Medium-voltage alternating-current bus direct-hanging type EV charging station power distribution framework and control method thereof

Abstract

The invention discloses a medium-voltage alternating-current 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 system comprises a medium-voltage alternating-current bus and a coordination controller, the medium-voltage alternating-current bus is in electrical cross connection with three phases of cascaded H-bridge units, each phase of cascaded H-bridge unit is electrically connected with a plurality of three-active-bridge converter units, and each three-active-bridge converter unit performs bidirectional power transmission with two cascaded H-bridge units. And the three-active bridge converter unit is connected with an EV charging interface. Power conversion between three-phase medium-voltage alternating current and multiple low-voltage direct current can be achieved in the EV charging station powered by a three-phase medium-voltage alternating current bus, compared with a traditional low-voltage power distribution framework, use of a high-power industrial frequency transformer can be avoided, power conversion links are reduced, the power density and the operation efficiency of a power distribution system of the EV charging station are improved, and the cost is reduced. And power balance among the sub-modules can be realized under any power consumption condition, so that the flexibility and reliability of power distribution are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and specifically to a medium-voltage AC bus directly-connected EV charging station power distribution architecture. Background Art

[0002] With the transformation of the global energy structure, the large-scale development of EVs has put forward higher requirements for charging infrastructure. Currently, the mainstream EV charging stations generally adopt low-voltage AC or low-voltage DC bus power distribution architectures, which require multiple levels of power conversion, resulting in low power distribution system efficiency and high costs. By using a medium-voltage AC bus directly-connected power distribution architecture, the power conversion links can be reduced, the system losses can be lowered, and the equipment power density can be increased. However, the power imbalance degree of multiple charging ports in the existing medium-voltage AC bus directly-connected power distribution architecture is limited, restricting its application in EV charging stations. Therefore, the present invention proposes a medium-voltage AC bus directly-connected EV charging station power distribution architecture and its control method. Summary of the Invention

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

[0004] To achieve the above purpose, the present invention provides the following technical solution: A medium-voltage AC bus directly-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 a three-phase cascaded H-bridge unit. Each phase of the cascaded H-bridge unit is electrically connected with a number of three-active-bridge converter units. The cascaded H-bridge unit and the three-active-bridge converter unit perform bidirectional power transmission, and an EV charging interface is connected to the three-active-bridge converter unit. The coordination controller is connected to the cascaded H-bridge and the three-active-bridge converter through a sensor circuit.

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

[0006] 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 the DC sides of the three full-bridge modules are respectively connected to the positive and negative electrodes of the full-bridge sub-module capacitor.

[0007] Furthermore, the three-active-bridge converter unit is set 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] Further, the full-bridge sub-module includes four ports a, b, c, and d. Ports a and b are the input and output ports of the full-bridge sub-module respectively. The full-bridge sub-module is connected in series to the cascaded H-bridge unit through ports a and b;

[0009] Ports c and d are respectively connected in parallel to the positive and negative electrodes of the capacitor in the full-bridge sub-module.

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

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

[0012] Further, the power distribution architecture includes two operating modes, namely the power feeding mode from the power grid to the charging station and the power feeding mode from the charging station to the power grid.

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

[0014] (71) Power feeding mode from the power grid to the charging station: 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 a constant current and current sharing control strategy, and then calculates the power to be compensated for interface ② of each three-active-bridge converter unit to achieve power balance between the full-bridge sub-modules in the cascaded H-bridge unit according to the output power of all interface ③s, and then adopts a constant power control strategy for interface ②;

[0015] (72) Power feeding mode from the charging station to the power grid: The cascaded H-bridge unit controls the capacitor voltage of the full-bridge sub-module. The three-active-bridge converter unit calculates the output power reference of interface ③ and the compensation power between the full-bridge sub-modules according to the instruction, and adopts a constant power control strategy for both interface ② and interface ③ to achieve power balance of the full-bridge sub-modules in the cascaded H-bridge unit.

[0016] Further, calculating the output power reference of interface ③ and the compensation power between the full-bridge sub-modules is specifically as follows:

[0017] (81) The output power of each full-bridge sub-module 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. The expression is:

[0018]

[0019] Wherein, P SM1 ~P SMN are respectively the output powers of full-bridge sub-modules 1 to N. The positive direction is defined as the power flowing from the full-bridge sub-module to the three-active-bridge converter interface ①. P EV1 ~P EVN-1 are respectively the output powers of the interfaces ③ of three-active-bridge converters 1 to N-1. The positive direction is defined as the power flowing from the interface ③ of the three-active-bridge converter to the EV charging interface.

[0020] (82) According to Kirchhoff's law, the output power of the full-bridge sub-module can also be calculated from the port power of the connected three-active-bridge converter unit, and is expressed as:

[0021]

[0022] Wherein, P Ti1 represents the input power of the interface ① of the i-th three-active-bridge converter. The positive direction is defined as the power flowing from the full-bridge sub-module to the interface ① of the three-active-bridge converter. P Ti2 represents the output power of the interface ② of the i-th three-active-bridge converter. The positive direction is defined as the power flowing from the interface ② of the three-active-bridge converter to the full-bridge sub-module. P Ti3 represents the output power of the interface ③ of the i-th three-active-bridge converter. The positive direction is defined as 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]

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

[0026]

[0027] Combining equations (2) to (4), the power of the interface ② of each three-active-bridge converter unit in the steady state is calculated, that is, the compensation power between the full-bridge sub-modules, and the expression is:

[0028]

[0029] Wherein, P ISiref represents the compensation power reference value of the i-th three-active-bridge.

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

[0031] Further, the control method further includes fault-tolerant operation control. When a full-bridge sub-module or a three-active-bridge converter power module fails, the faulty circuit part is bypassed through the corresponding full-bridge sub-module and bypass switch, and the control strategy and modulation strategy of the DC power distribution device are reconstructed to enable other power modules to operate normally. After the faulty power module is repaired and pre-charged, it is re-connected in series 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 the power conversion link and improve the power density and operation efficiency of the EV charging station power distribution system.

[0034] 2. Compared with the existing medium-voltage AC bus directly-connected power distribution architecture, the present invention can achieve power balance among full-bridge sub-modules under any power consumption conditions, improving the power distribution flexibility and reliability. At the same time, the present invention has a high modular level, which is convenient for production, manufacturing and maintenance.

[0035] Of course, it is not necessary for any product implementing the present invention to achieve all the above advantages simultaneously. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is the topological circuit diagram of the power distribution architecture described in the present invention;

[0037] Figure 2 is the control strategy block diagram of the power distribution architecture described in the present invention in the G2V mode;

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

[0039] Figure 4 is the topological circuit diagram of the power distribution architecture described in the present invention when the input side is single-phase alternating current. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] Hereinafter, the technical solutions in the embodiments of the present disclosure will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present disclosure. Apparently, the described embodiments are only a part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present disclosure.

[0041] Embodiment 1:

[0042] Please refer to Figures 1-4, the present invention provides a technical solution: a medium-voltage AC bus directly-connected EV charging station power distribution architecture, including a group of medium-voltage AC buses, a three-phase cascaded H-bridge (CHB) unit converter, 3*(N - 1) three-active-bridge converter (TAB) units, N - 1 EV charging interfaces, and a coordination controller. Among them, the medium-voltage AC bus is electrically connected to the three-phase cascaded H-bridge unit. Each phase of the cascaded H-bridge unit is electrically connected to several three-active-bridge converter units. The cascaded H-bridge unit and the three-active-bridge converter unit perform bidirectional power transmission, and the three-active-bridge converter unit is electrically connected to the EV charging interface. The coordination controller is connected to the cascaded H-bridge and the three-active-bridge converter through a sensor circuit to collect electrical and temperature signals, and then is connected to the drive circuits of the cascaded H-bridge and the three-active-bridge converter through optical fibers for drive control;

[0043] Each phase of the cascaded H-bridge in 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 connected in cascade;

[0044] 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 the DC sides of the three full-bridge modules are respectively connected to the positive and negative poles of the capacitor of the full-bridge sub-module;

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

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

[0047] Ports c and d are respectively connected in parallel to the positive and negative poles of the capacitor in the full-bridge sub-module. The capacitor of the full-bridge sub-module can achieve power decoupling between the CHB and the subsequent TAB, and can also provide power for the 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 poles of the capacitor of the full-bridge sub-module, that is, connected to ports c and d. The positive and negative poles of the sub-module capacitors of the three full-bridge modules are led out to generate three DC interfaces, namely interface ①, interface ②, and interface ③. The interface ① of the TAB i is connected to the FBSM iAt the CD end, interface ② is connected to FBSM i+1 At the CD end, a power path is constructed among the full-bridge sub-modules, enabling power balance among the full-bridge sub-modules. Interface ③ is connected to EV i The charging interface, where TAB i represents the i-th triple active bridge converter unit, FBSM i represents the i-th full-bridge sub-module, FBSM i+1 represents the (i + 1)-th full-bridge sub-module, EV i represents the i-th EV charging interface, and the value range of i is from 1 to N - 1.

[0049] It should be noted that the triple active bridge converter unit can also be replaced by fully isolated three-port DC / DC converters such as a dual-transformer triple active bridge converter, a triple active half-bridge converter, a dual-transformer triple active half-bridge converter, and an isolated three-port resonant converter. Among them, the star distribution architecture can also be changed to a triangular distribution architecture. This embodiment does not make specific limitations and can be selected according to actual situations.

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

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

[0052] Due to the limitation of the power imbalance operation boundary of the CHB sub-module, the traditional medium-voltage AC bus directly-connected EV charging station distribution architecture cannot cope with arbitrary EV unbalanced charging and discharging conditions. For the technical solution of this embodiment, the medium-voltage AC bus directly-connected EV charging station distribution architecture generates an isolated power path between the FBSMs of each phase CHB through TAB, enabling active power balance of the FBSMs, thus avoiding the constraints of the CHB unbalanced operation boundary and having better power supply flexibility and reliability.

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

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

[0055] Under the G2V mode, the TAB control strategy block diagram includes an output current loop and a power balance loop. The interface ③ of the TAB accessing the EV charging port adopts constant current control, and the deviation between the output current reference i EViref and the actual output current i Evi is sent to a PI regulator to generate the phase shift ratio φ 13 between the full-bridge of interface ① and the full-bridge of interface ③; the interface ② of the TAB adopts constant power control. According to the output power P EV1 -P EV(N-1) of all interfaces ③ of the TAB, the power reference P ISiref of its interface ② is calculated, and the deviation from the actual value P ISi is sent to a PI regulator to generate the phase shift ratio φ 12 between the full-bridge sub-module of interface ① and the full-bridge sub-module of interface ②.

[0056] The calculation method of the power reference of all interfaces ② of the TAB is as follows. Ignoring power losses, 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]

[0058] In the formula, P SM1 ~P SMN are the output powers of full-bridge sub-module 1 to full-bridge sub-module N respectively. Taking the power flowing from the full-bridge sub-module to the interface ① of the three-active-bridge converter as the positive direction, P EV1 ~P EVN-1 are the output powers of the interface ③ of three-active-bridge converter 1 to three-active-bridge converter N-1 respectively. Taking the power flowing from the interface ③ of the three-active-bridge converter to the EV charging interface as the positive direction. At the same time, according to Kirchhoff's law, the output power of the FBSM is also calculated from the power of the connected TAB ports, expressed as:

[0059]

[0060] In the formula, P Ti1 represents the input power of the interface ① of the i-th three-active-bridge converter. Taking the power flowing from the full-bridge sub-module to the interface ① of the three-active-bridge converter as the positive direction, P Ti2 represents the output power of the interface ② of the i-th three-active-bridge converter. Taking the power flowing from the interface ② of the three-active-bridge converter to the full-bridge sub-module as the positive direction, P Ti3Represents the output power of the i-th three-active-bridge converter interface ③, with the power flowing from the three-active-bridge interface ③ to the EV charging interface taken as the positive direction;

[0061] For each TAB, according to the law of conservation of power, we have:

[0062]

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

[0064]

[0065] Combining the above three equations, the power of each TAB interface ② under steady state can be calculated, which is the inter-module compensation power command, and the expression is

[0066]

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

[0068] Figure 3 Fig. is the control strategy block diagram of the medium-voltage AC bus directly-connected EV charging station distribution architecture under V2G, which consists of the CHB control strategy block diagram and the TAB control strategy block diagram. In the V2G mode, the CHB control strategy is the same as that in the G2V mode and still responsible for controlling the capacitor voltage of the FBSM.

[0069] In the V2G mode, the TAB control strategy block diagram includes an output power loop and a power balance loop. The upper computer calculates the EV charging power command P V2Gref and the power balance control command P EViref among sub-modules according to the superior scheduling command P ISiref and the SOC of all EVs connected to the charging station. In the V2G mode, the P EViref power command can be positive or negative. A positive command represents EV charging, and a negative command represents EV discharging. The calculation method of P EViref belongs to the energy management strategy of the EV charging station and is not involved in this invention. The constant power control method of the TAB interface ③ and the calculation method of P ISiref in the V2G mode are the same as those in the G2V mode.

[0070] In summary, the present invention can reduce the power conversion link, improve the power density and operation efficiency of the EV charging station distribution system; compared with the existing medium-voltage AC bus directly-connected distribution architecture, the present invention can achieve power balance among sub-modules under any power consumption condition, improving the distribution flexibility and reliability; at the same time, the present invention has a high modular level, which is convenient for production, manufacturing and maintenance.

[0071] Embodiment 2:

[0072] The present invention provides a control method for a medium-voltage AC bus directly-connected EV charging station power distribution architecture, which switches the working mode of the charging station by using the medium-voltage AC bus directly-connected EV charging station power distribution architecture described in Embodiment 1, as follows:

[0073] S1. Grid power feeding mode to the charging station: 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 a constant-current and current-sharing control strategy, and then calculates the power to be compensated at 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 according to the output power of all interfaces ③, and then adopts a constant-power control strategy for the interface ②;

[0074] S2. Charging station power feeding mode to the grid: The cascaded H-bridge unit controls the capacitor voltage of the full-bridge sub-module. The three-active-bridge converter unit calculates the output power reference of the interface ③ and the compensation power among the full-bridge sub-modules according to the instruction, and adopts a constant-power control strategy for both the interface ② and the interface ③ to achieve power balance among the full-bridge sub-modules in the cascaded H-bridge unit.

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

[0076] The output power of each full-bridge sub-module 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. The expression is:

[0077]

[0078] In the formula, SM1 ~P SMN are the output powers of full-bridge sub-module 1 to full-bridge sub-module N respectively. Taking the power flowing from the full-bridge sub-module to the interface ① of the three-active-bridge converter as the positive direction, P EV1 ~P EVN-1 are the output powers of the interface ③ of three-active-bridge converter 1 to three-active-bridge converter N-1 respectively. Taking the power flowing from the interface ③ of the three-active-bridge converter to the EV charging interface as the positive direction.

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

[0080]

[0081] Wherein, PTi1 represents the input power of the i-th three-active-bridge converter interface ①, with the power flowing from the full-bridge sub-module to the three-active-bridge converter interface ① taken as the positive direction; PTi2 represents the output power of the i-th three-active-bridge converter interface ②, with the power flowing from the three-active-bridge converter interface ② to the full-bridge sub-module taken as the positive direction; PTi3 represents the output power of the i-th three-active-bridge converter interface ③, with the power flowing from the three-active-bridge interface ③ to the EV charging interface taken as the positive direction;

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

[0083]

[0084] The power of the three-active-bridge converter unit interface ③ is the power on the EV charging interface side, and the specific expression is as follows:

[0085]

[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 sub-modules, and the expression is:

[0087]

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

[0089] In some embodiments, it further includes a modulation strategy. The CHB adopts a phase-shift modulation strategy, and the TAB adopts a single-phase-shift modulation strategy.

[0090] In some embodiments, it further includes a fault-tolerant operation control. When a fault occurs in the full-bridge sub-module or the three-active-bridge converter, the faulty circuit part is bypassed through the corresponding full-bridge sub-module and the bypass switch, and the control strategy and modulation strategy of the DC power distribution device are reconfigured to enable other power modules to operate normally; after the faulty power module is repaired and pre-charged, it is re-connected in series to the DC power distribution device, and the DC power distribution device resumes normal operation.

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

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

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

[0094] In the description of this specification, the description with reference to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

Claims

1. A medium voltage AC busbar direct-mounted EV charging station power distribution architecture, including 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 of the cascaded H-bridge unit is electrically connected to a number of three-active bridge converter units, the cascaded H-bridge unit and the three-active bridge converter unit perform bidirectional power transmission, and the three-active bridge converter unit is connected to an EV charging interface, and the coordination controller is connected to the cascaded H-bridge and the three-active bridge converter through a sensor circuit; Each phase cascade H-bridge in the three-phase cascade H-bridge unit includes a filter inductor and a series sub-module structure connected to the filter inductor, wherein the series sub-module structure is composed of N cascaded full-bridge sub-modules, which can realize the conversion from AC to DC; 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 the DC sides of the three full-bridge modules are respectively connected to the positive and negative electrodes of the full-bridge sub-module capacitors.

2. The medium voltage AC busbar direct-mounted EV charging station power distribution architecture according to claim 1 is characterized by: 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-mounted EV charging station power distribution architecture according to claim 2 is characterized by: The full-bridge submodule includes four ports, a, b, c, and d, wherein ports a and b are the input and output ports of the full-bridge submodule respectively, and the full-bridge submodule is connected in series to the cascaded H-bridge unit through ports a and b; The c and d ports are respectively connected in parallel to the positive and negative electrodes of the capacitor in the full-bridge submodule.

4. The medium voltage AC busbar direct-mounted EV charging station power distribution architecture according to claim 3 is characterized by: The positive and negative electrodes of the capacitors of the three full-bridge modules in the three-active bridge converter unit are led out to generate three DC interfaces, namely interface ①, interface ② and interface ③. Interface ① and interface ② are respectively connected to the c and d ports of two adjacent full-bridge sub-modules to build a power path between the full-bridge sub-modules; interface ③ is connected to the EV charging interface.

5. The medium voltage AC busbar direct-mounted EV charging station power distribution architecture according to claim 4 is characterized in that: The three active bridge converters on each phase cascaded H-bridge unit are connected in parallel and output current sharing through interface ③ to achieve power balance between phases, and adjacent EV charging ports are connected in parallel and output current sharing.

6. The medium voltage AC busbar direct-mounted EV charging station power distribution architecture according to claim 1, characterized in that: There are two operating modes: the power grid feeds energy to the charging station and the charging station feeds energy to the power grid.

7. A method for controlling a power distribution architecture of a medium-voltage AC busbar direct-mounted EV charging station, using the power distribution architecture of a medium-voltage AC busbar direct-mounted EV charging station according to any one of claims 1 to 6 to switch the charging station working mode, characterized in that: The details are as follows: (71) The grid feeds energy to the charging station in this mode: the cascaded H-bridge unit controls the capacitor voltage of the full-bridge sub-module, and the interface ③ of the three active bridge converter units adopts a constant current and current sharing control strategy. Then, based on the output power of all interfaces ③, the power required to be compensated by the interface ② of each of the three active bridge converter units to achieve power balance between the full-bridge sub-modules in the cascaded H-bridge unit is calculated, and then a constant power control strategy is adopted for interface ②. (72) Charging station feeds power to the grid: The cascaded H-bridge unit controls the capacitor voltage of the full-bridge sub-module. The three active bridge converter units calculate the output power reference of interface ③ and the compensation power between the full-bridge sub-modules according to the instructions. A constant power control strategy is adopted for both interface ② and interface ③ to achieve power balance of the full-bridge sub-modules in the cascaded H-bridge unit.

8. The method for controlling the power distribution architecture of a medium voltage AC busbar direct-mounted EV charging station according to claim 7, characterized in that: Calculate the output power reference of interface ③ and the compensation power between full-bridge sub-modules as follows: (81) The output power of each full-bridge submodule is 1 / N of the total power on the medium voltage AC bus side, and is also 1 / N of the total power on the EV charging interface side, expressed as: Where P SM1 ~P SMN are the output powers of full-bridge submodules 1 to N, respectively. The power flowing from the full-bridge submodule to the three-active-bridge converter interface ① is taken as the positive direction, P EV1 ~P EVN-1 They are the output powers of interfaces ③ of three active bridge converters 1 to three active bridge converters N-1, and the power flowing from interface ③ of the three active bridge converter to the EV charging interface is taken as the positive direction. (82) According to Kirchhoff’s law, the output power of the full-bridge submodule can also be calculated from the port power of the three connected active bridge converter units, expressed as: Where P Ti1 represents the input power of the i-th three-active-bridge converter interface ①, where the power flowing from the full-bridge submodule to the three-active-bridge converter interface ① is taken as the positive direction, P Ti2 represents the output power of the i-th three-active bridge converter interface ②, where the power flowing from the three-active bridge converter interface ② to the full-bridge submodule is taken as the positive direction, P Ti3 represents the output power of the i-th three-active bridge converter interface ③, and the power flowing from the three-active bridge interface ③ to the EV charging interface is taken as the positive direction; For each three-active bridge converter unit, according to the power conservation law: The power of the three active bridge converter unit interface ③ is the power on the EV charging interface side, which is specifically expressed as follows: Combining equations (2) to (4), the power of each three-active bridge converter unit interface ② in steady state, that is, the compensation power between the full-bridge sub-modules, is calculated as follows: Where P ISiref represents the compensation power reference value of the i-th triple active bridge.

9. The method for controlling the power distribution architecture of a medium voltage AC busbar direct-mounted EV charging station according to claim 8, 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.

10. The method for controlling the power distribution architecture of a medium voltage AC busbar direct-mounted EV charging station according to claim 9, characterized in that: It also includes fault-tolerant operation control. When a full-bridge sub-module or a three-active-bridge converter fails, the faulty circuit portion is bypassed through the corresponding full-bridge sub-module and the bypass switch, and the control strategy and modulation strategy of the DC distribution device are reconstructed to enable the normal operation of other power modules; after the faulty power module is repaired and pre-charged, it is re-connected in series with the DC distribution device, and the DC distribution device resumes normal operation.

Images