Energy storage system and charging station

Abstract

The embodiment of the invention provides an energy storage system and a charging station. The energy storage system comprises an AC power grid, an AC-DC system and a DC bus. The input end of the AC-DC system is connected with an AC power grid, the output end of the AC-DC system is connected with a DC bus, and the DC bus supplies power to a load; the AC-DC system comprises N cascaded AC-DC converters, each AC-DC converter adopts a single-stage structure, and N is an integer greater than or equal to 2. The cost of the energy storage system can be reduced.

Description

Technical Field

[0001] The present application relates to the field of electronic circuit technology, and in particular to an energy storage system and a charging station. Background Art

[0002] There are two main transformer isolation schemes for current energy storage systems. The first is to convert the 10kV AC power of the power grid into 380V through an industrial frequency transformer, and then convert it into high-voltage DC (for example, 800V DC) through an alternating current-direct current (AC-DC) module. The second is to convert the 10kV AC power of the power grid into high-voltage DC through a high-frequency converter. Due to the small size of the high-frequency converter, the volume of the entire energy storage system can be reduced. However, the current high-frequency converter adopts a two-stage structure and uses a large number of electronic switching tubes, which makes the cost of the energy storage system higher. Summary of the invention

[0003] The embodiments of the present application provide an energy storage system and a charging station, which can reduce the cost of the energy storage system.

[0004] A first aspect of an embodiment of the present application provides an energy storage system, including an AC power grid, an AC-DC system, and a DC bus; an input end of the AC-DC system is connected to the AC power grid, an output end of the AC-DC system is connected to the DC bus, and the AC-DC system supplies power to a load through the DC bus;

[0005] The AC-DC system includes N cascaded AC-DC converters, the AC-DC converters adopt a single-stage structure, and N is an integer greater than or equal to 2.

[0006] Optionally, the AC-DC system includes a plurality of AC-DC modules;

[0007] Each AC-DC module includes n1 cascaded AC-DC converters; n1 is an integer greater than or equal to 2;

[0008] The input end of each AC-DC module is connected to one phase of the three-phase transmission line of the AC power grid, and the output end of each AC-DC module is connected to the DC bus.

[0009] Optionally, in each of the AC-DC modules, the primary sides of the n1 cascaded AC-DC converters are connected in series in sequence, and the secondary sides of the n1 cascaded AC-DC converters are connected in parallel.

[0010] Optionally, at least part of the AC-DC converter is connected in series between any two-phase transmission lines of the AC power grid.

[0011] 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 of the AC-DC modules includes: a first-stage AC-DC converter, at least one intermediate-stage AC-DC converter and a last-stage AC-DC converter;

[0012] Wherein, the first input end of the first-stage AC-DC converter of each of the AC-DC modules is connected to one phase of the three-phase transmission line of the AC power grid, and the second input ends of the last-stage AC-DC converters of each of the AC-DC modules are connected in common; the first output end of each AC-DC converter is connected to the positive pole of the DC bus, and the second output end of each AC-DC converter is connected to the negative pole of the DC bus;

[0013] In each of the AC-DC modules, the first input end of the intermediate-stage AC-DC converter is connected to the second input end of the AC-DC converter of the previous stage of the intermediate-stage AC-DC converter; the first input end of the last-stage AC-DC converter is connected to the second input end of the AC-DC converter of the previous stage of the last-stage AC-DC converter.

[0014] Optionally, the multiple 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-level AC-DC converter, a first-phase intermediate-level AC-DC converter and a first-phase last-level AC-DC converter; the second-phase AC-DC module includes: a second-phase first-level AC-DC converter, a second-phase intermediate-level AC-DC converter and a second-phase last-level AC-DC converter; the third-phase AC-DC module includes: a third-phase first-level AC-DC converter, a third-phase intermediate-level AC-DC converter and a third-phase last-level AC-DC converter;

[0015] Wherein, the first input end of the first-stage AC-DC converter of the first phase is connected to the first-phase transmission line of the AC power grid, the first input end of the first-stage AC-DC converter of the second phase is connected to the second-phase transmission line of the AC power grid, and the first input end of the first-stage AC-DC converter of the third phase is connected to the third-phase transmission line of the AC power grid; the second input end of the last-stage AC-DC converter of the first phase is connected to the second input end of the last-stage AC-DC converter of the second-phase AC-DC module and the second input end of the last-stage AC-DC converter of the third-phase AC-DC module; the first output end of each AC-DC converter is connected to the positive pole of the DC bus, and the second output end of each AC-DC converter is connected to the negative pole of the DC bus;

[0016] The first input end of the first-phase intermediate-stage AC-DC converter is connected to the second input end of the previous-stage AC-DC converter of the first-phase intermediate-stage AC-DC converter, and the first input end of the first-phase last-stage AC-DC converter is connected to the second input end of the previous-stage AC-DC converter of the first-phase last-stage AC-DC converter;

[0017] The first input end of the second-phase intermediate-stage AC-DC converter is connected to the second input end of the previous-stage AC-DC converter of the second-phase intermediate-stage AC-DC converter, and the first input end of the second-phase last-stage AC-DC converter is connected to the second input end of the previous-stage AC-DC converter of the second-phase last-stage AC-DC converter;

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

[0019] Optionally, the AC-DC converter includes: a primary circuit, a transformer and a secondary circuit, the primary circuit includes two primary bridge arms or three primary bridge arms, and the secondary circuit includes two secondary bridge arms; the first output end of the AC-DC converter is connected to the first ends of the two secondary bridge arms, the second output end of the AC-DC converter is connected to the second ends of the two secondary bridge arms, and the midpoints of the two secondary bridge arms are respectively connected to the two ends of the secondary winding of the transformer;

[0020] In the case where the primary circuit includes two primary bridge arms, the midpoints of the two primary bridge arms are respectively suitable for connecting 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 suitable for connecting the two ends of the primary winding of the transformer;

[0021] In the case where the primary circuit includes three primary bridge arms, two of the three primary bridge arms' midpoints are suitable for connecting the first input terminal of the AC-DC converter and the two ends of the primary winding of the transformer, and the other bridge arm midpoint is connected to the second input terminal of the AC-DC converter.

[0022] Optionally, in the case where the primary circuit includes three primary bridge arms, the primary circuit includes: a first primary bridge arm, a second primary bridge arm, and a third primary bridge arm, and the secondary circuit includes: a first secondary bridge arm and a second secondary bridge arm; the first end of the first primary bridge arm is connected to the first end of the second primary bridge arm and the first end of the third primary bridge arm, and the second end of the first primary bridge arm is connected to the second end of the second primary bridge arm and the second end of the third primary bridge arm;

[0023] The first input end of the AC-DC converter is suitable for connecting the bridge arm midpoint of the first primary bridge arm and the bridge arm midpoint of the second primary bridge arm, the bridge arm midpoint of the first primary bridge arm and the bridge arm midpoint of the second primary bridge arm are suitable for connecting the first end of the primary winding of the transformer, the bridge arm midpoint of the second primary bridge arm is suitable for connecting the second end of the primary winding of the transformer, and the second input end of the AC-DC converter is connected to the bridge arm midpoint of the third primary bridge arm;

[0024] The first output end 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 end 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.

[0025] Optionally, the primary circuit further includes a first inductor, a second inductor, a third inductor and a first capacitor, and the secondary circuit further includes a second capacitor; the first end of the first primary bridge arm is connected to the first end of the first capacitor, and the second end of the first primary bridge arm is connected to the second end of the first capacitor;

[0026] The first input end of the AC-DC converter is connected to the first end of the first inductor and the first end of the second inductor, the second end of the first inductor is connected to the midpoint of the first primary bridge arm and the first end of the third inductor, the second end of the third inductor is connected to the first end of the primary winding of the transformer, and the second end of the second inductor is connected to the midpoint of the second primary bridge arm and the second end of the primary winding of the transformer;

[0027] The first output end of the AC-DC converter is connected to the first end of the second capacitor, and the second output end of the AC-DC converter is connected to the second end of the second capacitor.

[0028] Optionally, in the case where the primary circuit includes three primary bridge arms, the primary circuit includes: a first primary bridge arm, a second primary bridge arm and a third primary bridge arm, and the secondary circuit includes: a first secondary bridge arm and a second secondary bridge arm; the first end of the first primary bridge arm is connected to the first end of the second primary bridge arm and the first end of the third primary bridge arm, and the second end of the first primary bridge arm is connected to the second end of the second primary bridge arm and the second end of the third primary bridge arm;

[0029] The first input end of the AC-DC converter is suitable for connecting to the bridge arm midpoint of the first primary bridge arm, the bridge arm midpoint of the first primary bridge arm is suitable for connecting to the first end of the primary winding of the transformer, the bridge arm midpoint of the second primary bridge arm is suitable for connecting to the second end of the primary winding of the transformer, and the second input end of the AC-DC converter is connected to the bridge arm midpoint of the third primary bridge arm;

[0030] The first output end 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 end 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.

[0031] Optionally, the primary circuit further includes a first inductor, a second inductor, a third inductor, a first capacitor and a third capacitor, and the secondary circuit further includes a second capacitor; the first end of the first primary bridge arm is connected to the first end of the first capacitor, and the second end of the first primary bridge arm is connected to the second end of the first capacitor;

[0032] The first input end of the AC-DC converter is connected to the first end of the first inductor and the first end of the second inductor, the second end of the first inductor is connected to the midpoint of the first primary bridge arm and the first end of the third inductor, the second end of the third inductor is connected to the first end of the primary winding of the transformer, the second end of the second inductor is connected to the first end of the third capacitor and the midpoint of the second primary bridge arm, and the second end of the third capacitor is connected to the second end of the primary winding of the transformer;

[0033] The first output end of the AC-DC converter is connected to the first end of the second capacitor, and the second output end of the AC-DC converter is connected to the second end of the second capacitor.

[0034] Optionally, in the case where the primary circuit includes two primary bridge arms, the primary circuit includes: a first primary bridge arm and a second primary bridge arm, and the secondary circuit includes: a first secondary bridge arm and a second secondary bridge arm; the first end of the first primary bridge arm is connected to the first end of the second primary bridge arm, and the second end of the first primary bridge arm is connected to the second end of the second primary bridge arm;

[0035] The first input end of the AC-DC converter is suitable for connecting the bridge arm midpoint of the first primary bridge arm, the bridge arm midpoint of the first primary bridge arm is suitable for connecting the first end of the primary winding of the transformer, and the second input end of the AC-DC converter is connected to the bridge arm midpoint of the second primary bridge arm and the second end of the primary winding of the transformer;

[0036] The first output end 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 end 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.

[0037] The primary circuit further includes a first inductor, a second inductor, a third inductor and a first capacitor, and the secondary circuit further includes a second capacitor; the first end of the first primary bridge arm is connected to the first end of the first capacitor, and the second end of the first primary bridge arm is connected to the second end of the first capacitor;

[0038] The first input end of the AC-DC converter is connected to the first end of the first inductor, the second end of the first inductor is connected to the bridge arm midpoint of the first primary bridge arm and the first end of the second inductor, and the second end of the second inductor is connected to the first end of the primary winding of the transformer;

[0039] The first output end of the AC-DC converter is connected to the first end of the second capacitor, and the second output end of the AC-DC converter is connected to the second end of the second capacitor.

[0040] Optionally, the load includes: an electric vehicle or an energy storage device.

[0041] Optionally, the energy storage system further includes a photovoltaic component, and the DC bus is connected to the photovoltaic component via a DC-DC module.

[0042] A second aspect of an embodiment of the present application provides a charging station, comprising the energy storage system described in the first aspect.

[0043] The energy storage system of the embodiment of the present application includes an AC power grid, an AC-DC system, and a DC bus; the input end of the AC-DC system is connected to the AC power grid, the output end 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; the AC-DC system includes N cascaded AC-DC converters, the AC-DC converter adopts a single-stage structure, and N is an integer greater than or equal to 2. Each AC-DC converter in the AC-DC system adopts a single-stage structure, and compared with a two-stage structure, fewer electronic switch tubes are used, thereby reducing the cost of the energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0045] Figure 1 is a structural schematic diagram of an energy storage system provided in an embodiment of the present application;

[0046] Figure 2 An AC-DC converter with a two-stage structure is provided in an embodiment of the present application;

[0047] Figure 3 An AC-DC converter with a single-stage structure is provided in an embodiment of the present application;

[0048] Figure 4 is a schematic diagram of the structure of an AC-DC converter provided in an embodiment of the present application;

[0049] Figure 5 is a schematic diagram of the structure of an AC-DC converter provided in an embodiment of the present application;

[0050] Figure 6 is a specific structural diagram of an AC-DC converter provided in an embodiment of the present application;

[0051] Figure 7 is a specific structural diagram of an AC-DC converter provided in an embodiment of the present application;

[0052] Figure 8 is a specific structural diagram of an energy storage system provided in an embodiment of the present application;

[0053] Fig. 9 is a specific structural schematic diagram of another energy storage system provided in an embodiment of the present application;

[0054] Fig.10It is a structural schematic diagram of a charging station provided in an embodiment of the present application. DETAILED DESCRIPTION

[0055] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of this application.

[0056] The terms "first", "second", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, products or devices.

[0057] Reference to "embodiments" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments.

[0058] See also Figure 1 , Figure 1 Schematic diagram of the structure of an energy storage system provided in an embodiment of the present application. Figure 1 As shown, the energy storage system includes an AC power grid, an AC-DC system, and a DC bus; the input end of the AC-DC system is connected to the AC power grid, the output end 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;

[0059] The AC-DC system includes N cascaded AC-DC converters (such as Figure 1 As shown in the 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), the AC-DC converter adopts a single-stage structure, and N is an integer greater than or equal to 2.

[0060] In the embodiment of the present application, the alternating current on the AC power grid can be any one of 380V, 660V, 1000V, 3kV, 6kV, 10kV, 35kV, 66kV, 110kV, 220kV, 330kV, 500kV, 750kV, and 1000kV. The voltage of the DC bus can be 800V or 650V. The alternating current-direct current (AC-DC) system can convert the alternating current into direct current. For example, the alternating current on the AC power grid is 10 kilovolts (kV), and the AC-DC system can convert the 10kV alternating current into 800V direct current, and output 800V direct current to the DC bus.

[0061] The traditional AC-DC converter adopts a two-stage structure, and the AC-DC converter includes an AC-DC unit and a DC-DC unit. The AC-DC unit first converts the alternating current into a direct current of a certain voltage to achieve power factor correction, and then converts it into high-voltage direct current through the DC-DC unit. The AC-DC converter of the embodiment of the present application adopts a single-stage structure. The single-stage converter structure combines the AC-DC unit and the DC-DC unit into one, and is no longer a two-stage conversion structure. Compared with the traditional AC-DC converter with a two-stage structure, the AC-DC converter with a single-stage structure uses fewer electronic switch tubes, thereby reducing costs.

[0062] See also Figure 2 and Figure 3 , Figure 2 An AC-DC converter with a two-stage structure is provided in an embodiment of the present application. Figure 3 An AC-DC converter with a single-stage structure is provided in an embodiment of the present application. Figure 2 The AC-DC converter shown includes a two-stage structure consisting of an AC-DC unit and a DC-DC unit. Figure 2 The AC-DC converter shown includes 12 electronic switching tubes (the AC-DC unit includes 4 electronic switching tubes, and the DC-DC unit includes 8 electronic switching tubes). Figure 3 The AC-DC converter shown includes 10 electronic switch tubes. For an AC-DC system including N AC-DC converters, 2*N electronic switch tubes can be saved, thereby reducing the number of electronic switch tubes used in the AC-DC converter, reducing the cost of the AC-DC converter, and further reducing the cost of the energy storage system.

[0063] Optional, such as Figure 1 As shown, the energy storage system also includes a DC-DC module, and the DC bus supplies power to at least one load through the DC-DC module. The DC-DC module may include at least one DC-DC converter (such as Figure 1As shown in the DC-DC), at least one DC-DC converter corresponds to at least one load, each DC-DC converter can correspond to one load, and each DC-DC converter can supply power for the corresponding load.

[0064] Optionally, the load may include an electric vehicle or an energy storage device. The energy storage system may charge the electric vehicle and the energy storage device.

[0065] Electric vehicles are vehicles that can be driven by electricity, and electric vehicles can include power batteries. Energy storage devices are devices used to store energy, and energy storage devices can include energy storage batteries. Power batteries and energy storage batteries are not the same type of batteries. Energy storage batteries have lower energy density and longer life, and are energy-type batteries. Power batteries have higher energy density and longer battery life, and are power-type batteries.

[0066] Optionally, the energy storage system further includes a photovoltaic component, and the DC bus is connected to the photovoltaic component via a DC-DC module.

[0067] Among them, photovoltaic modules are modules that can generate electricity through solar energy. The voltage of photovoltaic modules is not the voltage of the DC bus. For example, a photovoltaic module is composed of 50 or 100 photovoltaic panels connected in series, and the output voltage is between 200V and 300V. The voltage of the DC bus is 600-800V. The photovoltaic module discharges to the DC bus through the DC-DC module. Among them, energy storage batteries and electric vehicles can be charged through the DC bus and discharged to the DC bus. For example, if an electric car requires a charging power of 500KW and the power generation power of the photovoltaic module is 100KW, the remaining 400KW is from the AC power grid, through the AC-DC system to the DC bus, and then charged to the electric car through the DC-DC module.

[0068] The power generation of photovoltaic modules may not be enough for electric vehicles. At present, the AC grid is the main source, supplemented by energy storage batteries and photovoltaic modules.

[0069] After the energy of the photovoltaic module reaches the DC bus, it can supply power to energy storage batteries and electric vehicles and be distributed according to demand.

[0070] like Figure 1 As shown, the DC-DC module may include three DC-DC converters, wherein the three DC-DC converters are respectively connected to the photovoltaic component, the energy storage device, and the electric vehicle.

[0071] It should be noted that Figure 1This is just a possible example. The number of DC-DC converters included in the DC-DC module can be greater than or equal to 2. For example, the number of photovoltaic modules connected to the DC bus is M1, the number of energy storage devices connected to the DC bus is M2, and the number of electric vehicles connected to the DC bus is M3. Then, the number of DC-DC converters that the DC-DC module can include is (M1+M2+M3).

[0072] The energy storage system of the embodiment of the present application includes an AC power grid, an AC-DC system, and a DC bus; the input end of the AC-DC system is connected to the AC power grid, the output end 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; the AC-DC system includes N cascaded AC-DC converters, the AC-DC converter adopts a single-stage structure, and N is an integer greater than or equal to 2. On the one hand, each AC-DC converter in the AC-DC system adopts a single-stage structure, and compared with a two-stage structure, fewer electronic switch tubes are used, thereby reducing the cost of the energy storage system. On the other hand, the N AC-DC converters in the AC-DC system are cascaded, which can reduce the voltage stress of the electronic switch tube in the AC-DC converter, thereby reducing the cost of the AC-DC converter, and further reducing the cost of the energy storage system.

[0073] Optionally, at least part of the AC-DC converter is connected in series between any two-phase transmission lines of the AC power grid.

[0074] In the embodiment of the present application, the AC power grid is a three-phase AC power grid, which includes a first phase transmission line (such as Figure 1 A-phase transmission line shown), the second-phase transmission line (such as Figure 1 The B-phase transmission line shown) and the third-phase transmission line (as shown Figure 1 C-phase transmission line shown).

[0075] Each of the N cascaded AC-DC converters is connected in series to the two-phase transmission line of the AC power grid. Figure 1 For example, AC-DC 11 is connected in series between the A-phase transmission line and the B-phase transmission line, or AC-DC 11 is connected in series between the A-phase transmission line and the C-phase transmission line. AC-DC 12 is connected in series between the A-phase transmission line and the B-phase transmission line, or AC-DC 12 is connected in series between the B-phase transmission line and the C-phase transmission line. AC-DC 13 is connected in series between the A-phase transmission line and the C-phase transmission line, or AC-DC 13 is connected in series between the B-phase transmission line and the C-phase transmission line.

[0076] Figure 1In the embodiment, AC-DC 11, AC-DC 21, ..., AC-DC n1 are connected in series, AC-DC 12, AC-DC 22, ..., AC-DCn2 are connected in series, and AC-DC13, AC-DC 23, ..., AC-DC n3 are connected in series, which can reduce the voltage stress of the electronic switch tube in the AC-DC converter, thereby reducing the cost of the AC-DC converter, and further reducing the cost of the energy storage system.

[0077] Optionally, in each of the AC-DC modules, the primary sides of the n1 cascaded AC-DC converters are connected in series in sequence, and the secondary sides of the n1 cascaded AC-DC converters are connected in parallel. Figure 1 As shown, the primary sides of AC-DC11, AC-DC21, ..., AC-DCn1 are connected in series in sequence, and the secondary sides of AC-DC11, AC-DC21, ..., AC-DCn1 are connected in parallel.

[0078] Wherein, in each AC-DC module, each AC-DC converter primary side includes a first input terminal and a second input terminal, and each AC-DC converter secondary side includes a first output terminal and a second output terminal. In two adjacent AC-DC converters, 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 of the current-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 of the current-stage AC-DC converter. In each AC-DC module, the first output terminal of each AC-DC converter is connected, and the second output terminal of each AC-DC converter is connected.

[0079] 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 of the AC-DC modules includes: a first-stage AC-DC converter (such as Figure 1 AC-DC 11 shown), at least one intermediate AC-DC converter (such as Figure 1 The AC-DC 21, AC-DC 31, etc. shown in FIG. 1 and the last stage AC-DC converter (such as Figure 1 AC-DCn1 shown);

[0080] Wherein, the first input end of the first-stage AC-DC converter of each of the AC-DC modules is connected to one phase of the three-phase transmission line of the AC power grid, and the second input ends of the last-stage AC-DC converters of each of the AC-DC modules are connected in common; the first output end of each AC-DC converter is connected to the positive pole of the DC bus, and the second output end of each AC-DC converter is connected to the negative pole of the DC bus;

[0081] In each of the AC-DC modules, the first input end of the intermediate-stage AC-DC converter is connected to the second input end of the AC-DC converter of the previous stage of the intermediate-stage AC-DC converter; the first input end of the last-stage AC-DC converter is connected to the second input end of the AC-DC converter of the previous stage of the last-stage AC-DC converter.

[0082] Optionally, the multiple 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 n1 cascaded AC-DC converters, the second-phase AC-DC module includes n2 cascaded AC-DC converters, 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.

[0083] In the embodiment of the present application, n1, n2, and n3 may be equal or unequal. Figure 1 Take n1, n2, and n3 as an example. Figure 1 In the equation, n1=n2=n3=n, and N=3*n.

[0084] The first phase AC-DC module includes AC-DC 11, AC-DC 21, ... AC-DC n1, a total of n cascaded AC-DC converters. The second phase AC-DC module includes AC-DC 12, AC-DC 22, ... AC-DC n2, a total of n cascaded AC-DC converters. The third phase AC-DC module includes AC-DC13, AC-DC 23, ... AC-DC n3, a total of n cascaded AC-DC converters.

[0085] An input end of the first-phase AC-DC module is connected to a first-phase transmission line of the AC power grid, an input end of the second-phase AC-DC module is connected to a second-phase transmission line of the AC power grid, an input end of the third-phase AC-DC module is connected to a third-phase transmission line of the AC power grid, and an output end of the first-phase AC-DC module, an output end of the second-phase AC-DC module, and an output end of the third-phase AC-DC module are connected to the DC bus.

[0086] The n1 cascaded AC-DC converters include: a first-stage AC-DC converter (such as Figure 1 AC-DC 11 shown), at least one intermediate AC-DC converter (such as Figure 1 The AC-DC 21, AC-DC 31, etc. shown in FIG. 1 and the last stage AC-DC converter (such as Figure 1The AC-DC converter n1 shown); the n2 cascaded AC-DC converters include: the second phase first stage AC-DC converter (such as Figure 1 AC-DC 12 shown), at least one second phase intermediate stage AC-DC converter (such as Figure 1 The AC-DC 22, AC-DC 32, etc. shown in the figure) and the last stage AC-DC converter of the second phase (such as Figure 1 The AC-DC n2 shown); the n3 cascaded AC-DC converters include: a third-phase first-stage AC-DC converter (such as Figure 1 AC-DC 13 shown), at least one third phase intermediate AC-DC converter (such as Figure 1 The AC-DC 23, AC-DC 33, etc. shown in FIG. 1 and the last AC-DC converter of the third phase (such as Figure 1 AC-DC n3) shown;

[0087] Wherein, the first input end of the first-phase first-stage AC-DC converter is connected to the first-phase transmission line of the AC power grid (such as Figure 1 The first input end of the second-phase first-stage AC-DC converter is connected to the second-phase transmission line of the AC power grid (such as Figure 1 The first input end of the third-phase first-stage AC-DC converter is connected to the third-phase transmission line of the AC power grid (such as Figure 1 The first phase AC-DC module is connected to the second input terminal of the last AC-DC converter of the second phase AC-DC module and the second input terminal of the last AC-DC converter of the third phase AC-DC module; the first output terminal of each AC-DC converter is connected to the positive pole of the DC bus, and the second output terminal of each AC-DC converter is connected to the negative pole of the DC bus;

[0088] The first input end of the first-phase intermediate-stage AC-DC converter is connected to the second input end of the previous-stage AC-DC converter of the first-phase intermediate-stage AC-DC converter, and the first input end of the first-phase last-stage AC-DC converter is connected to the second input end of the previous-stage AC-DC converter of the first-phase last-stage AC-DC converter;

[0089] The first input end of the second-phase intermediate-stage AC-DC converter is connected to the second input end of the previous-stage AC-DC converter of the second-phase intermediate-stage AC-DC converter, and the first input end of the last-stage AC-DC converter of the first phase is connected to the second input end of the previous-stage AC-DC converter of the last-stage AC-DC converter of the first phase;

[0090] The first input end of the third-phase intermediate-level AC-DC converter is connected to the second input end of the previous-level AC-DC converter of the third-phase intermediate-level AC-DC converter, and the first input end of the third-phase last-level AC-DC converter is connected to the second input end of the previous-level AC-DC converter of the third-phase last-level AC-DC converter.

[0091] See also Figure 1 , the first input terminal of AC-DC 11 is connected to the A-phase transmission line of the AC power grid, 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 the AC power grid, 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 the AC power grid, 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 terminal of AC-DC n2 and the second input terminal of AC-DC n3. Figure 1 The first output end of each AC-DC converter is connected to the positive pole of the DC bus, and the second output end of each AC-DC converter is connected to the negative pole of the DC bus.

[0092] Figure 1 This is a specific cascade diagram of AC-DC converters 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 the present application. The multiple AC-DC converters in each phase AC-DC module are cascaded, which can reduce the voltage stress of the electronic switching tube in the AC-DC converter, thereby reducing the cost of the AC-DC converter, and then reducing the cost of the AC-DC module, and then reducing the cost of the energy storage system.

[0093] Optionally, the AC-DC converter includes: a primary circuit, a transformer and a secondary circuit, the primary circuit includes two primary bridge arms or three primary bridge arms, and the secondary circuit includes two secondary bridge arms; the first output end of the AC-DC converter is connected to the first ends of the two secondary bridge arms, the second output end of the AC-DC converter is connected to the second ends of the two secondary bridge arms, and the midpoints of the two secondary bridge arms are respectively connected to the two ends of the secondary winding of the transformer;

[0094] In the case where the primary circuit includes two primary bridge arms, the midpoints of the two primary bridge arms are respectively suitable for connecting 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 suitable for connecting the two ends of the primary winding of the transformer;

[0095] In the case where the primary circuit includes three primary bridge arms, two of the three primary bridge arms' midpoints are suitable for connecting the first input terminal of the AC-DC converter and the two ends of the primary winding of the transformer, and the other bridge arm midpoint is connected to the second input terminal of the AC-DC converter.

[0096] See also Figure 4 , Figure 4 Schematic diagram of the structure of an AC-DC converter provided in an embodiment of the present application. Figure 4 As shown, the AC-DC converter includes: a primary circuit, a transformer and a secondary circuit, wherein the primary circuit includes three primary bridge arms, and the secondary circuit includes two secondary bridge arms; the first output end of the AC-DC converter is connected to the first ends of the two secondary bridge arms, the second output end of the AC-DC converter is connected to the second ends of the two secondary bridge arms, and the bridge arm midpoints of the two secondary bridge arms are respectively connected to the two ends of the secondary winding of the transformer; two bridge arm midpoints of the three primary bridge arm midpoints are suitable for connecting the first input end of the AC-DC converter and the two ends of the primary winding of the transformer, and the other bridge arm midpoint is connected to the second input end of the AC-DC converter.

[0097] Figure 4 The primary circuit and the secondary circuit may both include capacitors, and the capacitor in the primary circuit is used to stabilize the voltage between the first end and the second end of the primary bridge arm. The capacitor in the secondary circuit is used to stabilize the voltage at the output end of the secondary circuit. Figure 4 The primary circuit also includes an inductor, which serves as a resonant element and can store energy during the switching action of the electronic switch tube of the primary bridge arm.

[0098] Two of the three primary bridge arms' midpoints are suitable for connecting to the first input terminal of the AC-DC converter, which may specifically include: two of the three primary bridge arms' midpoints are connected to the first input terminal of the AC-DC converter (e.g. Figure 4 As shown), or one of the midpoints of the three primary bridge arms is connected to the first input terminal of the AC-DC converter through an inductor (as shown Figure 3 or Figure 6 As shown), the midpoint of the other bridge arm is connected to the first input terminal of the AC-DC converter through another inductor.

[0099] See also Figure 5 , Figure 5 Schematic diagram of the structure of an AC-DC converter provided in an embodiment of the present application. Figure 5 As shown, the AC-DC converter includes: a primary circuit, a transformer and a secondary circuit, wherein the primary circuit includes two primary bridge arms, and the secondary circuit includes two secondary bridge arms; the first output end of the AC-DC converter is connected to the first ends of the two secondary bridge arms, the second output end of the AC-DC converter is connected to the second ends of the two secondary bridge arms, and the bridge arm midpoints of the two secondary bridge arms are respectively connected to the two ends of the secondary winding of the transformer; the bridge arm midpoints of the two primary bridge arms are respectively suitable for connecting the first input end and the second input end of the AC-DC converter, and the bridge arm midpoints of the two primary bridge arms are respectively suitable for the two ends of the primary winding of the transformer.

[0100] Figure 5 The primary circuit and the secondary circuit may both include capacitors, and the capacitor in the primary circuit is used to stabilize the voltage between the first end and the second end of the primary bridge arm. The capacitor in the secondary circuit is used to stabilize the voltage at the output end of the secondary circuit. Figure 5 The primary circuit also includes an inductor, which serves as a resonant element and can store energy during the switching action of the electronic switch tube of the primary bridge arm.

[0101] The midpoints of the two primary bridge arms are respectively suitable for connecting the first input terminal and the second input terminal of the AC-DC converter, which may specifically include: two of the midpoints of the two primary bridge arms are respectively connected to the first input terminal of the AC-DC converter (such as Figure 5 ) and the second input terminal, or one of the midpoints of the bridge arms of the two primary bridge arms is connected to the first input terminal of the AC-DC converter (as shown) through an inductor. Figure 7 The midpoint of the other bridge arm is connected to the second input terminal of the AC-DC converter.

[0102] Optional, see Figure 3, when the primary circuit includes three primary bridge arms, the primary circuit includes: a first primary bridge arm, a second primary bridge arm, a third primary bridge arm, a first inductor, a second inductor, a third inductor and a first capacitor, and the secondary circuit includes: a first secondary bridge arm, a second secondary bridge arm and a second capacitor; the first end of the first primary bridge arm is connected to the first end of the second primary bridge arm, the first end of the third primary bridge arm and the first end of the first capacitor, and the second end of the first primary bridge arm is connected to the second end of the second primary bridge arm, the second end of the third primary bridge arm and the second end of the first capacitor;

[0103] The first input end of the AC-DC converter is connected to the first end of the first inductor and the first end of the second inductor, the second end of the first inductor is connected to the bridge arm midpoint of the first primary bridge arm and the first end of the third inductor, the second end of the third inductor is connected to the first end of the primary winding of the transformer, the second end of the second inductor is connected to the bridge arm midpoint of the second primary bridge arm and the second end of the primary winding of the transformer, and the second input end of the AC-DC converter is connected to the bridge arm midpoint of the third primary bridge arm;

[0104] The first output end 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 end 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, and the midpoint of the second secondary bridge arm is connected to the second end of the secondary winding of the transformer.

[0105] Figure 3 In the example, an AC-DC converter consists of 10 electronic switches. Figure 2 In comparison, each AC-DC converter can save 2 electronic switches, thereby reducing the number of electronic switch tubes used in the AC-DC converter, reducing the cost of the AC-DC converter, and further reducing the cost of the energy storage system.

[0106] It should be noted that Figure 3 The first inductor, the second inductor, the third inductor, the first capacitor and the second capacitor in the circuit can be deleted as needed.

[0107] Optional, see Figure 6 , Figure 6 is a schematic diagram of a specific structure of an AC-DC converter provided in an embodiment of the present application, such as Figure 6As shown, in the case where the primary circuit includes three primary bridge arms, the primary circuit includes: a first primary bridge arm, a second primary bridge arm, a third primary bridge arm, a first inductor, a second inductor, a third inductor, a first capacitor and a third capacitor, and the secondary circuit includes: a first secondary bridge arm, a second secondary bridge arm and a second capacitor; the first end of the first primary bridge arm is connected to the first end of the second primary bridge arm, the first end of the third primary bridge arm and the first end of the first capacitor, and the second end of the first primary bridge arm is connected to the second end of the second primary bridge arm, the second end of the third primary bridge arm and the second end of the first capacitor;

[0108] The first input end of the AC-DC converter is connected to the first end of the first inductor and the first end of the second inductor, the second end of the first inductor is connected to the midpoint of the bridge arm of the first primary bridge arm and the first end of the third inductor, the second end of the third inductor is connected to the first end of the primary winding of the transformer, the second end of the second inductor is connected to the first end of the third capacitor and the midpoint of the bridge arm of the second primary bridge arm, the second end of the third capacitor is connected to the second end of the primary winding of the transformer, and the second input end of the AC-DC converter is connected to the midpoint of the bridge arm of the third primary bridge arm;

[0109] The first output end 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 end 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, and the midpoint of the second secondary bridge arm is connected to the second end of the secondary winding of the transformer.

[0110] Figure 6 In the example, an AC-DC converter consists of 10 electronic switches. Figure 2 In comparison, each AC-DC converter can save 2 electronic switches, thereby reducing the number of electronic switch tubes used in the AC-DC converter, reducing the cost of the AC-DC converter, and further reducing the cost of the energy storage system. Figure 6 and Figure 3 Compared with the AC-DC converter, a capacitor is added to improve the DC isolation effect of the AC-DC converter. Figure 3 The output voltage range is relatively wide, for example, the output voltage range can be 500V-1000V. Figure 6 The output voltage range is narrower, for example, the output voltage range can be 600-900V. Different architectures can be selected according to different application environments.

[0111] It should be noted that Figure 6 The first inductor, the second inductor, the third inductor, the first capacitor, the second capacitor and the third capacitor in the circuit can be deleted as needed.

[0112] Optional, see Figure 7 , Figure 7 is a schematic diagram of a specific structure of an AC-DC converter provided in an embodiment of the present application, such as Figure 7 As shown, in the case where the primary circuit includes two primary bridge arms, the primary circuit includes: a first primary bridge arm, a second primary bridge arm, a first inductor, a second inductor and a first capacitor, and the secondary circuit includes: a first secondary bridge arm, a second secondary bridge arm and a second capacitor; the first end of the first primary bridge arm is connected to the first end of the second primary bridge arm and the first end of the first capacitor, and the second end of the first primary bridge arm is connected to the second end of the second primary bridge arm and the second end of the first capacitor;

[0113] The first input end of the AC-DC converter is connected to the first end of the first inductor, the second end of the first inductor is connected to the bridge arm midpoint of the first primary bridge arm and the first end of the second inductor, the second end of the second inductor is connected to the first end of the primary winding of the transformer, and the second input end of the AC-DC converter is connected to the bridge arm midpoint of the second primary bridge arm and the second end of the primary winding of the transformer;

[0114] The first output end 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 end 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, and the midpoint of the second secondary bridge arm is connected to the second end of the secondary winding of the transformer.

[0115] Figure 7 In the example, an AC-DC converter consists of 10 electronic switches. Figure 2 Compared with the conventional AC-DC converter, each AC-DC converter can save two electronic switches, thereby reducing the number of electronic switch tubes used in the AC-DC converter, reducing the cost of the AC-DC converter, and thus reducing the cost of the energy storage system. Figure 3 and Figure 6 compared to, Figure 7 By using less inductance, the size of the AC-DC converter can be reduced.

[0116] It should be noted that Figure 7 The first inductor, the second inductor, the first capacitor and the second capacitor in the circuit can be deleted as needed.

[0117] Figure 1 The AC-DC converter in the energy storage system shown can be Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 Any of . Figure 1 The AC-DC converter in the energy storage system shown may be any one of the above, or a combination of at least two of the above, which is not limited in the embodiments of the present application.

[0118] See also Figure 8 , Figure 8 It is a specific structural diagram of an energy storage system provided in an embodiment of the present application. Figure 8 Each AC-DC converter in Figure 3 For example.

[0119] See also Fig. 9 , Fig. 9 It is a specific structural diagram of another energy storage system provided in an embodiment of the present application. Fig. 9 Each AC-DC converter in Figure 3 For example.

[0120] It should be noted that Figure 8 Each AC-DC converter in the circuit contains three inductors. Fig. 9 In the example, only the first-stage AC-DC converter of each phase contains three inductors, and the other AC-DC converters contain two inductors. Figure 8 compared to, Fig. 9 Less inductance can be used, thus reducing the size of the energy storage system.

[0121] Figure 8 and Fig. 9 Can be used in different application scenarios. Figure 8 It can be used in scenarios with higher output voltage ripple requirements. Fig. 9 Can be used in smaller scenes.

[0122] and Fig. 9 compared to, Figure 8 The inductance of each inductor can be smaller, for example, Figure 8 The inductance of each inductor is 10 microhenry (uH). Fig. 9 The inductance at the input end of the first stage of each phase of the AC-DC converter can be 100uH. Figure 8 Each inductor is smaller, Figure 8 The output current ripple is compared to Fig. 9 Will be smaller and the output will be smoother.

[0123] See also Fig.10 , Fig.10Schematic diagram of a charging station provided in an embodiment of the present application. Fig.10 As shown, the charging station may include Figure 1 or Figure 8 or Fig. 9 The energy storage system shown.

[0124] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0125] 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 only schematic, and for example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed.

Claims

1. An energy storage system, characterized in that: It includes an AC power grid, an AC-DC system, and a DC bus; the input end of the AC-DC system is connected to the AC power grid, the output end 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; The AC-DC system includes N cascaded AC-DC converters, the AC-DC converters adopt a single-stage structure, and 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 includes a plurality of AC-DC modules; each of the AC-DC modules includes n1 cascaded AC-DC converters; n1 is an integer greater than or equal to 2; The input end of each of the AC-DC modules is connected to one phase of the three-phase transmission line of the AC power grid, and the output end of each of the AC-DC modules is connected to the DC bus.

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

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

5. The energy storage system according to claim 2 or 3, characterized in that: 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 final-stage AC-DC converter; Wherein, the first input end of the first-stage AC-DC converter of each of the AC-DC modules is connected to one phase of the three-phase transmission line of the AC power grid, and the second input ends of the last-stage AC-DC converters of each of the AC-DC modules are connected in common; the first output end of each AC-DC converter is connected to the positive pole of the DC bus, and the second output end of each AC-DC converter is connected to the negative pole of the DC bus; In each of the AC-DC modules, the first input end of the intermediate-stage AC-DC converter is connected to the second input end of the AC-DC converter of the previous stage of the intermediate-stage AC-DC converter; the first input end of the last-stage AC-DC converter is connected to the second input end of the AC-DC converter of the previous stage of the last-stage AC-DC converter.

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, wherein the first-phase AC-DC module includes: a first-phase first-level AC-DC converter, a first-phase intermediate-level AC-DC converter and a first-phase last-level AC-DC converter; the second-phase AC-DC module includes: a second-phase first-level AC-DC converter, a second-phase intermediate-level AC-DC converter and a second-phase last-level AC-DC converter; the third-phase AC-DC module includes: a third-phase first-level AC-DC converter, a third-phase intermediate-level AC-DC converter and a third-phase last-level AC-DC converter; Wherein, the first input end of the first-stage AC-DC converter of the first phase is connected to the first-phase transmission line of the AC power grid, the first input end of the first-stage AC-DC converter of the second phase is connected to the second-phase transmission line of the AC power grid, and the first input end of the first-stage AC-DC converter of the third phase is connected to the third-phase transmission line of the AC power grid; the second input end of the last-stage AC-DC converter of the first phase is connected to the second input end of the last-stage AC-DC converter of the second-phase AC-DC module and the second input end of the last-stage AC-DC converter of the third-phase AC-DC module; the first output end of each AC-DC converter is connected to the positive pole of the DC bus, and the second output end of each AC-DC converter is connected to the negative pole of the DC bus; The first input end of the first-phase intermediate-stage AC-DC converter is connected to the second input end of the previous-stage AC-DC converter of the first-phase intermediate-stage AC-DC converter, and the first input end of the first-phase last-stage AC-DC converter is connected to the second input end of the previous-stage AC-DC converter of the first-phase last-stage AC-DC converter; The first input end of the second-phase intermediate-stage AC-DC converter is connected to the second input end of the previous-stage AC-DC converter of the second-phase intermediate-stage AC-DC converter, and the first input end of the second-phase last-stage AC-DC converter is connected to the second input end of the previous-stage AC-DC converter of the second-phase last-stage AC-DC converter; The first input end of the third-phase intermediate-level AC-DC converter is connected to the second input end of the previous-level AC-DC converter of the third-phase intermediate-level AC-DC converter, and the first input end of the third-phase last-level AC-DC converter is connected to the second input end of the previous-level AC-DC converter of the third-phase last-level AC-DC converter.

7. The energy storage system according to any one of claims 1 to 6, characterized in that: The AC-DC converter comprises: a primary circuit, a transformer and a secondary circuit, wherein the primary circuit comprises two primary bridge arms or three primary bridge arms, and the secondary circuit comprises two secondary bridge arms; the first output end of the AC-DC converter is connected to the first ends of the two secondary bridge arms, the second output end of the AC-DC converter is connected to the second ends of the two secondary bridge arms, and the midpoints of the two secondary bridge arms are respectively connected to the two ends of the secondary winding of the transformer; In the case where the primary circuit includes two primary bridge arms, the midpoints of the two primary bridge arms are respectively suitable for connecting 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 suitable for connecting the two ends of the primary winding of the transformer; In the case where the primary circuit includes three primary bridge arms, two of the three primary bridge arms' midpoints are suitable for connecting the first input terminal of the AC-DC converter and the two ends of the primary winding of the transformer, and the other bridge arm midpoint is connected to the second input terminal of the AC-DC converter.

8. The energy storage system according to claim 7, characterized in that: In the case where the primary circuit includes three primary bridge arms, the primary circuit includes: a first primary bridge arm, a second primary bridge arm, and a third primary bridge arm, and the secondary circuit includes: a first secondary bridge arm and a second secondary bridge arm; the first end of the first primary bridge arm is connected to the first end of the second primary bridge arm and the first end of the third primary bridge arm, and the second end of the first primary bridge arm is connected to the second end of the second primary bridge arm and the second end of the third primary bridge arm; The first input end of the AC-DC converter is suitable for connecting the bridge arm midpoint of the first primary bridge arm and the bridge arm midpoint of the second primary bridge arm, the bridge arm midpoint of the first primary bridge arm is suitable for connecting the first end of the primary winding of the transformer, the bridge arm midpoint of the second primary bridge arm is suitable for connecting the second end of the primary winding of the transformer, and the second input end of the AC-DC converter is connected to the bridge arm midpoint of the third primary bridge arm; The first output end 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 end 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.

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

10. The energy storage system according to claim 7, characterized in that: In the case where the primary circuit includes three primary bridge arms, the primary circuit includes: a first primary bridge arm, a second primary bridge arm and a third primary bridge arm, and the secondary circuit includes: a first secondary bridge arm and a second secondary bridge arm; the first end of the first primary bridge arm is connected to the first end of the second primary bridge arm and the first end of the third primary bridge arm, and the second end of the first primary bridge arm is connected to the second end of the second primary bridge arm and the second end of the third primary bridge arm; The first input end of the AC-DC converter is suitable for connecting to the bridge arm midpoint of the first primary bridge arm, the bridge arm midpoint of the first primary bridge arm is suitable for connecting to the first end of the primary winding of the transformer, the bridge arm midpoint of the second primary bridge arm is suitable for connecting to the second end of the primary winding of the transformer, and the second input end of the AC-DC converter is connected to the bridge arm midpoint of the third primary bridge arm; The first output end 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 end 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.

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

12. The energy storage system according to claim 7, characterized in that: In the case where the primary circuit includes two primary bridge arms, the primary circuit includes: a first primary bridge arm and a second primary bridge arm, and the secondary circuit includes: a first secondary bridge arm and a second secondary bridge arm; the first end of the first primary bridge arm is connected to the first end of the second primary bridge arm, and the second end of the first primary bridge arm is connected to the second end of the second primary bridge arm; The first input end of the AC-DC converter is suitable for connecting the bridge arm midpoint of the first primary bridge arm, the bridge arm midpoint of the first primary bridge arm is suitable for connecting the first end of the primary winding of the transformer, and the second input end of the AC-DC converter is connected to the bridge arm midpoint of the second primary bridge arm and the second end of the primary winding of the transformer; The first output end 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 end 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.

13. The energy storage system according to claim 12, characterized in that: The primary circuit further includes a first inductor, a second inductor, a third inductor and a first capacitor, and the secondary circuit further includes a second capacitor; the first end of the first primary bridge arm is connected to the first end of the first capacitor, and the second end of the first primary bridge arm is connected to the second end of the first capacitor; The first input end of the AC-DC converter is connected to the first end of the first inductor, the second end of the first inductor is connected to the bridge arm midpoint of the first primary bridge arm and the first end of the second inductor, and the second end of the second inductor is connected to the first end of the primary winding of the transformer; The first output end of the AC-DC converter is connected to the first end of the second capacitor, and the second output end of the AC-DC converter is connected to the second end 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 or an energy storage device.

15. The energy storage system according to any one of claims 1 to 14, characterized in that: The energy storage system further comprises a photovoltaic assembly, and the DC bus is connected to the photovoltaic assembly via a DC-DC module.

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

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