Sub-module temperature adjustment and balance method under centralized control based on modular multilevel converter

Abstract

The invention discloses a sub-module temperature regulation and balance method based on the centralized control of a modular multi-level converter. ; Calculate the average junction temperature of each sub-module according to the collected data, calculate the virtual voltage bias coefficient of each sub-module according to the average junction temperature; calculate the virtual capacitor voltage of each sub-module according to the virtual voltage bias coefficient of each sub-module, The voltage sorts the sub-modules in the bridge arm in ascending order and establishes a sub-module index list; the number of sub-modules to be turned on is determined in real time by modulating the reference signal, and then according to the sub-module index table and the current direction of the bridge arm, it is determined in real time which should be conducted through the sub-modules, so as to achieve the temperature balance of the sub-modules in the bridge arm. The invention is neither limited to the number of sub-modules nor affects the power quality of the converter connected to the grid, and the control algorithm is simple and easy to understand and implement.

Description

technical field [0001] The invention belongs to the technical field of multilevel power electronic converters. Background technique [0002] Modular multilevel converters have become a very promising topology for HVDC applications. Compared with traditional two-level and three-level voltage source converters, modular multilevel converters do not require series power devices due to the structure of cascaded sub-modules in each bridge arm. Modular multilevel converters It has attracted more and more attention in the high-voltage transmission system. [0003] In addition to efficiency, the reliable operation of high-power converters is also a key indicator, and power devices play an important role in the reliability of converters. A modular multilevel converter contains many sub-modules, and each sub-module includes multiple power devices. In the case of overload, parameter mismatch caused by long-term operation of sub-modules, or failure of some cooling devices, it may caus...

AI Technical Summary

Problems solved by technology

In the case of overload, parameter mismatch caused by long-term operation of sub-modules or failure of some cooling devices, it may cause large temperature differences between one or more sub-modules

Since power devices are considered to be the most vulnerable to failure in power electronic converters, and the failure of power semiconductors is mainly caused by overheating, the large temperature difference of power devices in sub-modules will give a safety hazard to the modular multilevel converter. Reliable operation poses a huge threat

[0004] Aiming at the problem of temperature balance adjustment and control of the sub-module power switch tube of the modular multilevel converter, the existing technology changes the switching frequency of the converter switch tube, adjusts the reactive power, and uses the continuous pulse width modulation and discontinuous pulse width modulation of the driving signal Switching strategies between sub-modules, changing the gate drive voltage and other methods to adjust the temperature between sub-modules, but the above-mentioned methods will increase the complexity of the hardware system and algorithm, affect the output quality of electric energy, and increase the operating cost of the system

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