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Switching frequency minimization harmonic suppression pulse width modulation method for two-level inverter

A pulse width modulation, switching frequency technology, applied in the application field, to achieve the effect of small switching loss, high energy conversion efficiency, and low heat dissipation pressure

Active Publication Date: 2018-12-11
CHINA UNIV OF MINING & TECH (BEIJING)
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, these discoveries are only accidental discoveries when studying the characteristics of SHE solutions, not actively exploring the problem of how many switching angles are the minimum required to eliminate a certain number of harmonics

Method used

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  • Switching frequency minimization harmonic suppression pulse width modulation method for two-level inverter
  • Switching frequency minimization harmonic suppression pulse width modulation method for two-level inverter
  • Switching frequency minimization harmonic suppression pulse width modulation method for two-level inverter

Examples

Experimental program
Comparison scheme
Effect test

specific Embodiment 1

[0020] Step 1. Sampling the two-level PWM waveforms within a fundamental period P at equal intervals, expressing it as

[0021] x=[x 1 , x 2 ,...,x n ] T

[0022] where n is the number of sampling points, x i ,i=1,2,...,n is the state of the PWM waveform at the i-th sampling point, and its value is 1 or -1;

[0023] Step 2. Express the switching frequency L as the following quadratic function about x

[0024] L=x T A T Ax

[0025] in

[0026]

[0027] Step 3. Expand the two-level PWM waveform into the following Fourier series:

[0028]

[0029] The calculation formula of the Fourier coefficient is as follows

[0030]

[0031]

[0032] According to the rectangular calculation formula of numerical integration, the Fourier coefficients can be approximated as

[0033]

[0034]

[0035] in

[0036]

[0037]

[0038] Among them, k=1 means the fundamental wave, k=2, 3... means the harmonic order;

[0039] Step 4. According to the result of step 3...

specific Embodiment 3

[0062] Assuming that the number of sampling points in one cycle of the PWM waveform is 720, the sequence of binary variables is

[0063] x=[x 1 , x 2 ,...,x 720 ] T

[0064] The switching frequency L is expressed as a quadratic function of x as follows

[0065] L=x T A T Ax

[0066] in

[0067]

[0068] Suppose the harmonic to be eliminated is the 5th, 7, 11, 13, 17, 19, 23, 25th harmonic, and k is {1, 5, 7, 11, 13, 17, 19, 23, 25}, Construct the following binary quadratic programming model

[0069] minL=x T A T Ax

[0070]

[0071]

[0072] Bx≤e

[0073] x ∈ {-1, 1} n

[0074] in

[0075]

[0076]

[0077] B=[s 5 ,s 7 ,s 11 ,s 13 ,s 17 ,s 19 ,s 23 ,s 25 , c 5 , c 7 , c 11 , c 13 , c 17 , c 19 , c 23 , c 25 ] T

[0078] take a 1 =0.6,b 1 =0,e=[0.01,0.01,...,0.01] T . Use the YALMIP toolbox in MATLAB to find the solution x of the quadratic programming model as follows:

[0079] [1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,...

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Abstract

The invention discloses a switching frequency minimization harmonic suppression pulse width modulation method suitable for a two-level inverter, The main technical features include: sampling the two-level PWM waveform in one fundamental period at equal intervals and representing it as a binary variable sequence, and using the first-order difference matrix to represent the switching frequency as aquadratic function of the binary variable sequence; The PWM waveform is expanded by Fourier series, and the linear constraint conditions of fundamental wave and harmonic wave with respect to binary variable sequence are established according to numerical integration formula. A binary quadratic programming model or 0-1 quadratic programming model is constructed by taking the switching frequency asan optimization target function. The quadratic programming model is solved and the discrete two-level PWM waveform is obtained. Compared with the specific harmonic elimination method commonly used atpresent, the method disclosed by the invention obviously reduces the number of switch angles required when the same number of harmonics are eliminated, which can effectively reduce the switching lossof the inverter and improve the energy conversion efficiency.

Description

technical field [0001] The invention relates to the field of power electronic systems and control methods thereof, and relates to a pulse width modulation method for simultaneously optimizing the switching frequency and harmonics of a two-level inverter, and is particularly suitable for application fields such as high-power inverter or rectification. Background technique [0002] For PWM inverters, power quality and conversion efficiency are a pair of contradictions to a certain extent. As the switching frequency increases, the harmonics will move to high frequency, which is easier to filter out, so the output power quality of the inverter is improved, but the switching loss will increase with the increase of switching frequency, which will reduce the conversion efficiency And increase heat dissipation pressure. How to reduce the switching frequency as much as possible on the premise of ensuring the power quality standard of the grid is of great significance to the optimal ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02M7/483H02M1/08
CPCH02M1/08H02M7/483H02M1/0054Y02B70/10
Inventor 杨克虎李华伟何飞王晨旭
Owner CHINA UNIV OF MINING & TECH (BEIJING)
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