Energy storage system and control method thereof

Abstract

The invention provides an energy storage system and a control method thereof, the energy storage system comprises a plurality of battery pack branches, a bus and an energy storage converter, each battery pack branch leads out a bus connecting end used for connecting the bus, each battery pack branch comprises a battery pack, a bidirectional direct current converter and a relay, and the relay is connected with the bus connecting end. The bidirectional direct-current converter and the relay are connected in parallel between the battery packs and the bus connecting end, the bidirectional direct-current converter and the relay are not connected to the energy storage system at the same time, the energy storage converter is connected to the bus, and the method comprises the steps that battery pack parameters, corresponding to the working state of the energy storage converter, of the battery packs are obtained, and the battery pack parameters comprise voltage parameters; according to the position relation between the voltage parameter of the battery pack in each battery pack branch and the corresponding reference voltage range, target equipment connected to the energy storage system in each battery pack branch of the energy storage system is determined; and controlling the target device of each battery pack branch to access the energy storage system and controlling the preset device to be connected out of the energy storage system.

Description

Technical Field

[0001] The present application relates to the technical field of energy storage systems, and in particular to an energy storage system and a control method thereof. Background Art

[0002] At present, energy storage systems built with large-capacity batteries are often required for application scenarios such as power generation side energy storage and grid side energy storage. Due to the limitation of the voltage resistance level of components, the large-capacity batteries in the energy storage system can only be connected in parallel. However, after the energy storage system has been running for a period of time, the batteries will be differentiated, the internal resistance and voltage of the batteries will be inconsistent, and the charge and discharge current will be unbalanced, resulting in circulating currents. The circulating current is uncontrollable and affects the life of the hardware. When replacing any battery in the energy storage system, it is necessary to manually adjust the voltage of the unreplaced battery to the voltage of the replaced battery before parallel connection can be performed. Therefore, additional charging and discharging equipment is required for charging and discharging, which wastes manpower. Summary of the invention

[0003] In view of this, the purpose of the present application is to at least provide an energy storage system and a control method thereof, by equipping each battery pack branch with a bidirectional DC converter and a relay connected in parallel, and arranging the bidirectional DC converter and the relay between the bus and the battery pack, and then obtaining the voltage parameters in the battery pack parameters of each battery pack corresponding to the working state of the energy storage inverter, and comparing the positional relationship between the voltage parameters and the corresponding reference voltage range, to determine whether to connect the bidirectional DC converter or relay in each battery pack branch to the energy storage system, so as to balance the battery pack voltage of the energy storage inverter under different working states, solve the technical problem of the high frequency of circulating current caused by the direct connection of the battery pack to the bus in the prior art, and achieve the technical effect of reducing the differences between each battery pack and reducing the number of occurrences of circulating current problems.

[0004] This application mainly includes the following aspects:

[0005] In a first aspect, an embodiment of the present application provides a control method for an energy storage system, wherein the energy storage system includes multiple battery pack branches, a bus and an energy storage inverter, wherein each battery pack branch leads to a bus connection terminal for connecting to the bus, each battery pack branch includes a battery pack, a bidirectional DC converter and a relay, the bidirectional DC converter and the relay are connected in parallel between the battery pack and the bus connection terminal, the bidirectional DC converter and the relay are not connected to the energy storage system at the same time, and the energy storage inverter is connected to the bus, wherein the method includes: obtaining the working state of each battery pack corresponding to the working state of the energy storage inverter Battery pack parameters, the battery pack parameters include voltage parameters, the working state is used to describe whether the energy storage inverter performs power transmission for the battery pack; according to the positional relationship between the voltage parameters of the battery pack in each battery pack branch and its corresponding reference voltage range, determine the target device connected to the energy storage system in each battery pack branch of the energy storage system, the target device is one of the bidirectional DC converter and the relay; control the target device of each battery pack branch to connect to the energy storage system and control the preset device to connect out of the energy storage system, the preset device is the other of the bidirectional DC converter and the relay.

[0006] Optionally, the working state of the energy storage inverter includes a non-working state, and the voltage parameter corresponding to the non-working state includes a battery pack voltage, and the reference voltage range corresponding to the battery pack voltage refers to the access voltage range corresponding to the bus voltage, wherein the target device connected to the energy storage system in each battery pack branch of the energy storage system is determined in the following manner: when the battery pack voltage corresponding to at least one battery pack branch does not belong to the access voltage range corresponding to the bus voltage, the target device and the charge and discharge state of the battery pack connected to each battery pack branch are determined based on the size relationship between each battery pack voltage and the limit value of the access voltage range; when the battery pack voltage corresponding to each battery pack branch belongs to the access voltage range corresponding to the bus voltage, the target device connected to each battery pack branch is a relay.

[0007] Optionally, the charge and discharge status of the target device and battery pack connected to each battery pack branch is determined based on the size relationship between each battery pack voltage and the limit value of the access voltage range, including: determining the corresponding numbers of high-voltage battery packs whose battery pack voltage is greater than the upper limit value of the access voltage range, low-voltage battery packs whose battery pack voltage is less than the lower limit value of the access voltage range, and conventional battery packs whose battery pack voltage falls within the access voltage range among multiple battery packs; and determining the charge and discharge status of the target device and battery pack connected to each battery pack branch based on the corresponding numbers of the high-voltage battery packs, the low-voltage battery packs, and the conventional battery packs.

[0008] Optionally, the charge and discharge state of the battery pack includes a charging state and a discharging state, and the target device connected to each battery pack branch and the charge and discharge state of the battery pack are determined in the following manner: when the number of high-voltage battery packs is zero, the target device of the low-voltage battery pack is determined to be a bidirectional DC converter and the corresponding charge and discharge state is a charging state, the target device of the battery pack other than the low-voltage battery pack is determined to be a relay and the corresponding charge and discharge state is a discharging state, and when the number of high-voltage battery packs is not zero, the target device of the high-voltage battery pack is determined to be a relay and the corresponding charge and discharge state is a discharging state, and the target devices of the battery packs other than the high-voltage battery pack are determined to be bidirectional DC converters and the corresponding charge and discharge states are charging states.

[0009] Optionally, the working state of the energy storage inverter includes a charging and discharging state, and the voltage parameters corresponding to the charging and discharging state include the single cell voltage of each battery pack, and the reference voltage range corresponding to the single cell voltage refers to the cell voltage range of the battery pack where it is located, wherein the target device connected to the energy storage system in each battery pack branch of the energy storage system is determined in the following manner: according to the charging and discharging state of the energy storage inverter, the outlier battery pack of the energy storage system is determined by determining the relationship between the voltage of each single cell of each battery pack and the limit value of the cell voltage range of the battery pack where it is located; the target device of the battery pack branch where the outlier battery pack is located is determined to be the bidirectional DC converter, and the target device of other battery packs except the outlier battery pack is determined to be the relay.

[0010] Optionally, the charge and discharge state includes a charging state and a discharging state, and the outlier battery pack of the energy storage system is determined in the following manner: when the energy storage inverter is in a charging state, a battery pack having at least one battery cell whose single cell voltage is greater than an upper limit value of its corresponding battery cell voltage range is determined as the outlier battery pack; when the energy storage inverter is in a discharging state, a battery pack having at least one battery cell whose single cell voltage is less than a lower limit value of its corresponding battery cell voltage range is determined as the outlier battery pack.

[0011] Optionally, after controlling the target device of each battery pack branch to connect to the energy storage system and controlling the preset device to connect out of the energy storage system, the method further includes: adjusting the preset battery pack parameters of the isolated battery pack, the preset battery pack parameters including the battery pack current; wherein, adjusting the preset battery pack parameters of the isolated battery pack includes: reducing the battery pack current of the isolated battery pack.

[0012] Optionally, the method also includes: obtaining the number of faulty battery packs among multiple battery packs, and calculating the failure ratio of the number of faulty battery packs among the multiple battery packs; determining an adjustment method for the working power of the energy storage inverter based on a comparison result between the fault ratio and a preset ratio; and based on the adjustment method, controlling the regular battery packs among the multiple battery packs except the faulty battery packs to output power.

[0013] Optionally, the adjustment method for the working power of the energy storage inverter is determined in the following manner: when the fault ratio is greater than a preset ratio, the adjustment method is determined to reduce the working power of the energy storage inverter; when the fault ratio is not greater than a preset ratio, the adjustment method is determined to maintain the working power of the energy storage inverter.

[0014] Optionally, the regular battery packs among the multiple battery packs except the faulty battery pack are controlled to output power in the following manner: the regular battery packs are controlled to output power according to a preset output power to reduce the operating power of the energy storage inverter, or the regular battery packs are controlled to output power according to the operating power of the energy storage inverter to maintain the operating power of the energy storage inverter.

[0015] In a second aspect, an embodiment of the present application further provides an energy storage system, comprising: a bus; an energy storage inverter connected to the bus; a plurality of battery pack branches, each battery pack branch leading out a bus connection terminal for connecting to the bus, each battery pack branch comprising a battery pack, a bidirectional DC converter and a relay, the bidirectional DC converter and the relay being connected in parallel between the battery pack and the bus connection terminal, the bidirectional DC converter and the relay being not connected to the energy storage system at the same time, and a controller being configured to execute a method as described in the first aspect or any possible implementation manner of the first aspect above, wherein each battery pack also comprises a battery management system, and the battery management system of each battery pack sends the battery pack parameters to the controller.

[0016] An energy storage system and a control method thereof provided in an embodiment of the present application, the energy storage system includes a plurality of battery pack branches, a bus and an energy storage inverter, wherein each battery pack branch leads to a bus connection end for connecting to the bus, each battery pack branch includes a battery pack, a bidirectional DC converter and a relay, the bidirectional DC converter and the relay are connected in parallel between the battery pack and the bus connection end, the bidirectional DC converter and the relay are not connected to the energy storage system at the same time, the energy storage inverter is connected to the bus, wherein the method includes: obtaining the battery of each battery pack corresponding to the working state of the energy storage inverter The battery pack parameters include voltage parameters, and the working state is used to describe whether the energy storage inverter performs power transmission for the battery pack; according to the positional relationship between the voltage parameters of the battery pack in each battery pack branch and its corresponding reference voltage range, the target device connected to the energy storage system in each battery pack branch of the energy storage system is determined, and the target device is one of the bidirectional DC converter and the relay; the target device of each battery pack branch is controlled to be connected to the energy storage system and the preset device is controlled to be connected out of the energy storage system, and the preset device is the other one of the bidirectional DC converter and the relay. By equipping each branch where a battery pack is located with a bidirectional DC converter and a relay connected in parallel, and arranging the bidirectional DC converter and the relay between the bus and the battery pack, and then obtaining the voltage parameters in the battery pack parameters of each battery pack corresponding to the working state of the energy storage inverter, and comparing the positional relationship between the voltage parameters and the corresponding reference voltage range, it is determined in each battery pack branch whether the bidirectional DC converter or relay is connected to the energy storage system, so as to balance the battery pack voltage of the energy storage inverter under different working states, thereby solving the technical problem of the high frequency of circulating current caused by the direct connection of the battery pack to the bus in the prior art, and achieving the technical effect of reducing the differences between the battery packs and reducing the number of occurrences of circulating current problems.

[0017] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, preferred embodiments are specifically cited below and described in detail with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 A schematic structural diagram of an energy storage system provided in an embodiment of the present application is shown.

[0020] Figure 2 A flow chart of a control method for an energy storage system provided in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0021] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. It should be understood that the drawings in the present application only serve the purpose of explanation and description and are not used to limit the scope of protection of the present application. In addition, it should be understood that the schematic drawings are not drawn in real proportion. The flowchart used in this application shows the operations implemented according to some embodiments of the present application. It should be understood that the operations of the flowchart can be implemented out of sequence, and the steps without logical context can be reversed in order or implemented simultaneously. In addition, those skilled in the art, under the guidance of the content of the present application, can add one or more other operations to the flowchart, or remove one or more operations from the flowchart.

[0022] In addition, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.

[0023] In recent years, the development of new energy technologies has been rapid, and has entered the stage of large-scale commercial application from the early stage of technical verification. For application scenarios such as power generation side energy storage and grid side energy storage, large-capacity battery energy storage systems are often required. Due to the limitations of the voltage resistance level of components, large-capacity battery systems can only be connected in parallel. However, the parallel connection of multiple battery clusters will cause problems such as pressure difference and circulation due to the inconsistency of the batteries themselves.

[0024] Based on this, the embodiment of the present application provides an energy storage system and a control method thereof, by equipping each branch where a battery pack is located with a bidirectional DC converter and a relay connected in parallel, and arranging the bidirectional DC converter and the relay between the bus and the battery pack, and then obtaining the voltage parameter in the battery pack parameter of each battery pack corresponding to the working state of the energy storage inverter, and comparing the positional relationship between the voltage parameter and its corresponding reference voltage range, to determine whether to connect the bidirectional DC converter or relay in each battery pack branch to the energy storage system, so as to balance the battery pack voltage of the energy storage inverter under different working states, solve the technical problem of the high frequency of circulating current caused by the direct connection of the battery pack to the bus in the prior art, and achieve the technical effect of reducing the differences between the battery packs and reducing the number of occurrences of the circulating current problem, as follows:

[0025] See also Figure 1 , Figure 1 This is a schematic diagram of the structure of an energy storage system provided in an embodiment of the present application. Figure 1 As shown, an energy storage system provided in an embodiment of the present application comprises a plurality of battery pack branches, busbars (BUS1 and BUS2) and an energy storage inverter PCS, wherein each battery pack branch leads out a busbar connection terminal for connecting to the busbar, each battery pack branch comprises a battery pack P, a bidirectional DC converter DCDC and a relay (S1 and S2), the bidirectional DC converter and the relay are connected in parallel between the battery pack and the busbar connection terminal, the bidirectional DC converter and the relay are not connected to the energy storage system at the same time, and the energy storage inverter is connected to the busbar.

[0026] That is to say, the bidirectional DC converter and the relay are connected in parallel and arranged between the battery pack and the bus, wherein the battery pack is connected to one end of the bidirectional DC converter and one end of the relay, and the other end of the bidirectional DC converter and the other end of the relay are connected as the bus connection end of the battery pack branch.

[0027] Specifically, for each battery pack, the battery pack leads out a positive terminal and a negative terminal, the positive terminal of the battery pack is connected to the positive terminal of one end of the relay and the positive terminal of one end of the bidirectional DC converter, the negative terminal of the battery pack is connected to the negative terminal of one end of the relay and the negative terminal of one end of the bidirectional DC converter, the positive terminal of the other end of the relay is connected to the positive terminal of the other end of the bidirectional DC converter and leads out a positive bus connection terminal for connecting to the positive bus, the negative terminal of the other end of the relay is connected to the negative terminal of the other end of the bidirectional DC converter and leads out a negative bus connection terminal for connecting to the negative bus, thereby realizing the bidirectional DC converter and the relay being connected in parallel and arranged between the battery pack and the bus connection terminal.

[0028] Specifically, when the bidirectional DC converter is in a working state, it is considered that the bidirectional DC converter is connected to the energy storage system; when the bidirectional DC converter is in a non-working state, it is considered that the bidirectional DC converter is not connected to the energy storage system; when the relay is in a closed state, it is considered that the relay is connected to the energy storage system; when the relay is in an open state, it is considered that the relay is not connected to the energy storage system.

[0029] That is to say, by controlling the bidirectional DC converter to be in working state and the relay to be in disconnected state, or controlling the bidirectional DC converter to be in non-working state and the relay to be in closed state, only one of the bidirectional DC converter and the relay is connected to the energy storage system.

[0030] The bidirectional DC converter is used to adjust the DC voltage output from or flowing into the battery pack, that is, when the bidirectional DC converter adjusts the DC voltage input to the battery pack or the voltage output by the battery pack, the bidirectional DC converter is considered to be in a working state. In other words, when the DC voltage input to the battery pack or the voltage output by the battery pack does not flow through the bidirectional DC converter, it is considered that the bidirectional DC converter does not perform any voltage adjustment and is in a non-working state; when the DC voltage input to the battery pack or the voltage output by the battery pack flows through the bidirectional DC converter, it is considered that the bidirectional DC converter performs any voltage adjustment and is in a working state.

[0031] like Figure 1 As shown, the energy storage system also includes a controller EMS configured to execute a control method for the energy storage system. Figure 2 , Figure 2 This is a flow chart of a control method for an energy storage system provided in an embodiment of the present application. Figure 2 As shown, the method includes:

[0032] S101: Obtain battery pack parameters of each battery pack corresponding to the working state of the energy storage converter.

[0033] Each battery pack also includes a battery management system, and the battery management system of each battery pack sends the battery pack parameters of each battery pack to the controller. In other words, the battery management system of each battery pack sends its own battery pack parameters to the controller, so that the controller obtains the battery pack parameters of each battery pack of the energy storage system.

[0034] Specifically, each battery pack includes multiple cells, and multiple cells are connected in series or in parallel to form a battery pack. The battery pack parameters are used to describe the working state of the battery pack, and generally include the battery pack voltage, battery pack current, state of charge SOC, battery pack temperature, and the cell voltage of each cell.

[0035] Among them, the working state of the energy storage converter is used to describe whether the energy storage converter performs power transmission for the battery pack, and different working states correspond to different battery pack parameters of the battery pack, and the battery pack parameters include voltage parameters. That is to say, when the energy storage converter performs power transmission for the battery pack, it is necessary to obtain a voltage parameter, and when the energy storage converter does not perform power transmission for the battery pack, it is necessary to obtain another voltage parameter. Two different voltage parameters can also be obtained at the same time, but the voltage parameters corresponding to different working states need to be considered when comparing with the reference voltage range later.

[0036] Among them, the working state of the energy storage inverter includes a non-working state and a charging and discharging state, that is, when the working state of the energy storage inverter is in the non-working state, the energy storage inverter does not perform power transmission for the battery pack, and the battery pack cannot transmit power to external devices; when the working state of the energy storage inverter is in the charging and discharging state, the energy storage inverter performs power transmission for the battery pack, and power transmission is performed between the battery pack and external devices.

[0037] Exemplarily, all battery packs of the energy storage system also include a total battery management system, and the controller of the energy storage system is connected to the battery management system of each battery pack through the total battery management system, and the total battery management system is configured to: determine whether each battery pack is a faulty battery pack based on the battery pack parameters transmitted by the battery management system of each battery pack, and send the number and quantity of the faulty battery packs and the number and number of regular battery packs other than the faulty battery packs to the controller, so that the controller determines to control the battery pack branch where the regular battery pack is located to connect to the energy storage system, that is, to control the bidirectional DC converter or relay of the battery pack branch where the regular battery pack is located to connect to the energy storage system, and control the battery pack branch where the faulty battery pack is located to connect out of the energy storage system, that is, to control the bidirectional DC converter and relay of the battery pack branch where the faulty battery pack is located to connect out of the energy storage system, that is, to control the bidirectional DC converter and relay of the battery pack branch where the faulty battery pack is located to connect out of the energy storage system, that is, the bidirectional DC converter is in a non-working state and the relay is in a disconnected state.

[0038] Exemplarily, whether a battery pack is a faulty battery pack can be determined by determining whether each battery pack parameter falls within its corresponding preset parameter range. If any battery pack parameter does not fall within its corresponding preset parameter range, the battery pack is considered to be a faulty battery pack.

[0039] For example, the energy storage converter can be connected to the power grid to connect the energy storage system to the grid, that is, the energy storage converter supplies power to the power grid through the busbar from the power supply of each battery pack connected to the energy storage system. Alternatively, the energy storage converter is connected to an external power supply device to charge the battery packs connected to the energy storage system through the busbar from the power supply of the external power supply device.

[0040] Specifically, the method also includes: obtaining the number of faulty battery packs in a plurality of battery packs, and calculating the fault ratio of the number of faulty battery packs in the plurality of battery packs; determining an adjustment method for the working power of the energy storage inverter based on a comparison result between the fault ratio and a preset ratio; and based on the adjustment method, controlling the regular battery packs other than the faulty battery packs in the plurality of battery packs to output power.

[0041] That is to say, when the working state of the energy storage converter is the charge and discharge state, the number of faulty battery packs in the multiple battery packs and the number of regular battery packs of regular battery packs other than the faulty battery packs are obtained, and the ratio of the number of faulty battery packs to the total number of multiple battery packs is used as the fault ratio. The fault ratio is compared with the preset ratio to determine the adjustment method for increasing or decreasing the working power of the energy storage converter, and then the output power of the regular battery pack is correspondingly controlled according to the adjustment method so that the working power of the energy storage converter meets the adjustment method.

[0042] Specifically, the adjustment method for the working power of the energy storage inverter is determined in the following way: when the fault ratio is greater than a preset ratio, the adjustment method is determined to reduce the working power of the energy storage inverter; when the fault ratio is not greater than a preset ratio, the adjustment method is determined to maintain the working power of the energy storage inverter.

[0043] That is to say, when the fault ratio is greater than the preset ratio, it is considered that the fault ratio is large. At this time, as long as the number of conventional battery packs is not zero, the adjustment method is determined to reduce the working power of the energy storage inverter to prevent the conventional battery packs from being unable to support the working power of the energy storage inverter before the reduction; when the fault ratio is greater than or equal to the preset ratio, it is considered that the number of conventional battery packs can support the working power of the energy storage inverter, and then, the adjustment method is to maintain the working power of the energy storage inverter.

[0044] Specifically, the conventional battery packs except the faulty battery pack among the multiple battery packs are controlled to output power in the following manner: the conventional battery packs are controlled to output power according to a preset output power to reduce the operating power of the energy storage inverter, or the conventional battery packs are controlled to output power according to the operating power of the energy storage inverter to maintain the operating power of the energy storage inverter.

[0045] That is to say, when the fault ratio is greater than the preset ratio, it is only necessary to control the conventional battery pack to output power according to the preset output power, that is, the working power of the energy storage inverter is the product of the preset output power and the number of conventional battery packs. When the fault ratio is less than or equal to the preset ratio, the ratio of the working power of the energy storage inverter to the number of conventional batteries is used as the output power of each conventional battery pack. Among them, the relay corresponding to the conventional battery pack is in a closed state for power output.

[0046] Exemplarily, if the energy storage system includes four battery packs, the operating power of the PCS is 110kW. If the preset ratio is 50%, then when the number of faulty battery packs is ≤2, the ratio of 110kW power to the number of conventional batteries is used as the output power of each conventional battery pack. When the fault ratio is greater than 50%, that is, when the number of faulty battery packs is ≥3, the product of the preset output power of the conventional battery pack and the number of conventional battery packs is used to reduce the operating power of the energy storage inverter.

[0047] Exemplarily, the controller is also configured to limit the output current of each battery pack according to the output power of each conventional battery pack, and when the output current of any battery pack is greater than the maximum current corresponding to the output power, control the relay of the conventional battery pack to be in a disconnected state to prevent damage to the device.

[0048] Exemplarily, each battery pack branch also includes a fuse connected in series on the battery pack branch. If the controller does not limit the output current of the battery pack, the battery management system BMS of each battery pack detects the output current of each battery pack and controls the relay to be in the disconnected state when overcurrent is determined. The fuse of each battery pack branch will also blow when the current is too large, so as to protect the energy storage system.

[0049] S102: Determine a target device connected to the energy storage system in each battery pack branch of the energy storage system according to a positional relationship between the voltage parameter of the battery pack in each battery pack branch and its corresponding reference voltage range.

[0050] Wherein, the target device is one of the bidirectional DC converter and the relay.

[0051] Specifically, the working state of the energy storage inverter includes a non-working state, the voltage parameter corresponding to the non-working state includes a battery pack voltage, and the reference voltage range corresponding to the battery pack voltage refers to the access voltage range corresponding to the bus voltage; the working state of the energy storage inverter includes a charging and discharging state, and the voltage parameter corresponding to the charging and discharging state includes a single cell voltage of each battery pack, and the reference voltage range corresponding to the single cell voltage refers to the cell voltage range of the battery pack.

[0052] That is to say, when the working state of the energy storage converter is the non-working state, the controller needs to compare the battery pack voltage of each battery pack with the access voltage range corresponding to the bus voltage, and determine the bidirectional DC converter or relay in the branch where each battery pack is located to access the energy storage system based on the comparison result. That is to say, before grid connection, the battery pack voltage of each battery pack is compared with the bus voltage to reduce the difference in battery pack voltage and maintain the consistency of each battery pack. When the working state of the energy storage converter is the charging and discharging state, the controller needs to compare the single cell voltage of each battery pack with the cell voltage range of the battery pack where it is located, and determine whether each battery pack is an outlier battery pack based on the comparison result, and determine the bidirectional DC converter or relay in the branch where the outlier battery pack and other battery packs other than the outlier battery pack are respectively located to access the energy storage system. That is to say, after grid connection, the battery pack voltage of each battery pack is the same as the bus voltage, and then, it is necessary to determine whether there is a difference between the single cells of each battery pack to reduce the difference in cell voltage in each battery pack and maintain the consistency in the battery pack.

[0053] Specifically, when the working state of the energy storage inverter is a non-working state, the target device connected to the energy storage system in each battery pack branch of the energy storage system is determined in the following manner: when the battery pack voltage corresponding to at least one battery pack branch does not belong to the access voltage range corresponding to the bus voltage, the target device connected to each battery pack branch and the charge and discharge state of the battery pack are determined based on the size relationship between each battery pack voltage and the limit value of the access voltage range; when the battery pack voltage corresponding to each battery pack branch belongs to the access voltage range corresponding to the bus voltage, the target device connected to each battery pack branch is a relay.

[0054] Exemplarily, the product of the bus voltage and the preset error ratio plus the bus voltage is used as the upper limit of the access voltage range corresponding to the bus voltage, and the bus voltage minus the product of the bus voltage and the preset error ratio is used as the lower limit of the access voltage range corresponding to the bus voltage. Furthermore, whether the battery pack voltage is within the access voltage range is used to determine whether power transmission between the battery pack and the bus is allowed. The preset error ratio can be set to 2%.

[0055] Furthermore, for each battery pack, when the battery pack voltage of the battery pack meets the access voltage range corresponding to the bus voltage, it is considered that there is no need to adjust the battery pack voltage, and the battery pack can be directly connected to the bus. Then, the relay of the battery pack branch where the battery pack is located is taken as the target device, and the relay corresponding to the battery pack is controlled to be in a closed state to connect the relay to the energy storage system, and control the power transmission between the battery pack and the bus.

[0056] Among them, for each battery pack, when the battery pack voltage of the battery pack does not meet the access voltage range corresponding to the bus voltage, it is considered that there is a large difference between the battery pack and the bus voltage, and direct access to the bus will affect the bus voltage and may generate circulating current, and thus, the battery pack voltage needs to be adjusted. At this time, it is necessary to determine the positional relationship between each battery pack voltage and the upper and lower limits of the access voltage range to determine the target device of each battery pack branch and to determine the corresponding charge and discharge state of each battery pack in order to balance the voltage of each battery pack.

[0057] Specifically, the charge and discharge status of the target device and battery pack connected to each battery pack branch is determined based on the size relationship between each battery pack voltage and the limit value of the access voltage range, including: determining the corresponding numbers of high-voltage battery packs whose battery pack voltage is greater than the upper limit value of the access voltage range, low-voltage battery packs whose battery pack voltage is less than the lower limit value of the access voltage range, and conventional battery packs whose battery pack voltage falls within the access voltage range among multiple battery packs; and determining the charge and discharge status of the target device and battery pack connected to each battery pack branch based on the corresponding numbers of the high-voltage battery packs, the low-voltage battery packs, and the conventional battery packs.

[0058] That is to say, the positional relationship between each battery pack voltage and the access voltage range is determined, and the positional relationship includes the battery pack voltage belonging to the access voltage range, the battery pack voltage being greater than the upper limit of the access voltage range, and the battery pack voltage being less than the lower limit of the access voltage range. Among them, the battery pack whose battery pack voltage is greater than the upper limit of the access voltage range is regarded as a high-voltage battery pack, the battery pack whose battery pack voltage is less than the lower limit of the access voltage range is regarded as a low-voltage battery pack, and the battery pack whose battery pack voltage belongs to the access voltage range is regarded as a normal battery pack.

[0059] Among them, since the battery pack voltage of each battery pack connected to the bus will change, the bus voltage will also change accordingly, and the access voltage range of the bus voltage will also change. It is necessary to determine in real time the positional relationship between the battery pack voltage and the access voltage range corresponding to the current bus voltage, so that when each battery pack voltage belongs to the access voltage range corresponding to the current bus voltage, the target device of each battery pack branch is determined to be a relay.

[0060] Furthermore, the target device and the charge and discharge status of each battery pack are determined by the number of battery packs at various positional relationships according to the battery pack voltage, so as to determine the discharging battery packs and the charging battery packs among the multiple battery packs in the energy storage system, and balance the battery pack voltage by flowing the electric energy of the discharging battery pack into the charging battery pack.

[0061] Specifically, the charge and discharge state of the battery pack includes a charging state and a discharging state, and the target device connected to each battery pack branch and the charge and discharge state of the battery pack are determined in the following manner: when the number of high-voltage battery packs is zero, the target device of the low-voltage battery pack is determined to be a bidirectional DC converter and the corresponding charge and discharge state is a charging state, the target device of the battery pack other than the low-voltage battery pack is determined to be a relay and the corresponding charge and discharge state is a discharging state, and when the number of high-voltage battery packs is not zero, the target device of the high-voltage battery pack is determined to be a relay and the corresponding charge and discharge state is a discharging state, and the target devices of the battery packs other than the high-voltage battery pack are determined to be bidirectional DC converters and the corresponding charge and discharge states are charging states.

[0062] That is to say, when the number of high-voltage battery packs is zero, the battery pack voltage of the conventional battery pack in the multiple battery packs is greater than the battery pack voltage of the low-voltage battery pack. Furthermore, the conventional battery pack is used as a discharge battery pack, and the low-voltage battery pack is used as a charge battery pack, so as to control the relay of the conventional battery pack to be connected to the energy storage system and the bidirectional DC converter to be connected out of the energy storage system, and the charge and discharge state of the conventional battery pack is set to the discharge state, that is, the electric energy on the relay flows from the conventional battery pack to the bus; the bidirectional DC converter of the low-voltage battery pack is controlled to be connected to the energy storage system and the relay is connected out of the energy storage system, and the charge and discharge state of the low-voltage battery pack is set to the charge state, that is, the electric energy on the bidirectional DC converter flows from the bus into the low-voltage battery pack. Thus, the electric energy of the conventional battery pack flows into the low-voltage battery pack through the bus until the voltage of each battery pack belongs to the access voltage range.

[0063] That is to say, when the number of the high-voltage battery packs is not zero, the multiple battery packs include any of the following: a high-voltage battery pack, a conventional battery pack; a high-voltage battery pack, a low-voltage battery pack; a high-voltage battery pack, a conventional battery pack, and a low-voltage battery pack. At this time, the battery pack voltage of the high-voltage battery pack is greater than the battery pack voltage of the other battery packs except the high-voltage battery pack. Furthermore, the high-voltage battery pack is used as a discharge battery pack, and the other battery packs except the high-voltage battery pack are used as charging battery packs to control the relay of the high-voltage battery pack to be connected to the energy storage system and the bidirectional DC converter to be connected out of the energy storage system, and the charge and discharge state of the high-voltage battery pack is set to the discharge state, that is, the electric energy on the relay flows from the high-voltage battery pack to the bus; the bidirectional DC converter of the other battery packs except the high-voltage battery pack is controlled to be connected to the energy storage system and the relay is connected out of the energy storage system, and the charge and discharge state of the other battery packs is set to the charging state, that is, the electric energy on the bidirectional DC converter flows from the bus to the other battery packs. Thus, the electric energy of the high-voltage battery pack flows into the other battery packs through the bus until the voltage of each battery pack belongs to the access voltage range.

[0064] Exemplarily, the battery pack voltage can also be directly compared with the bus voltage, and the access voltage range corresponding to the bus voltage is equal to the bus voltage. That is to say, only when each battery pack voltage is equal to the bus voltage, the target device of each battery pack branch is determined to be a relay; when there is a battery pack whose battery pack voltage is greater than the bus voltage, the target device of the branch where the battery pack with a voltage greater than the bus voltage is located is set to a relay and adjusted to a discharge state, and the target devices of other battery pack branches are set to a bidirectional DC converter and adjusted to a charging state; when there is no battery pack whose battery pack voltage is greater than the bus voltage, the target device corresponding to the battery pack with a battery pack voltage less than the bus voltage is set to a bidirectional DC converter and adjusted to a charging state, and the target devices of other battery pack branches are set to relays and adjusted to a discharge state.

[0065] S103: Control the target device of each battery pack branch to connect to the energy storage system and control the preset device to connect out of the energy storage system.

[0066] Wherein, the preset device is the other one of the bidirectional DC converter and the relay.

[0067] That is to say, before grid connection, when a battery pack that does not meet the access voltage range corresponding to the bus voltage is determined, the target equipment of the branch where each battery pack is located is connected to the energy storage system according to the positional relationship between the battery pack voltage and the access voltage range, and the preset equipment of its branch is connected out of the energy storage system, so that when the voltage of each battery pack falls within the access voltage range, the relays of each battery pack are controlled to connect to the energy storage system and the bidirectional DC converter is connected out of the energy storage system, so that the energy storage inverter can be connected to the grid and electric energy can be transmitted between the battery pack and the power grid without consuming power through the bidirectional DC converter.

[0068] That is to say, since the bidirectional DC converter will adjust the voltage, the voltage of the battery pack will be reduced before it is connected to the power grid, which will cause power loss. Furthermore, the present application avoids power loss caused by only using a bidirectional DC converter by connecting the bidirectional DC converter and the relay in parallel, thereby increasing power output efficiency.

[0069] Wherein, the working state of the energy storage inverter includes a charging and discharging state, and the voltage parameters corresponding to the charging and discharging state include the single cell voltage of each battery pack, and the reference voltage range corresponding to the single cell voltage refers to the cell voltage range of the battery pack where it is located. Wherein, the target device connected to the energy storage system in each battery pack branch of the energy storage system is determined in the following manner: according to the charging and discharging state of the energy storage inverter, the outlier battery pack of the energy storage system is determined by determining the relationship between the voltage of each single cell of each battery pack and the limit value of the cell voltage range of the battery pack where it is located; the target device of the battery pack branch where the outlier battery pack is located is determined to be the bidirectional DC converter, and the target device of other battery packs except the outlier battery pack is determined to be the relay.

[0070] After controlling the target device of each battery pack branch to connect to the energy storage system and controlling the preset device to connect out of the energy storage system, the method further includes: adjusting the preset battery pack parameters of the isolated battery pack, the preset battery pack parameters including the battery pack current; wherein, adjusting the preset battery pack parameters of the isolated battery pack includes: reducing the battery pack current of the isolated battery pack.

[0071] Among them, when the working power of the energy storage inverter is not zero, that is, when the working state of the energy storage inverter is the charging and discharging state, the voltage on the bus has been adjusted before the grid connection, and then, the battery pack synchronization during the charging and discharging process is achieved by adjusting the outlier battery pack. For each battery pack, the single cell voltage of each battery cell in the battery pack is obtained, and it is determined whether the battery pack is an outlier battery pack, and there are outlier cells in the outlier battery pack. After the outlier battery pack is determined, the bidirectional DC converter of the battery pack branch where the outlier battery pack is located is controlled to be in a working state, and the relay of the battery pack branch where the outlier battery pack is located is controlled to be in a disconnected state, and the battery pack current of the outlier battery pack is adjusted accordingly to maintain the consistency within the battery pack and the consistency with other battery packs.

[0072] Among them, the cell voltage range of each battery pack may be different. For each battery pack, the cell voltage range of the battery pack is determined in the following manner: sort each single cell of the battery pack, determine the middle value of the single cell voltage according to the sorting result, multiply the middle value by the preset cell error ratio to obtain the product, use the sum of the middle value and the product as the upper limit value of the cell voltage range of the battery pack, and use the difference between the middle value and the product as the lower limit value of the cell voltage range of the battery pack. Among them, the preset cell error ratio can be the same as or different from the preset error ratio of the access voltage range corresponding to the calculated bus voltage.

[0073] In general, for each battery pack, the positional relationship between the single cell voltage of each battery cell of the battery pack and the battery cell voltage range of the battery pack is determined. When the single cell voltage of the battery cell is greater than the upper limit of the battery cell voltage range of the battery pack, the voltage of the battery cell is considered to be too high. When the single cell voltage of the battery cell is less than the lower limit of the battery cell voltage range of the battery pack, the voltage of the battery cell is considered to be too low. When the single cell voltage of the battery cell belongs to the battery cell voltage range of the battery pack, the voltage of the battery cell is considered to be normal. When the working state of the energy storage converter is the charge and discharge state, different charge and discharge states correspond to different methods of determining outlier battery packs. In a charge and discharge state, an abnormal condition corresponding to only one battery cell will be considered as an outlier battery pack.

[0074] Specifically, the charge and discharge state includes a charging state and a discharging state, and the outlier battery pack of the energy storage system is determined in the following manner: in the charging state of the energy storage inverter, a battery pack in which the single cell voltage of at least one battery cell is greater than the upper limit value of the corresponding battery cell voltage range is determined as the outlier battery pack; in the discharging state of the energy storage inverter, a battery pack in which the single cell voltage of at least one battery cell is less than the lower limit value of the corresponding battery cell voltage range is determined as the outlier battery pack.

[0075] Among them, when the energy storage inverter is in the charging state, each battery pack is charged at this time. In order to prevent the voltage of a battery pack from being too high, an alarm trip may be generated, and then, the problem of excessive voltage of a single cell is mainly solved. Then, when the energy storage inverter is in the charging state, only the battery pack whose single cell voltage is greater than the upper limit value of its corresponding battery cell voltage range is determined as an outlier battery pack, and the target device of the battery pack branch where the outlier battery pack is located is set to a bidirectional DC converter, and the target devices of other battery packs except the outlier battery pack are determined to be relays.

[0076] When the energy storage inverter is in the discharge state, each battery pack discharges externally. In order to prevent the voltage of a battery pack from being too low, which may cause the battery pack to be over-discharged and affect the service life of the battery pack, the problem of too low voltage of the single cell is mainly solved. Then, when the energy storage inverter is in the discharge state, only the battery pack whose single cell voltage is less than the lower limit of its corresponding battery cell voltage range is determined as an outlier battery pack, and the target device of the battery pack branch where the outlier battery pack is located is set to a bidirectional DC converter, and the target devices of other battery packs except the outlier battery pack are determined to be relays.

[0077] That is to say, when the energy storage system initially enters the charge and discharge state, the voltage and current of each battery pack are basically the same. After running for a period of time, the voltage of the single cells in each battery pack will be different. Since the battery packs are all connected to the bus for charging and discharging, the difference between the voltages of each battery pack is small, and it is difficult to determine the outlier battery pack. Therefore, the outlier battery pack can be determined by detecting the voltage of the single cells in each battery pack. If the charge and discharge state of the energy storage system is a charging state, the electric energy on the power grid is transmitted to each battery pack. At this time, when the single cell voltage of the battery cell in the isolated battery pack is greater than the upper limit of the battery cell voltage range, it is necessary to connect to the energy storage system through a bidirectional DC converter to reduce the battery pack current of the isolated battery pack to slow down the charging rate, thereby facilitating the synchronous charging of the isolated battery pack and other battery packs; if the charge and discharge state of the energy storage system is a discharging state, the electric energy of each battery pack is transmitted to the power grid. At this time, when the single cell voltage of the battery cell in the isolated battery pack is less than the lower limit of the battery cell voltage range, it is necessary to connect to the energy storage system through a bidirectional DC converter to reduce the battery pack current of the isolated battery pack to prevent the battery pack from being over-discharged, thereby facilitating the synchronous discharge of the isolated battery pack and other battery packs.

[0078] Furthermore, when there are no isolated cells in the isolated battery pack, the bidirectional DC converter is controlled to connect to the energy storage system, and the relay is controlled to be in a closed state to control the isolated battery pack to charge and discharge according to the battery pack current required for the output power.

[0079] Exemplarily, the controller EMS of the present application can use high-performance control chips, such as ARM, DSP, etc., and configure communication interfaces and I / O ports at the same time, and can execute 485 communication, CAN communication, Ethernet and other communication methods. EMS communicates with BMS, PCS and other devices to obtain information such as battery pack parameters in real time, so as to execute corresponding control strategies for the acquired parameters and increase system operation efficiency. In addition, the battery pack can adopt a high-voltage mode, such as a conventional 600-900V, 1000-1500V system, to adapt to the DC voltage operating range of the mainstream PCS.

[0080] For example, since the bidirectional DC converter is only used for balancing the battery pack, it does not need to be set according to the maximum power that each battery pack can output, and thus a low-power bidirectional DC converter can be selected to reduce costs. The relay uses a hybrid solid-state relay, which does not arc when the high voltage is cut off under load, increases the service life, and can be flexibly connected to and from the battery pack.

[0081] Furthermore, the present application can connect battery packs of different SOCs to the energy storage system through a bidirectional DC converter, so as to automatically balance and level the energy storage system before grid connection, without the need for manual leveling and alignment through charging and discharging equipment, saving manpower and equipment costs. Moreover, after grid connection, the consistency of the battery pack can still be balanced through the bidirectional DC converter, and the circulating current between battery clusters can be controlled; when the battery pack is normally charged and discharged, only the relay is controlled to be in a closed state, and the power range is increased to prevent the power drop caused by only setting the bidirectional DC converter between the battery pack and the bus; when there is a faulty battery pack, it does not affect the overall operation of the system, improves the overall availability of the system, and reduces the downtime loss caused by single-cell failure; the battery pack operation and replacement are more convenient, and the faulty pack can be removed and shielded without affecting the system operation; the battery pack high-voltage mode matches the conventional PCS voltage range, and the overall system conversion efficiency is high; new and old battery packs can also be mixed, and the voltage of each battery pack can be balanced to increase the service life of the battery pack.

[0082] Based on the same application concept, an embodiment of the present application further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the control method provided in the above embodiment are executed.

[0083] Specifically, the storage medium can be a general storage medium, such as a mobile disk, a hard disk, etc. When the computer program on the storage medium is run, the above method can be executed, by equipping each branch where the battery pack is located with a bidirectional DC converter and a relay connected in parallel, and arranging the bidirectional DC converter and the relay between the bus and the battery pack, and then obtaining the voltage parameters in the battery pack parameters of each battery pack corresponding to the working state of the energy storage inverter, and comparing the positional relationship between the voltage parameters and the corresponding reference voltage range to determine whether the bidirectional DC converter or relay is connected to the energy storage system in each battery pack branch, so as to balance the battery pack voltage of the energy storage inverter under different working states, thereby solving the technical problem of the high frequency of circulating current caused by the direct connection of the battery pack to the bus in the prior art, and achieving the technical effect of reducing the differences between the battery packs and reducing the number of occurrences of circulating current problems.

[0084] Those skilled in the art can clearly understand that, for the convenience and simplicity of description, the specific working process of the system and device described above can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here. In the several embodiments provided in the present application, it should be understood that the disclosed system, device and method can be implemented in other ways. The device embodiments described above are merely schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some communication interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0085] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0086] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0087] If the function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a non-volatile computer-readable storage medium that is executable by a processor. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM), random access memory (RAM), disk or optical disk, etc., various media that can store program codes.

[0088] The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A control method for an energy storage system, characterized in that: The energy storage system includes a plurality of battery pack branches, a busbar and an energy storage converter, wherein each battery pack branch leads to a busbar connection end for connecting to the busbar, each battery pack branch includes a battery pack, a bidirectional DC converter and a relay, the bidirectional DC converter and the relay are connected in parallel between the battery pack and the busbar connection end, the bidirectional DC converter and the relay are not connected to the energy storage system at the same time, and the energy storage converter is connected to the busbar, Wherein, the method comprises: Acquire battery pack parameters of each battery pack corresponding to the working state of the energy storage converter, wherein the battery pack parameters include voltage parameters, and the working state is used to describe whether the energy storage converter performs power transmission for the battery pack; Determine a target device connected to the energy storage system in each battery pack branch of the energy storage system according to the positional relationship between the voltage parameter of the battery pack in each battery pack branch and its corresponding reference voltage range, wherein the target device is one of the bidirectional DC converter and the relay; The target device of each battery pack branch is controlled to be connected to the energy storage system and the preset device is controlled to be connected out of the energy storage system, wherein the preset device is the other one of the bidirectional DC converter and the relay.

2. The method according to claim 1, characterized in that The working state of the energy storage converter includes a non-working state, the voltage parameter corresponding to the non-working state includes a battery pack voltage, and the reference voltage range corresponding to the battery pack voltage refers to an access voltage range corresponding to the bus voltage. The target device connected to the energy storage system in each battery pack branch of the energy storage system is determined in the following manner: When the battery pack voltage corresponding to at least one battery pack branch does not belong to the access voltage range corresponding to the bus voltage, determining the charge and discharge state of the target device and the battery pack connected to each battery pack branch according to the magnitude relationship between each battery pack voltage and the limit value of the access voltage range; When the battery pack voltage corresponding to each battery pack branch belongs to the access voltage range corresponding to the bus voltage, the target device connected to each battery pack branch is a relay.

3. The method according to claim 2, characterized in that Determining the charge and discharge status of the target device and the battery pack connected to each battery pack branch according to the magnitude relationship between each battery pack voltage and the limit value of the access voltage range, including: Determine the number of high-voltage battery packs whose battery pack voltage is greater than an upper limit of the access voltage range, the number of low-voltage battery packs whose battery pack voltage is less than a lower limit of the access voltage range, and the number of conventional battery packs whose battery pack voltage is within the access voltage range, respectively, among a plurality of battery packs; The charge and discharge status of the target device and the battery pack connected to each battery pack branch are determined according to the corresponding quantities of the high-voltage battery pack, the low-voltage battery pack and the conventional battery pack.

4. The method according to claim 3, characterized in that The charge and discharge state of the battery pack includes a charge state and a discharge state. The charge and discharge state of the target device and the battery pack connected to each battery pack branch is determined in the following manner: When the number of the high-voltage battery packs is zero, it is determined that the target device of the low-voltage battery pack is a bidirectional DC converter and the corresponding charge and discharge state is a charging state, and it is determined that the target device of the battery pack other than the low-voltage battery pack is a relay and the corresponding charge and discharge state is a discharging state, When the number of the high-voltage battery packs is not zero, the target device of the high-voltage battery pack is determined to be a relay and the corresponding charge and discharge state is a discharge state, and the target devices of other battery packs except the high-voltage battery pack are determined to be bidirectional DC converters and the corresponding charge and discharge state is a charge state.

5. The method according to claim 1, characterized in that The working state of the energy storage converter includes a charge and discharge state, the voltage parameter corresponding to the charge and discharge state includes a single cell voltage of each battery pack, and the reference voltage range corresponding to the single cell voltage refers to the cell voltage range of the battery pack. The target device connected to the energy storage system in each battery pack branch of the energy storage system is determined in the following manner: According to the charge and discharge state of the energy storage converter, the outlier battery pack of the energy storage system is determined by determining the magnitude relationship between the voltage of each single cell of each battery pack and the limit value of the battery cell voltage range of the battery pack in which the outlier battery pack is located; The target device of the battery pack branch where the outlier battery pack is located is determined to be the bidirectional DC converter, and the target devices of other battery packs except the outlier battery pack are determined to be the relay.

6. The method according to claim 5, characterized in that The charge and discharge state includes a charge state and a discharge state, and the outlier battery pack of the energy storage system is determined by: In the charging state of the energy storage converter, a battery pack having at least one battery cell whose single cell voltage is greater than an upper limit of its corresponding battery cell voltage range is determined as the outlier battery pack; In the discharging state of the energy storage converter, a battery pack having at least one battery cell whose single cell voltage is less than a lower limit of its corresponding battery cell voltage range is determined as the outlier battery pack.

7. The method according to claim 5, characterized in that After controlling the target device of each battery pack branch to connect to the energy storage system and controlling the preset device to connect out of the energy storage system, the method further includes: adjusting preset battery pack parameters of the outlier battery pack, wherein the preset battery pack parameters include battery pack current; Wherein, adjusting the preset battery pack parameters of the outlier battery pack includes: reducing the battery pack current of the outlier battery pack.

8. The method according to claim 1, characterized in that The method further comprises: Obtaining the number of faulty battery packs among the multiple battery packs, and calculating the fault ratio of the number of faulty battery packs among the multiple battery packs; Determining a mode for adjusting the working power of the energy storage converter according to a comparison result between the fault ratio and a preset ratio; Based on the adjustment method, the normal battery packs except the faulty battery pack among the plurality of battery packs are controlled to output power.

9. The method according to claim 8, characterized in that The adjustment method for the working power of the energy storage converter is determined by: When the fault ratio is greater than a preset ratio, determining that the adjustment method is to reduce the operating power of the energy storage converter; When the fault ratio is not greater than a preset ratio, the adjustment method is determined to maintain the operating power of the energy storage converter.

10. The method according to claim 9, characterized in that The normal battery packs except the faulty battery pack among the plurality of battery packs are controlled to output power in the following manner: Control the conventional battery pack to output power according to a preset output power to reduce the operating power of the energy storage inverter, or control the conventional battery pack to output power according to the operating power of the energy storage inverter to maintain the operating power of the energy storage inverter.

11. An energy storage system, characterized in that: The energy storage system comprises: Busbar; An energy storage converter connected to the bus; A plurality of battery pack branches, each battery pack branch leads to a busbar connection end for connecting to the busbar, each battery pack branch comprises a battery pack, a bidirectional DC converter and a relay, the bidirectional DC converter and the relay are connected in parallel between the battery pack and the busbar connection end, and the bidirectional DC converter and the relay are not connected to the energy storage system at the same time; A controller configured to execute the method according to any one of claims 1 to 10, Each battery pack further includes a battery management system, and the battery management system of each battery pack sends the battery pack parameters to the controller.

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