Alternating current charging structure and charging system of electric automobile

Abstract

The utility model provides an alternating current charging structure and a charging system of an electric vehicle. The alternating current charging structure comprises a direct current input module; the direct-current power distribution module is connected with the direct-current input module and receives the direct-current voltage of the direct-current input module; and the step-down inversion module is connected with the direct-current power distribution module and is used for carrying out step-down and inversion processing on the direct-current voltage and outputting alternating-current voltage, and the alternating-current voltage is used for charging an electric vehicle after an alternating-current charging pile takes power. According to the alternating current charging scheme provided by the invention, the cable laying cost is effectively reduced, and the total manufacturing cost of electrical equipment is further reduced.

Description

Technical Field

[0001] This application belongs to the technical field of charging design, and relates to a charging structure, in particular to an AC charging structure and a charging system for electric vehicles. Background Art

[0002] In today's society, with the popularization and promotion of electric vehicles, charging piles have become one of the indispensable facilities in cities. However, there are still some problems to be solved with the slow charging piles commonly used on the market. The working architecture of most AC slow charging piles on the market is as follows: A transformer is connected to a 10KV switch cabinet, and its output is 380V alternating current, which is then connected to a power distribution cabinet. Then, any one of the three phases is randomly pulled from the power distribution cabinet to the charging pile to supply power to the charging pile.

[0003] The above method has many problems and limitations. First of all, in real life, the parking spaces in many parking lots are far from the 380V power distribution cabinet, and the 220V AC voltage is too low. This results in that when using a cable with a smaller cross-sectional area to connect the charging pile, due to the larger resistance of the cable with a small cross-sectional area, its voltage drop and loss are also large, affecting the charging efficiency. Moreover, due to the constant power load characteristic of the slow charging pile, the voltage drop at the end of the cable will also cause the current to rise further, thus posing a fire hazard. On the other hand, if a cable with a larger cross-sectional area is used to reduce the voltage drop and loss, the cost of the cable will increase significantly. Summary of the Invention

[0004] This application provides an AC charging structure and a charging system for electric vehicles, which are used to solve the problem of how to supply power to the charging pile over a long distance with a low-cost cable.

[0005] In a first aspect, this application provides an AC charging structure for electric vehicles, and the AC charging structure includes: a DC input module; a DC power distribution module connected to the DC input module and receiving the DC voltage of the DC input module; a buck-inverting module connected to the DC power distribution module, which performs buck and inversion processing on the DC voltage and outputs an AC voltage, and the AC voltage is used for the AC charging pile to draw power and charge the electric vehicle.

[0006] In an implementation manner of the first aspect, the DC input module includes a three-phase input power supply and a transformer rectifier; the three-phase input power supply is connected to the transformer rectifier; the three-phase input power supply inputs the power supply to the transformer rectifier, and after the transformer rectifier performs voltage transformation and rectification processing on the power supply, it outputs the DC voltage.

[0007] In an implementation of the first aspect, the step-down rectifier includes a phase-shifting transformer and a rectifier bridge; after the phase-shifting transformer processes the power supply voltage, it is transmitted to the rectifier bridge for rectification processing, and the rectifier bridge outputs the DC voltage.

[0008] In an implementation of the first aspect, the DC power distribution module includes a star power distribution structure; the star power distribution structure distributes the DC voltage to the first branch, the second branch, and the third branch respectively.

[0009] In an implementation of the first aspect, the step-down inverter module includes a first step-down inverter power supply, a second step-down inverter power supply, and a third step-down inverter power supply; the first step-down inverter power supply accesses the DC voltage transmitted by the first branch and outputs a first AC voltage; the second step-down inverter power supply accesses the DC voltage transmitted by the second branch and outputs a second AC voltage; the third step-down inverter power supply accesses the DC voltage transmitted by the third branch and outputs a third AC voltage.

[0010] In a second aspect, the present application provides an AC charging system, and the AC charging system includes: the AC charging structure of the electric vehicle.

[0011] In an implementation of the second aspect, the AC charging system further includes: an AC charging pile, the AC charging pile is connected to the AC charging structure, and the AC charging pile takes power from the output AC voltage to charge the electric vehicle.

[0012] In an implementation of the second aspect, the DC power distribution module of the AC charging structure includes a star power distribution structure; the star power distribution structure distributes the DC voltage to the first branch, the second branch, and the third branch respectively.

[0013] In an implementation of the second aspect, the step-down inverter module of the AC charging structure includes a first step-down inverter power supply, a second step-down inverter power supply, and a third step-down inverter power supply; the first step-down inverter power supply accesses the DC voltage transmitted by the first branch and outputs a first AC voltage; the second step-down inverter power supply accesses the DC voltage transmitted by the second branch and outputs a second AC voltage; the third step-down inverter power supply accesses the DC voltage transmitted by the third branch and outputs a third AC voltage.

[0014] In an implementation of the second aspect, the AC charging pile includes a first AC charging pile, a second AC charging pile, and a third AC charging pile; the first AC charging pile accesses the first AC voltage transmitted by the first step-down inverter power supply; the second AC charging pile accesses the second AC voltage transmitted by the second step-down inverter power supply; the third AC charging pile accesses the third AC voltage transmitted by the third step-down inverter power supply.

[0015] As described above, the AC charging structure and charging system of the electric vehicle according to the present application have the following beneficial effects:

[0016] The present application applies high-voltage DC power supply and step-down inverter technology, solves the limitations of the traditional charging system. Through 800V high-voltage DC power supply, the charging distance of low-power AC charging piles is greatly improved. At the same time, the cable cost of the charging pile project is reduced, and the charging efficiency and safety in the charging system are improved. Under the voltage drop specified by the national standard (the voltage deviation of 220V specified in "GB / T 12325-2008" is -10% - 7% of the rated voltage value, that is, the theoretical maximum voltage drop is 10%, and generally in actual projects, the voltage drop is often designed to about 3%), the cross-sectional area of the laid cable required is greatly reduced, and the cable cost can be reduced to about 10% of the cable required for 220V AC power supply. Even if a centralized multi-pulse transformer rectifier and an inverter power supply on each charging pile side are added, in a charging station with a large number of charging piles and a long power supply distance, the present application can still reduce the total cost of electrical equipment to less than 50% of that of 220V AC power supply. Brief Description of the Drawings

[0017] Figure 1 It shows a schematic structural connection diagram of the AC charging structure of the electric vehicle according to the embodiment of the present application.

[0018] Figure 2 It shows a circuit structure diagram of the DC input module of the AC charging structure of the electric vehicle according to the embodiment of the present application.

[0019] Figure 3 It shows a circuit structure diagram of the AC charging structure of the electric vehicle according to the embodiment of the present application.

[0020] Figure 4 It shows a step-down circuit structure diagram of the AC charging structure of the electric vehicle according to the embodiment of the present application.

[0021] Figure 5 It shows an inverter circuit structure diagram of the AC charging structure of the electric vehicle according to the embodiment of the present application.

[0022] Figure 6 It shows a schematic structural connection diagram of the AC charging system according to the embodiment of the present application.

[0023] Figure 7 It shows a circuit structure diagram of the AC charging system of the electric vehicle according to the embodiment of the present application.

[0024] Description of Component Labels

[0025] 1 AC charging structure of the electric vehicle

[0026] 11 DC input module

[0027] 12 DC power distribution module

[0028] 13 Step-down and inversion module

[0029] 2 AC charging pile Specific implementation manners

[0030] The following uses specific specific examples to illustrate the implementation manners of the present application. Those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in this specification. The present application can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0031] It should be noted that the drawings provided in the following embodiments only illustrate the basic concept of the present application in a schematic manner. Therefore, only the components related to the present application are shown in the drawings, rather than being drawn according to the number, shape, and size of the components in actual implementation. The types, quantities, and proportions of the components in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0032] Next, the technical solutions in the embodiments of the present application will be described in detail with reference to the accompanying drawings in the embodiments of the present application.

[0033] Please refer to Figure 1 , which shows a schematic structural connection diagram of the AC charging structure of an electric vehicle described in the embodiments of the present application. As Figure 1 shown, this embodiment provides an AC charging structure 1 for an electric vehicle, which specifically includes: a DC input module 11, a DC power distribution module 12, and a step-down and inversion module 13.

[0034] The DC power distribution module 12 is connected to the DC input module 11 and receives the DC voltage of the DC input module 11.

[0035] The step-down and inversion module 13 is connected to the DC power distribution module 12, performs step-down and inversion processing on the DC voltage, and outputs an AC voltage, and the AC voltage is used for the AC charging pile to draw power and charge the electric vehicle.

[0036] In one embodiment, the DC input module includes a three-phase input power supply and a transformer rectifier; the three-phase input power supply is connected to the transformer rectifier.

[0037] The three-phase input power supply inputs the power supply into the step-down rectifier. After the step-down rectifier performs step-down and rectification processing on the power supply, the DC voltage is output.

[0038] Please refer to Figure 2 , which shows the circuit structure diagram of the DC input module of the AC charging structure of the electric vehicle described in the embodiment of the present application. As Figure 2 shown, the DC input module includes a three-phase input power supply part and a step-down rectifier part; the three-phase input power supply part is connected to the step-down rectifier part. The three-phase input power supply inputs the 10 kV power supply into the step-down rectifier part in three paths. After the step-down rectifier part performs step-down and rectification processing on the power supply, the DC voltage is output.

[0039] As Figure 2 shown, the step-down rectifier includes a phase-shifting transformer and three rectifier bridges.

[0040] The phase-shifting transformer performs step-down processing on the 10 kV power supply and then transmits it to the rectifier bridge for rectification processing. The three rectifier bridges merge to output the DC voltage.

[0041] In practical applications, the step-down rectifier includes a multi-pulse step-down rectifier connected to a 10 kV switchgear, which converts the input voltage from 10 kV to DC 800 V and uses this as the DC voltage for power supply to the installation location of the charging pile. Currently, the commonly used power supply method is to connect a transformer to a 10 kV switchgear to output 380 V alternating current, and then connect it to a power distribution cabinet. This application uses a DC voltage of 800 V, which is higher than 380 V alternating current. Thus, the overall system cost is reduced by increasing the power supply voltage.

[0042] In practical applications, if there is no condition to connect to a 10 kV power supply, a multi-pulse step-down rectifier connected to a 380 V AC voltage can also be used, and its output is still 800 V DC voltage. (Connecting to a 10 kV power supply requires pulling a cable from a 10 kV high-voltage cabinet to the transformer, while connecting to a 380 V power supply requires pulling a cable from a 380 V low-voltage cabinet to the transformer. At the same time, the rectifier transformer also needs to be changed from a step-down transformer to a step-up transformer, and the turns ratio changes. There is no significant difference in their working principles. The main difference in engineering is that if 10 kV is used as the input, a conventional 10 kV / 380 V transformer is not required, so one level of voltage conversion is reduced; if 380 V is used as the input, a conventional 10 kV / 380 V transformer is used as one level of voltage conversion, and power loss will still occur. For new projects, it is recommended to use a 10 kV direct input as much as possible. However, in actual application scenarios, it is possible that there is already a 10 kV / 380 V transformer on-site with sufficient capacity, and it is difficult to install an additional 10 kV device. In this case, a step-down rectifier with 380 V as the input needs to be used.)

[0043] Please refer to Figure 3 , which shows the circuit structure diagram of the AC charging structure of the electric vehicle described in the embodiment of the present application. As Figure 3 shown, in one embodiment, the DC power distribution module includes a star-shaped power distribution structure.

[0044] The star-shaped power distribution structure distributes the DC voltage to the first branch, the second branch, and the third branch respectively.

[0045] As Figure 3 shown, the 800 V DC voltage is output to the step-down inverter module 13 through three branches after passing through the power distribution cabinet. Specifically, the first branch is the left path output by the power distribution cabinet, the second branch is the middle path output by the power distribution cabinet, and the third branch is the right path output by the power distribution cabinet.

[0046] In one embodiment, the step-down inverter module includes a first step-down inverter power supply, a second step-down inverter power supply, and a third step-down inverter power supply.

[0047] The first step-down inverter power supply accesses the DC voltage transmitted by the first branch and outputs a first AC voltage; the second step-down inverter power supply accesses the DC voltage transmitted by the second branch and outputs a second AC voltage; the third step-down inverter power supply accesses the DC voltage transmitted by the third branch and outputs a third AC voltage.

[0048] Specifically, the step-down inverter power supply includes a step-down circuit part and an inverter circuit part. The step-down inverter power supply solves the interface problem between the 800V system power supply and the 220V AC supply voltage required by a conventional slow charging pile. Overall, the technical solution of this application innovatively applies high-voltage DC power supply and step-down inverter technology, solves the limitations of traditional charging systems, improves charging efficiency and safety, and has important application prospects and market potential.

[0049] Please refer to Figure 4 , which shows the step-down circuit structure diagram of the AC charging structure of the electric vehicle described in the embodiment of this application. As Figure 4 shown, the step-down circuit is a BUCK circuit, Vin represents the 800V DC voltage, and the output voltage is regulated by controlling the on / off of the switching tube T to achieve the step-down of the 800V DC voltage to 220V DC voltage.

[0050] Please refer to Figure 5 , which shows the inverter circuit structure diagram of the AC charging structure of the electric vehicle described in the embodiment of this application. As Figure 5 shown, the inverter circuit is a full-bridge inverter circuit composed of four MOS tubes (Q1, Q2, Q3, and Q4), and the input direct current is Figure 4 the 220V DC voltage output by the step-down circuit of

[0051] This application takes advantage of the fact that high voltage and direct current have no power factor. At a reasonable voltage drop and loss level, the cross-sectional area of the cable is significantly reduced (most charging piles on the market can be approximately regarded as constant power loads. The cable current is I = P / U in the DC case and I = P / Ucosα in the AC case, where 0 < α < 1. Here, I is the current inside the cable, P is the power, α is the phase angle, and U is the cable transmission voltage. The larger the voltage, the smaller the current inside the cable and the smaller the cross-sectional area used. At the same time, the voltage drop ΔU = 2IR and the loss ΔP = I²R, where R is the cable resistance. Then, in the case of using the same cable, the smaller the current, the lower the voltage drop and the lower the loss), thereby reducing the construction cost of charging equipment. Even if the parking lot is far from the power distribution cabinet, it can provide high-efficiency charging services for electric vehicles at low cost.

[0052] Please refer to Figure 6 , which shows the schematic diagram of the structural connection of the AC charging system described in the embodiment of this application. As Figure 6 shown, the embodiment of this application provides an AC charging system, and the AC charging system includes: the AC charging structure of the above-mentioned electric vehicle.

[0053] The AC charging structure 1 of the electric vehicle specifically includes: a DC input module 11, a DC power distribution module 12, and a buck-inverter module 13. The DC power distribution module 12 is connected to the DC input module 11 and receives the DC voltage of the DC input module 11. The buck-inverter module 13 is connected to the DC power distribution module 12, steps down and inverts the DC voltage, and outputs an AC voltage, which is used to charge the electric vehicle after taking power from the AC charging pile.

[0054] In one embodiment, the DC input module includes a three-phase input power supply and a transformer rectifier; the three-phase input power supply is connected to the transformer rectifier. The three-phase input power supply inputs the power supply to the transformer rectifier, and after the transformer rectifier steps down and rectifies the power supply, the DC voltage is output.

[0055] As Figure 2 shown, the DC input module includes a three-phase input power supply part and a transformer rectifier part; the three-phase input power supply part is connected to the transformer rectifier part. The three-phase input power supply inputs the 10 kV power supply in three paths to the transformer rectifier part, and after the transformer rectifier part steps down and rectifies the power supply, the DC voltage is output. As Figure 2 shown, the transformer rectifier includes a phase-shifting transformer and three rectifier bridges. After the phase-shifting transformer steps down the 10 kV power supply, it is transmitted to the rectifier bridge for rectification, and the DC voltage is output by combining the three rectifier bridges.

[0056] As Figure 3 shown, in one embodiment, the DC power distribution module includes a star-shaped power distribution structure. The star-shaped power distribution structure distributes the DC voltage to the first branch, the second branch, and the third branch respectively. As Figure 3 shown, the 800 V DC voltage is output to the buck-inverter module 13 in three branches after passing through the power distribution cabinet. Specifically, the first branch is the left path output by the power distribution cabinet, the second branch is the middle path output by the power distribution cabinet, and the third branch is the right path output by the power distribution cabinet.

[0057] Specifically, the buck-inverter power supply includes a buck circuit part and an inverter circuit part. As Figure 4 shown, the buck circuit is a BUCK circuit, Vin represents the 800 V DC voltage, and the output voltage is adjusted by controlling the on-off of the switching tube T to step down the 800 V DC voltage to 220 DC voltage. As Figure 5 shown, the inverter circuit is a full-bridge inverter circuit composed of four MOS tubes (Q1, Q2, Q3, and Q4), and the input direct current is Figure 4 the 220 DC voltage output by the buck circuit.

[0058] As Figure 6 shown, the AC charging system further includes: an AC charging pile 2, which is connected to the AC charging structure 1 and charges an electric vehicle after taking power from the output AC voltage.

[0059] Please refer to Figure 7 , which shows the circuit structure diagram of the AC charging system of the electric vehicle described in the embodiment of the present application. As Figure 7 shown, the DC power distribution cabinet part of the AC charging structure includes a star-shaped power distribution structure.

[0060] The star-shaped power distribution structure distributes the DC voltage to the first branch, the second branch, and the third branch respectively. The first branch, the second branch, and the third branch are respectively connected to the load part of the AC charging system.

[0061] As Figure 7 shown, the load part of the AC charging system includes a step-down inverter power supply and a low-power AC charging pile. In order to match the input voltage corresponding to the low-power AC charging pile, a step-down inverter power supply is added on the pile side, so the voltage change sequence is AC-DC-AC.

[0062] The step-down inverter module of the AC charging structure includes a first step-down inverter power supply, a second step-down inverter power supply, and a third step-down inverter power supply; the first step-down inverter power supply accesses the DC voltage transmitted by the first branch and outputs a first AC voltage; the second step-down inverter power supply accesses the DC voltage transmitted by the second branch and outputs a second AC voltage; the third step-down inverter power supply accesses the DC voltage transmitted by the third branch and outputs a third AC voltage.

[0063] As Figure 7 shown, the AC charging pile is a low-power AC charging pile, such as a 7kW AC charging pile, and includes a first AC charging pile, a second AC charging pile, and a third AC charging pile.

[0064] The first AC charging pile accesses the first AC voltage transmitted by the first step-down inverter power supply; the second AC charging pile accesses the second AC voltage transmitted by the second step-down inverter power supply; the third AC charging pile accesses the third AC voltage transmitted by the third step-down inverter power supply.

[0065] Thus, the present application solves the problem that most low-power AC charging piles (7KW) on the market cannot use a reasonable and economical method for long-distance charging due to the low amplitude of their input voltage (220VAC), and focuses on the power supply cable in terms of cost savings. The purpose of the present application is to increase the charging distance of low-power charging piles through a high-amplitude DC voltage, greatly reducing the cost of the cable in the charging project and improving the safety of the project.

[0066] An embodiment of the present utility model is a public charging station system for the underground parking lot of an old community. This community has 1,912 property-owned parking spaces and 459 non-property-owned parking spaces, and the transformer capacity is tight. Due to the large number of private cars in the community and the relatively large proportion of new energy vehicles, it is planned to install more 7kW AC slow charging piles. It is planned to install 50 7KW AC slow charging piles. Among them, the straight-line distance from the charging pile closest to the distribution cabinet is about 100m, and the straight-line distance from the charging pile farthest from the distribution cabinet is about 180m. The slow charging piles are arranged in 3 rows in sequence.

[0067] The original plan was to build a new AC box transformer in the original power distribution room of the community to supply power to the AC slow charging piles. However, there are relatively few original distribution cabinets in the community, and most of them are arranged within 50m around the power distribution room to save costs. If an AC power distribution system is used to supply normal power to the newly built charging piles, the number of distribution cabinets needs to be increased in each area, and the construction cost and cable cost will increase greatly, exceeding the original budget. Therefore, the DC 800V power supply scheme of this application is adopted for replacement.

[0068] Install a DC box transformer (250KVA) with sufficient capacity in the power distribution room where an AC box transformer was originally planned to be installed. The input voltage is three-phase 10KV, and the output voltage from the rectifier cabinet is DC 800V; replace the originally planned ordinary 7KW slow charging piles with slow charging piles with built-in step-down inverter devices. Build distribution cabinets within 50 meters outside the power distribution room, and pull cables from the distribution cabinets to the charging piles. In this embodiment, the total cost of using the 800V DC power supply scheme is about 40% less than the original AC scheme. Among them, the cable cost from the distribution cabinet to the charging pile for the 800V DC power supply is about 1 / 8 of that for the 220V AC power supply. Thus, it can be seen that although a step-down inverter device needs to be installed inside each AC slow charging pile under the 800V DC power supply scheme, it solves the problems of the too large area of the underground parking lot in the community, too many parking spaces, and the long distance from many charging piles to the distribution cabinet. At the same time, the cost of installing the step-down inverter power supply is much less than the cost of building redundant distribution cabinets and using cables with more lines and larger cross-sectional areas.

[0069] In several embodiments provided in this application, it should be understood that the disclosed structure or system can be implemented in other ways. For example, the structural embodiments described above are only illustrative. For example, the division of modules / units is only a logical function division. In actual implementation, there can be other division methods. For example, multiple modules or units can be combined or integrated into another system, or some features can be ignored or not executed. Another point, the displayed or discussed coupling or direct coupling or communication connection with each other can be through some interfaces, and the indirect coupling or communication connection of devices or modules or units can be in an electrical, mechanical or other forms.

[0070] The module / unit described as a separate component may or may not be physically separated. The component shown as a module / unit may or may not be a physical module, that is, it may be located in one place or distributed across multiple network units. Some or all of the modules / units can be selected according to actual needs to achieve the purpose of the embodiments of the present application. For example, in various embodiments of the present application, each functional module / unit can be integrated in a processing module, or each module / unit can exist physically alone, or two or more modules / units can be integrated in one module / unit.

[0071] The above embodiments are only illustrative of the principles and effects of the present application, and are not used to limit the present application. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed in the present application should still be covered by the claims of the present application.

Claims

1. An AC charging structure for an electric vehicle, characterized in that: The AC charging structure comprises: DC input module; A DC power distribution module, connected to the DC input module, and receiving a DC voltage from the DC input module; The step-down inverter module is connected to the DC power distribution module, steps down and inverts the DC voltage, and outputs an AC voltage. The AC voltage is used to charge the electric vehicle after the AC charging pile draws power.

2. The AC charging structure according to claim 1, characterized in that: The DC input module includes a three-phase input power supply and a transformer rectifier; the three-phase input power supply is connected to the transformer rectifier; The three-phase input power source inputs the power supply into the transformer-rectifier, and the transformer-rectifier outputs the DC voltage after transforming and rectifying the power supply.

3. The AC charging structure according to claim 2, characterized in that: The transformer rectifier includes a phase-shifting transformer and a rectifier bridge; The phase-shifting transformer transforms the power supply and transmits the transformed power to the rectifier bridge for rectification, and the rectifier bridge outputs the DC voltage.

4. The AC charging structure according to claim 1, characterized in that: The DC power distribution module includes a star-type power distribution structure; The star-type power distribution structure distributes the DC voltage to the first branch, the second branch and the third branch respectively.

5. The AC charging structure according to claim 4, characterized in that: The step-down inverter module includes a first step-down inverter power supply, a second step-down inverter power supply and a third step-down inverter power supply; The first step-down inverter power supply is connected to the DC voltage transmitted by the first branch and outputs a first AC voltage; the second step-down inverter power supply is connected to the DC voltage transmitted by the second branch and outputs a second AC voltage; the third step-down inverter power supply is connected to the DC voltage transmitted by the third branch and outputs a third AC voltage.

6. An AC charging system, characterized in that: The AC charging system comprises: the AC charging structure for an electric vehicle as described in any one of claims 1-5.

7. The AC charging system according to claim 6, characterized in that: The AC charging system further includes: an AC charging pile, which is connected to the AC charging structure, and the AC charging pile charges the electric vehicle after taking power from the output AC voltage.

8. The AC charging system according to claim 7, characterized in that: The DC power distribution module of the AC charging structure includes a star-shaped power distribution structure; The star-type power distribution structure distributes the DC voltage to the first branch, the second branch and the third branch respectively.

9. The AC charging system according to claim 8, characterized in that: The buck inverter module of the AC charging structure includes a first buck inverter power supply, a second buck inverter power supply and a third buck inverter power supply; The first step-down inverter power supply is connected to the DC voltage transmitted by the first branch and outputs a first AC voltage; the second step-down inverter power supply is connected to the DC voltage transmitted by the second branch and outputs a second AC voltage; the third step-down inverter power supply is connected to the DC voltage transmitted by the third branch and outputs a third AC voltage.

10. The AC charging system according to claim 9, characterized in that: The AC charging pile includes a first AC charging pile, a second AC charging pile and a third AC charging pile; The first AC charging pile is connected to the first AC voltage transmitted by the first step-down inverter power supply; the second AC charging pile is connected to the second AC voltage transmitted by the second step-down inverter power supply; and the third AC charging pile is connected to the third AC voltage transmitted by the third step-down inverter power supply.

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