Medium voltage ac bus direct hanging type ev charging station power distribution architecture and control method thereof

Abstract

The application discloses a medium-voltage AC bus direct-hanging type EV charging station power distribution architecture and a control method thereof, and relates to the technical field of power electronics. The application comprises a medium-voltage AC bus and a coordination controller. The medium-voltage AC bus is electrically cross-connected with three-phase cascade H-bridge units. Each phase cascade H-bridge unit is electrically connected with a plurality of three-active-bridge converter units. Each three-active-bridge converter unit performs bidirectional power transmission with two cascade H-bridge units, and the three-active-bridge converter unit is connected with an EV charging interface. The application can realize power conversion between three-phase medium-voltage AC and multiple low-voltage DC in an EV charging station powered by a three-phase medium-voltage AC bus. Compared with a traditional low-voltage power distribution architecture, the application can avoid using a high-power power frequency transformer, reduce the power conversion link, improve the power density and operation efficiency of the EV charging station power distribution system, and realize power balance between sub-modules under any power consumption condition, thereby improving the power distribution flexibility and reliability.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, specifically to a medium-voltage AC busbar-connected EV charging station power distribution architecture. Background Technology

[0002] The large-scale development of EVs has placed higher demands on charging infrastructure. Currently, most mainstream EV charging stations use low-voltage AC or low-voltage DC bus power distribution architectures, requiring multiple power conversion stages, resulting in low efficiency and high cost. A medium-voltage AC bus direct-connection power distribution architecture can reduce power conversion stages, lower system losses, and increase equipment power density. However, the existing medium-voltage AC bus direct-connection power distribution architecture has limitations in terms of power imbalance among multiple charging ports, restricting its application in EV charging stations. Therefore, this invention proposes a medium-voltage AC bus direct-connection EV charging station power distribution architecture and its control method. Summary of the Invention

[0003] The purpose of this invention is to provide a power distribution architecture and control method for a medium-voltage AC bus-connected EV charging station, which can overcome the shortcomings of existing medium-voltage AC bus-connected power distribution architectures that cannot solve the problem of unbalanced power distribution at charging ports.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a medium-voltage AC bus direct-connected EV charging station power distribution architecture, including a medium-voltage AC bus and a coordination controller. The medium-voltage AC bus is electrically cross-connected with three-phase cascaded H-bridge units. Each phase cascaded H-bridge unit is electrically connected to several three-phase active bridge converter units. The cascaded H-bridge units and the three-phase active bridge converter units perform bidirectional power transmission. The three-phase active bridge converter units are connected to EV charging interfaces. The coordination controller is connected to the cascaded H-bridge and the three-phase active bridge converters through sensor circuits.

[0005] Each phase of the three-phase cascaded H-bridge unit includes a filter inductor and a series sub-module structure connected to the filter inductor. The series sub-module structure is composed of N full-bridge sub-modules cascaded together.

[0006] The three-phase active bridge converter unit includes three full-bridge modules and a three-winding transformer. The AC side of the three full-bridge modules is connected to the three windings of the three-winding transformer, and the DC side of the three full-bridge modules is connected to the positive and negative terminals of the capacitors in the full-bridge sub-modules, respectively.

[0007] Furthermore, the three active bridge converter unit is configured as a dual transformer three active bridge converter, a three active half bridge converter, a dual transformer three active half bridge converter, or an isolated three-port resonant converter.

[0008] Furthermore, the full-bridge submodule includes four ports: a, b, c, and d. Ports a and b are the input and output ports of the full-bridge submodule, respectively. The full-bridge submodule is connected in series to the cascaded H-bridge unit through ports a and b.

[0009] Ports c and d are connected in parallel to the positive and negative terminals of the capacitor in the full-bridge submodule, respectively.

[0010] Furthermore, the positive and negative terminals of the capacitors of the three full-bridge modules in the three active bridge converter unit generate three DC interfaces, namely interface ①, interface ② and interface ③. Interface ① and interface ② are connected to the c and d ports of two adjacent full-bridge sub-modules, respectively, to build a power path between the full-bridge sub-modules; interface ③ is connected to the EV charging interface.

[0011] Furthermore, the three active bridge converters on each phase cascaded H-bridge unit are connected in parallel through interface ③ to achieve power balance between phases, and adjacent EV charging ports are connected in parallel to share current.

[0012] Furthermore, the power distribution architecture includes two operating modes: the grid-to-charging-station power supply mode and the charging-station-to-grid power supply mode.

[0013] According to a second aspect of the present invention, the present invention provides a control method for the power distribution architecture of a medium-voltage AC bus-connected EV charging station, which uses the power distribution architecture of the medium-voltage AC bus-connected EV charging station as described in any one of claims 1 to 6 to switch the operating mode of the charging station, as follows:

[0014] (71) Power grid to charging station power supply mode: The cascaded H-bridge unit controls the capacitor voltage of the full bridge sub-module. The interface ③ of the three active bridge converter unit adopts constant current and current sharing control strategy. Then, based on the output power of all interfaces ③, the power required to compensate the interface ② of each three active bridge converter unit to achieve power balance among the full bridge sub-modules in the cascaded H-bridge unit is calculated. Then, a constant power control strategy is adopted for interface ②.

[0015] (72) Charging station power supply mode to the grid: The cascaded H-bridge unit controls the capacitor voltage of the full bridge submodule. The three active bridge converter units calculate the output power reference of interface ③ and the compensation power between the full bridge submodules according to the instructions. Constant power control strategy is adopted for both interface ② and interface ③ to achieve power balance of the full bridge submodules in the cascaded H-bridge unit.

[0016] Furthermore, the output power reference of interface ③ and the compensation power between the full-bridge submodules are calculated, as follows:

[0017] (81) The output power of each full-bridge submodule is 1 / N of the total power on the medium-voltage AC bus side, and also 1 / N of the total power on the EV charging interface side, expressed as:

[0018] (1)

[0019] In the formula, P SM1 ~ P SMN These represent the output power of full-bridge submodules 1 through N, with the positive direction being the power flow from the full-bridge submodules to interface ① of the three active bridge converter. P EV1 ~ P EVN-1 These represent the output power of interface ③ of the three active bridge converters 1 to N-1, respectively. The positive direction is defined as the power flowing from interface ③ of the three active bridge converters to the EV charging interface.

[0020] (82) According to Kirchhoff's laws, the output power of the full-bridge submodule can also be calculated from the port power of the connected three active bridge converter units, as follows:

[0021] (2)

[0022] In the formula, P Ti1 Let represent the input power of the i-th three-active-bridge converter interface ①, taking the power flow from the full-bridge submodule to the three-active-bridge converter interface ① as the positive direction. P Ti2 This represents the output power of the i-th three-active-bridge converter interface ②, with the positive direction defined as power flowing from the three-active-bridge converter interface ② to the full-bridge submodule. P Ti3 This represents the output power of the i-th three-active-bridge converter interface ③, with the positive direction being the power flowing from the three-active-bridge interface ③ to the EV charging interface;

[0023] For each three-active-bridge converter unit, according to power conservation:

[0024] (3)

[0025] The power of interface ③ of the three active bridge converter unit is the power on the EV charging interface side, specifically expressed as follows:

[0026] (4)

[0027] Combining equations (2) to (4), the power of each three-active-bridge converter unit interface ② under steady state is calculated, which is the compensation power between the full-bridge submodules. The expression is:

[0028] (5)

[0029] In the formula, PISiref This represents the reference value for the compensation power of the i-th three-active bridge.

[0030] Furthermore, the three active bridge converter units adopt a single phase-shift modulation strategy, and the cascaded H-bridge units adopt a phase-shift modulation strategy.

[0031] Furthermore, the control method also includes fault-tolerant operation control. When a full-bridge submodule or a three-active-bridge converter power module fails, the faulty circuit part is bypassed through the corresponding full-bridge submodule and bypass switch, and the control strategy and modulation strategy of the DC power distribution device are reconstructed so that other power modules can operate normally. After the faulty power module has been repaired and pre-charged, it is reconnected to the DC power distribution device, and the DC power distribution device resumes normal operation.

[0032] The present invention has at least the following beneficial effects:

[0033] 1. Compared with the traditional low-voltage power distribution architecture, the present invention can reduce power conversion links and improve the power density and operating efficiency of the EV charging station power distribution system.

[0034] 2. Compared with the existing medium-voltage AC busbar direct-connection power distribution architecture, the present invention can achieve power balance between full-bridge sub-modules under any power consumption conditions, improving the flexibility and reliability of power distribution. At the same time, the present invention has a high degree of modularity, which facilitates production, manufacturing and maintenance.

[0035] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0036] Figure 1 This is a topology diagram of the power distribution architecture described in this invention;

[0037] Figure 2 This is a block diagram of the control strategy for the power distribution architecture described in this invention under G2V mode;

[0038] Figure 3 This is a block diagram of the control strategy of the power distribution architecture described in this invention under V2G mode;

[0039] Figure 4 This is a topology diagram of the power distribution architecture described in this invention, where the input side is single-phase AC power. Detailed Implementation

[0040] The technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0041] Example 1:

[0042] Please see Figures 1-4 This invention provides a technical solution: a medium-voltage AC busbar direct-connected EV charging station power distribution architecture, including a set of medium-voltage AC busbars, a three-phase cascaded H-bridge (CHB) unit converter, and 3... The system comprises (N-1) three-phase active bridge converter (TAB) units, N-1 EV charging interfaces, and a coordination controller. The medium-voltage AC bus is electrically connected to the three-phase cascaded H-bridge units. Each phase of the cascaded H-bridge unit is electrically connected to several three-phase active bridge converter units. The cascaded H-bridge units and the three-phase active bridge converter units perform bidirectional power transmission. The three-phase active bridge converter units are also electrically connected to the EV charging interfaces. The coordination controller is connected to the cascaded H-bridges and the three-phase active bridge converters through sensor circuits to collect electrical and temperature signals. Then, it is connected to the drive circuits of the cascaded H-bridges and the three-phase active bridge converters through optical fibers to perform drive control.

[0043] Each phase of the three-phase cascaded H-bridge unit includes a filter inductor and a series sub-module structure connected to the filter inductor. The series sub-module structure is composed of N full-bridge sub-modules cascaded together.

[0044] The three-phase active bridge converter unit includes three full-bridge modules and a three-winding transformer. The AC side of the three full-bridge modules is connected to the three windings of the three-winding transformer, and the DC side of the three full-bridge modules is connected to the positive and negative terminals of the capacitors in the full-bridge sub-modules, respectively.

[0045] By connecting the three-phase cascaded H-bridge unit to the medium-voltage AC bus, the medium-voltage AC bus voltage is converted into the low-voltage DC voltage of the sub-module capacitor, which can power the three active bridge converter units.

[0046] Regarding the technical solution of this embodiment, such as Figure 1 As shown, the full-bridge submodule includes four ports: a, b, c, and d. Ports a and b are the input and output ports of the full-bridge submodule, respectively. The full-bridge submodule is connected in series to the cascaded H-bridge unit through ports a and b.

[0047] Ports c and d are connected in parallel to the positive and negative terminals of the capacitor in the full-bridge submodule, respectively. The capacitor in the full-bridge submodule can decouple the power of CHB from the subsequent TAB, and at the same time provide power to TAB.

[0048] Regarding the technical solution of this embodiment, the three active bridge converter unit includes three full-bridge modules and a three-winding transformer. The AC sides of the three full-bridge modules are respectively connected to the three windings of the three-winding transformer, and power is transmitted through magnetic coupling. The DC sides of the three full-bridge modules are respectively connected to the positive and negative terminals of the full-bridge sub-module capacitors, that is, connected to the c and d ports. The positive and negative terminals of the sub-module capacitors of the three full-bridge modules lead out to generate three DC interfaces, namely interface ①, interface ②, and interface ③. i Interface ① connects to FBSM i On the CD end, interface ② connects to FBSM i+1 At the CD end, power paths are constructed between full-bridge submodules to achieve power balance among them. Interface ③ connects to the EV. i The charging port, including TAB i Let FBSM represent the i-th three-active-bridge converter unit. i Denotes the i-th full-bridge submodule, FBSM i+1 EV represents the (i+1)th full-bridge submodule. i Let i represent the i-th EV charging port, where i ranges from 1 to N-1.

[0049] It should be noted that the three active bridge converter unit can also be replaced by a fully isolated three-port DC / DC converter such as a dual transformer three active bridge converter, a three active half bridge converter, a dual transformer three active half bridge converter, or an isolated three-port resonant converter. The star power distribution architecture can also be changed to a delta power distribution architecture. This embodiment does not make specific limitations on this and can be selected according to the actual situation.

[0050] Furthermore, since multiple ports of the subsequent TAB are cross-cascaded on the capacitors of the preceding full-bridge submodule, it can also be called a switched-capacitor cross-cascaded triple active bridge (SC3TAB) power distribution architecture.

[0051] Furthermore, the three active bridge converter unit interfaces ③ at the corresponding positions of each phase cascaded H-bridge unit are connected in parallel for current sharing output to achieve power balance between phases; at the same time, multiple adjacent charging ports can be connected in parallel for output and a current sharing strategy can be adopted to expand the power output capability.

[0052] Traditional medium-voltage AC bus-connected EV charging station power distribution architectures are limited by the power imbalance operating boundary of CHB submodules, making them unable to cope with arbitrary EV unbalanced charging and discharging conditions. In this embodiment, the medium-voltage AC bus-connected EV charging station power distribution architecture uses TAB to create isolated power paths between the FBSMs of each CHB phase, enabling active FBSM power balancing and thus avoiding the constraints of the CHB unbalanced operating boundary, resulting in better power supply flexibility and reliability.

[0053] Furthermore, since CHB and TAB have bidirectional power transmission capabilities, this embodiment can realize two working modes: grid to vehicle (G2V) and charging station to grid (Vehicle to grid (V2G), thereby achieving flexible power interaction between EV and grid.

[0054] Figure 2 The control strategy block diagram for the power distribution architecture of a medium-voltage AC bus-connected EV charging station under G2V is shown. It consists of the CHB control strategy block diagram and the TAB control strategy block diagram. In G2V mode, the three-phase CHB adopts the dq decoupling control strategy.

[0055] In G2V mode, the TAB control strategy block diagram includes an output current loop and a power balance loop. Interface ③, where the TAB connects to the EV charging port, uses constant current control, referencing the output current. i EViref With actual output current i Evi The deviation is fed into the PI controller, generating a shift ratio between the full-bridge at interface ① and the full-bridge at interface ③. φ 13 TAB interface ② adopts constant power control, based on the output power of all TAB interfaces ③ P EV1 - P EV(N-1) Calculate the power reference of its interface ② P ISiref and subtract the actual value P ISi The deviation is fed into the PI controller to generate a shift ratio between the full-bridge submodule of interface ① and the full-bridge submodule of interface ②. φ 12 .

[0056] The power reference calculation method for all TAB interfaces ② is as follows: ignoring power loss, the output power of each FBSM is 1 / N of the total power on the medium-voltage side, and also 1 / N of the total power on the EV side. The expression is:

[0057] (1)

[0058] In the formula, in the formula, P SM1 ~ P SMN These represent the output power of full-bridge submodules 1 through N, with the positive direction being the power flow from the full-bridge submodules to interface ① of the three active bridge converter. P EV1 ~ P EVN-1 These represent the output power of interface ③ of the three active bridge converters 1 to N-1, with the positive direction being the power flowing from interface ③ of the three active bridge converters to the EV charging interface. Simultaneously, according to Kirchhoff's laws, the FBSM output power is also calculated from the power of the connected TAB port, expressed as:

[0059] (2)

[0060] In the formula, P Ti1 Let represent the input power of the i-th three-active-bridge converter interface ①, taking the power flow from the full-bridge submodule to the three-active-bridge converter interface ① as the positive direction. P Ti2 This represents the output power of the i-th three-active-bridge converter interface ②, with the positive direction defined as power flowing from the three-active-bridge converter interface ② to the full-bridge submodule. P Ti3 This represents the output power of the i-th three-active-bridge converter interface ③, with the positive direction being the power flowing from the three-active-bridge interface ③ to the EV charging interface;

[0061] For each tab, according to the law of power conservation:

[0062] (3)

[0063] Considering that the power of TAB interface ③ is the same as the EV-side power, we have:

[0064] (4)

[0065] Combining the three equations above, we can calculate the power of each TAB interface ② in steady state, which is the inter-module compensation power command, expressed as follows:

[0066] (5)

[0067] In the formula, P ISiref This represents the reference value for the compensation power of the i-th three-active bridge.

[0068] Figure 3The control strategy block diagram for the power distribution architecture of a medium-voltage AC bus-connected EV charging station under V2G is shown. It consists of the CHB control strategy block diagram and the TAB control strategy block diagram. In V2G mode, the CHB control strategy is consistent with the G2V mode and is still responsible for controlling the FBSM capacitor voltage.

[0069] In V2G mode, the TAB control strategy block diagram includes an output power loop and a power balancing loop. The host computer executes the control strategy according to the upper-level scheduling instructions. P V2Gref Based on the State of Charge (SOC) of all EVs connected to the charging station, calculate the charging power command for each EV. P EViref and power balance control commands between submodules P ISiref In V2G mode P EViref Power commands can be positive or negative. A positive command indicates that the EV is charging, while a negative command indicates that the EV is discharging. P EViref The calculation method pertains to EV charging station energy management strategies and is not covered in this invention. The constant power control method for TAB interface ③ in V2G mode and... P ISiref The calculation method is consistent with the G2V model.

[0070] In summary, this invention can reduce power conversion stages and improve the power density and operating efficiency of the EV charging station power distribution system. Compared with the existing medium-voltage AC bus direct-connection power distribution architecture, this invention can achieve power balance between sub-modules under any power usage conditions, improving power distribution flexibility and reliability. At the same time, this invention has a high degree of modularity, which facilitates production, manufacturing and maintenance.

[0071] Example 2:

[0072] This invention provides a control method for the power distribution architecture of a medium-voltage AC bus-connected EV charging station. The method uses the power distribution architecture of the medium-voltage AC bus-connected EV charging station described in Embodiment 1 to switch the charging station's operating mode, as detailed below:

[0073] S1. Power grid to charging station power supply mode: The cascaded H-bridge unit controls the capacitor voltage of the full bridge submodule. The interface ③ of the three active bridge converter unit adopts constant current and current sharing control strategy. Then, based on the output power of all interfaces ③, the power compensation required for each interface ② of the three active bridge converter unit to achieve power balance among the full bridge submodules in the cascaded H-bridge unit is calculated. Then, a constant power control strategy is adopted for interface ②.

[0074] S2. Charging station power supply mode to the grid: The cascaded H-bridge unit controls the capacitor voltage of the full-bridge submodule. The three active bridge converter units calculate the output power reference of interface ③ and the compensation power between the full-bridge submodules according to the instructions. Constant power control strategy is adopted for both interface ② and interface ③ to achieve power balance of the full-bridge submodules in the cascaded H-bridge unit.

[0075] Regarding the technical solution of this embodiment, the output power reference of interface ③ and the compensation power between full-bridge submodules are calculated as follows:

[0076] The output power of each full-bridge submodule is 1 / N of the total power on the medium-voltage AC bus side, and also 1 / N of the total power on the EV charging interface side, expressed as:

[0077] (6)

[0078] In the formula, in the formula, P SM1 ~ P SMN These represent the output power of full-bridge submodules 1 through N, with the positive direction being the power flow from the full-bridge submodules to interface ① of the three active bridge converter. P EV1 ~ P EVN-1 These represent the output power of interface ③ of the three active bridge converters 1 to N-1, respectively. The positive direction is defined as the power flowing from interface ③ of the three active bridge converters to the EV charging interface.

[0079] According to Kirchhoff's laws, the output power of the full-bridge submodule is also calculated from the port power of the three connected active bridge converter units, expressed as:

[0080] (7)

[0081] In the formula, PTi1 represents the input power of the i-th three-active bridge converter interface ①, with the positive direction being the power flowing from the full-bridge submodule to the three-active bridge converter interface ①; PTi2 represents the output power of the i-th three-active bridge converter interface ②, with the positive direction being the power flowing from the three-active bridge converter interface ② to the full-bridge submodule; and PTi3 represents the output power of the i-th three-active bridge converter interface ③, with the positive direction being the power flowing from the three-active bridge interface ③ to the EV charging interface.

[0082] For each three-active-bridge converter unit, according to power conservation:

[0083] (8)

[0084] The power of interface ③ of the three active bridge converter unit is the power on the EV charging interface side, specifically expressed as follows:

[0085] (9)

[0086] Combining equations (7) to (9), the power of each three-active-bridge converter unit interface ② under steady state is calculated, which is the compensation power between the full-bridge submodules. The expression is:

[0087] (10)

[0088] In the formula, P ISiref This represents the reference value for the compensation power of the i-th three-active bridge.

[0089] In some embodiments, a modulation strategy is also included, wherein CHB employs a phase-shift modulation strategy and TAB employs a single-phase-shift modulation strategy.

[0090] In some embodiments, fault-tolerant operation control is also included. When a full-bridge submodule or a three-active-bridge converter fails, the faulty circuit part is bypassed through the corresponding full-bridge submodule and bypass switch, and the control strategy and modulation strategy of the DC power distribution device are reconstructed so that other power modules can operate normally. After the faulty power module has completed repair and pre-charging, it is reconnected to the DC power distribution device, and the DC power distribution device resumes normal operation.

[0091] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0092] For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances. When an element is referred to as being "assembled on," "mounted on," "fixed to," or "set on" another element, it may be directly on the other element or there may be an intermediate element present. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible embodiments.

[0093] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0094] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

Claims

1. A medium-voltage AC busbar direct-connected EV charging station power distribution architecture, comprising a medium-voltage AC busbar and a coordination controller, characterized in that, The medium-voltage AC bus is electrically cross-connected with a three-phase cascaded H-bridge unit. Each phase cascaded H-bridge unit is electrically connected to several three-phase active bridge converter units. The cascaded H-bridge units and the three-phase active bridge converter units perform bidirectional power transmission. The three-phase active bridge converter units are connected to an EV charging interface. The coordinating controller connects the cascaded H-bridge and the three-phase active bridge converters through a sensor circuit. Each phase of the three-phase cascaded H-bridge unit includes a filter inductor and a series sub-module structure connected to the filter inductor. The series sub-module structure is composed of N full-bridge sub-modules cascaded together, which can realize the AC to DC conversion. The three-phase active bridge converter unit includes three full-bridge modules and a three-winding transformer. The AC side of the three full-bridge modules is connected to the three windings of the three-winding transformer, and the DC side of the three full-bridge modules is connected to the positive and negative terminals of the capacitors in the full-bridge sub-modules, respectively. The full-bridge submodule includes four ports: a, b, c, and d. Ports a and b are the input and output ports of the full-bridge submodule, respectively. The full-bridge submodule is connected in series to the cascaded H-bridge unit through ports a and b. Ports c and d are connected in parallel to the positive and negative terminals of the capacitor in the full-bridge submodule, respectively. The positive and negative terminals of the capacitors of the three full-bridge modules in the three active bridge converter unit generate three DC interfaces, namely interface ①, interface ② and interface ③. Interface ① and interface ② are connected to the c and d ports of two adjacent full-bridge sub-modules, respectively, to build a power path between the full-bridge sub-modules; interface ③ is connected to the EV charging interface. The EV charging station adopts a medium-voltage AC bus direct-connection power distribution architecture to switch the charging station's operating mode, as detailed below: Power grid feeding mode to charging station: The cascaded H-bridge unit controls the capacitor voltage of the full bridge submodule. The interface ③ of the three active bridge converter unit adopts constant current and current sharing control strategy. Then, based on the output power of all interfaces ③, the power compensation required for each interface ② of the three active bridge converter unit to achieve power balance among the full bridge submodules in the cascaded H-bridge unit is calculated. Then, a constant power control strategy is adopted for interface ②. Charging station power supply mode to the grid: The cascaded H-bridge unit controls the capacitor voltage of the full-bridge submodule. The three active bridge converter units calculate the output power reference of interface ③ and the compensation power between the full-bridge submodules according to the instructions. Constant power control strategy is adopted for both interface ② and interface ③ to achieve power balance of the full-bridge submodules in the cascaded H-bridge unit.

2. The medium-voltage AC busbar direct-connected EV charging station power distribution architecture according to claim 1, characterized in that: The three active bridge converter unit is configured as a dual transformer three active bridge converter, a three active half bridge converter, a dual transformer three active half bridge converter, or an isolated three-port resonant converter.

3. The medium-voltage AC busbar direct-connected EV charging station power distribution architecture according to claim 2, characterized in that, The three active bridge converters on each phase cascaded H-bridge unit are connected in parallel through interface ③ to achieve power balance between phases, and adjacent EV charging ports are connected in parallel to share current.

4. The medium-voltage AC busbar direct-connected EV charging station power distribution architecture according to claim 3, characterized in that, The output power reference of interface ③ and the compensation power between full-bridge submodules are calculated as follows: (41) The output power of each full-bridge submodule is 1 / N of the total power on the medium-voltage AC bus side, and also 1 / N of the total power on the EV charging interface side, expressed as: （1） In the formula, P SM1 ~ P SMN These represent the output power of full-bridge submodules 1 through N, with the positive direction being the power flow from the full-bridge submodules to interface ① of the three active bridge converter. P EV1 ~ P EVN-1 These are the output power of interface ③ of the three active bridge converters 1 to N-1, respectively. The positive direction is taken as the power flowing from interface ③ of the three active bridge converter to the EV charging interface. (42) According to Kirchhoff's laws, the output power of the full-bridge submodule can also be calculated from the port power of the three connected active bridge converter units, as follows: （2） In the formula, P Ti1 Let represent the input power of the i-th three-active-bridge converter interface ①, taking the power flow from the full-bridge submodule to the three-active-bridge converter interface ① as the positive direction. P Ti2 This represents the output power of the i-th three-active-bridge converter interface ②, with the positive direction defined as power flowing from the three-active-bridge converter interface ② to the full-bridge submodule. P Ti3 This represents the output power of the i-th three-active-bridge converter interface ③, with the positive direction being the power flowing from the three-active-bridge interface ③ to the EV charging interface; For each three-active-bridge converter unit, according to power conservation: （3） The power of interface ③ of the three active bridge converter unit is the power on the EV charging interface side, specifically expressed as follows: （4） Combining equations (2) to (4), the power of each three-active-bridge converter unit interface ② under steady state is calculated, which is the compensation power between the full-bridge submodules. The expression is: （5） In the formula, P ISiref This represents the reference value for the compensation power of the i-th three-active bridge.

5. The medium-voltage AC busbar direct-connected EV charging station power distribution architecture according to claim 4, characterized in that: The three active bridge converter units adopt a single phase-shift modulation strategy, and the cascaded H-bridge units adopt a phase-shift modulation strategy.

6. The medium-voltage AC busbar direct-connected EV charging station power distribution architecture according to claim 5, characterized in that: It also includes fault-tolerant operation control. When a full-bridge submodule or a three-phase active bridge converter fails, the faulty circuit part is bypassed through the corresponding full-bridge submodule and bypass switch, and the control strategy and modulation strategy of the DC power distribution device are reconstructed so that other power modules can operate normally. After the faulty power module has been repaired and pre-charged, it is reconnected to the DC power distribution device, and the DC power distribution device resumes normal operation.

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