An Optimal Modulation Method for a Full-Bridge Modular Multilevel Converter

Abstract

The invention discloses an optimized modulation method for a full-bridge modular multi-level converter. While modulating the bridge arm voltage of the integer input sub-module, a SAPWM modulation algorithm is proposed. By considering the full-bridge modular multi-level conversion Adaptively adjust the carrier phase of the upper and lower arms according to the positive and negative conditions of the bridge arm voltage under the pressure-boosting operating condition, and control the The output level of the sub-module of the fractional part of the output voltage, so as to realize the modulation of the bridge arm voltage of the integer and fractional input sub-module at the same time, and can increase the load in the whole boost operation fundamental period of the full-bridge modular multi-level converter The number of voltage levels not only effectively reduces the total harmonic distortion rate of the load voltage, but also increases the harmonic frequency of the load voltage, reducing the cost of filtering, and is suitable for full-bridge modular multi-level under the operating condition of increasing voltage converter.

Description

technical field [0001] The invention belongs to the field of voltage converters, and more specifically relates to an optimal modulation method for a full-bridge modular multilevel converter. Background technique [0002] Full Bridge Modular Multilevel Converter (FBMMC), with its flexible sub-module output capability, shows unique advantages in the fields of voltage boost operation, DC fault ride-through, and motor drive. By generating a negative output level through the sub-module, FB MMC can generate a higher amplitude load voltage under the condition of constant DC voltage, realize boosted voltage operation, and increase the capacity of FB MMC. In the case of a short-circuit fault on the DC side, the fault current on the DC side can be eliminated, reactive power compensation can be provided, and DC fault ride-through can be realized without relying on additional devices. The flexible level output capability of the FB MMC sub-module allows the sub-modules of the same bridg...

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Problems solved by technology

[0006] Aiming at the defects of the prior art, the purpose of the present invention is to propose an optimized modulation method for a full-bridge modular multilevel converter, aiming to solve the inapplicability of the prior art due to the lack of consideration of the negative level output of the integer sub-module Problems in pressure-lifting operating conditions

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