Power frequency transformer-free three phase-single-phase voltage transformation device

Abstract

The invention discloses a power frequency transformer-free three-phase-single-phase voltage transformation device. According to the three-phase-single-phase voltage transformation device, a single-phase-single-phase converter multi-module cascade structure is adopted to withstand three-phase power grid high-voltage; single-phase-single-phase converters at three phases are in cascade connection with one another and then are connected with in series with each other, so as to realize output, and therefore, a power frequency transformer can be omitted, and the three phase-single-phase voltage transformation device can be directly connected with a single-phase power supply network, and output voltage level can be improved; the single-phase-single-phase converter is mainly composed of a rectifying circuit, a bidirectional DC-DC conversion circuit and an inversion circuit. The single-phase-single-phase converters of the voltage transformation device are simple in structure, and therefore, the structure of the system can be greatly simplified, and two-way flow of the power of a three-phase power grid and a single-phase power supply network can be realized, and energy transmission efficiency can be improved, and thus, unbalance of the three-phase power grid can be avoided; and the converters can have reactive power and harmonic compensation functions through selecting proper control strategies, and therefore, electric energy quality of the three-phase power grid side can be improved, and reactive power and harmonic can be compensated for the single-phase power supply network.

Description

technical field [0001] The invention relates to a three-phase-single-phase power electronic transformer device, especially the application in converting the three-phase electricity of the grid into the required single-phase electricity. Background technique [0002] At present, there are a large number of single-phase loads in many industrial fields, and single-phase loads generally have the characteristics of heavy load, low power factor, and high harmonics, which lead to asymmetrical operation of the grid, affect grid reliability, reduce power supply quality, and increase These single-phase loads include electrified railway traction power supply system, induction heating, petrochemical power supply, etc. In order to meet the needs of such loads, three-phase to single-phase transformers are often used, including Scott transformers. The schematic diagram is as follows figure 1 As shown, but the current of the three-phase side of the Scott transformer can only be realized whe...

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Problems solved by technology

[0004] However, due to the limitation of the development level of power electronic devices, in many practical applications, only a single converter cannot be directly connected to the three-phase grid, thus requiring three-phase step-down transformers and single-phase step-up transformers

The existence of the transformer makes the power electronic device system have higher requirements for the corresponding supporting equipment such as the converter and the wire, and the loss of the equipment and the line becomes larger and more complicated, and the volume and weight are difficult to reduce

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