Efficient electric vehicle direct-current fast charge system

Abstract

The invention relates to an efficient electric vehicle direct-current fast charge system, and belongs to the field of new energy vehicles. The efficient electric vehicle direct-current fast charge system comprises a pile of a direct-current fast charge pile, output direct-current bus, an AC / DC converter, a DC / DC converter, a capacitor, a power distribution transformer and a power grid. One end ofthe power distribution transformer is connected to the power grid, the other end of the power distribution transformer is connected to an AC end of the AC / DC converter, and a DC end of the AC / DC converter is connected with the output direct-current bus of the electric vehicle direct-current fast charge pile; one end of the DC / DC converter is connected with the capacitor, the other end of the DC / DCconverter is connected with the output direct-current bus of the direct-current fast charge pile, and low-order harmonic waves in AC / DC direct-current output currents can be absorbed by the other endof the DC / DC converter under the control. The efficient electric vehicle direct-current fast charge system has the advantages that secondary-side winding transformation ratios of the power distribution transformer are designs, accordingly, three-phase alternating-current-side voltages can be reduced, and requirements of minimum values of voltage ranges of battery packs of mainstream electric vehicles can be met by AC / DC direct-current output; only single-stage AC / DC power conversion is required, only harmonic currents are absorbed by the low-power DC / DC converter, the problem that all chargepower is transmitted through extra DC / DC converters can be solved, accordingly, the cost can be saved, and the efficiency of the efficient electric vehicle direct-current fast charge system can be improved.

Description

technical field [0001] The invention belongs to the field of new energy vehicles and relates to a high-efficiency DC fast charging system for electric vehicles. Background technique [0002] In recent years, the electric vehicle market has expanded rapidly, and various countries are also actively promoting the development of electric vehicles. At present, many European countries have launched and formulated a timetable for banning the sale of fuel vehicles, and my country has issued relevant policies. However, the construction of electric vehicle charging infrastructure is relatively lagging behind, and the charging time of electric vehicles is much longer than the refueling time of traditional fuel vehicles, resulting in poor user experience of electric vehicles, which cannot replace fuel vehicles in the short term. Among the two main types of charging methods, AC charging piles are usually called slow charging piles, which mainly provide plugging and metering of single-ph...

AI Technical Summary

Problems solved by technology

[0005] The first is the problem of low-order harmonics of the charging current: on the one hand, the voltage on the grid side contains major harmonics such as 5th, 7th, 11th, and 13th, which cause deviations in the sine of the voltage; on the other hand, fast charging piles and all The load (or grid-connected) current of the AC grid side of the electrical equipment (load or grid-connected) must meet the requirements of the charging standard, that is, to maintain a good sine degree of the current on the grid side of the equipment; so the power obtained by the product of the voltage and current contains The low-order harmonics are eliminated; this low-order harmonic power can only go to the DC side in the single-stage ACDC conversion, and the voltage on the DC side is relatively stable (for example, the bus voltage of the DC charging pile is determined by the connected electric motor Determined by the voltage of the car battery pack), the charging current on the DC side will have low harmonics, thus violating the charging standard

Therefore, a single-stage AC / DC with an input voltage of three-phase 380V cannot meet the typical voltage range of electric vehicle charging

[0007] The third is the problem of electrical isolation

Obviously, this isolation link will cause a greater loss of efficiency

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