Error frequency modulation method for reducing THD (Total Harmonic Distortion) of single-phase photovoltaic grid-connected inverter

A modulation method and inverter technology, applied in photovoltaic power generation, harmonic reduction devices, single-network parallel feeding arrangements, etc., can solve the problems of not being used in practice, and cannot improve the output performance of the inverter, so as to improve the electric energy High quality, THD reduction, and excellent output performance

CN110365244AActive Publication Date: 2019-10-22HUBEI UNIV OF TECH
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Publication Date
2019-10-22

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Abstract

The invention provides an error frequency modulation method for reducing THD (Total Harmonic Distortion) of a single-phase photovoltaic grid-connected inverter. The topological main circuit of the single-phase photovoltaic grid-connected inverter comprises a direct current source DC, a first switch tube Q1, a second switch tube Q2, a third switch tube Q3, a fourth switch tube Q4, an output filterinductor L, an output filter capacitor C and a load R, wherein the effective value of the output alternating current voltage is recorded as U0, and the input direct current voltage is recorded as Ud.The characteristics are that the first switch tube Q1 and the second switch tube Q2 form a front arm S1, the third switch tube Q3 and the fourth switch tube Q4 form a rear arm S2, the front arm S1 andthe rear arm S2 are respectively controlled by adopting SPWM pulses with different carrier frequencies, the carrier frequency fs is recorded as the switching frequency of the front arm S1, the carrier frequency fm is recorded as the switching frequency of the rear arm S2, fm=nfs, the value range of n is limited according to a formula shown in the description, and the value of n is preferably setin the value range, so that the ratio of the low switching frequency to the high switching frequency of the two bridge arms is enabled to be close to 1 as far as possible.
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Description

technical field

[0001] The invention relates to the technical field of single-phase photovoltaic grid connection, in particular to a frequency-staggering method for a single-phase inverter to reduce the THD (total harmonic distortion) of the inverter. Background technique

[0002] Photovoltaic grid-connection is one of the important applications of photovoltaic power generation. However, the harmonics generated by photovoltaic grid-connected inverters will pollute the grid. Reducing the THD generated by photovoltaic grid-connected devices can effectively reduce the pollution to the grid and increase the grid-connected power. quality.

[0003] The grid connection of large-scale photovoltaic power sources has led to the introduction of a large number of power electronic converters into the power system, so that a large number of nonlinear loads are also added to the power supply system, which will cause serious pollution to the power system and cause more serious power quality...

Examples

Embodiment Construction

[0027] In order to better understand the technical solution of the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

[0028] The embodiment of the present invention provides a method for reducing THD through frequency shift technology, which is implemented for the existing single-phase inverter topology main circuit. The single-phase inverter topology main circuit includes a DC source, a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, an output filter inductor, an output filter capacitor and a load.

[0029] Such as figure 1 As shown, the interleaved topology circuit includes a direct current source DC, a first switching tube Q 1 , the second switching tube Q 2 , the third switching tube Q 3 , the fourth switching tube Q 4 , Output filter inductor L, output filter capacitor C and load R. The four switch tubes are metal oxide semiconductor fi...