A redundant fault-tolerant control method for modular multilevel converters

Abstract

A redundant fault-tolerant control method for a modular multi-level converter, the method sets an inverter controller on the AC side of the modular multi-level converter, and implements a redundant fault-tolerant model for the modular multi-level converter Predictive control, the redundant fault-tolerant model predictive control includes three control objectives of AC current tracking, sub-module capacitor voltage balance, and circulating current suppression, each control objective defines an objective function, and calculates all possible switch state objective function values ​​under the corresponding objective function , where the AC current tracking objective function and the sub-module capacitor voltage equalization objective function calculate the values ​​under all switch states of the MMC, the circulating current suppression objective function calculates the values ​​under all circulating current suppression compensation levels, select the minimum value of the objective function, and record the minimum value of the objective function The switch state corresponding to the value is input into the MMC as the switch state of the MMC at the next moment to realize the circulation suppression and sub-module capacitor voltage balance of the modular multilevel converter under the redundant fault tolerance condition.

Description

Technical field [0001] The invention relates to the technical field of converters, and in particular to a redundant fault-tolerant control method for converters. Background technique [0002] The topological structure of voltage source converter is mainly divided into two-level and three-level forms, which are widely used in DC transmission projects, but this type of topology has the disadvantages of high switching frequency, series dynamic voltage equalization, and large harmonic content. . The modular multi-level converter (MMC) proposed by German scholars Lesnicar and R. Marquardt, compared with the traditional two-level voltage source converter, has a high degree of modularity, low loss, strong scalability, and output The waveform quality is good, and it has the advantages of fault ride-through capability. In 2010, the converter with this topology was used for the first time in the US "Trans Bay Cable" project put into operation by Siemens. In recent years, modular multile...

AI Technical Summary

Problems solved by technology

Although the first solution realizes the symmetrical operation of the system, there are many sub-modules that need to be bypassed, resulting in unstable operation of the converter

Although the second solution greatly reduces the risk of bypassing the normal working sub-modules, it will cause asymmetric operation between the bridge arms of the converter

However, adopting the second scheme will bring many influences to the MMC, such as changes in the circulating current components, unbalanced sub-module capacitor voltages, etc.

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