A balanced control method for full bridge MMC capacitor voltages

Abstract

The invention discloses a balanced control method for full bridge MMC capacitor voltages. The method comprises the following steps: (1) a positive input record database, a negative input record database and an abscission record database are established; (2) a sub-module with a maximum capacitor voltage and a minimum capacitor voltage in the record databases and on bridges arms are found out; (3) according to information such as bridge arm levels, bridge arm currents and the capacitor voltages, sub-modules which need to be subjected to switching are selected through logic judgment; and (4) corresponding switching operation is carried out on the selected sub-modules, and data updating is carried out on the record database. According to the invention, under a condition that the capacitor voltages are maintained to be stable, the switching frequency of the sub-modules can be effectively reduced; losses of a transverter can be reduced; and simultaneously, decrease in the system control frequency and system operation performance deterioration, etc., due to ordering problems are avoided.

Description

technical field [0001] The invention belongs to the technical field of power electronic systems, and in particular relates to a method for equalizing and controlling the capacitor voltage of a full-bridge MMC. Background technique [0002] Since Professor R.Marquardt proposed the half-bridge modular multilevel converter (MMC) based on the half-bridge sub-module cascading, in recent years, the half-bridge MMC technology has been vigorously developed, experts and scholars from all over the world Extensive and in-depth research has been carried out on it. Full-bridge MMC is formed by cascading full-bridge sub-modules. Compared with half-bridge MMC, full-bridge MMC has more flexible and superior characteristics, such as DC fault ride-through capability, and a hybrid DC transmission system composed of traditional thyristor converters. It has better trend reversal ability, etc., and has a wider application space. [0003] Whether the sub-module capacitor voltage is balanced seri...

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Problems solved by technology

[0005] Aiming at the above-mentioned technical problems existing in the prior art, the present invention provides a method for equalizing the capacitor voltage of the full-bridge MMC, which not only can effectively reduce the switching frequency of the sub-modules while maintaining the stability of the capacitor voltage, but also reduce the loss of the converter , and at the same time, it can avoid problems such as the decrease of system control frequency and the deterioration of system performance caused by the sorting problem

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