Sub-module temperature adjusting and balancing method based on centralized control of modular multilevel converter

Abstract

The invention discloses a sub-module temperature adjusting and balancing method based on centralized control of a modular multilevel converter. The method comprises the steps: collecting the temperature and bridge arm current of a radiator of each sub-module, the capacitor voltage of each sub-module on a bridge arm and a switching function; calculating the average junction temperature of each sub-module according to the acquired data, and calculating the virtual voltage bias coefficient of each sub-module according to the average junction temperature; calculating the virtual capacitor voltageof each sub-module according to the virtual voltage bias coefficient of each sub-module, performing ascending sorting on the sub-modules in the bridge arm according to the virtual capacitor voltage, and establishing a sub-module index list; determining the number of the sub-modules needing to be conducted in real time by modulating the reference signal, and determining the sub-modules needing to be conducted in real time according to the sub-module index table and the bridge arm current direction, so temperature balance of the sub-modules in the bridge arm is achieved. The method is not limited by the number of sub-modules, does not affect the grid-connected power quality of the converter, is simple in control algorithm, and is 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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