Three-phase input single-phase output frequency converter and control method

Abstract

A three-phase input single-phase output frequency converter and its control strategy are composed of a three-phase connected transformer, a cascaded converter A, a cascaded converter B and a cascaded converter C. The primary winding of the three-phase connection transformer is in the form of delta connection, and the secondary winding of the three-phase connection transformer is in the form of Yn connection. Cascaded converter A, cascaded converter B and cascaded converter C are all formed by cascading M identical power modules PM. One end of cascade converter A is connected to terminal a of the secondary winding of the three-phase connection transformer, and the other end is connected to point x; one end of cascade converter B is connected to terminal b of the secondary winding of the three-phase connection transformer, and the other end is connected to to point x; one end of cascaded converter C is connected to terminal c of the secondary winding of the three-phase connected transformer, and the other end is connected to point x. The primary winding of the three-phase connection transformer is connected to the three-phase AC input, and the star points n and x of the secondary winding of the three-phase connection transformer are used as the two connection terminals of the single-phase output.

Description

technical field [0001] The invention relates to a power frequency conversion device for inputting three-phase alternating current and outputting single-phase alternating current and its control strategy. Background technique [0002] The power frequency conversion device with three-phase AC input and single-phase AC output has multiple uses in special occasions, such as converting three-phase power frequency AC into single-phase high-frequency induction heating power supply, converting from three-phase 50Hz public AC power grid to 16.7 Hz electric locomotive single-phase AC occasions, etc. In the prior art, the device for realizing the three-phase AC-single-phase AC frequency conversion of electric energy is often realized by means of multiple conversions of AC-DC-AC. For example, Chinese patent CN201711102337 requires three-stage conversion of the first multilevel converter module, high frequency transformer isolation module and second multilevel converter module to realiz...

AI Technical Summary

Problems solved by technology

[0003] The purpose of the present invention is to overcome the shortcomings of the existing three-phase AC-single-phase AC frequency conversion device, such as many power conversion links, low efficiency, and high cost, and propose a frequency converter that directly realizes the input of three-phase AC and the output of single-phase AC without intermediate DC conversion

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