Ripple current peak value based random switching frequency modulation method for NPC converter

A ripple current and switching frequency technology is applied in the field of random switching frequency modulation of NPC converters based on the peak value of ripple current, which can solve the problems of high output ripple current of the converter and low operating efficiency of the converter.

Active Publication Date: 2018-05-18
XIAN UNIV OF TECH +1
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Problems solved by technology

[0006] The purpose of the present invention is to provide a random switching frequency modulation method for NPC converters based on the peak value of the ripple current, which solves the problems of low operating efficiency of the existing converters and high output ripple current of the converters

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  • Ripple current peak value based random switching frequency modulation method for NPC converter
  • Ripple current peak value based random switching frequency modulation method for NPC converter
  • Ripple current peak value based random switching frequency modulation method for NPC converter

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Embodiment Construction

[0079] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0080] Such as figure 1 Shown is the schematic diagram of the three-level NPC converter of the present invention, including the three-phase AC part (if it is a three-level inverter structure, the three-phase AC part is the load; if it is a three-level rectifier, static var Generator and other devices, the three-phase AC part is AC source plus three-phase AC smoothing reactor), the external part of the three-level DC side (if it is a three-level inverter structure, the external part of the DC side is a DC voltage source , the DC source can be an actual power supply, or a DC source obtained by rectifying the AC power supply; if it is a three-level rectifier structure, the external part of the DC side is the load; if it is a three-level static var generator, the DC There is no external part on the side), the main circuit part of the three-level...

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Abstract

The invention discloses a ripple current peak value based random switching frequency modulation method for an NPC converter. The method includes steps of 1, obtaining a three-phase modulation wave according to a carrier wave pulse width modulation method, setting a fixed switching period and solving and outputting a, b and c phase switch states and corresponding acting time of the three phase switches; 2, according to the maximal value and an inflection point value of the slope of ripple current in the three phases, determining the ripple current maximal value, and solving a random switching period meeting a ripple current limit value; 3, using a random switching period for replacing the fixed switching period, and calculating three-phase switch acting time in the random switching period and forming the finally modulation waveform. According to the invention, the ripple current maximal value is obtained through comparison and the switching period is adjusted, so that the ripple currentmaximal value meets the limit value of the ripple current valid value in the random switching period. Therefore, the harmonic content of current output by the converter is reduced effectively and a good practical value is achieved.

Description

technical field [0001] The invention belongs to the technical field of power electronics, and in particular relates to a random switching frequency modulation method of an NPC converter based on a ripple current peak value. Background technique [0002] In recent years, three-phase voltage source pulse width modulation (PWM) converter is one of the most widely used power electronic devices in power conversion applications. Space Vector PWM (SVPWM) and Discontinuous PWM (DPWM) are two typical modulation methods. [0003] For a long time, for the PWM control mode of the three-phase converter, the switching cycle is fixed. However, simply treating the switching period as a constant value loses important degrees of freedom for system performance improvement. Also, since the spectral peaks are close to harmonics of the switching frequency, EMI noise peaks will also be larger around these frequencies, making the ripple current problem even worse. [0004] Random PWM (RPWM) is c...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02M7/5395H02M1/12
CPCH02M1/12H02M7/5395
Inventor 李宁高桐曹志浩张辉周登科何俊成范聪
Owner XIAN UNIV OF TECH
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