Method for setting up modularized multi-level converter composite structure model

Abstract

The invention discloses a method for setting up a modularized multi-level converter composite structure model in the field of power transmission and distribution technology. Firstly, sub-modules on each bridge arm of a half-bridge converter HBMMC are divided into groups, and the sub-modules in an upper group are changed into full-bridge sub-module FBSM structures, and the sub-modules in a lower group are changed into half-bridge sub-module HBSM structures. Secondly, the upper group and the lower group of every bridge arm are respectively subjected to sequencing gating, and the group in full-bridge sub-module HBSM structures is switched on through adoption of an alternative breakover control method. Finally, six bridge arm electric reactors on a modularized multi-level converter are respectively connected with a discharging access in parallel mode. The method has the advantages that the modularized multi-level converter composite structure model is strong in direct current fault ride-through capability, and simultaneously does not need so many semiconductors like a full-bridge modularized multi-level converter FBMMC, and achieves good uniformity in technology and cost.

Description

technical field [0001] The invention belongs to the technical field of power transmission and distribution, and in particular relates to a method for establishing a hybrid structure model of a modular multilevel converter. Background technique [0002] Modular multilevel converters (MMCs) have been successfully used in high-power converters, mainly in the field of high voltage direct current (HVDC) transmission. Compared with traditional two-level and three-level voltage source converter HVDC (Voltage Source Converter based HVDC, VSC-HVDC), modular multilevel converter HVDC (ModularMultilevel Converter based HVDC, MMC- HVDC) has many advantages: the AC side and the DC side can be fully controlled, the DC bus does not need to install capacitors, the power electronic equipment has the ability to operate redundantly after a fault, no need to install AC filters, etc. Due to the unique advantages of MMC, MMC-HVDC has become the development trend in the field of HVDC in the futur...

AI Technical Summary

Problems solved by technology

[0003] When a bipolar DC short-circuit fault occurs in the flexible DC transmission system, the freewheeling effect of the anti-parallel diode of the insulated gate bipolar transistor (Insulated Gate Bipolar Transistor, IGBT) in the HBMMC-HVDC and the two- and three-level VSC-HVDC makes the AC system A three-phase short-circuit occurs at the short-circuit point, and the short-circuit current cannot be cut off by the converter itself, seriously endangering the safe operation of the system

At the same time, due to the immature manufacturing process of high-voltage and large-capacity DC circuit breakers, the existing multi-terminal flexible DC projects must require DC cables to have extremely high reliability, that is, require extremely low DC fault occurrence probability, which limits to a certain extent The development and application of flexible direct current to multi-terminal power transmission field

[0004] In order to solve this problem, Professor R. Marquardt, the founder of the HBMMC topology, introduced a full-bridge MMC (Full-BridgeMMC, FBMMC) structure in his thesis that can traverse severe DC faults. Each full-bridge sub-module (Full-BridgeMMC) Bridge Sub-module, FBSM) can output three levels, which can interrupt the bridge arm current in any direction, and can change the DC bus voltage polarity of MMC, but it requires double the number of semiconductor devices

Since FBMMC requires twice as many semiconductor devices as HBMMC, this seriously restricts the engineering application of FBMMC, which is why the current MMC-HVDC project adopts the half-bridge structure.

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