PWM逆变器驱动异步电动机采用长线电缆时电压反射现象的研究

PWM逆变器驱动的异步电动机,在逆变器和电动机之间采用长线电缆传输时,会产生电压反射现象,导致在电动机端产生过电压,高频阻尼振荡,使电动机绝缘老化,造成电动机在短期内绝缘击穿等事故,这是PWM逆变器驱动异步电动机采用长线电缆所产生的负面效 应,文中首先分析了长线电缆传输时由于长线电缆的分布参数所产生的电压反射现象及其所造成的过电压等负面效应,分析表明电动机端产生的过电压与逆变器输出PWM脉冲上升时间和电缆长度有关。PWM脉冲上升时间愈短,电缆愈长,反射现象愈明显。采用低成本无源滤波技术可消除这种负面效应,文中分析和设计了一种一阶RC电动机端滤波器,用于接在异步电动机的接线端上,实验结果表明该滤波器可有效地减少电动机端过电压等负荷效应,从而提高系统的可靠性。     

新型PWM逆变器输出无源滤波器的研究

研究了变频器在长线传输时产生的过电压问题，理论分析表明，电动机端过电压与PWM变频器采用的开关器件上升时间和PWM变频器与电动机之间的电缆长度密切相关：上升时间越短，电缆长度越长，电压反射现象越显著，过电压也越高。为消除PWM变频器长线传输时在电动机端产生的过电压等负面效应，提出了一种逆变器输出无源滤波器。实验研究验证了该滤波器能够将变频器输出的PWM电压滤成近似正弦波，从而有效地抑制电动机端的过电压。这种滤波器还可以有效降低共模电压。文中分析了这种滤波器的共模结构及其可以降低共模电压的原因，实验验证了设计思想的正确性。同一种结构的滤波器能够同时消除差模dv／dt和共模电压，减小了滤波器的体积和成本，结构简单，是一种消除逆变器输出负面效应的有效手段。     

逆变器端RLC滤波器的参数设计与损耗计算

在长线电缆传输高频脉宽调制(PWM)脉冲的过程中,逆变器输出端通常用RLC滤波器来抑制电机端过电压和高频振荡,但对相关滤波器参数优化设计的研究较少。基于滤波器电感、电容最小值与PWM脉冲上升时间与滤波器电阻之间的定量关系,对上升时间和滤波器电阻的选取原则进行改进,从而有效减小滤波电感和电容,实验验证了所提改进方法的合理性。     

PWM逆变器端过电压滤波器设计

PWM逆变器通过长线电缆与电机连接时,由于电缆分布参数的影响会在电机端产生2倍的过电压,从而使电机承受的应力大为增加.本文在对电压脉冲上升时间与电缆长度关系分析的基础上,提出了一种改进型的逆变器端无源滤波器.通过对滤波器传递函数特性分析,给出了具体的参数选取原则与设计方法.采用本文提出的滤波器可以使电机端的过电压得到对称的抑制,通过在380 V/3 KW电机系统的实验,验证了该滤波器的有效性,取得了良好的效果.     

PWM逆变器输出对异步电动机的不利影响及其抑制分析

文章通过分析,揭示了PWM逆变器驱动的异步电机调速系统时的三个主要的不利影响,即PWM逆变器输出产生的异步电动机端部绕组过电压、谐波电流、以及共模电压。并结合过电压、谐波电流、以及共模电压的特点与产生的机理,分析了仿真研究所需的电缆与异步电动机的数学模型建立的思路与方法,并阐述了不同结构和安置地点的滤波器的设计思想,指出滤波器设计时,应综合考虑的几个重要因素。     

PWM逆变器输出端共模与差模电压 dv/dt滤波器设计

PWM逆变器直接驱动电机时会产生较高dv/dt的共模电压,并由此产生轴承电流和共模漏电流以及严重的电磁干扰(EMI).特别是当逆变器通过长线电缆与电机连接时,由于电缆中分布参数的影响,会在电机端产生电压反射现象,从而在电机端会产生2倍以上的过电压,导致线圈绝缘失败.本文通过对PWM逆变器驱动电机系统产生的共模以及差模电压分析,提出了一种改进型的逆变器端无源滤波器,并给出了参数的设计方法.与传统的滤波器相比,该滤波器可对共模及差模电压dv/dt同时起到抑制作用,从而减小了由此产生的负面效应.实验结果验证了该滤波器的有效性.     

潜油电泵井下监测仪的滤波系统设计

井下潜油电泵机组在PWM变频驱动运行过程中,尤其是在逆变器和井下电动机之间采用长线传输时。会在井下电动机端产生很高的共模电压,会损害井下电路。同时产生严重的电磁干扰影响测试仪器的正常工作。研究PWM逆变器驱动电动机产生共模电压的原因,提出在电动机星点和井下电动机之间采用LC功率滤波器对其进行消除和抑制,保证井下监测仪器的可靠运行。     

变频器驱动系统滤波器设计研究

由于PWM逆变器输出的脉冲电压在电机接线端子及绕组上产生了差模电压和共模电压;特别是当逆变器通过长线电缆与电机连接时,会在电机端产生电压反射现象,从而在电机端形成很大的过电压,危害电气设备的安全运行。通过对PWM逆变器驱动电机系统产生差模和共模电压机理分析的研究,在变频器输出端抑制电机端差模电压的RLC滤波器的基础上,提出一种改进型变频器输出端无源滤波器的方案,并给出了参数的设计方法。该滤波器可对共模及差模电压同时起到抑制作用,仿真结果验证了该滤波器设计方案的有效性,为变频器驱动系统滤波器设计研究提供理论依据。     

电机驱动用长电缆破坏机理分析及防护

采用长线电缆的电动机驱动系统频繁出现电缆绝缘损坏问题,严重影响了系统的可靠运行。在分析变频谐波和电压闪停对长线电缆绝缘影响的基础上,通过PSCAD/EMTDC软件建立了"变频器—长线电缆—异步电机"仿真计算模型,进行了变频谐波和电压闪停情况下长线电缆的过电压、过电流及相应频谱仿真分析。仿真结果表明:变频器输出脉冲波经长电缆传输时会在电缆接头处产生接近两倍的谐波过电压,同时产生谐波过电流导致电缆绝缘降低;电网电压发生闪停后,电机会发生能量倒送,产生短时大电流破坏电缆绝缘。基于仿真结果,设计了一种二阶RLC低通滤波器以抑制变频谐波的危害,并提出了降低电压闪停影响的保护措施,从而有效地保护电缆绝缘。     

基于滤波电容电流补偿的并网逆变器控制

在并网逆变器中,LC滤波器因容易控制和具有良好的高频衰减特性而应用广泛。分析了输出滤波电容对采用LC滤波的并网逆变器并网电流幅值、相位和低次谐波的影响,提出一种采用滤波电容电流补偿和电网电压前馈的数字PI控制策略,给出了离散时间域下控制器参数的设计方法,并从电网谐波阻抗角度分析了控制器抑制电网电压扰动的能力。理论分析和实验证明,该方案能有效降低并网电流的谐波畸变率(THD),提高并网逆变器输出电能质量。     

PWM逆变器-感应电机系统中的过电压抑止滤波器研究

在PWM逆变器供电的感应电机调速系统中，当逆变器与电机之间的电缆超过一定长度后，在电机端可能出现2倍于逆变器直流母线电压的过电压。本文从时域和频域分析了过电压的内在特点，给出了过电压振荡频率与系统参数的函数关系式，根据过电压的形成机理及其特点，以R－C滤波器为例，给出了详细的滤波器参数选取方法。仿真和实验结果证明了按照本文所提供的方法设计的滤波器能够很好地抑止电机过电压。     

Estimation and Reduction of Motor Input Surge Voltage Using Frequency Response Analysis

This paper presents a plain method of calculating the voltage waveform at motor input terminals from the inverter output terminal voltage and also a method of reducing the voltage. The voltage waveform at the motor input terminals is obtained by a frequency domain calculation using the transfer function of the cable and the frequency characteristics of the voltage waveform at the inverter output terminals. The analysis using this method clarifies the mechanism of the rise of the maximum voltage at the motor input terminals, that is, ringing at the motor input terminals, which occurs at specific frequencies at which the transfer gain increases, causing the rise of the maximum voltage. Therefore, to decrease the maximum voltage at the motor input terminals, it is effective to shorten the cable length or cancel the ringing voltage by preswitching. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(4): 11–19, 2014; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22482     

Output filters for PWM drives with induction motors

When an induction motor is energized from a pulse width modulated (PWM) inverter, through long connecting cables, its insulation system can be severely stressed. The high dv/dt voltage pulses at the output of the inverter cause traveling waves in the connecting cable between the inverter and the motor. When the traveling wave reaches the motor, a large impedance mismatch is present which leads to a reflected voltage wave that, when added to the incoming incident wave, can reach two times the inverter output voltage. The resulting overvoltage at the motor terminals stresses the insulation system and can lead to reduced motor life. Various output filter arrangements can be used to condition the inverter output voltage before it is applied to the cable. The advantage of adding output filtering is that the dielectric stress on the motor insulation and the inverter cable charging current can both be reduced. The major disadvantages of adding filtering is that they represent extra cost, they require extra mounting space, and they introduce extra losses in the system. The most commonly used types of inverter output filters are: simple output line inductors; output limit filter; sine wave output filter; and motor termination filter. These filters are discussed     

Filtering techniques to minimize the effect of long motor leads onPWM inverter-fed AC motor drive systems

In this paper, filtering techniques are investigated to reduce the motor terminal overvoltage, ringing, and dv/dt in inverter-fed AC motor drive systems where long leads are required. Analysis is presented to show that the distributed LC of a cable and the pulse-width modulated (PWM) inverter switching action lead to motor terminal voltage reflections and ringing that stress the turn insulation and contribute to bearing currents. First- and second-order shunt filter designs are analyzed and compared. Detailed design equations to match the filter impedance to the cable surge impedance and to determine the filter component values are presented. It is demonstrated that a first-order shunt filter connected at the motor terminals significantly reduces the overvoltage stress and ringing, and also lowers the dv/dt of the PWM switching pulse. Simulation and experimental results are presented to verify the proposed filter designs for 50-ft and 100-ft cable lengths for 460-V PWM insulated gate bipolar transistor (IGBT) AC motor drive systems     

长电缆连接的PWM驱动系统电机端过电压模型

变频器的大量使用,对电机绝缘产生较大影响,尤其是通过长电缆连接的PWM驱动系统在电机端会产生一个明显高于变频器输出的过电压,严重危害电机绝缘。本文基于等效开路电压和短路电流,构建了电机端过电压的数学模型,并通过仿真结果与理论分析比较验证了此方法分可行性。最后,通过构建的模型,分析了此系统中一些因素对电机端电压的影响。     

基于SVPWM控制的潜油电机端过电压分析研究

采用SVPWM技术控制潜油电机时,由于行波反射现象的存在,会在潜油电机端产生很大的过电压,对电机和输电电缆造成绝缘击穿。针对这一问题,本文应用Matlab建立仿真模型,对电动机端和长电缆上的过电压进行仿真,并在电机端加入滤波装置抑制过电压,从而使潜油电机控制系统的设计更加合理,故障率达到最小。     

A novel output filter topology to reduce motor overvoltage

When an induction machine is supplied with a voltage-source pulsewidth-modulation (PWM) inverter, a ringing voltage overshoot appears at motor terminals due to steep PWM voltage pulse propagation along the motor cable. It has been reported that in particular situations, when very long motor cables are used and retrofit installations, the overvoltage could stress motors with poor insulation. This paper presents a novel inverter output filter topology consisting of an LC filter which has the star point of the common-mode capacitors clamped to the + and - dc-link rails by the means of two diodes. The proposed filter drastically reduces the voltage overshoot at the motor terminals, thus reducing motor insulation stress. This is a cheap alternative to more known industrial solutions.     

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     

Surge propagation and overvoltages for PWM‐inverter‐driven motors

The use of PWM inverters with high switching characteristics to provide variable frequency supply to motors causes overvoltage with steep‐fronted waveform on the motor terminals. Insulation failure in motor winding can be caused by this steep‐fronted transient voltage in inverter drive systems. From the point of view of wave propagation with the skin effect of cable conductors, these phenomena have not been reported previously. The main purpose of this paper to describe the exact surge propagation considering the skin effect of cable conductors and the wave deflections at inverter and motor terminals. © 2000 Scripta Technica, Electr Eng Jpn, 132(2): 65–72, 2000