Single-phase power electronic transformer

Abstract

The invention provides a single-phase power electronic transformer. The single-phase power electronic transformer comprises an input-stage circuit, a middle isolating-stage circuit and a DC-AC (direct current-alternating current) inverter, wherein the input-stage circuit comprises a first bridge arm and a second bridge arm; the first bridge arm and the second bridge arm are connected between a positive input end and a negative input end of a high-voltage direct-current bus; the first bridge arm comprises two capacitors which are connected with each other; a connecting line between the two capacitors is connected with an input end of a high-voltage alternating-current bus; an upper half bridge arm and a lower half bridge arm of the second bridge arm comprise a plurality of modular multi-level SM (signal modules); and a connecting line between the upper half bridge arm and the lower half bridge arm is connected with another input end of the high-voltage alternating-current bus. A single-phase half-bridge rectifying circuit is formed by the whole input-stage circuit. The single-phase power electronic transformer is suitable for a high-voltage single-phase rectifier system. Moreover, the power electronic transformer is provided with an alternating-current and direct-current mixed input interface, not only is suitable for an independent alternating-current or direct-current power distribution system, but also is suitable for an alternating-current and direct-current mixed power distribution system. Functions of transformation isolation and power transmission between power grids with different types and voltage classes can be fulfilled.

Description

technical field [0001] The invention relates to the field of electric power technology, in particular to a single-phase power electronic transformer. Background technique [0002] Since the transformer was invented in the 19th century, it has become one of the most basic and important components of the power system. It is widely used in power distribution systems to achieve voltage level conversion and isolation. However, the traditional transformer has many disadvantages: (1) It is huge, and with the increase of the voltage level, the volume and weight of the transformer increase sharply; (2) It is sensitive to power quality, and the distortion generated when it is connected to non-linear loads such as uncontrolled rectification The current will enter the power grid through the coupling effect of the transformer, which will pollute the bus grid and cause the quality of power supply to decline; (3) When a grounding short circuit fault occurs on the load side, the traditional...

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Problems solved by technology

However, the traditional transformer has many disadvantages: (1) It is huge, and with the increase of the voltage level, the volume and weight of the transformer increase sharply; (2) It is sensitive to power quality, and the distortion generated when it is connected to non-linear loads such as uncontrolled rectification The current will enter the power grid through the coupling effect of the transformer, which will pollute the bus grid and cause the quality of power supply to decline; (3) When a grounding short circuit fault occurs on the load side, the traditional transformer cannot effectively isolate the fault, resulting in the expansion of the fault range; (4 ) requires a special relay protection device for protection. When the transformer core is saturated, it is easy to generate a large excitation inrush current, which brings harm to the power system; (6) The function is single, without functions such as voltage regulation, power factor correction and power flow control, which cannot meet the needs of smart grid construction

[0005] Electronic power transformers in the prior art generally include cascaded H-bridge rectifiers, isolation stages and inverters, and a small number of modular multi-level rectifiers are used, but they are limited to three-phase three-leg circuit structures and cannot be applied to single phase system

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