Modulation Method for Increasing Output Level Number of Full-Bridge Modular Multilevel Converter
A modular multi-level, output-level technology, applied in the conversion of AC power input to DC power output, output power conversion devices, electrical components, etc., can solve the problem of low average voltage of sub-modules, DC bus voltage fluctuation, The capacitor voltage fluctuates greatly, etc., to achieve the effect of increasing the number of AC output levels, reducing the harmonic content, and improving the effect.
Active Publication Date: 2019-10-11
XI AN JIAOTONG UNIV
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[0007] Documents [1] and [2] both make the phases of the modulation waveforms of the upper and lower bridge arms different to increase the output level of the modulation wave without changing the number of modules, but this method will cause the average value of the sub-module voltage to be biased. Low, and the capacitor voltage fluctuates greatly, the bridge arm inductance voltage fluctuates greatly, and the DC bus voltage fluctuates, etc.
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[0036] A hybrid topology modulation method for increasing the output level of a full bridge modular multilevel converter (FBMMC for short), each upper and lower bridge arm of the FBMMC is composed of N full bridge full voltage sub-modules ( Full bridge full voltage sub module, referred to as FBFVSM) and a full bridge half voltage sub module (full bridge half voltage sub module, referred to as FBHVSM), the two sub-modules are properly switched, so that the FBMMC AC output ladder The step height of the wave becomes half of the original, so that the output level of the AC side of the FBMMC is increased from N+1 to 2N+1. The present invention does not cause problems such as sub-module capacitance voltage offset, bridge arm inductance voltage peak, FBMMC DC side voltage fluctuation and the like.
[0037] The concrete realization steps of the present invention are as follows:
[0038] (1) The upper and lower bridge arms are composed of N FBFVSM and 1 FBHVSM;
[0039] (2) The modul...
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The invention discloses a modulation method for increasing output level numbers of a full bridge modular multilevel converter (FBMMC). An upper bridge arm and a lower bridge arm of each phase of the FBMMC respectively comprises a full bridge full voltage sub module and a full bridge half voltage sub module, and the AC-side level numbers output from the FBMMC are increased by appropriate switching of the two sub modules. By the modulation method, the AC output level numbers are increased, the effect of a nearest level approximation method is remarkably improved, and the harmonic component of an output voltage of the FBMMC is remarkably reduced; and moreover, by the modulation method, the problems of capacitance voltage deviation of the sub modules, inductance voltage peak of the bridge arms and voltage fluctuation of a DC side of the FBMMC and the like are prevented.
Description
【Technical field】 [0001] The invention belongs to the field of power electronics and relates to a modulation method for increasing the output level of a full-bridge modular multilevel converter. 【Background technique】 [0002] Modular multilevel converters have highly modularized circuits, which facilitate integrated design, shorten project cycles, save costs, and have broad application prospects. [0003] In order to realize multi-level output on the AC side, a specific modulation method must be adopted. The modulation method of a modular multilevel converter has a key influence on its performance. Currently existing modulation techniques are mainly divided into two categories: multi-carrier PWM modulation techniques and recent level modulation techniques. When the number of modules is low, PWM modulation technology with high switching frequency is usually used. Too high switching frequency means excessive switching loss. Recently, the level modulation strategy can not on...
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IPC IPC(8): H02M7/483
Inventor 司刚全朱建伟雷妤航张彦斌
Owner XI AN JIAOTONG UNIV