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A fault-tolerant control method for MMC systems without redundant sub-modules

A control method and system fault-tolerant technology, which are applied in output power conversion devices, electrical components, and AC power input to DC power output, etc., which can solve the problems of large computational load, cumbersome control, and rarely applied MMC modulation strategies. , to improve the utilization rate, reduce the harmonic content, and improve the effect of three-phase automatic voltage equalization.

Inactive Publication Date: 2019-05-31
CHINA UNIV OF PETROLEUM (EAST CHINA)
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Problems solved by technology

The first three control strategies are relatively simple, but they cannot directly realize the fault-tolerant operation of the non-redundant sub-module system; although the multi-level SVPWM technology contains redundant space vectors, the calculation amount is large and the control is cumbersome. In the MMC modulation strategy rarely used

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  • A fault-tolerant control method for MMC systems without redundant sub-modules
  • A fault-tolerant control method for MMC systems without redundant sub-modules
  • A fault-tolerant control method for MMC systems without redundant sub-modules

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Embodiment Construction

[0053] In order to describe the present invention more specifically, the technical solutions of the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0054] Such as figure 1 As shown in the flow chart, the implementation steps of a fault-tolerant control method for an MMC system without redundant sub-modules are:

[0055] Step 1: Determine the position of the faulty sub-module according to the result of fault location, cut off the faulty sub-module through the bypass switch, and do nothing for the remaining normal sub-modules;

[0056] Step 2: On the basis of step 1, according to the range of the number s of faulty sub-modules, the three-phase modulation wave is processed accordingly. When s≤n(1-m) / 2, the reference voltage remains unchanged and the non-action The pulse is distributed to the fault sub-module, and the three-phase modulation wave does not need to be recombined at this time; when s>n(1-m)...

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Abstract

A fault-tolerant control method for an MMC (modular multilevel converter) system without redundant submodules is a method for fault ride-through control in the situation that redundant submodules of an MMC system are used up, but the system does not allow shutdown for overhauling. According to the method, firstly, the positions of fault submodules are detected, the fault submodules are removed through a bypass switch, and other normal submodules are not processed; modulating waves of fault phases are subjected to amplitude limiting according to the number of the fault submodules, a zero-sequence voltage value is calculated, and capacitor voltage of remaining normal submodules of the fault-phase bridge arms is sequenced again; finally, zero-sequence voltage is injected to modulating waves of other normal phases, recombination of the modulating waves is realized, and balance of voltage of output lines is guaranteed. According to the fault-tolerant control method, migration of neutral points of a system is avoided, the equipment reliability is enhanced, the operation efficiency is improved, and ceaseless and stable running of the system is maintained. The invention applies to the field of electrotechnics.

Description

technical field [0001] The invention belongs to the technical field of electric engineering, and in particular relates to a fault-tolerant control method of an MMC system without redundant sub-modules. Background technique [0002] Modular multilevel converter (MMC) has become a hot topic in recent years due to its modular structure, convenient voltage level expansion and strong fault tolerance. The MMC converter can obtain a relatively high-quality output waveform at a lower switching frequency. The reduction of the switching frequency means that the loss of the switching device is reduced, and the reliability of the converter and the economic performance of the system are improved and improved. The harmonic content of the output voltage of the MMC converter is low, which allows direct grid-connected operation without additional filtering links, which is conducive to reducing costs. [0003] Each phase bridge arm of the MMC converter is formed by cascading multiple sub-mod...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02M7/483
CPCH02M7/483
Inventor 马文忠刘勇王晓王金鹏张凯
Owner CHINA UNIV OF PETROLEUM (EAST CHINA)
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