Electric vehicle charging station power supply system based on solid-state transformer

Abstract

The invention discloses an electric vehicle charging station power supply system based on a solid-state transformer. The system comprises an alternating-current / direct-current solid-state transformer, a direct-current power distribution cabinet, a direct-current charging cabinet, a direct-current charging pile, an inverter, an alternating-current charging cabinet, an alternating-current charging pile and other equipment. In the system, a power supply line, where a 400V direct current as a main portion, is set and is connected to a power grid through the alternating-current / direct-current solid-state transformer. During an electric vehicle charging process, an influence of a generated harmonic wave on power-grid electric energy quality is effectively restrained and a power factor is effectively increased so that energy saving and consumption reduction are realized and structures of a power supply system and charging equipment are simplified. Based on that, because of an application of an energy storage unit, a power grid load can be effectively regulated and controlled, which is good for power supply stabilization; and because that the alternating-current / direct-current solid-state transformer and the power supply line where the 400V direct current as the main portion are arranged, access of renewable energy sources of solar energy, wind energy and the like can be convenient.

Description

technical field [0001] The invention relates to the technical field of electric vehicle charging station power supply, in particular to a solid-state transformer-based electric vehicle charging station power supply system. Background technique [0002] At present, the typical electric vehicle charging station power supply system is as follows: figure 1 shown. The transformer 102 is connected to the power grid 101 to obtain 380V three-phase alternating current to supply power for the charging load of the electric vehicle charging station and equipment such as communication and lighting. The low-voltage switch cabinet 103 is connected to multiple AC charging piles 106 and multiple DC charging cabinets 107 to provide electric energy for charging loads. The AC charging pile 106 can provide 220V AC charging voltage for the electric vehicle for AC slow charging. The DC charging cabinet 107 further distributes electric energy to multiple DC charging piles 108. The DC charging pi...

AI Technical Summary

Problems solved by technology

[0004] (1) Since the charging of electric vehicles is a nonlinear load, harmonic current will be injected into the grid at the same time during the charging process, resulting in a decrease in the power quality of the grid, an increase in grid loss, and normal capacity occupation of power transmission and transformation equipment

When the traditional power transformer is used to connect to the power grid, the generated harmonics cannot be isolated and controlled. Therefore, a harmonic control module needs to be added to the charging equipment, and reactive power compensation equipment needs to be added to the power supply line to improve access to the power grid. Node power factor

However, according to the existing power supply system structure, each charging pile needs to be equipped with a harmonic control module. If a better harmonic control effect is to be achieved, the cost of the corresponding charging pile will increase significantly

In addition, in order to achieve a better free compensation effect to stabilize the node voltage, the compensation capacity of the reactive power compensation equipment also needs to be changed according to the load conditions, and the corresponding compensation equipment is complicated to control, and the equipment cost also increases accordingly

[0005] (2) The charging of electric vehicles, especially DC fast charging, will bring a lot of changes to the grid load, which is not conducive to maintaining stable power supply

[0006] (3) The existing power supply system is inconvenient to access renewable energy

Due to the inherent characteristics of time-varying, intermittent, and unpredictable renewable energy such as solar energy and wind energy, traditional power transformers used in existing power supply systems do not have voltage adjustment functions, and it is difficult to control the voltage of nodes connected to the grid to maintain stability

In addition, due to the use of 380V three-phase AC power supply lines, when solar and wind energy are connected, inverters are required to invert DC power into AC power to be incorporated into the power supply lines. The control of the conversion, storage and utilization of renewable energy will would be too complex for practical application

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