Energy storage system and charging station

Abstract

Provided in the embodiments of the present application are an energy storage system and a charging station. The energy storage system comprises an alternating-current power grid, an alternating current-direct current (AC-DC) system and a direct-current bus, wherein an input end of the AC-DC system is connected to the alternating-current power grid, an output end of the AC-DC system is connected to the direct-current bus, and the direct-current bus supplies power to a load; the AC-DC system comprises N cascaded AC-DC converters, and each AC-DC converter uses a single-stage structure, N being an integer greater than or equal to 2. The cost of the energy storage system can be reduced.

Description

Energy storage systems and charging stations

[0001] This application claims priority to Chinese Patent Application No. 2024110267722, filed on July 29, 2024, entitled “Energy Storage System and Charging Station”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of electronic circuit technology, specifically to an energy storage system and a charging station. Background Technology

[0003] There are currently two main transformer isolation schemes for energy storage systems. The first involves converting the 10kV AC power from the grid to 380V via a power frequency transformer, and then converting it to high-voltage DC (e.g., 800V DC) via an alternating current-to-direct current (AC-DC) module. The second involves converting the 10kV AC power from the grid to high-voltage DC via a high-frequency converter. Because high-frequency converters are small, the overall size of the energy storage system can be reduced. However, current high-frequency converters employ a two-stage structure and a large number of electronic switches, resulting in higher costs for the energy storage system. Summary of the Invention

[0004] This application provides an energy storage system and a charging station, which can reduce the cost of the energy storage system.

[0005] A first aspect of this application provides an energy storage system, including an AC power grid, an AC-DC system, and a DC bus; the input terminal of the AC-DC system is connected to the AC power grid, the output terminal of the AC-DC system is connected to the DC bus, and the AC-DC system supplies power to the load through the DC bus;

[0006] The AC-DC system includes N cascaded AC-DC converters, each employing a single-stage structure, where N is an integer greater than or equal to 2.

[0007] Optionally, the AC-DC system includes multiple AC-DC modules;

[0008] Each AC-DC module includes n1 cascaded AC-DC converters; n1 is an integer greater than or equal to 2;

[0009] The input terminal of each AC-DC module is connected to one phase of the three-phase transmission line of the AC power grid, and the output terminal of each AC-DC module is connected to the DC bus.

[0010] Optionally, in each AC-DC module, the primary sides of the n1 cascaded AC-DC converters are connected in series, and the secondary sides of the n1 cascaded AC-DC converters are connected in parallel.

[0011] Optionally, at least a portion of the AC-DC converter may be connected in series between any two phase transmission lines of the AC power grid.

[0012] Optionally, each AC-DC converter includes a first input terminal, a second input terminal, a first output terminal, and a second output terminal; the AC-DC converter of each AC-DC module includes: a first-stage AC-DC converter, at least one intermediate-stage AC-DC converter, and a last-stage AC-DC converter.

[0013] In this configuration, the first input terminal of the first-stage AC-DC converter of each AC-DC module is connected to one phase of the three-phase transmission line of the AC power grid, and the second input terminal of the last-stage AC-DC converter of each AC-DC module is shared; the first output terminal of each AC-DC converter is connected to the positive terminal of the DC bus, and the second output terminal of each AC-DC converter is connected to the negative terminal of the DC bus.

[0014] In each AC-DC module, the first input terminal of the intermediate stage AC-DC converter is connected to the second input terminal of the AC-DC converter of the previous stage; the first input terminal of the last stage AC-DC converter is connected to the second input terminal of the AC-DC converter of the previous stage.

[0015] Optionally, the plurality of AC-DC modules include a first-phase AC-DC module, a second-phase AC-DC module, and a third-phase AC-DC module. The first-phase AC-DC module includes: a first-phase first-stage AC-DC converter, a first-phase intermediate-stage AC-DC converter, and a first-phase last-stage AC-DC converter; the second-phase AC-DC module includes: a second-phase first-stage AC-DC converter, a second-phase intermediate-stage AC-DC converter, and a second-phase last-stage AC-DC converter; the third-phase AC-DC module includes: a third-phase first-stage AC-DC converter, a third-phase intermediate-stage AC-DC converter, and a third-phase last-stage AC-DC converter.

[0016] Wherein, the first input terminal of the first-phase first-stage AC-DC converter is connected to the first-phase transmission line of the AC power grid; the first input terminal of the second-phase first-stage AC-DC converter is connected to the second-phase transmission line of the AC power grid; and the first input terminal of the third-phase first-stage AC-DC converter is connected to the third-phase transmission line of the AC power grid. The second input terminal of the first-phase last-stage AC-DC converter is connected to the second input terminal of the last-stage AC-DC converter of the second-phase AC-DC module and the second input terminal of the last-stage AC-DC converter of the third-phase AC-DC module. The first output terminal of each AC-DC converter is connected to the positive terminal of the DC bus, and the second output terminal of each AC-DC converter is connected to the negative terminal of the DC bus.

[0017] The first input terminal of the first phase intermediate stage AC-DC converter is connected to the second input terminal of the AC-DC converter above the first phase intermediate stage AC-DC converter, and the first input terminal of the first phase last stage AC-DC converter is connected to the second input terminal of the AC-DC converter above the first phase last stage AC-DC converter.

[0018] The first input terminal of the second phase intermediate stage AC-DC converter is connected to the second input terminal of the previous stage AC-DC converter, and the first input terminal of the second phase last stage AC-DC converter is connected to the second input terminal of the previous stage AC-DC converter.

[0019] The first input terminal of the third-phase intermediate stage AC-DC converter is connected to the second input terminal of the AC-DC converter above the third-phase intermediate stage AC-DC converter, and the first input terminal of the third-phase last stage AC-DC converter is connected to the second input terminal of the AC-DC converter above the third-phase last stage AC-DC converter.

[0020] Optionally, the AC-DC converter includes: a primary circuit, a transformer, and a secondary circuit. The primary circuit includes two or three primary bridge arms, and the secondary circuit includes two secondary bridge arms. The first output terminal of the AC-DC converter is connected to the first ends of the two secondary bridge arms, and the second output terminal of the AC-DC converter is connected to the second ends of the two secondary bridge arms. The midpoints of the two secondary bridge arms are respectively connected to the two ends of the secondary winding of the transformer.

[0021] When the primary circuit includes two primary bridge arms, the midpoints of the two primary bridge arms are respectively adapted to connect the first input terminal and the second input terminal of the AC-DC converter, and the midpoints of the two primary bridge arms are respectively adapted to the two ends of the primary winding of the transformer.

[0022] In the case where the primary-side circuit includes three primary-side bridge arms, the midpoints of two of the three primary-side bridge arms are adapted to connect the first input terminal of the AC-DC converter and the two ends of the primary winding of the transformer, and the midpoint of the other bridge arm is connected to the second input terminal of the AC-DC converter.

[0023] Optionally, when the primary-side circuit includes three primary-side bridge arms, the primary-side circuit includes: a first primary-side bridge arm, a second primary-side bridge arm, and a third primary-side bridge arm, and the secondary-side circuit includes: a first secondary-side bridge arm and a second secondary-side bridge arm; the first end of the first primary-side bridge arm is connected to the first end of the second primary-side bridge arm and the first end of the third primary-side bridge arm, and the second end of the first primary-side bridge arm is connected to the second end of the second primary-side bridge arm and the second end of the third primary-side bridge arm;

[0024] The first input terminal of the AC-DC converter is adapted to connect the midpoint of the first primary bridge arm and the midpoint of the second primary bridge arm, the midpoint of the first and second primary bridge arms is adapted to connect the first end of the primary winding of the transformer, the midpoint of the second primary bridge arm is adapted to connect the second end of the primary winding of the transformer, and the second input terminal of the AC-DC converter is connected to the midpoint of the third primary bridge arm.

[0025] The first output terminal of the AC-DC converter is connected to the first end of the first secondary bridge arm and the first end of the second secondary bridge arm. The second output terminal of the AC-DC converter is connected to the second end of the first secondary bridge arm and the second end of the second secondary bridge arm. The midpoint of the first secondary bridge arm is connected to the first end of the secondary winding of the transformer, and the midpoint of the second secondary bridge arm is connected to the second end of the secondary winding of the transformer.

[0026] Optionally, the primary-side circuit further includes a first inductor, a second inductor, a third inductor, and a first capacitor, and the secondary-side circuit further includes a second capacitor; the first end of the first primary-side bridge arm is connected to the first end of the first capacitor, and the second end of the first primary-side bridge arm is connected to the second end of the first capacitor;

[0027] The first input terminal of the AC-DC converter is connected to the first terminal of the first inductor and the first terminal of the second inductor. The second terminal of the first inductor is connected to the midpoint of the first primary bridge arm and the first terminal of the third inductor. The second terminal of the third inductor is connected to the first terminal of the primary winding of the transformer. The second terminal of the second inductor is connected to the midpoint of the second primary bridge arm and the second terminal of the primary winding of the transformer.

[0028] The first output terminal of the AC-DC converter is connected to the first terminal of the second capacitor, and the second output terminal of the AC-DC converter is connected to the second terminal of the second capacitor.

[0029] Optionally, when the primary-side circuit includes three primary-side bridge arms, the primary-side circuit includes: a first primary-side bridge arm, a second primary-side bridge arm, and a third primary-side bridge arm, and the secondary-side circuit includes: a first secondary-side bridge arm and a second secondary-side bridge arm; the first end of the first primary-side bridge arm is connected to the first end of the second primary-side bridge arm and the first end of the third primary-side bridge arm, and the second end of the first primary-side bridge arm is connected to the second end of the second primary-side bridge arm and the second end of the third primary-side bridge arm;

[0030] The first input terminal of the AC-DC converter is adapted to be connected to the midpoint of the first primary bridge arm, the midpoint of the first primary bridge arm is adapted to be connected to the first end of the primary winding of the transformer, the midpoint of the second primary bridge arm is adapted to be connected to the second end of the primary winding of the transformer, and the second input terminal of the AC-DC converter is connected to the midpoint of the third primary bridge arm.

[0031] The first output terminal of the AC-DC converter is connected to the first end of the first secondary bridge arm and the first end of the second secondary bridge arm. The second output terminal of the AC-DC converter is connected to the second end of the first secondary bridge arm and the second end of the second secondary bridge arm. The midpoint of the bridge arm of the first secondary bridge arm is connected to the first end of the secondary winding of the transformer, and the midpoint of the bridge arm of the second secondary bridge arm is connected to the second end of the secondary winding of the transformer.

[0032] Optionally, the primary-side circuit further includes a first inductor, a second inductor, a third inductor, a first capacitor, and a third capacitor, and the secondary-side circuit further includes a second capacitor; the first end of the first primary-side bridge arm is connected to the first end of the first capacitor, and the second end of the first primary-side bridge arm is connected to the second end of the first capacitor;

[0033] The first input terminal of the AC-DC converter is connected to the first terminal of the first inductor and the first terminal of the second inductor. The second terminal of the first inductor is connected to the midpoint of the first primary bridge arm and the first terminal of the third inductor. The second terminal of the third inductor is connected to the first terminal of the primary winding of the transformer. The second terminal of the second inductor is connected to the first terminal of the third capacitor and the midpoint of the second primary bridge arm. The second terminal of the third capacitor is connected to the second terminal of the primary winding of the transformer.

[0034] The first output terminal of the AC-DC converter is connected to the first terminal of the second capacitor, and the second output terminal of the AC-DC converter is connected to the second terminal of the second capacitor.

[0035] Optionally, when the primary-side circuit includes two primary-side bridge arms, the primary-side circuit includes: a first primary-side bridge arm and a second primary-side bridge arm, and the secondary-side circuit includes: a first secondary-side bridge arm and a second secondary-side bridge arm; the first end of the first primary-side bridge arm is connected to the first end of the second primary-side bridge arm, and the second end of the first primary-side bridge arm is connected to the second end of the second primary-side bridge arm.

[0036] The first input terminal of the AC-DC converter is adapted to be connected to the midpoint of the first primary bridge arm, the midpoint of the first primary bridge arm is adapted to be connected to the first end of the primary winding of the transformer, and the second input terminal of the AC-DC converter is connected to the midpoint of the second primary bridge arm and the second end of the primary winding of the transformer.

[0037] The first output terminal of the AC-DC converter is connected to the first end of the first secondary bridge arm and the first end of the second secondary bridge arm. The second output terminal of the AC-DC converter is connected to the second end of the first secondary bridge arm and the second end of the second secondary bridge arm. The midpoint of the bridge arm of the first secondary bridge arm is connected to the first end of the secondary winding of the transformer, and the midpoint of the bridge arm of the second secondary bridge arm is connected to the second end of the secondary winding of the transformer.

[0038] The primary-side circuit further includes a first inductor, a second inductor, a third inductor, and a first capacitor; the secondary-side circuit further includes a second capacitor; the first end of the first primary-side bridge arm is connected to the first end of the first capacitor, and the second end of the first primary-side bridge arm is connected to the second end of the first capacitor.

[0039] The first input terminal of the AC-DC converter is connected to the first terminal of the first inductor, the second terminal of the first inductor is connected to the midpoint of the first primary bridge arm and the first terminal of the second inductor, and the second terminal of the second inductor is connected to the first terminal of the primary winding of the transformer.

[0040] The first output terminal of the AC-DC converter is connected to the first terminal of the second capacitor, and the second output terminal of the AC-DC converter is connected to the second terminal of the second capacitor.

[0041] Optionally, the load may include an electric vehicle or an energy storage device.

[0042] Optionally, the energy storage system further includes photovoltaic modules, and the DC bus is connected to the photovoltaic modules via a DC-DC module.

[0043] A second aspect of this application provides a charging station, including the energy storage system described in the first aspect.

[0044] The energy storage system of this application embodiment includes an AC power grid, an AC-DC system, and a DC bus. The input terminal of the AC-DC system is connected to the AC power grid, and the output terminal of the AC-DC system is connected to the DC bus. The AC-DC system supplies power to the load through the DC bus. The AC-DC system includes N cascaded AC-DC converters, each employing a single-stage structure, where N is an integer greater than or equal to 2. Each AC-DC converter in the AC-DC system employs a single-stage structure, which, compared to a two-stage structure, uses fewer electronic switching transistors, thereby reducing the cost of the energy storage system.

[0045] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 is a schematic diagram of an energy storage system provided in an embodiment of this application;

[0048] Figure 2 is an AC-DC converter with a two-stage structure provided in an embodiment of this application;

[0049] Figure 3 is an AC-DC converter with a single-stage structure provided in an embodiment of this application;

[0050] Figure 4 is a schematic diagram of an AC-DC converter provided in an embodiment of this application;

[0051] Figure 5 is a schematic diagram of an AC-DC converter provided in an embodiment of this application;

[0052] Figure 6 is a schematic diagram of the specific structure of an AC-DC converter provided in an embodiment of this application;

[0053] Figure 7 is a schematic diagram of the specific structure of an AC-DC converter provided in an embodiment of this application;

[0054] Figure 8 is a schematic diagram of the specific structure of an energy storage system provided in an embodiment of this application;

[0055] Figure 9 is a schematic diagram of the specific structure of another energy storage system provided in an embodiment of this application;

[0056] Figure 10 is a structural schematic diagram of a charging station provided in an embodiment of this application.

[0057] Explanation of reference numerals in the attached diagram: 100-AC power grid, 200-AC-DC system, 210-AC-DC converter, 211-primary circuit, 212-transformer, 213-secondary circuit, 214-AC-DC unit, 215-DC-DC unit, 300-DC bus, 400-photovoltaic module, 500-energy storage device, 600-electric vehicle. Specific Implementation

[0058] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0059] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, system, product, or apparatus that comprises a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, products, or apparatuses.

[0060] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments.

[0061] Please refer to Figure 1, which is a schematic diagram of an energy storage system provided in an embodiment of this application. As shown in Figure 1, the energy storage system includes an AC power grid 100, an AC-DC system 200, and a DC bus 300; the input terminal of the AC-DC system 200 is connected to the AC power grid 100, the output terminal of the AC-DC system 200 is connected to the DC bus 300, and the AC-DC system supplies power to the load through the DC bus 300;

[0062] The AC-DC system 200 includes N cascaded AC-DC converters 210 (AC-DC 11, AC-DC 21, ..., AC-DC n1, AC-DC 12, AC-DC 22, ..., AC-DC n2, AC-DC 13, AC-DC 23, ..., AC-DC n3 as shown in Figure 1). The AC-DC converters 210 adopt a single-stage structure, and N is an integer greater than or equal to 2.

[0063] In this embodiment, the AC power on the AC grid can be any of 380V, 660V, 1000V, 3kV, 6kV, 10kV, 35kV, 66kV, 110kV, 220kV, 330kV, 500kV, 750kV, or 1000kV. The DC bus voltage can be 800V or 650V. An AC-DC system can convert AC power to DC power. For example, if the AC power on the AC grid is 10 kV, the AC-DC system can convert 10kV AC power to 800V DC power and output 800V DC power to the DC bus.

[0064] Traditional AC-DC converters employ a two-stage structure, comprising an AC-DC unit and a DC-DC unit. The AC-DC unit first converts alternating current (AC) into direct current (DC) at a specific voltage to achieve power factor correction, and then the DC-DC unit converts it into high-voltage DC. The AC-DC converter in this application adopts a single-stage structure, combining the AC-DC unit and the DC-DC unit into one, eliminating the need for a two-stage structure. Compared to traditional two-stage AC-DC converters, the single-stage structure reduces the number of electronic switches used, resulting in lower costs.

[0065] Please refer to Figures 2 and 3. Figure 2 shows an AC-DC converter 210 with a two-stage structure according to an embodiment of this application, and Figure 3 shows an AC-DC converter with a single-stage structure according to an embodiment of this application. The AC-DC converter 210 shown in Figure 2 includes a two-stage structure composed of an AC-DC unit 214 and a DC-DC unit 215. The AC-DC converter 210 shown in Figure 2 contains 12 electronic switches (AC-DC unit 214 contains 4 electronic switches, and DC-DC unit 215 contains 8 electronic switches). The AC-DC converter 210 shown in Figure 3 contains 10 electronic switches. For an AC-DC system 200 containing N AC-DC converters 210, 2*N electronic switches can be saved, thereby reducing the number of electronic switches used in the AC-DC converter, reducing the cost of the AC-DC converter, and consequently reducing the cost of the energy storage system.

[0066] Optionally, as shown in Figure 1, the energy storage system also includes a DC-DC module, through which the DC bus 300 supplies power to at least one load. The DC-DC module may include at least one DC-DC converter (as shown in Figure 1), with each DC-DC converter corresponding to at least one load. Each DC-DC converter can supply power to its corresponding load.

[0067] Optionally, the load may include an electric vehicle or an energy storage device. The energy storage system can charge both the electric vehicle and the energy storage device.

[0068] Electric vehicles are cars powered by electricity, and they can include power batteries. Energy storage devices are devices used to store energy, and they can include energy storage batteries. Power batteries and energy storage batteries are not the same type of battery. Energy storage batteries have lower energy density and longer lifespan, and are classified as energy-type batteries. Power batteries have higher energy density and longer driving range, and are classified as power-type batteries.

[0069] Optionally, the energy storage system further includes a photovoltaic module 400, and the DC bus 300 is connected to the photovoltaic module 400 via a DC-DC module.

[0070] Photovoltaic (PV) modules are components that generate electricity using solar energy. The voltage of a PV module is not the same as the DC bus voltage. For example, a PV module consisting of 50 or 100 photovoltaic panels connected in series will output a voltage between 200V and 300V. The DC bus voltage is 600-800V. The PV module discharges to the DC bus through a DC-DC module. Energy storage batteries and electric vehicles can both charge and discharge to the DC bus. For instance, if an electric vehicle requires 500kW of charging power, and the PV module generates 100kW, the remaining 400kW will be drawn from the AC grid, passed through the AC-DC system to the DC bus, and then used to charge the electric vehicle via the DC-DC module.

[0071] The power generated by photovoltaic modules may not be enough for electric vehicles. Currently, the main power source is the AC grid, with energy storage batteries and photovoltaic modules serving as supplements.

[0072] The energy from the photovoltaic modules, once connected to the DC bus, can power energy storage batteries and electric vehicles, distributed according to demand.

[0073] As shown in Figure 1, the DC-DC module can contain three DC-DC converters, which are respectively connected to the photovoltaic module 400, the energy storage device 500, and the electric vehicle 600.

[0074] It should be noted that Figure 1 is only one possible example, and the number of DC-DC converters included in the DC-DC module can be greater than or equal to two. For example, there may be M1 photovoltaic modules 400 connected to the DC bus 300, M2 energy storage devices 500 connected to the DC bus, and M3 electric vehicles connected to the DC bus. Therefore, the total number of DC-DC converters that the DC-DC module can include is (M1 + M2 + M3).

[0075] The energy storage system of this application embodiment includes an AC power grid, an AC-DC system, and a DC bus. The input terminal of the AC-DC system is connected to the AC power grid, and the output terminal of the AC-DC system is connected to the DC bus. The AC-DC system supplies power to the load through the DC bus. The AC-DC system includes N cascaded AC-DC converters, each employing a single-stage structure, where N is an integer greater than or equal to 2. On one hand, each AC-DC converter in the AC-DC system employs a single-stage structure, which uses fewer electronic switches compared to a two-stage structure, thereby reducing the cost of the energy storage system. On the other hand, the cascading of the N AC-DC converters in the AC-DC system reduces the voltage stress on the electronic switches in the AC-DC converters, thereby reducing the cost of the AC-DC converters and, consequently, the cost of the energy storage system.

[0076] Optionally, at least a portion of the AC-DC converter 210 may be connected in series between any two phase transmission lines of the AC power grid 100.

[0077] In this embodiment of the application, the AC power grid is a three-phase AC power grid, which includes a first-phase transmission line (as shown in Figure 1, phase A transmission line), a second-phase transmission line (as shown in Figure 1, phase B transmission line), and a third-phase transmission line (as shown in Figure 1, phase C transmission line).

[0078] In the N cascaded AC-DC converters 210, each AC-DC converter 210 is connected in series with two phase transmission lines of the AC power grid 100. Taking Figure 1 as an example, AC-DC converter 11 is connected in series with phase A and phase B transmission lines, or AC-DC converter 11 is connected in series with phase A and phase C transmission lines. AC-DC converter 12 is connected in series with phase A and phase B transmission lines, or AC-DC converter 12 is connected in series with phase B and phase C transmission lines. AC-DC converter 13 is connected in series with phase A and phase C transmission lines, or AC-DC converter 13 is connected in series with phase B and phase C transmission lines.

[0079] In Figure 1, AC-DC 11, AC-DC 21, ... AC-DC n1 are connected in series, AC-DC 12, AC-DC 22, ... AC-DC n2 are connected in series, and AC-DC 13, AC-DC 23, ... AC-DC n3 are connected in series. This can reduce the voltage stress on the electronic switching transistors in the AC-DC converter, thereby reducing the cost of the AC-DC converter and, consequently, the cost of the energy storage system.

[0080] Optionally, in each AC-DC module, the primary sides of the n1 cascaded AC-DC converters 210 are connected in series, and the secondary sides of the n1 cascaded AC-DC converters 210 are connected in parallel. As shown in Figure 1, the primary sides of AC-DC11, AC-DC21, ..., AC-DCn1 are connected in series, and the secondary sides of AC-DC11, AC-DC21, ..., AC-DCn1 are connected in parallel.

[0081] In each AC-DC module, the primary side of each AC-DC converter 210 includes a first input terminal and a second input terminal, and the secondary side of each AC-DC converter 210 includes a first output terminal and a second output terminal. In two adjacent AC-DC converters 210, the first input terminal of the current stage AC-DC converter is connected to the second input terminal of the previous stage AC-DC converter; the second input terminal of the current stage AC-DC converter is connected to the first input terminal of the next stage AC-DC converter. In each AC-DC module, the first output terminals of each AC-DC converter 210 are connected together, and the second output terminals of each AC-DC converter 210 are connected together.

[0082] Optionally, each AC-DC converter 210 includes a first input terminal, a second input terminal, a first output terminal, and a second output terminal; the AC-DC converter of each AC-DC module includes: a first-stage AC-DC converter (AC-DC 11 as shown in Figure 1), at least one intermediate-stage AC-DC converter (AC-DC 21, AC-DC 31, etc. as shown in Figure 1), and a last-stage AC-DC converter (AC-DC n1 as shown in Figure 1);

[0083] In this configuration, the first input terminal of the first-stage AC-DC converter of each AC-DC module is connected to one phase of the three-phase transmission line of the AC power grid 100, and the second input terminal of the last-stage AC-DC converter of each AC-DC module is shared; the first output terminal of each AC-DC converter is connected to the positive terminal of the DC bus 300, and the second output terminal of each AC-DC converter is connected to the negative terminal of the DC bus 300.

[0084] In each AC-DC module, the first input terminal of the intermediate stage AC-DC converter is connected to the second input terminal of the AC-DC converter of the previous stage; the first input terminal of the last stage AC-DC converter is connected to the second input terminal of the AC-DC converter of the previous stage.

[0085] Optionally, the plurality of AC-DC modules includes a first-phase AC-DC module, a second-phase AC-DC module, and a third-phase AC-DC module. The first-phase AC-DC module includes n1 cascaded AC-DC converters 210, the second-phase AC-DC module includes n2 cascaded AC-DC converters 210, and the third-phase AC-DC module includes n3 cascaded AC-DC converters; n1, n2, and n3 are all integers greater than or equal to 2. N = n1 + n2 + n3.

[0086] In the embodiments of this application, n1, n2, and n3 may be equal or unequal. Figure 1 takes the equality of n1, n2, and n3 as an example. In Figure 1, n1 = n2 = n3 = n, and N = 3 * n.

[0087] The first phase AC-DC module includes AC-DC 11, AC-DC 21, ..., AC-DC n1, a total of n cascaded AC-DC converters 210. The second phase AC-DC module includes AC-DC 12, AC-DC 22, ..., AC-DC n2, a total of n cascaded AC-DC converters 210. The third phase AC-DC module includes AC-DC 13, AC-DC 23, ..., AC-DC n3, a total of n cascaded AC-DC converters 210.

[0088] The input terminal of the first phase AC-DC module is connected to the first phase transmission line of the AC power grid 100, the input terminal of the second phase AC-DC module is connected to the second phase transmission line of the AC power grid 100, the input terminal of the third phase AC-DC module is connected to the third phase transmission line of the AC power grid 100, and the output terminals of the first phase AC-DC module, the second phase AC-DC module, and the third phase AC-DC module are connected to the DC bus 300.

[0089] The n1 cascaded AC-DC converters 210 include: a first-stage AC-DC converter (AC-DC 11 as shown in Figure 1), at least one intermediate-stage AC-DC converter (AC-DC 21, AC-DC 31, etc. as shown in Figure 1), and a last-stage AC-DC converter (AC-DC n1 as shown in Figure 1); the n2 cascaded AC-DC converters include: a second-phase first-stage AC-DC converter (AC-DC 12 as shown in Figure 1), at least one second-phase intermediate-stage AC-DC converter (AC-DC 22, AC-DC 32, etc. as shown in Figure 1), and a second-phase last-stage AC-DC converter (AC-DC n2 as shown in Figure 1); the n3 cascaded AC-DC converters include: a third-phase first-stage AC-DC converter (AC-DC 13 as shown in Figure 1), at least one third-phase intermediate-stage AC-DC converter (AC-DC 23, AC-DC 33, etc. as shown in Figure 1), and a third-phase last-stage AC-DC converter (AC-DC n2 as shown in Figure 1). n3);

[0090] Wherein, the first input terminal of the first-phase first-stage AC-DC converter is connected to the first-phase transmission line of the AC power grid 100 (as shown in Figure 1, phase A transmission line); the first input terminal of the second-phase first-stage AC-DC converter is connected to the second-phase transmission line of the AC power grid 100 (as shown in Figure 1, phase B transmission line); and the first input terminal of the third-phase first-stage AC-DC converter is connected to the third-phase transmission line of the AC power grid 100 (as shown in Figure 1, phase C transmission line). The second input terminal of the first-phase last-stage AC-DC converter is connected to the second input terminal of the last-stage AC-DC converter of the second-phase AC-DC module and the second input terminal of the last-stage AC-DC converter of the third-phase AC-DC module. The first output terminal of each AC-DC converter is connected to the positive terminal of the DC bus 300, and the second output terminal of each AC-DC converter is connected to the negative terminal of the DC bus 300.

[0091] The first input terminal of the first phase intermediate stage AC-DC converter is connected to the second input terminal of the AC-DC converter above the first phase intermediate stage AC-DC converter, and the first input terminal of the first phase last stage AC-DC converter is connected to the second input terminal of the AC-DC converter above the first phase last stage AC-DC converter.

[0092] The first input terminal of the second phase intermediate stage AC-DC converter is connected to the second input terminal of the previous stage AC-DC converter, and the first input terminal of the first phase last stage AC-DC converter is connected to the second input terminal of the previous stage AC-DC converter.

[0093] The first input terminal of the third-phase intermediate stage AC-DC converter is connected to the second input terminal of the AC-DC converter above the third-phase intermediate stage AC-DC converter, and the first input terminal of the third-phase last stage AC-DC converter is connected to the second input terminal of the AC-DC converter above the third-phase last stage AC-DC converter.

[0094] Please refer to Figure 1. The first input terminal of AC-DC 11 is connected to the A-phase transmission line of AC power grid 100. The second input terminal of AC-DC 11 is connected to the first input terminal of AC-DC 21. The second input terminal of AC-DC 21 is connected to the first input terminal of AC-DC 31, and so on, until the second input terminal of AC-DC(n-1)1 is connected to the first input terminal of AC-DC n1. The first input terminal of AC-DC 12 is connected to the A-phase transmission line of AC power grid 100. The second input terminal of AC-DC 12 is connected to the first input terminal of AC-DC 22. The second input terminal of AC-DC 22 is connected to the first input terminal of AC-DC 32, and so on, until the second input terminal of AC-DC(n-1)2 is connected to the first input terminal of AC-DC n2. The first input terminal of AC-DC 13 is connected to the A-phase transmission line of AC power grid 100. The second input terminal of AC-DC 13 is connected to the first input terminal of AC-DC 23, the second input terminal of AC-DC 23 is connected to the first input terminal of AC-DC 33, and so on, until the second input terminal of AC-DC(n-1)3 is connected to the first input terminal of AC-DC n3. The second input terminal of AC-DC n1 is connected to the second input terminals of AC-DC n2 and AC-DC n3. The first output terminal of each AC-DC converter 210 in Figure 1 is connected to the positive terminal of DC bus 300, and the second output terminal of each AC-DC converter 210 is connected to the negative terminal of DC bus 300.

[0095] Figure 1 is a schematic diagram of the specific cascading of AC-DC converters 210 in a first-phase AC-DC module, a second-phase AC-DC module, and a third-phase AC-DC module provided in an embodiment of this application. The multiple AC-DC converters 210 in each phase AC-DC module are cascaded, which can reduce the voltage stress of the electronic switching transistors in the AC-DC converter, thereby reducing the cost of the AC-DC converter, and further reducing the cost of the AC-DC module, and thus reducing the cost of the energy storage system.

[0096] Optionally, the AC-DC converter 210 includes: a primary circuit 211, a transformer 212, and a secondary circuit 213. The primary circuit 211 includes two or three primary bridge arms, and the secondary circuit 213 includes two secondary bridge arms. The first output terminal of the AC-DC converter 210 is connected to the first ends of the two secondary bridge arms, and the second output terminal of the AC-DC converter 210 is connected to the second ends of the two secondary bridge arms. The midpoints of the two secondary bridge arms are respectively connected to the two ends of the secondary winding of the transformer 212.

[0097] When the primary circuit 211 includes two primary bridge arms, the midpoints of the two primary bridge arms are respectively adapted to connect the first input terminal and the second input terminal of the AC-DC converter 210, and the midpoints of the two primary bridge arms are respectively adapted to the two ends of the primary winding of the transformer 212.

[0098] In the case where the primary-side circuit 211 includes three primary-side bridge arms, the midpoints of two of the three primary-side bridge arms are adapted to connect the first input terminal of the AC-DC converter and the two ends of the primary winding of the transformer 212, and the midpoint of the other bridge arm is connected to the second input terminal of the AC-DC converter.

[0099] Please refer to Figure 4, which is a schematic diagram of an AC-DC converter provided in an embodiment of this application. As shown in Figure 4, the AC-DC converter 210 includes: a primary circuit 211, a transformer 212, and a secondary circuit 213. The primary circuit 211 includes three primary bridge arms, and the secondary circuit 213 includes two secondary bridge arms. The first output terminal of the AC-DC converter 210 is connected to the first ends of the two secondary bridge arms, and the second output terminal of the AC-DC converter 210 is connected to the second ends of the two secondary bridge arms. The midpoints of the two secondary bridge arms are respectively connected to the two ends of the secondary winding of the transformer 212. Two of the midpoints of the three primary bridge arms are adapted to connect the first input terminal of the AC-DC converter 210 and the two ends of the primary winding of the transformer 212, and the midpoint of the other bridge arm is connected to the second input terminal of the AC-DC converter 210.

[0100] Both the primary-side circuit 211 and the secondary-side circuit 213 in Figure 4 can include capacitors. The capacitor in the primary-side circuit 211 is used to stabilize the voltage between the first and second terminals of the primary-side bridge arm. The capacitor in the secondary-side circuit 213 is used to stabilize the voltage at the output terminal of the secondary-side circuit 213. The primary-side circuit 211 in Figure 4 also includes an inductor, which acts as a resonant element and can store energy during the switching operation of the electronic switching transistors in the primary-side bridge arm.

[0101] Two of the midpoints of the three primary-side bridge arms are adapted to connect to the first input terminal of the AC-DC converter 210. Specifically, this can include: two of the midpoints of the three primary-side bridge arms are connected to the first input terminal of the AC-DC converter 210 (as shown in Figure 4), or one of the midpoints of the three primary-side bridge arms is connected to the first input terminal of the AC-DC converter 210 through an inductor (as shown in Figure 3 or Figure 6), and the other midpoint is connected to the first input terminal of the AC-DC converter 210 through another inductor.

[0102] Please refer to Figure 5, which is a schematic diagram of an AC-DC converter provided in an embodiment of this application. As shown in Figure 5, the AC-DC converter 210 includes: a primary circuit 211, a transformer 212, and a secondary circuit 213. The primary circuit 211 includes two primary bridge arms, and the secondary circuit 213 includes two secondary bridge arms. The first output terminal of the AC-DC converter 210 is connected to the first ends of the two secondary bridge arms, and the second output terminal of the AC-DC converter 210 is connected to the second ends of the two secondary bridge arms. The midpoints of the two secondary bridge arms are respectively connected to the two ends of the secondary winding of the transformer 212. The midpoints of the two primary bridge arms are respectively adapted to connect to the first input terminal and the second input terminal of the AC-DC converter 210, and the midpoints of the two primary bridge arms are respectively adapted to the two ends of the primary winding of the transformer 212.

[0103] Both the primary-side circuit 211 and the secondary-side circuit 213 in Figure 5 may include capacitors. The capacitor in the primary-side circuit 211 is used to stabilize the voltage between the first and second terminals of the primary-side bridge arm. The capacitor in the secondary-side circuit 213 is used to stabilize the voltage at the output terminal of the secondary-side circuit 213. The primary-side circuit 211 in Figure 5 also includes an inductor, which acts as a resonant element and can store energy during the switching operation of the electronic switch transistor in the primary-side bridge arm.

[0104] The midpoints of the two primary-side bridge arms are respectively adapted to connect to the first input terminal and the second input terminal of the AC-DC converter 210. Specifically, this may include: two of the midpoints of the two primary-side bridge arms are respectively connected to the first input terminal (as shown in Figure 5) and the second input terminal of the AC-DC converter 210, or one of the midpoints of the two primary-side bridge arms is connected to the first input terminal of the AC-DC converter 210 through an inductor (as shown in Figure 7), and the other midpoint is connected to the second input terminal of the AC-DC converter 210.

[0105] Optionally, referring to Figure 3, when the primary-side circuit 211 includes three primary-side bridge arms, the primary-side circuit 211 includes: a first primary-side bridge arm, a second primary-side bridge arm, a third primary-side bridge arm, a first inductor, a second inductor, a third inductor, and a first capacitor; the secondary-side circuit 213 includes: a first secondary-side bridge arm, a second secondary-side bridge arm, and a second capacitor; the first end of the first primary-side bridge arm is connected to the first end of the second primary-side bridge arm, the first end of the third primary-side bridge arm, and the first end of the first capacitor; the second end of the first primary-side bridge arm is connected to the second end of the second primary-side bridge arm, the second end of the third primary-side bridge arm, and the second end of the first capacitor.

[0106] The first input terminal of the AC-DC converter is connected to the first terminal of the first inductor and the first terminal of the second inductor. The second terminal of the first inductor is connected to the midpoint of the first primary bridge arm and the first terminal of the third inductor. The second terminal of the third inductor is connected to the first terminal of the primary winding of the transformer 212. The second terminal of the second inductor is connected to the midpoint of the second primary bridge arm and the second terminal of the primary winding of the transformer 212. The second input terminal of the AC-DC converter is connected to the midpoint of the third primary bridge arm.

[0107] The first output terminal of the AC-DC converter is connected to the first end of the first secondary bridge arm, the first end of the second secondary bridge arm, and the first end of the second capacitor. The second output terminal of the AC-DC converter is connected to the second end of the first secondary bridge arm, the second end of the second secondary bridge arm, and the second end of the second capacitor. The midpoint of the first secondary bridge arm is connected to the first end of the secondary winding of the transformer 212, and the midpoint of the second secondary bridge arm is connected to the second end of the secondary winding of the transformer 212.

[0108] In Figure 3, an AC-DC converter includes 10 electronic switches. Compared with Figure 2, each AC-DC converter can save 2 electronic switches, thereby reducing the number of electronic switches used in the AC-DC converter, reducing the cost of the AC-DC converter, and thus reducing the cost of the energy storage system.

[0109] It should be noted that the first inductor, second inductor, third inductor, first capacitor, and second capacitor in Figure 3 can be omitted as needed.

[0110] Optionally, please refer to Figure 6, which is a schematic diagram of the specific structure of an AC-DC converter provided in an embodiment of this application. As shown in Figure 6, when the primary-side circuit 211 includes three primary-side bridge arms, the primary-side circuit 211 includes: a first primary-side bridge arm, a second primary-side bridge arm, a third primary-side bridge arm, a first inductor, a second inductor, a third inductor, a first capacitor, and a third capacitor. The secondary-side circuit 213 includes: a first secondary-side bridge arm, a second secondary-side bridge arm, and a second capacitor. The first end of the first primary-side bridge arm is connected to the first end of the second primary-side bridge arm, the first end of the third primary-side bridge arm, and the first end of the first capacitor. The second end of the first primary-side bridge arm is connected to the second end of the second primary-side bridge arm, the second end of the third primary-side bridge arm, and the second end of the first capacitor.

[0111] The first input terminal of the AC-DC converter is connected to the first terminal of the first inductor and the first terminal of the second inductor. The second terminal of the first inductor is connected to the midpoint of the first primary bridge arm and the first terminal of the third inductor. The second terminal of the third inductor is connected to the first terminal of the primary winding of the transformer 212. The second terminal of the second inductor is connected to the first terminal of the third capacitor and the midpoint of the second primary bridge arm. The second terminal of the third capacitor is connected to the second terminal of the primary winding of the transformer 212. The second input terminal of the AC-DC converter is connected to the midpoint of the third primary bridge arm.

[0112] The first output terminal of the AC-DC converter is connected to the first end of the first secondary bridge arm, the first end of the second secondary bridge arm, and the first end of the second capacitor. The second output terminal of the AC-DC converter is connected to the second end of the first secondary bridge arm, the second end of the second secondary bridge arm, and the second end of the second capacitor. The midpoint of the first secondary bridge arm is connected to the first end of the secondary winding of the transformer 212, and the midpoint of the second secondary bridge arm is connected to the second end of the secondary winding of the transformer 212.

[0113] In Figure 6, an AC-DC converter 210 includes 10 electronic switches. Compared to Figure 2, each AC-DC converter saves 2 electronic switches, thus reducing the number of electronic switches used in the AC-DC converter, lowering its cost, and consequently reducing the cost of the energy storage system. Compared to Figure 3, the AC-DC converter in Figure 6 adds a capacitor, improving its DC isolation performance. The architecture in Figure 3 offers a wider output voltage range, for example, 500V-1000V. The architecture in Figure 6 offers a narrower output voltage range, for example, 600-900V. Different architectures can be selected based on the specific application environment.

[0114] It should be noted that the first inductor, second inductor, third inductor, first capacitor, second capacitor, and third capacitor in Figure 6 can be omitted as needed.

[0115] Optionally, please refer to Figure 7, which is a schematic diagram of the specific structure of an AC-DC converter provided in an embodiment of this application. As shown in Figure 7, when the primary-side circuit 211 includes two primary-side bridge arms, the primary-side circuit 211 includes: a first primary-side bridge arm, a second primary-side bridge arm, a first inductor, a second inductor, and a first capacitor. The secondary-side circuit 213 includes: a first secondary-side bridge arm, a second secondary-side bridge arm, and a second capacitor. The first end of the first primary-side bridge arm is connected to the first end of the second primary-side bridge arm and the first end of the first capacitor, and the second end of the first primary-side bridge arm is connected to the second end of the second primary-side bridge arm and the second end of the first capacitor.

[0116] The first input terminal of the AC-DC converter 210 is connected to the first terminal of the first inductor, the second terminal of the first inductor is connected to the midpoint of the first primary bridge arm and the first terminal of the second inductor, the second terminal of the second inductor is connected to the first terminal of the primary winding of the transformer 212, and the second input terminal of the AC-DC converter 210 is connected to the midpoint of the second primary bridge arm and the second terminal of the primary winding of the transformer 212.

[0117] The first output terminal of the AC-DC converter 210 is connected to the first end of the first secondary bridge arm, the first end of the second secondary bridge arm, and the first end of the second capacitor. The second output terminal of the AC-DC converter 210 is connected to the second end of the first secondary bridge arm, the second end of the second secondary bridge arm, and the second end of the second capacitor. The midpoint of the first secondary bridge arm is connected to the first end of the secondary winding of the transformer 212, and the midpoint of the second secondary bridge arm is connected to the second end of the secondary winding of the transformer 212.

[0118] In Figure 7, an AC-DC converter includes 10 electronic switches. Compared with Figure 2, each AC-DC converter can save 2 electronic switches, thereby reducing the number of electronic switches used in the AC-DC converter, reducing the cost of the AC-DC converter, and thus reducing the cost of the energy storage system. Compared with Figures 3 and 6, Figure 7 uses fewer inductors, which can reduce the size of the AC-DC converter.

[0119] It should be noted that the first inductor, the second inductor, the first capacitor, and the second capacitor in Figure 7 can be omitted as needed.

[0120] The AC-DC converter in the energy storage system shown in Figure 1 can be any one of the types shown in Figures 3, 4, 5, 6, and 7. The AC-DC converter in the energy storage system shown in Figure 1 can be any one of the above types, or a combination of at least two of them; this application does not limit the specific type.

[0121] Please refer to Figure 8, which is a schematic diagram of the specific structure of an energy storage system provided in an embodiment of this application. Each AC-DC converter in Figure 8 is based on an example from Figure 3.

[0122] Please refer to Figure 9, which is a schematic diagram of another energy storage system provided in an embodiment of this application. Each AC-DC converter in Figure 9 is based on an example from Figure 3.

[0123] It should be noted that each AC-DC converter 210 in Figure 8 contains 3 inductors. In Figure 9, only the first stage AC-DC converter 210 of each phase contains 3 inductors; the other AC-DC converters 210 contain 2 inductors each. Compared to Figure 8, Figure 9 can use fewer inductors, thereby reducing the size of the energy storage system.

[0124] Figures 8 and 9 can be used for different application scenarios. Figure 8 can be used for scenarios with higher requirements for output voltage ripple. Figure 9 can be used for scenarios with smaller size.

[0125] Compared to Figure 9, the inductance of each inductor in Figure 8 can be smaller. For example, the inductance of each inductor in Figure 8 is 10 microhenries (µH), while the inductance at the input of the first stage AC-DC converter 210 in each phase of Figure 9 can be 100µH. Because each inductor in Figure 8 is smaller, the current ripple at the output of Figure 8 is smaller than that in Figure 9, resulting in a smoother output.

[0126] Please refer to Figure 10, which is a structural schematic diagram of a charging station provided in an embodiment of this application. As shown in Figure 10, the charging station may include an energy storage system as shown in Figure 1, Figure 8, or Figure 9.

[0127] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0128] In the several embodiments provided in this application, it should be understood that the disclosed energy storage system can be implemented in other ways. For example, the energy storage system embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed.

[0129] The terms "an embodiment," "embodiment," or "one or more embodiments" as used herein mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of this application. Furthermore, please note that the examples of the phrase "in one embodiment" do not necessarily all refer to the same embodiment.

[0130] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of this application may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0131] In the claims, any reference signs placed between parentheses should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

[0132] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. An energy storage system, characterized in that, It includes an AC power grid (100), an AC-DC system (200), and a DC bus (300); the input terminal of the AC-DC system (200) is connected to the AC power grid (100), the output terminal of the AC-DC system (200) is connected to the DC bus (300), and the AC-DC system (200) supplies power to the load through the DC bus (300); The AC-DC system (200) includes N cascaded AC-DC converters (210), each AC-DC converter (210) adopting a single-stage structure, where N is an integer greater than or equal to 2.

2. The energy storage system according to claim 1, characterized in that, The AC-DC system (200) includes multiple AC-DC modules; each AC-DC module includes n1 cascaded AC-DC converters (210); n1 is an integer greater than or equal to 2; The input terminal of each AC-DC module is connected to one phase of the three-phase transmission line of the AC power grid (100), and the output terminal of each AC-DC module is connected to the DC bus (300).

3. The energy storage system according to claim 2, characterized in that, In each AC-DC module, the primary sides of the n1 cascaded AC-DC converters (210) are connected in series, and the secondary sides of the n1 cascaded AC-DC converters (210) are connected in parallel.

4. The energy storage system according to claim 1 or 2, characterized in that, At least a portion of the AC-DC converter (210) is connected in series between any two phase transmission lines of the AC power grid (100).

5. The energy storage system according to claim 2 or 3, characterized in that, Each AC-DC converter (210) includes a first input terminal, a second input terminal, a first output terminal, and a second output terminal; each AC-DC module's AC-DC converter (210) includes: a first-stage AC-DC converter, at least one intermediate-stage AC-DC converter, and a last-stage AC-DC converter; In this configuration, the first input terminal of the first stage AC-DC converter of each AC-DC module is connected to one phase of the three-phase transmission line of the AC power grid (100), and the second input terminal of the last stage AC-DC converter of each AC-DC module is connected to the same phase; the first output terminal of each AC-DC converter (210) is connected to the positive terminal of the DC bus (300), and the second output terminal of each AC-DC converter (210) is connected to the negative terminal of the DC bus (300); In each AC-DC module, the first input terminal of the intermediate stage AC-DC converter is connected to the second input terminal of the AC-DC converter of the previous stage; the first input terminal of the last stage AC-DC converter is connected to the second input terminal of the AC-DC converter of the previous stage.

6. The energy storage system according to claim 5, characterized in that, The plurality of AC-DC modules include a first-phase AC-DC module, a second-phase AC-DC module, and a third-phase AC-DC module. The first-phase AC-DC module includes: a first-phase first-stage AC-DC converter, a first-phase intermediate-stage AC-DC converter, and a first-phase last-stage AC-DC converter. The second-phase AC-DC module includes: a second-phase first-stage AC-DC converter, a second-phase intermediate-stage AC-DC converter, and a second-phase last-stage AC-DC converter. The third-phase AC-DC module includes: a third-phase first-stage AC-DC converter, a third-phase intermediate-stage AC-DC converter, and a third-phase last-stage AC-DC converter. Wherein, the first input terminal of the first-stage AC-DC converter of the first phase is connected to the first phase transmission line of the AC power grid (100), the first input terminal of the first-stage AC-DC converter of the second phase is connected to the second phase transmission line of the AC power grid (100), and the first input terminal of the first-stage AC-DC converter of the third phase is connected to the third phase transmission line of the AC power grid (100); the second input terminal of the last stage AC-DC converter of the first phase is connected to the second input terminal of the last stage AC-DC converter of the second phase AC-DC module and the second input terminal of the last stage AC-DC converter of the third phase AC-DC module; the first output terminal of each AC-DC converter (210) is connected to the positive terminal of the DC bus (300), and the second output terminal of each AC-DC converter (210) is connected to the negative terminal of the DC bus (300); The first input terminal of the first phase intermediate stage AC-DC converter is connected to the second input terminal of the AC-DC converter above the first phase intermediate stage AC-DC converter, and the first input terminal of the first phase last stage AC-DC converter is connected to the second input terminal of the AC-DC converter above the first phase last stage AC-DC converter. The first input terminal of the second phase intermediate stage AC-DC converter is connected to the second input terminal of the previous stage AC-DC converter, and the first input terminal of the second phase last stage AC-DC converter is connected to the second input terminal of the previous stage AC-DC converter. The first input terminal of the third-phase intermediate stage AC-DC converter is connected to the second input terminal of the AC-DC converter above the third-phase intermediate stage AC-DC converter, and the first input terminal of the third-phase last stage AC-DC converter is connected to the second input terminal of the AC-DC converter above the third-phase last stage AC-DC converter.

7. The energy storage system according to any one of claims 1 to 6, characterized in that, The AC-DC converter (210) includes a primary circuit (211), a transformer (212), and a secondary circuit (213). The primary circuit (211) includes two or three primary bridge arms, and the secondary circuit (213) includes two secondary bridge arms. The first output terminal of the AC-DC converter (210) is connected to the first end of the two secondary bridge arms, and the second output terminal of the AC-DC converter (210) is connected to the second end of the two secondary bridge arms. The midpoints of the two secondary bridge arms are respectively connected to the two ends of the secondary winding of the transformer (212). When the primary circuit (211) includes two primary bridge arms, the midpoints of the two primary bridge arms are respectively adapted to connect the first input terminal and the second input terminal of the AC-DC converter (210), and the midpoints of the two primary bridge arms are respectively adapted to the two ends of the primary winding of the transformer (212). In the case where the primary-side circuit (211) includes three primary-side bridge arms, the midpoints of two of the three primary-side bridge arms are adapted to connect the first input terminal of the AC-DC converter (210) and the two ends of the primary winding of the transformer (212), and the midpoint of the other bridge arm is connected to the second input terminal of the AC-DC converter (210).

8. The energy storage system according to claim 7, characterized in that, When the primary-side circuit (211) includes three primary-side bridge arms, the primary-side circuit (211) includes: a first primary-side bridge arm, a second primary-side bridge arm, and a third primary-side bridge arm, and the secondary-side circuit (213) includes: a first secondary-side bridge arm and a second secondary-side bridge arm; the first end of the first primary-side bridge arm is connected to the first end of the second primary-side bridge arm and the first end of the third primary-side bridge arm, and the second end of the first primary-side bridge arm is connected to the second end of the second primary-side bridge arm and the second end of the third primary-side bridge arm; The first input terminal of the AC-DC converter (210) is adapted to connect the midpoint of the first primary bridge arm and the midpoint of the second primary bridge arm. The midpoint of the first primary bridge arm is adapted to connect the first end of the primary winding of the transformer (212). The midpoint of the second primary bridge arm is adapted to connect the second end of the primary winding of the transformer (212). The second input terminal of the AC-DC converter (210) is connected to the midpoint of the third primary bridge arm. The first output terminal of the AC-DC converter (210) is connected to the first end of the first secondary bridge arm and the first end of the second secondary bridge arm. The second output terminal of the AC-DC converter (210) is connected to the second end of the first secondary bridge arm and the second end of the second secondary bridge arm. The midpoint of the bridge arm of the first secondary bridge arm is connected to the first end of the secondary winding of the transformer (212). The midpoint of the bridge arm of the second secondary bridge arm is connected to the second end of the secondary winding of the transformer (212).

9. The energy storage system according to claim 8, characterized in that, The primary-side circuit (211) further includes a first inductor, a second inductor, a third inductor, and a first capacitor; the secondary-side circuit (213) further includes a second capacitor; the first end of the first primary-side bridge arm is connected to the first end of the first capacitor, and the second end of the first primary-side bridge arm is connected to the second end of the first capacitor. The first input terminal of the AC-DC converter (210) is connected to the first terminal of the first inductor and the first terminal of the second inductor. The second terminal of the first inductor is connected to the midpoint of the first primary bridge arm and the first terminal of the third inductor. The second terminal of the third inductor is connected to the first terminal of the primary winding of the transformer (212). The second terminal of the second inductor is connected to the midpoint of the second primary bridge arm and the second terminal of the primary winding of the transformer (212). The first output terminal of the AC-DC converter (210) is connected to the first terminal of the second capacitor, and the second output terminal of the AC-DC converter (210) is connected to the second terminal of the second capacitor.

10. The energy storage system according to claim 7, characterized in that, When the primary-side circuit (211) includes three primary-side bridge arms, the primary-side circuit (211) includes: a first primary-side bridge arm, a second primary-side bridge arm, and a third primary-side bridge arm, and the secondary-side circuit (213) includes: a first secondary-side bridge arm and a second secondary-side bridge arm; the first end of the first primary-side bridge arm is connected to the first end of the second primary-side bridge arm and the first end of the third primary-side bridge arm, and the second end of the first primary-side bridge arm is connected to the second end of the second primary-side bridge arm and the second end of the third primary-side bridge arm; The first input terminal of the AC-DC converter (210) is adapted to be connected to the midpoint of the first primary side bridge arm, the midpoint of the first primary side bridge arm is adapted to be connected to the first end of the primary winding of the transformer (212), the midpoint of the second primary side bridge arm is adapted to be connected to the second end of the primary winding of the transformer (212), and the second input terminal of the AC-DC converter (210) is connected to the midpoint of the third primary side bridge arm. The first output terminal of the AC-DC converter (210) is connected to the first end of the first secondary bridge arm and the first end of the second secondary bridge arm. The second output terminal of the AC-DC converter (210) is connected to the second end of the first secondary bridge arm and the second end of the second secondary bridge arm. The midpoint of the bridge arm of the first secondary bridge arm is connected to the first end of the secondary winding of the transformer (212). The midpoint of the bridge arm of the second secondary bridge arm is connected to the second end of the secondary winding of the transformer (212).

11. The energy storage system according to claim 10, characterized in that, The primary-side circuit (211) further includes a first inductor, a second inductor, a third inductor, a first capacitor, and a third capacitor; the secondary-side circuit (213) further includes a second capacitor; the first end of the first primary-side bridge arm is connected to the first end of the first capacitor, and the second end of the first primary-side bridge arm is connected to the second end of the first capacitor. The first input terminal of the AC-DC converter (210) is connected to the first terminal of the first inductor and the first terminal of the second inductor. The second terminal of the first inductor is connected to the midpoint of the first primary bridge arm and the first terminal of the third inductor. The second terminal of the third inductor is connected to the first terminal of the primary winding of the transformer (212). The second terminal of the second inductor is connected to the first terminal of the third capacitor and the midpoint of the second primary bridge arm. The second terminal of the third capacitor is connected to the second terminal of the primary winding of the transformer (212). The first output terminal of the AC-DC converter (210) is connected to the first terminal of the second capacitor, and the second output terminal of the AC-DC converter (210) is connected to the second terminal of the second capacitor.

12. The energy storage system according to claim 7, characterized in that, When the primary-side circuit (211) includes two primary-side bridge arms, the primary-side circuit (211) includes: a first primary-side bridge arm and a second primary-side bridge arm, and the secondary-side circuit (213) includes: a first secondary-side bridge arm and a second secondary-side bridge arm; the first end of the first primary-side bridge arm is connected to the first end of the second primary-side bridge arm, and the second end of the first primary-side bridge arm is connected to the second end of the second primary-side bridge arm; The first input terminal of the AC-DC converter (210) is adapted to be connected to the midpoint of the first primary bridge arm, the midpoint of the first primary bridge arm is adapted to be connected to the first end of the primary winding of the transformer (212), and the second input terminal of the AC-DC converter (210) is connected to the midpoint of the second primary bridge arm and the second end of the primary winding of the transformer (212). The first output terminal of the AC-DC converter (210) is connected to the first end of the first secondary bridge arm and the first end of the second secondary bridge arm. The second output terminal of the AC-DC converter (210) is connected to the second end of the first secondary bridge arm and the second end of the second secondary bridge arm. The midpoint of the bridge arm of the first secondary bridge arm is connected to the first end of the secondary winding of the transformer (212). The midpoint of the bridge arm of the second secondary bridge arm is connected to the second end of the secondary winding of the transformer (212).

13. The energy storage system according to claim 12, characterized in that, The primary-side circuit (211) further includes a first inductor, a second inductor, a third inductor, and a first capacitor; the secondary-side circuit (213) further includes a second capacitor; the first end of the first primary-side bridge arm is connected to the first end of the first capacitor, and the second end of the first primary-side bridge arm is connected to the second end of the first capacitor. The first input terminal of the AC-DC converter (210) is connected to the first terminal of the first inductor, the second terminal of the first inductor is connected to the midpoint of the first primary side bridge arm and the first terminal of the second inductor, and the second terminal of the second inductor is connected to the first terminal of the primary winding of the transformer (212). The first output terminal of the AC-DC converter (210) is connected to the first terminal of the second capacitor, and the second output terminal of the AC-DC converter (210) is connected to the second terminal of the second capacitor.

14. The energy storage system according to any one of claims 1 to 13, characterized in that, The load includes: an electric vehicle (600) or an energy storage device (500).

15. The energy storage system according to any one of claims 1 to 14, characterized in that, The energy storage system also includes a photovoltaic module (400), and the DC bus (300) is connected to the photovoltaic module (400) via a DC-DC module.

16. A charging station, characterized in that, Including the energy storage system as described in any one of claims 1 to 15.

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