变频器功率单元结构改变对电磁兼容性能的影响

通过对多电平单元串联电压源型变频器的功率滩元进行EMC测试，并根据测试的数据提出改进的要求。分析影响电磁兼容性能的结构与要点，预研出通过高等级的电快速瞬变脉冲群测试的基本型式，结合具体的功率单元结构进行更改，提高功率单元的EMC性能指标。在结构更改完成后，功率单元的电快速瞬变脉冲群的通过指标由3．0kV、5kHz、300s提高到4．0kV、2．5kHz、300s，达到严酷工业环境的指标。功率单元结构更改后，其大小和安装方式未变，所以变频器的功率柜内的结构体与功率单元托架无需改变，吲时功率单元内部的主回路的复杂刚性电气连接件均未改变，只是对外壳结构体进行改动就完成了预定的目标。     

变频器功率单元采用电磁兼容原则的新结构研发

系统法是解决电磁兼容性的先进方法，它集中了电磁兼容方面的研究成果，根据电磁兼容要求进行最佳工程设计的方法。多电平单元串联电压源型变频器的功率单元新结构研发中，充分应用系统法，从设计开始就预测和分析电磁兼容性，并在设计、制造、组装和实验过程中不断对其电磁兼容性进行预测和分析，使在正式产品完成之前解决90％的电磁兼容问题。在新单元研发完成后，对其进行电磁兼容性能测试，一次性通过了电快速瞬变脉冲群、静电放电、电磁发射抗干扰度的严酷工业环境等级抗干扰测试。     

多电平单元串联电压源型变频器高压电源瞬时失电连续运行研究

高压变频调速系统现场应用复杂，工艺多样。在重要的大型工业系统中，高压电源系统有双备用，紧急互投等功能，当变频器对大功率的电机供电时，如果高压电源进行切换，将出现0．1S～1．5s左右的失电间隔，要求变频器在失电间隔中能正常工作，且转速波动较小，达到系统在失电期间不出现剧烈振荡。对于多电平单元串联电压源型变频器，当通过对功率单元电容值的加大，PWM输出占空比减小的方法提高失电连续运行性能，其效果均不理想。在经过大量论证后，采用特殊的DSP控制逻辑，并利用旋转系统中的飞轮动能转换，取得实现变频器在高压瞬时失电时保持稳定运行。     

多电平单元串联高压变频器功率单元的热设计

多电平单元串联电压源型高压变频揣的核心——变顿器的通用系统是功率单元，功率单元的热稳定性是高压变频器热发全的核心。在对兆瓦级高压变频器研发中，根据IGBT和DOIDE的参数特性，计算其热损耗功率。结合热分析公式研发变频器功率单元的热沉系统．并利用相关的热分析行业软件，完成300A电流等级的通用功率单元的热设计。     

国产超大功率高压变频器在炼铁高炉鼓风机中的应用

本文结合6500kW/10kV高压变频器实际运行工况,介绍了国产超大功率高压变频器在高炉鼓风机上的应用。通过改造,实现了高炉的工艺优化,也体现了国产基于单元级联式多电平高压变频器的制造能力。     

采用智能化单元的高压变频调速装置

本文简单介绍了单元串联多电平方式高压变频调速装置的两种控制实现途径，提出了智能化功率单元的定义，介绍了智能化单元实现的功能，对集中控制型的装置和智能单元型的装置进行了比较，认为采用智能单元的高压变频调速装置技术更先进，可靠性更高。[编者按]     

一种四单元圆极化微带天线阵的研制

本文设计了一种新颖的四单元圆极化微带天线阵。通过去掉单元贴片周围的介质,使天线阵的重量减少了54%。文中采用电磁仿真软件HFSS10进行优化与仿真,讨论了阵元间距对天线阵的增益、半功率波束宽度、旁瓣电平以及后瓣电平的影响。最后加工制作了相应的微带天线阵,测试结果与仿真吻合较好。     

一种可变电压等级恒功率输出的变流器实现方法

高压大功率变流器已得到广泛应用,但目前,变流器在输出电压降低时输出功率也等比的减少,只能是运用多个变频器来实现恒功率输出。本文介绍了采用IGBT多个功率单元（H桥）串联相结合的多种变换形式,达到恒功率输出多种电压等级的目的。通过组合开关切换实现了1 3.2kV、6.6kV、3.3kV、1.65kV和0～1000V直流的...     

中压（10kV）补偿装置在通信局（站）供配电系统的应用

通过对现有的三电平降压式结构10kV补偿装置及串联链式结构10kV补偿装置的性能、可靠性比较分析，结合国家标准及相关部委发文，系统地剖析10kV补偿装置在通信局（站）选用的原则及具体方案。     

VHF跳频通信系统功率放大器的研制

设计了一种用于跳频通信系统的射频功率放大器。该放大器具有较高的线性度,同时又能实现高功率的稳定输出,低功率输出大于0．25W,中功率输出大于4．5W,滤波器衰减损耗小于2dB,谐波抑制大于48dB。介绍了VHF跳频发射机系统。包括逻辑电平转换单元、调制环单元、射频环单元、频率合成器单元和功放单元;着重对射频功率放大器的性能进行了分析,指出了提高功放线性度的特殊方法;给出了射频功率放大器的硬件电路设计过程。最后,对射频功率放大器进行测试,结果表明,其性能指标完全达到系统设计要求,并有所提高,而且具有较强的实用性。     

10kV配网合环转电对继电保护的影响研究

我国普遍使用的配网电压为10 kV,该电压配网存在自身的优势和特点,不仅具有综合性及系统性,同时更具有强大的兼容性。但是10 kV配网也存在很多不足,例如容易受外部因素的干扰,容易产生各类事故,时常会出现电力系统运行不正常的现象。为此,文章全面解析了10 kV配电合环转电的安全使用以及继电保护等环节。不论是电流继电保护装备,还是合环操作都需要加以重视,才能规避安全问题。     

10kV配电线路故障排除及处理措施

10kV配电线路本身属于高压配电设备。在实际运行过程中,受到多种因素的影响,使得配电线路出现了不同程度上的故障与问题。因此,如何将故障及时排除和处理十分重要。本文对10kV配电线路故障以及处理方法进行分析。     

Current state-of-the-art and future prospects for power semiconductor devices in power transmission and distribution applications

Since the first commercially viable thyristors appeared in the early 1960s, there has been a dramatic increase in the switched power ratings and versatility of high-voltage power semiconductor devices. By the mid 1970s, thyristors with switched power ratings of several MVA were being applied in high voltage dc transmission systems and static VAr compensators. The introduction, in the 1980s, of controlled turn-off devices, such as the gate turn-off thyristor (GTO) and insulated gate bipolar transistor (IGBT), broadened the application of high-voltage power devices to hard-switched converters and, by the start of the 21st century, controllable silicon power devices were available with voltage ratings of 12?kV and switched power capabilities of up to 40?MVA. A review of the current state-of-the-art in silicon high-voltage power semiconductor technology covers gate-commutated thyristors (GCT, IGCT) and IGBT devices, including the injection-enhanced IGBT or IEGT. Despite these considerable achievements, there is now mounting evidence that silicon-based power semiconductors are reaching their limit, both in terms of voltage rating and of switched power capability. The introduction of wide-band-gap semiconductor materials such as silicon carbide offers the potential to break through the voltage-switching frequency limitations of silicon, with power-switching frequency products more than two orders of magnitude higher. An analysis of the current status and future prospects for silicon carbide power electronic devices is presented, together with a case study comparing a variety of silicon and silicon carbide solutions in a 10?kV hard-switched converter application. It is shown that an all-silicon carbide switch offers the best electrical performance and lowest cost solution, in spite of higher per unit area device costs.     

风洞实验室自动化控制系统的电磁兼容

介绍了某风洞自动化控制系统中,变频器干扰测控系统的实例分析及干扰处理方法。通过在变频器输入、输出端以及其他控制部分电路中加装匹配的滤波器,及对整个供电系统进行屏蔽和良好接地,有效解决了变频器工作时产生的电磁干扰。     

GPS synchronized power system phase angle measurements

Before a major new 500 kV transmission line was placed in service between Oregon and the San Francisco, California area, a series of high-voltage short circuit tests were performed on the transmission system. The short circuit faults produced a brief ‘delta function’ shock to the regional power system. This paper discusses the use of Global Positioning System (GPS) synchronized equipment for the measurement and analysis of key power system quantities. Before the testing, the authors installed two GPS synchronized phasor measurement units (PMUs). The PMUs use GPS to globally synchronize the measurement of the state vector of the power system, the complex voltages of substation busses. Complex voltage means the magnitude and the relative phase angles of substation voltages. GPS provides the global time reference marker for phase angle measurement. One electrical degree of the 60 Hz waveform equals about 46 μs. Across short transmission lines (less than 50 km), measurements may need to be made to 0.1 electrical degree, which translates to clock synchronizations of roughly 5 μs. The PMUs recorded the dynamic response of the power system phase angles when the northern California power grid was excited by the artificial short circuits. Power system planning engineers perform detailed computer generated simulations of the dynamic response of the power system to naturally occurring short circuits, e.g. faults caused by lightning. The computer simulations use models of transmission lines, transformers, circuit breakers, and other high voltage components. This work will compare computer simulations of the same event with field measurements.     

Computer Simulation of a 5.7GHz, 110kW Transit-Time Oscillator

A high-power transit-time oscillator producing 110kW at 5.7GHz in the TM₀₁₀ cavity mode is described. The device comprises a temperature-limited diode electron gun operating at 40A in the range from 28kV to 35kV and an intermediate coaxial cavity from which the microwave power is extracted through a TEM coaxial guide. The diode serves also as a resonant cavity, where electromagnetic oscillations are grown from noise. The effect of the applied voltage on both the output microwave power and the instability saturation time has been investigated leading to an optimal diode voltage of 33kV.     

带延时功能的微波自动报警系统的设计

设计了一个由微波发射器、555定时器、电压比较器和继电器组成的具有延时功能的自动报警器。该报警器由微波探头检测活动物体,将波动的电磁场信号转化为波动的电压信号后输出给电压比较器,电压比较器比较后的高电平触发555定时器工作,经过延时后的信号触发继电器报警。该报警系统克服了一般报警器容易出现的漏报警现象和其他微波报警器容易受外界电磁场的干扰所引起的误报警的缺点,很好地解决了报警系统的灵敏性与可靠性之间的矛盾。