A Capacitor Precharging Method for Modular Multilevel Converter Topology

A modular multi-level, topological structure technology, applied in the direction of high-efficiency power electronic conversion, conversion of AC power input to DC power output, electrical components, etc., can solve the problem of reducing the quality of MMC output voltage, output waveform distortion, and increasing hardware costs, etc. question

Active Publication Date: 2019-11-22
SOUTHEAST UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Thanks to the topological structure of the MMC, with the increase of parallel output modules, the quality of the output waveform is higher, closer to a sine wave, but when there are more sub-modules in the MMC, the hardware cost will increase, and when the number of sub-modules in the MMC When less, its output waveform will be distorted, reducing the output voltage quality of MMC

Method used

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  • A Capacitor Precharging Method for Modular Multilevel Converter Topology
  • A Capacitor Precharging Method for Modular Multilevel Converter Topology
  • A Capacitor Precharging Method for Modular Multilevel Converter Topology

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Experimental program
Comparison scheme
Effect test

Embodiment

[0038] Embodiment: A simulation model is used to verify the correctness and effectiveness of the topology and the control strategy.

[0039] Build an open-loop simulation model of a single-phase n+1 hybrid MMC converter in Matlab / Simulink software, and its equivalent schematic diagram is as follows figure 2 shown. Two half-bridge sub-modules and one full-bridge sub-module are connected in series on a single bridge arm. The output waveform of the traditional MMC is 3 levels, and its power quality is very poor, while the output waveform of the n+1 hybrid MMC is 7 levels, which better improves the power quality.

[0040] The hybrid MMC is used to supply power to the inductive load, and its main parameters are shown in Table 1 below.

[0041] Table 1

[0042]

[0043] In the simulation, in order to simulate the start-up pre-charging process of the hybrid MMC converter sub-module, the DC side voltage increases slowly from 0, and the DC side voltage reaches half of the rated ...

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Abstract

The invention discloses an n+1 hybrid modular multilevel converter topology and its control strategy, belonging to the field of power electronics and distributed power generation. Its topology is formed by adding a full-bridge sub-module to the upper and lower bridge arms of each phase on the basis of the traditional modular multilevel converter (MMC) of n half-bridge sub-modules, so that the capacitance voltage of the full-bridge sub-module It is half of the half-bridge sub-module, and the number of output voltage levels is increased from the original n+1 to 2n+3. The invention aims at increasing the output level of the sub-module and improving the output voltage quality of the MMC converter, and proposes its control strategy according to its topological structure: a hybrid modulation mode and a capacitor pre-charging mode, which have a certain effective availability and feasibility.

Description

technical field [0001] The invention relates to a capacitor precharging method for a topology structure of a modular multilevel converter, which belongs to the field of power electronics and distributed power generation. Background technique [0002] With the development of power electronics technology, flexible DC transmission based on voltage source converters has received more and more attention. The essential idea of ​​the modular multilevel converter (MMC) is to reduce the voltage stress on each sub-module by cascading multiple sub-modules. There are n sub-modules in the upper and lower bridge arms of one phase, which can output n+1 levels. During operation, half of the sub-modules in each phase are always in the on state, and half of the sub-modules are in the cut-off state. Due to its modular and cascade structure features, MMC has the advantages of easy expansion and can be flexibly applied to industrial sites. At present, research on MMC mainly focuses on its topo...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02M7/483
CPCH02M7/483H02M1/0054Y02B70/10
Inventor 郑建勇缪惠宇陈虹妃顾盼盼杨赟
Owner SOUTHEAST UNIV
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