Battery charging state estimation device based on coulomb counter

Abstract

The present invention relates to a battery state-of-charge estimation device, comprising: a first coulomb counter that accumulates a battery current Im for each predetermined period and calculates a first charge change amount [Delta] Q for each period; a second coulomb counter that accumulates the first charge change amount [Delta] Q to calculate a first predicted charge amount Qe; a compensator that calculates a second charge change amount [Delta] Qcomp by compensating the first charge change amount [Delta] Q using the first predicted charge amount Qm and the second predicted charge amount Qe; a third coulomb counter that accumulates the second charge change amount [Delta] Qcomp to calculate a second predicted charge amount Qe; and a state-of-charge estimator that estimates the state of charge of the battery on the basis of the second predicted charge amount Qe. According to the present invention, in battery state-of-charge estimation based on a coulomb counter, a state-of-charge estimation error caused by error accumulation of current detection can be reduced, and characteristics caused by battery temperature and aging can be compensated to improve the accuracy of state-of-charge estimation.

Description

Technical Field

[0001] This application claims priority to Korean Patent Application No. 10-2024-0194631, filed on December 23, 2024, the entire contents of which are incorporated herein by reference for all relevant purposes. Background Technology

[0002] This invention relates to a battery state-of-charge estimation device based on a coulomb counter. Specifically, the invention relates to a battery state-of-charge estimation device that can reduce the state-of-charge estimation error caused by the accumulation of errors in current detection in coulomb counter-based battery state-of-charge estimation, and improve the accuracy of state-of-charge estimation by compensating for characteristics caused by battery temperature and aging.

[0003] Coulomb counter-based techniques are widely used to estimate the state of charge (SOC) of batteries. This technique detects the battery current and accumulates the detected currents to estimate the battery's charge, and then uses this estimated charge to determine the SOC. Also known as the current accumulation method, this coulomb counter-based SOC estimation technique is widely used due to its advantage of providing a relatively accurate and simple method for SOC estimation.

[0004] However, conventional battery state-of-charge estimation techniques based on coulomb counters predict the remaining charge of a battery by continuously summing the measured currents. Even if there are some errors in the process of measuring the current, these errors will accumulate and may lead to larger errors in the prediction of the remaining charge of the battery over time.

[0005] Furthermore, conventional coulomb counter-based battery state-of-charge (SOC) estimation techniques do not reflect changes in battery characteristics due to temperature and aging, thus leaving room for improvement. For example, if a battery is at low temperatures or aging, its full-charge capacity (or usable capacity) may be significantly reduced compared to its design capacity. When this reduction in full-charge capacity is not reflected, the accuracy of SOC estimation decreases.

[0006] Existing technical documents

[0007] Patent documents

[0008] (Patent Document 1) Korean Patent Publication No. 10-2021-0137763 (Publication Date: November 18, 2021)

[0009] (Patent Document 2) Japanese Patent Publication No. 2015-224975 (Publication Date: December 14, 2015)

[0010] (Patent Document 3) Japanese Patent Publication No. 2009-109269 (Publication Date: May 21, 2009) Summary of the Invention

[0011] According to embodiments, the present invention aims to improve the problem of decreased accuracy of state of charge estimation in battery state of charge estimation due to the accumulation of errors such as current measurement in coulomb counter-based estimation.

[0012] According to embodiments, the present invention aims to improve the accuracy of state of charge estimation by reflecting changes in battery characteristics due to battery temperature and aging in the battery state of charge estimation based on a coulomb counter.

[0013] According to embodiments, the present invention aims to estimate the state of charge of a battery based on the changes in full charge capacity due to battery temperature and aging in a coulomb counter-based battery state of charge estimation.

[0014] According to embodiments, the present invention aims to simplify the structure and reduce the power consumption used for state of charge estimation in battery state-of-charge estimation based on coulomb counters.

[0015] A battery state-of-charge estimation apparatus according to the present invention, for solving the above-mentioned technical problems, comprises: a first coulomb counter, which accumulates the battery current Im in each predetermined period to calculate a first charge change ΔQ corresponding to each period; a second coulomb counter, which accumulates the first charge change ΔQ to calculate a first predicted charge Qm; a compensator, which uses the first predicted charge Qm and a second predicted charge Qe to compensate for the first charge change ΔQ to calculate a second charge change ΔQ_comp; a third coulomb counter, which accumulates the second charge change ΔQ_comp to calculate the second predicted charge Qe; and a state-of-charge estimator, which estimates the state of charge of the battery based on the second predicted charge Qe.

[0016] According to the battery state of charge estimation apparatus of the present invention, the compensator uses the second predicted charge quantity Qe to calculate the predicted open-circuit voltage OCVe, and uses the predicted open-circuit voltage OCVe to calculate the second charge change ΔQ_comp.

[0017] According to the battery state of charge estimation apparatus of the present invention, when calculating the predicted open-circuit voltage OCVe using the second predicted charge Qe, the compensator uses a first lookup table containing data relating the open-circuit voltage OCV and the charge Q of the battery.

[0018] According to the battery state of charge estimation device of the present invention, when the magnitude of the battery current Im is less than a first threshold, the compensator compensates for the first charge change ΔQ in order to reduce the difference between the predicted open-circuit voltage OCVe and the battery terminal voltage Vm, thereby calculating the second charge change ΔQ_comp.

[0019] According to the battery state of charge estimation apparatus of the present invention, the compensator calculates the second charge change ΔQ_comp based on the value obtained by multiplying the predicted open-circuit voltage OCVe by a first constant C1 from the value obtained by subtracting the predicted open-circuit voltage OCVe from the battery terminal voltage Vm.

[0020] According to the battery state of charge estimation device of the present invention, the first constant C1 is predetermined based on the internal resistance value of the battery.

[0021] According to the battery state of charge estimation apparatus of the present invention, the compensator calculates a charge change compensation coefficient COMP_RATE based on the ratio of the voltage-based remaining prediction time RTV calculated according to the battery terminal voltage Vm to the charge-based remaining prediction time RTQ calculated according to the second predicted charge Qe, and multiplies the charge change compensation coefficient COMP_RATE by the first charge change ΔQ to calculate the second charge change ΔQ_comp.

[0022] According to the battery state of charge estimation apparatus of the present invention, the remaining prediction time RTQ based on charge quantity is the time required for the current remaining capacity of the battery to reach 0 under the discharge conditions of the battery.

[0023] According to the battery state of charge estimation apparatus of the present invention, the remaining prediction time RTQ based on charge is calculated based on the absolute value of the product of the second predicted charge Qe and the battery current Im and the charge change compensation coefficient COMP_RATE.

[0024] According to the battery state of charge estimation apparatus of the present invention, the voltage-based remaining prediction time RTV is the time required for the current battery voltage Vm to reach the termination voltage Vterm under the discharge conditions of the battery.

[0025] According to the battery state of charge estimation apparatus of the present invention, the voltage-based remaining prediction time RTV is calculated by multiplying the value obtained by subtracting the battery voltage Vm from the termination voltage Vterm by the inverse of the slope of the opening voltage OCVm, ΔT / ΔOCVm.

[0026] According to the battery state of charge estimation apparatus of the present invention, the compensator linearizes the discontinuous components of the voltage-based remaining prediction time RTV to generate a remaining prediction time RTV_1st based on a first correction voltage.

[0027] According to the battery state of charge estimation apparatus of the present invention, the compensator corrects the remaining prediction time RTV_1st based on the primary correction voltage according to the characteristic differences caused by the discharge current and battery temperature, so as to generate the remaining prediction time RTV_2nd based on the secondary correction voltage.

[0028] According to the present invention, and according to embodiments, the problem of decreased accuracy of state-of-charge estimation due to the accumulation of errors such as current measurement in battery state-of-charge estimation based on coulomb counters can be improved.

[0029] According to the present invention, and according to embodiments, the accuracy of state of charge estimation can be improved by reflecting changes in battery characteristics due to battery temperature and aging in the coulomb counter-based battery state of charge estimation.

[0030] According to the present invention, and according to an embodiment, the state of charge of a battery can be estimated based on the full charge capacity, which varies due to battery temperature and aging, in a coulomb counter-based battery state of charge estimation.

[0031] According to one embodiment of the present invention, the structure can be simplified and the power consumption used for state of charge estimation can be reduced in battery state of charge estimation based on a coulomb counter. Attached Figure Description

[0032] Figure 1 A battery state-of-charge estimation device according to an embodiment of the present invention is shown.

[0033] Figure 2 This is an example diagram illustrating the overall structure of the charge change compensation coefficient COMP_RATE calculated by the ratio of the remaining prediction time RTQ based on charge quantity to the remaining prediction time RTV based on voltage quantity, according to one embodiment of the present invention.

[0034] Figure 3 This is an example illustration of a diagram showing the configuration of calculating RTV using the termination voltage Vterm, battery voltage Vm, and open-circuit voltage OCVm, according to an embodiment of the present invention.

[0035] Figure 4 This is an example illustration of an uncorrected RTV according to one embodiment of the present invention.

[0036] Figure 5This is a diagram conceptually illustrating a single correction for converting RTV to RTV_ref according to one embodiment of the present invention.

[0037] Figure 6 This is an embodiment of the present invention, which exemplarily illustrates a flowchart of an RTV single-pass calibration.

[0038] Figure 7 The figure illustrates, by way of example, the simulation results of a single RTV correction performed under discharge conditions of 25°C and -0.02C, according to one embodiment of the present invention.

[0039] Figure 8 According to one embodiment of the present invention, a graph is provided exemplarily showing the voltage characteristics at different temperatures under a discharge current of -0.8A.

[0040] Figure 9 This is an example illustration of the voltage characteristics corresponding to different discharge currents under a temperature condition of 25°C, according to one embodiment of the present invention.

[0041] Figure 10 This is an example illustration of a graph showing the first correction result of the voltage curve under conditions of 25°C and -0.8A, according to one embodiment of the present invention.

[0042] Figure 11 According to one embodiment of the present invention, an exemplary graph is shown showing the first correction result of the voltage curve under the conditions of -10°C and -0.8A.

[0043] Figure 12 According to one embodiment of the present invention, an exemplary flowchart of RTV secondary correction is shown.

[0044] Figure 13 This is an example illustration of simulation results of RTV primary and secondary corrections performed under discharge conditions of 25°C and -0.8A, according to one embodiment of the present invention.

[0045] Figure 14 This is an example of a simulation result of the first and second RTV corrections performed under discharge conditions of -10°C and -0.8A, according to an embodiment of the present invention.

[0046] Figure 15 According to one embodiment of the present invention, an exemplary flowchart for calculating the charge change compensation coefficient COMP_RATE is shown.

[0047] Figures 16 to 19 This is a diagram used to illustrate a comparison between the effects of an embodiment of the present invention and the prior art. Detailed Implementation

[0048] The specific structural or functional descriptions of implementation examples of the inventive concept disclosed in this specification are merely illustrative for the purpose of describing implementation examples based on the inventive concept. Implementation examples based on the inventive concept can be implemented in various forms and should not be construed as being limited to the implementation examples presented in this case.

[0049] Implementations based on the concept of this invention can be modified in various ways and have various forms. Therefore, implementations will be illustrated by way of example in the accompanying drawings and described in detail in this specification. However, this is not intended to limit the implementations based on the concept of this invention to a specific disclosed form, including all modifications, equivalents, and even substitutions contained within the scope of the ideas and techniques of this invention.

[0050] Unless otherwise defined, all terms used in this specification, including technical or scientific terms, shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms identical to those defined in a commonly used dictionary shall be interpreted as having the same meaning as in the context of the prior art, and shall not be construed excessively or overly as having a formal meaning unless explicitly defined in this specification.

[0051] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0052] Figure 1 A battery state of charge estimation device 10 according to an embodiment of the present invention is shown.

[0053] refer to Figure 1 The battery state of charge estimation device 10 may include a first coulomb counter (STCC) 100, a second coulomb calculator (CCM) 200, a compensator 300, a third coulomb counter (SOC Estimator) 500, and a state of charge estimator (SOC Estimator) 500.

[0054] The battery state of charge estimation device 10 can be used to estimate the state of charge of a battery in various devices that use a battery. For example, the battery state of charge estimation device 10 may be highly applicable in portable electronic devices such as mobile phones, tablets, and laptops, but its use is not limited to this. The battery state of charge estimation device 10 can be implemented in various ways, for example, as a separate device in various devices that use a battery, or as a functional element within another device (e.g., a controller) that is already installed in that device.

[0055] The first coulomb counter 100 can calculate the first charge change ΔQ corresponding to each cycle by accumulating the battery current Im in each specified cycle.

[0056] The battery current Im can be a value obtained by detecting the current used to charge or discharge the battery. A conventional current sensing unit can be used to detect the battery current Im. For example, a current sensing resistor or a current transformer can be used, but it is not limited to these. The battery current Im sensing unit can be included in the battery state-of-charge estimation device 10, but the battery state-of-charge estimation device 10 can also obtain battery current Im information from an external battery current Im sensing unit.

[0057] The first coulomb counter 100 can perform a cycle-by-cycle accumulation function for the battery current Im. That is, the first coulomb counter 100 can operate as follows: after calculating the first charge change ΔQ by accumulating the battery current Im in each predetermined cycle, it is initialized (resct), and then the process of accumulating the battery current Im is repeated for the predetermined cycle. For example, the first coulomb counter 100 can calculate the first charge change ΔQ by summing the digitized sampled data of the battery current Im a predetermined number of times. In this case, the value obtained by multiplying the sampling period of the battery current Im by the number of accumulated data points can be understood as the accumulation period of the first coulomb counter 100.

[0058] The reason for performing the cycle-by-cycle accumulation function on the first coulomb counter 100 will be explained. As will be explained in detail later, in this embodiment, after calculating the second charge change ΔQ_comp by compensating the first charge change ΔQ with the compensator 300, the second charge change ΔQ_comp is accumulated in the third coulomb counter 400 to calculate the second predicted charge Qe. When the first coulomb counter 100 is not used, the compensator 300 needs to perform compensation work on each sampled battery current Im. In this case, when noise is included in each sampled battery current Im, the operation of the compensator 300 may not be smooth, and the power consumption may increase with the number of times the compensator 300 operates. In this embodiment, by using the first coulomb counter 100 to accumulate the battery current Im in each predetermined cycle to generate the first charge change ΔQ corresponding to each cycle, the compensator 300 can perform compensation work for the first charge change ΔQ corresponding to each cycle. In this case, since the first charge change ΔQ is the integral of most of the sampled battery current Im values, the influence of noise is reduced, and the operating frequency of the compensator 300 is reduced, thus having the advantage of reduced power consumption.

[0059] At this point, it is preferable to set the accumulation period of the first coulomb counter 100 to a level where the changes in battery states such as battery current Im, battery voltage Vm, and state of charge (SOC) are not significant. This is because if the accumulation period of the first coulomb counter 100 is set too long, resulting in significant changes in battery states, it will be difficult for the compensator 300 to perform appropriate compensation for the first charge change ΔQ due to these changes. For example, when the battery current Im is sampled via an ADC (analog-digital converter) at a period of approximately 0.3 seconds, and the first coulomb counter 100 accumulates 4 to 8 samples of the battery current Im, the accuracy of the state of charge estimation can be improved by appropriately compensating for the first charge change ΔQ while reducing the impact of noise and power consumption.

[0060] The second coulomb counter (CCM) 200 can accumulate the first charge change ΔQ to calculate the first predicted charge Qm. Unlike the third coulomb counter 400, the second coulomb counter 200 can directly accumulate the first charge change ΔQ in the uncompensated state.

[0061] According to an embodiment, the compensator 300 can use a first predicted charge amount Qm and a second predicted charge amount Qe to compensate for a first charge change amount ΔQ, thereby calculating a second charge change amount ΔQ_comp.

[0062] According to an embodiment, the compensator 300 can use the battery current Im, the battery terminal voltage Vm, and the second predicted charge Qe to compensate for the first charge change ΔQ, thereby calculating the second charge change ΔQ_comp.

[0063] According to the embodiment, the compensator 300 uses the second predicted charge amount Qe to calculate the predicted open-circuit voltage OCVe, and uses the predicted open-circuit voltage OCVe to compensate for the first charge change amount ΔQ, thereby the second charge change amount ΔQ_comp can be calculated.

[0064] According to an embodiment, the compensator 300 can calculate the charge change compensation coefficient COMP_RATE based on the ratio of the voltage-based remaining prediction time RTV calculated based on the battery terminal depressurization Vm to the charge-based remaining prediction time RTQ calculated based on the second predicted charge Qe, and multiply the charge change compensation coefficient COMP_RATE by the first charge change ΔQ to calculate the second charge change ΔQ_comp.

[0065] For example, compensator 300 may include a first lookup table (LUT1) 310, a first compensator 320, a second lookup table (LUT2) 330, a second compensator 340, a multiplier 350, and a multiplexer 360.

[0066] The first lookup table (LUT1) 310 may include data on the relationship between the open-circuit voltage OCV and the charge Q of the corresponding battery. The compensator 300 can use the first lookup table 310 and calculate the predicted open-circuit voltage OCVe based on the second predicted charge Qe. The predicted open-circuit voltage OCVe calculated using the first lookup table 310 can be applied to the first compensator 320 and the second compensator 340.

[0067] The first compensator 320 can operate in a manner that eliminates the accumulated error of the second predicted charge Qe when the battery is in a relaxed state.

[0068] Therefore, according to an embodiment, when the battery current Im is less than a first threshold, the first compensator 320 can calculate a second charge change ΔQ_comp to compensate for the first charge change ΔQ by reducing the difference between the predicted open-circuit voltage OCVe and the battery terminal voltage Vm. According to an embodiment, the battery current Im can be the average of the absolute values ​​of the battery current Im during the accumulation period of the first coulomb counter 100, but is not limited thereto. Furthermore, according to an embodiment, the first compensator 320 can be configured to operate only when the determination that the battery current Im is less than the first threshold is sustained for more than a predetermined number of times. The first threshold can be set to a value that indicates the battery is in a certain degree of relaxation.

[0069] When the battery is in a fully relaxed state, the battery terminal voltage Vm can be substantially the same as the actual open-circuit voltage OCV. In this embodiment, since an equivalent model of the battery is not used, an attempt is not made to accurately estimate the actual open-circuit voltage OCV. The predicted open-circuit voltage OCVe in this embodiment is a value simply calculated from the second predicted charge Qe using a lookup table, as described later, based on the premise that there is some degree of difference between the predicted open-circuit voltage OCVe and the actual open-circuit voltage OCV. In this embodiment, under this understanding, when the battery current Im is less than the first threshold, the battery terminal voltage Vm will be more similar to the actual open-circuit voltage OCV than the predicted open-circuit voltage OCVe. Under this assumption, the second charge change ΔQ_comp is calculated by compensating for the first charge change ΔQ in a manner that the predicted open-circuit voltage OCVe follows the battery terminal voltage Vm, thereby eliminating the accumulated error of the second predicted charge Qe.

[0070] If the battery current Im is less than the first threshold for a prolonged period (e.g., several hours), the battery is in a fully relaxed state. Only in this state can the battery terminal voltage Vm be the same as the actual open-circuit voltage OCV. However, in this embodiment, as long as the battery current Im is less than the first threshold, even if a sufficient time has passed, it is assumed that the battery terminal voltage Vm is similar to the actual open-circuit voltage OCV. The system can operate in a way that the predicted open-circuit voltage OCVe follows the battery terminal voltage Vm.

[0071] According to this embodiment, the accumulation error of the second predicted charge Qe during battery operation (even if the battery is not sufficiently relaxed) can be reduced. If the battery is in a sufficiently relaxed state, the error of the second predicted charge Qe is almost completely eliminated automatically by the same algorithm. As described above, according to this embodiment, without using a complex system that accurately estimates the actual open-circuit voltage OCV through a battery equivalent model, the accumulation of the error of the second predicted charge Qe can be prevented by a simple method, thereby improving the accuracy of battery state-of-charge estimation.

[0072] According to an embodiment, as shown in the following mathematical formula 1, the second charge change ΔQ_comp can be calculated by multiplying the value obtained by subtracting the predicted open-circuit voltage OCVe from the battery terminal voltage Vm by the first constant C1.

[0073]

Mathematical Formula 1

[0074] Here, the first constant C1 is a constant that affects the rate at which the predicted open-circuit voltage OCVe follows the battery terminal voltage Vm, and can be determined based on the battery's internal resistance value.

[0075] Equation 1 illustrates the case where the second charge change ΔQ_comp is independent of the first charge change ΔQ. However, unlike this, it can be set such that the second charge change ΔQ_comp is affected by the first charge change ΔQ, while the predicted open-circuit voltage OCVe follows the battery terminal voltage Vm.

[0076] As described above, when the first compensator 320 is in a state where the battery current Im is less than the first threshold (even if the battery is not in a sufficiently relaxed state), the error of the second predicted charge Qe can be prevented from accumulating by making the predicted open-circuit voltage OCVe follow the battery terminal voltage Vm.

[0077] The second lookup table (LUT2) 330 may include data for primary and secondary corrections of the voltage-based remaining prediction time RTV. The second compensator 340 may use the second lookup table 330 to linearize the discontinuous components of the voltage-based remaining prediction time RTV to generate a remaining prediction time RTV_1st based on the primary correction voltage, and may compensate for characteristic differences in the remaining prediction time RTV_1st based on the primary correction voltage according to the discharge current and battery temperature to generate a remaining prediction time RTV_2nd based on the secondary correction voltage.

[0078] When the magnitude of the battery current Im is greater than the second threshold, the second compensator 340 can calculate the charge change compensation coefficient COMP_RATE based on the ratio of the voltage-based remaining prediction time RTV calculated based on the battery terminal voltage Vm to the charge-based remaining prediction time RTQ calculated based on the second predicted charge Qe. The charge change compensation coefficient COMP_RATE is then multiplied by the first charge change ΔQ to calculate the second charge change ΔQ_comp.

[0079] For example, the magnitude of the battery current Im can be the average of the absolute values ​​of the battery current Im during the accumulation period of the first coulomb counter 100, but is not limited to this. Furthermore, according to an embodiment, the second compensator 340 can be configured to operate only after a predetermined number of determinations that the magnitude of the battery current Im is greater than a second threshold. The second threshold can be set to a value that determines whether the battery is in a charging or discharging state.

[0080] The following reference Figures 2 to 19 The composition of the second compensator 340 is described in detail.

[0081] Figure 2 This is an example diagram illustrating the overall structure of the charge change compensation coefficient COMP_RATE calculated by the ratio of the remaining prediction time RTQ based on charge quantity to the remaining prediction time RTV based on voltage quantity, according to one embodiment of the present invention.

[0082] Further reference Figure 2One embodiment of the present invention predicts the current battery usable time and thereby corrects the rate of decrease of the battery charge Q, thus estimating the accurate decrease of the battery charge Q. In one embodiment of the present invention, two battery usable times are predicted: one is the remaining time by voltage (RTV), which is used to predict the battery usable time based on the current battery voltage; the other is the remaining time by charge (RTQ), which is used to predict the usable time based on the current second predicted charge Qe (S20). When predicting the usable time, the final ratio of RTV to RTQ, RTQRTV_RATE, is used to calculate the charge change compensation coefficient COMP_RATE, thereby adjusting the rate of decrease of the current second predicted charge Qe. RTV varies greatly depending on temperature and discharge current, therefore it is corrected twice.

[0083] The remaining predicted time RTQ based on charge is the time required for the current remaining capacity to reach 0 under battery discharge conditions, and it can be calculated based on the absolute value of the product of the second predicted charge Qe and the battery current Im and the charge change compensation coefficient COMP_RATE.

[0084] That is, the remaining prediction time based on charge at any point in time can be calculated using the following mathematical formula 2.

[0085]

Mathematical Formula 2

[0086] Further reference Figure 3 RTV can be defined as the time required for the currently measured battery voltage Vm to reach the termination voltage Vterm under battery discharge conditions.

[0087] The battery's termination voltage Vterm can have different values ​​for each system, but the state of charge (SOC) at the termination point should be 0%.

[0088] At any time point t, RTV can find a straight line with intercept Vm(t) and slope ΔOCVm / ΔT, and calculate the time required for its value to reach the termination voltage Vterm.

[0089] The equation of the straight line is shown in mathematical formula 3.

[0090]

Mathematical Expression 3

[0091] In actual discharge conditions, due to the large noise of the battery voltage Vm, it is difficult to obtain a stable slope. Therefore, the slope can be obtained by using the open-circuit voltage OCVm, which always decreases monotonically.

[0092] At any time point t, RTV is the time required for the battery voltage Vm to reach the termination voltage Vterm, and therefore can be calculated as shown in the following mathematical formula 4.

[0093]

Mathematical Expression 4

[0094] Further reference Figure 4 Since the waveform of RTV calculated using mathematical formulas 3 and 4 is not linear, it is difficult to accurately predict RTV at any given time point. Therefore, RTV can be calculated more accurately using the first and second corrections described later.

[0095] Figure 5 This is a diagram conceptually illustrating a single correction for converting RTV to RTV_ref according to one embodiment of the present invention. Figure 6 This is an embodiment of the present invention, which exemplarily illustrates a flowchart of an RTV single-pass calibration.

[0096] Reference Figure 5 and Figure 6 The first correction for RTV is as follows Figure 5 The linearization of discontinuous RTV, as shown, can be achieved through... Figure 6 The processing sequence shown is used to generate the second lookup table 330. For example, a vector that discharges under conditions of 25°C and 0.02C can be used.

[0097] To perform RTV primary correction, RTV / RTV_ref can be calculated, and interval-wise linear fitting can be performed on this. Interval-wise linear fitting is a method that divides the data into multiple linear functions to find the most suitable straight line for each interval. That is, instead of approximating all the data as a straight line, it divides the data into multiple intervals based on its characteristics and finds the most suitable straight line in each interval to more accurately represent the data.

[0098] When the linear expression of the fitting is L[1], L[2], ..., L[n], the RTV_1st of the LTV after one correction can be represented by mathematical formula 5 and mathematical formula 6 respectively.

[0099]

Mathematical Expression 5

[0100]

Mathematical Expression 6

[0101] RTV_1st = RTV * L[n]

[0102] As a more specific example, refer to Figure 6 In step S32, the process of calculating OCVm[n] by dividing the linear interval of RTV can be executed. In step S34, the process of calculating slope[n] and intercept[n] by finding the slope and intercept used for the linear transformation of each interval can be executed. In step S36, the process of generating a second lookup table 330 including OCVm[n], slope[n], and intercept[n] can be executed.

[0103] Figure 7 The figure illustrates, by way of example, the simulation results of a single RTV correction performed under discharge conditions of 25°C and -0.02C, according to one embodiment of the present invention.

[0104] Reference Figure 7 As can be seen from the example, RTV_1st, which is an RTV after one correction, accurately represents the remaining time, just like RTV_ref.

[0105] Figure 8 According to one embodiment of the present invention, a graph is provided exemplarily showing the voltage characteristics at different temperatures under a discharge current of -0.8A. Figure 9This is an example illustration of the voltage characteristics corresponding to different discharge currents under a temperature condition of 25°C, according to one embodiment of the present invention. Figure 10 This is an example illustration of a graph showing the first correction result of the voltage curve under conditions of 25°C and -0.8A, according to one embodiment of the present invention. Figure 11 According to one embodiment of the present invention, an exemplary graph is shown showing the first correction result of the voltage curve under the conditions of -10°C and -0.8A.

[0106] Reference Figures 8 to 11 The simulation results of a first-order correction of RTV based on various battery conditions are shown.

[0107] like Figure 8 and Figure 9 As shown, the voltage curve characteristics of the battery vary with temperature and discharge current.

[0108] Figure 10 The simulation results of the first-order correction of RTV under the discharge conditions of 25℃ and -0.8A are shown. Figure 11 The simulation results of the first-order correction of RTV under discharge conditions of -10℃ and -0.02C are shown.

[0109] Reference Figure 10 and Figure 11 For example, since the voltage curve characteristics of the battery vary with temperature and discharge current, it is known that an error occurs in the remaining prediction time RTV_1st based on the first correction voltage, which is the result of the first correction to RTV, and in order to improve this error, a second correction to RTV is applied.

[0110] The second correction of RTV can be calculated by multiplying the result of the first correction of RTV by the remaining time RTV_1st based on the first correction voltage by a quadratic polynomial, and expressed as the following mathematical formula 7.

[0111]

Mathematical Expression 7

[0112] RTV_2nd = (Ax 2 + Bx + C) *RTV_1st

[0113] x = OCVm_MAX – OCVm

[0114] RTV_1st is the remaining prediction time based on the first correction voltage, and RTV_2nd is the remaining prediction time based on the second correction voltage. The coefficients A, B, and C of the quadratic polynomial are values ​​stored in the second lookup table 330. OCVm_MAX is the maximum value of OCVm, which is usually the full charge voltage of the battery.

[0115] The coefficients A, B, and C of the quadratic polynomial vary depending on the battery temperature and discharge current, and their values ​​can be stored in the second lookup table 330.

[0116] Table 1 below shows examples of the temperature and current conditions of the battery used to obtain the coefficients of the quadratic polynomial.

[0117] Table 1 NO Temperature (°C) Current (A) 1 40 -2.0 2 40 -1.2 3 40 -0.8 4 25 -2.0 5 25 -1.2 6 25 -0.8 7 0 -2.0 8 0 -1.2 9 0 -0.8 10 -10 -2.0 11 -10 -1.2 12 -10 -0.8

[0118] Further refer to the exemplary flowchart in Table 1 and RTV secondary correction. Figure 12 In step S42, the process of measuring the battery temperature Tm and the discharge current Im can be performed.

[0119] In step S44, the process of reading the coefficients A, B, and C of the quadratic polynomial from the second lookup table 330 can be performed.

[0120] In the second lookup table 330, the coefficients A, B and C of the quadratic polynomial can be matched and stored with the battery temperature Tm and the discharge current Im, and expressed as the following mathematical expression 8.

[0121]

Mathematical Expression 8

[0122] A, B, C = LUT2 (Tm, Im)

[0123] When the battery temperature Tm and the discharge current Im are between the values ​​stored in the second lookup table 330, the interpolation of the values ​​stored in the second lookup table 330 can be applied to the coefficients A, B and C of the quadratic polynomial.

[0124] In step S44, the process of calculating the remaining prediction time RTV_2nd based on the quadratic correction voltage can be performed by applying the coefficients A, B, and C of the quadratic polynomial stored in the second lookup table 330 to mathematical expression 7.

[0125] Figure 13 This is an example illustration of simulation results of RTV primary and secondary corrections performed under discharge conditions of 25°C and -0.8A, according to one embodiment of the present invention. Figure 14 This is an example of a simulation result of the first and second RTV corrections performed under discharge conditions of -10°C and -0.8A, according to an embodiment of the present invention.

[0126] Further reference Figure 13 and Figure 14It can be confirmed that under discharge conditions of 25℃ and -0.8A and -10℃ and -0.8A, the accuracy of the RTV secondary correction result is improved compared with the RTV primary correction result.

[0127] Figure 15 According to one embodiment of the present invention, an exemplary flowchart for calculating the charge change compensation coefficient COMP_RATE is shown.

[0128] Further reference Figure 15 In step S52, the process of calculating the ratio of the remaining prediction time RTQ based on the charge quantity to the remaining prediction time RTV based on the secondary correction voltage can be performed and expressed as the following mathematical formula 9.

[0129]

Mathematical Expression 9

[0130] In step S54, the process of calculating the charge change compensation coefficient COMP_RATE can be performed and expressed as the following mathematical formula 10.

[0131]

Mathematical Formula 10

[0132] Figures 16 to 19 This is a diagram used to illustrate a comparison between the effects of an embodiment of the present invention and the prior art.

[0133] Further reference Figures 16 to 19 In one embodiment of the present invention, the accumulation ratio of the first coulomb counter is adjusted by a charge change compensation coefficient COMP_RATE calculated based on the remaining prediction time RTQ based on the charge quantity and the remaining prediction time RTV based on the voltage. That is, in one embodiment of the present invention, by applying the charge change compensation coefficient COMP_RATE, simulation results with improved accuracy of state of charge (SOC) estimation can be obtained.

[0134] Figure 18 Qe1 is the result of the second predicted charge Qe calculated by the third coulomb counter when the charge change compensation coefficient COMP_RATE is fixed at 1, and Qe2 is the result of the second predicted charge Qe calculated by the third coulomb counter when the charge change compensation coefficient COMP_RATE is calculated by applying the voltage-based residual prediction time RTV and the charge-based residual prediction time RTQ according to an embodiment of the present invention.

[0135] Reference Figure 19 For example, when the charge change compensation coefficient COMP_RATE is fixed at 1, the SOC1, which is the estimated state of charge, produces a large error. However, according to an embodiment of the present invention, when the charge change compensation coefficient COMP_RATE is calculated by applying the voltage-based remaining prediction time RTV and the charge-based remaining prediction time RTQ, the SOC2, which is the estimated state of charge, accurately estimates the state of charge SOC.

[0136] The multiplier 350 can calculate the third charge change ΔQ_cr by multiplying the charge change compensation coefficient COMP_RATE, which is the output of the second compensator 340, by the first charge change ΔQ.

[0137] Multiplexer 360 can output a value selected from a fourth charge change ΔQ_track (output of first compensator 320) and a third charge change ΔQ_cr (generated by second compensator 340) based on a mode. To this end, multiplexer 360 can receive a mode selection signal mode from a controller (not shown) and output the value selected from the third charge change ΔQ_cr and fourth charge change ΔQ_track based on mode selection signal mode as a second charge change ΔQ_comp. For example, as shown in mathematical formula 11, when mode selection signal mode is '0', multiplexer 360 can output the third charge change ΔQ_cr, and when mode selection signal mode is '1', multiplexer 360 can output the fourth charge change ΔQ_track. That is, multiplexer 360 can make first compensator 320 and second compensator 340 operate selectively according to mode selection signal mode.

[0138]

Mathematical Expression 11

[0139] on the other hand, Figure 1 An example is shown where the first compensator 320 and the second compensator 340 are used together, but the battery state-of-charge estimation device 10 can selectively use either the first compensator 320 or the second compensator 340. In this case, the multiplexer 360 can be omitted or used to select whether the corresponding controller is operational.

[0140] Furthermore, the first threshold for determining whether the first compensator 320 is operational and the second threshold for determining whether the second compensator 340 is operational can be the same value. In this case, the first compensator 320 can operate when the battery current Im is less than the first threshold (or the second threshold), and the second compensator 340 can operate when the battery current Im is greater than the first threshold (or the second threshold). Alternatively, according to an embodiment, the second threshold can have a value greater than the first threshold. In this case, the first compensator 320 can operate when the battery current Im is less than the first threshold, neither the first compensator 320 nor the second compensator 340 operates when the battery current Im is greater than the first threshold and less than the second threshold, and the second compensator 340 can operate when the battery current Im is greater than the second threshold.

[0141] According to an embodiment, the first compensator 320 can calculate the value of the fourth charge change amount ΔQ_track based on the different magnitudes of the battery voltage Vm and the predicted open-circuit voltage OCVe. For example, when the battery voltage Vm is greater than the predicted open-circuit voltage OCVe, as shown in Equation 12, the fourth charge change amount ΔQ_track is set to '0' so that the predicted open-circuit voltage OCVe does not change. When the battery voltage Vm is less than the predicted open-circuit voltage OCVe, the fourth charge change amount ΔQ_track is calculated as shown in Equation 12 so that the predicted open-circuit voltage OCVe follows the battery voltage Vm.

[0142]

Mathematical Expression 12

[0143] In Equation 12, when the battery voltage Vm is greater than the predicted open-circuit voltage OCVe, the reason for setting the fourth charge change ΔQ_track to '0' is to prevent the following problem: when the fourth charge change ΔQ_track is given a positive value to increase the predicted open-circuit voltage OCVe, the battery will increase the second predicted charge Qe and the calculated state of charge while maintaining the discharge state.

[0144] Furthermore, in Equation 12, the first constant C1 is a constant that affects the rate at which the predicted open-circuit voltage OCVe follows the battery terminal voltage Vm. By appropriately setting the first constant C1, the predicted open-circuit voltage OCVe can progressively follow the battery terminal voltage Vm. According to an embodiment, the first constant C1 is set based on the internal resistance R of the battery, such that the predicted open-circuit voltage OCVe follows the battery terminal voltage Vm at a rate matching the battery's time constant.

[0145] The third coulomb counter 400 (CCE) calculates the second predicted charge Qe by accumulating the second charge change ΔQ_comp. If the first coulomb counter 100 performs periodic accumulation, the third coulomb counter 400 can be understood as accumulating and summing the battery current Im without a specific period. The difference from a typical current accumulation method is that the third coulomb counter 400 does not directly accumulate the battery current Im, but instead accumulates the second charge change ΔQ_comp as a value compensated by the compensator 300.

[0146] The State of Charge (SOC) estimator 500 can estimate the battery's state of charge based on a second predicted charge quantity Qe. According to an embodiment, the battery state of charge output by the SOC estimator 500 can be SOC (state of charge), but is not limited to this. For example, the battery state of charge can be a value corresponding to the value obtained by dividing the second predicted charge quantity Qe by the battery's design capacity.

[0147] According to an embodiment, the battery state-of-charge estimation device 10 described above can be implemented in software, and its functions can be executed by a computing device such as a CPU while stored in a computer-readable storage medium (memory, etc.). In this case, the various elements within the battery state-of-charge estimation device 10 can be implemented as separate modules within the software implementing the battery state-of-charge estimation device 10 for differentiation, or they can be implemented as a mixture of functions within the software without differentiation, depending on the situation. According to an embodiment, the battery state-of-charge estimation device 10 can be implemented in hardware such as an ASIC (Application Specific Integrated Circuit) or a FPGA (Field Programmable Gate Array).

[0148] For the terms "comprising," "consisting of," or "having," unless specifically stated otherwise, they indicate that the corresponding constituent element may be included, but do not exclude other constituent elements, and should be understood as capable of further including other constituent elements. Unless otherwise defined, all terms, including technical and scientific terms, have the same meaning as commonly understood by those skilled in the art. Commonly used terms, such as those defined in dictionaries, should be interpreted as consistent with their meaning in the relevant technical context, and should not be interpreted in an ideal or overly formal sense unless explicitly defined by the present invention.

[0149] The above description is merely an illustrative example of the technical concept of the present invention. Those skilled in the art can make various modifications and variations without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in this invention are not intended to limit the technical concept of the present invention, but rather to illustrate it, and the scope of the technical concept of the present invention is not limited by these embodiments. The scope of protection of this invention should be interpreted by the appended claims, and all technical concepts within their equivalent scope should be understood to be included within the scope of the claims of this invention.

[0150] Figure Labels

[0151] 10: Battery state of charge estimation device

[0152] 100: First coulomb counter

[0153] 200: Second coulomb counter

[0154] 300: Compensator

[0155] 310: First lookup table

[0156] 320: First compensator

[0157] 330: Second lookup table

[0158] 340: Second compensator

[0159] 350: Multiplier

[0160] 360: Multiplexer

[0161] 400: Third coulomb counter

[0162] 500: State of Charge Estimation Device

Claims

1. A battery state-of-charge estimation device, comprising: The first coulomb counter accumulates the battery current (Im) in each specified period to calculate the first charge change (ΔQ) for each period. A second coulomb counter is used to accumulate the first charge change (ΔQ) to calculate the first predicted charge (Qm). A compensator that uses the first predicted charge (Qm) and the second predicted charge (Qe) to compensate for the first charge change (ΔQ) to calculate the second charge change (ΔQ_comp). A third coulomb counter is used to calculate the second predicted charge (Qe) by accumulating the second charge change (ΔQ_comp). as well as A state of charge estimator that estimates the state of charge of the battery based on the second predicted charge quantity (Qe).

2. The battery state of charge estimation device according to claim 1, characterized in that, The compensator uses the second predicted charge quantity (Qe) to calculate the predicted open-circuit voltage (OCVe), and uses the predicted open-circuit voltage (OCVe) to calculate the second charge change (ΔQ_comp).

3. The battery state of charge estimation device according to claim 2, characterized in that, When calculating the predicted open-circuit voltage (OCVe) using the second predicted charge (Qe), the compensator uses a first lookup table containing data on the relationship between the charge (Q) and open-circuit voltage (OCV) corresponding to the battery.

4. The battery state of charge estimation device according to claim 1, characterized in that, When the magnitude of the battery current (Im) is less than the first threshold, the compensator compensates for the first charge change (ΔQ) to reduce the difference between the predicted open-circuit voltage (OCVe) and the battery terminal voltage (Vm), thereby calculating the second charge change (ΔQ_comp).

5. The battery state of charge estimation device according to claim 4, characterized in that, The compensator calculates the second charge change (ΔQ_comp) based on the value obtained by multiplying the predicted open-circuit voltage (OCVe) by a first constant (C1).

6. The battery state of charge estimation device according to claim 5, characterized in that, The first constant (C1) is predetermined based on the internal resistance value of the battery.

7. The battery state of charge estimation device according to claim 1, characterized in that, When the magnitude of the battery current (Im) is greater than the second threshold, the compensator calculates the charge change compensation coefficient (COMP_RATE) based on the ratio of the voltage-based remaining prediction time (RTV) calculated according to the battery terminal voltage (Vm) to the charge-based remaining prediction time (RTQ) calculated according to the second predicted charge amount (Qe), and multiplies the charge change compensation coefficient (COMP_RATE) by the first charge change amount (ΔQ) to calculate the second charge change amount (ΔQ_comp).

8. The battery state of charge estimation device according to claim 7, characterized in that, The remaining prediction time based on charge (RTQ) is the time required for the battery's current remaining capacity to reach 0 under the battery's discharge conditions.

9. The battery state of charge estimation device according to claim 8, characterized in that, The remaining prediction time (RTQ) based on charge is calculated based on the absolute value of the product of the second predicted charge (Qe) and the battery current (Im) and the charge change compensation coefficient (COMP_RATE).

10. The battery state of charge estimation device according to claim 7, characterized in that, The voltage-based remaining prediction time (RTV) is the time required for the current battery voltage (Vm) to reach the termination voltage (Vterm) under the battery's discharge conditions.

11. The battery state of charge estimation device according to claim 10, characterized in that, The voltage-based Remaining Predictive Time (RTV) is calculated by multiplying the value obtained by subtracting the battery voltage (Vm) from the termination voltage (Vterm) by the reciprocal of the slope of the opening voltage (OCVm) (ΔT / ΔOCVm).

12. The battery state of charge estimation device according to claim 7, characterized in that, The compensator linearizes the discontinuous components of the voltage-based residual prediction time (RTV) to generate a residual prediction time (RTV_1st) based on a first-correction voltage.

13. The battery state of charge estimation device according to claim 12, characterized in that, The compensator corrects the remaining prediction time (RTV_1st) based on the primary correction voltage according to the characteristic differences caused by the discharge current and battery temperature, so as to generate the remaining prediction time (RTV_2nd) based on the secondary correction voltage.

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