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Enhanced VSVPWM (virtual space vector pulse-width modulation) method

A modulation method and enhanced technology, applied in output power conversion devices, electrical components, and AC power input to DC power output, etc., can solve the problems of inability to eliminate the accumulated DC offset of the midpoint potential, poor anti-interference ability, etc.

Active Publication Date: 2015-07-15
SHANDONG UNIV
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Problems solved by technology

But these two methods belong to open-loop control, the anti-interference ability is poor, and the cumulative DC offset problem of the midpoint potential cannot be eliminated

Method used

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  • Enhanced VSVPWM (virtual space vector pulse-width modulation) method
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  • Enhanced VSVPWM (virtual space vector pulse-width modulation) method

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Embodiment Construction

[0059] The present invention will be further described below in conjunction with accompanying drawings and examples.

[0060] The traditional NPC three-level inverter adopts LC filter and purely resistive load.

[0061] Based on the modulation method of the above-mentioned NPC three-level inverter, specifically:

[0062] The turn-on time of each switching device of the three-phase bridge arm obtained by the virtual vector PWM modulation method passes d xp , d xn (x∈{a,b,c}) three groups of six modulated waves are responded. According to the detected DC capacitor voltage difference or midpoint potential fluctuation, the corresponding modulation wave is corrected, thereby changing the action time of the small vector, eliminating the cumulative DC offset of the midpoint potential, and the corrected PWM signal obtained through The driving circuit controls the three-level inverter.

[0063] figure 1 It is the structure diagram of NPC three-level inverter, which adopts a single...

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Abstract

The invention discloses an enhanced VSVPWM (virtual space vector pulse-width modulation) method. The method comprises steps as follows: space vectors are converted into virtual vectors through PWM, and the action time duty ratio of each virtual vector is calculated; duration per unit values of three-phase output voltage at states P and N are figured out according to the correspondence between the virtual vectors and actual space vectors; the duration per unit values of the three-phase output voltage at the states P and N are used as modulating waves respectively, and a three-phase switch state is obtained; small vector action time is adjusted according to the difference between voltage of two direct-current capacitors or the fluctuation magnitude of midpoint potential, and PWM output of an inverter is obtained. With the adoption of the method, the problem of virtual vector PWM midpoint potential cumulative deviation is solved, midpoint potential balance control can be realized within any modulation degrees, the low-frequency fluctuation of the midpoint potential can be completely eliminated, the anti-interference performance of a system is improved, sizes of the direct-current capacitors are reduced, and the output waveform quality is improved.

Description

technical field [0001] The invention relates to an enhanced virtual vector PWM modulation method. Background technique [0002] Three-level inverters are widely used in high-voltage and high-power occasions due to their advantages such as low voltage for switching devices and high-quality output waveforms. However, the inherent problem of unbalanced midpoint potential has obvious restrictions on the promotion of three-level inverter applications. In recent years, many scholars at home and abroad have done a lot of work on this problem. In terms of topology, a mixed-clamp three-level topology was proposed to realize the automatic balance of the midpoint potential; in terms of modulation methods, methods such as zero-sequence component injection and changing the action time of small vectors were proposed and achieved good results. [0003] In the midpoint potential imbalance problem, the fluctuation of the midpoint potential three times the fundamental frequency is called lo...

Claims

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Application Information

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IPC IPC(8): H02M7/487
CPCH02M7/487
Inventor 陈阿莲王伟胜张承慧柴锦
Owner SHANDONG UNIV
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