Apparatus and method for controlling battery rack

Abstract

The present invention relates to a battery rack control device characterized by comprising: a battery rack in which a plurality of battery modules are connected in series and parallel; a data collection unit for collecting operation data of a plurality of battery modules; and a processor for determining the cumulative degradation degree of each of the plurality of battery modules based on the operation data, determining the relative degradation degree of each of the battery modules based on the cumulative degradation degree of each of the battery modules, and controlling the current of the plurality of battery modules based on the relative degradation degree of each of the battery modules.

Description

Technology Field

[0001] The present invention relates to a battery rack control device and method, and more specifically, to a device and method for controlling the current of a plurality of battery modules by detecting a deviation in the degree of degradation between battery modules. Background Technology

[0003] Recently, as the adoption of renewable energy expands and the demand for power grid stability increases, interest in Energy Storage Systems (ESS), which can store large amounts of power and supply it when needed, is growing. Energy storage systems are being utilized for various purposes, such as stabilizing the output of renewable energy sources with high output variability, like solar and wind power, or performing peak shaving functions, which store power during periods of low demand and supply the stored power during periods of high demand.

[0004] Such an energy storage system may generally be configured to include a battery rack that stores power, a power conversion system (PCS) that converts direct current power stored in the battery rack into alternating current power or performs the reverse conversion, and an energy management system (EMS) that manages the overall operation of the system.

[0005] Meanwhile, as battery modules included in a battery rack undergo repeated charging and discharging, degradation phenomena may inevitably occur in which internal resistance increases and rechargeable capacity decreases due to various electrochemical reactions such as structural deformation of the internal active material, growth of the solid electrolyte interphase (SEI) layer on the electrode surface, irreversible consumption of lithium ions, and decomposition of the electrolyte.

[0006] Conventionally, a Battery Management System (BMS) has been utilized to manage the degradation of such battery modules. Conventional battery management systems measure the voltage, current, and temperature of multiple battery modules or battery cells contained in a battery rack in real time, and perform a protection function by disconnecting the corresponding battery module or battery cell from the circuit when abnormal conditions such as overcharging, over-discharging, and overheating are detected based on the measured values.

[0007] However, conventional battery management systems primarily focus on short-term control to resolve voltage or charge state deviations within a single charge-discharge cycle, and thus have limitations in effectively managing the degradation deviations accumulated between multiple battery modules during the long-term operation of the battery rack. Prior art literature

[0009] (Patent Document 0001) US 2025-0372812 A1(Patent Document 0002) US 2025-0309443 A1(Patent Document 0003) KR 10-2024-0160963 A(Patent Document 0004) KR 10-2024-0049383 A

[0010] Zhao, H., Wu, Q., Hu, S., et al.: 'Review of energy storage system for wind power integration support', Appl. Energy, 2015, 137, pp. 545-553Salee, S., Wirasanti, P.: 'Optimal sitting and sizing of battery energy storage systems for grid-supporting in electrical distribution network'. 2018 Int. ECTI Northern Section Conf. on Electrical, Electronics, Computer and Telecommunications Engineering (ECTI-NCON), Malang, Indonesia, 10-12 Nov. 2018, pp. 100-105 The problem to be solved

[0011] The purpose of the present invention is to provide a battery rack control device and method capable of reducing degradation deviations among multiple battery modules and extending the lifespan of the entire battery rack by determining the cumulative degradation and relative degradation of each battery module based on operation data of multiple battery modules included in the battery rack, and actively redistributing the current of each battery module based on the determined relative degradation. means of solving the problem

[0013] A battery rack control device according to some embodiment of the present invention comprises: a battery rack in which a plurality of battery modules are connected in series and parallel; a data collection unit for collecting operation data of the plurality of battery modules; and a processor for determining the cumulative degradation degree of each of the plurality of battery modules based on the operation data, determining the relative degradation degree of each of the battery modules based on the cumulative degradation degree of each of the battery modules, and controlling the current of the plurality of battery modules based on the relative degradation degree of each of the battery modules.

[0014] In the present invention, the operation data is characterized by including the voltage, temperature, number of charge / discharge cycles, and operating time of each battery module.

[0015] In the present invention, the processor determines the cumulative charge / discharge amount of each battery module based on the voltage of each battery module and the current of each battery module, and determines the cumulative degradation degree of each battery module based on the cumulative charge / discharge amount, the temperature, the number of charge / discharge cycles, and the operating time.

[0016] In the present invention, the processor determines the cumulative degradation of a battery module by the sum of a value obtained by multiplying the cumulative charge / discharge amount of the battery module by a first weight, a value obtained by multiplying the temperature of the battery module by a second weight, a value obtained by multiplying the number of charge / discharge cycles of the battery module by a third weight, and a value obtained by multiplying the operating time of the battery module by a fourth weight, wherein the first weight is the largest among the first weight, the second weight, the third weight, and the fourth weight.

[0017] In the present invention, the processor is characterized by determining the cumulative degradation of each battery module by further considering the weighting of each battery module according to the operating time period.

[0018] In the present invention, the processor is characterized by determining the cumulative degradation degree of each battery module by further considering the positional weight of each battery module.

[0019] In the present invention, the processor is characterized by determining the relative degradation of each battery module by dividing the value obtained by subtracting the average value of the cumulative degradation of each battery module from the cumulative degradation of each battery module by the average value.

[0020] The present invention further comprises a plurality of first switches for controlling the current between parallel-connected battery modules among the plurality of battery modules; and the processor controls the plurality of first switches to reduce the current of a battery module whose relative degradation is greater than or equal to a preset value.

[0021] In the present invention, the processor is characterized by opening a first switch connected to the battery module when the relative degradation degree of the battery module is greater than or equal to a cutoff threshold.

[0022] The present invention further comprises a plurality of second switches for controlling the current of a plurality of strings through which the current of the input terminal of the battery rack is branched and flows; and the processor is characterized by controlling the plurality of second switches to reduce the current of the string connected to the single second switch when the relative degradation degree of a set number or more of battery modules among the battery modules whose current is controlled by a single second switch is greater than or equal to a preset value.

[0023] In the present invention, each of the first switch and the second switch comprises a semiconductor switch and a mechanical switch, and the processor determines whether the semiconductor switch is faulty and opens the mechanical switch of the first switch or the second switch corresponding to the semiconductor switch determined to be faulty.

[0024] A battery rack control method according to some embodiments of the present invention comprises: a step in which a processor acquires operation data of a plurality of battery modules; a step in which the processor determines the cumulative degradation degree of each battery module based on the operation data; a step in which the processor determines the relative degradation degree of each battery module based on the cumulative degradation degree of each battery module; and a step in which the processor controls the current of the plurality of battery modules based on the relative degradation degree of each battery module.

[0025] In the present invention, the operation data is characterized by including the voltage, temperature, number of charge / discharge cycles, and operating time of each battery module.

[0026] The present invention is characterized in that, in the step of determining the cumulative degradation degree, the processor determines the cumulative charge / discharge amount of each battery module based on the voltage of each battery module and the current of each battery module, and determines the cumulative degradation degree of each battery module based on the cumulative charge / discharge amount, the temperature, the number of charge / discharge cycles, and the operating time.

[0027] The present invention is characterized in that, in the step of determining the cumulative degradation degree, the processor determines the cumulative degradation degree of the battery module by the sum of the value obtained by multiplying the cumulative charge / discharge amount of the battery module by a first weight, the value obtained by multiplying the temperature of the battery module by a second weight, the value obtained by multiplying the number of charge / discharge cycles of the battery module by a third weight, and the value obtained by multiplying the operating time of the battery module by a fourth weight, wherein the first weight is the largest among the first weight, the second weight, the third weight, and the fourth weight.

[0028] The present invention is characterized by determining the cumulative degradation of each battery module by further considering the weighting of each battery module's operating time period in the step of determining the cumulative degradation.

[0029] The present invention is characterized by determining the cumulative degradation of each battery module by further considering the positional weight of each battery module in the step of determining the cumulative degradation.

[0030] The present invention is characterized in that, in the step of determining the relative degradation degree, the processor determines the relative degradation degree of each battery module by dividing the value obtained by subtracting the average value of the cumulative degradation degree of each battery module from the cumulative degradation degree of each battery module by the average value.

[0031] The present invention is characterized in that, in the step of controlling the current of each of the battery modules, the processor controls a plurality of first switches that regulate the current between parallel-connected battery modules among the plurality of battery modules to reduce the current of a battery module whose relative degradation degree is greater than or equal to a preset value.

[0032] The present invention is characterized in that, in the step of controlling the current of each of the battery modules, the processor opens a first switch connected to the battery module to cut off the current of the battery module when the relative degradation degree of the battery module is greater than or equal to a cutoff threshold.

[0033] The present invention is characterized in that, in the step of controlling the current of each of the battery modules, the processor controls the plurality of second switches to reduce the current of the string connected to the single second switch when the relative degradation degree of more than a set number of battery modules among the battery modules whose current is controlled by one of the plurality of second switches that regulate the current of the plurality of strings through which the current of the input terminal of the battery rack is branched is greater than or equal to a preset value.

[0034] In the present invention, each first switch and second switch comprises a semiconductor switch and a mechanical switch, and in the step of controlling the current of each battery module, the processor determines whether the semiconductor switch is faulty and opens the mechanical switch corresponding to the semiconductor switch determined to be faulty. Effects of the invention

[0036] According to the present invention, by controlling the current of each battery module based on the cumulative degradation and relative degradation of a plurality of battery modules, the degradation variation between battery modules can be reduced and the lifespan of the entire battery rack can be extended.

[0037] According to the present invention, by reducing the current of a battery module whose relative degradation is greater than a preset value, the phenomenon of current and thermal stress being concentrated in a specific battery module can be prevented, and thereby the operational stability of the battery rack can be improved.

[0038] According to the present invention, by calculating the cumulative degradation degree by comprehensively reflecting the cumulative charge / discharge amount, temperature, number of charge / discharge cycles, and operating time of a battery module, it is possible to perform a quantitative and accurate degradation evaluation that considers both cycle degradation and calendar degradation.

[0039] According to the present invention, by providing a first switch for controlling the current between parallel-connected battery modules and a second switch for controlling the current of a plurality of strings, current control at the battery module level and current redistribution at the string level can be performed in stages.

[0040] The effects obtainable from the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art to which the present invention belongs from the description below. Brief explanation of the drawing

[0042] FIG. 1 is an exemplary diagram showing a battery rack according to some embodiment of the present invention. FIG. 2 is a block diagram of a battery rack control device according to some embodiment of the present invention. FIG. 3 is an illustrative diagram for explaining a current control method by a first switch according to some embodiment of the present invention. FIG. 4 is an illustrative diagram for explaining a current control method by a second switch according to some embodiment of the present invention. FIG. 5 is an illustrative diagram for explaining a current control method by a first switch and a second switch according to some embodiments of the present invention. FIG. 6 is a flowchart of a battery rack control method according to some embodiments of the present invention. FIG. 7 is a flowchart of a battery rack control method according to some embodiments of the present invention. Specific details for implementing the invention

[0043] Preferred embodiments of the present invention will be described in detail below 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. Instead, based on the principle that the inventor may appropriately define the concepts of terms to best describe his invention, they should be interpreted in a meaning and concept consistent with the technical spirit of the present invention. Therefore, it should be understood that the embodiments described in this specification and the configurations illustrated in the drawings are merely some of the most preferred embodiments of the present invention and do not represent all of the technical spirit of the present invention; thus, various equivalents and modifications that can replace them may exist at the time of filing this application. Furthermore, as used in this specification, "comprise" or "include" and / or "comprising" or "including" specify the presence of the mentioned features, numbers, steps, actions, parts, elements, and / or groups thereof, and do not exclude the presence or addition of one or more other features, numbers, actions, parts, elements, and / or groups. In addition, when describing embodiments of the present invention, "may" or "may be" may include "one or more embodiments of the present invention."

[0044] Hereinafter, embodiments of the present invention will be described with reference to the attached drawings.

[0045] FIG. 1 is an exemplary diagram showing a battery rack according to some embodiment of the present invention.

[0046] Referring to FIG. 1, a battery rack (10) according to some embodiment of the present invention may be configured such that a plurality of battery modules are connected in series and in parallel.

[0047] Specifically, the battery rack (10) is connected between the positive terminal (+) and the negative terminal (-) of the DC bus, and a plurality of battery modules can be arranged in a combined form of series connection and parallel connection to meet the required output voltage and output capacity.

[0048] FIG. 1 illustrates an exemplary case in which a battery rack (10) includes eight battery modules (battery module 1 to battery module 8), but this is merely an example to aid in understanding the present invention, and the number of battery modules, the number of series connections, and the number of parallel connections can be varied depending on the rated voltage and rated capacity required of the battery rack (10).

[0049] Meanwhile, the arrow shown in FIG. 1 exemplarily indicates the direction of current flow when the battery rack (10) is discharged. The input and output terminals of the battery rack (10) can be defined relatively according to the operating mode of the battery rack (10). That is, during the discharge operation, the terminal connected to the negative terminal (-) of the DC bus becomes the input terminal where current flows into the battery rack (10), and the terminal connected to the positive terminal (+) of the DC bus becomes the output terminal where current flows out from the battery rack (10).

[0050] On the other hand, during charging operation, the terminal connected to the positive terminal (+) of the DC bus becomes the input terminal through which current flows into the battery rack (10), and the terminal connected to the negative terminal (-) of the DC bus becomes the output terminal through which current flows out from the battery rack (10). That is, in this specification, the input terminal can be interpreted as the terminal through which current flows into the battery rack (10) in the corresponding operation mode, and the output terminal as the terminal through which current flows out from the battery rack (10).

[0051] More specifically, the current flowing into the input terminal of the battery rack (10) can be branched into multiple paths and each branched path is defined as a string in this specification. One or more battery modules can be connected in series to each string.

[0052] For example, the multiple strings through which the current from the input terminal of the battery rack (10) branches off are the first strings branched off from the negative terminal (-) or positive terminal (+) of the DC bus, and in FIG. 1, there are two strings on the positive terminal (+) side and two strings on the negative terminal (-) side.

[0053] However, the number of strings and the number of battery modules included in each string shown in FIG. 1 are merely examples to aid in understanding the present invention, and the number of strings and the number of battery modules included in each string may be varied according to the specifications required for the battery rack (10).

[0054] Meanwhile, in the actual battery rack (10) operating environment, differences in the rate of degradation among multiple battery modules may occur due to manufacturing variations of each battery module, temperature variations depending on the installation location, and differences in charge / discharge history.

[0055] These differences in degradation rates can cause premature decline in the lifespan of specific battery modules and deterioration in the performance of the entire battery rack (10), and the present invention aims to solve such problems by controlling the current of each battery module based on the cumulative degradation and relative degradation of a plurality of battery modules as described below.

[0057] FIG. 2 is a block diagram of a battery rack control device according to some embodiment of the present invention.

[0058] As illustrated in FIG. 2, the battery rack control device may include a battery rack (10), a data collection unit (20), a first switch (30), a second switch (40), a processor (50), a memory (60), and a third switch (70).

[0059] A battery rack (10) can have multiple battery modules connected in series and parallel.

[0060] The battery rack (10) can function as an energy storage device that stores power and supplies the stored power externally. Specifically, the battery rack (10) can perform a charging operation that stores power supplied from an external power source, a power conversion system (PCS), or a grid in the form of chemical energy, and a discharging operation that converts the stored chemical energy into electrical energy and supplies it to a load or grid. As the battery rack (10) has been described in detail in FIG. 1, further description is omitted below.

[0061] The data collection unit (20) can collect operation data of multiple battery modules.

[0062] Here, the operation data may include the voltage, temperature, number of charge / discharge cycles, and operating time of multiple battery modules.

[0063] The voltage of a battery module may refer to the potential difference measured between the positive and negative terminals of each battery module. The voltage of a battery module may fluctuate depending on the State of Charge (SOC), charge / discharge status, and the degree of degradation of the battery module. The voltage of a battery module can be measured through a voltage sensor equipped in each battery module.

[0064] The temperature of a battery module may refer to the temperature measured inside or on the surface of each battery module. The temperature of a battery module may be measured through a temperature sensor equipped in each battery module (e.g., a thermistor, a thermocouple, or a resistance temperature detector (RTD), etc.). If the temperature of a battery module is high, it can accelerate the degradation of the battery module.

[0065] The number of charge-discharge cycles of a battery module may refer to the cumulative number of times each battery module has repeatedly performed charging and discharging operations. Specifically, the number of charge-discharge cycles may refer to the number of times a battery module has been fully charged once, and in the case of partial charge-discharge, the number of charge-discharge cycles may be determined by dividing the amount of partial charge-discharge by the maximum charge-discharge amount. For example, if the maximum charge-discharge amount of a battery module is 10 kWh and the charge-discharge amount in the corresponding charge-discharge cycle is 5 kWh, the number of charge-discharge cycles may be determined to be 0.5 times. It may be determined that the greater the number of charge-discharge cycles of a battery module, the greater the cumulative degradation of the battery module, and the number of charge-discharge cycles can be used as an indicator to quantitatively represent the degradation of the battery module. According to one embodiment, the data collection unit (20) may collect the number of charge-discharge cycles by monitoring the direction of the current of each battery module and counting the number of times the direction of the current switches from the charging direction to the discharging direction, or from the discharging direction to the charging direction.

[0066] The operating time of a battery module may refer to the cumulative time during which each battery module has operated. Specifically, the operating time may refer to the time from when the battery module first began operation until the present time.

[0067] According to one embodiment, the time at which the battery module first started operating is stored in the memory (60) to be described later, and the data collection unit (20) can collect the operating time of each battery module by calculating the difference between the time at which each battery module started operating stored in the memory (60) and the current time. Alternatively, the data collection unit (20) may collect the operating time of the battery module by receiving operating time information recorded in the Battery Management System (BMS) that manages each battery module. The operating time of the battery module can also affect the degree of degradation of the battery module. The longer the operating time of the battery module, the more it can act as a factor that accelerates the degradation of the battery module. Therefore, it can be determined that the longer the operating time of the battery module, the greater the cumulative degradation of the battery module, and the operating time can be used as an indicator to quantitatively represent time-dependent degradation factors that are not reflected by the number of charge / discharge cycles alone.

[0068] The data collection unit (20) is electrically connected to the processor (50) and can transmit the collected operation data to the processor (50).

[0069] The first switch (30) can regulate the current between battery modules connected in parallel among a plurality of battery modules, and the second switch (40) can regulate the current of a plurality of strings through which the current of the input terminal of the battery rack (10) branches and flows, and the first switch (30) and the second switch (40) may be multiple.

[0070] The first switch (30) and the second switch (40) may include semiconductor switching elements capable of Pulse Width Modulation (PWM) control. For example, the first switch (30) and the second switch (40) may include at least one of a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET), a Gallium Nitride (GaN) power device, an Insulated Gate Bipolar Transistor (IGBT), or a Solid State Relay (SSR). The first switch (30) and the second switch (40) are electrically connected to a processor (50), so that the conduction rate can be controlled according to the duty ratio of a PWM signal applied from the processor (50), and accordingly, the current flowing through each of the parallel-connected battery modules can be finely adjusted.

[0071] Meanwhile, the first switch (30) and the second switch (40) may further include a mechanical switching element in addition to the semiconductor switching element. The semiconductor switching element may have limitations in that conduction loss occurs due to on-resistance in the conduction state, and there is a possibility that the failure will proceed in a short-circuit mode upon failure, making it difficult to physically completely insulate the battery module. To compensate for these limitations, the first switch (30) may further include a mechanical switching element along with the semiconductor switching element, and the mechanical switching element may be connected in series or parallel with the semiconductor switching element. For example, the mechanical switching element may include at least one of an electromagnetic contactor (MC) in which contacts are opened and closed by electromagnetic force, an electromagnetic relay (EMR) in which contacts are operated by an electromagnet, a latching relay in which the open / closed state is maintained using a latch structure, and a pre-charge relay.

[0072] When the first switch (30) and the second switch (40) include both semiconductor switching elements and mechanical switching elements, the processor (50) finely controls the current flowing to each of the parallel-connected battery modules through PWM control of the semiconductor switching elements during normal operation, and can physically isolate the battery module from the battery rack (10) by opening the mechanical switching elements when the relative degradation of a specific battery module is excessively large or when a failure of the semiconductor switching element is detected. The case where the relative degradation of a specific battery module is excessively large may be a cutoff threshold (a case where the relative degradation of a specific battery module is 1.5 times or more of the threshold to be described later), etc. However, 1.5 times is merely an example and may be changed at will.

[0073] By providing both a semiconductor switching element and a mechanical switching element in this manner, the first switch (30) and the second switch (40) can simultaneously secure control precision capable of finely adjusting the current of the battery module and safety capable of physically completely insulating the battery module. Furthermore, the current control method by the first switch (30) will be described in detail later in FIG. 3, and the current control method by the second switch (40) will be described in detail later in FIG. 4.

[0074] The processor (50) can determine the cumulative degradation of a plurality of battery modules based on operation data, determine the relative degradation of a plurality of battery modules based on the cumulative degradation, and control the current of a plurality of battery modules based on the relative degradation of a plurality of battery modules.

[0075] Here, the cumulative degradation of a battery module refers to an indicator that quantitatively represents the degree of degradation of the battery module that has accumulated from the time each battery module first began operation until the present time. Specifically, the cumulative degradation of a battery module is a value that converts the accumulated extent of degradation phenomena, such as capacity reduction, increased internal resistance, and deterioration of output characteristics, into a single numerical value; a higher cumulative degradation value indicates that the degradation of the corresponding battery module has progressed significantly. The cumulative degradation of a battery module may be an indicator that includes both degradation caused by the charging and discharging operations of the battery module and degradation caused by the passage of operating time.

[0076] The cumulative degradation of a battery module can be determined in the following way.

[0077] First, the processor (50) can determine the cumulative charge / discharge amount of the battery module based on the voltage of the battery module and the current of the battery module collected by the data collection unit (20). Specifically, the cumulative charge / discharge amount of the battery module can be calculated as the cumulative charge amount obtained by integrating the current flowing through the battery module over time, or as the cumulative power amount (Watt-hour, Wh) obtained by integrating the product of the voltage and current of the battery module over time. The cumulative charge / discharge amount of the battery module can be expressed as follows [Equation 1].

[0078]

[0079] ( : Cumulative charge / discharge amount of the nth battery module, : Voltage of the nth battery module, : Current of the nth battery module, : Driving time)

[0080] Meanwhile, when the data collection unit (20) samples and collects the voltage and current of the battery module at regular intervals, the accumulated charge and discharge amount of the battery module may be calculated by discrete summation rather than continuous integral operation.

[0081] Next, the processor (50) can determine the cumulative degradation of the battery module based on the determined cumulative charge / discharge amount of the battery module and the temperature, charge / discharge cycles, and operating time of the battery module collected by the data collection unit (20). In one embodiment, the processor (50) can determine the cumulative degradation of the battery module by the sum of the value obtained by multiplying the cumulative charge / discharge amount of the battery module by a first weight, the value obtained by multiplying the temperature of the battery module by a second weight, the value obtained by multiplying the charge / discharge cycles of the battery module by a third weight, and the value obtained by multiplying the operating time of the battery module by a fourth weight. The cumulative degradation of the battery module can be expressed as follows [Equation 2].

[0082]

[0083] ( : Cumulative degradation of the nth battery module, : Cumulative charge / discharge amount of the nth battery module, : Temperature of the nth battery module, : Number of charge / discharge cycles of the nth battery module, : Operating time of the nth battery module, : 1st weight, : Second weight, : Third weight, : 4th weight)

[0084] At this time, the first weight, the second weight, the third weight, and the fourth weight may each be set to a value greater than or equal to 0 and less than or equal to 1. The value of each weight may be determined in advance based on the specifications of the battery module, the type of battery cell used in the battery module, the operating environment in which the battery rack (10) is installed, or experimental data regarding the degradation characteristics of the battery module, and in one embodiment, the sum of the first weight, the second weight, the third weight, and the fourth weight may be set to be 1. However, the specific value of each weight is not limited thereto, and depending on the embodiment, the sum of each weight may be set to a value different from 1.

[0085] In one embodiment, the first weight may be set to a value of approximately 0.4 to 0.6, the second weight may be set to a value of approximately 0.1 to 0.3, the third weight may be set to a value of approximately 0.1 to 0.2, and the fourth weight may be set to a value of approximately 0.05 to 0.15. This reflects the fact that, generally, the influence of cycle degradation caused by the accumulated charge / discharge amount on the degradation of the battery module is the greatest, followed by the influence of temperature, and the influence of the number of charge / discharge cycles and operating time is relatively small. That is, among the first weight, the second weight, the third weight, and the fourth weight, the first weight may be set to be the largest.

[0086] In another embodiment, the second, third, and fourth weights may all be set to 0, and only the first weight may be set to a value greater than 0 (e.g., 1). In this case, the terms regarding temperature, number of charge / discharge cycles, and operating time in [Equation 2] may all be eliminated, so that the cumulative degradation of the battery module can be determined based only on the cumulative charge / discharge amount of the battery module. That is, the cumulative charge / discharge amount of the battery module itself can be considered as the cumulative degradation of the battery module. In this case, the computational load of the processor (50) is reduced, so battery rack control according to the present invention can be performed efficiently even in an environment where computational resources are limited.

[0087] And, each variable ( , , , ) can undergo a normalization process before being combined with weights. For example, each variable can be normalized to a value between 0 and 1 by dividing it by its maximum value or the rated value of the battery module, thereby allowing variables with different units and ranges to be summed on the same basis.

[0088] In another embodiment, the processor (50) may determine the cumulative degradation of the battery module by further considering at least one of the time-based weight and the location-based weight. This is because, in an actual operating environment, the magnitude of the degradation stress applied to the battery module may differ depending on the time of day when the battery module is operating and the location where the battery module is installed within the battery rack (10). Specifically, even if the same charge / discharge operation is performed, the degradation of the battery module may proceed more rapidly in the time period when the battery module is exposed to a high-temperature environment or high-load operation is performed. For example, if the operating time of the battery module is during the afternoon hours of the summer (e.g., 12:00 to 18:00), the operating temperature of the battery module tends to rise and the charge / discharge current tends to increase due to the rise in ambient temperature and the increase in power demand, and the charge / discharge operation performed in such an environment may have a greater impact on the degradation of the battery module than the charge / discharge operation performed during the low-temperature / low-load time period. To reflect this, the processor (50) can determine the cumulative charge / discharge amount by time by multiplying the operating time-time weight corresponding to the time of each sampling point in the part calculating the cumulative charge / discharge amount when calculating the cumulative charge / discharge amount of the battery module, and the method of determining the cumulative charge / discharge amount by operating time may be as shown in [Equation 3] below.

[0089]

[0090] ( : Cumulative charge / discharge amount of the nth battery module, : Voltage of the nth battery module, : Current of the nth battery module, : Driving time, : Weights by driving time period)

[0091] For example, the weights for each operating time period may be set as follows. The weights for each operating time period may be set to 1.2 for high temperature or high load time periods (e.g., 12:00 to 18:00), 1 for normal operating time periods (e.g., 06:00 to 12:00 or 18:00 to 24:00), and 0.7 for low load or standby time periods (e.g., 00:00 to 06:00).

[0092] By applying weights based on the operating time period in this way, even if the charging and discharging operations involve the same amount of current flow, the charging and discharging operations performed during the high temperature / high load time period can be reflected more significantly in the cumulative degradation of the battery module. Through this, the processor (50) can determine the cumulative degradation that more precisely reflects the actual progression of degradation of the battery module.

[0093] Next, the processor (50) may determine the cumulative degradation by applying different location-specific weights according to the physical location where the battery module is installed within the battery rack (10).

[0094] Generally, the battery rack (10) may have a structure in which a plurality of battery modules are stacked in a vertical direction, and in this structure, the battery modules located at the top of the battery rack (10) may be exposed to a relatively higher temperature environment than the battery modules located at the bottom due to the phenomenon of heat convection.

[0095] As such, the installation location of the battery module can affect the rate of degradation of the battery module. To reflect this, the processor (50) can correct the cumulative degradation of the battery module by multiplying the location-specific weight corresponding to the installation location of each battery module by the battery module.

[0096] For example, the positional weight of a battery module installed at the top of the battery rack (10) can be set to 1.1, the positional weight of a battery module installed at the center of the battery rack (10) can be set to 1, and the positional weight of a battery module installed at the bottom of the battery rack (10) can be set to 0.9. Applying positional weights in this way is intended to reflect the degradation contribution of the battery module located at the top and exposed to a relatively high-temperature environment more significantly in the cumulative degradation degree. The positional weights can be set to a predetermined fixed value.

[0097] When both the weighting by driving time period and the weighting by location are reflected, the cumulative degradation of the battery module can be expressed as follows [Equation 4].

[0098]

[0099] ( : Cumulative degradation of the nth battery module reflecting weights by driving time period and location, : Cumulative charge / discharge amount of the nth battery module reflecting weights by driving time period, : Temperature of the nth battery module, : Number of charge / discharge cycles of the nth battery module, : Operating time of the nth battery module, : 1st weight, : Second weight, : Third weight, : 4th weight, : Position-specific weights corresponding to the installation location of the nth battery module)

[0100] Meanwhile, the processor (50) can periodically update the cumulative degradation of the battery module determined in the manner described above. Specifically, the processor (50) can recalculate and update the cumulative degradation of the battery module whenever the voltage, temperature, number of charge / discharge cycles, and operating time of the battery module are collected from the data collection unit (20) or at preset intervals, and the updated cumulative degradation can be stored in the memory (60) and utilized for the calculation of relative degradation and current control described later.

[0101] If the cumulative degradation of each battery module has been determined, the processor (50) can determine the relative degradation of each of the multiple battery modules based on the cumulative degradation of the multiple battery modules.

[0102] Here, the relative degradation of a battery module refers to an indicator representing the degree of deviation in the degradation of a specific battery module relative to the average degradation of multiple battery modules. Specifically, the relative degradation is a normalized numerical value indicating how much higher or lower the cumulative degradation of a specific battery module is compared to the average cumulative degradation of multiple battery modules; a positive (+) value of the relative degradation indicates that the degradation of the battery module has progressed more than the average, while a negative (-) value indicates that the degradation of the battery module has progressed less than the average.

[0103] The relative degradation of a battery module can be determined in the following manner.

[0104] First, the processor (50) can calculate the average value of the cumulative degradation of multiple battery modules. The average value of the cumulative degradation of multiple battery modules can be expressed as [Equation 5].

[0105]

[0106] ( : Average value of cumulative degradation of multiple battery modules, : Total number of battery modules included in the battery rack (10), : Cumulative degradation of the nth battery module)

[0107] Next, the processor (50) can determine the relative degradation of each battery module by subtracting the average value from the cumulative degradation of each battery module and dividing the result by the average value. The relative degradation of the battery module can be expressed as follows [Equation 6].

[0108]

[0109] ( : Relative degradation of the nth battery module, : Cumulative degradation of the nth battery module, : Average value of cumulative degradation of multiple battery modules)

[0110] For example, assuming that the battery rack (10) includes four battery modules (battery module 1 to battery module 4) and the cumulative degradation of battery module 1 is 120, the cumulative degradation of battery module 2 is 100, the cumulative degradation of battery module 3 is 80, and the cumulative degradation of battery module 4 is 100, the average value of the cumulative degradation is (120 + 100 + 80 + 100) / 4 = 100. In this case, the relative degradation of battery module 1 becomes (120 - 100) / 100 = +0.2, the relative degradation of battery module 2 becomes (100 - 100) / 100 = 0, the relative degradation of battery module 3 becomes (80 - 100) / 100 = -0.2, and the relative degradation of battery module 4 becomes (100 - 100) / 100 = 0.

[0111] A relative degradation of battery module 1 of +0.2 means that the cumulative degradation of battery module 1 is 20% higher than the average, and a relative degradation of battery module 3 of -0.2 means that the cumulative degradation of battery module 3 is 20% lower than the average. The processor (50) can control the current of multiple battery modules based on the determined relative degradation.

[0112] Specifically, the processor (50) can reduce the current of a battery module when the relative degradation of the battery module is above a preset threshold. Here, the threshold can be set according to the operating environment of the battery rack (10) and the required allowable degradation deviation range, for example, it can be set to a value in the range of 0.05 to 0.3. The smaller the threshold, the more sensitively current control is initiated regarding degradation deviation between battery modules, and the larger the threshold, the more current control is initiated only when degradation deviation above a certain level occurs.

[0113] For example, if the threshold is set to 0.1, the relative degradation of battery module 1 in the above-described numerical example is +0.2, which exceeds the threshold (0.1), so the processor (50) can perform control to reduce the current flowing through battery module 1. On the other hand, the relative degradation of battery module 2 is 0, the relative degradation of battery module 3 is -0.2, and the relative degradation of battery module 4 is 0, all of which are below the threshold, so the processor (50) can maintain the current of the battery modules or increase the current in response to the reduced amount of current in battery module 1. Through this, the current stress applied to battery module 1 is relieved, the rate of degradation of battery module 1 is reduced, and the effect of the degradation deviation between multiple battery modules converging in the long term can be obtained.

[0114] Meanwhile, when the processor (50) reduces the current of a battery module whose relative degradation level is above a threshold value, it can reduce the current by controlling at least one of the first switch (30) and the second switch (40). Specifically, the processor (50) can control the first switch (30) to regulate the current in units of parallel-connected battery modules, and can control the second switch (40) to regulate the current in units of strings containing the battery modules. The current control method by the first switch (30) and the second switch (40) will be described in more detail later.

[0115] The processor (50) may include an Electronic Control Unit (ECU), a Central Processing Unit (CPU), a Graphics Processing Unit (GPU), a Digital Signal Processing Unit (DSP), a memory (60), or a similar type of computing device.

[0116] A memory (60) may store instructions for performing each step of the method according to the present invention. The memory (60) may include at least one of a flash memory type, a hard disk type, a multimedia card micro type, a card type memory (e.g., SD or XD memory, etc.), RAM (Random Access Memory), SRAM (Static Random Access Memory), ROM (Read-Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), PROM (Programmable Read-Only Memory), Mask ROM, Flash ROM, etc.), a hard disk drive (HDD), or a solid-state drive (SSD).

[0117] A third switch (70) is placed between two battery modules connected in series to regulate or limit the current in the string between the two battery modules, and there may be multiple third switches (70).

[0118] Specifically, as described in FIG. 1, when the battery rack (10) includes battery modules 1 to 8 and each pair of modules is connected in series to form a total of 4 strings, the third switch (70) can be placed one each between battery module 1 and battery module 2, between battery module 3 and battery module 4, between battery module 5 and battery module 6, and between battery module 7 and battery module 8.

[0119] The third switch (70) may include a semiconductor switching element capable of PWM control, similar to the first switch (30) and the second switch (40).

[0120] The third switch (70) is electrically connected to the processor (50) and can be controlled by the processor (50). The processor (50) can limit the magnitude of the current flowing through the string in which the third switch (70) is placed or the rate of change of the current by adjusting the PWM duty ratio of the semiconductor switching element included in the third switch (70).

[0121] Specifically, the processor (50) obtains the current between battery modules connected in series through the data collection unit (20), and if it is determined that the magnitude of the current or the rate of change of the current is greater than or equal to a preset value, it can control the third switch (70) placed in the string to limit the current flowing in the string.

[0122] That is, if it is determined that the magnitude of the current flowing in a specific string is greater than or equal to a preset current upper limit, the processor (50) can limit the magnitude of the current flowing in the string to less than or equal to the current upper limit by reducing the PWM duty ratio of the third switch (70) placed in the string. Alternatively, if it is determined that the rate of change of the current flowing in the specific string per hour is greater than or equal to a preset rate of change upper limit, the processor (50) can limit the rate of change of the current flowing in the string to less than or equal to the rate of change upper limit by adjusting the PWM duty ratio of the third switch (70) placed in the string. Here, the current upper limit or the rate of change upper limit may be preset based on the electrochemical characteristics of the battery module.

[0123] When a sudden fluctuation in power demand occurs and the magnitude of the current flowing in a specific string exceeds the allowable range or the rate of change of the current increases rapidly, the third switch (70) limits the magnitude of the current flowing in the string and the rate of change of the current to a preset value or lower, thereby preemptively mitigating the peak current and instantaneous current stress applied to the battery module within the string, thereby reducing the rate of long-term degradation of the battery module and improving the operational stability of the battery rack (10).

[0125] FIG. 3 is an illustrative diagram for explaining a current control method by a first switch according to some embodiment of the present invention.

[0126] Referring to FIG. 3, the first switch (30) can be individually connected between each of the plurality of battery modules and the positive terminal (+) or negative terminal (-) of the DC bus. Specifically, in the embodiment illustrated in FIG. 3, the first switch (30) can be connected one by one between the positive terminal (+) of the DC bus and battery modules 1, 3, 5, and 7, and one by one between the negative terminal (-) of the DC bus and battery modules 2, 4, 6, and 8. That is, a total of eight first switches (30) can be provided for eight battery modules.

[0127] At this time, the processor (50) can independently control the current flowing to each battery module by individually adjusting the duty ratio of the PWM signal for each of the plurality of first switches (30). At this time, as described above in FIG. 1, the input and output terminals of the battery rack (10) are defined relatively according to the operating mode of the battery rack (10), so the position of the first switch (30) controlled by the processor (50) may also differ according to the operating mode of the battery rack (10).

[0128] During a discharge operation, the negative terminal (-) of the DC bus becomes the input terminal of the battery rack (10), and the positive terminal (+) of the DC bus becomes the output terminal of the battery rack (10). In this case, the current flowing into the input terminal branches into each string at the point where battery modules 2, 4, 6, and 8 are connected, then follows each string through battery modules 2, 4, 6, and 8, passes through battery modules 1, 3, 5, and 7, and then flows out through the positive terminal (+) of the DC bus, which is the output terminal. Therefore, the magnitude of the current branched into each string during a discharge operation can be determined by the duty cycle of the first switch (30) connected to the bottom of battery modules 2, 4, 6, and 8, and the processor (50) can control the first switch (30) connected to the bottom of battery modules 2, 4, 6, and 8 to regulate the current flowing through each string.

[0129] For example, if it is determined that the relative degradation of battery module 2 during a discharge operation is greater than or equal to a preset threshold, the processor (50) can reduce the current branched to the string containing battery module 2 by reducing the duty cycle of the first switch (30) connected to the bottom of battery module 2. At this time, the duty cycle of the first switch (30) connected to the bottom of battery modules 4, 6, and 8, which are in a parallel relationship with battery module 2, may be maintained or increased, and accordingly, the current may be redistributed to the strings containing battery modules 4, 6, and 8 in response to the reduced current in the string containing battery module 2. Meanwhile, during the discharge operation, the first switch (30) connected to the top of battery modules 1, 3, 5, and 7 is located on the output side and forms a current path that is already joined and flows out from each string, so the processor (50) can maintain the first switch (30) connected to the top of battery modules 1, 3, 5, and 7 in a constantly conductive state during the discharge operation.

[0130] On the other hand, during charging operation, the positive terminal (+) of the DC bus becomes the input terminal of the battery rack (10), and the negative terminal (-) of the DC bus becomes the output terminal of the battery rack (10). In this case, the current flowing into the input terminal is branched into each string at the point where battery modules 1, 3, 5, and 7 are connected, then follows each string through battery modules 1, 3, 5, and 7, passes through battery modules 2, 4, 6, and 8, and then flows out through the negative terminal (-) of the DC bus, which is the output terminal. Therefore, the magnitude of the current branched into each string during charging operation can be determined by the duty cycle of the first switch (30) connected to the top of battery modules 1, 3, 5, and 7, and the processor (50) can control the first switch (30) connected to the top of battery modules 1, 3, 5, and 7 to regulate the current flowing through each string.

[0131] For example, if it is determined that the relative degradation of battery module 1 is above a threshold value during a charging operation, the processor (50) can reduce the current branched to the string containing battery module 1 by reducing the duty cycle of the first switch (30) connected to the top of battery module 1. At this time, the duty cycle of the first switch (30) connected to the top of battery modules 3, 5, and 7, which are in a parallel relationship with battery module 1, may be maintained or increased. Meanwhile, since the first switch (30) connected to the bottom of battery modules 2, 4, 6, and 8 is located on the output side during a charging operation, the processor (50) can maintain the first switch (30) connected to the bottom of battery modules 2, 4, 6, and 8 in a constantly conductive state during a charging operation.

[0132] In addition, if the first switch (30) includes a mechanical switching element in addition to a semiconductor switching element, the processor (50) determines whether the semiconductor switching element included in the first switch (30) is faulty, and by opening the mechanical switching element corresponding to the semiconductor switching element determined to be faulty, the battery modules connected in series with the corresponding battery module can be physically isolated from the battery rack (10). Furthermore, the processor (50) can open the mechanical switching element of the first switch (30) connected to the battery module even if the accumulated degradation of the specific battery module is excessively large.

[0133] For example, assume a case where the cumulative degradation of battery module 2 exceeds a preset isolation threshold (hereinafter set to a value greater than the threshold for relative degradation control), or where a short or open failure is detected in the semiconductor switching element of the first switch (30) connected to battery module 2.

[0134] In this case, the processor (50) may output a control signal to open not only the mechanical switching element included in the first switch (30) connected to the bottom of battery module 2 but also the mechanical switching element included in the first switch (30) connected to the top of battery module 1, in order to physically isolate battery module 1 and battery module 2 from the battery rack (10). By opening both mechanical switching elements located at both ends of the string in this way, battery module 1 and battery module 2 can be cut off from both the positive terminal (+) and the negative terminal (-) of the DC bus and completely separated from the current path.

[0135] Meanwhile, fault detection of semiconductor switching devices can be performed in various ways.

[0136] For example, the processor (50) can compare the duty cycle of the PWM signal output to the first switch (30) with the current measurement value of the battery module collected through the data collection unit (20), and if a current that does not correspond to the output duty cycle flows, it can determine that a fault has occurred in the semiconductor switching element of the first switch (30). Specifically, if current continues to flow in the battery module even though the processor (50) has set the duty cycle of the semiconductor switching element to 0, it can determine that a short circuit fault has occurred; conversely, if current does not flow in the battery module even though the duty cycle has been set to a value other than 0, it can determine that an open circuit fault has occurred.

[0137] In this way, by providing both a semiconductor switching element and a mechanical switching element in the first switch (30), the current is finely controlled through the semiconductor switching element during normal operation to reduce the degradation variation between battery modules, while in the event of a serious abnormality in a specific battery module, the string containing the battery module is physically isolated through the mechanical switching element, thereby ensuring the safety and continuity of operation of the entire battery rack (10) at the same time.

[0139] FIG. 4 is an illustrative diagram for explaining a current control method by a second switch according to some embodiment of the present invention.

[0140] Referring to FIG. 4, the second switch (40) can regulate the current of a plurality of strings through which the current of the input terminal of the battery rack (10) branches. Specifically, two second switches (40) may be placed at the branching point between the positive terminal (+) of the DC bus and the battery module, and two second switches may be placed at the branching point between the negative terminal (-) of the DC bus and the battery module, so that a total of four second switches (40) may be provided.

[0141] More specifically, one second switch (40) placed on the positive terminal (+) side of the DC bus is commonly connected to battery module 1 and battery module 3 to regulate the current flowing into or out of battery module 1 and battery module 3 together, and another second switch (40) placed on the positive terminal (+) side of the DC bus is commonly connected to battery module 5 and battery module 7 to regulate the current flowing into or out of battery module 5 and battery module 7 together.

[0142] Likewise, one second switch (40) placed on the negative terminal (-) side of the DC bus is commonly connected to battery module 2 and battery module 4 to regulate the current flowing into or out of battery module 2 and battery module 4 together, and another second switch (40) placed on the negative terminal (-) side of the DC bus is commonly connected to battery module 6 and battery module 8 to regulate the current flowing into or out of battery module 6 and battery module 8 together.

[0143] In this way, the second switch (40) can be distinguished from the first switch (30) in the following respects. First, the first switch (30) described in FIG. 3 is individually connected to each of the multiple battery modules to regulate the current on a per-battery module basis, whereas the second switch (40) is connected in common to the multiple battery modules to regulate the current on a per-battery module basis. For example, unlike FIG. 3 where a total of 8 first switches (30) are provided for 8 battery modules, FIG. 4 provides a total of 4 second switches (40), and one second switch (40) can be connected in common to 2 battery modules.

[0144] In addition, the first switch (30) can be distinguished in that it is suitable for individually and finely controlling the current flowing through a specific battery module when only the relative degradation of that specific battery module is locally high, whereas the second switch (40) is suitable for collectively controlling the current flowing through the battery modules when the relative degradation of multiple battery modules is generally high or when a wide degradation variation occurs.

[0145] Accordingly, it can be understood that the first switch (30) is responsible for precise current control at the battery module level, and the second switch (40) is responsible for extensive current control at the current path level that first branches off from the input terminal of the battery rack (10).

[0146] The second switch (40) may include a semiconductor switching element capable of PWM control, similar to the first switch (30), and may also include a mechanical switching element in addition to the semiconductor switching element. The processor (50) can independently control the current flowing to the battery modules managed by each second switch (40) by individually adjusting the duty ratio of the PWM signal for each of the plurality of second switches (40). At this time, just as the input and output terminals of the battery rack (10) are defined relatively according to the operating mode, the second switch (40) controlled by the processor (50) may differ according to the operating mode of the battery rack (10).

[0147] According to one embodiment, the processor (50) can control a plurality of second switches (40) to reduce the current of a string connected to one second switch (40) when the relative degradation of more than a set number of battery modules among the battery modules whose current is controlled by one second switch (40) is greater than a preset value.

[0148] For example, if the relative degradation of battery module 2 and battery module 4 during a discharge operation is above a preset threshold and the number of settings is 2, the processor (50) can reduce the duty cycle of the second switch (40) that is commonly connected to battery module 2 and battery module 4. In this case, the current flowing into battery module 2 and battery module 4 connected to the second switch (40) is reduced together, and the duty cycle of the second switch (40) that is relatively commonly connected to battery module 6 and battery module 8 is maintained or increased, so that the current can be redistributed to battery module 6 and battery module 8 by the amount of the reduced current. Meanwhile, since the second switch (40) placed on the positive terminal (+) side of the DC bus during a discharge operation is located on the output terminal side, the processor (50) can maintain the second switch (40) placed on the positive terminal (+) side of the DC bus in a constantly conductive state during a discharge operation.

[0149] On the other hand, during charging operation, the positive terminal (+) of the DC bus becomes the input terminal of the battery rack (10), so the current flowing into the input terminal is branched by two second switches (40) placed on the positive terminal (+) side of the DC bus and distributed to battery modules 1, 3, 5, and 7. Accordingly, during charging operation, the processor (50) can control the second switches (40) placed on the positive terminal (+) side of the DC bus to regulate the current flowing to battery modules 1, 3, 5, and 7.

[0150] For example, if it is determined that it is necessary to reduce the current flowing through battery module 1 or battery module 3 during a charging operation, the processor (50) can reduce the duty cycle of the second switch (40) that is commonly connected to battery module 1 and battery module 3. Meanwhile, since the second switch (40) placed on the negative terminal (-) side of the DC bus during a charging operation is located on the output terminal side, the processor (50) can maintain the second switch (40) placed on the negative terminal (-) side of the DC bus in a constantly conductive state during a charging operation.

[0151] According to one embodiment, the processor (50) can selectively or stepwise control the first switch (30) and the second switch (40) depending on the scale and pattern of degradation variation between battery modules.

[0152] For example, if the relative degradation of multiple battery modules managed by the second switch (40) is generally high, the processor (50) first controls the second switch (40) to collectively reduce the current flowing to the battery modules, and then, if it is necessary to additionally adjust only the relative degradation of a specific battery module among the battery modules, it controls the first switch (30) to finely adjust the current on an individual battery module basis.

[0153] Conversely, if only the relative degradation of a specific battery module is locally high, the processor (50) may control only the first switch (30) to reduce the current flowing to the battery module.

[0154] In this way, by combining individual battery module unit control by the first switch (30) and batch control of multiple battery modules by the second switch (40) in stages, the degradation deviation of the battery rack (10) can be managed more effectively and flexibly.

[0155] Additionally, if the second switch (40) includes a mechanical switching element in addition to a semiconductor switching element, the processor (50) can open the mechanical switching element to physically isolate the battery modules from the battery rack (10) when the cumulative degradation of a plurality of battery modules managed by a specific second switch (40) is excessively large or when a failure of the semiconductor switching element included in the second switch (40) is detected.

[0156] For example, if a situation arises where battery modules 1 to 4 must be isolated from the battery rack (10), the processor (50) can completely disconnect battery modules 1 to 4 from the DC bus by opening together the mechanical switching element of the second switch (40) that is commonly connected to battery modules 1 and 3 on the positive terminal (+) side of the DC bus and the mechanical switching element of the second switch (40) that is commonly connected to battery modules 2 and 4 on the negative terminal (-) side of the DC bus. In this case, the remaining battery modules 5 to 8, excluding the isolated battery modules 1 to 4, can continue to operate normally, and the processor (50) can stably maintain the output power of the battery rack (10) by adjusting the duty cycle of the second switch (40) connected to battery modules 5 to 8 in a direction that increases it.

[0157] Meanwhile, as with the first switch (30), the processor (50) may determine whether the semiconductor switching element included in the second switch (40) is faulty and may open the mechanical switching element of the second switch (40) corresponding to the semiconductor switching element determined to be faulty. The determination of whether the semiconductor switching element is faulty may be performed by comparing the duty cycle of the PWM signal output by the processor (50) to the second switch (40) with the current measurement values ​​of the battery modules commonly connected to the second switch (40) collected through the data collection unit (20), and determining that a fault has occurred in the semiconductor switching element of the second switch (40) if a current that does not correspond to the output duty cycle flows.

[0158] For example, if a fault is detected in a semiconductor switching element of a second switch (40) that is commonly connected to battery module 1 and battery module 3, the processor (50) can disconnect the strings containing battery module 1 and battery module 3 from the DC bus by opening a mechanical switching element included in the second switch (40). In this case, the remaining battery modules 5 to 8 that are not isolated can continue to operate normally.

[0160] FIG. 5 is an illustrative diagram for explaining a current control method by a first switch and a second switch according to some embodiments of the present invention.

[0161] Referring to FIG. 5, a battery rack (10) according to some embodiment of the present invention may include both a first switch (30) and a second switch (40).

[0162] Specifically, a total of four second switches (40) may be placed at the branching point between the positive terminal (+) and negative terminal (-) of the DC bus and the battery module, and a total of eight first switches (30) may be placed, one between each second switch (40) and each battery module. Accordingly, the current path flowing from the DC bus to each battery module may be configured to pass sequentially from the positive terminal (+) or negative terminal (-) of the DC bus through the second switch (40) and the first switch (30) to the corresponding battery module.

[0163] In one embodiment, when the relative degradation of at least one battery module among a plurality of battery modules whose current is controlled by a specific second switch (40) is greater than a preset threshold, the processor (50) can first reduce the current flowing into the plurality of battery modules connected to the second switch (40) by reducing the PWM duty ratio of the second switch (40).

[0164] For example, if it is determined that the relative degradation of battery module 2 among battery module 2 and battery module 4, whose current is controlled by a second switch (40) commonly connected to battery module 2 and battery module 4 during a discharge operation, is greater than or equal to a preset threshold, the processor (50) can reduce the PWM duty ratio of the second switch (40) commonly connected to battery module 2 and battery module 4. Accordingly, the current flowing into battery module 2 and battery module 4 is reduced together, and the PWM duty ratio of the second switch (40) commonly connected to battery module 6 and battery module 8 is maintained or increased relatively, so that the current can be redistributed to strings containing battery module 6 and battery module 8 by the amount of the reduced current.

[0165] According to the collective adjustment of the second switch (40), even if current reduction is required only for some of the multiple battery modules commonly connected to one second switch (40), the corresponding second

[0166] For example, a situation may occur where the relative degradation of battery module 2 is above a threshold value but the relative degradation of battery module 4 is below a threshold value, and the current flowing through battery module 4 is also reduced by the reduction in the duty cycle of the second switch (40) that is commonly connected to battery module 2 and battery module 4. In this case, the current flowing through the relatively healthy battery module 4 is excessively reduced, which may lower the output efficiency of the battery rack (10).

[0167] In order to respond to this situation, the processor (50) can additionally control the first switch (30) in addition to the control of the second switch (40) performed in the first step to individually fine-tune the current flowing to each of the plurality of battery modules commonly connected to the second switch (40).

[0168] For example, the processor (50) can control the current flowing through the second switch (40) to be distributed less toward the battery module 2 side and relatively more toward the battery module 4 side by relatively reducing the PWM duty ratio of the first switch (30) connected to the bottom of the battery module 2 and relatively reducing or maintaining the PWM duty ratio of the first switch (30) connected to the bottom of the battery module 4. Accordingly, the current stress applied to the battery module 2, where the relative degradation level is above a threshold value, is effectively relieved, while the current flowing through the battery module 4, where the relative degradation level is below a threshold value, can be controlled so that it is not excessively reduced.

[0169] According to the stepwise current control method described above, collective current redistribution to multiple battery modules can be performed more efficiently compared to the case where only the first switch (30) is provided, and fine current control at the individual battery module level is possible compared to the case where only the second switch (40) is provided.

[0171] FIG. 6 is a flowchart of a battery rack control method according to some embodiments of the present invention. Specific descriptions of configurations that overlap with the foregoing are omitted, and the description focuses on the chronological configuration.

[0172] First, the processor (50) can obtain operation data of each of the multiple battery modules through the data collection unit (20) (S201).

[0173] Here, the operation data may include the voltage, temperature, number of charge / discharge cycles, and operating time of a plurality of battery modules. The processor (50) may obtain the operation data collected at each sampling cycle preset by the data collection unit (20) from the memory (60) or receive it directly from the data collection unit (20).

[0174] After step S201, the processor (50) can determine the cumulative charge / discharge amount of the plurality of battery modules based on the voltage and current of the plurality of battery modules obtained (S202).

[0175] Specifically, the processor (50) can calculate the accumulated charge / discharge amount of each battery module by sequentially accumulating the value obtained by multiplying the product of the voltage and current collected at each sampling point by the sampling period over time.

[0176] The processor (50) can determine the cumulative deterioration of the multiple battery modules based on the cumulative charge / discharge amount of the multiple battery modules, the temperature of the multiple battery modules, the number of charge / discharge cycles, and the operating time (S203).

[0177] Specifically, the processor (50) can determine the cumulative degradation of the battery module by the sum of the value obtained by multiplying the cumulative charge / discharge amount by a first weight, the value obtained by multiplying the temperature by a second weight, the value obtained by multiplying the number of charge / discharge cycles by a third weight, and the value obtained by multiplying the operating time by a fourth weight. At this time, the first weight, the second weight, the third weight, and the fourth weight can each be set to a value greater than or equal to 0 and less than or equal to 1, and in one embodiment, the first weight among the first weight, the second weight, the third weight, and the fourth weight can be set to the largest value.

[0178] Next, the processor (50) can determine the relative degradation of each battery module based on the cumulative degradation of the determined plurality of battery modules (S204).

[0179] Specifically, the processor (50) can first calculate the average value of the cumulative degradation of a plurality of battery modules and determine the value obtained by subtracting the average value from the cumulative degradation of each battery module and dividing the result by the average value as the relative degradation of the battery module.

[0180] Next, the processor (50) can determine whether the relative degradation of each battery module determined in step (S204) exceeds a preset threshold value (S205). Here, the threshold value may be a preset value based on the operating environment of the battery rack (10) and the required allowable degradation deviation range.

[0181] If it is determined that the relative degradation of a specific battery module exceeds a threshold value (e.g., S205), the processor (50) can perform control to reduce the current flowing through the battery module (S206).

[0182] Specifically, the processor (50) can reduce the current flowing to the battery module by controlling the first switch (30) connected to the battery module among the plurality of first switches (30).

[0183] Additionally, the processor (50) may reduce the current flowing through the string by controlling the second switch (40) among the plurality of second switches (40) that is connected to the string containing the battery module. At this time, the processor (50) may selectively control only one of the first switch (30) and the second switch (40), or it may control the first switch (30) and the second switch (40) together in stages. The specific current control method by the first switch (30) and the second switch (40) is as described above in FIGS. 3 and FIGS. 4.

[0184] FIG. 7 is a flowchart of a battery rack control method according to some embodiments of the present invention. Specific descriptions of configurations that overlap with the foregoing are omitted, and the description focuses on the chronological configuration.

[0185] The battery rack control method illustrated in FIG. 7 can be distinguished from the battery rack control method illustrated in FIG. 6 in that, unlike the battery rack control method illustrated in FIG. 6 which directly reduces the current flowing to a battery module whose relative degradation is greater than or equal to a preset value based on the relative degradation of a plurality of battery modules, the power path through which current flows within the battery rack (10) is newly determined based on the relative degradation of a plurality of battery modules, and the power path of the battery rack (10) is reconfigured by controlling the first switch (30) or the second switch (40) accordingly.

[0186] First, the processor (50) can obtain operation data of each of the multiple battery modules through the data collection unit (20) (S301).

[0187] Here, the operation data may include the voltage, temperature, number of charge / discharge cycles, and operating time of a plurality of battery modules. The processor (50) may obtain the operation data collected at each sampling cycle preset by the data collection unit (20) from the memory (60) or receive it directly from the data collection unit (20).

[0188] After step S301, the processor (50) can determine the cumulative charge / discharge amount of the plurality of battery modules based on the voltage and current of the plurality of battery modules obtained (S302).

[0189] Specifically, the processor (50) can calculate the accumulated charge / discharge amount of each battery module by sequentially accumulating the value obtained by multiplying the product of the voltage and current collected at each sampling point by the sampling period over time.

[0190] The processor (50) can determine the cumulative deterioration of the multiple battery modules based on the cumulative charge / discharge amount of the multiple battery modules, the temperature of the multiple battery modules, the number of charge / discharge cycles, and the operating time (S303).

[0191] Specifically, the processor (50) can determine the cumulative degradation of the battery module by the sum of the value obtained by multiplying the cumulative charge / discharge amount by a first weight, the value obtained by multiplying the temperature by a second weight, the value obtained by multiplying the number of charge / discharge cycles by a third weight, and the value obtained by multiplying the operating time by a fourth weight. At this time, the first weight, the second weight, the third weight, and the fourth weight can each be set to a value greater than or equal to 0 and less than or equal to 1, and in one embodiment, the first weight among the first weight, the second weight, the third weight, and the fourth weight can be set to the largest value.

[0192] Next, the processor (50) can determine the relative degradation of each battery module based on the cumulative degradation of the determined plurality of battery modules (S304).

[0193] Specifically, the processor (50) can first calculate the average value of the cumulative degradation of a plurality of battery modules and determine the value obtained by subtracting the average value from the cumulative degradation of each battery module and dividing the result by the average value as the relative degradation of the battery module.

[0194] After the relative degradation of multiple battery modules is determined, the processor (50) can determine the power path of the battery rack (10) based on the determined relative degradation (S305).

[0195] Here, the power path of the battery rack (10) may refer to the path through which current flowing into the input terminal of the battery rack (10) flows through a plurality of battery modules until it flows out to the output terminal. At this time, the current of each battery module may be determined according to the conduction state of the first switch (30) and the second switch (40), and the processor (50) can actively reconfigure the power path of the battery rack (10) by adjusting the combination of the conduction states of the first switch (30) and the second switch (40).

[0196] In one embodiment, the processor (50) can determine the power path of the battery rack (10) by selecting a string among a plurality of strings that does not include a high-temperature module as a candidate path and determining the current distributed to each candidate path based on the path score of each selected candidate path.

[0197] Specifically, the processor (50) may determine a battery module among a plurality of battery modules whose relative degradation level exceeds a preset threshold as a high degradation module. For example, as shown in FIG. 1, it is assumed that the battery rack (10) includes battery modules 1 to 8, and each pair of modules is connected in series to form a total of four strings (a string in which battery module 1 and battery module 2 are connected in series, a string in which battery module 3 and battery module 4 are connected in series, a string in which battery module 5 and battery module 6 are connected in series, and a string in which battery module 7 and battery module 8 are connected in series). In this case, if it is determined that the relative degradation level of battery module 6 exceeds the threshold, the processor (50) may determine battery module 6 as a high degradation module.

[0198] Next, the processor (50) may select a string that does not contain a high-degradation module as a candidate path. That is, a string containing a high-degradation module is excluded from the candidate path, and only the remaining strings can be selected as candidate paths. For example, as described above, if battery module 6 is determined to be a high-degradation module, a string in which battery module 5 and battery module 6 are connected in series is excluded from the candidate path, and a string in which battery module 1 and battery module 2 are connected in series, a string in which battery module 3 and battery module 4 are connected in series, and a string in which battery module 7 and battery module 8 are connected in series can be selected as candidate paths.

[0199] The processor (50) can determine a path score for each candidate path that indicates the priority of each candidate path. The path score of each candidate path can be expressed as [Equation 7].

[0200]

[0201] ( : Path score of the k-th candidate path : Average relative degradation of the k-th candidate path, : Average temperature of battery modules included in the k-th candidate path, : Average cumulative charge / discharge amount of battery modules included in the k-th candidate path, : Maximum value among the temperatures of the entire battery module, : Maximum value among the cumulative charge / discharge amounts of the entire battery module , , : Weight)

[0202] According to [Mathematical Formula 7] The smaller the, The smaller the, The smaller the value, the larger the path score of the corresponding candidate path can be determined, and the larger the path score of the candidate path, the more suitable the path may be for sharing the output power of the battery rack (10). In one embodiment, the weighting factor 0.4 to 0.6, is 0.2 to 0.3, Each can be set to a value in the range of 0.1 to 0.3. For example, if the relative degradation of battery module 1 is -0.15 and the relative degradation of battery module 2 is +0.05, the average relative degradation of a string in which battery module 1 and battery module 2 are connected in series can be determined as -0.05, which is the average of the two values. However, depending on the embodiment, the largest value among the relative degradations of the battery modules in the string may be determined as the average relative degradation of the string, and in such a case, the effect of placing greater emphasis on safety aspects, such as preventing overcurrent from flowing through the most degraded battery module in the string, can be obtained.

[0203] Next, the processor (50) can determine the priority of all candidate paths sequentially by comparing the path scores of the determined multiple candidate paths, determining the candidate path with the largest path score as the first priority power path, and determining the candidate path with the second largest path score as the second priority power path.

[0204] At this time, the priority of the candidate paths is not intended to exclusively select only one candidate path, but rather to have multiple candidate paths share the output power of the battery rack (10), and to determine the magnitude of the current shared by each candidate path differentially.

[0205] The processor (50) can determine the current distributed to each candidate path in proportion to the path score of each candidate path. The current distributed to each candidate path can be expressed as follows [Equation 8].

[0206]

[0207] ( : Current distributed to the k-th candidate path, : Total input current required for the battery rack (10), : Path score of the k-th candidate path, : Sum of path scores of all candidate paths)

[0208] Here This may mean current flowing into the battery modules included in the candidate path through the first switch (30) connected to the candidate path.

[0209] That is, the processor (50) of each candidate path Determines and, in response, adjusts the PWM duty ratio of the first switch (30) so that the current flowing into the corresponding candidate path It can be controlled to become so.

[0210] For example, in FIG. 1, battery module 6 is determined to be a high-temperature module, so a string in which battery module 5 and battery module 6 are connected in series is excluded from the candidate path, and a string in which battery module 1 and battery module 2 are connected in series, a string in which battery module 3 and battery module 4 are connected in series, and a string in which battery module 7 and battery module 8 are connected in series are selected as candidate paths, and the total output current of the battery rack (10) is assumed to be 100A.

[0211] In this case, assuming that the path score of the string in which battery module 1 and battery module 2 are connected in series is the largest, the path score of the string in which battery module 3 and battery module 4 are connected in series is the second largest, and the path score of the string in which battery module 7 and battery module 8 are connected in series is the third largest, the processor (50) can determine, according to [Equation 8], that approximately 40A is distributed to the string in which battery module 1 and battery module 2 are connected in series, approximately 35A is distributed to the string in which battery module 3 and battery module 4 are connected in series, and approximately 25A is distributed to the string in which battery module 7 and battery module 8 are connected in series. Meanwhile, the current distributed to the string in which battery module 5 and battery module 6 containing the high-temperature module are connected in series can be determined to be 0A.

[0212] Next, the processor (50) can adjust the actual power path of the battery rack (10) to match the determined power path by controlling the first switch (30) or the second switch (40) according to the current of each determined candidate path (S306).

[0213] According to one embodiment, the processor (50) can control a plurality of first switches (30) individually connected to each of a plurality of battery modules to control the current flowing to the battery modules included in each candidate path.

[0214] Specifically, in a structure in which a first switch (30) is individually connected to each of a plurality of battery modules as shown in FIG. 3, when discharging, the first switch (30) placed on the negative terminal (-) side of the DC bus (i.e., the first switch (30) connected to the bottom of battery modules 2, 4, 6, and 8) controls the current branched to each string, so the processor (50) can control the PWM duty ratio of the first switch (30) placed on the negative terminal (-) side of the DC bus.

[0215] For example, as previously assumed, if battery module 6 is determined to be a high-temperature module and the string in which battery module 5 and battery module 6 are connected in series is excluded from the candidate path, and the total output current of the battery rack (10) is 100A, and it is determined according to [Equation 9] that 40A is distributed to the string in which battery module 1 and battery module 2 are connected in series, 35A to the string in which battery module 3 and battery module 4 are connected in series, and 25A to the string in which battery module 7 and battery module 8 are connected in series, the processor (50) controls the supply of 40A to the string in which battery module 1 and battery module 2 are connected in series by adjusting the duty cycle of the first switch (30) connected to the bottom of battery module 2, and controls the supply of 35A to the string in which battery module 3 and battery module 4 are connected in series by adjusting the duty cycle of the first switch (30) connected to the bottom of battery module 4. By adjusting the duty cycle of the first switch (30) connected to the bottom of battery module 8, 25A can be controlled to flow into the string in which battery module 7 and battery module 8 are connected in series.

[0216] Additionally, the processor (50) can physically isolate the string by setting the duty cycle of the first switch (30) connected to the bottom of the battery module 6 to 0 so that the current flowing through the string containing the battery module 6, which is a high-temperature module, becomes 0A, or by opening the mechanical switching element included in the first switch (30).

[0217] Meanwhile, during charging operation, the first switch (30) placed on the positive terminal (+) side of the DC bus (i.e., the first switch (30) connected to the top of battery modules 1, 3, 5, and 7) controls the current branched to each string, so the processor (50) can control the PWM duty ratio of the first switch (30) placed on the positive terminal (+) side of the DC bus. For example, during charging operation, the processor (50) can control the current flowing into the string in which battery module 1 and battery module 2 are connected in series to 40A by adjusting the duty ratio of the first switch (30) connected to the top of battery module 1, and control can be performed by setting the duty ratio of the first switch (30) connected to the top of battery module 5 to 0 to cut off the string containing battery module 6, which is a high-temperature module.

[0218] According to one embodiment, the processor (50) can control a plurality of second switches (40) to regulate the current flowing into each candidate path.

[0219] Specifically, in a structure in which a second switch (40) is placed at each branch point between the positive terminal (+) and negative terminal (-) of the DC bus and a plurality of battery modules as shown in FIG. 4, during a discharge operation, the second switch (40) placed on the negative terminal (-) side of the DC bus (i.e., the second switch (40) commonly connected to battery module 2 and battery module 4 and the second switch (40) commonly connected to battery module 6 and battery module 8) controls the current branched to each string, so the processor (50) can control the PWM duty ratio of the second switch (40) placed on the negative terminal (-) side of the DC bus.

[0220] For example, if it is determined that 40A is distributed to a string in which battery module 1 and battery module 2 are connected in series, and 35A is distributed to a string in which battery module 3 and battery module 4 are connected in series, the processor (50) can control the PWM duty cycle of a second switch (40) commonly connected to battery module 2 and battery module 4 so that the sum of the currents flowing into the two strings (40A + 35A = 75A) is distributed to the battery module 2 and battery module 4 sides through the second switch (40).

[0221] Additionally, the processor (50) may selectively or in combination perform the first embodiment and the second embodiment. For example, the processor (50) may control the second switch (40) to collectively adjust the current in units of multiple strings, and then control the first switch (30) to finely adjust the current in units of individual battery modules included in each string. By controlling the first switch (30) and the second switch (40) in combination in stages in this way, both precision and efficiency of power path reconfiguration of the battery rack (10) can be secured.

[0222] Meanwhile, the processor (50) can continuously monitor the degradation status of several battery modules after a new power path is determined by the presence of a high-temperature module.

[0223] Specifically, when a battery module is identified as a high-degradation module and its string is blocked, the accumulated charge / discharge amount of that battery module does not increase while the state in which current does not flow through that string is maintained, whereas the battery modules included in the remaining candidate paths continue to perform charge / discharge operations by the distributed current, so the accumulated charge / discharge amount of those battery modules continues to increase. Accordingly, as time passes, the accumulated degradation of the remaining battery modules increases, while the accumulated degradation of the battery module identified as a high-degradation module does not increase relatively; as a result, the average value of the accumulated degradation of multiple battery modules increases, and the relative degradation of the battery module identified as a high-degradation module can gradually decrease.

[0224] Accordingly, the processor (50) updates the relative degradation of each battery module at preset intervals and, based on the updated relative degradation, determines whether the relative degradation of a battery module determined to be a high degradation module has decreased to below a preset return threshold. Here, the return threshold may be set to a value smaller than the threshold for determining a high degradation module, for example, it may be set to 0.7 times the threshold for determining a high degradation module.

[0225] When it is determined that the relative degradation level of a battery module determined to be a high-degradation module has decreased below a return threshold, the string containing the battery module that has been released from high-degradation module determination is included again in the candidate path, and the processor (50) can reset the power path of the battery rack (10) by newly determining the path score for all candidate paths including the string that has been released from high-degradation module determination and newly determining the current distributed to each candidate path.

[0227] Through this, according to the present invention, by controlling the current of each battery module based on the cumulative degradation and relative degradation of a plurality of battery modules, the degradation variation between battery modules can be reduced and the lifespan of the entire battery rack can be extended.

[0228] According to the present invention, by reducing the current of a battery module whose relative degradation is greater than a preset value, the phenomenon of current and thermal stress being concentrated in a specific battery module can be prevented, and thereby the operational stability of the battery rack can be improved.

[0229] According to the present invention, by calculating the cumulative degradation degree by comprehensively reflecting the cumulative charge / discharge amount, temperature, number of charge / discharge cycles, and operating time of a battery module, it is possible to perform a quantitative and accurate degradation evaluation that considers both cycle degradation and calendar degradation.

[0230] According to the present invention, by providing a first switch for controlling the current between parallel-connected battery modules and a second switch for controlling the current of a plurality of strings, current control at the battery module level and current redistribution at the string level can be performed in stages.

[0231] Although the present invention has been described with reference to the embodiments illustrated in the drawings, this is merely illustrative, and those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible therefrom.

[0232] Therefore, the technical scope of protection of the present invention should be determined by the following patent claims. Explanation of the symbols

[0235] 10: Battery Rack 20: Data Collection Department 30: 1st switch 40: Second switch 50: Processor 60: Memory 70: Third switch

Claims

Claim 1 A battery rack control device characterized by comprising: a battery rack in which a plurality of battery modules are connected in series and parallel; a data collection unit for collecting operation data of the plurality of battery modules; and a processor for determining the cumulative degradation degree of each of the plurality of battery modules based on the operation data, determining the relative degradation degree of each of the battery modules based on the cumulative degradation degree of each of the battery modules, and controlling the current of the plurality of battery modules based on the relative degradation degree of each of the battery modules. Claim 2 A battery rack control device according to claim 1, wherein the operation data includes the voltage, temperature, number of charge / discharge cycles, and operating time of each battery module. Claim 3 A battery rack control device according to paragraph 2, wherein the processor determines the cumulative charge / discharge amount of each battery module based on the voltage of each battery module and the current of each battery module, and determines the cumulative deterioration degree of each battery module based on the cumulative charge / discharge amount, the temperature, the number of charge / discharge cycles, and the operating time. Claim 4 A battery rack control device according to claim 3, wherein the processor determines the cumulative degradation of the battery module by the sum of the value obtained by multiplying the cumulative charge / discharge amount of the battery module by a first weight, the value obtained by multiplying the temperature of the battery module by a second weight, the value obtained by multiplying the number of charge / discharge cycles of the battery module by a third weight, and the value obtained by multiplying the operating time of the battery module by a fourth weight, wherein the first weight is the largest among the first weight, the second weight, the third weight, and the fourth weight. Claim 5 A battery rack control device according to paragraph 3, wherein the processor determines the cumulative degradation of each battery module by further considering the operating time-based weighting of each battery module. Claim 6 A battery rack control device according to paragraph 3, wherein the processor determines the cumulative degradation degree of each battery module by further considering the positional weight of each battery module. Claim 7 A battery rack control device according to claim 1, wherein the processor determines the relative degradation of each battery module by dividing the value obtained by subtracting the average value of the cumulative degradation of each battery module from the cumulative degradation of each battery module by the average value. Claim 8 A battery rack control device according to claim 1, further comprising a plurality of first switches for controlling the current between parallel-connected battery modules among the plurality of battery modules, wherein the processor controls the plurality of first switches to reduce the current of a battery module whose relative degradation is greater than or equal to a preset value. Claim 9 A battery rack control device according to claim 8, wherein the processor opens a first switch connected to the battery module when the relative degradation degree of the battery module is greater than or equal to a cutoff threshold. Claim 10 A battery rack control device according to claim 8, further comprising a plurality of second switches for controlling the current of a plurality of strings through which the current of the input terminal of the battery rack is branched and flows; wherein the processor controls the plurality of second switches to reduce the current of the string connected to the single second switch when the relative degradation degree of a set number or more of battery modules among the battery modules whose current is controlled by a single second switch is greater than or equal to a preset value. Claim 11 A battery rack control device according to claim 10, wherein each first switch and second switch comprises a semiconductor switch and a mechanical switch, and the processor determines whether the semiconductor switch is faulty and opens the mechanical switch of the first switch or second switch corresponding to the semiconductor switch determined to be faulty. Claim 12 A battery rack control method characterized by comprising: a step in which a processor acquires operation data of a plurality of battery modules; a step in which the processor determines the cumulative degradation degree of each battery module based on the operation data; a step in which the processor determines the relative degradation degree of each battery module based on the cumulative degradation degree of each battery module; and a step in which the processor controls the current of the plurality of battery modules based on the relative degradation degree of each battery module. Claim 13 A battery rack control method according to claim 12, wherein the operation data includes the voltage, temperature, number of charge / discharge cycles, and operating time of each of the battery modules. Claim 14 A battery rack control method according to claim 13, wherein in the step of determining the cumulative degradation degree, the processor determines the cumulative charge / discharge amount of each battery module based on the voltage of each battery module and the current of each battery module, and determines the cumulative degradation degree of each battery module based on the cumulative charge / discharge amount, the temperature, the number of charge / discharge cycles, and the operating time. Claim 15 A battery rack control method according to claim 13, wherein in the step of determining the cumulative degradation degree, the processor determines the cumulative degradation degree of the battery module by the sum of the value obtained by multiplying the cumulative charge / discharge amount of the battery module by a first weight, the value obtained by multiplying the temperature of the battery module by a second weight, the value obtained by multiplying the number of charge / discharge cycles of the battery module by a third weight, and the value obtained by multiplying the operating time of the battery module by a fourth weight, wherein the first weight is the largest among the first weight, the second weight, the third weight, and the fourth weight. Claim 16 A battery rack control method according to claim 14, characterized in that, in the step of determining the cumulative degradation degree, the cumulative degradation degree of each battery module is determined by further considering the weighting of each battery module according to the operating time period. Claim 17 A battery rack control method according to claim 14, characterized in that, in the step of determining the cumulative degradation degree, the cumulative degradation degree of each battery module is determined by further considering the positional weight of each battery module. Claim 18 A battery rack control method according to claim 12, characterized in that, in the step of determining the relative degradation degree, the processor determines the relative degradation degree of each battery module by dividing the value obtained by subtracting the average value of the cumulative degradation degree of each battery module from the cumulative degradation degree of each battery module by the average value. Claim 19 A battery rack control method according to claim 12, wherein, in the step of controlling the current of each of the above-mentioned battery modules, the processor controls a plurality of first switches that regulate the current between parallel-connected battery modules among the plurality of battery modules to reduce the current of a battery module whose relative degradation degree is greater than or equal to a preset value. Claim 20 A battery rack control method according to claim 19, wherein in the step of controlling the current of each of the above-mentioned battery modules, the processor opens a first switch connected to the battery module to cut off the current of the battery module when the relative degradation degree of the battery module is greater than or equal to a cutoff threshold. Claim 21 A battery rack control method according to claim 19, wherein, in the step of controlling the current of each of the above-mentioned battery modules, the processor controls the plurality of second switches to reduce the current of the string connected to the one second switch when the relative degradation degree of more than a set number of battery modules among the battery modules whose current is controlled by one of the plurality of second switches that regulate the current of the input terminal of the battery rack is greater than or equal to a preset value. Claim 22 A battery rack control method according to claim 21, wherein each first switch and second switch comprises a semiconductor switch and a mechanical switch, and in the step of controlling the current of each battery module, the processor determines whether the semiconductor switch is faulty and opens the mechanical switch corresponding to the semiconductor switch determined to be faulty.

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