Battery management system and battery management method

Abstract

A battery management system and a battery management method are provided. The battery management system according to the present invention comprises: a sensing unit configured to measure a battery voltage value and a battery current value of a battery; and a control unit configured to estimate a temporary SOC of the battery on the basis of the battery voltage value and the battery current value. The control unit is configured to determine a reference SOC section from a reference voltage profile on the basis of the battery voltage value if it is determined that a constant current stimulus is being applied to the battery on the basis of the battery current value. The control unit is configured to determine a confirmed SOC of the battery on the basis of a comparison between the temporary SOC and the reference SOC section.

Description

Battery Management System and Battery Management Method

[0001] The present invention relates to a technique for estimating the state of charge of a battery.

[0002] This application is a priority application for Korean Patent Application No. 10-2024-0188342 filed on December 17, 2024, and all contents disclosed in the specification and drawings of said application are incorporated into this application by reference.

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

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

[0005] One of the important parameters required to control the charging and discharging of a battery is the state of charge (SOC). SOC is a parameter representing the relative ratio of the current capacity to the maximum capacity, which indicates the total electrical energy when the battery is fully charged, and can be expressed as 0% to 100% (or 0 to 1). For example, if the maximum capacity of the battery is 1000 Ah (ampere-hour) and the capacity currently stored in the battery is 750 Ah, the battery's SOC is 75%.

[0006] The Extended Kalman Filter (EKF) is widely used for estimating the State of Charge (SOC) of batteries. A standard EKF is an SOC estimation model that utilizes an Equivalent Circuit Model (ECM) and an Open Circuit Voltage (SOC-OCV) curve, respectively, pre-programmed to match the electrochemical characteristics of the battery; when the battery voltage and current are input variables, it outputs an estimated SOC value, which is one of the state variables.

[0007] Meanwhile, the SOC-OCV (Open Circuit Voltage) curve of some battery types, such as lithium iron phosphate (LFP) batteries, may contain at least one voltage flat region. If two or more voltage flat regions exist, a voltage inflection point may be located between them.

[0008] Unlike the open circuit state where charging and discharging are stopped, if a constant current stimulus (a constant charging current or discharging current) is applied, the voltage flatness characteristics of the battery are weakened, and the higher the intensity of the constant current stimulus, the more significantly the voltage flatness characteristics are weakened or disappear completely.

[0009] In order for the current-dependent characteristics of the voltage flatness of the battery described above to be faithfully reflected in the EKF, the ECM must be designed with high precision. However, as the design precision of the ECM increases, the number of components included in the ECM becomes excessively large, and the inter-component relationships inevitably become more complex, which has the disadvantage of increasing the amount of computation and data storage space required for SOC estimation. Furthermore, even if the design precision of the ECM is increased, there is a problem in that it is difficult to perfectly reflect the dependence of the voltage flatness characteristics on constant current stimulation.

[0010] To address the problems caused by the constraints of the ECM, a method can be proposed to estimate the battery's SOC using ampere counting instead of EKF during the application period of constant current stimulation. Ampere counting is a type of SOC estimation model that refers to a method of estimating the battery's SOC by converting the integrated value of the current flowing through the battery into a change in SOC. However, as the duration of constant current stimulation is prolonged, current measurement errors also accumulate over time, which has the disadvantage that the accuracy of SOC estimation by ampere counting gradually decreases.

[0011] The problems of the aforementioned conventional SOC estimation methods can be resolved by intentionally charging or discharging the battery to a sufficiently low or high OCV range to ensure that the battery's SOC is within the SOC range without voltage flatness characteristics, and then estimating the SOC based on OCV; however, in this case, unnecessary energy is consumed and the SOC estimation takes an excessively long time.

[0012] The present invention was devised to solve the above-mentioned problems and aims to provide a battery management system and a battery management method that accurately estimate the SOC of a battery by utilizing the relationship between voltage flatness characteristics and the intensity of a constant current stimulus.

[0013] Other objects and advantages of the present invention may be understood from the following description and will become more clearly apparent from the embodiments of the present invention. Furthermore, it will be readily apparent that the objects and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims.

[0014] A battery management system according to one aspect of the present invention includes: a sensing unit configured to measure a battery voltage value and a battery current value of a battery; and a control unit configured to estimate a temporary SOC of the battery based on the battery voltage value and the battery current value. The control unit is configured to determine a reference SOC range from a reference voltage profile based on the battery voltage value when it is determined that a constant current stimulus is being applied to the battery based on the battery current value. The control unit is configured to determine a confirmed SOC of the battery based on a comparison of the temporary SOC and the reference SOC range.

[0015] The control unit may be configured to determine that a constant current stimulus is being applied to the battery when the amount of current change based on the battery current value is within a reference range.

[0016] The control unit may be configured to select one voltage profile corresponding to the battery current value among a plurality of voltage profiles associated with different current indicators as the reference voltage profile.

[0017] The control unit may be configured to determine a reference voltage range based on the battery voltage value and voltage measurement error. The control unit may be configured to determine the SOC range mapped to the reference voltage range in the reference voltage profile as the reference SOC range.

[0018] The control unit may be configured to determine the confirmed SOC in the same way as the temporary SOC when the temporary SOC is within the reference SOC range.

[0019] The control unit may be configured to determine the confirmed SOC based on the difference in SOC between the temporary SOC and the lower limit SOC when the temporary SOC is less than the lower limit SOC of the reference SOC range.

[0020] The control unit may be configured to determine a correction ratio based on the size of the reference SOC interval, determine a correction value by multiplying the SOC difference by the correction ratio, and determine the confirmed SOC by applying the correction value to the temporary SOC.

[0021] The above control unit may be configured to determine the correction ratio by applying a predetermined negative correspondence to the size of the above reference SOC interval.

[0022] The control unit may be configured to determine the confirmed SOC based on the difference in SOC between the temporary SOC and the upper limit SOC when the temporary SOC exceeds the upper limit SOC of the reference SOC range.

[0023] A battery pack according to another aspect of the present invention includes the battery management system.

[0024] An electric vehicle according to another aspect of the present invention includes the battery pack.

[0025] A battery management method according to another aspect of the present invention comprises: a step of measuring a battery voltage value and a battery current value of a battery; a step of estimating a temporary SOC of the battery based on the battery voltage value and the battery current value; a step of determining a reference SOC range from a reference voltage profile based on the battery voltage value when it is determined that a constant current stimulus is being applied to the battery based on the battery current value; and a step of determining a confirmed SOC of the battery based on a comparison of the temporary SOC and the reference SOC range.

[0026] The step of determining the reference SOC range may include: determining a reference voltage range based on the battery voltage value and voltage measurement error; and determining the SOC range mapped to the reference voltage range in the reference voltage profile as the reference SOC range.

[0027] In the step of determining the confirmed SOC of the battery, if the temporary SOC exceeds the upper limit SOC of the reference SOC range, the confirmed SOC can be determined based on the SOC difference between the temporary SOC and the upper limit SOC.

[0028] In the step of determining the confirmed SOC of the battery, if the temporary SOC is less than the lower limit SOC of the reference SOC range, the confirmed SOC can be determined based on the difference in SOC between the temporary SOC and the lower limit SOC.

[0029] A computer-readable medium according to another aspect of the present invention can record a program for executing the battery management method on a computer.

[0030] According to at least one of the embodiments of the present invention, the accuracy of estimating the battery SOC can be improved by utilizing the relationship between the voltage flatness characteristic and the intensity of the constant current stimulation.

[0031] In addition, according to at least one of the embodiments of the present invention, since there is no need to intentionally charge or discharge the battery into an SOC range where the voltage flatness characteristic is absent or very weak, unnecessary energy consumption can be reduced and the time required for SOC estimation can be shortened.

[0032] The effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description in the claims.

[0033] The following drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the detailed description of the invention provided below; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings.

[0034] FIG. 1 is a schematic diagram showing the configuration of an electric vehicle according to the present invention.

[0035] Figure 2 is a diagram showing an example of an equivalent circuit model for the battery shown in Figure 1.

[0036] Figure 3 is a diagram exemplarily showing the SOC-OCV curve of the battery illustrated in Figure 1.

[0037] FIG. 4 is a drawing referenced to explain a constant current stimulation map according to the present invention.

[0038] FIG. 5 is a flowchart exemplarily illustrating a battery management method according to one embodiment of the present invention.

[0039] Figure 6 is a flowchart illustrating an example of subroutines that can be included in step S540 of Figure 5.

[0040] Figure 7 is an exemplary graph referenced to explain the method of Figure 6.

[0041] FIG. 8 is a flowchart illustrating an example of subroutines that can be included in step S550 of FIG. 5.

[0042] FIG. 9 is a flowchart illustrating another example of subroutines that can be included in step S550 of FIG. 5.

[0043] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Prior to this, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, and should be interpreted in a meaning and concept consistent with the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0044] Therefore, the embodiments described in this specification and the configurations illustrated in the drawings are merely the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention; thus, it should be understood that various equivalents and modifications that can replace them may exist at the time of filing this application.

[0045] Terms including ordinal numbers, such as first, second, etc., are used for the purpose of distinguishing one of the various components from the rest, and are not used to limit the components by such terms.

[0046] Throughout the specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components. Furthermore, terms such as "<unit>" as used in the specification refer to a unit that performs at least one function or operation and may be implemented in hardware, software, or a combination of hardware and software.

[0047] Additionally, throughout the specification, when it is said that a part is "connected" to another part, this includes not only cases where they are "directly connected," but also cases where they are "indirectly connected" with other components in between.

[0048] FIG. 1 is a schematic diagram showing the configuration of an electric vehicle according to the present invention.

[0049] It includes a vehicle controller (2), a battery pack (10), a relay (20), an inverter (30), and an electric motor (40). The charging and discharging terminals (P+, P-) of the battery pack (10) can be electrically connected to a charger (3) via a charging cable, etc. The charger (3) may be included in the electric vehicle (1) or provided in a charging station.

[0050] A vehicle controller (2) (e.g., ECU: Electronic Control Unit) is configured to transmit a key-on signal to a battery management system (100) in response to a user switching a start button (not shown) provided in an electric vehicle (1) to the ON position. The vehicle controller (2) is configured to transmit a key-off signal to a battery management system (100) in response to a user switching the start button to the OFF position. A charger (3) can communicate with the vehicle controller (2) to supply charging power of a constant current or constant voltage through the charging / discharging terminals (P+, P-) of the battery pack (10).

[0051] The battery pack (10) includes a battery group (11) and a battery management system (100).

[0052] The battery group (11) includes at least one battery (B). In FIG. 1, a plurality of batteries (B1~B N , N is a natural number greater than or equal to 2) is exemplified as being included in the battery group (11). Multiple batteries (B1~B N ) can be interconnected in series, parallel, or a combination of series and parallel. In the following description, a plurality of batteries (B1~B N In explaining the common content of ), the symbol 'B' was assigned to the battery cell.

[0053] The battery (B) is capable of repeated charging and discharging. The battery (B) may include at least one battery cell having a voltage plateau characteristic, such as an LFP cell (which may be referred to as a 'LiFePO4 cell'). The voltage plateau characteristic refers to a characteristic in which the rate of change of OCV is maintained at 0 or below a predetermined threshold value even with a change in SOC.

[0054] The relay (20) is electrically connected in series to the battery group (11) through a power path connecting the battery group (11) and the inverter (30). In FIG. 1, the relay (20) is illustrated as being connected between the positive terminal and the charge / discharge terminal (P+) of the battery group (11). The relay (20) is turned on / off in response to a switching signal from the battery management system (100). The relay (20) may be a mechanical contactor that is turned on / off by the magnetic force of a coil, or a semiconductor switch such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor).

[0055] An inverter (30) is provided to convert direct current from a battery group (11) into alternating current in response to a command from a battery management system (100) or a vehicle controller (2).

[0056] The electric motor (40) is driven using alternating current power from the inverter (30). For example, a three-phase alternating current motor (40) can be used as the electric motor (40).

[0057] The battery management system (100) includes a sensing unit (110) and a control unit (130). The battery management system (100) may further include a communication circuit (150).

[0058] The sensing unit (110) includes a voltage sensor (111) and a current sensor (113), and may further include a temperature sensor (115).

[0059] The voltage sensor (111) is connected to the positive and negative terminals of the battery (B) included in the battery group (11) to measure a battery voltage value representing the voltage across both ends of the battery (B), and is configured to output a voltage signal representing the measured battery voltage value to the control unit (130). The voltage sensor (111) may be implemented as one or more combinations of known voltage detection elements, such as a voltage measurement IC.

[0060] The current sensor (113) is connected in series to the battery group (11) through a current path between the battery group (11) and the inverter (30). The current sensor (113) is configured to measure a battery current value representing the current flowing through the battery group (11) and to output a current signal representing the measured battery current value to the control unit (130). The current sensor (113) may be implemented as one or more combinations of known current detection elements, such as a shunt resistor, a Hall effect element, etc.

[0061] The temperature sensor (115) is configured to measure the battery temperature value of the battery (B) and output a temperature signal indicating the measured battery temperature value to the control unit (130). The temperature sensor (115) may be implemented as one or more combinations of known temperature detection elements, such as a thermocouple, a thermistor, a bimetal, etc.

[0062] The communication circuit (150) is configured to support wired or wireless communication between the control unit (130) and the vehicle controller (2). Wired communication may be, for example, CAN (Controller Area Network) communication, and wireless communication may be, for example, Zigbee or Bluetooth communication. Of course, as long as wired or wireless communication between the control unit (130) and the vehicle controller (2) is supported, the type of communication protocol is not specifically limited. The communication circuit (150) may include an output device (e.g., display, speaker) that provides information received from the control unit (130) and / or the vehicle controller (2) in a form recognizable by the user.

[0063] The control unit (130) is operably coupled to the relay (20), the sensing unit (110), and the communication circuit (150). Being operably coupled to the two components means that the two components are directly or indirectly connected so that signals can be transmitted and received in either a unidirectional or bidirectional manner.

[0064] The control unit (130) can collect a voltage signal from the voltage sensor (111), a current signal from the current sensor (113), and / or a temperature signal from the temperature sensor (115). The control unit (130) can convert and record each analog signal collected from the sensors (111, 113, 115) into a digital value using an internally provided ADC (Analog to Digital Converter).

[0065] The control unit (130) may be referred to as a 'control circuit' or 'battery controller' and may be implemented in hardware using at least one of ASICs (application specific integrated circuits), DSPs (digital signal processors), DSPDs (digital signal processing devices), PLDs (programmable logic devices), FPGAs (field programmable gate arrays), microprocessors, and other electrical units for performing functions.

[0066] The memory unit (131) may include at least one type of storage medium among, for example, a flash memory type, a hard disk type, an SSD type (Solid State Disk type), an SSD type (Silicon Disk Drive type), a multimedia card micro type, RAM (random access memory; RAM), SRAM (static random access memory), ROM (read-only memory; ROM), EEPROM (electrically erasable programmable read-only memory), and PROM (programmable read-only memory). The memory unit (131) may store data and programs required for operation by the control unit (130). The memory unit (131) may store data representing the result of operation by the control unit (130). Although the memory unit (131) is shown as being physically independent from the control unit (130) in FIG. 1, it may be embedded within the control unit (130).

[0067] The memory unit (131) can store an equivalent circuit model (see FIG. 2), a SOC-OCV curve (see FIG. 3), a constant current stimulation map (see FIG. 4), and an extended Kalman filter. The SOC-OCV curve, the constant current stimulation map, and the extended Kalman filter will each be described in more detail below.

[0068] The control unit (130) can turn on the relay (20) in response to a key-on signal. The control unit (130) can turn off the relay (20) in response to a key-off signal. The key-off signal indicates a transition from cycle mode to idle mode. Alternatively, the on / off control of the relay (20) can be handled by the vehicle controller (2) instead of the control unit (130).

[0069] While the relay (20) is turned on, the battery (B) of the battery group (11) is in cycle mode. Cycle mode refers to an operating state capable of charging and discharging. Cycle mode can be divided into constant current charging mode, constant current discharging mode, and non-constant current charging and discharging mode.

[0070] The constant current charging mode refers to a state in which a constant charging current flows through the battery (B). The constant current discharging mode refers to a state in which a constant discharging current flows through the battery (B).

[0071] The non-constant current charging / discharging mode refers to a state in which a time-varying charging current or discharging current flows through the battery (B) (e.g., constant voltage charging).

[0072] While the relay (20) is turned off, the battery (B) of the battery group (11) enters a idle mode. An idle mode refers to an operating state in which the battery current is cut off and charging or discharging is not possible.

[0073] In the present specification, the first operating state of the battery (B) means that the battery (B) is in a resting mode or a non-constant current charging / discharging mode. The second operating state of the battery (B) means that a constant current stimulus is being applied to the battery (B), that is, the battery (B) is in a constant current charging mode or a constant current discharging mode.

[0074] The control unit (130) can determine (estimate) the SOC of the battery (B) based on the battery voltage value, battery current value and / or battery temperature value indicated by the signal(s) collected from the sensing unit (110) while the battery group (11) is in cycle mode. The SOC may represent the ratio of the remaining capacity to the full charge capacity (maximum capacity) of the battery (B).

[0075] In this specification, SOC is expressed as a range of 0 to 1, where SOC 0 indicates a fully discharged state and SOC 1 indicates a fully charged state.

[0076] In this specification, when U is a variable, it is assumed that 'U[k-1]' represents the value of U from the previous cycle (previous period) and 'U[k]' represents the value of U from the current cycle. The symbol k used with the symbol [] is a time index that increases by 1 each time a predetermined set time (Δt, e.g., 0.001 seconds) elapses from the initial time point t0.

[0077] At the initial time point t0, k can be set to 0. For example, k = 10 indicates that time of Δt × 10 has elapsed since the initial time point t0, and that the SOC estimate value has been calculated 10 times during that time. The initial time point t0 is the time point at which a predetermined event occurs, for example, the time point at which an event occurs in which the control unit (130) switches from a sleep state to a wake-up state. The control unit (130) can switch from a sleep state to a wake-up state in response to the electric vehicle (1) being turned on, and switch from a wake-up state to a sleep state in response to the electric vehicle (1) being turned off.

[0078] From now on, the equivalent circuit model and SOC-OCV curve used by the extended Kalman filter will be described. Equations 1 through 8 below relate to the extended Kalman filter, and in explaining each of Equations 1 through 8, repeated descriptions of variables that have already been explained may be omitted.

[0079] The extended Kalman filter uses a state equation (see Equations 4-1 and 4-2 below) that includes SOC and polarization voltage as state variables, respectively, and Equation 1 below represents the relationship between SOC and battery current by ampere counting.

[0080] <Formula 1>

[0081]

[0082] In Equation 1, I[k-1] is the battery current measured in the previous cycle, Q i ε is the maximum capacity of the battery (B), SOC[k-1] is the SOC of the previous cycle, and SOC[k] is the SOC of the current cycle. I[0] = 0 A. Q i represents the maximum amount of charge that can be stored in the battery (B). That is, the maximum capacity Q iThe value is equal to the integrated value of the battery current from either the fully charged state or the fully discharged state of the battery (B) to the other.

[0083] FIG. 2 is a diagram showing an example of an equivalent circuit model (200) for the battery (B) shown in FIG. 1, and FIG. 3 is a diagram showing an exemplary SOC-OCV curve of the battery (B) shown in FIG. 1.

[0084] Referring to FIG. 2, the equivalent circuit model (200) includes a voltage source (210) and a resistor (R DC ) and RC pair(R P , C P Includes ).

[0085] Output voltage (V) of the voltage source (210) OCV ) represents the OCV of the battery (B) maintained in idle mode for a long time. The SOC and OCV of the battery (B) have a non-linear positive correlation. That is, f OCV and f SOC Assuming they are mutual inverse functions, OCV = f OCV (SOC), SOC = f SOC (OCV).

[0086] FIG. 3 illustrates two SOC-OCV curves (310, 320). The SOC-OCV curve (310) represents the change in OCV of the battery (B) in a constant current charging mode at a predetermined current rate, and the SOC-OCV curve (320) represents the change in OCV of the battery (B) in a constant current discharge mode at a predetermined current rate. At the same SOC, the OCV of the SOC-OCV curve (310) is slightly higher than the OCV of the SOC-OCV curve (320), and this difference is due to hysteresis of the battery (B) caused by the constant current charging mode and the constant current discharge mode.

[0087] Referring to FIG. 3, the two SOC-OCV curves (310, 320) are illustrated as having two voltage flat sections (331, 332) spaced apart from each other with a voltage inflection section (311, 321) in between. The voltage flat section (331) of the low SOC is z A ~z B And, the voltage flat section (302) of high SOC is z C ~z D Unlike the two voltage flat sections (331, 332), in the voltage inflection section (311, 321), the rate of change of OCV with respect to SOC (which may be an absolute value) may be greater than a threshold value.

[0088] Resistance (R DC ) is the IR drop (V) of the battery (B). DC It is related to ). IR drop(V DC ) is an instantaneous change in the battery voltage of the battery (B) due to the battery current. The memory section (130) includes SOC, temperature, and resistance (R DC A first lookup table defining a correspondence relationship between ) may be recorded, and the control unit (130) retrieves from the first lookup table a resistor (R) corresponding to the SOC and temperature of the previous (or current) cycle. DC ) can be determined.

[0089] RC pairs are resistors (R P ) and capacitor(C P Referring to a parallel circuit of ), the polarization voltage of the battery (B) (which may also be referred to as 'overpotential') (V P It is related to ). The time constant of an RC pair is the resistance (R P ) and capacitor(C P It is the product of ). In the memory section (130), SOC, temperature and RC pair (R P , C P A second lookup table defining the correspondence relationship between ) may be recorded. The control unit (130) retrieves from the second lookup table the resistance (R) corresponding to the SOC and temperature of the previous (or current) cycle.P ) and capacitor(C P Can determine ). Resistance (R P ) and capacitor(C P Determining ) means resistance (R P The resistance value of ) and the capacitor (C P This may mean determining the capacitance of ).

[0090] V ecm ε is a variable representing the voltage across the terminals of the equivalent circuit model (200), and can represent the predicted value of the battery voltage of the battery (B). As shown in Equation 2-1 below, V ecm is the output voltage (V OCV ), IR drop(V DC ) and polarization voltage (V P It can be expressed as the sum of ).

[0091] <Equation 2-1>

[0092]

[0093] In Equation 2-1, R DC [k] is the resistance of the current meeting (R DC The resistance value of ), I[k] is the battery current measured in the current trial, V OCV [k] is the estimated OCV of the current meeting, V P [k] is the estimated value of the polarization voltage of the current trial. Equation 2-1 can be expressed as Equation 2-2 below.

[0094] <Equation 2-2>

[0095]

[0096] In Equation 2-2, C[k] is a system matrix with two components, c[k] and 1. c[k] is the function f OCV V from SOC[k] according to OCV It is the conversion factor to [k]. That is, the product of c[k] and SOC[k] is V OCV It is the same as [k].

[0097] In the equivalent circuit model (200), the polarization voltage (VP ) can be calculated (estimated) using Equation 3-1 or Equation 3-2 below.

[0098] <Equation 3-1>

[0099]

[0100] <Equation 3-2>

[0101]

[0102] In Equations 3-1 and 3-2, V P [k] is the polarization voltage of the current trial, V P [k-1] is the previous polarization voltage, τ is the RC pair (R P , C P The time constant of ), R P [k] Current meeting's resistance (R P It represents the resistance value of ). τ is R P [k-1] and R P One of [k] and C P [k-1] and C P It can be the product of one of [k]. V P [0] can be set to 0 V.

[0103] The extended Kalman filter will now be described in detail. The state equation of the extended Kalman filter can be expressed as Equation 4-1 or Equation 4-2 below. Equation 4-1 is related to Equation 1 and Equation 3-1, and Equation 4-2 is related to Equation 1 and Equation 3-2.

[0104] <Equation 4-1>

[0105]

[0106] <Equation 4-2>

[0107]

[0108] In Formulas 4-1 and 4-2, SOC ^ [k-1] is the SOC, V estimated in the previous round P^ [k-1] is the polarization voltage estimated in the previous step, Q iε is the maximum capacity of the battery (B), and τ is the RC pair (R P , C P Represents the time constant of ). x ^ - [k] is the state matrix of the current meeting, and the SOC included therein ^ - [k] and V P^ - [k] are state variables representing the predicted SOC and polarization voltage for the current cycle, respectively.

[0109] The following Equation 5 is the time update equation of the extended Kalman filter.

[0110] <Equation 5>

[0111]

[0112] In Equation 5, P[k-1] is the error covariance matrix estimated in the previous iteration, W is the process noise covariance matrix, and P - [k] represents the error covariance matrix predicted for the current round. A1 in Equation 5 is the Jacobian of the function f1 in Equations 4-1 and 4-2. The Jacobian (A1) can be expressed as shown in Equation 5-1 below.

[0113] <Equation 5-1>

[0114]

[0115] A1 T is the transpose matrix of A1. At k=0, P[0]=[ 1 0 ; 0 1 ]. The control unit (130) executes a measurement update process when the time update process using Equation 4-1 or Equation 4-2 and Equation 5 is completed.

[0116] The following Equation 6 is the first measurement update equation of the extended Kalman filter.

[0117] <Equation 6>

[0118]

[0119] In Equation 6, K[k] is the Kalman gain of the current iteration, H1 is the Jacobian of the function h1 according to Equation 6-1 below, H1 T is the transpose of H1, and L is the measurement noise covariance matrix.

[0120] In relation to Equation 6, the state matrix (x ^ - By associating [k]) with Equation 2-1, a battery voltage prediction equation (output equation) such as Equation 6-1 below can be derived.

[0121] <Equation 6-1>

[0122]

[0123] The Jacobian (H1) of Equation 6 can be expressed as shown in Equation 6-2 below.

[0124] <Equation 6-2>

[0125]

[0126] The following Equation 7 is the second measurement update equation of the extended Kalman filter.

[0127] <Equation 7>

[0128]

[0129] In Equation 7, P[k] is P from Equation 5 - [k] is the result corrected by Equation 7.

[0130] The following Equation 8 is the third measurement update equation of the first extended Kalman filter.

[0131] <Equation 8>

[0132]

[0133] In Equation 8, z[k] is the battery voltage measured in the current trial, z ^ [k] is the battery voltage and SOC estimated at the current meeting ^[k] is the SOC estimated in the current meeting (representing the 'provisional SOC' of the claim scope), V P^ [k] is the polarization voltage estimated in the current trial. x according to Equation 8 ^ [k] is x in Equation 4 in the next session. ^ It can be used as [k-1].

[0134] When the extended Kalman filter is executed by the control unit (130), an estimated SOC value representing the current SOC of the battery (B) is output from the extended Kalman filter according to the process described above.

[0135] From now on, we will first explain the constant current stimulation map, and then explain the extended Kalman filter in detail.

[0136] FIG. 4 is a drawing referenced to explain a constant current stimulation map according to the present invention. The constant current stimulation map (400) includes a plurality of voltage profiles (411–416) associated with a charging mode and a plurality of voltage profiles (421–426) associated with a discharging mode.

[0137] Multiple voltage profiles (411–416) are associated with different current indicators, and each of the multiple voltage profiles (411–416) represents the CCV for the SOC of the battery (B) in a constant current charging mode. The current indicator may refer to a single current rate (which may be called a 'C-rate') or a range of current rates. CCV may be a term referring to the battery voltage of the battery (B) measured during charging or discharging. In a constant current charging mode, the higher the current rate, the greater the CCV at the same SOC.

[0138] Multiple voltage profiles (421 to 416) are also associated with different current indicators, and each of the multiple voltage profiles (411 to 416) represents the CCV for the SOC of the battery (B) in constant current discharge mode. During constant current discharge mode, the higher the current rate, the smaller the CCV at the same SOC.

[0139] Six of the multiple voltage profiles (411–416) and multiple voltage profiles (421–416) are each shown, and the current rates are 0.05 C, 0.15 C, 0.25 C, 0.50 C, 1.00 C, and 1.50 C in order of magnitude. For example, two voltage profiles (411, 421) are associated with 0.05 C, and two voltage profiles (413, 423) are associated with 0.25 C.

[0140] Each profile included in the constant current stimulation map (400) can be stored in the memory unit (131) in the form of a mathematical function and / or a data table.

[0141] For better understanding, FIG. 4 illustrates the two SOC-OCV curves (310, 320) of FIG. 3 along with multiple voltage profiles (411–416) and multiple voltage profiles (421–416). As can be seen from FIG. 4, as the current rate used for the progression of the constant current charging mode increases, the voltage flatness characteristic in the voltage flat section of the SOC-OCV curve (310) gradually disappears. Similarly, as the current rate used for the progression of the constant current discharge mode increases, the voltage flatness characteristic in the voltage flat section of the SOC-OCV curve (320) also gradually disappears.

[0142] As previously mentioned, it is by no means easy to design an equivalent circuit model (200) to fully describe the so-called fading characteristic in which the voltage flat region disappears as the current rate increases. Furthermore, the SOC estimated based on the output value of an equivalent circuit model (200) that fails to describe the fading characteristic beyond a certain level may have a large error compared to the actual SOC.

[0143] Accordingly, during the application period of the constant current stimulation, the control unit (130) can estimate the SOC of the battery (B) based not only on the output value of the extended Kalman filter and / or ampere counting, but also on the output value of the SOC estimation model based on the constant current stimulation map (400), thereby resolving the aforementioned problem to a significant extent.

[0144] As the battery (B) degrades, its maximum capacity gradually decreases. Therefore, since there is a very high possibility that a battery (B) whose degree of degeneration exceeds a certain level will suddenly become unusable, it is necessary to estimate the SOC more precisely.

[0145] FIG. 5 is a flowchart illustrating an exemplary battery management method according to an embodiment of the present invention. The method of FIG. 5 may be repeated at set intervals starting from the time when a predetermined event occurs.

[0146] Referring to FIGS. 1 to 5, in step S510, the control unit (130) measures the battery voltage value (V[k]) and battery current value (I[k]) of the battery (B) using the sensing unit (111, 113).

[0147] In step S520, the control unit (130) estimates a temporary SOC based on the battery voltage value (V[k]) and the battery current value (I[k]). The temporary SOC can be said to be a candidate value representing the SOC of the battery (B).

[0148] The aforementioned extended Kalman filter may be used for estimating the temporary SOC. The extended Kalman filter is an SOC estimation model that utilizes an equivalent circuit model (200) of the battery (B) and an SOC-OCV curve (300). The battery voltage value (V[k]) may be used as z[k] in Equation 8. If the battery current value (I[k]) indicates the charging direction, the control unit (130) may provide the SOC-OCV curve (310) among the two SOC-OCV curves (310, 320) to the extended Kalman filter. On the other hand, if the battery current value (I[k]) indicates the discharging direction, the control unit (130) may provide the SOC-OCV curve (320) among the two SOC-OCV curves (310, 320) to the extended Kalman filter.

[0149] In step S530, the control unit (130) determines whether a constant current stimulus is being applied to the battery (B) based on the battery current value (I[k]). If the value of step S530 is "yes", the process proceeds to step S540. If the value of step S530 is "no", the process proceeds to step S560.

[0150] For example, the control unit (130) can determine that a constant current stimulus is being applied to the battery (B) if the amount of change in current based on the battery current value (I[k]) is within a predetermined reference range (e.g., -0.0002 A to +0.002 A). The amount of change in current may represent the difference between the battery current value (I[k]) and the previous battery current value (I[k-1]).

[0151] As another example, the control unit (130) can determine that a constant current stimulus is being applied to the battery (B) when the maximum deviation (the difference between the maximum and minimum values) of the battery current time series (including the battery current value (I[k]) as the final value) representing the history of changes in the battery current value over a certain period of time is within a predetermined reference range (e.g., -0.0002 A to +0.002 A) and the rate of change of the battery current time series is within a predetermined reference range (e.g., -0.001 A / s to +0.001 A / s).

[0152] In step S540, the control unit (130) determines a reference SOC range from a reference voltage profile based on a battery voltage value (V[k]). Step S540 will be described in more detail below with reference to FIGS. 6 and FIGS. 7.

[0153] In step S550, the control unit (130) determines the confirmed SOC of the battery (B) based on a comparison of the temporary SOC and the reference SOC range. The confirmed SOC can be said to be a candidate value representing the SOC of the battery (B), and may be the same as or different from the temporary SOC. Step S550 will be described in more detail below with reference to FIGS. 7 to 10.

[0154] In step S560, the control unit (130) determines the fixed SOC of the battery (B) to be the same as the temporary SOC.

[0155] The control unit (130) can control the charging or discharging of the battery (B) based on the determined fixed SOC.

[0156] The control unit (130) can control the charger (3) to stop charging the battery (B) when the confirmed SOC reaches the upper limit of a predetermined allowable SOC range during the charging of the battery (B). For example, the control unit (130) can physically block the power path between the battery group (11) and the charger (3) by outputting a switch-off signal to the relay (20).

[0157] The control unit (130) can control the inverter (30) to stop discharging the battery (B) when the confirmed SOC reaches the lower limit of a predetermined allowable SOC range during the discharge of the battery (B).

[0158] The control unit (130) can reduce the maximum charging current of the battery (B) as the confirmed SOC approaches the upper limit of a predetermined allowable SOC range during charging of the battery (B). The maximum charging current may have a predetermined positive relationship with the difference between the confirmed SOC and the upper limit of the predetermined allowable SOC range.

[0159] The control unit (130) can reduce the maximum discharge current of the battery (B) as the positive SOC approaches the lower limit of a predetermined allowable SOC range during the discharge of the battery (B). The maximum discharge current may have a predetermined positive relationship with the difference between the positive SOC and the lower limit of a predetermined allowable SOC range.

[0160] Here, instructions, data, and / or programs required for charging or discharging the battery (B), such as an allowable SOC range, may be pre-recorded in the memory unit (131).

[0161] FIG. 6 is a flowchart illustrating an example of subroutines that can be included in step S540 of FIG. 5, and FIG. 7 is an exemplary graph referenced to explain the method of FIG. 6.

[0162] Referring to FIGS. 6 and FIGS. 7, in step S610, the control unit (130) measures the battery voltage value (V[k]) and the voltage measurement error (ΔV error Based on ), the reference voltage interval (SV R Determines ).

[0163] Voltage measurement error (ΔV error ) may be predetermined based on at least one of the performance indicators (e.g., measurement accuracy, resolution) of the voltage sensor (111).

[0164] Reference voltage range (SV R) is the voltage value (V R1 From ) voltage value (V R2 It can be a voltage range up to ). Voltage value (V R1 ) is the voltage measurement error (ΔV) compared to the battery voltage value (V[k]). error It is smaller by ), and the voltage value (V R2 ) is the voltage measurement error (ΔV) compared to the battery voltage value (V[k]). error It is as big as )

[0165] In step S620, the control unit (130) reads out one voltage profile included in the constant current stimulation map (400) as a reference voltage profile (700) based on the battery current value (I[k]). That is, among the voltage profiles (411~416, 421~426) of the constant current stimulation map (400), one voltage profile associated with a current index corresponding to the battery current value (I[k]) is selected as the reference voltage profile (700).

[0166] In step S630, the control unit (130) in the reference voltage profile (700) reference voltage interval (SV R The SOC interval mapped to ) is the reference SOC interval (SZ R Decide as ).

[0167] Referring to Fig. 7, the reference SOC section (SZ R Lower bound of ) SOC(z R1 ) is the voltage value (V R1 It is the SOC of the reference voltage profile (700) mapped to ). Likewise, the reference SOC interval (SZ R Upper limit of SOC(z) R2 ) is the voltage value (V R2 It is the SOC of the reference voltage profile (700) mapped to ). That is, the reference SOC interval (SZ R ) is z R1 from z R2 It is the SOC range up to.

[0168] FIG. 8 is a flowchart illustrating an example of subroutines that can be included in step S550 of FIG. 5.

[0169] Referring to FIGS. 7 and FIGS. 8, in step S810, the control unit (130) determines that the temporary SOC is in the reference SOC interval (SZ R Determines whether it is within ). In Fig. 7, the temporary SOC is z A If so, the value of step S810 is output as "Yes". If the value of step S810 is "Yes", proceed to step S820. If the value of step S810 is "No", the temporary SOC is in the reference SOC interval (SZ R Lower bound of ) SOC(z R1 SOC(z) smaller than or upper than ) R2 It means that it is greater than ). In Fig. 7, the temporary SOC is z B or z C If the value of step S810 is "No", the output is "No". If the value of step S810 is "No", proceed to step S830.

[0170] In step S820, the control unit (130) determines the fixed SOC of the battery (B) to be the same as the temporary SOC.

[0171] In step S830, the control unit (130) has a lower limit SOC (z R1 ) or upper limit SOC(z R2 The confirmed SOC of the battery (B) is determined in the same way as ). For example, the temporary SOC is the lower limit SOC (z R1 If it is smaller than ), the confirmed SOC is the lower bound SOC(z R1 It can be determined to be the same as ), and the temporary SOC is the upper limit SOC(z R2 If it is greater than ), the confirmed SOC is the upper limit SOC(z R2 It can be determined in the same way as ). That is, a value different from the temporary SOC is determined as the final SOC, and this is because the SOC estimate value (i.e., temporary SOC) by the first SOC estimation model based on an extended Kalman filter is corrected by the second SOC estimation model based on a constant current stimulation map (400), and the corrected SOC estimate value is the final SOC.

[0172] FIG. 9 is a flowchart illustrating another example of subroutines that can be included in step S550 of FIG. 5. The method according to FIG. 9 may correspond to a variation of the method according to FIG. 8.

[0173] Referring to FIGS. 7 and FIGS. 9, in step S910, the control unit (130) determines that the temporary SOC is in the reference SOC interval (SZ R Determine whether it is within ). If the value of step S910 is "Yes", proceed to step S920. If the value of step S910 is "No", proceed to step S930. Step S910 is substantially the same as step S810.

[0174] In step S920, the control unit (130) determines the fixed SOC of the battery (B) as the same as the temporary SOC. Step S920 is substantially the same as step S820.

[0175] In step S930, the control unit (130) has a temporary SOC and a lower limit SOC (z R1 The difference in SOC between ) or temporary SOC and upper limit SOC(z R2 Calculate the difference in SOC between ).

[0176] Temporary SOC is lower limit SOC(z R1 If it is smaller than ), temporary SOC and lower bound SOC(z R1 The SOC difference between ) can be calculated. For example, in FIG. 7, the temporary SOC is z B Ramen, z B wa z R1 The difference can be calculated as the SOC difference in step S930.

[0177] Temporary SOC is upper limit SOC(z R2 If greater than ), temporary SOC and upper limit SOC(z R2 The SOC difference between ) can be calculated. For example, in FIG. 7, the temporary SOC is z C Ramen, z C wa z R2 The difference can be calculated as the SOC difference in step S930.

[0178] In step S932, the control unit (130) determines a correction value based on the SOC difference calculated in step S930.

[0179] The control unit (130) can determine the correction value by multiplying the SOC difference by a correction ratio. For example, the temporary SOC is z B Ramen, correction value = (z R1 - z B ) × Correction ratio. As another example, the temporary SOC is z C Ramen, correction value = (z C - z R2 ) × Correction ratio.

[0180] In one embodiment, the calibration ratio may be predetermined as a positive number less than 1. Therefore, the greater the difference in SOC, the larger the calibration value may be.

[0181] In another embodiment, the calibration ratio is the reference SOC interval (SZ R It can be determined dependently on the size (width) of ). Reference SOC interval (SZ R The size of ) is the lower limit SOC(z R1 ) and upper limit SOC(z R2 It can represent the difference in SOC between ).

[0182] More specifically, the standard SOC section (SZ R The narrowness of ) is the standard SOC section (SZ R This indicates that the voltage change rate of the reference voltage profile (700) in ) is large, which is the reference SOC interval (SZ R This means that most of ) is likely outside the voltage flat region (331, 332). Conversely, the reference SOC region (SZ R The wideness of ) is the standard SOC section (SZ R This indicates that the voltage change rate of the reference voltage profile (700) in ) is small, which is the reference SOC interval (SZ RThis means that most of ) is likely to overlap with the voltage flat sections (331, 332). Therefore, the control unit (130) has a reference SOC section (SZ R The correction ratio can be determined by applying a predetermined negative correspondence to the size of ). That is, the reference SOC interval (SZ R The smaller the size of ), the larger the correction ratio, and the reference SOC range (SZ R The larger the size of ), the smaller the correction ratio may be.

[0183] In step S934, the control unit (130) determines the final SOC by applying the correction value determined in step S932 to the temporary SOC.

[0184] Temporary SOC is lower limit SOC(z R1 If it is smaller than ), the final SOC can be determined to be equal to the value obtained by summing the correction value to the temporary SOC. For example, in Fig. 7, z B' is, temporary SOC is z B In this case, it represents the confirmed SOC determined in step S934.

[0185] Temporary SOC is upper limit SOC(z R2 If it is greater than ), the final SOC can be determined as equal to the value obtained by subtracting the correction value from the temporary SOC. For example, in Fig. 7, z C' is, temporary SOC is z C In this case, it represents the confirmed SOC determined in step S934.

[0186] Another embodiment of the present invention may provide a computer-readable medium having a program recorded thereon for executing the various embodiments described above on a computer.

[0187] A program may be implemented as hardware components, software components, and / or a combination of hardware and software components. A program may be executed by any system capable of executing computer-readable instructions.

[0188] Software may include computer programs, code, instructions, or a combination thereof, and may configure a processing unit to operate as desired or command the processing unit independently or collectively.

[0189] Software can be implemented as a computer program containing instructions stored on a computer-readable storage medium. Examples of computer-readable storage media include magnetic storage media (e.g., ROM (read-only memory), RAM (random-access memory), floppy disks, hard disks, etc.) and optical reading media (e.g., CD-ROMs, DVDs (Digital Versatile Discs)). Computer-readable storage media can be distributed across networked computer systems, allowing computer-readable code to be stored and executed in a distributed manner. The storage medium is readable by a computer, stored in memory, and can be executed by a processor.

[0190] Computer-readable media may be provided in the form of non-transitory recording media. Here, 'non-transitory storage media' simply means that it is a tangible device and does not contain a signal (e.g., electromagnetic waves), and the term does not distinguish between cases where data is stored semi-permanently and cases where it is stored temporarily. For example, 'non-transitory storage media' may include a buffer in which data is stored temporarily.

[0191] In addition, the program may be provided as part of a computer program product. Computer program products may be traded between a seller and a buyer as goods.

[0192] A computer program product may include a software program or a computer-readable recording medium on which the software program is stored. For example, a computer program product may include a product in the form of a software program that is distributed electronically through a manufacturer of an electronic device or an electronic market (e.g., a downloadable application). For electronic distribution, at least a portion of the software program may be stored on a recording medium or temporarily created. In this case, the recording medium may be a server of the manufacturer of the electronic device, a server of the electronic market, or a recording medium of a relay server that temporarily stores the software program.

[0193] The embodiments of the present invention described above are not limited to implementation through devices and methods, but may also be implemented through a program that realizes a function corresponding to the configuration of the embodiments of the present invention or a recording medium on which such a program is recorded. Such implementation can be easily achieved by a person skilled in the art to which the present invention pertains, based on the description of the embodiments described above.

[0194] Although the present invention has been described above by limited embodiments and drawings, the present invention is not limited thereto, and it is obvious that various modifications and variations are possible within the scope of the technical spirit of the present invention and the equivalent scope of the claims described below by those skilled in the art to which the present invention belongs.

[0195] Furthermore, since the present invention described above allows for various substitutions, modifications, and changes within the scope of the technical concept of the present invention to those skilled in the art without departing from the technical spirit of the present invention, it is not limited by the aforementioned embodiments and attached drawings, but rather all or part of each embodiment may be selectively combined to allow for various modifications.

Claims

1. A sensing unit configured to measure the battery voltage value and battery current value of the battery; and It includes a control unit configured to estimate the temporary SOC of the battery based on the battery voltage value and the battery current value, and The above control unit is, When it is determined that a constant current stimulus is being applied to the battery based on the battery current value, a reference SOC interval is determined from a reference voltage profile based on the battery voltage value, and A battery management system configured to determine the confirmed SOC of the battery based on a comparison of the above temporary SOC and the above reference SOC range.

2. In Paragraph 1, The above control unit is, A battery management system configured to determine that a constant current stimulus is being applied to the battery when the amount of current change based on the battery current value is within a reference range.

3. In Paragraph 1, The above control unit is, A battery management system configured to select, among a plurality of voltage profiles associated with different current indicators, one voltage profile corresponding to the battery current value as the reference voltage profile.

4. In Paragraph 1, The above control unit is, Based on the above battery voltage value and voltage measurement error, a reference voltage range is determined, and A battery management system configured to determine the SOC range mapped to the reference voltage range in the above reference voltage profile as the above reference SOC range.

5. In Paragraph 1, The above control unit is, A battery management system configured to determine the confirmed SOC in the same way as the temporary SOC when the temporary SOC is within the reference SOC range.

6. In Paragraph 1, The above control unit is, A battery management system configured to determine the confirmed SOC based on the SOC difference between the temporary SOC and the lower limit SOC when the temporary SOC is less than the lower limit SOC of the reference SOC range.

7. In Paragraph 6, The above control unit is, Based on the size of the above standard SOC range, determine the correction ratio, and The correction value is determined by multiplying the above SOC difference by the above correction ratio, and A battery management system configured to determine the confirmed SOC by applying the above correction value to the above temporary SOC.

8. In Paragraph 7, The above control unit is, A battery management system configured to determine the correction ratio by applying a predetermined negative correspondence to the size of the above reference SOC range.

9. In Paragraph 1, The above control unit is, A battery management system configured to determine the confirmed SOC based on the SOC difference between the temporary SOC and the upper SOC when the temporary SOC exceeds the upper SOC of the reference SOC range.

10. A battery pack comprising a battery management system according to any one of paragraphs 1 through 9.

11. An electric vehicle including a battery pack pursuant to Paragraph 10.

12. Step of measuring the battery voltage and battery current values ​​of the battery; A step of estimating the temporary SOC of the battery based on the battery voltage value and the battery current value; When it is determined that a constant current stimulus is being applied to the battery based on the battery current value, a step of determining a reference SOC section from a reference voltage profile based on the battery voltage value; and A step of determining the confirmed SOC of the battery based on a comparison of the above temporary SOC and the above reference SOC range; A battery management method including 13. In Paragraph 12, The step of determining the above-mentioned standard SOC range is, A step of determining a reference voltage range based on the above battery voltage value and voltage measurement error; and A step of determining the SOC section mapped to the reference voltage section in the above reference voltage profile as the above reference SOC section; A battery management method including 14. In Paragraph 12, In the step of determining the confirmed SOC of the above battery, A battery management method for determining the confirmed SOC based on the difference in SOC between the temporary SOC and the upper limit SOC when the temporary SOC exceeds the upper limit SOC of the reference SOC range.

15. In Paragraph 12, In the step of determining the confirmed SOC of the above battery, A battery management method for determining the confirmed SOC based on the difference in SOC between the temporary SOC and the lower limit SOC when the temporary SOC is less than the lower limit SOC of the reference SOC range.

16. A computer-readable medium storing a program for executing a battery management method according to any one of paragraphs 12 through 15 on a computer.

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