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Double-carrier-wave modulation method of modular multilevel converter

A modular multi-level, dual-carrier modulation technology, applied in the direction of converting AC power input to DC power output, electrical components, output power conversion devices, etc. question

Active Publication Date: 2016-02-17
HUNAN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The traditional capacitor-voltage balance control method needs to sort all sub-modules from large to small, and then perform switching operations on the corresponding number of sub-modules according to the number of input sub-modules, voltage magnitude and current direction, which requires a large amount of calculation and switching loss Higher; the capacitor voltage balance control method to reduce the switching frequency only operates on the sub-modules that have been put into operation or the sub-modules that have not been put into operation according to the change in the number of input sub-modules, which reduces the switching frequency, but reduces the capacitance of the switching frequency The voltage balance control method still needs to sort the sub-modules from large to small. When the number of sub-modules is large, the amount of calculation is still large, which affects the performance of the control system.

Method used

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  • Double-carrier-wave modulation method of modular multilevel converter
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Embodiment Construction

[0026] see image 3 , is a flow chart of the dual-carrier modulation strategy and the capacitor-voltage balance control method, including the following steps:

[0027] 1) The number of sub-modules that need to be invested in the upper and lower arms of the three-phase a, b, and c phases is obtained through the dual-carrier modulation strategy. and (in the subscript p represents the upper bridge arm, n represents the lower bridge arm, j∈[a,b,c], and the superscript dcm represents dual-carrier modulation), and further obtains the change in the number of sub-modules that needs to be invested in the kth control cycle ;

[0028] 2) Detect the capacitor voltage and bridge arm current of each sub-module, and realize the capacitor voltage balance control according to the voltage balance control method.

[0029] and represent the reference voltages of the upper and lower arms of the j-phase, respectively. In order to facilitate the analysis of the harmonic characteristics of t...

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Abstract

The invention discloses a double-carrier-wave modulation method of a modular multilevel converter. The method comprises two parts, i.e., double-carrier-wave modulation and a voltage balance control method. First of all, according to reference voltages of upper legs and lower legs, quantities of submodules needing to be invested for the upper legs and the lower legs are respectively obtained through the double-carrier-wave modulation, a submodule change quantity needing to be invested at a current control period is further obtained, and then capacitance voltage balance is realized through the capacitance voltage balance control method. An operation condition is determined according to an absolute value of the invested submodule change quantity, only submodules needing switching operation or removal are calculated, the computation complexity is further reduced on the basis that a switch frequency is reduced, and the performance of a control system is improved. The method provided by the invention has the advantages of easy realization, good harmonic wave characteristics, low switch loss and the like.

Description

technical field [0001] The invention relates to a modularized multilevel converter, in particular to a dual-carrier modulation method of the modularized multilevel converter. Background technique [0002] Modular Multilevel Converters (MMC) have the characteristics of high modularity, easy expansion, easy realization of redundancy, high efficiency, good harmonic characteristics, and four-quadrant operation. Attractive multi-level topology has broad application prospects in flexible DC transmission, motor drive, power quality management and other fields. [0003] The multi-level modulation technology and the capacitor-voltage balance control method are the key technologies for the stable and efficient operation of the modular multi-level converter. At present, the modulation technology of MMC mainly includes specific harmonic elimination method, space vector modulation, nearest level approximation modulation, carrier phase shift modulation, carrier in-phase stack modulation....

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02M7/483H02M7/5387H02M1/12
Inventor 罗安周发云徐千鸣马伏军熊桥坡谢宁曹小辉贺加贝
Owner HUNAN UNIV
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