Power storage apparatus having plurality of storage battery modules connected in series, energy storage unit, and power supply system

Abstract

The present utility model relates to the energy storage technology. Disclosed are a power storage apparatus having a plurality of storage battery modules connected in series, an energy storage unit, and a power supply system. The power storage apparatus comprises a switch module, a storage battery pack, and a plurality of first functional units. A positive electrode of the storage battery pack is electrically connected to a positive line of a direct-current bus of the power supply system by means of the switch module, and a negative electrode of the storage battery pack is electrically connected to a negative line of the direct-current bus. The storage battery pack comprises a plurality of storage battery modules successively connected in series, and the first functional units and each of the storage battery modules are electrically connected to the direct-current bus by means of one of the first functional units; the direct-current bus is arranged between a direct-current output end of the power supply system and a load of a data center. The present utility model aims to solve the problem of unbalanced charging of battery cells between a plurality of storage battery modules connected in series.

Description

Power storage device, energy storage unit and power supply system with multiple battery modules connected in series

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on August 21, 2023, with application number 202322239273.9 and application name: "Storage device, energy storage unit and power supply system with multiple battery modules connected in series", the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The utility model relates to the technical field of energy storage, and in particular to an electricity storage device, an energy storage unit and a power supply system in which multiple battery modules are connected in series. Background Art

[0003] Data centers not only require large amounts of electricity to maintain the operation of equipment such as servers, storage devices, backup devices, and cooling systems, but also generally need to be equipped with corresponding battery packs for the data center's power supply system to prevent sudden interruptions in the mains power supply to the data center, which may cause data loss or damage to related equipment. In the event of an external power outage, the battery packs can still be used to power the data center and maintain normal operation of the data center (similarly, energy storage power stations also require battery packs for energy storage).

[0004] Data centers or energy storage power stations operate at higher voltages, requiring a larger number of battery cells to be connected in series to form a battery pack. Typically, several battery cells are connected in series or parallel to form a battery module, and then multiple battery modules are connected in series to form a battery pack.

[0005] Currently, this type of battery pack is generally connected to the DC bus between the DC output end of the power supply system and the load of the data center to draw power, and either the battery pack is charged directly using the DC bus, or a transformer unit is set between the DC bus and the battery pack so that all cells in the battery pack share a transformer unit for charging. However, this method is prone to uneven charging of cells between battery modules (for example, the cells in some battery modules are not fully charged, while the cells in some battery modules are overcharged).

[0006] The above content is only used to assist in understanding the technical solution of the present invention and does not constitute an admission that the above content is prior art.

[0007] Utility Model Content

[0008] The utility model provides a power storage device, an energy storage unit and a power supply system with multiple battery modules connected in series, aiming to solve the problem of uneven charging of battery cells among the multiple battery modules connected in series.

[0009] To achieve the above-mentioned objectives, the present invention proposes a storage device with multiple battery modules connected in series, wherein the storage device includes a switch module, a battery pack and multiple first functional units. The positive pole of the battery pack is electrically connected to the positive line of the DC bus of the power supply system via the switch module, and the negative pole of the battery pack is electrically connected to the negative line of the DC bus. The battery pack includes multiple battery modules connected in series in sequence, and each of the battery modules is electrically connected to the DC bus via one of the first functional units; the DC bus is arranged between the DC output end of the power supply system and the load of the data center.

[0010] The switch module is provided with a unidirectional conduction switch, a first conduction end of the unidirectional conduction switch is electrically connected to the positive electrode of the battery pack, a second conduction end of the unidirectional conduction switch is electrically connected to the positive line of the DC bus, and a conduction direction of the unidirectional conduction switch is from the first conduction end of the unidirectional conduction switch to the second conduction end of the unidirectional conduction switch.

[0011] Optionally, the unidirectional conducting switch is a diode, the anode of the diode is the first conducting end, and the cathode of the diode is the second conducting end;

[0012] Alternatively, the unidirectional conduction switch is a MOS transistor, and the power storage device further includes a control unit, wherein a control signal output end of the control unit is electrically connected to the gate of the MOS transistor; when the battery pack is in a non-discharge state, the control unit controls the MOS transistor to be in a cut-off state, and the conduction direction of the body diode in the MOS transistor is the same as the conduction direction of the unidirectional conduction switch; when the battery pack is in a discharge state, the MOS transistor is in a conduction state.

[0013] Optionally, a control unit is provided in each battery module.

[0014] The present invention further proposes an energy storage unit, comprising a second functional unit, a power distribution unit and at least one power storage device, wherein the power storage device is a power storage device with multiple batteries connected in series as described above; the second functional unit and the power distribution unit are connected in series in sequence between the DC output end of the power supply system and the load of the power supply system, and the power storage device is electrically connected to the DC bus between the second functional unit and the power distribution unit.

[0015] Optionally, the second functional unit is a unidirectional conducting device, and the conducting direction is from the DC output end to the load.

[0016] The present invention further proposes a power supply system, which includes a DC source and multiple energy storage units, wherein the energy storage units are the energy storage units described above, and each of the energy storage units is electrically connected to the DC output end of the DC source.

[0017] The beneficial effect of the technical solution of the present invention is that: by respectively configuring corresponding first functional units for multiple battery modules connected in series in the battery pack, the battery cells in each battery module can be independently charged by the corresponding first functional unit, so that the battery cells that are not fully charged can be independently charged using the first functional unit paired with it, and this will not cause the fully charged battery module to be overcharged, thereby achieving charging balance between the battery cells in multiple battery modules connected in series; at the same time, compared with the battery pack, the number of battery cells in each battery module is less, and the difference between the battery cells during charging and discharging will also be reduced, which will be easier to manage and balance; when the battery pack is discharging, if the voltages that can be provided by each battery module are not balanced, the battery module with low output voltage can also simultaneously draw power from the DC bus through the first functional unit paired with it and make up the voltage difference, thereby increasing the output voltage of the battery pack so that the battery pack can discharge its own power as much as possible before the cut-off voltage difference, giving full play to the battery's backup power storage capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG1 is a schematic structural diagram of an embodiment of a power storage device in which multiple battery modules are connected in series;

[0019] FIG2 is a schematic structural diagram of an embodiment of an energy storage unit of the present invention;

[0020] FIG3 is a schematic structural diagram of another embodiment of the energy storage unit of the present invention;

[0021] FIG4 is a schematic structural diagram of an embodiment of a power supply system of the present invention.

[0022] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the schemes in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0024] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0025] It should also be noted that when an element is referred to as being "fixed on" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element.

[0026] In addition, the descriptions of "first," "second," etc. in this utility model are for descriptive purposes only and should not be understood as indicating or implying their relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments can be combined with each other, but this must be based on the fact that they can be implemented by ordinary technicians in this field. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this utility model.

[0027] The present invention proposes a power storage device in which multiple battery modules are connected in series. Referring to FIG1 , the power storage device includes a switch module, a battery pack, and multiple first functional units. The positive electrode of the battery pack is electrically connected to the positive line of a DC busbar of a power supply system via the switch module, and the negative electrode of the battery pack is electrically connected to the negative line of the DC busbar. The battery pack includes multiple battery modules connected in series in sequence, and each of the battery modules is electrically connected to the DC busbar via one of the first functional units. The DC busbar is arranged between the DC output end of the power supply system and the load of the data center.

[0028] In this embodiment, the power storage device can be a power storage device arranged in a power supply system, which can be a power supply system of a data center. A DC source is provided in the power supply system, and a DC bus (divided into a positive line and a negative line) is provided between the DC output end of the DC source and the load of the data center, so that the DC source can supply power to the load of the data center through the DC bus.

[0029] The DC source can be connected to an external energy source (such as AC mains) and convert the external energy into DC power suitable for the load of the data center.

[0030] Optionally, the positive pole of the battery pack in the power storage device is electrically connected to the positive pole line of the DC bus through the switch module, and the negative pole of the battery pack is electrically connected to the negative pole line of the DC bus; wherein, the first conductive end of the switch module is electrically connected to the positive pole of the battery pack, and the second conductive end of the switch module is electrically connected to the positive pole line of the DC bus.

[0031] Optionally, the switch module is provided with a unidirectional conduction switch, the first conduction end of the unidirectional conduction switch is electrically connected to the positive pole of the battery pack, the second conduction end of the unidirectional conduction switch is electrically connected to the positive pole line of the DC bus, and the conduction direction of the unidirectional conduction switch is from the first conduction end of the unidirectional conduction switch to the second conduction end of the unidirectional conduction switch.

[0032] When the DC source of the power supply system is supplying power normally, the power supply system can directly use the DC source to supply power to the load via the DC bus. At this time, due to the unidirectional conduction function of the switch module, the current provided by the DC output end cannot flow to the battery pack through the switch module; when the DC source of the power supply system is supplying power abnormally and the battery pack needs to be enabled to discharge the DC bus to supply power to the load, the current output by the positive electrode of the battery pack can flow to the positive line of the DC bus through the switch module.

[0033] Optionally, the switch module may be a non-unidirectional conduction switch, and when the battery pack is in a non-discharging state, the switch module is in an off state. The switch module may be a contactor, a relay, or a low-loss non-unidirectional conduction switch device.

[0034] Among them, if the switch module is a non-unidirectional conductive switch, the power storage device may further include a control unit (not shown in the figure), and the control signal output end of the control unit is electrically connected to the control end of the switch module, so that the control unit can control the switch module to be closed or opened by outputting a corresponding control signal to the switch module; and if the switch module is in a closed state, the circuit between the first conductive end and the second conductive end inside it is in a conductive state, and if the switch module is in an open state, the circuit between the first conductive end and the second conductive end inside it is in a disconnected state.

[0035] Optionally, when the DC source of the power supply system is supplying power normally, the power supply system can directly use the DC source to supply power to the load through the DC bus. At this time, the battery pack does not need to discharge the DC bus, so the control unit controls the switch module to be in a disconnected state, so that the current provided by the DC output end cannot flow to the battery pack through the switch module; when the DC source of the power supply system is supplying power abnormally and the battery pack needs to be enabled to discharge the DC bus to supply power to the load, the control unit controls the switch module to be in a closed state, so that the current output from the positive pole of the battery pack can flow to the positive pole line of the DC bus through the switch module, and supply power to the load through the DC bus.

[0036] Optionally, a battery pack is provided with multiple battery modules connected in series, and the positive electrode of the first battery module in the series circuit can serve as the positive electrode of the battery pack, while the negative electrode of the first battery module is electrically connected to the positive electrode of the next battery module (and the negative electrode of the next battery module is electrically connected to the positive electrode of the next battery module), and so on, until the negative electrode of the last battery module serves as the negative electrode of the battery pack. Each battery module has multiple battery cells connected in series or in parallel.

[0037] In addition, the power storage device is provided with the same number of first functional units as battery modules, that is, one first functional unit is configured for each battery module. The positive input terminal of each first functional unit is electrically connected to the positive line of the DC bus, the negative input terminal of each first functional unit is electrically connected to the negative line of the DC bus, the positive output terminal of each first functional unit is electrically connected to the positive terminal of the corresponding battery module, and the negative output terminal of each first functional unit is electrically connected to the negative terminal of the corresponding battery module.

[0038] The first functional unit can be a unidirectional voltage transformer (e.g., a DC / DC (direct current to direct current) voltage power conversion unit) with a conduction direction from the DC bus to the battery module. The first functional unit can be used to convert the DC voltage received from the DC bus into a charging voltage compatible with the battery module and then output the converted voltage to the battery module. Furthermore, the first functional unit has a primary-to-secondary isolation design.

[0039] Optionally, the first functional unit can convert the received DC voltage into a charging voltage compatible with the battery module according to pre-set working parameters; or, the control end of the first functional unit is electrically connected to the control signal output end of the control unit (not shown in the figure) and is controlled by the control unit, so that the control unit can output a corresponding control signal to the first functional unit to set the working parameters of the first functional unit, so that the first functional unit can convert the received DC voltage into a corresponding DC voltage according to the charging requirements of the battery module (that is, the control unit can adjust the voltage converted by the first functional unit according to the charging requirements).

[0040] It should be noted that the control unit may be provided with a plurality of control signal output terminals, and may control various components (such as the switch module and / or the first functional unit) respectively through different control signal output terminals.

[0041] In this way, because each of the multiple series-connected battery modules in the battery pack is equipped with a corresponding first functional unit, each battery module can be independently charged through the corresponding first functional unit. That is, when the DC source of the power supply system is operating normally and the power supply system can directly use the DC source to power the load via the DC bus, if any battery module in the battery pack is not fully charged, the undercharged battery module can be independently charged using the first functional unit paired with it. This will not cause overcharging of the fully charged battery module, thereby achieving balanced charging of the cells among the multiple series-connected battery modules. At the same time, because the number of series-connected cells in each battery module is smaller, management is more efficient and replacement or maintenance is more convenient.

[0042] Optionally, when the DC source of the power supply system is abnormal and the battery pack needs to be enabled to discharge the DC bus to power the load, multiple battery modules connected in series in the battery pack can jointly provide power for the load. Moreover, when the voltages provided by the battery modules in the battery pack are not balanced (for example, some battery modules have low output voltages due to low stored power, which easily form a short-board effect during discharge), the battery modules with low output voltage can also simultaneously draw power from the DC bus through the first functional unit paired with it, thereby reducing their own discharge current, until the storage capacity (or output voltage) of all battery modules is roughly the same, achieving balanced discharge of multiple battery modules connected in series, thereby extending the discharge time of the battery pack. In scenarios with minimum operating voltage requirements, this solution can also increase the battery's discharge cut-off voltage, thereby releasing as much stored power as possible and extending the discharge time.

[0043] In addition, although the above-mentioned switch module is set between the positive pole of the battery pack and the positive pole of the DC bus, the switch module can also be set between the negative pole of the battery pack and the negative pole of the DC bus. Through corresponding logical control, the switch module can achieve the equivalent effect of setting the positive pole.

[0044] In one embodiment, based on the above embodiment, the switch module is a diode, the anode of the diode is the first conductive end, and the cathode of the diode is the second conductive end;

[0045] Alternatively, the switch module is a MOS tube, and the power storage device further includes a control unit, wherein a control signal output end of the control unit is electrically connected to the gate of the MOS tube; when the battery pack is in a non-discharge state, the control unit controls the MOS tube to be in a cut-off state, and the conduction direction of the body diode in the MOS tube is the same as the conduction direction of the diode; when the battery pack is in a discharge state, the MOS tube is in a conduction state.

[0046] In this embodiment, the switch module may be a diode or a MOS tube.

[0047] Optionally, if the switch module is a diode, the first conduction end of the switch module is the anode of the diode, the second conduction end of the switch module is the cathode of the diode, and the diode can automatically close or open the switch module by automatically detecting the voltage difference between the anode and the cathode.

[0048] Optionally, if the switch module is a MOS tube, the switch module has a control end, which is the gate of the MOS tube, and the gate of the MOS tube is electrically connected to the control signal output end of the control unit of the storage device. The control unit can control the MOS tube to be turned on or off by outputting a corresponding control signal to the gate of the MOS tube, thereby controlling the switch module to be closed or opened; wherein, if the switch module is a PMOS tube, the first conduction end of the switch module is the drain of the PMOS tube, and the second conduction end of the switch module is the source of the PMOS tube; if the switch module is an NMOS tube, the first conduction end of the switch module is the source of the NMOS tube, and the second conduction end of the switch module is the drain of the NMOS tube.

[0049] At the same time, the conduction direction of the body diode in the MOS tube is the same as the conduction direction of the diode.

[0050] Optionally, if the switching module is a diode, when the DC source of the power supply system can discharge normally to the DC bus, the cathode voltage of the diode will be greater than the anode voltage. At this time, the diode is in the cut-off state, and the switching module is automatically disconnected. The current provided by the DC output end cannot flow to the battery pack through the switching module; when the DC source of the power supply system cannot discharge normally to the DC bus, the anode voltage of the diode will be greater than the cathode voltage. At this time, the diode is in the on state, so that the current output from the positive electrode of the battery pack can flow to the positive line of the DC bus through the switching module.

[0051] Optionally, if the switch module is a MOS tube, when the DC source of the power supply system can discharge normally to the DC bus, there is no need to use the battery pack to power the load (that is, the battery pack is in a non-discharge state). Therefore, the control unit can control the MOS tube to be in a cut-off state, and the switch module is disconnected, and the current provided by the DC output end cannot flow to the battery pack through the switch module; when the DC source of the power supply system cannot discharge normally to the DC bus, the battery pack is in a discharge state, and the control unit can control the MOS tube to be in a conductive state, so that the current output from the positive electrode of the battery pack can flow to the positive line of the DC bus through the switch module.

[0052] It should be noted that if the current carrying capacity of the body diode of the MOS tube set separately in the switch module cannot meet the load power supply requirements, the MOS tube and the diode can be set in parallel in the switch module to enhance the current carrying capacity of the switch module so that the current output by the battery pack through the switch module can meet the load power supply requirements.

[0053] In one embodiment, based on the above embodiment, a control unit is provided in each battery module.

[0054] In this embodiment, the control unit provided in the battery module may be a battery management system (BMS).

[0055] The optional control unit within the battery module is responsible for monitoring and managing the charge and discharge of the batteries within the module. Furthermore, the control unit within the battery module collects signals from the module and reports the power levels monitored from each battery module to the overall control unit of the storage device. Functional and distributed integration is achieved between the control units within each battery module and the overall control unit of the storage device. The power supply system manages the entire system based on battery status, ensuring coordinated operation and providing early warnings in the event of a fault or insufficient power supply.

[0056] Referring to Figure 2 or Figure 3, the present invention further proposes an energy storage unit, including a second functional unit, a distribution unit and at least one power storage device, wherein the second functional unit and the distribution unit are connected in series between the DC output end of the power supply system and the load of the power supply system, and the power storage device is electrically connected to the DC bus between the second functional unit and the distribution unit.

[0057] It should be noted that the specific structure of any power storage device in the energy storage unit can refer to the above embodiments. Since this energy storage unit adopts all the technical solutions of all the above embodiments, it at least has all the technical effects brought about by the technical solutions of the above embodiments, which will not be described one by one here.

[0058] In this embodiment, the second functional unit and the power distribution unit in the energy storage unit are connected in series on the DC bus between the DC output end and the load, which is equivalent to the DC bus between the DC output end and the load (or the DC bus between the DC output end and the load) needing to pass through the second functional unit and the power distribution unit.

[0059] In addition, one power storage device can be provided in the energy storage unit (as shown in FIG1 ), or multiple power storage devices can be provided in parallel (as shown in FIG3 ), and the input / output of each power storage device must be electrically connected to the DC output end via the second functional unit, and electrically connected to the load via the power distribution unit.

[0060] Optionally, the second functional unit is a unidirectional conducting device, and the conducting direction is from the DC output end to the load.

[0061] Optionally, the second functional unit can be a unidirectional transformer unit (such as a DC / DC (direct current to direct current) voltage power conversion unit), and the conduction direction is from the DC output end to the load; the second functional unit can be used to convert the DC voltage received from the DC output end into a power supply unit that is compatible with the load power supply requirements. This solution can be applied to scenarios where a DC bus voltage is provided to reduce transmission losses; or it can be applied to scenarios where the existing DC bus voltage is lower than the operating voltage and the DC / DC performs a boost operation.

[0062] Optionally, each distribution unit can be connected to one or more loads; in addition to being used to connect to loads, the distribution unit can also be used to monitor the load status, such as whether the load has power supply requirements, the load power supply demand, etc.; that is, the distribution unit can serve as a circuit protection device and can have corresponding detection and metering functions (such as detecting whether there is a power storage device connected to one side of the load), and report the corresponding detection and metering to the control unit through a communication connection with the control unit. Among them, the distribution unit can be an output distribution unit (such as a distribution cabinet, a small busbar, etc.) to distribute the output power of the energy storage unit to the load; at the same time, the control unit can make the distribution unit act as a circuit switch by controlling whether the output distribution unit is working, that is, by controlling whether the distribution unit is working, the line between the power storage device and the load can be controlled to be conductive or disconnected.

[0063] In some optional embodiments, a controllable switch may be provided in the power distribution unit, and the control unit controls the controllable switch to be closed or opened, thereby correspondingly controlling the connection or disconnection of the line between the energy storage unit and the load.

[0064] Optionally, the second functional unit is configured to enable the DC source to supply power to the load and / or charge the power storage device through the second functional unit when the DC source is supplying power normally.

[0065] Optionally, when the DC source of the power supply system can discharge normally to the DC bus, the current output by the DC output terminal can be supplied to the load and the storage device after voltage conversion through the second functional unit to power the load and / or charge the storage device; wherein the second functional unit will convert the first voltage output by the DC output terminal into a second voltage that matches the load requirement voltage.

[0066] The present invention further proposes a power supply system. Referring to Figure 4, the power supply system includes a DC source and multiple energy storage units. The energy storage units can be distributed and arranged in different cabinets or equipment rooms. The specific structure of the energy storage unit refers to the above embodiment. Since the power supply system adopts all the technical solutions of all the above embodiments, it has at least all the technical effects brought about by the technical solutions of the above embodiments, which will not be repeated here.

[0067] The DC input terminal of each energy storage unit is electrically connected to the DC output terminal of the DC source; and the power distribution unit of the energy storage unit is responsible for connecting to the load of the data center.

[0068] Among them, on a single DC bus between the DC source and the load, a single energy storage unit can be set up, or multiple energy storage units can be set up in parallel to improve the ability to supply power to the load.

[0069] The above description is only part or preferred embodiments of the present invention. Neither the text nor the drawings can limit the scope of protection of the present invention. All equivalent structural transformations made by using the contents of the present invention specification and drawings under the overall concept of the present invention, or direct / indirect application in other related technical fields are included in the scope of protection of the present invention.

Claims

1. A power storage device with multiple battery modules connected in series, characterized in that: The power storage device includes a switch module, a battery pack and multiple first functional units. The positive electrode of the battery pack is electrically connected to the positive line of the DC bus of the power supply system through the switch module, and the negative electrode of the battery pack is electrically connected to the negative line of the DC bus. The battery pack includes multiple battery modules connected in series, and each of the battery modules is electrically connected to the DC bus through one of the first functional units; the DC bus is arranged between the DC output end of the power supply system and the load of the data center.

2. The power storage device with multiple battery modules connected in series according to claim 1, characterized in that: The switch module is provided with a unidirectional conduction switch, a first conduction end of the unidirectional conduction switch is electrically connected to the positive electrode of the battery pack, a second conduction end of the unidirectional conduction switch is electrically connected to the positive electrode line of the DC bus, and a conduction direction of the unidirectional conduction switch is from the first conduction end of the unidirectional conduction switch to the second conduction end of the unidirectional conduction switch.

3. The power storage device with multiple battery modules connected in series according to claim 2, characterized in that: The unidirectional conducting switch is a diode, the anode of the diode is the first conducting end, and the cathode of the diode is the second conducting end; Alternatively, the unidirectional conduction switch is a MOS tube, and the power storage device further includes a control unit, a control signal output end of the control unit is electrically connected to the gate of the MOS tube, and when the battery pack is in a non-discharging state, the control unit controls the MOS tube to be in a cut-off state, and the conduction direction of the body diode in the MOS tube is the same as the conduction direction of the unidirectional conduction switch; when the battery pack is in a discharging state, the MOS tube is in a conducting state.

4. The power storage device of claim 1, wherein: A control unit is arranged in each of the battery modules.

5. An energy storage unit, characterized in that: It comprises a second functional unit, a distribution unit and at least one power storage device, wherein the power storage device is a power storage device with multiple batteries connected in series as described in any one of claims 1 to 4; the second functional unit and the distribution unit are connected in series in sequence between the DC output end of the power supply system and the load of the power supply system, and the power storage device is electrically connected to the DC bus between the second functional unit and the distribution unit.

6. The energy storage unit according to claim 5, characterized in that: The second functional unit is a unidirectional conducting device, and the conducting direction is from the DC output end to the load.

7. A power supply system, characterized in that: It comprises a direct current source and a plurality of energy storage units, wherein the energy storage unit is the energy storage unit according to claim 5 or 6, and each of the energy storage units is electrically connected to a direct current output terminal of the direct current source.

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