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Direct current capacitor harmonic current suppression method

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: 2017-08-04
CHINA THREE GORGES UNIV
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  • Summary
  • Abstract
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  • 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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  • Direct current capacitor harmonic current suppression method
  • Direct current capacitor harmonic current suppression method
  • Direct current capacitor harmonic current suppression method

Examples

Experimental program
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Embodiment

[0024] A method for suppressing harmonic current of a DC capacitor, comprising the following steps:

[0025] In order to fully consider the influence of a single PWM carrier phase shift on the harmonic current components. like figure 1 Back-to-back converter shown, where both the rectifier and the inverter have three phases. DC link harmonic current i generated per phase dc (t) can be expressed as exchange i ac (t) multiplied by 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 magnitudes of these harmonics are usually so small that they are essentially negligible. Therefore, the alternating current can be represented only by the fundamental frequency component.

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PUM

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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 field of power electronic devices and harmonic suppression, in particular to a method for suppressing harmonic current of a DC capacitor. 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 capability of bidirectional power flow, and have been used in many fields. Examples include industrial drives, wind power and electric transport. [0003] Switching power converters inject current pulses from the rectifier and inverter sides into the DC link. These current pulses cause losses in the DC link capacitors, increase the requirements for capacitor ratings and thus increase weight, size and cost, as well as cause low power density and reliability issues. Therefore, the suppression of harmonic currents in DC link capacitors has received extensive attention. At present, there has been a lo...

Claims

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Application Information

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IPC IPC(8): H02M1/12H02M5/458
Inventor 刘雪婷张树冰
Owner CHINA THREE GORGES UNIV
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