Two-stage type AC-DC converter and control method thereof

Abstract

The invention discloses a two-stage type AC-DC converter and a control method thereof and belongs to the power electronic converter technical field. The two-stage AC-DC converter is composed of a double-output PFC converter and two DCX circuits; the dual-output PFC converter provides voltage-constant high-voltage direct current output and voltage-variable low-voltage direct current output; the high-voltage direct current output and the low-voltage direct current output are respectively adopted as the inputs of the two DCX circuits; and the outputs of the two DCX circuits are connected in series and are connected with a load. According to the two-stage type AC-DC converter and the control method thereof of the invention, the voltage-variable low-voltage direct current output of the double-output PFC converter is utilized to directly realize wide-range regulation of the voltage of the load side, and therefore, the power loss of the PFC converter can be decreased, and the high-efficiency DCX circuits can be adopted at the later stage, and overall efficiency can be improved significantly. The two-stage type AC-DC converter and the control method thereof are especially suitable for AC-DC conversion conditions where load voltage varies substantially and have a high application value and a bright application prospect in fields such as the electric vehicle charging and energy storage field.

Description

technical field [0001] The invention relates to a two-stage AC-DC converter and a control method thereof, belonging to the technical field of power electronic converters, in particular to the technical field of AC-DC electric energy conversion. Background technique [0002] With the wide application of power electronic devices, the harmonic current in the power grid is getting bigger and bigger, which has brought a series of hazards to the power grid itself and other electrical equipment, such as relay protection and automatic device malfunctions, instrumentation malfunctions, etc. Measurement; harmonics can also cause additional loss, resulting in transformer heating, cable aging, etc. To this end, governments and international organizations have formulated mandatory standards, such as IEC 61000-302 Class D, to limit the input current harmonics and power factor of the converter. The two-stage AC-DC converter has been widely used in switching power supply, uninterrupted pow...

AI Technical Summary

Problems solved by technology

Although the traditional two-stage AC-DC converter is widely used in the industry, it also has the following disadvantages: (1) Due to the high voltage level of the intermediate DC bus, the PFC converter in the front stage and the DC-DC converter in the rear stage The power devices will bear high voltage stress, and the switching loss of the converter is also large due to the large voltage change at both ends of the switching device during the switching action.

(2) The AC pulsating power input by the converter will be converted in two stages by the PFC converter and the DC-DC converter, which will increase the energy consumption of the system and reduce the overall efficiency of the converter

(3) In the application where the load voltage varies in a wide range, the post-stage DC-DC converter must use a converter with a wide gain, and the design of this type of converter is usually difficult and it is difficult to achieve the same efficiency in the entire gain range optimization

Literature "P. Das, M. Pahlevaninezhad, G. Moschopoulos. Analysis and Design of a New AC-DC Single-StageFull-Bridge PWM Converter With Two Controllers [J]. IEEE Transactions on Industrial Electronics2013, 60(11): 4930- 4946."A full-bridge converter is used to realize a single-stage PFC converter, and only one-stage converter is used to realize the functions of PFC and output voltage regulation at the same time, but the single-stage PFC converter either sacrifices the power factor adjustment capability, or greatly increases the number of devices voltage stress, the final effect is not much improved compared to the two-stage PFC converter

The above solution still uses a unified processing method for the pulsating power input by the converter, but due to the large-scale periodic fluctuation of the input AC voltage, the unified processing method cannot achieve power optimization for the entire input voltage range

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