Energy storage equipment grid-connected device and energy storage system

Abstract

The utility model relates to the technical field of electronic circuits, and provides an energy storage equipment grid connection device and an energy storage system. An energy storage equipment grid connection device comprises an energy storage converter and a power-on preparation module. Wherein the energy storage converter is used for being connected with a power grid, and the power-on preparation module is connected with the energy storage converter through a direct-current bus. The power-on preparation module comprises a connection bus, a power-on switch, a slow charging branch, a voltage-sharing circuit, N interface units and a control unit. And the control unit is respectively connected with the power-on switch and the slow charging branch. The control unit can be used for controlling the slow charging branch to be switched on and controlling the power-on switch to be switched off at the same time, so that electric energy of the energy storage equipment can be discharged by the voltage-sharing circuit. When the pressure difference between at least two pieces of energy storage equipment is large, the energy storage equipment grid-connected device can discharge the electric energy of the energy storage equipment. And an implementation basis is provided for the energy storage equipment grid connection device to connect all the energy storage equipment into a power grid, so that the application range of the energy storage equipment grid connection device is expanded.

Description

Technical Field

[0001] This application belongs to the field of electronic circuit technology, and in particular relates to a grid-connected energy storage device and an energy storage system. Background Technology

[0002] With the rapid development of new energy technologies, more and more green power generation equipment is being popularized and promoted. For example, solar power generation equipment and wind power generation equipment are installed on users' roofs to generate electricity, which is then stored using energy storage equipment. This allows the electricity to be used by users at any time and can also be supplied to the grid. As a result, the demand for grid-connected energy storage devices is also increasing.

[0003] However, in practical applications, users may connect energy storage devices from different manufacturers or of different specifications to the same grid-connected energy storage device. For example, connecting at least two energy storage devices to the same grid-connected device can lead to a situation where, if the voltage difference between the two devices is significant, the grid-connected device cannot integrate all the devices into the power grid. Therefore, providing a new energy storage grid-connected device solution is a pressing technical problem that needs to be solved. Utility Model Content

[0004] The purpose of this application is to provide an energy storage device grid connection device and an energy storage system, aiming to provide a new energy storage device grid connection device solution to solve the problem of the low applicability of energy storage device grid connection devices.

[0005] A first aspect of this application provides an energy storage device grid connection apparatus, comprising:

[0006] Energy storage converters are used to connect to the power grid;

[0007] The power-on preparation module is connected to the energy storage converter via the DC bus. The power-on preparation module includes:

[0008] The connection bus includes a first connection bus and a second connection bus;

[0009] The power switch is connected to the first connection bus.

[0010] The slow-charge branch is connected in parallel with the power-on switch to form the first node, and forms the second node on the first connection bus;

[0011] The voltage equalization circuit is connected to the first node and the second connection bus respectively, and the voltage equalization circuit is also connected to the DC bus.

[0012] There are N interface units, each configured with a connection terminal for connecting to the connection bus, and the interface units are used to connect energy storage devices; where N is an integer greater than 1.

[0013] The control unit is connected to the power-on switch and the slow-charge branch respectively. The control unit is used to control the power-on switch to be turned off when the slow-charge branch is turned on, and to control the slow-charge branch to be turned off when the power-on switch is turned on.

[0014] The second aspect of this application provides an energy storage system, including the grid-connected energy storage device provided in the first aspect, and X energy storage devices; wherein X is an integer, and 1≤X≤N.

[0015] The beneficial effects of this utility model embodiment compared with the prior art are:

[0016] The aforementioned grid-connected energy storage device includes an energy storage converter and a power-on preparation module. The energy storage converter is used to connect to the power grid, and the power-on preparation module is connected to the energy storage converter via a DC bus. The power-on preparation module includes: a connection bus, a power-on switch, a slow-charge branch, a voltage equalization circuit, N interface units, and a control unit. The connection bus includes a first connection bus and a second connection bus. The power-on switch is connected to the first connection bus. The slow-charge branch is connected in parallel with the power-on switch to form a first node, and also forms a second node on the first connection bus. The voltage equalization circuit is connected to the first node and the second connection bus respectively, and is also connected to the DC bus. Each interface unit is configured with a connection terminal for connecting to the connection bus, and the interface unit is used to connect to the energy storage device. The control unit is connected to the power-on switch and the slow-charge branch respectively. The control unit can control the conduction of the slow-charge branch and simultaneously control the disconnection of the power-on switch, allowing the energy storage device to sequentially pass through the interface unit, connection bus, and slow-charge branch to form a loop with the voltage equalization circuit, enabling the energy of the energy storage device to be discharged through the voltage equalization circuit. This allows the grid-connected energy storage device to discharge energy to the energy storage device even when there is a large voltage difference between at least two energy storage devices. Furthermore, the control unit can also control the conduction of the power-on switch and simultaneously control the disconnection of the slow-charge branch, allowing the energy storage device to sequentially pass through the interface unit, connection bus, and power-on switch to connect to the DC bus, achieving grid-connected operation. This provides a foundation for integrating all energy storage devices into the grid, making the grid-connected energy storage device applicable to more scenarios and thus expanding its applicability. Attached Figure Description

[0017] Figure 1 A schematic diagram of the structure of an energy storage device grid connection device provided in an embodiment of this application;

[0018] Figure 2 A schematic diagram of the specific structure of the grid-connected energy storage device provided in the embodiments of this application;

[0019] Figure 3 A partial circuit diagram of the grid-connected energy storage device provided in the embodiments of this application;

[0020] Figure 4 A schematic diagram of the specific structure of the grid-connected energy storage device provided in another embodiment of this application;

[0021] Figure 5 A schematic diagram of the specific structure of the grid-connected energy storage device provided in another embodiment of this application;

[0022] Figure 6 This is a schematic diagram of an energy storage system provided in an embodiment of this application. Detailed Implementation

[0023] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0024] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0025] For example, in some application scenarios, users may connect energy storage devices from different manufacturers or with different specifications to the same grid-connected energy storage device. For instance, connecting at least two energy storage devices to the same grid-connected device can be problematic. If the voltage difference between the two devices is significant, the grid-connected device can disconnect the device with the higher voltage from the grid for safety reasons. In other words, the grid-connected device cannot connect all energy storage devices to the grid. Therefore, providing a new grid-connected energy storage device solution is a crucial technical problem that needs to be solved.

[0026] To address the aforementioned technical problems, this embodiment provides a grid-connected energy storage device, including an energy storage converter and a power-on preparation module. The energy storage converter is used to connect to the power grid, and the power-on preparation module is connected to the energy storage converter via a DC bus. The power-on preparation module includes: a connection bus, a power-on switch, a slow-charge branch, a voltage equalization circuit, N interface units, and a control unit. The connection bus includes a first connection bus and a second connection bus. The power-on switch is connected to the first connection bus. The slow-charge branch is connected in parallel with the power-on switch to form a first node, and also forms a second node on the first connection bus. The voltage equalization circuit is connected to the first node and the second connection bus respectively, and is also connected to the DC bus. Each interface unit is configured with a connection terminal for connecting to the connection bus, and the interface unit is used to connect to the energy storage device. The control unit is connected to the power-on switch and the slow-charge branch respectively. The control unit can control the conduction of the slow-charge branch and simultaneously control the disconnection of the power-on switch, allowing the energy storage device to sequentially pass through the interface unit, connection bus, and slow-charge branch to form a loop with the voltage equalization circuit, enabling the energy of the energy storage device to be discharged through the voltage equalization circuit. This allows the grid-connected energy storage device to discharge energy to the energy storage device even when there is a large voltage difference between at least two energy storage devices. Furthermore, the control unit can also control the conduction of the power-on switch and simultaneously control the disconnection of the slow-charge branch, allowing the energy storage device to sequentially pass through the interface unit, connection bus, and power-on switch to connect to the DC bus, achieving grid-connected operation. This provides a foundation for integrating all energy storage devices into the grid, making the grid-connected energy storage device applicable to more scenarios and thus expanding its applicability.

[0027] This embodiment provides an energy storage device grid-connection device that can be configured in energy storage device grid-connection scenarios. Here, the grid-connection scenario can be a scenario where multiple energy storage devices are connected in parallel to form an energy storage network, or a scenario where multiple energy storage devices are connected to a household power grid; there are no limitations. Unlike energy storage devices performing cell balancing on their own, or energy storage devices performing parallel balancing, the energy storage device grid-connection device provided in this embodiment, when connecting at least two energy storage devices, allows the control unit to act as a battery management system or energy management system. By controlling the slow-charge branch to be turned on and simultaneously controlling the power-on switch to be turned off, the energy storage device with the higher voltage can form a power discharge circuit through the interface unit, connection bus, and slow-charge branch, together with the voltage equalization circuit. This achieves power discharge from the energy storage device, providing a basis for ensuring that the voltage difference between the energy storage devices meets the grid-connection requirements of the energy storage device grid-connection device. Furthermore, the control unit can also control the power-on switch to be turned on and simultaneously control the slow-charge branch to be turned off, allowing the energy storage devices to be connected to the DC bus sequentially through the interface unit, connection bus, and power-on switch, realizing all grid-connection operations.

[0028] The following provides a detailed description of the grid connection device for energy storage provided in this embodiment through specific implementation methods.

[0029] Figure 1 A schematic diagram of the structure of an energy storage device grid connection device provided in an embodiment of this application is shown. Figure 1 As shown, the energy storage grid connection device 100 includes an energy storage converter 10 and a power-on preparation module 20. Specifically:

[0030] The energy storage converter 10 is used to connect to the power grid. The power-on preparation module 20 is connected to the energy storage converter 10 via a DC bus.

[0031] exist Figure 1 In the power-on preparation module 20, there are: a connection bus 21, a power-on switch 22, a slow charging branch 23, a voltage equalization circuit 24, N interface units 25, and a control unit 26.

[0032] The connection bus 21 includes a first connection bus 211 and a second connection bus 212. A power-on switch 22 is connected to the first connection bus 211. A slow-charge branch 23 is connected in parallel with the power-on switch 22 to form a first node P1, and a second node P2 is formed on the first connection bus 211. A voltage equalization circuit 24 is connected to both the first node P1 and the second connection bus 212. The voltage equalization circuit 24 is also connected to the DC bus. Each of the N interface units 25 is configured with a connection terminal for connecting to the connection bus 21, and the interface unit 25 is used to connect to the energy storage device. Here, N is an integer greater than 1. A control unit 26 is connected to the power-on switch 22 and the slow-charge branch 23, respectively. The control unit 26 is used to control the power-on switch 22 to be off when the slow-charge branch 23 is on, and to control the slow-charge branch 23 to be off when the power-on switch 22 is on.

[0033] In this embodiment, the energy storage converter 10 and the power-on preparation module 20 in the energy storage device grid connection device 100 can be configured in the same housing or enclosure structure. The energy storage converter 10 can be connected to the power grid via a power transmission line. The interface unit 25 in the power-on preparation module 20 can be used to connect the energy storage device, and the power-on preparation module 20 is connected to the energy storage converter 10 via a DC bus. Therefore, when the energy storage device is connected to the power-on preparation module 20 via the interface unit 25, the power-on preparation module 20 can connect the energy storage device to the power grid via the DC bus and the energy storage converter 10.

[0034] It is easy to understand that since the power-on preparation module 20 includes N interface units 25, where N is an integer greater than 1, the energy storage grid connection device 100 can connect N energy storage devices through the N interface units 25.

[0035] In a specific implementation, the power-on switch 22 can be an electrically controlled switch or a switching circuit controlled by the control unit 26. The slow-charge branch 23 can be a current-limiting circuit including a controlled switch, wherein the controlled switch is controlled by the control unit 26. Correspondingly, the voltage equalization circuit 24 can specifically be a purely resistive circuit.

[0036] As an example, the voltage equalization circuit 24 includes a pure resistance equalization branch (not shown in the figure), the first end of which is used to connect to the first node P1, and the second end of which is used to connect to the second connection bus 212.

[0037] In this embodiment, while the control unit 26 controls the slow charging branch 23 to be turned on, it also controls the power-on switch 22 to be turned off. At this time, the energy of the energy storage device can be transferred to the pure resistance balancing branch through the interface unit 25, the connection bus 21 and the slow charging branch 23. That is, the pure resistance balancing branch discharges the energy of the energy storage device.

[0038] It is understandable that, since the power-on preparation module 20 discharges electrical energy to the energy storage device at this time, the energy storage converter 10 in the energy storage device grid connection device 100 does not work. That is, although the power-on preparation module 20 is connected to the energy storage converter 10 through the DC bus, since the energy storage converter 10 does not work, the electrical energy will not be transmitted to the energy storage converter 10 through the DC bus at this time.

[0039] As an example, when only one energy storage device is connected to the grid-connected energy storage device 100 via interface unit 25, the control unit 26 in the grid-connected energy storage device 100 can control the power-on switch 22 to turn on and simultaneously control the slow-charge branch 23 to turn off. Since the power-on preparation module 20 is connected to the energy storage converter 10 via the DC bus, and the energy storage converter 10 is used to connect to the power grid, when the power-on switch 22 is closed, the energy storage device is connected to the DC bus via interface unit 25, connection bus 21, and power-on switch 22, and can then transfer electrical energy to the power grid through the energy storage converter 10.

[0040] As another example, when at least two energy storage devices are connected to the grid-connected energy storage device 100 via interface unit 25, the control unit 26 in the grid-connected energy storage device 100 can determine whether to connect all energy storage devices to the grid by acquiring the voltage of each energy storage device. Here, the control unit 26 can communicate with the analog front-end or battery management system in the energy storage device through interface unit 25 to acquire the voltage value of each energy storage device. When the voltage difference between at least two energy storage devices is not less than a preset voltage difference, the path between the energy storage device with the higher voltage value and interface unit 25 can be opened only. At this time, the control unit 26 can control the slow charging branch 23 to be turned on and simultaneously control the power-on switch 22 to be turned off, so that the energy storage device with the higher voltage can form an energy discharge circuit through interface unit 25, connection bus 21, and slow charging branch 23 with voltage equalization circuit 24. It is easy to understand that when the voltage of the energy storage device after energy discharge through the energy discharge circuit is less than the voltage difference between the energy storage device and other energy storage devices, the control unit 26 can control the interface unit 25 connected to the energy storage device to be turned on, and at the same time control the power-on switch 22 to be turned on, and control the slow charging branch 23 to be turned off.

[0041] Based on the above example, when the control unit 26 controls the power-on switch 22 to be turned on and controls the slow-charge branch 23 to be turned off, it means that the energy storage device can transfer electrical energy to the power grid through the energy storage device grid connection device 100. That is, at this time, by controlling the workload of the energy storage converter 10, a conductive path can be formed between the energy storage device, the power-on preparation module 20, the DC bus, and the energy storage converter 10. At this time, since the voltage equalization circuit 24 is a purely resistive circuit, it can be regarded as an open circuit. The electrical energy between the energy storage device and the power grid can be transmitted through the DC bus and is not affected by the voltage equalization circuit 24.

[0042] It is readily understood that in all embodiments of this application, the control unit 26 in the energy storage grid connection device 100 can control the alternating on / off state of the power-on switch 22 and the slow-charge branch 23, thereby realizing the energy discharge and grid connection operation of the energy storage device. As for when the control unit 26 controls the alternating on / off state of the power-on switch 22 and the slow-charge branch 23, the above examples can be used as a reference. In specific implementations, those skilled in the art can also configure the control unit 26 according to actual needs, so this will not be elaborated here.

[0043] Figure 2 A schematic diagram of the specific structure of the grid-connected energy storage device provided in an embodiment of this application is shown. As one embodiment, the interface unit 25 is configured with a first connection terminal 2501 and a second connection terminal 2502. Specifically, the first connection terminal 2501 is connected to the first connection bus 211, and the second connection terminal 2502 is connected to the second connection bus 212.

[0044] In this embodiment, since the interface unit 25 is used to connect the energy storage device, the first connection terminal 2501 and the second connection terminal 2502 in the interface unit 25 can correspond to the positive and negative terminals of the energy storage device, respectively.

[0045] Taking the first connection terminal 2501 corresponding to the positive terminal of the energy storage device and the second connection terminal 2502 corresponding to the negative terminal of the energy storage device as an example, when the energy storage device is connected to the interface unit 25, the positive terminal of the energy storage device is connected to the first connection bus 211 through the first connection terminal 2501, and the negative terminal of the energy storage device is connected to the second connection bus 212 through the second connection terminal 2502. By turning on the slow charging branch 23 and turning off the power-on switch 22, the electrical energy of the energy storage device can be discharged through the voltage equalization circuit 24. By turning on the power-on switch 22 and turning off the slow charging branch 23, the energy storage device can be connected to the power grid through the DC bus and the energy storage converter 10 in the grid connection device 100 of the energy storage device, thereby realizing the transfer of electrical energy between the energy storage device and the power grid.

[0046] In a specific implementation, the interface switch 251 can be a relay or an electronic switch, etc. The control unit 26 can control the opening and closing of the interface switch 251, thereby controlling the connection between the energy storage device and the interface unit 25.

[0047] As an example, such as Figure 2 As shown, interface unit 25 is also configured with interface switch 251, which is connected to the first connection terminal 2501. Interface switch 251 is used, controlled by control unit 26, to connect or disconnect the path between the energy storage device and the first connection terminal 2501. And / or, interface switch 251 is connected to the second connection terminal 2502, and interface switch 251 is used, controlled by control unit 26, to connect or disconnect the path between the energy storage device and the second connection terminal 2502.

[0048] In this embodiment, the interface switch 251 may specifically refer to the switch connected to the first connection terminal 2501, or it may generally refer to the switch in the interface unit 25 used to control the connection and disconnection between the energy storage device and the interface unit 25.

[0049] For example, when interface switch 251 is connected to the first connection terminal 2501, control unit 26 can control the connection between the positive terminal of the energy storage device and interface unit 25 by controlling the on / off state of interface switch 251. Here, interface switch 251 may specifically refer to a switch connected to the first connection terminal 2501. Similarly, when interface switch 251 is connected to the second connection terminal 2502, control unit 26 can control the connection between the negative terminal of the energy storage device and interface unit 25 by controlling the on / off state of interface switch 251. Here, interface switch 251 may specifically refer to a switch connected to the second connection terminal 2502.

[0050] It is understandable that in other examples, when interface switch 251 is simultaneously connected to the first connection terminal 2501 and the second connection terminal 2502, interface switch 251 may specifically include a first interface switch and a second interface switch (not shown in the figure), that is, the first interface switch is connected to the first connection terminal 2501, and the second interface switch is connected to the second connection terminal 2502. When controlling the on / off state of interface switch 251, control unit 26 specifically controls the on / off state of the first interface switch and the second interface switch simultaneously.

[0051] In the above scheme, by setting an interface switch 251 in the interface unit 25, the control unit 26 can control the opening and closing of the interface switch 251, thereby realizing the opening and closing control of the path between the energy storage device and the interface unit 25, thus providing a basis for more application scenarios of connecting the energy storage device to the power grid through the energy storage device grid connection device 100.

[0052] Figure 3 A partial circuit diagram of the grid-connected energy storage device provided in an embodiment of this application is shown. (Combined with...) Figures 1 to 3 As one embodiment, the slow-charge branch includes a first switch S1 and a first resistor R1. Figure 3 In this circuit, the fixed end of the first switch S1 is connected to the fixed end of the power-on switch 22, the movable end of the first switch S1 is connected to the first end of the first resistor R1, the second end of the first resistor R1 is connected to the movable end of the power-on switch 22, and the controlled end of the first switch S1 is connected to the control unit 26.

[0053] As an example, such as Figure 3 As shown, the voltage equalization circuit 24 includes a purely resistive equalization branch as an example. This purely resistive equalization branch includes: a second resistor R2 and a third resistor R3. In Figure 3 In the circuit, the first end of the second resistor R2 serves as the first end of the pure resistance balancing branch, the second end of the second resistor R2 is connected to the first end of the third resistor R3, and the second end of the third resistor R3 serves as the second end of the pure resistance balancing branch.

[0054] Understandably, in Figure 3 In the example shown, when the first switch S1 is on, because the power-on switch 22 is off, the electrical energy of the energy storage device can be limited by the first resistor R1 and then transferred through the first node P1 to the purely resistive circuit composed of the second resistor R2 and the third resistor R3. The second resistor R2 and the third resistor R3 then dissipate the electrical energy of the energy storage device by converting it into heat. When the power-on switch 22 is on, because the first switch S1 is off, the electrical energy of the energy storage device cannot be limited by the first resistor R1 and then transferred to the purely resistive circuit composed of the second resistor R2 and the third resistor R3. (Combined with...) Figures 1 to 3At this time, the energy storage converter 10 can be controlled to work, and power can be transmitted through the DC bus, thus realizing the transfer of power between the energy storage device and the power grid.

[0055] Figure 4 A schematic diagram of the specific structure of a grid-connected energy storage device according to another embodiment of this application is shown. For example... Figure 4 As shown, the energy storage grid connection device 100 also includes a DC filter branch 27.

[0056] exist Figure 4 In this circuit, the DC filter branch 27 is connected to the first node P1 and the second connection bus 212 respectively. That is, the DC filter branch 27 and the voltage equalization circuit 24 are connected in parallel between the first node P1 and the second connection bus 212.

[0057] In a practical implementation, the DC filter branch 27 can be composed of capacitors to form a filter circuit, which can filter the DC current flowing through the DC bus, thereby improving the overall stability of the energy storage grid connection device 100.

[0058] Figure 5 A schematic diagram of the specific structure of a grid-connected energy storage device according to another embodiment of this application is shown. For example... Figure 5 As shown, the energy storage grid connection device 100 also includes a bidirectional AC / DC conversion unit 11.

[0059] exist Figure 5 In the middle, the bidirectional AC / DC conversion unit 11 is connected to the DC bus and is used to connect to the power grid.

[0060] In practical implementation, the bidirectional AC / DC conversion unit 11 can be implemented using a bidirectional inverter circuit. When using grid power to charge the energy storage device, the AC power supplied by the grid can be converted from AC to DC, and then the charging DC power can be output through the DC bus to charge the energy storage device. When using the energy storage device to supply power to the grid, the DC power passing through the DC bus of the energy storage device can be inverted and then output as AC power to the grid.

[0061] As one embodiment, the bidirectional AC / DC conversion unit 11 includes a bus capacitor (not shown in the figure). In a specific implementation, the bus capacitor can be connected between DC buses. When using grid power to charge the energy storage device, the bidirectional AC / DC conversion unit 11 can charge the bus capacitor based on the AC power provided by the grid, and then output charging DC power through the DC bus to charge the energy storage device. When using the energy storage device to supply power to the grid, the energy storage device provides DC power to the bidirectional AC / DC conversion unit 11 through the DC bus. The bidirectional AC / DC conversion unit 11 inverts the DC power and outputs AC power to the grid.

[0062] Figure 6 A schematic diagram of the structure of an energy storage system provided in an embodiment of this application is shown. Figure 6 As shown in the figure, an energy storage system 200 provided in this application embodiment includes the energy storage grid connection device 100 provided in the above embodiment, and X energy storage devices. Wherein, X is an integer, and 1≤X≤N.

[0063] In this embodiment, after the X energy storage devices are connected to the energy storage device grid connection device 100, the control unit 26 in the energy storage device grid connection device 100 can control the alternating on and off of the power-on switch 22 and the slow charging branch 23, thereby realizing the discharge of electrical energy from any one of the X energy storage devices, as well as the grid connection operation of any one or all of the X energy storage devices.

[0064] It is understandable that the improvements and specific implementation methods related to this application have already been... Figures 1 to 5 The corresponding embodiments are described in detail. In specific implementation, it can be... Figures 1 to 5 Based on the corresponding embodiment, the energy storage device grid connection device 100 is configured in the energy storage system 200, so it will not be described in detail here.

[0065] The above-described 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, and should all be included within the protection scope of this application.

Claims

1. A grid-connection device for energy storage equipment, characterized in that, include: Energy storage converters are used to connect to the power grid; A power-on preparation module is connected to the energy storage converter via a DC bus. The power-on preparation module includes: The connection bus includes a first connection bus and a second connection bus; The power switch is connected to the first connection bus. The slow-charge branch is connected in parallel with the power-on switch to form a first node, and a second node is formed on the first connection bus; The voltage equalization circuit is connected to the first node and the second connection bus respectively, and the voltage equalization circuit is also connected to the DC bus; There are N interface units, each of which is configured with a connection terminal for connecting to the connection bus, and the interface unit is used to connect to an energy storage device; where N is an integer greater than 1. The control unit is connected to the power-on switch and the slow-charge branch respectively. The control unit is used to control the power-on switch to be disconnected when the slow-charge branch is turned on, and to control the slow-charge branch to be disconnected when the power-on switch is turned on.

2. The grid connection device for energy storage equipment according to claim 1, characterized in that, The interface unit is configured with a first connection end and a second connection end; The first connection end is connected to the first connection bus, and the second connection end is connected to the second connection bus.

3. The grid connection device for energy storage equipment according to claim 2, characterized in that, The interface unit is also configured with an interface switch; The interface switch is connected to the first connection terminal, and the interface switch is used, under the control of the control unit, to connect or disconnect the path between the energy storage device and the first connection terminal. and / or The interface switch is connected to the second connection terminal. The interface switch is controlled by the control unit to connect or disconnect the path between the energy storage device and the second connection terminal.

4. The grid connection device for energy storage equipment according to claim 1, characterized in that, The slow-charge branch includes a first switch and a first resistor; The fixed end of the first switch is connected to the fixed end of the power-on switch, the movable end of the first switch is connected to the first end of the first resistor, the second end of the first resistor is connected to the movable end of the power-on switch, and the controlled end of the first switch is connected to the control unit.

5. The grid connection device for energy storage equipment according to claim 1, characterized in that, The voltage equalization circuit includes: A pure resistance balancing branch, wherein the first end of the pure resistance balancing branch is used to connect to the first node, and the second end of the pure resistance balancing branch is used to connect to the second connection bus.

6. The grid connection device for energy storage equipment according to claim 5, characterized in that, The pure resistance balancing branch includes: a second resistor and a third resistor; The first end of the second resistor serves as the first end of the pure resistance balancing branch, the second end of the second resistor is connected to the first end of the third resistor, and the second end of the third resistor serves as the second end of the pure resistance balancing branch.

7. The grid connection device for energy storage equipment according to claim 1, characterized in that, Also includes: The DC filter branch is connected to the first node and the second connection bus, respectively.

8. The grid-connected energy storage device according to any one of claims 1 to 7, characterized in that, The energy storage converter includes: A bidirectional AC / DC conversion unit is connected to the DC bus and is used to connect to the power grid.

9. The grid connection device for energy storage equipment according to claim 8, characterized in that, The bidirectional AC / DC conversion unit includes: Bus capacitors are connected between the DC buses.

10. An energy storage system, characterized in that, It includes the grid-connected energy storage device as described in any one of claims 1 to 9, and X energy storage devices; wherein X is an integer, and 1≤X≤N.

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