使用基本PWM技术的电压源逆变器的三相电性能分析与仿真 Performance Analysis and Simulation of Th ree Phase Voltage Source Inverter using basic PWM Techniques

【来自IEEE xplore,翻译未经授权,基本是机翻。只是用于学习】

Abstract:

This paper illustrates use of different Pulse Width Techniques for a three phase voltage source inverter using Matlab Simulink software. These techniques help in reducing harmonic content in power supply as well as in controlling output voltage and frequency. The techniques which we have demonstrated are Multiple PWM, Sinusoidal PWM (SPWM), Trapezoidal PWM, Staircase PWM, 60° PWM and Third Harmonic PWM. Though these techniques are very good at reducing lower order harmonics, effi ciency of an inverter can’t be effectively increased due to the presence of higher order harmonics. To eliminate these harmonics, a fi lter is designed.

本文说明了不同脉冲的使用三相电压源逆变器的宽度技术使用Matlab Simulink软件。 这些技术有助于减少电源以及电源中的谐波含量,控制输出电压和频率。 我们展示的是多重PWM正弦波PWM(SPWM),梯形PWM,60°PWM和三次谐波PWM。 虽然
这些技术非常擅长降低低阶谐波,逆变器的效率无法有效由于存在高次谐波而增加。为了消除这些谐波,设计了一个滤波器。

1. Introduction

Power systems designed to function at the fundamental frequency are prone to unsatisfactory operation and, at times, failure when subjected to voltages and currents that contain harmonics. A harmonic is a component of a periodic wave having a frequency that is an integral multiple of the fundamental power line frequency. Nowadays, a pure sinusoidal wave is a conceptual quantity as harmonics are always present in the periodic wave.

设计为以基频运行的电源系统容易出现操作不令人满意的情况,有时在遭受包含谐波的电压和电流时有时会发生故障。 谐波是周期波的一部分,其频率是基本电力线频率的整数倍。 如今,纯正弦波已成为概念量,因为谐波始终存在于周期波中。

Such distorted sinusoidal waves are generally produced by non linear loads and in inverters1. Reduction of harmonics is important as these have various adverse effects on the power system components. Some of them are discussed1-4: Conductor Overheating-Conductor overheating is a function of square rms current per unit volume of the conductor.

这种失真的正弦波通常是由非线性负载产生的,并且是在逆变器中产生的。 降低谐波非常重要,因为这些谐波会对电力系统组件产生各种不利影响。 其中的一些将在1-4中讨论:导体过热导体过热是单位体积导体的均方根电流的函数。

Harmonic currents can cause “skin effect” which increases with frequency. Reduced life of Capacitors- Capacitors are affected by heat rise increases due to power loss .If a capacitor is tuned to one of the characteristic harmonics such as 5th or 7th , overvoltage and resonance can cause dielectric failure . False operations of fuses and circuit breakersHarmonics can cause false operations and trips, damaging or blowing components for no apparent reasons.

谐波电流会导致“趋肤效应”,并随频率增加。 电容器寿命的缩短-电容器会因功率损耗而增加热量,从而影响电容器的工作。如果将电容器调谐至特征谐波之一(例如5th或7th),则过电压和谐振会导致介电故障。 保险丝和断路器的错误操作谐波可能会导致错误的操作和跳闸,无明显原因损坏或烧毁组件。

Overheating of transformer windings- Transformers have increased iron and copper loses or eddy currents due to stray fl ux losses which cause excessive overheating in the transformer windings. Motors increased hysteresis and eddy current losses in the magnetic core resulting in increase in the operating temperature of the core and the windings surrounding the core. Hence, this paper deals with the reduction of harmonics in inverter output voltage waveforms.

变压器绕组的过热-由于杂散的磁通损耗而导致变压器绕组中的过热,变压器铁和铜的损耗或涡流增加。 电动机增加了磁芯中的磁滞和涡流损耗,从而导致了磁芯和磁芯周围绕组的工作温度升高。 因此,本文致力于降低逆变器输出电压波形中的谐波。

One way to do this is to insert fi lters between the load and the inverter. If the inverter output voltage contains high frequency harmonics, these can be reduced by a low-size fi lter, however for the attenuation of low-frequency harmonics the size of fi lter components increases. The fi lter circuit becomes costly, bulky and in addition, the transient response of the system becomes slow.

一种方法是在负载和逆变器之间插入滤波器。 如果逆变器输出电压包含高频谐波,则可以通过减小尺寸的滤波器来减小这些谐波,但是对于低频谐波的衰减,滤波器组件的尺寸会增加。 滤波电路变得昂贵,笨重,此外,系统的瞬态响应变慢。

This shows that low-frequency harmonics should be reduced by some means other than the fi lter and subsequently high frequency components can be easily attenuated by a low size, low cost fi lter5. Thus in this paper PWM techniques have been used to reduce low frequency harmonics and subsequently, a low pass fi lter is added to fi lter out the high-frequency components.

这表明,除了滤波器以外,还应通过其他方式降低低频谐波,随后可以通过小型,低成本滤波器轻松衰减高频分量。 因此,在本文中,PWM技术已用于减少低频谐波,随后,添加了低通滤波器以滤除高频分量。

2. PWM Techniques

In these techniques, a fi xed dc input voltage is given to the inverter and a controlled ac output voltage is obtained by adjusting the on and off periods of the inverter components. The on and off periods of the inverter are controlled by different PWM signals. The PWM signals are pulses with fi xed frequency and magnitude and variable pulse width6. Chennai and Vivekanandha College of Technology for women, Th ird International Conference on Sustainable Energy and Intelligent System (seiscon 2012),VCTW, Tiruchengode, Tamilnadu, India on 27-29 December, 2012.

在此技术中,固定的直流输入电压被提供给逆变器,并且通过调节逆变器组件的导通和截止时间来获得受控的交流输出电压。 逆变器的开启和关闭时间由不同的PWM信号控制。 PWM信号是具有固定频率和幅度以及可变脉冲宽度的脉冲6。 2012年12月27日至29日在印度泰米尔纳德邦Tiruchengode举行的第三届可持续能源与智能系统国际会议(seiscon 2012),Chennai和Vivekanandha女子技术学院。

These are generated by mainly two techniques, Triangle comparison based PWM and Space Vector based PWM7. Here, Triangle comparison based PWM is discussed where a triangular carrier wave is compared with a modulating wave of fundamental frequency. The width of the PWM pulses changes from pulse to pulse according to the modulating wave. The frequency of the carrier signal must be much higher than that of the modulating signal, such that the energy delivered to the load depends mostly on the modulating signal6. Advantages of PWM Techniques8:

它们主要由两种技术生成:基于三角形比较的PWM和基于空间矢量的PWM7。 在此,讨论基于三角形比较的PWM,其中将三角形载波与基频调制波进行比较。 PWM脉冲的宽度根据调制波在脉冲之间变化。 载波信号的频率必须比调制信号的频率高得多,这样,传递给负载的能量主要取决于调制信号6。

PWM技术的优势8:

  • These are easy to implement and control.
  • Lower power dissipation.
  • Lower power dissipation.
  • Reduction of lower order harmonics
  • Filtering requirements are minimized as only higher order harmonics are present
  • Hardware implementation is easy as it is compatible with today’s digital microprocessor.
  • 这些很容易实现和控制。
  • 更低的功耗。
  • 更低的功耗。
  • 降低低次谐波
  • 由于仅存在高次谐波,因此对滤波的要求降至最低
  • 硬件实现容易,因为它与当今的数字微处理器兼容。

Disadvantages of PWM Techniques8:

  • They attenuate wanted fundamental component.
  • Generation of high frequency components. In this paper the following PWM techniques are presented and the performance of each technique is carried.
  • Multiple Pulse Width Modulation.
  • Trapezoidal Pulse Width Modulation.
  • Staircase Pulse Width Modulation.
  • Sinusoidal Pulse Width Modulation (SPWM).
  • 60 degree Pulse Width Modulation.
  • Third Harmonic Pulse Width Modulation (THPWM).
  • 它们减弱了所需的基本成分。
  • 产生高频分量。 本文介绍了以下PWM技术,并介绍了每种技术的性能。
  • 多脉冲宽度调制。
  • 梯形脉宽调制。
  • 楼梯脉冲宽度调制。
  • 正弦脉冲宽度调制(SPWM)。
  • 60度脉冲宽度调制。
  • 第三谐波脉宽调制(THPWM)。

【中间还有一些介绍各种PWM,就不放图了。】

3. Filter Design

A Harmonic Filter is used for elimination of harmonic distortion in the output waveform. There are various types of fi lters that can be used for this purpose; here a simple constant k type low pass passive fi lter is designed. It is a single T section fi lter as shown in Fig. 7. Designing is done based on formulae derived by image method. The formulae used for calculating the fi lter parameters are10. L = Zo / (ð * fc) and C = 1/(ð *fc *Zo) where, Zo = load impedance and fc = cutoff frequency. For three phases, three single T sections are used, each connected in series with one phase as shown in Fig. 8.

谐波滤波器用于消除输出波形中的谐波失真。 有多种类型的过滤器可用于此目的。 这里设计了一个简单的恒定k型低通无源滤波器。 如图7所示,它是一个T形截面过滤器。设计是基于通过图像方法得出的公式进行的。 用于计算滤波器参数的公式为10。 L = Zo /(ð* fc)和C = 1 /(ð* fc * Zo)其中,Zo =负载阻抗,fc =截止频率。 对于三相,使用三个单T形部分,每个部分与一个相串联连接,如图8所示。

4. Simulation Results

The output waveforms and harmonic voltage spectrums of above mentioned techniques are shown below. These are obtained through simulation done by MATLAB Simulink. The data that has been considered is as follows: Modulation index = 0.8 Carrier Frequency = 3 kHz Fundamental Frequency = 50 Hz DC Input Voltage = 400V Cutoff Frequency of fi lter = 1 kHz Resistive Load = 200 ohm The modulation index has been maintained constant for all the PWM technique. The output voltage and the FFT analysis with fi lters and without fi lters for all the techniques are shown in Fig 9 to Fig 13. Finally, the total harmonic distortion and the fundamental voltage for each technique are compared in Table-1 from the simulation result.

上述技术的输出波形和谐波电压频谱如下所示。 这些是通过MATLAB Simulink完成的仿真获得的。 所考虑的数据如下:调制指数= 0.8载波频率= 3 kHz基本频率= 50 Hz直流输入电压= 400V滤波器的截止频率= 1 kHz电阻负载= 200 ohm调制指数已保持恒定 所有PWM技术。 所有技术的输出电压和带滤波器和不带滤波器的FFT分析如图9至图13所示。最后,根据仿真结果,表1中比较了每种技术的总谐波失真和基波电压。

【这儿还有一些模拟结果的图也没放】

5. Conclusion

After a comparative study of these techniques from the point of view of their harmonics spectrum and total harmonic distortion, it is proven that the techniques SPWM and THPWM have better performances compared to other techniques. Also it has been verifi ed that after the addition of the fi lter, higher order harmonics have been eliminated and THD has been reduced.

从这些技术的谐波频谱和总谐波失真的角度对这些技术进行比较研究后,证明与其他技术相比,SPWM和THPWM技术具有更好的性能。 还已经证实,在添加滤波器之后,高阶谐波已消除,THD降低了。

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