A modulation method for reducing low-order harmonics of AC voltage in modular multilevel converters

A modular multi-level, AC voltage technology, applied in the direction of converting AC power input to DC power output, electrical components, output power conversion devices, etc., can solve problems such as unapplicable, easy divergence of the system, complex PI parameter design, etc. , to ensure that the system does not diverge, is easy to implement, and avoids the effect of PI controller design

Active Publication Date: 2021-06-15
SOUTHEAST UNIV
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Problems solved by technology

However, when this method is used in practice, additional upper and lower bridge arm energy balance controllers must be configured, otherwise the system will easily diverge.
The energy balance controller of the upper and lower bridge arms requires complex PI parameter design
In addition, some scholars started from the sub-module level, combined with the carrier phase-shift pulse width modulation method, assigned a carrier to each sub-module, and changed the carrier amplitude of the module in real time through the capacitor voltage of the module, thus correcting the module in each sub-module. The input duty cycle within a carrier cycle, but this method is only applicable to the situation where each module is attached with a dedicated capacitor voltage equalization controller, and cannot be used in the more general case of capacitor voltage equalization control based on bridge arm capacitor voltage sorting. application

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  • A modulation method for reducing low-order harmonics of AC voltage in modular multilevel converters
  • A modulation method for reducing low-order harmonics of AC voltage in modular multilevel converters
  • A modulation method for reducing low-order harmonics of AC voltage in modular multilevel converters

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Embodiment Construction

[0028] Embodiments of the invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below by referring to the figures are exemplary only for explaining the present invention and should not be construed as limiting the present invention.

[0029] The modulation method for reducing the low-order harmonics of the MMC AC voltage proposed by the present invention, according to the actual value of the capacitor voltage of the upper and lower bridge arms of each phase, changes the amplitude range of the stacked carrier wave of the upper and lower bridge arms in real time through calculation, respectively, The modulation result of the bridge arm is corrected, thereby equivalently correcting the switching function of the bridge arm, and reducing the low-frequency harmonics of the MMC AC voltage caused by the fluctuation of the capacitor voltage.

[0030] A modulation method for reducing low-order harmonics of MMC ...

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Abstract

The invention discloses a modulation method for reducing the low-order harmonics of the AC voltage of a modular multilevel converter (MMC). The actual measurement value of the voltage calculates and changes the amplitude range of the carrier wave in real time, thereby correcting the modulation result of the bridge arm and reducing the low-frequency harmonics of the MMC AC voltage caused by the capacitor voltage fluctuation. Compared with the existing modulation method, the modulation method proposed by the present invention takes into account the influence of the module capacitor voltage fluctuation on the AC output voltage, and equivalently corrects the bridge arm switching function by changing the carrier amplitude, so it can significantly reduce the voltage caused by the capacitor voltage fluctuation. Low-order harmonic problems caused by AC voltage.

Description

technical field [0001] The invention relates to a low-order harmonic modulation method for reducing the AC voltage of a modularized multilevel converter, and belongs to the technical field of high-power multilevel power electronic converters. Background technique [0002] The modular multilevel converter (MMC) adopts a cascaded structure of multiple modules, which is easy to expand, overcomes the limitations of the voltage level of the current fully-controlled power switching devices and the difficulty of connecting devices in series, and has high efficiency , so it is very suitable for the field of medium-high voltage and large-capacity power electronic conversion, and has great application prospects in medium-voltage occasions such as medium-voltage motor drives and medium-voltage distribution networks. [0003] The improvement of the quality of AC voltage waveform is one of the important research contents of MMC. According to the different spectrum distribution, the harm...

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02M1/12H02M7/483
CPCH02M1/12H02M7/483
Inventor 王宝安邓富金喻强
Owner SOUTHEAST UNIV
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