Battery charge state estimation device and method

Abstract

To provide a battery charge state estimation device and a method for protecting a battery from overcharge / overdischarge in charge / discharge of a battery rack constituted of many cells.SOLUTION: The present invention relates to a battery charge state estimation device and a method. The battery charge state estimation device includes a memory, and a processor which is coupled with the memory, wherein the processor calculates the maximum SOC of the maximum voltage cell and the minimum SOC of the minimum voltage cell in charge / discharge of a battery rack including a plurality of cells, and calculates a representative SOC of the battery rack on the basis of the maximum SOC and the minimum SOC.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an apparatus and method for estimating a state of charge of a battery, and more particularly to an apparatus and method for estimating a state of charge of a battery that can protect a battery from overcharging / over-discharging when charging / discharging a battery rack composed of a large number of cells. [Background technology]

[0002] As environmental destruction and resource depletion have been raised as serious issues, interest in energy storage systems (ESS) that can store energy and use it efficiently is growing. Energy storage systems consist of battery racks with dozens to hundreds of cells connected in series or parallel.

[0003] A method for controlling the charging / discharging of the many cells that make up such a battery rack involves calculating the average State of Charge (SOC) of the many cells included in the battery rack and then charging / discharging the cells based on that average.

[0004] However, if the average SOC of a number of cells included in a battery rack is used as the basis for charging / discharging, a problem may arise in which the charging / discharging state of the cells varies.

[0005] In addition, when SOC is calculated based on the average voltage of all cells, there is a risk of overcharging at the time of full charge and over-discharging at the time of full discharge due to the presence of an error from the available capacity of the actual battery rack. Specifically, cells with a higher than average SOC will be charged (overcharged) more than necessary, and cells with a lower than average SOC will be discharged (over-discharged) more than necessary, causing some cells to continue intermittent charging / discharging at the upper / lower limit of the Depth of Discharge (DOD), which acts as a major factor in cell degradation and leads to problems that reduce battery performance.

[0006] The background art of the present invention is disclosed in Korean Patent Publication No. 10-1467363. Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide an apparatus and method for estimating a state of charge of a battery that can protect the battery from overcharging / over-discharging during charging / discharging of a battery rack composed of a large number of cells. [Means for solving the problem]

[0008] A battery charge state estimating device according to some embodiments of the present invention includes a memory and a processor connected to the memory, and the processor calculates a maximum SOC of a maximum voltage cell and a minimum SOC of a minimum voltage cell when charging / discharging a battery rack including a plurality of cells, and calculates a representative SOC of the battery rack based on the maximum SOC and minimum SOC.

[0009] In some embodiments of the present invention, the processor calculates a maximum SOC based on the voltage and current of a maximum voltage cell having the highest voltage among the voltages of the plurality of cells when charging / discharging the battery rack, and calculates a minimum SOC based on the voltage and current of a minimum voltage cell having the lowest voltage among the voltages of the plurality of cells.

[0010] In some embodiments of the present invention, the processor calculates a first weighted value for the maximum SOC and a second weighted value for the minimum SOC based on a battery operating range, an average SOC and a deviation SOC of the maximum SOC and minimum SOC, and calculates the representative SOC by applying the first weighted value and the second weighted value to the maximum SOC and minimum SOC.

[0011] In some embodiments of the present invention, the processor calculates a second SOC upper limit value and a second SOC lower limit value by applying the differential SOC to a first SOC upper limit value and a first SOC lower limit value, which are the battery operating range, and calculates a first weighted value for the maximum SOC and a second weighted value for the minimum SOC based on the second SOC upper limit value, the second SOC lower limit value and an average SOC, respectively.

[0012] In some embodiments of the present invention, the processor calculates the second SOC upper limit value by subtracting a certain percentage of the differential SOC from the first SOC upper limit value, and calculates the second SOC lower limit value by adding a certain percentage of the differential SOC to the first SOC lower limit value.

[0013] In some embodiments of the present invention, the processor calculates the second weighting value by dividing a value obtained by subtracting an average SOC from the second SOC upper limit value by a value obtained by subtracting a second SOC lower limit value from the second SOC upper limit value, and calculates the first weighting value by subtracting the second weighting value from 1.

[0014] A method for estimating a battery state of charge according to some embodiments of the present invention includes a step of a processor receiving measurement data of each cell from a sensor when charging / discharging a battery rack including a plurality of cells, a step of the processor calculating a maximum SOC of a maximum voltage cell and a minimum SOC of a minimum voltage cell based on the measurement data of each cell, and a step of the processor calculating a representative SOC of the battery rack based on the maximum SOC and minimum SOC.

[0015] In some embodiments of the present invention, in the step of calculating the maximum SOC of the maximum voltage cell and the minimum SOC of the minimum voltage cell, the processor calculates the maximum SOC based on the voltage and current of a maximum voltage cell having the highest voltage among the voltages of the multiple cells, and calculates the minimum SOC based on the voltage and current of a minimum voltage cell having the lowest voltage among the voltages of the multiple cells.

[0016] In some embodiments of the present invention, the step of calculating a representative SOC of the battery rack includes the steps of: the processor calculating an average SOC and a deviation SOC of a maximum SOC and a minimum SOC; the processor calculating a second upper SOC limit value and a second SOC lower limit value by applying the deviation SOC to a first SOC upper limit value and a first SOC lower limit value, which are a battery operating range; the processor calculating a first weighted value for a maximum SOC and a second weighted value for a minimum SOC based on the second SOC upper limit value, the second SOC lower limit value and the average SOC; and the processor calculating the representative SOC of the battery rack by applying the first weighted value and the second weighted value to the maximum SOC and minimum SOC.

[0017] In some embodiments of the present invention, in the step of calculating the second SOC lower limit value, the processor calculates the second SOC upper limit value by subtracting a certain percentage of the differential SOC from the first SOC upper limit value, and calculates the second SOC lower limit value by adding a certain percentage of the differential SOC to the first SOC lower limit value.

[0018] In some embodiments of the present invention, in the step of calculating the second weight value, the processor calculates the second weight value by dividing a value obtained by subtracting an average SOC from the second SOC upper limit value by a value obtained by subtracting a second SOC lower limit value from the second SOC upper limit value, and calculates the first weight value by subtracting the second weight value from 1. Effect of the Invention

[0019] The battery charge state estimation device and method of the present invention calculates a representative SOC of the battery rack based on the maximum SOC of the maximum voltage cell and the minimum SOC of the minimum voltage cell when charging / discharging a battery rack containing multiple cells, which not only protects the battery from overcharging / over-discharging, but also enables the SOC to be calculated while minimizing resources. [Brief description of the drawings]

[0020] [Figure 1] 1 is a block diagram showing a schematic configuration of a battery charge state estimation system according to an embodiment of the present invention; [Diagram 2] 1 is a block diagram showing a schematic configuration of a battery charge state estimating device according to an embodiment of the present invention; [Diagram 3] 4 is a flowchart illustrating a method for calculating a representative SOC of a battery rack according to an embodiment of the present invention. [Figure 4] FIG. 2 is an exemplary diagram for comparing a representative SOC calculation method according to an embodiment of the present invention with a conventional SOC calculation method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment of a battery charge state estimation device and method according to the present invention will be described with reference to the accompanying drawings. In this process, the thickness of lines and the size of components shown in the drawings may be exaggerated for clarity and convenience of explanation. In addition, the terms described below are defined in consideration of the functions in the present invention, and may differ depending on the intention or practice of a user or operator. Therefore, the definitions of such terms should be determined based on the overall content of this specification.

[0022] FIG. 1 is a block diagram showing a schematic configuration of a battery charge state estimation system according to an embodiment of the present invention.

[0023] Referring to FIG. 1, a battery state of charge (SOC) estimation system according to an embodiment of the present invention includes a battery rack 100, a sensor 200, and a battery state of charge estimation device 300.

[0024] The battery rack 100 has a configuration in which a number of battery cells are arranged in series to be configured as one package. In the battery rack 100, a first battery cell, a second battery cell to an n-th battery cell may be arranged in series. Of course, although the present invention has been described as a case in which a number of battery cells are connected in series, the present invention is not limited thereto, and unit battery cells may be configured in series and / or in parallel.

[0025] The type of battery cell is not particularly limited, and may be a lithium ion battery, a lithium polymer battery, a nickel cadmium battery, a nickel metal hydride battery, a nickel zinc battery, or the like that can be repeatedly charged and discharged.

[0026] The sensor 200 can measure the current and voltage of each cell at a predetermined periodic interval while a number of cells constituting the battery rack 100 are being charged / discharged, and transmit the measured measurement data of each cell to the battery state of charge estimation device 300. Here, the measurement data can include the current, voltage, etc. of each cell.

[0027] Such a sensor 200 includes a voltage sensor (not shown) and a current sensor (not shown) for measuring the voltage and current of each cell, and can measure the current and voltage of each cell during charging / discharging at predetermined periodic intervals.

[0028] The battery state of charge estimation device 300 can calculate a representative SOC of the battery rack 100 based on the measurement data of each cell measured by the sensor 200. The representative SOC of the battery rack 100 is a parameter indicating the state of charge of the battery rack 100, and can be a value representative of the SOC of the battery rack 100 including the cells.

[0029] The battery charge state estimation device 300 may be implemented as a device for estimating the state of a battery, using a software module, a hardware module, or a combination thereof. For example, the battery charge state estimation device 300 may be implemented by a Battery Management System (BMS). The BMS is a system for managing a battery, and may, for example, monitor the state of the battery, maintain an optimized condition for the operation of the battery, predict when to replace the battery, detect problems with the battery, and generate a control or command signal related to the battery to control the state or operation of the battery.

[0030] For a detailed description of the battery state of charge estimating device 300, please refer to FIG.

[0031] FIG. 2 is a block diagram showing a schematic configuration of a battery charge state estimating device according to an embodiment of the present invention.

[0032] Referring to FIG. 2, a battery state of charge estimating apparatus 300 according to an embodiment of the present invention includes a memory 310 and a processor 320.

[0033] The memory 310 is configured to store data related to the operation of the battery state of charge estimation device 300. In particular, the memory 310 may store an application (program or applet) that calculates the maximum SOC of the maximum voltage cell and the minimum SOC of the minimum voltage cell when charging / discharging the battery rack 100 including a plurality of cells, and calculates a representative SOC of the battery rack 100 based on the maximum SOC and the minimum SOC, and the stored information may be selected by the processor 320 as necessary. That is, the memory 310 stores various types of data generated during the execution of an operating system for driving the battery state of charge estimation device 300 and a control application (program or applet). In addition, the memory 310 may store a first SOC upper limit value and a first SOC lower limit value, which are the battery operating range, measurement data of each cell, and the like. The memory 310 may include a magnetic storage medium or a flash storage medium in addition to a volatile storage device that requires power to maintain the stored information, but the scope of the present invention is not limited thereto.

[0034] When charging / discharging the battery rack 100 including multiple cells, the processor 320 can calculate the maximum SOC of the highest voltage cell and the minimum SOC of the lowest voltage cell, and calculate a representative SOC of the battery rack 100 based on the maximum SOC and minimum SOC.

[0035] The operation of the processor 320 will now be described in detail.

[0036] The processor 320 may receive measurement data of each cell from the sensor 200 at regular intervals while a number of cells included in the battery rack 100 are simultaneously being charged / discharged. Here, the measurement data may include the voltage and current of each cell.

[0037] When the measurement data of each cell is received, the processor 320 may calculate the maximum SOC of the maximum voltage cell and the minimum SOC of the minimum voltage cell. In this case, the processor 320 may calculate the maximum SOC based on the voltage and current of the maximum voltage cell having the highest voltage among the voltages of the cells. The processor 320 may also calculate the minimum SOC based on the voltage and current of the minimum voltage cell having the lowest voltage among the voltages of the cells. The SOC is a parameter indicating the state of charge and indicates the amount of energy stored in the corresponding cell, and may be expressed in percentages (%) from 0 to 100%. For example, 0% may mean a fully discharged state and 100% may mean a fully charged state, but such an expression method may be defined in various modified forms according to the design intent and embodiments.

[0038] When the maximum SOC and the minimum SOC are calculated, the processor 320 may calculate an average SOC and a deviation SOC of the maximum SOC and the minimum SOC. In this case, the processor 320 may calculate the average SOC using the following Equation 1 and calculate the deviation SOC using Equation 2.

[0039] [Formula 1] Average SOC=(Maximum SOC+Minimum SOC) / 2

[0040] [Formula 2] Deviation SOC = Maximum SOC - Minimum SOC

[0041] Thereafter, the processor 320 may calculate a second SOC upper limit value and a second SOC lower limit value by applying the difference SOC to the first SOC upper limit value and the first SOC lower limit value, which are the battery operating range. Here, the first SOC upper limit value and the first SOC lower limit value, which are the battery operating range, may mean a preset operating limit range. In this case, the processor 320 may calculate the second SOC upper limit value by subtracting a certain percentage of the difference SOC from the first SOC upper limit value, and may calculate the second SOC lower limit value by adding a certain percentage of the difference SOC to the first SOC lower limit value. For example, the processor 320 may calculate the second SOC upper limit value and the second SOC lower limit value by adding or subtracting only 1 / 2 of the difference SOC from the first SOC upper limit value and the first SOC lower limit value, which are the battery operating range. That is, the processor 320 may calculate the second SOC upper limit value using the following Equation 3, and may calculate the second SOC lower limit value using Equation 4.

[0042] [Formula 3] Second SOC upper limit = First SOC upper limit - (deviation SOC / 2)

[0043] [Formula 4] Second SOC lower limit = First SOC lower limit + (deviation SOC / 2)

[0044] After the second SOC upper limit value and the second SOC lower limit value are calculated, the processor 320 may calculate a first weighted value of the maximum SOC and a second weighted value of the minimum SOC based on the second SOC upper limit value, the second SOC lower limit value, and the average SOC. In this case, the processor 320 may calculate the second weighted value of the minimum SOC and the first weighted value of the maximum SOC by adding or subtracting the average SOC from the second SOC upper limit value and the second SOC lower limit value. That is, the processor 320 may calculate the second weighted value using the following Equation 5 and calculate the first weighted value using Equation 6.

[0045] [Formula 5] Second weighted value = (Second upper SOC limit - average SOC) / (Second upper SOC limit - Second lower SOC limit)

[0046] [Formula 6] 1st weight = 1 - 2nd weight

[0047] After the first weighted value and the second weighted value are calculated, the processor 320 may apply the first weighted value and the second weighted value to the maximum SOC and the minimum SOC to calculate the representative SOC of the battery rack 100. In this case, the processor 320 may calculate the representative SOC of the battery rack 100 using the following Equation 7.

[0048] [Formula 7] Representative SOC = 1st weighted value * Maximum SOC + 2nd weighted value * Minimum SOC

[0049] The processor 320 controls the overall operation of the battery state of charge estimation device 300 and may be implemented as an integrated circuit, a system-on-chip, or a mobile AP.

[0050] The processor 320 may control the overall operation state of the battery state of charge estimation device 300. The processor 320 may refer to a data processing device built into hardware having a circuit physically structured to perform a function expressed by a code or instruction included in a program, for example. As such, examples of the data processing device built into hardware may include processing devices such as a microprocessor, a central processing unit (CPU), a processor core, a multiprocessor, an application-specific integrated circuit (ASIC), and a field programmable gate array (FPGA), but the scope of the present invention is not limited thereto.

[0051] FIG. 3 is a flowchart for explaining a representative SOC calculation method of a battery rack 100 according to one embodiment of the present invention, and FIG. 4 is an illustrative diagram for comparing the representative SOC calculation method according to one embodiment of the present invention with a conventional SOC calculation method.

[0052] 3, when multiple cells included in the battery rack 100 are simultaneously charging / discharging (S302), the processor 320 receives measurement data of each cell from the sensor 200 at regular intervals (S304). Here, the measurement data may include the voltage and current of each cell.

[0053] After step S304 is performed, the processor 320 calculates the maximum SOC of the maximum voltage cell and the minimum SOC of the minimum voltage cell based on the measurement data of each cell (S306). At this time, the processor 320 may calculate the maximum SOC based on the voltage and current of the maximum voltage cell having the highest voltage among the voltages of the cells. The processor 320 may also calculate the minimum SOC based on the voltage and current of the minimum voltage cell having the lowest voltage among the voltages of the cells.

[0054] After step S306 is performed, the processor 320 calculates an average SOC and a deviation SOC of the maximum SOC and the minimum SOC (S308). In this case, the processor 320 may calculate the average value of the maximum SOC and the minimum SOC as the average SOC. The processor 320 may also calculate the difference between the maximum SOC and the minimum SOC as the deviation SOC.

[0055] After step S308 is performed, the processor 320 calculates a second SOC upper limit value and a second SOC lower limit value by applying the differential SOC to the first SOC upper limit value and the first SOC lower limit value, which are the battery operating range (S310). At this time, the processor 320 may calculate the second SOC upper limit value by subtracting 1 / 2 of the differential SOC from the first SOC upper limit value, which is the battery operating range. Also, the processor 320 may calculate the second SOC lower limit value by adding 1 / 2 of the differential SOC to the first SOC lower limit value, which is the battery operating range.

[0056] After step S310 is performed, processor 320 calculates a first weighted value of maximum SOC and a second weighted value of minimum SOC based on the second upper limit SOC, the second lower limit SOC, and the average SOC (S312). In this case, processor 320 may calculate the second weighted value by dividing a value obtained by subtracting the average SOC from the second upper limit SOC by a value obtained by subtracting the second lower limit SOC from the second upper limit SOC. Processor 320 may also calculate the first weighted value by subtracting the second weighted value from 1.

[0057] After step S312 is performed, the processor 320 applies the first weighting value and the second weighting value to the maximum SOC and the minimum SOC to calculate a representative SOC of the battery rack 100 (S314). In this case, the processor 320 may calculate the representative SOC by adding a value obtained by multiplying the maximum SOC by the first weighting value and a value obtained by multiplying the minimum SOC by the second weighting value.

[0058] For example, a method for calculating the representative SOC when the first SOC upper limit value is 100%, the first SOC lower limit value is 0%, the maximum SOC of the maximum voltage cell is 90%, and the minimum SOC of the minimum voltage cell is 70% will be described.

[0059] First, the processor 320 may calculate an average SOC of 80%, which is the average value of the maximum SOC of 90% and the minimum SOC of 70%, and may calculate a deviation SOC of 20%, which is the difference between the maximum SOC of 90% and the minimum SOC of 70%.

[0060] Then, processor 320 calculates a second SOC upper limit value of 90% by subtracting 1 / 2 of the deviation SOC 20% from the first SOC upper limit value of 100% (100%-(20% / 2)), and calculates a second SOC lower limit value of 10% by adding 1 / 2 of the deviation SOC 20% to the first SOC lower limit value of 0% (0%+(20% / 2)).

[0061] Then, the processor 320 may calculate the second weighting value as (second SOC upper limit 90% - average SOC 80%) / (second SOC upper limit 90% - second SOC lower limit 10%) = 0.125, and calculate the first weighting value as (1 - second weighting value 0.125) = 0.875.

[0062] The processor 320 may then calculate the representative SOC as ((first weighting value 0.875 * maximum SOC 90%) + (second weighting value 0.125 * minimum SOC 70%)) = 87.5%.

[0063] As described above, the present invention can protect the battery from the risk of overcharging / overdischarging by calculating the representative SOC of the battery rack 100 based on the maximum SOC of the maximum voltage cell and the minimum SOC of the minimum voltage cell when charging / discharging the battery rack 100 including a plurality of cells. For example, referring to Fig. 4, the representative SOC of the battery rack 100 at the time of full charge (SOC 100%) is 100% and there is no risk of overcharging, but when the SOC is calculated based on the average voltage of all the cells at the time of full charge (SOC 100%), there may be a risk of overcharging the SOC to 105%.

[0064] The device and method for estimating a battery state of charge according to the present invention calculates a representative SOC of the battery rack based on the maximum SOC of the maximum voltage cell and the minimum SOC of the minimum voltage cell when charging / discharging a battery rack containing multiple cells, thereby not only protecting the battery from overcharging / over-discharging but also enabling the SOC to be calculated while minimizing resources.

[0065] The present invention has been described with reference to the embodiments shown in the drawings, but it is understood that these are merely illustrative and that those skilled in the art will recognize that various modifications and equivalent embodiments are possible. Therefore, the technical scope of the present invention should be determined by the following claims.

Claims

1. memory; and a processor coupled to the memory, The processor, A battery charge state estimation device characterized in that, when charging / discharging a battery rack including a plurality of cells, a maximum SOC of a maximum voltage cell and a minimum SOC of a minimum voltage cell are calculated, and a representative SOC of the battery rack is calculated based on the maximum SOC and the minimum SOC.

2. The processor, 2. The battery charge state estimation device according to claim 1, wherein, when charging / discharging the battery rack, the maximum SOC is calculated based on a voltage and a current of the maximum voltage cell having the highest voltage among the voltages of the plurality of cells, and the minimum SOC is calculated based on a voltage and a current of the minimum voltage cell having the lowest voltage among the voltages of the plurality of cells.

3. The processor, 2. The device for estimating a state of charge of a battery according to claim 1, further comprising: a first weighted value for the maximum SOC and a second weighted value for the minimum SOC based on a battery operating range, an average SOC and a deviation SOC of the maximum SOC and the minimum SOC; and a representative SOC is calculated by applying the first weighted value and the second weighted value to the maximum SOC and the minimum SOC.

4. The processor, 4. The device for estimating a state of charge of a battery according to claim 3, further comprising: a first SOC upper limit value and a first SOC lower limit value, which are the battery operating range, to calculate a second SOC upper limit value and a second SOC lower limit value; and a first weighted value for the maximum SOC and a second weighted value for the minimum SOC, based on the second SOC upper limit value, the second SOC lower limit value and the average SOC.

5. The processor, 5. The battery charge state estimating device according to claim 4, wherein the second SOC upper limit value is calculated by subtracting a fixed percentage of the deviation SOC from the first SOC upper limit value, and the second SOC lower limit value is calculated by adding the fixed percentage of the deviation SOC to the first SOC lower limit value.

6. The processor, 5. The battery charge state estimating device according to claim 4, wherein the second weighting value is calculated by dividing a value obtained by subtracting the average SOC from the second SOC upper limit value by a value obtained by subtracting the second SOC lower limit value from the second SOC upper limit value, and the first weighting value is calculated by subtracting the second weighting value from 1.

7. receiving measurement data for each cell from a sensor when a battery rack including a plurality of cells is charged / discharged by a processor; the processor calculating a maximum SOC for a maximum voltage cell and a minimum SOC for a minimum voltage cell based on the measurement data for each cell; and the processor calculating a representative SOC of the battery rack based on the maximum SOC and the minimum SOC. A method for estimating a battery state of charge, comprising:

8. In the step of calculating the maximum SOC of the maximum voltage cell and the minimum SOC of the minimum voltage cell, 8. The method of claim 7, wherein the processor calculates the maximum SOC based on a voltage and a current of the maximum voltage cell having the highest voltage among the voltages of the plurality of cells, and calculates the minimum SOC based on a voltage and a current of the minimum voltage cell having the lowest voltage among the voltages of the plurality of cells.

9. The step of calculating the representative SOC of the battery rack includes: said processor calculating an average SOC and a deviation SOC of said maximum SOC and said minimum SOC; the processor applies the difference SOC to a first SOC upper limit value and a first SOC lower limit value that are within a battery operating range to calculate a second SOC upper limit value and a second SOC lower limit value; calculating a first weighted value of the maximum SOC and a second weighted value of the minimum SOC based on the second upper SOC limit value, the second lower SOC limit value, and the average SOC; and 8. The method of claim 7, further comprising: calculating the representative SOC of the battery rack by applying the first weighting value and the second weighting value to the maximum SOC and the minimum SOC.

10. In the step of calculating the second SOC lower limit value, 10. The method of estimating a battery state of charge according to claim 9, wherein the processor calculates the second SOC upper limit value by subtracting a certain percentage of the deviation SOC from the first SOC upper limit value, and calculates the second SOC lower limit value by adding the certain percentage of the deviation SOC to the first SOC lower limit value.

11. In the step of calculating the second weight value, 10. The method of claim 9, wherein the processor calculates the second weighting value by dividing a value obtained by subtracting the average SOC from the second SOC upper limit value by a value obtained by subtracting the second SOC lower limit value from the second SOC upper limit value, and calculates the first weighting value by subtracting the second weighting value from 1.

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