Modular multilevel converter modulation method based on double queues

Abstract

The invention discloses a modular multilevel converter modulation method based on double queues. The method includes: grouping submodules according to on-off status, and sequentially storing the same in an input queue or a remove queue from low voltage to high voltage; selecting number of the to-be-input or to-be-removed submodules according to bridge arm level variation, bridge arm current direction and maximum voltage deviation of the submodules, performing corresponding input and remove operations the selected submodules, and adjusting the two queues. By the method, only the on-off status of the submodules with the largest number or the smallest number in the two queues needs to be changed, switching frequency is kept low, voltage ordering is not required by all submodules, the queues can be adjusted by simple comparison, times and time of comparison required by ordering are reduced, system response speed is increased, and huge engineering application value is achieved.

Description

technical field [0001] The invention belongs to the technical field of electric power system control, and in particular relates to a modulation method of a dual-queue-based modular multilevel converter. Background technique [0002] In 2001, R. Marquardt, a scholar at the Bundeswehr University in Munich, Germany, first proposed a modular multilevel converter (MMC) topology. The bridge arms of this topology adopt the form of cascading basic operating units to avoid a large The switching devices are directly connected in series, and there is no problem such as consistent triggering. However, since the MMC topology disperses and stores energy in the capacitors of each sub-module of the bridge arm, how to perform reasonable modulation in the dynamic process to quickly realize the balance of the capacitor voltage of each sub-module Control, so that the energy is evenly distributed throughout the converter, is one of the difficulties in the realization of the MMC topology. [000...

AI Technical Summary

Problems solved by technology

Although this strategy can greatly reduce the switching frequency of sub-modules and avoid random switching, it is necessary to sort the sub-modules in the state of switching on or off each time

Especially when the number of sub-modules reaches a certain scale, the time required for sorting will increase greatly in the entire control cycle, which will cause delays in control, reduce the operating stability of the system, and increase the risk of system instability. potential risks

[0004] The Chinese patent with the publication number CN102916592A proposes a voltage equalization control method based on the idea of ​​grouping. Although this method improves the capacitor voltage sorting speed of the sub-modules, it still needs to sort all the sub-modules, and still does not overcome the problem of large amount of calculation. shortcoming

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