗器的减振降噪提供了理论支持。     

一种新型软开关有源电力滤波器研制

为了有效地抑制各种电力电子装置所造成的谐波污染和补偿无功功率，并尽量减小外加补偿系统的损耗，提出了一种新型软开关三相有源滤波器的设计思想。具体方法是在每相桥臂上下2个功率开关管之间串接1个耦合电感。为了提供零电流的关断条件，先将同一相的另一管子导通，使原来导通管子两端承受反向电压而使电流为零。利用该方法，不仅能有效地抑制各次谐波的产生，而且在使用以IGBT为开关管的大功率有源滤波装置中，能完全消除IGBT关断时电流拖尾的缺点，减小了开关功率损耗，提高了系统效率。     

A novel six-phase inverter system with 60-step output voltages forhigh-power motor drives

A novel six-phase voltage-fed inverter system is proposed. The system consists of two main three-phase inverters, coupling reactors, and an additional single-phase inverter. The ripple voltage injected into the DC link by the additional inverter results in 60-step load voltages with the help of the coupling reactors. The main inverters operate at the same frequency as the output, and the additional inverter operates at a frequency six times higher. The advantages and disadvantages of the system are quantitatively discussed     

±800kV干式平波电抗器的国产化制造

介绍了国内干式电抗器企业的技术发展及其技术开发上的重大突破,干式平波电抗器以其对地绝缘简单、无油化、功率倒送不会产生临界电介质应力、运行维护费用低、重量轻等特点广泛应用于电力系统中。提出了±800kV干式平波电抗器的开发应从电场分布、电流分布和波分布等方面进行设计的观点。实例说明国内电抗器生产企业有能力通过自主开发设计来满足特高压直流工程的要求。     

EMS型磁浮列车悬浮斩波器输入电流波动分析

悬浮斩波器是EMS型磁浮列车上的开关型电流放大器,由此造成输入电源的电流纹波较大。对双正激斩波器和三电平悬浮斩波器的输入电流波动方程进行了推导,对比发现,在相同输出电流条件下,三电平悬浮斩波器的输入电流波动更小。基于PspiceAD平台建立了悬浮斩波器模型,仿真研究验证了分析结论。最后,对自主研制的悬浮斩波器样机进行了实验对比测试。     

采用BUCK电路的低电感无刷直流电动机转矩脉动与损耗分析

通过分析低电枢电感无刷直流电动机的特点,在无刷直流电动机驱动器逆变电路前级采用BUCK变换电路实现电压的调整,在逆变电路中采用Hall信号换相而不叠加PWM斩波信号。通过建立无刷直流电动机及其驱动电路的模型,并对其进行仿真分析,结果表明采用BUCK变换电路后能够减小电机的相电流和母线电流的脉动,减小电磁转矩脉动,消除直流端反向电流,电机铁损耗和铜损耗也大大降低。     

Newly Developed Thyristor Chopper Equipment for Electric Railcars

In the chopper control system for electric railcars, it is effective to adopt high operational frequency of the chopper for achievement of the following: 1) decrease of higher harmonic current induced in the trolley wire, 2) reduction of weight for reactors and capacitors in the traction circuit, and 3) improvement of control response. Through development of reverse-conducting thyristors with very short turn-off time and a repulsion type two-phase chopper, we finally realized production of a new standard high-frequency chopper equipment with regenerative braking for 1500-V dc railcars. Technical achievements mentioned previously were completely realized as a result of adoption of high frequency, 660 Hz, in the equipment. The newly developed standard high-frequency chopper equipment for 30 cars were delivered to the Chiyoda Line of Teito Rapid Transit Authority in Tokyo, and they have been operated satisfactorily in revenue service since March 1971. This paper also describes: 1) the chopper circuit using fast-switching reverse-conducting thyristors and series saturable reactors, 2) analysis of commutation circuit and methods of suppressing reapplied forward voltage increasing rate (dv/dt) and shortening commutation period, 3) the composition of the traction circuit including the protection system, such as protection for overvoltage at the regenerative braking, and 4) test results on the Chiyoda Line of Teito Rapid Transit Authority.     

用于开关磁阻电机驱动系统的新型单电阻电流采样技术

为进一步降低开关磁阻电动自行车设计成本,提出了单电阻电流采样的四相电流重构技术。对单电阻电流采样的四相电流重构技术的原理进行研究,建立了不同开关状态下四相电流与采样电流的关系。对换相而引起的非换相相电流波动问题进行分析,定义了无法重构相电流的区域为非观测区。提出使用单脉冲注入控制解决非观测区内无法重构相电流的方法,通过在非观测区注入单个脉冲信号,依据直流母线电压值重构得到相电流,并根据给定电流参考量,计算得到脉宽调制补偿信号的占空比,从而实现在非观测区的斩波控制。建立了Matlab/Simulink数字仿真模型,并进行仿真验证,最后进行了开关磁阻电机单电阻电流采样及控制算法的实验。结果表明,所提单电阻电流采样技术具备可行性和使用价值。     

Analysis and implementation of a high‐efficiency zero‐voltage‐zero‐current‐switching DC–DC converter

A high‐efficiency zero‐voltage‐zero‐current‐switching DC–DC converter with ripple‐free input current is presented. In the presented converter, the ripple‐free boost cell provides ripple‐free input current and zero‐voltage switching of power switches. The resonant flyback cell provides zero‐voltage switching of power switches and zero‐current switching of the output diode. Also, it has a simple output stage. The proposed converter achieves high efficiency because of the reduction of the switching losses of the power switches and the output diode. Detailed analysis and design of the proposed converter are carried out. A prototype of the proposed converter is developed and its experimental results are presented for validation. Copyright © 2011 John Wiley & Sons, Ltd.     

Frequency and Current Ripple of DC to DC Power Converters with Respect to Different Modulation Techniques

In connection with dc choppers, different modulation techniques are used. The chopper may be of a transistor bridge type or of any thyristor type. The output current and voltage can be controlled by pulsewidth modulation, pulse-frequency modulation, or two-level control of the load current. The steady-state behavior of the different modulation techniques is shown in comparable equations and diagrams. Also shown are the ranges of the parameters in which it is possible to use the approximate equations for the chopper frequency and the output current ripple.     

基于自适应FIR算法的交流伺服系统前馈控制

永磁同步电机(PMSM)交流伺服控制系统中由于电子器件的开关引起相电流非正弦变化,经坐标变换得到的交直轴电流含有谐波成分,引起电流环振荡及电磁转矩脉动。在分析相电流与交直轴电流高次谐波关系,以及交直轴电流高次谐波对电磁转矩影响的基础上,提出了一种基于自适应FIR滤波器的交流伺服系统前馈控制策略,并在该方法的基础上提出了变步长因子算法,根据误差值改变步长因子,在提高滤波器收敛速度的同时减小超调。该算法与传统的一阶低通滤波器相比,相位不滞后,灵敏度更高,且系统稳定。改进后的控制策略有效地降低交直轴电流谐波,抑制电流环振荡及电磁转矩脉动,提高PMSM交流伺服控制系统稳定性及动态响应。通过仿真与试验证明了该方法的可行性。     

交错并联双向DC/DC变换器Buck模式下的耦合电感设计规则

针对目前交错并联双向DC/DC变换器中耦合电感设计规范不全面这一问题,以三相交错并联双向DC/DC变换器为例,在Buck模式下占空比在1/3~2/3范围内,研究变换器采用分立电感和耦合电感,对稳态电流纹波及暂态电流的响应速度的影响。通过对比,证明采用耦合电感具有减小稳态相电流纹波或者增大暂态总输出电流响应速度的作用,且占空比越接近1/3和2/3,耦合越强,效果越明显。给出一个耦合电感的设计规则,在这一规则下选择电感的耦合系数,既能减小变换器的稳态相电流纹波,又能提高暂态总输出电流响应速度。最后,通过实验证明了耦合电感具有提高暂态总输出电流响应速度和减小稳态相电流纹波的作用,从而证明了设计规范的正确性。