Power electronic transformer for high voltage distribution

Abstract

The invention relates to a three-phase power electronic transformer for a high voltage distribution system. An input stage is provided with a cascade connection type modular convertor (1), and an isolation stage comprises a plurality of isolation type DC-DC convertors (2) of which the inputs are connected in series and outputs are connected in parallel. An output stage comprises one or more single-phase or three-phase inverters (3) connected on a common direct current bus. Three input ends of the cascade connection type modular convertor (1) are connected with a three-phase high voltage alternating-current network, and two output ends are respectively connected with an anode and a cathode of a high voltage direct current bus capacitor (4). The isolation type DC-DC convertors (2) comprises two second low voltage power units, and the input end of each isolation type DC-DC convertor (2) is connected with the anode and the cathode of a first low voltage direct current capacitor of the high voltage direct current bus capacitor (4). The output ends of the isolation type DC-DC convertors (2) are connected in parallel and are connected with the anode and the cathode of a second low voltage direct current bus capacitor (5). The anode and the cathode of the second low voltage direct current bus capacitor (5) are connected with one or more single-phase or three-phase inverters (3) of the common direct current bus of the output stage.

Description

technical field [0001] The invention relates to a power electronic transformer, in particular to a three-phase power electronic transformer for high-voltage power distribution. Background technique [0002] The traditional power transformer is the basic component equipment of the power system, and its outstanding advantages are simple manufacturing process, high reliability and low price. However, traditional power transformers can only realize single voltage level conversion and isolated transmission of electric energy. In addition, due to the nonlinearity of ferromagnetic components, it is easy to cause distortion of the voltage and current of the power grid, resulting in harmonic pollution; and the secondary voltage cannot be kept constant when the load changes; it does not have continuous adjustment and comprehensive control capabilities for voltage and current; it cannot Realize the interaction with other equipment in the grid; it cannot meet the requirements of the fu...

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Problems solved by technology

[0003] Among the existing power electronic transformer topologies, US patents US 2006 / 0221653A1 and US 7050311B2 adopt a diode-clamped three-level structure on the high-voltage output side, which greatly limits its application in power system distribution networks, especially Application of high voltage distribution network

The US patent US 2006 / 0028848A1 uses three multi-winding power frequency transformers on the high voltage side, which greatly increases the volume and weight of power electronic transformers

The U.S. Patent US 005943229A, the European Patent EP 0989016A2, the Chinese Patents 200910025824.3, 200910184407.3, 02139030.4, and the utility model patent ZL02290343.7 all use a lot of intermediate frequency or high frequency transformers, and the high voltage side of the three-phase transformer is all made of single-phase transformers. Star-connected converters do not take advantage of the three-phase converters

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