Battery connection control method and battery connection control apparatus

Abstract

A battery connection control method and a battery connection control apparatus are provided. The battery connection control method comprises the steps of: determining, on the basis of individual state information of a plurality of battery racks connectable in parallel between power lines, an online SOC indicating the SOC of at least one battery rack in an online state from among the plurality of battery racks, and an offline SOC indicating the SOC of a target battery rack in an offline state; limiting charging / discharging power for each battery rack in the online state if the difference between the online SOC and the offline SOC is less than the threshold SOC; if an elapsed time of the limiting of the charging / discharging power is less than the threshold time, determining an online voltage indicating a voltage of the at least one battery rack in the online state and an offline voltage of the target battery rack; and switching the target battery rack to the online state if the difference between the online voltage and the offline voltage is less than the threshold voltage.

Description

Battery connection control method and battery connection control device

[0001] The present invention relates to a technology for controlling the parallel connection between a plurality of battery racks to prevent inrush current.

[0002] This application is a priority application for Korean Patent Application No. 10-2024-0139376 filed on October 14, 2024, and all contents disclosed in the specification and drawings of said application are incorporated into this application by reference.

[0003] Recently, as the demand for portable electronic products such as laptops, video cameras, and mobile phones has increased rapidly, and the development of electric vehicles, energy storage batteries, robots, and satellites has accelerated, research on high-performance batteries capable of repeated charging and discharging is actively underway.

[0004] Currently commercialized batteries include nickel-cadmium, nickel-hydrogen, nickel-zinc, and lithium batteries. Among these, lithium batteries are gaining attention for their advantages, such as the ability to freely charge and discharge with almost no memory effect compared to nickel-based batteries, a very low self-discharge rate, and high energy density.

[0005] Recently, it has become important to secure the highest possible capacity for stable power management in energy storage systems as well as electric vehicles. Accordingly, a battery bank comprising multiple battery racks installed to be connected in parallel is provided, and a method is being utilized in which one or more of the multiple battery racks are electrically connected between a pair of power lines to match the amount of charging and discharging power required from the outside.

[0006] However, when two or more battery racks with insufficient voltage suppression are connected in parallel, a very large inrush current may flow instantaneously. This inrush current can cause serious damage to the battery rack's protective components (e.g., the switching unit described later).

[0007] The present invention is devised to solve the above-mentioned problems and aims to provide a method and apparatus for controlling so that a battery rack in an offline state can be safely electrically connected in parallel to a battery rack that is already in an online state among a plurality of battery racks.

[0008] Other objects and advantages of the present invention may be understood from the following description and will become more clearly apparent from the embodiments of the present invention. Furthermore, it will be readily apparent that the objects and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims.

[0009] A battery connection control method according to one aspect of the present invention comprises: monitoring individual state information of a plurality of battery racks capable of parallel connection between a pair of power lines; determining, based on the state information, an online SOC representing the SOC of at least one battery rack among the plurality of battery racks that is in an online state and an offline SOC representing the SOC of a target battery rack among the plurality of battery racks that is in an offline state; if the difference between the online SOC and the offline SOC is less than a threshold SOC, executing a limit on the charge / discharge power for each battery rack in an online state; if the elapsed time of the limit on the charge / discharge power is less than a threshold time, determining an online voltage representing the voltage of at least one battery rack in an online state and an offline voltage representing the voltage of the target battery rack; and if the difference between the online voltage and the offline voltage is less than a threshold voltage, switching the target battery rack from an offline state to an online state.

[0010] The battery connection control method described above may further include the step of determining one of the two or more battery racks in an offline state as the target battery rack based on at least one of the identification number, voltage, and SOC of each of the two or more battery racks in an offline state when two or more of the battery racks among the plurality of battery racks are in an offline state.

[0011] If only a single battery rack among the plurality of battery racks is in the online state, the online SOC can be determined to be the same as the SOC of the single battery rack in the online state.

[0012] When two or more of the plurality of battery racks are in the online state, the online SOC can be determined to be equal to the average of the SOCs of the two or more battery racks that are in the online state.

[0013] The battery connection control method described above may further include the step of releasing the limit on charging and discharging power for each battery rack in the online state after the target battery rack is switched from the offline state to the online state.

[0014] The battery connection control method described above may further include a step of reducing the threshold SOC by a certain value if the elapsed time of the limitation of the charge / discharge power is greater than or equal to the threshold time.

[0015] The battery connection control method described above may further include the step of releasing the limitation on charging and discharging power for each battery rack in the online state if the elapsed time of the limitation on charging and discharging power is greater than or equal to the threshold time.

[0016] The battery connection control method described above may further include the step of resetting the threshold SOC to a predetermined reference SOC if the difference between the online voltage and the offline voltage is less than the threshold voltage.

[0017] If the difference between the above online voltage and the above offline voltage is greater than or equal to the above threshold voltage, the limit of the charge / discharge power can be maintained.

[0018] A computer-readable medium according to one embodiment of the present invention can record a program for executing the battery connection control method on a computer.

[0019] A battery connection control device according to another aspect of the present invention comprises: a monitoring unit that monitors individual status information of a plurality of battery racks capable of parallel connection between a pair of power lines; and a controller that, based on the status information, determines an online SOC representing the SOC of at least one battery rack among the plurality of battery racks that is in an online state, and determines an offline SOC representing the SOC of a target battery rack, which is one battery rack among the plurality of battery racks that is in an offline state. The controller is configured to execute a limit on charge / discharge power for each battery rack in an online state if the difference between the online SOC and the offline SOC is less than a threshold SOC. The controller is configured to determine an online voltage representing the voltage of at least one battery rack in an online state and an offline voltage representing the voltage of the target battery rack if the elapsed time of the limit on charge / discharge power is less than a threshold time. The controller is configured to switch the target battery rack from an offline state to an online state if the difference between the online voltage and the offline voltage is less than a threshold voltage.

[0020] The above controller may be configured to release the limit on charge / discharge power for each battery rack in the online state after the target battery rack is switched from the offline state to the online state.

[0021] The above controller may be configured to reduce the threshold SOC by a certain value if the elapsed time of the limitation of the charge / discharge power is longer than the threshold time.

[0022] The above controller may be configured to release the limit on charging and discharging power for each battery rack in the online state if the elapsed time of the limit on charging and discharging power is greater than or equal to the threshold time.

[0023] The above controller may be configured to reset the threshold SOC to a predetermined reference SOC if the difference between the online voltage and the offline voltage is less than the threshold voltage.

[0024] An energy storage system according to another aspect of the present invention includes the battery connection control device.

[0025] According to at least one of the embodiments of the present invention, the risk caused by inrush current that may flow when an offline battery rack is electrically connected in parallel to a battery rack that is already online among a plurality of battery racks can be reduced.

[0026] In addition, according to at least one of the embodiments of the present invention, after a primary connection condition (step S530 of FIG. 5) based on the SOC of an offline battery rack and the SOC of an online battery rack is satisfied, a secondary connection condition (step S560 of FIG. 5) based on the voltage of an offline battery rack and the voltage of an online battery rack is satisfied, thereby enabling safe parallel connection control that takes into account the difference characteristics between the OCV and the CCV.

[0027] In addition, according to at least one of the embodiments of the present invention, even if the charging and discharging power for an online battery rack is limited for a certain period of time or longer, if the voltage difference between an offline battery rack and an online battery rack is not sufficiently reduced, the execution conditions of the charging and discharging power limiting function are strengthened (reduction of 'critical SOC' in step S580), thereby preventing the charging and discharging power limiting function for each online battery rack from being executed more frequently than necessary or the charging and discharging power limiting state from being prolonged.

[0028] The effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description in the claims.

[0029] The following drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the detailed description of the invention provided below; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings.

[0030] FIG. 1 is a schematic diagram showing the configuration of an energy storage system according to the present invention.

[0031] Figure 2 is a diagram schematically showing the coupling relationships between the components of the energy storage system illustrated in Figure 1.

[0032] Figures 3 and 4 are reference drawings used to explain the situation of inrush current generation between multiple battery racks.

[0033] FIG. 5 is a flowchart schematically illustrating a battery connection control method according to the present invention.

[0034] FIG. 6 is a flowchart schematically illustrating an example of a set of routines that may be included in step S520 of FIG. 5.

[0035] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Prior to this, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, and should be interpreted in a meaning and concept consistent with the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0036] Therefore, the embodiments described in this specification and the configurations illustrated in the drawings are merely the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention; thus, it should be understood that various equivalents and modifications that can replace them may exist at the time of filing this application.

[0037] Terms including ordinal numbers, such as first, second, etc., are used for the purpose of distinguishing one of the various components from the rest, and are not used to limit the components by such terms.

[0038] Throughout the specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components. Furthermore, terms such as "<unit>" as used in the specification refer to a unit that performs at least one function or operation and may be implemented in hardware, software, or a combination of hardware and software.

[0039] Additionally, throughout the specification, when it is said that a part is "connected" to another part, this includes not only cases where they are "directly connected," but also cases where they are "indirectly connected" with other components in between.

[0040] FIG. 1 is a schematic diagram showing the configuration of an energy storage system (1) according to the present invention, and FIG. 2 is a schematic diagram showing the coupling relationship between the components of the energy storage system (1) shown in FIG. 1.

[0041] Referring to FIGS. 1 and 2, the energy storage system (1) includes a battery bank (BB), a power conversion system (10), and a battery connection control device (100). m is a natural number greater than or equal to 2.

[0042] The battery bank (BB) comprises a plurality of battery racks (BR1~BR m Includes ). Multiple battery racks (BR1~BR m Each of ) can be connected to a power conversion system (10) via a pair of power lines (P+, P-). In this specification, a plurality of battery racks (BR1~BR mIn explaining the contents common to ), the symbol 'BR' or 'BR i It is decided to assign '. i is a natural number less than or equal to m.

[0043] The power conversion system (10) comprises a plurality of battery racks (BR1~BR m ), is electrically connected between the power system (2) and / or the electric load (3).

[0044] A power conversion system (10) utilizes a DC-AC inverter and / or DC-DC converter equipped therein to form a plurality of battery racks (BR1~BR m ) and power system (2) and / or multiple battery racks (BR1~BR m It is responsible for power transfer between the power grid (2) and the electric load (3). That is, while operating in battery charging mode, the power conversion system (10) converts alternating current power (or other level of direct current power) supplied from the power grid (2) into direct current power and converts a plurality of battery racks (BR1~BR m Can supply to ).

[0045] The power conversion system (10), while operating in battery discharge mode, has a plurality of battery racks (BR1~BR m The DC power input by at least one discharge of ) can be converted into AC power (or DC power of a different level) and supplied to the power system (2) and / or electric load (3).

[0046] The battery connection control device (100) can receive power amount information from the power conversion system (10). The power amount information may represent the charging power or discharging power requested from the power system (2) and / or the electric load (3).

[0047] The battery connection control device (100) comprises a plurality of battery racks (BR1~BR m) Acquire state information indicating each state and, based on the acquired state information, transmit a charge request signal, a discharge request signal, and / or a standby request signal to the power conversion system (10). When the power conversion system (10) receives a charge request signal, it may operate in a battery charging mode. When the power conversion system (10) receives a discharge request signal, it may operate in a battery discharging mode.

[0048] The charging request signal is a plurality of battery racks (BR1~BR m It is a signal requesting that DC power be supplied to at least one of ). The discharge request signal is a plurality of battery racks (BR1~BR m It is a signal requesting that DC power be extracted from at least one of the following. The standby request signal is a signal requesting that both the charging operation and the discharging operation be stopped.

[0049] Battery Rack (BR i ) is a group of batteries (BG) connected in series with each other. i ) and switching unit (SW i Includes ).

[0050] Battery Group (BG) i ) includes at least one battery cell (BC). Battery group (BG i When a plurality of battery cells (BC) are included in the battery cell, these plurality of battery cells (BC) may be interconnected in series, parallel, or a combination of series and parallel. In this specification, a battery cell (BC) refers to a basic unit of a battery capable of independent charging and discharging, and is not particularly limited as long as it is rechargeable, such as a lithium-ion cell, for example.

[0051] Switching unit (SW) i ) is the battery group (BG iThe current path between the ) and the power conversion system (10) is not particularly limited as long as it is switchable. For example, a semiconductor switch such as a MOSFET, a mechanical switch such as a relay, etc., can be a switching unit (SW i It can be used as ).

[0052] Multiple switching units (SW1~SW m Depending on the individual on / off status of ), multiple battery racks (BR1~BR m Any two or more of the following can be connected in parallel between a pair of power lines (P+, P-).

[0053] Switching unit (SW) i When ) is turned on, the battery group (BG i ) is electrically connected between a pair of power lines, and this state can be referred to as the 'online state'. Therefore, multiple battery racks (BR1~BR m The fact that two or more battery racks (e.g., BR1, BR2, BR3) among the battery groups are online may mean that those two or more battery racks (e.g., BR1, BR2, BR3) are electrically connected in parallel with each other. Battery Group (BG i While ) is online, the battery group (BG i Both charging and discharging of ) are possible. Of course, the battery group (BG i Even if ) is online, if the operation of the power conversion system (10) is stopped, the battery group (BG i Both charging and discharging of ) can be stopped.

[0054] Conversely, the switching unit (SW i When ) is turned off, the battery group (BG i ) is electrically disconnected from a pair of power lines, and this state can be referred to as 'offline state'. Battery Group (BG iWhile ) is in an offline state, even if the power conversion system (10) operates in a charging mode or a discharging mode, the battery group (BG i Charging and discharging of ) is not possible.

[0055] In this specification, a battery rack that is online may simply be referred to as an "online rack," and a battery rack that is offline may simply be referred to as an "offline rack."

[0056] The battery connection control device (100) comprises a plurality of battery racks (BR1~BR m It can be configured to execute control function(s) to prevent the occurrence of inrush current that may flow when at least two of them are connected in parallel.

[0057] The battery connection control device (100) includes an information monitoring unit (110) and a controller (120).

[0058] The information monitoring unit (110) comprises a plurality of sensing units (SU1~SU m It may include a plurality of sensing units (SU1~SU m ) is a plurality of battery racks (BR1~BR m It is provided for monitoring the individual status of ).

[0059] Multiple sensing units (SU1~SU m Each includes a voltage measuring circuit (VS) and a current sensor (CS).

[0060] The voltage measurement circuit (VS) is a battery group (BG i Connected in parallel to the battery group (BG) i It measures the voltage across the terminals of ) (which may be referred to as 'rack voltage' or 'group voltage'). In addition, the voltage measurement circuit (VS) measures the battery group (BG i The voltage of each battery cell (BC) of ) can be measured (which can be called 'cell voltage').

[0061] The current sensor (CS) is a battery group (BG i) and switching unit (SW i Installed on the rack line connecting ), the battery rack (BR i Measures the current flowing through the ). Sensing unit (SU i ) generates a sensing signal representing the measured voltage and the measured current. The sensing signal may refer to a pair of synchronously detected voltage and current values.

[0062] The controller (120) comprises a plurality of switching units (SW1~SW m ), information monitoring unit (110), and power conversion system (10) can be individually and operably coupled. Being operably coupled means that the two components are connected by wire and / or wirelessly so that signals can be transmitted and received in one direction or both directions.

[0063] The controller (120) can be implemented in hardware using at least one of ASICs (application specific integrated circuits), DSPs (digital signal processors), DSPDs (digital signal processing devices), PLDs (programmable logic devices), FPGAs (field programmable gate arrays), microprocessors, and other electrical units for performing functions.

[0064] The controller (120) may have a memory device. The memory device may include at least one type of storage medium among flash memory type, hard disk type, SSD type (Solid State Disk type), SSD type (Silicon Disk Drive type), multimedia card micro type, RAM (random access memory; RAM), SRAM (static random access memory), ROM (read-only memory; ROM), EEPROM (electrically erasable programmable read-only memory), and PROM (programmable read-only memory). The memory device may store data and programs required for computational operations by the controller (120). The memory device may store data representing the result of computational operations by the controller (120).

[0065] The controller (120) can collect status information from the information monitoring unit (110) periodically or non-periodically. Based on the status information, the controller (120) can collect a plurality of battery racks (BR1~BR m The individual state of charge (SOC) can be determined. SOC is the ratio of remaining capacity to maximum capacity and is typically expressed in the range of 0 to 100%. Remaining capacity represents the amount of charge currently stored in the battery rack (BR).

[0066] FIGS. 3 and 4 show a plurality of battery racks (BR1~BR m This is a diagram referenced to explain the situation of inrush current generation between ).

[0067] Figure 3 shows a battery rack (BR iThis exemplifies the relationship between OCV (Open Circuit Voltage) and CCV (Closed Circuit Voltage) during constant current charging.

[0068] Referring to FIG. 3, the curve (310) is a battery rack (BR i It represents the relationship between the SOC and OCV of the battery rack (BR), that is, the change in OCV according to the change in SOC. The curve (320) represents the battery rack (BR i It shows the relationship between SOC and CCV, that is, the change in OCC according to the change in SOC. The curve (330) shows the change in the voltage difference between OCV and CCV according to the change in SOC.

[0069] As can be seen through curves (310) and (320), as SOC increases, OCV and CCV gradually increase.

[0070] In addition, the voltage difference between OCV and CCV occurs according to Ohm's law, and the larger the charging current, the larger the voltage difference between OCV and CCV.

[0071] Figure 4 shows a battery rack (BR i It exemplifies the equivalent circuit model of ).

[0072] Referring to FIG. 4, the equivalent circuit model (400) includes a voltage source (410) and an ohm resistor (R ohm Includes ) and RC pair (420).

[0073] The voltage source (410) is a battery group (BG) in an electrochemically stabilized state. i It simulates the OCV of ). The OCV output by the voltage source (410) is a battery group (BG i It has a non-linear functional relationship with the SOC of ) (curve 310 in Fig. 3).

[0074] Ohm resistance (R ohm ) is, battery rack (BR i It is associated with the IR drop (V1) of the battery group (BG). The IR drop (V1) is associated with the battery group (BG iDuring charging and discharging of the battery group (BG) i It refers to the instantaneous change in voltage. Ohm resistance (R ohm ) is, battery rack (BR i The internal resistance of each battery cell (BC) of ) as well as the battery rack (BR i It is a parameter that reflects even the resistance of the physical connection means (e.g., wires, busbars, etc.) of ), and can be verified through preliminary experiments, etc.

[0075] RC pair (420) is a battery rack (BR i Outputting an overpotential (V2) induced by the electric double layer, etc., of each battery cell (BC), wherein resistors (R) connected in parallel are used. P ) and capacitor(C P It includes ). The overpotential (V2) may also be referred to as the 'polarization voltage'.

[0076] The time constant of the RC pair (420) is the resistance (R P The resistance value of ) and the capacitor (C P It is the product of the capacitances, and can be predetermined for various charge states and temperatures through prior experiments. V ecm Silver represents the output voltage of the equivalent circuit model (400), and the battery rack (BR i Corresponds to the voltage of ). V ecm Silver, OCV of the voltage source (410), ohmic resistance (R ohm It can be equal to the sum of V1 of ) and V2 of RC pair (420).

[0077] Current (I B When the ) is cut off, V1 immediately becomes 0 [V], while V2 changes gradually. Therefore, the battery rack (BR i Even if ) switches from online to offline, V must pass for a certain amount of time to pass. ecm The voltage difference between and V1 can be sufficiently reduced.

[0078] Battery Rack (BR i If ) is offline, the battery rack (BR i The resistance value of ) is the ohm resistance (R ohm It can be configured identically to ). Battery rack (BR i If ) is online, the battery rack (BR i The resistance value of ) is the ohm resistance (R ohm ) and resistance (R P It can be set to be equal to the sum of ).

[0079] Synthesizing the above description with reference to FIGS. 3 and 4, a plurality of battery racks (BR1~BR m A person skilled in the art will easily understand that even if the SOC of the offline battery rack and the online battery rack among ) are the same, the voltage difference between these two battery racks can be very large. Furthermore, multiple battery racks (BR1~BR m Even if two battery racks are offline, if the time difference between each of the two battery racks remaining offline is large, the voltage difference between the two battery racks may be very large.

[0080] Battery Rack (BR i When ) transitions from offline to online, other battery racks already online (e.g., BR m The inrush current caused by the voltage difference with the switching unit (SW) i If it is greater than the rated current of the switching unit (SW i ) as well as the Battery Group (BG i Even ) may suffer overcurrent damage. In this case, the battery rack (BR i A problem may also arise in which the available capacity of the energy storage system (1) is reduced by the electrical capacity of ). Therefore, a plurality of battery racks (BR1~BR m A measure is needed to prevent the risk of inrush current generation when at least two of the ) are connected in parallel.

[0081] FIG. 5 is a flowchart schematically illustrating a battery connection control method according to the present invention. The method of FIG. 5 can be executed by the battery connection control device (100) illustrated in FIG. 2. The method of FIG. 5 comprises a plurality of battery racks (BR1~BR m It can be executed on the condition that at least one of the battery racks is offline and the remaining battery racks are online.

[0082] Referring to FIG. 5, in step S510, the information monitoring unit (110) comprises a plurality of battery racks (BR1~BR m Monitors individual status information of ).

[0083] In step S520, the controller (120) determines the offline SOC and online SOC based on the status information. The offline SOC is a plurality of battery racks (BR1~BR m It can represent the SOC of the target battery rack, which is any one of the battery racks in an offline state. The online SOC is the battery rack (BR1~BR m It can indicate the SOC of at least one battery rack that is online.

[0084] In step S530, the controller (120) determines whether the difference (absolute value) between the offline SOC and the online SOC is less than the threshold SOC. If the value of step S530 is "yes," the process can proceed to step S540. If the value of step S530 is "no," the method according to FIG. 5 can be terminated.

[0085] In step S540, the controller (120) implements a limit on the charge / discharge power for each battery rack that is online. In one embodiment, the limit on the charge / discharge power may mean that the controller (120) transmits a request to stop operation to the power conversion system (10). By step S540, the voltage (rack voltage) of each battery rack that is online may change toward the OCV. The elapsed time of the limit on the charge / discharge power may be counted in real time by the controller (120) until the limit on the charge / discharge power is released.

[0086] In step S550, the controller (120) can determine whether the elapsed time of the charge / discharge power limitation is less than a threshold time (e.g., 3 minutes). The threshold time may be predetermined based on the time constant of the RC pair (420). If the value of step S550 is "Yes," the process can proceed to step S560. If the value of step S550 is "No," it corresponds to a situation where the charge / discharge power is limited for longer than the threshold time, and one of the causes of this may be that the threshold SOC is excessively high. If the value of step S550 is "No," the process can proceed to step S580.

[0087] In step S560, the controller (120) can determine whether the difference between the online voltage and the offline voltage is less than a threshold voltage. The online voltage represents the voltage of at least one battery rack associated with the online SOC. The offline voltage represents the voltage of the target battery rack. The online voltage and the offline voltage may be determined in step S520.

[0088] The threshold voltage (e.g., 7 [V]) is the switching unit (SW i The rated current of ) and the battery rack (BR i The resistance value of ) (e.g., R ohm It may be predetermined by considering ). For example, a switching unit (SW iThe rated current of ) = 200 [A], and R ohm In the case where = 0.06[Ω], the voltage difference between the online voltage and the offline voltage is 12 [V] (= rated current × R ohm If it is ) or less, the inrush current does not exceed the rated current. However, the battery rack (BR i Considering the variation in the resistance value of ) and the voltage measurement error of the battery pack, the threshold voltage may be set to be less than 12 [V].

[0089] A value of "Yes" in step S560 corresponds to a situation where the offline voltage is sufficiently close to the online voltage, so that the risk of inrush current generation is very low even when the target battery rack is switched from an offline state to an online state. If the value of step S560 is "Yes", the process can proceed to step S570. If the value of step S560 is "No", the process can return to step S550.

[0090] In step S570, the controller (120) switches the target battery rack from an offline state to an online state. For example, a battery rack (BR i If ) is the target battery rack, the controller (120) is a switching unit (SW i ) can be turned on, and accordingly, the battery rack (BR i ) becomes online.

[0091] When step S570 is executed, the target battery rack is charged or discharged according to the voltage difference (less than the reference voltage) between at least one battery rack that is already online prior to step S570 and the target battery rack newly brought online by step S570, thereby safely balancing the SOC among all battery racks that are online.

[0092] In step S580, the controller (120) updates the threshold SOC by decreasing the threshold SOC by a certain value (ΔSOC) (e.g., 0.5%). Step S580 may be a procedure intended to reduce the frequency in which the value of step S560 becomes "No" even though the value of step S530 is "Yes". After the completion of step S580, the process may proceed to step S582.

[0093] In step S582, the controller (120) can determine whether the threshold SOC is less than a predetermined lower limit SOC (e.g., 1%). If the threshold SOC is less than the lower limit SOC, the likelihood that the value of step S530 will be "yes" becomes too low, and the target battery rack may have little chance of transitioning from an offline state to an online state. If the value of step S582 is "yes," the process can proceed to step S584. If the value of step S582 is "no," the process can proceed to step S590.

[0094] In step S584, the controller (120) can reset the threshold SOC to a predetermined reference SOC (e.g., 3%). Specifically, the threshold SOC, which has become smaller than the reference SOC by the aforementioned step S580, can be restored to be equal to the reference SOC by step S584. After the completion of step S584, the process can proceed to step S590.

[0095] In step S590, the controller (120) releases the limit on the charge / discharge power for each battery rack that is online. In one embodiment, releasing the limit on the charge / discharge power may mean that the controller (120) sends a request to resume operation to the power conversion system (10). As step S590 is executed, the charge / discharge of each battery rack that is online, which was temporarily paused by step S540, may be resumed.

[0096] FIG. 6 is a flowchart schematically illustrating an example of a set of routines that may be included in step S520 of FIG. 5. The method of FIG. 6 may be executed after step S510 of FIG. 5.

[0097] Referring to FIG. 6, in step S610, the controller (120), based on state information, has a plurality of battery racks (BR1~BR m The online SOC is determined based on the SOC of at least one battery rack that is online among the above.

[0098] Multiple battery racks (BR1~BR m If only one of the battery racks is online, the controller (120) can determine the SOC of the battery rack that is online as the online SOC.

[0099] Multiple battery racks (BR1~BR m If two or more of the battery racks are online, the controller (120) can determine the average of the SOCs of the two or more battery racks that are online as the online SOC.

[0100] In step S620, the controller (120) comprises a plurality of battery racks (BR1~BR m Select one of the battery racks that is offline as the target battery rack.

[0101] Multiple battery racks (BR1~BR m If only one of the battery racks is offline, the controller (120) can select the offline battery rack as the target battery rack.

[0102] Multiple battery racks (BR1~BR m If two or more of the battery racks are offline, the controller (120) can select one of the two or more offline battery racks as the target battery rack based on the identification number, SOC, or voltage of each of the two or more offline battery racks.

[0103] For example, the target battery rack may be the battery rack having the highest priority identification number among two or more battery racks. As another example, the target battery rack may be the battery rack having the smallest SOC with the smallest voltage difference from the online SOC among two or more battery racks. As yet another example, the target battery rack may be the battery rack having the smallest voltage with the smallest voltage difference from the online voltage among two or more battery racks.

[0104] In step S630, the controller (120) determines the SOC of the target battery rack as an offline SOC. After step S630 is executed, step S530 of FIG. 5 may proceed.

[0105] Another embodiment of the present invention may provide a computer-readable recording medium having a program recorded thereon for executing the various embodiments described above on a computer.

[0106] A program may be implemented as hardware components, software components, and / or a combination of hardware and software components. A program may be executed by any system capable of executing computer-readable instructions.

[0107] Software may include computer programs, code, instructions, or a combination thereof, and may configure a processing unit to operate as desired or command the processing unit independently or collectively.

[0108] Software can be implemented as a computer program containing instructions stored on a computer-readable storage medium. Examples of computer-readable storage media include magnetic storage media (e.g., ROM (read-only memory), RAM (random-access memory), floppy disks, hard disks, etc.) and optical reading media (e.g., CD-ROMs, DVDs (Digital Versatile Discs)). Computer-readable storage media can be distributed across networked computer systems, allowing computer-readable code to be stored and executed in a distributed manner. The storage medium is readable by a computer, stored in memory, and can be executed by a processor.

[0109] Computer-readable recording media may be provided in the form of non-transitory recording media. Here, 'non-transitory storage media' simply means that it is a tangible device and does not contain a signal (e.g., electromagnetic waves), and the term does not distinguish between cases where data is stored semi-permanently and cases where it is stored temporarily. For example, 'non-transitory storage media' may include a buffer in which data is stored temporarily.

[0110] In addition, the program may be provided by being included in a computer program product. A computer program product may be traded between a seller and a buyer as a product.

[0111] A computer program product may include a software program or a computer-readable recording medium on which the software program is stored. For example, a computer program product may include a product in the form of a software program that is distributed electronically through a manufacturer of an electronic device or an electronic market (e.g., a downloadable application). For electronic distribution, at least a portion of the software program may be stored on a recording medium or temporarily created. In this case, the recording medium may be a server of the manufacturer of the electronic device, a server of the electronic market, or a recording medium of a relay server that temporarily stores the software program.

[0112] The controller (120) may include a processor and memory. When a program stored in memory is executed by the processor, the program is executed by the processor in the following steps, namely, a plurality of battery racks (BR1~BR) that can be connected in parallel between a pair of power lines. m A step of monitoring individual status information of ); based on the status information, a plurality of battery racks (BR1~BR m Online SOC representing the SOC of at least one battery rack in an online state among ) and multiple battery racks (BR1~BR mA step of determining an offline SOC representing the SOC of a target battery rack that is one of the battery racks in an offline state; a step of limiting the charge / discharge power for each battery rack in an online state if the difference between the online SOC and the offline SOC is less than a threshold SOC; a step of determining an online voltage representing the voltage of at least one battery rack in an online state and an offline voltage representing the voltage of a target battery rack if the elapsed time of the limiting of the charge / discharge power is less than a threshold time; and a step of switching the target battery rack from an offline state to an online state if the difference between the online voltage and the offline voltage is less than a threshold voltage.

[0113] The embodiments of the present invention described above are not limited to implementation through devices and methods, but may also be implemented through a program that realizes a function corresponding to the configuration of the embodiments of the present invention or a recording medium on which such a program is recorded. Such implementation can be easily achieved by a person skilled in the art to which the present invention pertains, based on the description of the embodiments described above.

[0114] Although the present invention has been described above by limited embodiments and drawings, the present invention is not limited thereto, and it is obvious that various modifications and variations are possible within the scope of the technical spirit of the present invention and the equivalent scope of the claims described below by those skilled in the art to which the present invention belongs.

[0115] Furthermore, since the present invention described above allows for various substitutions, modifications, and changes within the scope of the technical concept of the present invention to those skilled in the art without departing from the technical spirit of the present invention, it is not limited by the aforementioned embodiments and attached drawings, but rather all or part of each embodiment may be selectively combined to allow for various modifications.

[0116]

Claims

1. A step of monitoring individual status information of multiple battery racks capable of parallel connection between a pair of power lines; Based on the above state information, a step of determining an online SOC representing the SOC of at least one battery rack that is in an online state among the plurality of battery racks, and an offline SOC representing the SOC of a target battery rack that is one battery rack that is in an offline state among the plurality of battery racks; If the difference between the online SOC and the offline SOC is less than the threshold SOC, a step of limiting the charge / discharge power for each battery rack in the online state; If the elapsed time of the limitation of the charge / discharge power is less than the threshold time, the method comprises the step of determining an online voltage representing the voltage of at least one battery rack in the online state and an offline voltage representing the voltage of the target battery rack; and If the difference between the online voltage and the offline voltage is less than a threshold voltage, the step of switching the target battery rack from the offline state to the online state; A battery connection control method including 2. In Paragraph 1, When two or more of the plurality of battery racks are in an offline state, a step of determining one of the two or more battery racks in an offline state as the target battery rack based on at least one of the identification number, voltage, and SOC of each of the two or more battery racks in an offline state; A battery connection control method further comprising 3. In Paragraph 1, When only a single battery rack among the plurality of battery racks is in the online state, the online SOC is determined to be the same as the SOC of the single battery rack in the online state, and A battery connection control method in which, when two or more of the plurality of battery racks are in an online state, the online SOC is determined to be equal to the average of the SOCs of the two or more battery racks in an online state.

4. In Paragraph 1, A step of releasing the limit on charging and discharging power for each battery rack in the online state after the target battery rack is switched from the offline state to the online state; A battery connection control method further comprising 5. In Paragraph 1, If the elapsed time of the limitation of the above charge / discharge power is longer than the above threshold time, a step of reducing the above threshold SOC by a certain value; A battery connection control method further comprising 6. In Paragraph 1, If the elapsed time of the limitation on the charging and discharging power is greater than or equal to the threshold time, a step of releasing the limitation on the charging and discharging power for each battery rack in the online state; A battery connection control method further comprising 7. In Paragraph 1, If the difference between the online voltage and the offline voltage is less than the threshold voltage, a step of resetting the threshold SOC to a predetermined reference SOC; A battery connection control method further comprising 8. In Paragraph 1, A battery connection control method in which, if the difference between the online voltage and the offline voltage is greater than or equal to the threshold voltage, the limit of the charge / discharge power is maintained.

9. A computer-readable medium storing a program for executing the method of any one of paragraphs 1 through 8 on a computer.

10. A monitoring unit for monitoring individual status information of a plurality of battery racks capable of parallel connection between a pair of power lines; and Based on the above state information, the controller determines an online SOC representing the SOC of at least one battery rack that is online among the plurality of battery racks, and determines an offline SOC representing the SOC of a target battery rack that is offline among the plurality of battery racks. The above controller is, If the difference between the above online SOC and the above offline SOC is less than the threshold SOC, limiting the charge / discharge power for each battery rack in the online state is executed, and If the elapsed time of the limitation of the above charge / discharge power is less than the critical time, an online voltage representing the voltage of at least one battery rack in the online state and an offline voltage representing the voltage of the target battery rack are determined, and A battery connection control device that switches the target battery rack from the offline state to the online state when the difference between the online voltage and the offline voltage is less than a threshold voltage.

11. In Paragraph 10, The above controller is, A battery connection control device that releases the limit on charging and discharging power for each battery rack in the online state after the target battery rack is switched from the offline state to the online state.

12. In Paragraph 10, The above controller is, A battery connection control device that reduces the threshold SOC by a certain value if the elapsed time of the limitation of the above-mentioned charge / discharge power is greater than or equal to the above-mentioned threshold time.

13. In Paragraph 10, The above controller is, A battery connection control device that releases the limitation on charging and discharging power for each battery rack in the online state if the elapsed time of the limitation on charging and discharging power is greater than or equal to the threshold time.

14. In Paragraph 10, The above controller is, A battery connection control device that resets the threshold SOC to a predetermined reference SOC when the difference between the online voltage and the offline voltage is less than the threshold voltage.

15. An energy storage system comprising a battery connection control device according to any one of paragraphs 10 to 14.

Images