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A method for suppressing harmonic current of DC capacitor

A harmonic current and capacitor technology, applied in the field of harmonic current suppression of DC capacitors, can solve the problem that the harmonic current suppression method of DC link capacitors is rarely mentioned, and achieve the effect of reducing harmonic content and current amplitude

Active Publication Date: 2019-10-08
CHINA THREE GORGES UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

There has been a lot of research on improving the control of current or power flow to suppress low-frequency harmonic currents, but there is little mention of methods for suppressing harmonic currents in DC link capacitors

Method used

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  • A method for suppressing harmonic current of DC capacitor
  • A method for suppressing harmonic current of DC capacitor
  • A method for suppressing harmonic current of DC capacitor

Examples

Experimental program
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Effect test

Embodiment

[0024] A method for suppressing harmonic currents of DC capacitors, comprising the following steps:

[0025] In order to fully take into account the influence of a single PWM carrier phase shift on the harmonic current components. Such as figure 1 A back-to-back converter is shown where both the rectifier and the inverter have three phases. DC link harmonic current i generated by each phase dc (t) can be expressed as AC i ac (t) and the product of the switching function sf(t).

[0026] i dc (t)=sf(t)×i ac (t) (1)

[0027] where i dc (t) is the DC link harmonic current generated by each phase, i ac (t) is the AC harmonic current, and sf(t) is the switching function.

[0028] Due to the switching characteristics of the converter, there will also be some harmonic currents on the AC side. However, the amplitudes of these harmonics are usually so small that they can basically be ignored. Therefore, an alternating current can be represented by only the fundamental frequen...

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Abstract

Disclosed is a direct current capacitor harmonic current suppression method. Back-to-back converters are adopted; the active direct current link capacitor current in the back-to-back converters is from superposition of direct currents of a rectifier i<dcr> and an inverter i<dci>; the phases of harmonic components in the two currents i<dcr> and i<dci>are determined by the relative phase PWM carrier waves of the rectifier and the inverter; and by actively controlling and regulating the frequencies and phases of PWM carrier waves in the rectifier and the inverter, the direct current link harmonic currents from the two converter levels can be the same in phases, so that the capacitor harmonic current minimization can be achieved. By adoption of the direct current capacitor harmonic current suppression method provided by the invention, harmonic contents and current amplitudes in the first and second carrier frequency bands in the direct current link capacitor current can be obviously lowered; and by virtue of the method, the power supply mass specification can be satisfied and capacitor current harmonic can be effectively reduced without using a high-capacity direct current link capacitor.

Description

technical field [0001] The invention relates to the fields of power electronic devices and harmonic suppression, in particular to a method for suppressing harmonic currents of DC capacitors. Background technique [0002] Two-level, three-phase AC-DC-AC converters are called "back-to-back" converters, especially known for their high power factor and high efficiency, as well as the ability to bidirectional power flow, and have been applied in many fields, Examples include industrial drives, wind power generation and electric transportation. [0003] The switching power converter injects current pulses from the rectifier and inverter sides into the DC link. These current pulses cause losses in the DC link capacitors, increasing the capacitor rating requirements and thus increasing weight, volume and cost, as well as low power density and reliability issues. Therefore, the suppression of harmonic currents in DC link capacitors has received extensive attention. At present, the...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02M1/12H02M5/458
Inventor 刘雪婷张树冰
Owner CHINA THREE GORGES UNIV
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