Clamp five-level back-to-back converter with flying capacitor auxiliary bridge arms

Abstract

The invention discloses a clamp five-level back-to-back converter with flying capacitor auxiliary bridge arms. The converter comprises a 5L-Vienna rectifier, neutral-point balancing auxiliary bridge arms, and a 5L-NPC inverter, wherein the 5L-Vienna rectifier is used as a variable speed controller of a permanent magnet synchronous generator, and higher voltage-withstand grade can be realized by adopting a five-level structure; the number of original parts is reduced, the problem of straight-through short circuit does not exist, the reliability is improved, the unity power factor variable speed control strategy can be realized, and the influences of harmonic waves are reduced since the current of the generator can be controlled to be sine waves; in addition, an auxiliary circuit formed by two three-level flying capacitor auxiliary bridge arms, which are connected in series, is provided for cooperating with modifying of the SVM strategy of the 5L-Vienna rectifier to realize neutral-point balancing, the auxiliary bridges can provide an unbalanced current flow path, and the problem of direct current unbalance is solved by using a voltage clamp principle of a flying capacitor.

Description

technical field [0001] The invention relates to a converter system and a control method thereof, in particular to a control method of a five-level rectifier and a capacitor voltage unbalance control method. Background technique [0002] At present, high-power direct-drive wind power generation systems all adopt the technical solution of direct-drive permanent magnet generator + full-power converter. Among them, the full power converter is used as the interface between the permanent magnet wind turbine and the grid, and its capacity is the same as the rated capacity of the system. With the continuous increase of the capacity level of the generator set, the capacity level of the converter must also be increased accordingly, which requires the converter itself and the switching device to have a higher voltage and power level. However, the manufacturing process of power semiconductor materials and withstand voltage limits, the traditional two-level converter has been unable to ...

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Problems solved by technology

With the continuous increase of the capacity level of the generator set, the capacity level of the converter must also be increased accordingly, which requires the converter itself and the switching devices to have higher voltage and power levels. However, the manufacturing process of power semiconductor materials and withstand voltage limits, the traditional two-level converter has been unable to meet the requirements

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