控制方式对变频调速系统谐波现象影响的研究

随着变频调速技术的发展,谐波污染问题突出,为了节能降耗消除谐波,有必要对变频调速系统中的谐波含量进行研究。     

漠北油田生产中的高次谐波危害分析与解决

在实际应用中,人们往往只注意到变频调速(VVVF)的节能效果,而忽视了由变频器引起的谐波危害。针对漠北油田转油站外输泵变频调速系统中的高次谐波危害,分析了高次谐波产生的原因,通过对电压、电流波形的观测和数据的记录比较,确认了故障是由变频器带来的高次谐波引起,提出了合理的解决方案,成功地消除了谐波危害,确保了漠北油田的安全生产并指出了使用变频调速技术的注意事项,具有较高的工程指导价值。     

交-交变频多相同步电动机调速系统谐波转矩分析

多相同步电动机用作舰船的推进电机有着广泛的应用前景.以十二相同步电动机系统为例,从十二相交-交变频器输出谐波电压入手,分析推导了交-交变频十二相同步电动机调速系统输出谐波转矩的解析计算公式.通过一个具体算例,计算得到了其主要次谐波的频谱,结果表明,其谐波转矩近似为零.理论计算结果得到了仿真和试验的验证,仿真和试验结果均表明,交-交变频十二相同步电动机调速系统转矩谐波情况比三相系统有了很大改善.     

引黄工程平鲁泵站接入系统及干线扩机后谐波分析计算

阐述了随着变频调速技术的日益成熟,变频器驱动交流电动机的变频调速系统已成为交流调速的主流,变频调速系统作为供电网的主要谐波源之一,对其进行谐波分析是必要的。针对万家寨引黄工程平鲁泵站及各干线的变频调速机组进行谐波分析计算,结果表明泵机投运后会对电网造成谐波污染,建议控制变频机组同时投运数量,并且在变频装置中装设滤波器。     

中压变频技术在火电厂中的应用与研究

在分析火电厂主要辅机设备运行现状的基础上，对中压变频调速技术进行研究，通过美国罗宾康公司完美无谐波变频器在某火电厂引风机改造中的应用实例，介绍中压变频调速技术在火电厂主要辅机设备中的调速控制技术。实例证明该变频技术在节能降耗、提高自动控制水平方面具有很好的应用前景。     

两种常见电压源型高压变频器的比较

1.引言 随着电气传动技术,尤其是变频调速技术的发展,作为大容量传动的高压变频调速技术也得到了广泛的应用。近年来,各种高压变频器不断出现,电压源型高压变频器具有运行稳定、调速范围宽、输出波形好、输入电流谐波含量低、功率因数高和效率高等优点,应用较为广泛。本文对三电平PWM变频器和单元串联多电平PWM变频器二种应用较为普遍的电压源型高压变频器进行分析比较,指出各自优缺点。 2.三电平PWM电压源型变频器 在PWM电压源型变频器中,当输出电压较高时,为了避免器件串联引起的动态均压问题,同时降低输出谐波和dv/dt,逆变器部分可以采用三电平方式,也称中心点钳位(Neutral Point Clamped:NPC)方式,如图1。逆变部分功率器     

变频调速系统对牵引电机谐波损耗影响的研究

变频调速系统输出的脉宽调制波含有丰富的谐波,谐波引起附加损耗,使交流牵引电机运行温升增加,导致绝缘加速老化,缩短其运行寿命.文章利用MATLAB软件建立了变频调速仿真系统,对影响变频牵引电机谐波损耗的逆变器参数进行了分析,并提出一种用谐波总损耗因数表征谐波损耗的方法.     

基于脉冲宽度调制技术的变频调速系统研究

介绍了交流变频调速类型、基本原理和脉冲宽度调制技术,分析了基于脉冲宽度调制技术变频调速的优点以及发展趋势,并对其性能进行了探讨,研究了脉冲宽度调制技术变频调速的工作原理和性能表现,论述了其克服谐波严重危害的基本方法。     

基于LabVIEW的油气田变频系统谐波测试与评价

针对目前变频调速拖动系统谐波测试与评价方法不完善、操作成本高等实际问题,建立一种涵盖变频器输入侧、输出侧2大类共9项指标的谐波评价指标体系,明确各项指标的计算方法.同时,提出基于虚拟仪器的变频调速系统谐波测试与分析方法,将LabVIEW软件平台与外置数据采集模块相结合,代替传统测试仪器实现谐波的测试及信号采集、处理与分析.在理论研究基础上,搭建实验平台,进行3种工况的验证实验,结果表明测试方法正确可行,进而开展40种工况的应用实验,结果进一步证明提出的方法简便可靠.基于实验结果数据,进一步分析谐波对变频调速拖动系统性能的影响,并得出相应的影响规律,为后续开展谐波防治等相关工作提供指导依据.     

变频调速异步电机槽配合的探讨

变频调速异步电机中由于时间谐波的存在,其槽配合规则的计算发生了变化。本文在变频调速异步机谐波磙势分析的基础上,从谐波转矩全面讨论计算变频调速异步电机的槽配合规则与普能异步电机的不同之点,为变频调速异步电机的设计提供了参考。     

Design, fabrication, back-to-back test of 14200-hp two-polecylindrical-rotor synchronous motor for ASD application

This paper describes the design aspects, fabrication, and testing of a 14200-hp two-pole cylindrical-rotor synchronous motor used with a load-commutated inverter (LCI) adjustable-speed drive (ASD) to drive a refrigeration compressor for a refinery alkylation plant. The motor design aspects include extensive finite-difference analysis of the rotor cage assembly and laboratory bench testing of a wedge assembly to verify finite-difference analysis results prior to fabrication. Torsional and harmonic analysis results are also presented. Special considerations are discussed regarding rotor heating due to harmonic currents and mitigation methods for handling the harmonic currents and heating. Mechanical design aspects are presented of the rotor cage, including rotor slot design, wedge, and end ring assembly. Two motors and drives were built, for companion projects, allowing for verification of the rotor-cage assembly by a back-to-back (BTB) test. Test preparation, setup and results are presented, including rotor temperature mapping, vibration data and torsional results. Finally, test results are compared with calculated values     

变频调速电动机最佳起动频率选择

分析了PWN控制电压型变频器供电变频调速电动机,在不同的起动频率下起动时,电动机转动转矩和起动电流的变化规律,以及由于高次谐波引起的趋肤效应使定、转子导体电阻阻值显著增加对电动机起动特性的影响,寻找到既满足电动机起动转矩要求,又不超过变频器过载电流的最佳起动频率范围。     

Closed-form analysis of adjustable-speed drive performance under input-voltage unbalance and sag conditions

Voltage unbalance or sag conditions generated by the line excitation can cause the input rectifier stage of an adjustable-speed drive (ASD) to enter single-phase rectifier operation. This degradation of the input power quality can have a significant negative impact on the induction-machine performance characteristics. This paper provides an approximate closed-form analysis of the impact of line-voltage sags and unbalance on the induction-machine phase voltages, currents, and torque pulsations for a general-purpose ASD consisting of a three-phase diode bridge rectifier, a dc link, and a pulsewidth modulation (PWM) inverter delivering constant volts-per-hertz excitation. Attention is focused on the impact of the dominant second harmonic of the line frequency, which appears in the dc link voltage during the sag/unbalance conditions, neglecting the impact of the other higher order harmonics. In addition to the closed-form analytical results that assume constant rotor speed, both simulation and experimental results are presented, which confirm the key analytical results, including the dominance of the second harmonic in the resulting torque pulsations. The analytical results can be used as a valuable design tool to rapidly evaluate the approximate impact of unbalance/sag conditions on ASD machine performance.     

Design considerations for an inverter output filter to mitigate theeffects of long motor leads in ASD applications

Design considerations for an inverter output filter to mitigate the effects of long motor leads in adjustable-speed drive (ASD) applications are presented. It is shown by analysis that, for a given length of cable, reducing the dv/dt of the pulsewidth modulated (PWM) inverter output voltage applied to the cable below a critical value will eliminate overvoltages due to voltage reflections. Design issues for a low-pass filter at the inverter output terminals to reduce the dv/dt of the inverter output pulse are examined in detail. The filter operation is verified for the entire variable frequency range of the inverter. The performance of the filter is evaluated through simulations and experimentally on a 460 V commercially available AC motor drive (PWM insulated gate bipolar transistor (IGBT)). The proposed inverter output filter is then compared with a motor terminal shunt filter also designed to reduce overvoltages and ringing at the motor terminals     

Modeling, Simulation, and Test of a Three-Level Voltage-Source Inverter With Output LC Filter and Direct Torque Control

This paper presents the modeling, detailed simulation, and test of an efficient medium-voltage adjustable-speed drive. The system consists of a three-level neutral-point-clamped inverter supplied by a 12-pulse rectifier. To achieve a motor-friendly supply, an LC filter is inserted between inverter output terminals and induction motor terminals. A direct torque control tunes the inverter. The full power circuits as well as the digital control scheme have been implemented and simulated. Simulation results have been compared successfully with measurements, in steady state and transients     

浅谈变频电机设计时需考虑的一些问题

简要介绍了静止式变压变频器的主要类型和以及之相应的变频电机设计特点。根据交流调速系统的特点及逆变器运行时对变频电机工作的影响,从系统的角度对变频电机在电磁设计、耐电晕绝缘系统、轴承绝缘技术、结构设计等方面进行了总结。     

A new medium-voltage PWM inverter topology for adjustable-speeddrives

In this paper, a new pulsewidth modulation (PWM) inverter topology suitable for medium-voltage (2300/4160 V) adjustable-speed drive systems is proposed. The modular inverter topology is derived by combining three standard three-phase inverter modules and a 0.33-pu output transformer. The output voltage is high-quality multistep PWM with low dv/dt. Further, the approach also guarantees balanced operation and 100% utilization of each three-phase inverter module over the entire speed range. These features enable the proposed topology to be suitable for powering constant-torque, as well as variable-torque type loads. Clean power utility interface of the proposed inverter system can be achieved via an 18-pulse input transformer. Analysis, simulation and experimental results are shown to validate the concepts     

A passive EMI filter for preventing high-frequency leakage current from flowing through the grounded inverter heat sink of an adjustable-speed motor drive system

This paper focuses on the high-frequency leakage current flowing through the grounded heat sink of a voltage-source pulsewidth-modulation (PWM) inverter in an adjustable-speed motor drive system. A passive electromagnetic interference (EMI) filter is proposed, designed, and tested for a 200-V 3.7-kW drive system. This filter does require access to the ungrounded motor neutral point. An equivalent common-mode circuit for the drive system equipped with the EMI filter is derived from experimental waveforms along with theoretical discussions. Experimental results verify that the EMI filter is viable and effective in eliminating both heat-sink and motor-frame leakage currents from the drive system.     

A new modular motor-modular inverter concept for medium-voltageadjustable-speed-drive systems

In this paper, a new modular motor-modular inverter concept for medium-voltage adjustable-speed drive (MV-ASD) systems is introduced. It is shown that standard MV motor winding connections can be reconnected into several three-phase groups, each powered by a separate three-phase pulsewidth modulation inverter, resulting in a high-performance MV-ASD system. The proposed approach is fault tolerant and can continue to operate at reduced power levels, under inverter and/or motor faults. An example 250 hp four-pole 60 Hz 2300 V/4160 V motor winding connection diagram along with the associated inverter configurations is analyzed. Results from analysis are presented on the aspects of faults and motor operation under partial winding excitation. Experimental results on a low-voltage (460 V) 10 hp ASD are demonstrated     

三相交流电机与变频器的配套使用

如何实现变频调速,如何才能正确的运用变频调速电动机以及变频器和电机如何配套才能使变频调速电机发挥其优势,文章就此问题进行了分析,并提出了可行方案。