Battery management system and battery management method

Abstract

A battery management device and a battery management method are disclosed. According to the present invention, a virtual terminal voltage can be calculated as a representative voltage using the actual terminal voltage of each battery cell and the maximum value of the change in terminal voltage, and using this, a current limit value that can be allowed in a battery pack can be accurately calculated so that the battery cells do not exceed the operating voltage range.

Description

Technology Field

[0001] The present invention relates to a battery management device capable of accurately calculating a limit value of the current allowed to a battery pack in order to prevent battery cells from deteriorating by exceeding the operating voltage range during charging and discharging of the battery pack. Background Technology

[0002] As a general method for estimating the state of a battery (SoC: State Of Charge, SoH: State Of Health, internal resistance, etc.) used in the Battery Management System (BMS) of an electric vehicle, there is a method of determining the state of the battery by selecting a representative voltage of the battery pack that represents multiple battery cells.

[0003] The battery management system uses the determined battery status to calculate a current limit value for charging and discharging the battery, which is the range between the upper voltage limit during charging and the lower voltage limit during discharging. This is because if the battery cell voltage repeatedly exceeds the upper and lower voltage boundaries—that is, the operating voltage range—during charging and discharging, cell degradation occurs, negatively impacting battery life. However, actual battery packs exhibit variations in the state of individual cells from the initial stages of production, and these variations can increase as the electric vehicle operates. When such variations between battery cells increase, the error in estimating the battery status using the representative voltage of multiple cells also increases.

[0004] Figure 1a shows the change in terminal voltage over time in the case of an ideal battery pack. Referring to Figure 1a, each battery cell included in the ideal battery pack has the same internal resistance, current capacity, etc., so the rate of decrease in terminal voltage over time is constant and they have the same terminal voltage, so there is no problem in determining the battery state by using the average voltage of any one battery cell or battery cells as the representative voltage.

[0005] In contrast, Fig. 1b shows the change in terminal voltage over time in the case of an actual battery pack. Referring to Fig. 1b, since each battery cell included in the actual battery pack has different internal resistance, current capacity, etc., and thus the rate of decrease in terminal voltage over time varies, an error occurs if the state of the battery is estimated by simply using the average voltage of a single battery cell or the battery cells as the representative voltage.

[0006] If an error occurs during battery state estimation, an error also occurs when calculating the current limit value based on the state estimation. This results in battery cells that continuously degrade beyond the operating voltage range during charging and discharging, which can ultimately lead to a decrease in the overall efficiency of the battery pack and a reduction in the stability of the battery pack, potentially causing the electric vehicle to stop while in operation. Prior art literature

[0007] Published Patent Application No. 10-2013-0110355 The problem to be solved

[0008] The present invention aims to provide a battery management device and a battery management method capable of accurately calculating a current limit value to prevent battery cells constituting a battery pack from exceeding an operating voltage range. means of solving the problem

[0009] A battery management device according to the present invention comprises: a virtual voltage calculation unit that calculates a virtual representative voltage by measuring the terminal voltage of each of a plurality of battery cells constituting a battery pack; and a current calculation unit that calculates a current limit value based on the virtual representative voltage to prevent the plurality of battery cells from exceeding an operating voltage.

[0010] Here, when the battery pack is charged, the virtual representative voltage calculated by the virtual voltage calculation unit can be calculated using the terminal voltage of the battery cell with the highest terminal voltage at the previous measurement point among the battery cells and the change in terminal voltage of the battery cell with the largest change in terminal voltage among the battery cells.

[0011] In addition, when the battery pack is charged, the virtual representative voltage calculated by the virtual voltage calculation unit can be calculated through the following mathematical formula.

[0012]

[0013] (Here, V k,vir CHA is the current measurement time t when the above battery pack is being charged k The above-mentioned virtual representative voltage at, and V k-1,max is the previous measurement point t k-1 In the above battery cells, it is the terminal voltage of the battery cell with the highest terminal voltage, and ΔV CHA is the change in terminal voltage of the battery cell with the largest change in terminal voltage among the battery cells when the battery pack is charged.)

[0014] In addition, when the battery pack is discharged, the virtual representative voltage calculated by the virtual voltage calculation unit can be calculated using the terminal voltage of the battery cell with the lowest terminal voltage at the previous measurement point among the battery cells and the change in terminal voltage of the battery cell with the largest change in terminal voltage among the battery cells.

[0015] In addition, when the battery pack is discharged, the virtual representative voltage calculated by the virtual voltage calculation unit can be calculated through the following mathematical formula.

[0016]

[0017] (Here, V k,vir DCH is the current measurement time t when the above battery pack is dischargedk The above-mentioned virtual representative voltage at, and V k-1,min is the previous measurement point t k-1 In the above battery cells, it is the terminal voltage of the battery cell with the lowest terminal voltage, and ΔV DCH is the change in terminal voltage of the battery cell with the largest change in terminal voltage among the battery cells when the battery pack is discharged.)

[0018] In addition, the virtual voltage calculation unit calculates a representative internal resistance of the battery pack using the current flowing through the battery pack and the calculated virtual representative voltage, and the current calculation unit can calculate a current limit value such that the virtual representative voltage does not exceed the upper or lower limit of the operating voltage using the virtual representative voltage, the current flowing through the battery pack, and the representative internal resistance.

[0019] In addition, the virtual voltage calculation unit calculates the internal resistance of the battery cell with the largest internal resistance among the battery cells as the representative internal resistance of the battery pack, and the current calculation unit can calculate the current limit value such that the virtual representative voltage does not exceed the upper or lower limit of the operating voltage by using the virtual representative voltage, the current flowing through the battery pack, and the representative internal resistance.

[0020] A battery management method according to the present invention comprises: a step of calculating a virtual representative voltage by measuring the terminal voltage of each of a plurality of battery cells constituting a battery pack; and a step of calculating a current limit value based on the virtual representative voltage to prevent the plurality of battery cells from exceeding an operating voltage.

[0021] At this time, the virtual representative voltage calculated in the step of calculating the virtual representative voltage can be calculated using the terminal voltage of the battery cell with the highest terminal voltage at the previous measurement point among the battery cells and the change in terminal voltage of the battery cell with the largest change in terminal voltage among the battery cells when the battery pack is charged.

[0022] In addition, the virtual representative voltage calculated in the step of calculating the virtual representative voltage can be calculated through the following mathematical formula when the battery pack is charged.

[0023]

[0024] (Here, V k,vir CHA is the current measurement time t when the above battery pack is being charged k The above-mentioned virtual representative voltage at, and V k-1,max is the previous measurement point t k-1 In the above battery cells, it is the terminal voltage of the battery cell with the highest terminal voltage, and ΔV CHA is the change in terminal voltage of the battery cell with the largest change in terminal voltage among the battery cells when the battery pack is charged.)

[0025] In addition, the virtual representative voltage calculated in the step of calculating the virtual representative voltage may be calculated using the battery cell with the lowest terminal voltage at the previous measurement point among the battery cells and the battery cell with the largest change in terminal voltage among the battery cells when the battery pack is discharged.

[0026] In addition, the virtual representative voltage calculated in the step of calculating the virtual representative voltage can be calculated through the following mathematical formula when the battery pack is discharged.

[0027]

[0028] (Here, V k,vir DCHis the current measurement time t when the above battery pack is discharged k The above-mentioned virtual representative voltage at, and V k-1,min is the previous measurement point t k-1 In the above battery cells, it is the terminal voltage of the battery cell with the lowest terminal voltage, and ΔV DCH is the change in terminal voltage of the battery cell with the largest change in terminal voltage among the battery cells when the battery pack is discharged.)

[0029] Meanwhile, the battery management method according to the present invention may further include a step of calculating a representative internal resistance of the battery pack after the step of calculating the virtual representative voltage; wherein the representative internal resistance calculated in the step of calculating the representative internal resistance of the battery pack is calculated using the current flowing through the battery pack and the calculated virtual representative voltage, and the step of calculating the current limit value may calculate the current limit value such that the virtual representative voltage does not exceed the upper or lower limit of the operating voltage by using the virtual representative voltage, the current flowing through the battery pack, and the representative internal resistance.

[0030] In addition, the battery management method according to the present invention may further include a step of calculating a representative internal resistance of the battery pack after the step of calculating the virtual representative voltage; wherein the representative internal resistance calculated in the step of calculating the representative internal resistance of the battery pack is calculated as the internal resistance of the battery cell with the largest internal resistance among the battery cells; and the step of calculating the current limit value may calculate the current limit value such that the virtual representative voltage does not exceed the upper or lower limit of the operating voltage by using the virtual representative voltage, the current flowing through the battery pack, and the representative internal resistance. Effects of the invention

[0031] According to the present invention, a virtual terminal voltage can be calculated as a representative voltage using the actual terminal voltage of each battery cell and the maximum value of the change in terminal voltage, and by using this, a current limit value can be accurately calculated to prevent the battery cells from exceeding the operating voltage range. Brief explanation of the drawing

[0032] Figure 1a is a diagram showing the change in terminal voltage over time of a battery cell included in an ideal battery pack. Figure 1b is a diagram showing the change in terminal voltage over time of a battery cell included in an actual battery pack. Figure 2 is a diagram showing a conventional Battery Management System (BMS). FIG. 3 is a drawing showing a battery management device according to the present invention. FIG. 4 is a graph illustrating a method for obtaining a virtual representative voltage in a battery management device according to the present invention. FIG. 5 is a flowchart illustrating a battery management method according to the present invention. Specific details for implementing the invention

[0033] The present invention will be described in detail below with reference to the attached drawings. Detailed descriptions of known functions and configurations that may unnecessarily obscure the essence of the invention will be omitted.

[0034] Additionally, terms such as ‘…part’, ‘module’ described in the specification refer to a unit that processes at least one function or operation, and this may be implemented in hardware, software, or a combination of hardware and software.

[0035] Figure 2 is a drawing showing a conventional battery management device.

[0036] Referring to FIG. 2, a conventional battery management device (10) receives a representative battery pack voltage, battery pack current, and temperature from a battery pack (20) and calculates a representative SoC (State of Charge), a representative SoH (State of Health), and a representative internal resistance (Rs) of the battery pack (20) in a state information calculation unit (11).

[0037] In addition, a current limit value is calculated in the current calculation unit (12) using the calculated representative internal resistance (Rs), the representative voltage of the battery pack, and the battery pack current to allow the battery pack (20) to be charged and discharged within the operating voltage range, and when the current limit value is transmitted to the VCU (vehicle Control Unit) (30), the load is adjusted so that a current within the current limit value flows to the battery pack (20).

[0038] At this time, the load can be an inverter that controls the motor, a charging device for charging the battery pack (20), etc.

[0039] However, as described above, in actual battery packs, the variation in terminal voltage between battery cells is severe, so if the terminal voltage of one cell is used as the representative voltage of the pack as in the conventional method, or if the average value of the terminal voltages of the battery cells is used as the representative voltage of the pack, the current limit value cannot be accurately calculated.

[0040] FIG. 3 is a drawing showing a battery management device according to the present invention.

[0041] Referring to FIG. 3, the battery management device (1000) according to the present invention includes a virtual voltage calculation unit (100) and a current calculation unit (200).

[0042] Here, the virtual voltage calculation unit (100) is configured to calculate a virtual representative voltage by measuring the terminal voltage of each of the plurality of battery cells constituting the battery pack (10), and measures the terminal voltage of each of the battery cells at a predetermined time interval (e.g., at 10-second intervals).

[0043] At this time, the virtual representative voltage is a variable required to obtain an optimized current limit value so that all battery cells included in the battery pack (10) do not exceed the upper or lower limit of the operating voltage.

[0044] In other words, the above-mentioned virtual representative voltage needs to be obtained by assuming the worst-case conditions so that the above-mentioned current limit value can be derived as an optimized value.

[0045] Below, how the virtual voltage calculation unit (100) calculates a virtual representative voltage is explained in two parts, divided into when the battery pack is charged and when it is discharged.

[0046] 1. When the battery pack is being charged

[0047] The virtual voltage calculation unit (100) calculates a virtual representative voltage when the battery pack is charged by using the battery cell with the highest terminal voltage at the previous measurement point among the plurality of battery cells constituting the battery pack and the battery cell with the largest change in terminal voltage among the battery cells.

[0048] More specifically, the virtual voltage calculation unit (100) can calculate a virtual representative voltage through the following mathematical formula 1 when the battery pack is charged.

[0049] [Mathematical Formula 1]

[0050]

[0051] Here, V k,vir CHA is the current measurement point t at the time of charging k The above-mentioned virtual representative voltage at, and V k-1,max is the previous measurement point t k-1 In the above battery cells, it is the terminal voltage of the battery cell with the highest terminal voltage during charging, and ΔV CHA is the terminal voltage change of the battery cell with the largest terminal voltage change during charging among the above battery cells.

[0052] FIG. 4 is a graph illustrating a method for obtaining a virtual representative voltage in a battery management device according to the present invention.

[0053] In FIG. 4, battery cells A, B, and C are used as examples for convenience of explanation. Referring to FIG. 4, first, the virtual voltage calculation unit (100) calculates the previous measurement time point t k-1 Among the battery cells, select battery cell C with the highest terminal voltage. Next, at the previous measurement time point t k-1 At the current measurement time t k The battery cell with the largest change in terminal voltage up to is selected. In Fig. 4, the previous measurement time point t k-1 At the current measurement time t k Battery cell A, which exhibits the steepest slope of the graph up to this point, is the battery cell with the largest change in terminal voltage during charging. Finally, as shown in Equation 1 above, at the previous measurement time point t k-1 The change in terminal voltage of battery cell A, ΔV, to the terminal voltage of cell C CHA Adding it gives the current time point t k The virtual representative voltage V k,vir CHA You can obtain.

[0054] Here, if we look at the meaning of the above mathematical formula 1, the terminal voltage of the battery cell having the largest terminal voltage at any measurement point during the charging of the battery pack is added to the terminal voltage of the battery cell having the largest terminal voltage change amount to obtain a virtual charging terminal voltage at the next measurement point, and no battery cell can have a terminal voltage exceeding the above virtual terminal voltage.

[0055] In other words, if a current limit value is calculated based on the aforementioned virtual terminal voltage, it is possible to prevent any battery cell constituting the battery pack from being charged beyond the upper limit of the operating voltage. Therefore, the aforementioned virtual terminal voltage can be used as a virtual representative voltage.

[0056] 2. When the battery pack is discharged

[0057] The virtual voltage calculation unit (100) calculates a virtual representative voltage when the battery pack is discharged by using the battery cell with the lowest terminal voltage at the previous measurement point among the plurality of battery cells constituting the battery pack and the battery cell with the largest change in terminal voltage among the battery cells.

[0058] More specifically, the virtual voltage calculation unit (100) can calculate a virtual representative voltage through the following mathematical formula 2 when the battery pack is discharged.

[0059] [Mathematical Formula 2]

[0060]

[0061] Here, V k,vir DCH is the current measurement point t during discharge k The above-mentioned virtual representative voltage at, and V k-1,min is the previous measurement point t k-1 Among the above battery cells, it is the battery cell with the lowest terminal voltage during discharge, and ΔV DCH is the terminal voltage change of the battery cell with the largest terminal voltage change during discharge among the above battery cells.

[0062] Here, if we look at the meaning of the above mathematical formula 2, a virtual terminal voltage is obtained by adding the change in terminal voltage of the battery cell with the largest change in terminal voltage (wherein the change in terminal voltage has a value less than 0) to the terminal voltage of the battery cell having the lowest terminal voltage at a given measurement point, and no battery cell can be discharged to a terminal voltage lower than the above virtual terminal voltage.

[0063] In other words, if the current limit value is calculated based on the aforementioned virtual terminal voltage, it is possible to prevent any battery cell from discharging below the lower limit of the operating voltage. Therefore, the aforementioned virtual terminal voltage can be used as a virtual representative voltage.

[0064] After calculating a virtual representative voltage (virtual representative voltage or virtual representative voltage), the virtual voltage calculation unit (100) can further calculate a representative internal resistance of the battery pack using the current flowing through the battery pack (20) and the calculated virtual representative voltage.

[0065] More specifically, the current measurement point (t k If a virtual representative voltage of ) has been calculated, the virtual voltage calculation unit (100) calculates the current measurement time (t k The current flowing through the battery pack (20) can be measured, and the representative internal resistance of the battery pack can be calculated using Ohm's law (V=IR) with the virtual representative voltage and the current.

[0066] Alternatively, the voltage calculation unit (100) may calculate the internal resistance of the battery cell having the largest internal resistance among the battery cells as the representative internal resistance of the battery pack.

[0067] Meanwhile, the current calculation unit (200) can calculate a current limit value such that the virtual representative voltage calculated from the virtual voltage calculation unit (100), the current flowing through the battery pack, and the representative internal resistance of the battery pack do not exceed the upper or lower limit of the operating voltage.

[0068] At this time, the operating voltage range is a voltage range in which the battery cell can be stably charged and discharged without deterioration, and for example, the upper limit of the operating voltage range may be 4.2V and the lower limit may be 2.7V.

[0069] More specifically, the current calculation unit (200) uses the following mathematical formula 3 to calculate the charging current limit value (I max CHA ) can be produced.

[0070] [Mathematical Formula 3]

[0071]

[0072] Here, Vmax is the upper limit of the operating voltage range and Vk,vir CHA is a virtual representative voltage at the current measurement time calculated from the virtual voltage calculation unit (100), and Rs is a representative internal resistance calculated from the virtual voltage calculation unit (100).

[0073] Here, if we examine the meaning of the above mathematical formula 3, the next measurement point (t) during charging k+1 The upper limit of the operating voltage (V) at ) max The current value calculated assuming it reaches (e.g., 4.2V), i.e., the charging current limit value (I max CHA It is to produce ).

[0074] Calculated charging current limit value (I max CHA If a current equal to ) flows, the upper limit of the operating voltage (V) at the next measurement point max Since a battery cell may reach ), the current calculation unit (200) calculates the charging current limit value (I) calculated above to the VCU. max CHA Along with ), the calculated charging current limit value (I max CHA A control signal can be sent to adjust the load so that a current of less than ) can flow.

[0075] In addition, the current calculation unit (200) uses the following mathematical formula 4 to obtain a discharge current limit value (I max DCH ) can be produced.

[0076] [Mathematical Formula 4]

[0077]

[0078] Here, if we examine the meaning of the above mathematical formula 4, the next measurement point (t) during discharge k+1 The lower limit of the operating voltage (V) at ) min The current value calculated assuming it reaches (e.g., 2.7V), i.e., the discharge current limit value (I max DCH It is to produce ).

[0079] Calculated discharge current limit value (I max DCH If the same current as ) flows, the next measurement point (t k+1 The lower limit of the operating voltage (V) at ) minSince a battery cell may reach ), the current calculation unit (200) sends the calculated discharge current limit value (I) to the VCU. max DCH Along with ), a control signal can be sent to adjust the load so that a current less than the calculated current limit value can flow.

[0080] As described above, the battery management device of the present invention can calculate a virtual terminal voltage as a representative voltage using the actual terminal voltage of each battery cell and the maximum value of the change in terminal voltage, and can calculate a current limit value having a maximum margin using this. When the current limit value is calculated to have a maximum margin, no battery cell exceeds the operating voltage range, and the accuracy of the calculated current limit value is guaranteed.

[0081] Meanwhile, FIG. 5 is a flowchart illustrating a battery management method of the present invention, and a battery management method according to one embodiment of the present invention can be performed by the battery management device (1000) described above.

[0082] Referring to FIG. 5, a battery management method according to one embodiment of the present invention first calculates a virtual representative voltage by measuring the terminal voltage of each of a plurality of battery cells constituting a battery pack (20) (S100).

[0083] At this time, in this step (S100), the virtual voltage calculation unit (100) can calculate a virtual representative voltage when the battery pack (20) is charged using the battery cell with the highest terminal voltage at the previous measurement time among the battery cells and the battery cell with the largest change in terminal voltage among the battery cells through the mathematical formula 1.

[0084] In addition, in this step (S100), the virtual voltage calculation unit (100) can calculate a virtual representative voltage when the battery pack (20) is discharged using the terminal voltage of the battery cell with the lowest terminal voltage at the previous measurement point among the battery cells and the voltage change amount of the battery cell with the largest terminal voltage change amount among the battery cells through the mathematical formula 2.

[0085] Next, the current calculation unit (200) calculates a current limit value based on the virtual representative voltage to prevent the plurality of battery cells from exceeding the operating voltage (S300).

[0086] At this time, after the step (S100) of calculating the virtual representative voltage, the virtual voltage calculation unit (100) may further include a step (S200) of calculating the representative internal resistance of the battery pack.

[0087] The representative internal resistance here may be calculated using Ohm's law with the current flowing through the battery pack and the calculated virtual representative voltage, or it may be calculated as the internal resistance of the battery cell having the largest internal resistance among the battery cells.

[0088] The step of calculating the current limit value (S300) can calculate a charging current limit value that prevents the virtual representative voltage from being charged beyond the upper limit of the operating voltage by using the virtual representative voltage, the current flowing through the battery pack, and the representative internal resistance when the representative internal resistance is calculated, through the mathematical formula 3.

[0089] In addition, the step (S300) of calculating the current limit value can calculate a discharge current limit value that prevents the virtual representative voltage from being discharged below the lower limit of the operating voltage by using the virtual representative voltage, the current flowing through the battery pack, and the representative internal resistance when the representative internal resistance is calculated, through the mathematical formula 4.

[0090] A more detailed description of the battery management method according to an embodiment of the present invention other than the above description of the battery management device (1000) according to the present invention may be substituted.

[0091] As described above, although the present invention has been explained by limited embodiments and drawings, the present invention is not limited to the above embodiments, and various modifications and variations are possible from this description by those skilled in the art to which the present invention belongs. Accordingly, the technical concept of the present invention should be understood only by the claims, and all equivalent or analogous variations thereof shall be considered to fall within the scope of the technical concept of the present invention. Explanation of the symbols

[0092] 10, 1000: Battery management unit 11: State Information Calculation Unit 100: Virtual voltage calculation unit 12, 200 : Current calculation unit

Claims

Claim 1 delete Claim 2 A battery management device comprising: a virtual voltage calculation unit that calculates a virtual representative voltage by measuring the terminal voltage of each of a plurality of battery cells constituting a battery pack; and a current calculation unit that calculates a current limit value to prevent the plurality of battery cells from exceeding an operating voltage using the virtual representative voltage, the current flowing through the battery pack, and the calculated representative internal resistance of the battery pack; wherein, when the battery pack is charged, the virtual representative voltage calculated by the virtual voltage calculation unit is calculated by adding the terminal voltage of the battery cell with the highest terminal voltage at the previous measurement time among the battery cells to the terminal voltage change amount of the battery cell with the largest terminal voltage change amount from the previous measurement time to the current measurement time among the battery cells. Claim 3 In paragraph 2, when the battery pack is charged, the virtual representative voltage calculated by the virtual voltage calculation unit is a battery management device calculated through the following mathematical formula 1.[Mathematical Formula 1] (Here, V k,vir CHA is the current measurement time t when the above battery pack is being charged k The above-mentioned virtual representative voltage at, and V k-1,max is the previous measurement point t k-1 In the above battery cells, it is the terminal voltage of the battery cell with the highest terminal voltage, and ΔV CHA is the change in terminal voltage of the battery cell with the largest change in terminal voltage among the battery cells when the battery pack is charged.) Claim 4 A battery management device comprising: a virtual voltage calculation unit that calculates a virtual representative voltage by measuring the terminal voltage of each of a plurality of battery cells constituting a battery pack; and a current calculation unit that calculates a current limit value to prevent the plurality of battery cells from exceeding an operating voltage using the virtual representative voltage, the current flowing through the battery pack, and the calculated representative internal resistance of the battery pack; wherein, when the battery pack is discharged, the virtual representative voltage calculated by the virtual voltage calculation unit is calculated by adding the terminal voltage of the battery cell with the lowest terminal voltage at the previous measurement point to the terminal voltage change amount of the battery cell with the largest terminal voltage change amount from the previous measurement point to the current measurement point among the battery cells, wherein the terminal voltage change amount is a value less than 0. Claim 5 In paragraph 4, when the battery pack is discharged, the virtual representative voltage calculated by the virtual voltage calculation unit is a battery management device calculated through the following mathematical formula 2.[Mathematical Formula 2] (Here, V k,vir DCH is the current measurement time t when the above battery pack is discharged k The above-mentioned virtual representative voltage at, and V k-1,min is the previous measurement point t k-1 In the above battery cells, it is the terminal voltage of the battery cell with the lowest terminal voltage, and ΔV DCH is the change in terminal voltage of the battery cell with the largest change in terminal voltage among the battery cells when the battery pack is discharged.) Claim 6 A battery management device according to claim 2 or 4, wherein the virtual voltage calculation unit calculates a representative internal resistance of the battery pack using the current flowing through the battery pack and the calculated virtual representative voltage. Claim 7 A battery management device according to claim 2 or 4, wherein the virtual voltage calculation unit calculates the internal resistance of the battery cell with the largest internal resistance among the battery cells as the representative internal resistance of the battery pack. Claim 8 delete Claim 9 A battery management method comprising: a step of calculating a virtual representative voltage by measuring the terminal voltage of each of a plurality of battery cells constituting a battery pack; and a step of calculating a current limit value to prevent the plurality of battery cells from exceeding an operating voltage using the virtual representative voltage, the current flowing through the battery pack, and the calculated representative internal resistance of the battery pack; wherein, when the battery pack is charged, the virtual representative voltage calculated in the step of calculating the virtual representative voltage is calculated by adding the terminal voltage of the battery cell with the highest terminal voltage at the previous measurement time among the battery cells to the terminal voltage change of the battery cell with the largest terminal voltage change from the previous measurement time to the current measurement time among the battery cells. Claim 10 In claim 9, the virtual representative voltage calculated in the step of calculating the virtual representative voltage is a battery management method calculated through the following mathematical formula 3 when the battery pack is charged.[Mathematical Formula 3] (Here, V k,vir CHA is the current measurement time t when the above battery pack is being charged k The above-mentioned virtual representative voltage at, and V k-1,max is the previous measurement point t k-1 In the above battery cells, it is the terminal voltage of the battery cell with the highest terminal voltage, and ΔV CHA is the change in terminal voltage of the battery cell with the largest change in terminal voltage among the battery cells when the battery pack is charged.) Claim 11 A battery management method comprising: a step of calculating a virtual representative voltage by measuring the terminal voltage of each of a plurality of battery cells constituting a battery pack; and a step of calculating a current limit value to prevent the plurality of battery cells from exceeding an operating voltage using the virtual representative voltage, the current flowing through the battery pack, and the calculated representative internal resistance of the battery pack; wherein, when the battery pack is discharged, the virtual representative voltage calculated in the step of calculating the virtual representative voltage is calculated by adding the terminal voltage of the battery cell with the lowest terminal voltage at the previous measurement time among the battery cells to the terminal voltage change amount of the battery cell with the largest terminal voltage change amount from the previous measurement time to the current measurement time among the battery cells, wherein the terminal voltage change amount is a value less than 0. Claim 12 In claim 11, the virtual representative voltage calculated in the step of calculating the virtual representative voltage is a battery management method calculated through the following mathematical formula 4 when the battery pack is discharged. [Mathematical Formula 4] (Here, V k,vir DCH is the current measurement time t when the above battery pack is discharged k The above-mentioned virtual representative voltage at, and V k-1,min is the previous measurement point t k-1 In the above battery cells, it is the terminal voltage of the battery cell with the lowest terminal voltage, and ΔV DCH is the change in terminal voltage of the battery cell with the largest change in terminal voltage among the battery cells when the battery pack is discharged.) Claim 13 A battery management method according to claim 9 or 11, further comprising the step of calculating a representative internal resistance of the battery pack after the step of calculating the virtual representative voltage, wherein the representative internal resistance is calculated using the current flowing through the battery pack and the calculated virtual representative voltage. Claim 14 A battery management method according to claim 9 or 11, further comprising the step of calculating a representative internal resistance of the battery pack after the step of calculating the virtual representative voltage, wherein the representative internal resistance is calculated as the internal resistance of the battery cell having the largest internal resistance among the battery cells.

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