An intermediate frequency DC-DC autotransformer

Abstract

The invention discloses an intermediate-frequency DC-DC autotransformer used to interconnect two DC systems of different voltage levels. The autotransformer is composed of a first converter group, a second converter group and a third converter group which are sequentially connected in series at a DC side. The positive electrode of the first converter group and the negative electrode of the third converter group are respectively connected with the positive and negative electrodes of a second DC system, and the positive and negative electrodes of the second converter group are respectively connected with the positive and negative electrodes of a first DC system. Each converter group is composed of multiple power units which are connected in series. Each power unit is connected to a common AC bus through an intermediate-frequency AC transformer. The second converter group can be further divided into a second converter positive group and a second converter negative group, so that the system can still run normally when only the first converter group and the second converter positive group are included or only the second converter negative group and the third converter group are included.

Description

technical field [0001] The invention belongs to the technical field of power transmission and distribution in power systems, and more specifically relates to an intermediate frequency DC-DC autotransformer. Background technique [0002] With the development of modular multilevel converters, the use of modular multilevel converters to construct DC power grids has become a hot spot in the power industry in recent years. The interconnection of DC power grids in various regions is an urgent problem to be solved. Due to the different functions of the DC power grids in each region, the different technologies adopted, and the different years of construction, the rated DC voltages of the DC power grids in each region will not be completely consistent. In order to interconnect DC grids of different voltage levels, a DC-DC converter is required. At the distribution network level, DC microgrids are also one of the current technical hotspots, and DC-DC converters are also required to ...

AI Technical Summary

Problems solved by technology

[0004] However, the existing DC autotransformer topology is mainly suitable for industrial frequency (such as 50Hz or 60Hz) operating occasions, and the AC transformer used has the disadvantages of large volume and heavy weight, which makes the existing DC autotransformer technology unsuitable. Ideal for applications with strict footprint and weight restrictions

In order to reduce the size and weight of the DC autotransformer, the DC transformer can be operated at an intermediate frequency (for example, 500Hz), so that the area and weight of the AC transformer can be reduced to about 10% under the condition of power frequency, and the DC autotransformer can be greatly reduced. The volume and weight of the coupling transformer, but there are the following defects in the operation of the existing DC autotransformer at the intermediate frequency frequency: the number of AC transformers included in the existing DC autotransformer technology is small, if the existing DC autotransformer technology Operating at IF frequency, the capacity of each IF AC transformer is too high and will be difficult to manufacture successfully due to material constraints

The existing conventional isolated intermediate frequency DC-DC converter can reduce the volume and weight of the AC transformer because it operates at the intermediate frequency frequency, and the requirement for the capacity of each intermediate frequency AC transformer can be reduced due to the use of modular series and parallel topology, but Conventional isolated intermediate frequency DC-DC converter technology needs to undergo DC-AC-DC conversion, and the total capacity of the converter used is twice the rated transmission power, which has the disadvantages of large capacity and high operating loss

Images