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A Calculation Method of PWM Harmonic RMS

A calculation method and effective value technology, which is applied in the field of PWM harmonic effective value calculation, can solve problems such as complex process, difficulty in calculating the effective value of each harmonic, and calculating the effective value of each harmonic

Active Publication Date: 2021-08-06
苔花科迈西安信息技术有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The spectrum of this waveform often has main harmonics and more inter-harmonic waves, and the energy is distributed around each harmonic, so it is difficult to calculate the effective value of each harmonic
[0003] In the field of electromagnetic interference, the detector of the receiver has a certain bandwidth, and the energy within the bandwidth is received and the total effective value is detected, so the effective value of each harmonic is an important content in the interference calculation. Simple FFT transformation cannot directly obtain harmonic RMS
[0004] At present, the calculation steps for the effective value of each harmonic of PWM are as follows: After the PWM wave is transformed by FFT, since there are some inter-harmonic waves near the main peak of each harmonic, this makes the energy of each harmonic relatively scattered, not It is convenient to directly calculate the effective value of each harmonic
In order to calculate the total effective value near each harmonic, first use the bandpass filter to extract the spectrum energy near each harmonic, and then calculate the total effective value RMS, this process is complicated

Method used

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  • A Calculation Method of PWM Harmonic RMS
  • A Calculation Method of PWM Harmonic RMS
  • A Calculation Method of PWM Harmonic RMS

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0034] A method for calculating the effective value of PWM harmonics is characterized in that a sawtooth wave is constructed according to the PWM wave.

[0035] The PWM wave is the result of a sawtooth wave carrier modulated with a sine wave.

[0036] The PWM waves include unipolar PWM waves and bipolar PWM waves.

[0037] The steps of causing the sawtooth wave by the unipolar PWM wave are as follows:

[0038] A. Calculate the amplitude and frequency of the unipolar PWM wave;

[0039] B. Construct the sawtooth wave so that its frequency is the same as the carrier frequency of the unipolar PWM wave in A, and its amplitude is twice the amplitude of the unipolar PWM wave in A.

[0040] C. After the sawtooth wave is subjected to FFT operation, each harmonic peak value is obtained;

[0041] D. Divide the peak value of each harmonic by That is, the effective value of each harmonic of the unipolar PWM wave is obtained.

[0042] The slope of the sawtooth wave can be positive or ...

Embodiment 2

[0046] The steps of causing the sawtooth wave by the bipolar PWM wave are as follows:

[0047] A. Calculate the amplitude and frequency of the bipolar PWM wave;

[0048] B. Construct the sawtooth wave so that its frequency is the same as the carrier frequency of the bipolar PWM wave in A, and the amplitude is twice the amplitude of the bipolar PWM wave in A.

[0049] C. After the sawtooth wave is subjected to FFT operation, each harmonic peak value is obtained;

[0050] D. Divide the peak value of each harmonic by That is, the effective value of each harmonic of the bipolar PWM wave is obtained.

[0051] The slope of the sawtooth wave can be positive or negative, such as Figure 8 and Figure 9 shown.

[0052] like Image 6 As shown, the bipolar PWM wave is modulated by a sawtooth wave carrier and a sine wave. After the bipolar PWM wave is transformed by FFT, the harmonic spectrum of each order is obtained as follows: Figure 7 , the interharmonic wave near the main pe...

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Abstract

The invention belongs to the field of electromagnetic interference and relates to a method for calculating effective values ​​of PWM harmonics. The present invention constructs a PWM wave into a sawtooth wave, the frequency of the sawtooth wave is the same as the carrier frequency of the PWM wave, and the amplitude is twice the amplitude of the PWM wave. Using the inventive method, it can effectively solve the problem that the effective value of the PWM wave cannot be directly calculated. Problem, after using the PWM harmonic effective value calculation method of the present invention, the effective value of each harmonic can be directly obtained in the subsequent simulation results, and in the field of electromagnetic compatibility simulation, the independence of each harmonic of the sawtooth wave can be intuitively obtained RMS results of each frequency point.

Description

technical field [0001] The invention belongs to the field of electromagnetic interference, and in particular relates to a method for calculating the effective value of PWM harmonics. Background technique [0002] In the field of power electronics, PWM is a common control method, and its waveform has periodicity on the macroscopic level, and the duty cycle gradually changes on the microscopic level. The spectrum of this kind of waveform often has main harmonic and many interharmonics, and the energy is distributed around each harmonic, so it is difficult to calculate the effective value of each harmonic. [0003] In the scope of electromagnetic interference, the detector of the receiver has a certain bandwidth, and the energy within the bandwidth is received and the total effective value is detected, so the effective value of each harmonic is an important content in the interference calculation. Simple FFT transform does not directly get harmonic rms. [0004] At present, t...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01R23/16
CPCG01R23/16
Inventor 符立梅董立红赵振民
Owner 苔花科迈西安信息技术有限公司
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