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Cascade inverter H-bridge unit fault detecting method based on harmonic analysis

A cascaded inverter, harmonic analysis technology, applied in the direction of instruments, measuring electricity, measuring devices, etc., can solve the problems of reducing device reliability, increasing system complexity, increasing costs, etc., to achieve the effect of wide detection range

Active Publication Date: 2014-01-22
SOUTHEAST UNIV
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Problems solved by technology

[0004] The fault detection of the H-bridge cascaded inverter can be realized by adding additional hardware circuits, such as installing a voltage sensor on the output side of each H-bridge unit, but this method not only greatly increases the cost, but also increases the system cost. complexity, reducing the reliability of the device

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  • Cascade inverter H-bridge unit fault detecting method based on harmonic analysis
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  • Cascade inverter H-bridge unit fault detecting method based on harmonic analysis

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Embodiment Construction

[0027] The present invention will be further explained below in conjunction with the accompanying drawings.

[0028] A kind of cascaded inverter H-bridge unit fault detection method based on harmonic analysis provided by the invention, the method comprises the following steps:

[0029] Step 1: Output AC voltage sampling:

[0030] Step 1.1: Use the voltage sensor to collect the three-phase voltage of the cascaded inverter as v xo , where x represents phase x, that is, x=a, b, c, a, b, c are three-phase symbols; the analog signal v xo Filtered by a low-pass filter, the filtered signal is v' xo , the cutoff frequency f of the low-pass filter lp = 3f sw , f sw is the switching frequency of the output voltage of the H-bridge unit of the cascaded inverter;

[0031] Step 1.2, for the filtered analog signal v' xo Perform A / D sampling, sampling frequency f s Output voltage switching frequency f for the H-bridge unit sw Integer multiples of , the discrete signal obtained by sam...

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Abstract

The invention discloses a cascade inverter H-bridge unit short circuit fault detecting method based on harmonic analysis of switching frequency, which is suitable for a carrier phase-shifting PWM (pulse width modulation) manner based on the harmonic analysis to output phase voltage and comprises three parts, namely output alternating voltage sampling, extracting and processing of harmonic wave close to the switching frequency, and fault judging and fault locating. Three-phase output voltage of a cascade inverter is respectively subjected to low-pass filtering and A / D (analog-to-digital conversion) sampling, and is subjected to discrete Fourier transformation to obtain characteristic harmonic; a comparison result of the characteristic harmonic amplitude and a fault threshold is utilized as the evidence of fault judging, wherein the fault threshold is obtained by carrying out a series of calculation on command voltage. The fault locating is determined through a phase angle range of the harmonic of the switching frequency. According to the cascade inverter H-bridge unit short circuit fault detecting method based on the harmonic analysis of the switching frequency, which is disclosed by the invention, the three-phase output voltage of the inverter is collected, and no other hardware circuit is additionally arranged, so that the cost is reduced, and the efficiency is improved; the application capability is strong, and the application value in the study on the real time fault detection of the cascade inverter exists.

Description

technical field [0001] The invention belongs to the technical field of application of high-voltage and high-power power electronics technology in power systems, and relates to the short-circuit fault detection of H-bridge units of cascaded inverters under the carrier phase-shifting PWM (pulse width modulation) mode based on switching frequency harmonic analysis method. Background technique [0002] In recent years, with the development of industry and power technology, the H-bridge cascaded structure has become a research hotspot in the fields of grid-connected inverter, energy storage, and power electronic transformers. The H-bridge cascaded inverter has the advantages of large power capacity, small switching device stress, and low harmonic content, so it is widely used in various electrical devices. [0003] Cascaded inverters are structurally easy to realize modularly, and have lower switching losses and harmonic output. However, because it adopts a structure in which m...

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Application Information

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IPC IPC(8): G01R31/02
Inventor 季振东赵剑锋刘巍孙毅超朱泽安
Owner SOUTHEAST UNIV
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