Battery management system, battery pack, electric vehicle, and battery management method

Abstract

The invention provides a battery management system, a battery pack, an electric vehicle, and a battery management method. The battery management system includes: a sensing unit for detecting a terminal voltage and a charge / discharge current of a battery having a characteristic in which a voltage change section changes according to a current rate; a memory unit for storing a first Kalman filter using an equivalent circuit model and a state of charge (SOC)-open circuit voltage curve of the battery and a second Kalman filter using a constant current charge / discharge map of the battery; and a control unit for determining a first estimated SOC by inputting the voltage value of the terminal voltage, the current value of the charge / discharge current, and the estimated SOC in the previous cycle to a first Kalman filter, and determining a second estimated SOC by inputting the current value and the estimated SOC in the previous cycle to a second Kalman filter.

Description

Technical Field

[0001] The present disclosure relates to state of charge estimation in a battery.

[0002] This application claims priority to Korean Patent Application No. 10-2023-0082153 filed in Korea on June 26, 2023, the disclosure of which is incorporated herein by reference. Background Art

[0003] In recent years, the demand for portable electronic products such as laptop computers, cameras, and mobile phones has increased dramatically, and with the widespread development of electric vehicles, secondary batteries for energy storage, robots, and satellites, much research is being conducted on high-performance batteries that can be repeatedly recharged.

[0004] Currently, commercially available batteries include nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, lithium batteries, etc., and among them, lithium batteries have no or almost no memory effect, and therefore lithium batteries have gained more attention than nickel-based batteries due to their advantages of being able to be recharged at any convenient time, having a very low self-discharge rate, and having a 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 indicating the relative ratio of the current capacity to the maximum capacity indicating the total electrical energy when the battery is fully charged, and SOC can be expressed as 0 to 1 (or 0% to 100%). For example, when the maximum capacity of the battery is 1000Ah (ampere-hour) and the capacity currently stored in the battery is 750Ah, the SOC of the battery is 0.75 (or 75%).

[0006] To estimate the SOC of the battery, the Extended Kalman Filter (EKF) is widely used.

[0007] The extended Kalman filter is an SOC estimation logic that uses an equivalent circuit model (ECM) and an SOC-open circuit voltage (OCV) curve each prepared in advance according to the electrical and chemical properties of a battery, and outputs an estimated SOC as one of state variables when the voltage and current of the battery are input as input variables.

[0008] Meanwhile, some types of batteries, such as lithium iron phosphate (LFP) batteries, have a voltage variation section in the SOC-OCV curve. The SOC-closed circuit voltage (CCV) curve obtained by repeatedly measuring the terminal voltage of the battery in a constant current charge mode and / or a constant current discharge mode has a less obvious voltage variation section than the SOC-OCV curve. As the current rate is greater, the voltage variation section gradually disappears or disappears completely.

[0009] In order to fully reflect the characteristics of the voltage variation section of the battery on the EKF, it is necessary to accurately design the ECM. However, as the design accuracy of the ECM increases, the number of devices included in the ECM also increases, and the connection relationship between the devices becomes complicated, resulting in an increase in the complexity of SOC estimation and the required data storage space. In addition, despite the high design accuracy of the ECM, it is difficult to fully reflect the voltage variation section that changes according to the current rate.

[0010] In order to solve the problem caused by the ECM constraint, a method of estimating the SOC of the battery using ampere counting instead of EKF in a constant current charge / discharge mode can be foreseen. Ampere counting refers to a technique for estimating the SOC of a battery by converting the accumulated value of the current flowing through the battery into a change in SOC. However, when the constant current charge / discharge mode continues for a long time, the current measurement error also accumulates over time, resulting in low accuracy of the SOC estimation by ampere counting. Summary of the invention

[0011] Technical issues

[0012] The present disclosure is designed to solve the above-mentioned problems, and therefore the present disclosure relates to a battery pack for estimating the charging state of a battery having a characteristic in which a voltage variation section changes according to a current rate by using two extended Kalman filters having a complementary relationship in parallel, an electric vehicle including the battery pack, and a battery management method.

[0013] These and other purposes and advantages of the present disclosure can be understood through the following description and will be apparent from the embodiments of the present disclosure.In addition, it will be easily understood that the purposes and advantages of the present disclosure can be achieved by the means set forth in the appended claims and combinations thereof.

[0014] Technical Solution

[0015] A battery management system according to one aspect of the present disclosure is used for a battery having a characteristic that a voltage variation section changes according to a current rate. The battery management system includes: a sensing unit configured to detect a terminal voltage and a charge / discharge current of a battery; a memory unit configured to store a first Kalman filter and a second Kalman filter, the first Kalman filter being an SOC estimation logic using an equivalent circuit model of a battery and a state of charge (SOC)-open circuit voltage (OCV) curve, and the second Kalman filter being an SOC estimation logic using a constant current charge / discharge diagram of a battery; and a control unit configured to determine a voltage value of the detected terminal voltage and a current value of the detected charge / discharge current. The control unit is configured to determine a first estimated SOC by inputting a voltage value, a current value, and an estimated SOC in a previous cycle to the first Kalman filter, and to determine a second estimated SOC by inputting a current value and an estimated SOC in a previous cycle to the second Kalman filter. The control unit is configured to determine the SOC of the battery in the current cycle based on at least one of the first estimated SOC and the second estimated SOC.

[0016] The control unit may be configured to determine whether the battery is in a first state in which the battery is not being charged / discharged at a constant current or a second state in which the battery is being charged / discharged at a constant current based on the current value or current time series data indicating a time-dependent change history of the charge / discharge current. The control unit may be configured to determine the SOC of the battery in the current cycle to be equal to the first estimated SOC in response to determining that the battery is in the first state. The control unit may be configured to determine the SOC of the battery in the current cycle to be equal to the second estimated SOC in response to determining that the battery is in the second state.

[0017] The control unit may be configured to determine whether the battery is in a first state or a second state based on a current value or current time series data indicating a time-dependent change history of a charge / discharge current, in which the battery is not being charged / discharged at a constant current, and in which the battery is being charged / discharged at a constant current. The control unit may be configured to determine, in response to determining that the battery is in the first state, a first weight that is positively correlated with the duration of the first state and a second weight that is negatively correlated with the duration of the first state. The control unit may be configured to determine the SOC of the battery in the current cycle to be equal to a weighted average of a first estimated SOC and a second estimated SOC by the first weight and the second weight.

[0018] The first weight may be greater than the second weight. The sum of the first weight and the second weight may be 1.

[0019] The control unit may be configured to determine whether the battery is in a first state or a second state based on a current value or current time series data indicating a time-dependent change history of a charge / discharge current, in which the battery is not being charged / discharged at a constant current, and in which the battery is being charged / discharged at a constant current. The control unit may be configured to determine, in response to determining that the battery is in the second state, a third weight that is negatively correlated with the duration of the second state and a fourth weight that is positively correlated with the duration of the second state. The control unit may be configured to determine the first estimated SOC and the second estimated SOC as the SOC of the battery in the current cycle by a weighted average of the third weight and the fourth weight.

[0020] The third weight may be smaller than the fourth weight. The sum of the third weight and the fourth weight may be 1.

[0021] The constant current charge / discharge graph may include: a plurality of charge curves indicating the relationship between the SOC and voltage of the battery during constant current charging using a plurality of current rates; and a plurality of discharge curves indicating the relationship between the SOC and voltage of the battery during constant current discharging using a plurality of current rates.

[0022] In response to providing any one of the plurality of charging profiles and the plurality of discharging profiles to the second Kalman filter, a second estimated SOC may be output from the second Kalman filter.

[0023] The control unit may be configured to provide, to the second Kalman filter, any one of a plurality of charging curves associated with a current rate corresponding to the current value in response to the battery being charged at a constant current. The control unit may be configured to provide, to the second Kalman filter, any one of a plurality of discharging curves associated with a current rate corresponding to the current value in response to the battery being discharged at a constant current.

[0024] A battery pack according to another aspect of the present disclosure includes the battery management system.

[0025] An electric vehicle according to still another aspect of the present disclosure includes the battery pack.

[0026] A battery management method according to another aspect of the present disclosure is used for a battery having a characteristic that a voltage variation section changes according to a current rate. The battery management method includes: detecting a terminal voltage and a charge / discharge current of a battery; determining a voltage value of the detected terminal voltage and a current value of the detected charge / discharge current; determining a first estimated SOC by inputting a voltage value, a current value, and an estimated SOC in a previous cycle into a first Kalman filter, the first Kalman filter being an SOC estimation logic using an equivalent circuit model of a battery and an SOC-OCV curve; determining a second estimated SOC by inputting a current value and an estimated SOC in a previous cycle into a second Kalman filter, the second Kalman filter being an SOC estimation logic using a constant current charge / discharge diagram of a battery; and determining the SOC of the battery in a current cycle based on at least one of the first estimated SOC and the second estimated SOC.

[0027] Determining the SOC of a battery in a current cycle may include: determining whether the battery is in a first state or a second state based on a current value or current time series data indicating a time-related change history of a charge / discharge current, in which the battery is not being charged / discharged at a constant current, and in which the battery is being charged / discharged at a constant current; in response to determining that the battery is in the first state, determining a first estimated SOC as the SOC of the battery in the current cycle; and in response to determining that the battery is in the second state, determining a second estimated SOC as the SOC of the battery in the current cycle.

[0028] Determining the SOC of a battery in a current cycle may include: determining whether the battery is in a first state or a second state based on a current value or current time series data indicating a time-related change history of a charge / discharge current, in which the battery is not being charged / discharged at a constant current, and in which the battery is being charged / discharged at a constant current; in response to determining that the battery is in the first state, determining a first weight that is positively correlated with a duration of the first state and a second weight that is negatively correlated with a duration of the first state; and determining the first estimated SOC and the second estimated SOC as the SOC of the battery in the current cycle by a weighted average of the first weight and the second weight.

[0029] Determining the SOC of a battery in a current cycle may include: determining whether the battery is in a first state or a second state based on a current value or current time series data indicating a time-related change history of a charge / discharge current, in which the battery is not being charged / discharged at a constant current, and in which the battery is being charged / discharged at a constant current; in response to determining that the battery is in the second state, determining a third weight that is negatively correlated with a duration of the second state and a fourth weight that is positively correlated with a duration of the second state; and determining the first estimated SOC and the second estimated SOC as the SOC of the battery in the current cycle by a weighted average of the third weight and the fourth weight.

[0030] The constant current charge / discharge graph may include: a plurality of charge curves indicating the relationship between the SOC and voltage of the battery during constant current charging using a plurality of current rates; and a plurality of discharge curves indicating the relationship between the SOC and voltage of the battery during constant current discharging using a plurality of current rates.

[0031] In response to providing any one of the plurality of charging profiles and the plurality of discharging profiles to the second Kalman filter, a second estimated SOC may be output from the second Kalman filter.

[0032] Beneficial Effects

[0033] According to at least one embodiment of the present disclosure, two extended Kalman filters having a complementary relationship are used in parallel to estimate the SOC of a battery having a characteristic in which a voltage variation section changes according to a current rate, so as to reduce the SOC estimation error that changes with the charge / discharge mode of the battery compared to a single extended Kalman filter, thereby improving the SOC estimation accuracy.

[0034] The effects of the present disclosure are not limited to the above-described effects, and those skilled in the art will clearly understand these and other effects from the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings illustrate exemplary embodiments of the present disclosure and, together with the following detailed description, serve to provide a further understanding of the technical aspects of the present disclosure, and thus the present disclosure should not be construed as being limited to the accompanying drawings.

[0036] Figure 1 is a diagram exemplarily showing a configuration of an electric vehicle according to the present disclosure.

[0037] Figure 2 It is shown Figure 1 A diagram of an exemplary equivalent circuit model of a battery is shown in FIG.

[0038] Figure 3 It is shown exemplarily Figure 1FIG. 5 is a graph showing a state of charge (SOC)-open circuit voltage (OCV) curve of a battery.

[0039] Figure 4 is a graph used as a reference in describing a constant current charge / discharge graph according to the present disclosure.

[0040] Figure 5 is a flowchart exemplarily illustrating a battery management method for SOC estimation according to the first embodiment of the present disclosure.

[0041] Figure 6 is a flowchart exemplarily illustrating a battery management method for SOC estimation according to a second embodiment of the present disclosure.

[0042] Figure 7 is a flowchart exemplarily illustrating a battery management method for SOC estimation according to a third embodiment of the present disclosure.

[0043] Figure 8 is describing the Figure 7 Figure used as reference in the method.

[0044] Fig. 9 is a flowchart exemplarily illustrating a battery management method for SOC estimation according to a fourth embodiment of the present disclosure.

[0045] Fig.10 is describing the Fig. 9 Figure used as reference in the method.

[0046] Fig.11 is a flowchart exemplarily illustrating a battery management method for SOC estimation according to a fifth embodiment of the present disclosure.

[0047] Fig.12 is a flow chart exemplarily showing a method for determining whether a battery is being charged / discharged at a constant current. DETAILED DESCRIPTION

[0048] Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Before the description, it should be understood that the terms or words used in the specification and the appended claims should not be interpreted as limited to the general and dictionary meanings, but should be interpreted based on the meanings and concepts corresponding to the technical aspects of the present disclosure on the basis of the principle that the inventor is allowed to appropriately define the terms for the best interpretation.

[0049] Therefore, the embodiments described herein and the illustrations shown in the accompanying drawings are provided for describing exemplary embodiments of the present disclosure by way of example, and are not intended to fully describe the technical aspects of the present disclosure, and it should be understood that various other equivalents and modifications may have been made thereto when the present application is filed.

[0050] Terms including ordinal numbers such as “first,” “second,” etc. are used to distinguish one element from another element among various elements, but are not intended to limit the elements by the terms.

[0051] Unless the context clearly indicates otherwise, it should be understood that the term "comprising" when used in this specification specifies the presence of the stated elements, but does not exclude the presence or addition of one or more other elements. In addition, the term "control unit" as used herein refers to a processing unit having at least one function or operation, and can be implemented by hardware or software alone or in combination.

[0052] In addition, throughout the specification, it will also be understood that when an element is referred to as being “connected to” another element, it can be directly connected to the other element or intervening elements may be present.

[0053] Figure 1 is a diagram exemplarily showing a configuration of an electric vehicle according to the present disclosure.

[0054] The electric vehicle 1 includes a vehicle controller 2, a battery pack 10, a relay 20, an inverter 30, and a motor 40. The charging / discharging terminals P+, P- of the battery pack 10 may be electrically coupled to a charger 3 through a charging cable. The charger 3 may be included in the electric vehicle 1, or may be present at a charging station.

[0055] The vehicle controller 2 (e.g., an electronic control unit (ECU)) is configured to send a key-on signal to the battery management system 100 when the user switches a start button (not shown) of the electric vehicle 1 to the on position. The vehicle controller 2 is configured to send a key-off signal to the battery management system 100 when the user switches the start button to the off position. The charger 3 may provide a constant current or constant voltage charging power through the charge / discharge terminals P+, P- of the battery pack 10 via communication with the vehicle controller 2.

[0056] The battery pack 10 includes a battery module 11 and a battery management system 100 .

[0057] The battery module 11 includes at least one battery B. The battery B may be repeatedly recharged. In addition, the battery B is not limited to a specific type, and may include any battery having a characteristic that a voltage variation section changes according to a current rate, such as a lithium iron phosphate (LFP) battery.

[0058] When the battery module 11 includes a plurality of batteries, the plurality of batteries may be connected in series, in parallel, or in series and in parallel.

[0059] The relay 20 is electrically connected in series to the battery module 11 through a power path connecting the battery module 11 to the inverter 30 . Figure 1A relay 20 is shown connected between the positive terminal of the battery module 11 and the charge / discharge terminal P+. The relay 20 controls turning on or 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 or off by the magnetic force of a coil, or a semiconductor switch such as a metal oxide semiconductor field effect transistor (MOSFET).

[0060] The inverter 30 is configured to convert direct current power from the battery module 11 into alternating current power in response to a command from the battery management system 100 or the vehicle controller 2 .

[0061] The motor 40 is operated using the AC power from the inverter 30. The motor 40 may include a three-phase AC motor 40, for example.

[0062] The battery management system 100 includes a voltage detection unit 111, a current detection unit 113, a temperature detection unit 115, and a control unit 130. The battery management system 100 may further include a communication circuit 150.

[0063] The voltage detection unit 111 is connected to the positive terminal and the negative terminal of the battery B included in the battery module 11, and is configured to detect the terminal voltage across the two terminals of the battery B and output a voltage signal SV indicating the detected terminal voltage to the control unit 130.

[0064] The current detection unit 113 is connected in series to the battery module 11 through a current path between the battery module 11 and the inverter 30. The current detection unit 113 is configured to detect a charge / discharge current flowing through the battery module 11, and output a current signal SI indicating the detected charge / discharge current to the control unit 130. The current detection unit 113 may include one of known current detection devices such as, for example, a shunt resistor or a Hall effect device or a combination thereof.

[0065] Temperature detection unit 115 is configured to detect the temperature of battery B and output a temperature signal ST indicating the detected temperature to control unit 130. Temperature detection unit 115 may include one of known temperature detection devices such as, for example, a thermocouple, a thermistor, or a bimetallic strip, or a combination thereof.

[0066] The voltage detection unit 111 , the current detection unit 113 , and the temperature detection unit 115 may be referred to as a “sensing unit”.

[0067] The communication circuit 150 is configured to support wired or wireless communication between the control unit 130 and the vehicle controller 2. The wired communication may be, for example, a controller area network (CAN) communication, and the wireless communication may be, for example, Zigbee or Bluetooth communication. The communication protocol is not limited to a specific type, and may include a protocol that supports wired / wireless communication between the control unit 130 and the vehicle controller 2. The communication circuit 150 may include an output device (e.g., a display, a speaker) to provide information received from the control unit 130 and / or the vehicle controller 2 in a format recognizable to a user.

[0068] The control unit 130 is operably coupled to the relay 20, the voltage detection unit 111, the current detection unit 113, the temperature detection unit 115, and the communication circuit 150. The operably coupling may be a direct / indirect connection to enable signal transmission and reception in one or both directions.

[0069] The control unit 130 may collect the voltage signal SV from the voltage detection unit 111, the current signal SI from the current detection unit 113, and / or the temperature signal ST from the temperature detection unit 115. The control unit 130 may convert and record each of the analog signals collected from the detection units 111, 113, 115 into a digital value by using an analog-to-digital converter (ADC) within the control unit 130.

[0070] The control unit 130 may be referred to as a “control circuit” or a “battery controller” and may be implemented in hardware using at least one of an application specific integrated circuit (ASIC), a digital signal processor (DSP), a digital signal processing device (DSPD), a programmable logic device (PLD), a field programmable gate array (FPGA), a microprocessor, or an electrical unit for performing other functions.

[0071] The memory unit 140 may include, for example, at least one type of storage medium of a flash memory type, a hard disk type, a solid state disk (SSD) type, a silicon disk drive (SDD) type, a multimedia card micro type, a random access memory (RAM), a static random access memory (SRAM), a read only memory (ROM), an electrically erasable programmable read only memory (EEPROM), or a programmable read only memory (PROM). The memory unit 140 may store data and programs required for calculation operations performed by the control unit 130. The memory unit 140 may store data indicating results of calculation operations performed by the control unit 130. Although Figure 1 The memory unit 140 is shown to be physically independent from the control unit 130 , but the memory unit 140 may be included in the control unit 130 .

[0072] The memory unit 140 may store an equivalent circuit model (see Figure 2 ), state of charge (SOC)-open circuit voltage (OCV) curve (see Figure 3 ), constant current charge / discharge diagram (see Figure 4 ), a first extended Kalman filter and a second extended Kalman filter. Each of the SOC-OCV curve, the constant current charge / discharge diagram, the first extended Kalman filter and the second extended Kalman filter will be described in more detail below.

[0073] The control unit 130 may turn on the relay 20 in response to the key-on signal. The control unit 130 may turn off the relay 20 in response to the key-off signal. The key-off signal indicates a switch from the circulation mode to the rest mode. Alternatively, the vehicle controller 2 may be responsible for the on / off control of the relay 20 instead of the control unit 130.

[0074] When the relay 20 is turned on, the battery B of the battery module 11 enters the cycle mode. The cycle mode refers to an operating state in which the battery can be charged and discharged. The cycle mode may include a constant current charging mode, a constant current discharging mode, and a non-constant current charging / discharging mode.

[0075] The constant current charging mode refers to a state in which a charging current at a constant current rate flows in the battery B. The constant current discharging mode refers to a state in which a discharging current at a constant current rate flows in the battery B. The non-constant current charging / discharging mode refers to a state in which a non-constant charging or discharging current flows in the battery B.

[0076] When the relay 20 is turned off, the battery B of the battery module 11 enters a rest mode. The rest mode refers to an operating state in which a charge / discharge current is interrupted and the battery cannot be charged and discharged.

[0077] In the specification, the battery B in the first operating state refers to the battery B in the rest mode or the non-constant current charge / discharge mode. The battery B in the second operating state refers to the battery B in the constant current charge mode or the constant current discharge mode.

[0078] When the battery module 11 is in the cycle mode, the control unit 130 may determine a voltage value, a current value, and a temperature value based on the voltage signal SV, the current signal SI, and the temperature signal ST, respectively, and determine (estimate) the SOC of the battery B based on the voltage value, the current value, and / or the temperature value. The SOC refers to the ratio of the remaining capacity of the battery B to the fully charged capacity (maximum capacity).

[0079] In the specification, SOC is indicated as a range between 0 and 1, SOC 0 refers to a fully discharged state, and SOC 1 refers to a fully charged state.

[0080] In the specification, it is assumed that when U is a specific variable, 'U[k-1]' represents the value of U in the previous cycle, and 'U[k]' represents the value of U in the current cycle. The symbol k used with the symbol [] is a time index that increases by 1 every time a predetermined time period Δt (e.g., 0.001 seconds) elapses from an initial time point t0.

[0081] At the initial time point t0, k=0 may be set. For example, k=10 indicates that Δt×10 has passed since the initial time point t0, and the estimated SOC has been calculated 10 times during this time period. The initial time point t0 is a time point at which a predetermined event occurs, such as an event of switching of the control unit 130 from a dormant state to an awake state. The control unit 130 may switch from the dormant state to the awake state in response to the key-on of the electric vehicle 1, and switch from the awake state to the dormant state in response to the key-off of the electric vehicle 1.

[0082] Hereinafter, an equivalent circuit model and an SOC-OCV curve used by the first Kalman filter will be described. The following equations 1 to 8 express the first extended Kalman filter, and when describing each of equations 1 to 8, already described variables may be omitted to avoid redundancy.

[0083] The first extended Kalman filter uses a state equation including the SOC and the polarization voltage as state variables (see Equation 4-1 and Equation 4-2 below), and the following Equation 1 expresses the relationship between the SOC and the charge / discharge current by ampere count.

[0084] <Equation 1>

[0085]

[0086] In Equation 1, I[k-1] represents the detected charge / discharge current in the previous cycle, Q i represents the maximum capacity of battery B, SOC[k-1] represents the SOC in the previous cycle, and SOC[k] represents the SOC in the current cycle. I[0]=0A. Q i represents the maximum amount of charge that can be stored in battery B. In other words, the maximum capacity Q i Equal to the accumulated value of the charge / discharge current from either the fully charged state or the fully discharged state of battery B to the other state.

[0087] Then, Figure 2 It is shown Figure 1 FIG. 2 is a diagram of an exemplary equivalent circuit model 200 of a battery B shown in FIG. Figure 3 It is shown exemplarily Figure 1Graph of the SOC-OCV curve of battery B is shown in FIG.

[0088] refer to Figure 2 The equivalent circuit model 200 includes a voltage source 210, a resistor R DC and RC to R P , C P The symbol I indicates the charging current.

[0089] The output voltage V of the voltage source 210 OCV Indicates the OCV of Battery B when it is kept in rest mode for a long time and reaches equilibrium.

[0090] Figure 3 Two SOC-OCV curves 310, 320 are shown. The SOC-OCV curve 310 shows the change in OCV of battery B during the charge cycle, and the SOC-OCV curve 320 shows the change in OCV of battery B during the discharge cycle. At the same SOC, the OCV in the SOC-OCV curve 310 is slightly higher than the OCV in the SOC-OCV curve 320, and this difference originates from the hysteresis phenomenon of battery B during the charge cycle and the discharge cycle.

[0091] In either of the two SOC-OCV curves 310 , 320 , the SOC and OCV of battery B have a nonlinear positive correlation. That is, when f OCV With f SOC When it is an inverse function, OCV=f OCV (SOC), SOC=f SOC (OCV).

[0092] Figure 3 The SOC-OCV curves 310 , 320 shown in FIG. 1 are associated with a specific temperature or a specific temperature range, and other SOC-OCV curves associated with other temperatures or temperature ranges may be additionally stored in the memory unit 140 .

[0093] Meanwhile, both SOC-OCV curves 310 , 320 have a voltage variation section, that is, a SOC range in which a change (which may be an absolute value) of OCV relative to SOC is equal to or greater than a reference value. Figure 3 , reference numeral 311 indicates a voltage variation section of the SOC-OCV curve 310 , and reference numeral 321 indicates a voltage variation section of the SOC-OCV curve 320 .

[0094] Resistor R DC IR drop with battery B V DC Related. IR drop V DCThe instantaneous change of the terminal voltage across the battery B due to the charge / discharge current. The memory unit 140 can record the definition of SOC, temperature and resistor R DC and the control unit 130 can determine the resistor R corresponding to the SOC and temperature in the previous (or current) cycle from the first lookup table. DC .

[0095] The RC pair refers to the resistor R P and capacitor C P parallel circuit, and the polarization voltage (also called "overpotential") V of battery B P The time constant of the RC pair is the resistor R P and capacitor C P The memory unit 140 can record the definition of SOC, temperature and RC to R P , C P The control unit 130 can determine the resistor R corresponding to the SOC and temperature in the previous (or current) cycle from the second lookup table. P and capacitor C P . Determine the resistor R P and capacitor C P It can refer to determining the resistor R P The resistor and capacitor C P of capacitance.

[0096] V ecm is a variable indicating the voltage across the equivalent circuit model 200 and may indicate an estimated terminal voltage of the battery B. As shown in the following equation 2-1, V ecm Can be the output voltage V OCV 、IR voltage drop V DC and polarization voltage V P sum.

[0097] <Equation 2-1>

[0098]

[0099] In equation 2-1, R DC [k] is the resistor R in the current loop DC resistance, I[k] is the measured charge / discharge current in the current cycle, V OCV [k] is the estimated OCV in the current cycle, and V P [k] is the estimated polarization voltage in the current cycle. Equation 2-1 can be expressed by the following equation 2-2.

[0100] <Equation 2-2>

[0101]

[0102] In Equation 2-2, C[k] is a system matrix with two components c[k] and 1. c[k] is obtained by the function f OCV The obtained value from SOC[k] to V OCV The conversion factor of [k]. That is, the product of c[k] and SOC[k] is equal to V OCV [k].

[0103] In the equivalent circuit model 200, the polarization voltage V can be calculated (estimated) using the following equation 3-1 or equation 3-2: P .

[0104] <Equation 3-1>

[0105]

[0106] <Equation 3-2>

[0107]

[0108] In Equation 3-1 and Equation 3-2, V P [k] represents the polarization voltage in the current cycle, V P [k-1] represents the polarization voltage in the previous cycle, and τ represents the RC to R P , C P The time constant, and R P [k] indicates the resistor R in the current cycle P The resistance of τ can be R P [k-1] and R P [k] one and C P [k-1] and C P The product of one of [k]. V P [0] can be set to 0V.

[0109] Hereinafter, the first extended Kalman filter will be described in detail. The state equation of the first extended Kalman filter can be represented by the following equation 4-1 or equation 4-2. Equation 4-1 is associated with equation 1 and equation 3-1, and equation 4-2 is associated with equation 1 and equation 3-2.

[0110] <Equation 4-1>

[0111]

[0112] <Equation 4-2>

[0113]

[0114] In Equation 4-1 and Equation 4-2, SOC ^ [k-1] represents the estimated SOC in the previous cycle, V P^ [k-1] represents the estimated polarization voltage in the previous cycle, Q i represents the maximum capacity of battery B, and τ represents the RC to R P , C P The time constant of x ^ - [k] is the state matrix in the current cycle, and the SOC ^ - [k] and VP ^ - [k] are state variables indicating the estimated SOC and polarization voltage in the current cycle, respectively.

[0115] Equation 5 below is the time update equation for the first extended Kalman filter.

[0116] <Equation 5>

[0117]

[0118] In Equation 5, P[k-1] represents the estimated error covariance matrix in the previous cycle, W represents the process noise covariance matrix, and P - [k] represents the estimated error covariance matrix in the current cycle. In Equation 5, A1 is the Jacobian matrix of the function f1 in Equation 4-1 and Equation 4-2. The Jacobian matrix A1 can be represented by the following Equation 5-1.

[0119] <Equation 5-1>

[0120]

[0121] A1 T is the transposed matrix of A1. In the case of k=0, P[0]=[1 0; 0 1]. When the time update process using Equation 4-1 or Equation 4-2 and Equation 5 is completed, the control unit 130 performs a measurement update process.

[0122] Equation 6 below is the first measurement update equation of the first extended Kalman filter.

[0123] <Equation 6>

[0124]

[0125] In Equation 6, K[k] is the Kalman gain in the current cycle, H1 is the Jacobian matrix of the function h1 according to the following Equation 6-1, H1 Tis the transposed matrix of H1, and L is the measurement noise covariance matrix.

[0126] Regarding Equation 6, we can get the state matrix (x ^ - [k]) is associated with Equation 2-1 to derive the terminal voltage estimation equation (output equation) of the following Equation 6-1.

[0127] <Equation 6-1>

[0128]

[0129] The Jacobian matrix H1 in Equation 6 can be expressed by the following Equation 6-2.

[0130] <Equation 6-2>

[0131]

[0132] Equation 7 below is a second measurement update equation for the first extended Kalman filter.

[0133] <Equation 7>

[0134]

[0135] In Equation 7, P[k] is P from Equation 5 corrected by Equation 7. - [k] results.

[0136] Equation 8 below is the third measurement update equation of the first extended Kalman filter.

[0137] <Equation 8>

[0138]

[0139] In Equation 8, z[k] is the detected terminal voltage in the current cycle, z ^ [k] is the estimated terminal voltage in the current cycle, SOC ^ [k] is the estimated SOC in the current cycle (referred to as “first estimated SOC” in the claims), and V P^ [k] is the estimated polarization voltage in the current cycle. ^ [k] can be used as x in equation 4 in the next loop ^ [k-1].

[0140] When the first extended Kalman filter is operated by the control unit 130, a first estimated SOC indicating the current SOC of the battery B according to the above process is output from the first extended Kalman filter. The control unit 130 may operate the second extended Kalman filter in parallel while the first extended Kalman filter is in operation. That is, the first extended Kalman filter and the second extended Kalman filter may be operated simultaneously.

[0141] Hereinafter, the constant current charge / discharge diagram will be explained first, and then the second extended Kalman filter will be described in detail.

[0142] Figure 4 is a graph used as a reference in describing a constant current charge / discharge graph according to the present disclosure. The constant current charge / discharge graph 400 includes a plurality of charge curves 411 to 416 and a plurality of discharge curves 421 to 426.

[0143] Each of the plurality of charging curves 411-416 indicates the terminal voltage versus SOC of battery B during a constant current charging cycle using different current rates (also referred to as "C-rates"). CCV may be a term describing the measured terminal voltage of battery B during charging or discharging. During a charging cycle, as the current rate is higher, the CCV at the same SOC is higher.

[0144] Each of the plurality of discharge curves 421-416 indicates the voltage (CCV) versus SOC of the battery B during a constant current discharge cycle using different current rates. During the discharge cycle, as the current rate is higher, the CCV at the same SOC is lower.

[0145] The plurality of charge curves 411-416 and the plurality of discharge curves 421-416 include six charge curves and six discharge curves, respectively, and the current rates are in ascending order of 0.05 C, 0.15 C, 0.25 C, 0.50 C, 1.00 C, and 1.50 C. Each curve included in the constant current charge / discharge graph 400 may be stored in the memory unit 140 in the form of a function.

[0146] To help understand, Figure 4 A plurality of charging curves 411 to 416 and a plurality of discharging curves 421 to 416 are shown. Figure 3 The two SOC-OCV curves 310 and 320 are shown in FIG. Figure 4 It can be seen that as the current rate used during the charge cycle increases, the voltage variation section present in the SOC-OCV curve 310 gradually disappears. Likewise, as the current rate used during the discharge cycle increases, the voltage variation section present in the SOC-OCV curve 320 also gradually disappears.

[0147] As described above, it is not easy to design the equivalent circuit model 200 to accurately describe the so-called fading, which is a phenomenon in which a voltage variation section disappears as the current rate increases. In addition, when the SOC of the battery B during constant current charging or constant current discharging is estimated using the equivalent circuit model 200 that does not accurately describe the fading characteristics at or above a predetermined level, there may be a large difference between the actual SOC and the estimated SOC.

[0148] Therefore, in order to solve the above problem, during constant current charging or discharging, the SOC of battery B can be estimated based on the output value of the second extended Kalman filter instead of the output value of the first extended Kalman filter using the constant current charging / discharging diagram 400, or the SOC of battery B can be estimated by combining the output value of the first extended Kalman filter with the output value of the second extended Kalman filter (e.g., a weighted average).

[0149] In contrast to the first extended Kalman filter that uses SOC and polarization voltage as its state variables, the second extended Kalman filter uses only SOC as its state variable, and the second extended Kalman filter can be expressed by Equation 9 below.

[0150] <Equation 9>

[0151]

[0152] In Equation 9, x ^ i[k-1] is the estimated SOC in the previous cycle, i[k] is the current value of the detected charge / discharge current in the current cycle, Q i is the maximum capacity of battery B, x ^ - [k] is the estimated SOC in the current cycle, x ^ - [k] may be equal to SOC indicating the estimated SOC in the current cycle ^ - [k], and f2(x ^ [k-1]) can be equal to x ^ [k-1].

[0153] The following Equation 10 is a time update equation for the second extended Kalman filter.

[0154] <Equation 10>

[0155]

[0156] In Equation 10, P[k-1] represents the estimated error covariance in the previous cycle, w represents the process noise covariance, and P -[k] represents the estimated error covariance in the current cycle. A2 is the Jacobian matrix of the function f2 in Equation 9. The Jacobian matrix A2 can be represented by the following Equation 10-1.

[0157] <Equation 10-1>

[0158]

[0159] A2 T is the transposed matrix of A2. In the case of k=0, P[0]=0. When the time update process using Equation 9 and Equation 10 is completed, the control unit 130 performs a measurement update process.

[0160] The following Equation 11 is the first measurement update equation of the second extended Kalman filter.

[0161] <Equation 11>

[0162]

[0163] In Equation 11, K[k] is the Kalman gain in the current cycle, H2 is the Jacobian matrix of the function h2 in Equation 11-1 below, and H2 T is the transposed matrix of H2, and l is the measurement noise covariance.

[0164] In relation to Equation 11, in contrast to the first extended Kalman filter, the second extended Kalman filter uses a constant current charge / discharge diagram 400, and thus the terminal voltage estimation equation (output equation) of the following Equation 12-1 can be derived.

[0165] <Equation 12-1>

[0166]

[0167] In Equation 12-1, the function f CCV_I[k] is a function that defines any one charging or discharging curve associated with the current rate corresponding to I[k] among the curves included in the constant current charging / discharging diagram 400. The control unit 130 selects any one charging curve corresponding to I[k] from the plurality of charging curves 411 to 416 in response to I[k] being the charging current. Selecting any one charging curve may refer to acquiring the function f from the memory unit 140. CCV_I[k] Subsequently, the control unit 130 may set the estimated terminal voltage of the battery B in the current cycle so that the state variable (SOC ^ - [k]) is equal to the function f when input CCV_I[k] The output value (z ^ [k]).

[0168] In addition, the Jacobian matrix H in Equation 12-1 can be expressed by the following Equation 12-2.

[0169] <Equation 12-2>

[0170]

[0171] Equation 13 below is a second measurement update equation for the second extended Kalman filter.

[0172] <Equation 13>

[0173]

[0174] In Equation 13, P[k] is P from Equation 10 corrected by Equation 13. - [k] results.

[0175] The following Equation 14 is the third measurement update equation of the second extended Kalman filter.

[0176] <Equation 14>

[0177]

[0178] In Equation 14, z[k] is the detected terminal voltage in the current cycle, z ^ [k] is the estimated terminal voltage in the current cycle, and SOC ^ [k] is the estimated SOC in the current cycle (referred to as “second estimated SOC” in the claims). x in Equation 14 ^ [k] can be used as x in Equation 9 in the next loop ^ [k-1].

[0179] The SOC estimation of battery B by the first extended Kalman filter and the second extended Kalman filter has been described above.

[0180] The control unit 130 may determine the maximum capacity Q of the battery B as a basic variable used by the first extended Kalman filter and the second extended Kalman filter by using the following Equation 15: i .

[0181] <Equation 15>

[0182]

[0183] In Equation 15, ΔSOC is the change in SOC for the capacity update period, and ΔQ is the accumulated value of the current counted by the ampere for the capacity update period. In Equation 15, 'a' is a time index corresponding to the start time of the capacity update period, and 'b' is a time index corresponding to the end time of the capacity update period. The capacity update period may be the most recent period during which ΔSOC is equal to or higher than a threshold change (e.g., 0.5).

[0184] The maximum capacity gradually decreases as the battery B deteriorates. Therefore, when the degree of degradation of the battery B is higher than a predetermined level, there is a high possibility that the battery cell suddenly becomes inoperable, and thus it is necessary to estimate the SOC more accurately.

[0185] Figure 5 is a flowchart exemplarily illustrating a battery management method for an SOC estimation method according to a first embodiment of the present disclosure. Figure 5 The method may be repeatedly executed at preset time intervals starting from the time when the predetermined event occurs.

[0186] refer to Figures 1 to 5 In step S510, the control unit 130 detects the terminal voltage V[k] and the charge / discharge current I[k] of the battery B, and determines the voltage value V[k] of the terminal voltage and the current value I[k] of the charge / discharge current.

[0187] In step S520, the control unit 130 determines a first estimated SOC by inputting a voltage value V[k], a current value I[k], and an estimated SOC in a previous cycle to a first extended Kalman filter. The first extended Kalman filter is an SOC estimation logic using an equivalent circuit model 200 of battery B and a SOC-OCV curve 300. The first estimated SOC may be a candidate value indicating the SOC of battery B in the current cycle. The voltage value V[k] of the terminal voltage may be used as z[k] in equation 8. When the current value I[k] indicates a charging direction, the control unit 130 may provide a SOC-OCV curve 310 among two SOC-OCV curves 310, 320 to the first extended Kalman filter. On the contrary, when the current value I[k] indicates a discharging direction, the control unit 130 may provide a SOC-OCV curve 320 among two SOC-OCV curves 310, 320 to the first extended Kalman filter.

[0188] In step S530, the control unit 130 determines a second estimated SOC by inputting the current value and the estimated SOC in the previous cycle into the second extended Kalman filter. The second extended Kalman filter is an SOC estimation logic using a constant current charge / discharge diagram 400 of battery B. The second estimated SOC may be another candidate value indicating the SOC of battery B in the current cycle. When the current value I[k] indicates a charging direction, the control unit 130 may provide any one of a plurality of charging curves 411 to 416 associated with a current rate corresponding to the current value I[k] to the second extended Kalman filter. Conversely, when the current value I[k] indicates a discharging direction, the control unit 130 may provide any one of a plurality of charging curves 421 to 426 associated with a current rate corresponding to the current value I[k] to the second extended Kalman filter.

[0189] When the time index k is 1, the average of the two SOCs corresponding to the OCV at the initial time point t0 in the two curves 310 and 320 may be input to the first extended Kalman filter and the second extended Kalman filter as the estimated SOC in the previous cycle in steps S520 and S530 .

[0190] In step S540 , the control unit 130 determines the SOC of the battery B in the current cycle based on at least one of the first estimated SOC and the second estimated SOC.

[0191] Figure 6 is a flowchart exemplarily illustrating a battery management method for SOC estimation according to a second embodiment of the present disclosure. Figure 6 The method can be based on Figure 5 An example of a set of subroutines of step S540 of the battery management method.

[0192] refer to Figure 6 , in step S610, the control unit 130 determines whether the battery B is being charged / discharged at a constant current based on the current value I[k] or the current time series data indicating the time-related change history of the charging / discharging current. As an example, in the case where the time index k=100, the current time series data includes I[1]~I

[100] as data points. The value of step S610 is "No" indicating a first state in which the battery B is not being charged / discharged at a constant current. When the value of step S610 is "No", the process moves to step S620. The value of step S610 is "Yes" indicating a second state in which the battery B is being charged / discharged at a constant current. When the value of step S610 is "Yes", the process moves to step S630.

[0193] In step S620 , the control unit 130 determines that the SOC of the battery B in the current cycle is equal to the first estimated SOC.

[0194] In step S630 , the control unit 130 determines that the SOC of the battery B in the current cycle is equal to the second estimated SOC.

[0195] Figure 7 is a flowchart exemplarily illustrating a battery management method for SOC estimation according to a third embodiment of the present disclosure, and Figure 8 is describing the Figure 7 Figure used as reference in the method. Figure 7 The method can be based on Figure 5 The third embodiment is another example of a set of subroutines of step S540 of the battery management method. That is, the third embodiment is a variation of the second embodiment.

[0196] refer to Figure 7 In step S710, the control unit 130 determines whether the battery B is being charged / discharged at a constant current based on the current value I[k] or the current time series data indicating the time-dependent change history of the charge / discharge current. When the value of step S710 is "No", the process moves to step S720. When the value of step S710 is "Yes", the process moves to step S730.

[0197] In step S720, the control unit 130 determines a first weight and a second weight that are positively correlated and negatively correlated with the duration of the first state, respectively. The first weight may be greater than the second weight. The sum of the first weight and the second weight may be a preset constant (e.g., 1). In this case, when any one of the first weight and the second weight is determined, the remaining one may also be determined.

[0198] Figure 8 is a diagram exemplarily showing a change in the first weight according to the duration of the first state. Figure 8 , which shows that the minimum value of the first weight is 0.6, then in the time range 0~t S1 As the duration of the first state increases, the first weight increases, and from the duration of the first state to the first reference time t S1 From then on, the first weight is constantly maintained at 1.

[0199] In step S722, the control unit 130 determines that the SOC of battery B in the current cycle is equal to the weighted average of the first estimated SOC and the second estimated SOC by the first weight and the second weight. As an example, in the case where the first weight = 0.8, the second weight = 1-the first weight = 0.2, the first estimated SOC = 0.60, and the second estimated SOC = 0.62, the weighted average = (0.8 * 0.60) + (0.2 * 0.62) = 0.604. That is, the SOC of battery B in the current cycle can be determined to be 60.4%.

[0200] In step S730 , the control unit 130 determines whether the SOC of the battery B in the current cycle is equal to the second estimated SOC.

[0201] Fig. 9 is a flowchart exemplarily illustrating a battery management method for SOC estimation according to a fourth embodiment of the present disclosure. And Fig.10 is describing the Fig. 9 Figure used as reference in the method. Fig. 9 The method can be based on Figure 5 The fourth embodiment is another example of a set of subroutines of step S540 of the battery management method. That is, the fourth embodiment is an additional variation of the second embodiment.

[0202] refer to Fig. 9 In step S910, the control unit 130 determines whether the battery B is being charged / discharged at a constant current based on the current value or the current time series data indicating the time-dependent change history of the charge / discharge current. When the value of step S910 is "No", the process moves to step S920. When the value of step S910 is "Yes", the process moves to step S930.

[0203] In step S920 , the control unit 130 determines whether the SOC of the battery B in the current cycle is equal to the first estimated SOC.

[0204] In step S930, the control unit 130 determines a third weight and a fourth weight that are negatively correlated and positively correlated with the duration of the second state, respectively. The third weight may be less than the fourth weight. The sum of the third weight and the fourth weight may be a preset constant (e.g., 1). In this case, when any one of the third weight and the fourth weight is determined, the remaining one may also be determined.

[0205] Fig.10 is a diagram exemplarily showing a change in the third weight according to the duration of the second state. Fig.10 , which shows that the maximum value of the third weight is 0.4, then in the time range (0~t S2), as the duration of the second state increases, the third weight decreases, and from the duration of the second state to the second reference time t S2 From then on, the third weight is constantly maintained at 0.

[0206] In step S932, the control unit 130 determines that the SOC of the battery B in the current cycle is equal to the weighted average of the first estimated SOC and the second estimated SOC by the third weight and the fourth weight. As an example, when the third weight = 0.1, the fourth weight = 1-the third weight = 0.9, the first estimated SOC = 0.60, and the second estimated SOC = 0.62, the weighted average = (0.1 * 0.60) + (0.9 * 0.62) = 0.618. That is, the SOC of the battery B in the current cycle can be determined to be 61.8%.

[0207] Fig.11 is a flowchart exemplarily illustrating a battery management method for SOC estimation according to a fifth embodiment of the present disclosure. Fig.11 The method can be based on Figure 5 The fifth embodiment is another example of a set of subroutines of step S540 of the battery management method. That is, the fifth embodiment is an additional variation of the second embodiment.

[0208] refer to Fig.11 In step S1110, the control unit 130 determines whether the battery B is being charged / discharged at a constant current based on the current value or the current time series data indicating the time-dependent change history of the charge / discharge current. When the value of step S1110 is "No", the process moves to step S1120. When the value of step S1110 is "Yes", the process moves to step S1130.

[0209] In step S1120 , the control unit 130 determines a first weight and a second weight having a positive correlation and a negative correlation with the duration of the first state, respectively.

[0210] In step S1122 , the control unit 130 determines that the SOC of the battery B in the current cycle is equal to a weighted average of the first estimated SOC and the second estimated SOC by the first weight and the second weight.

[0211] Step S1120 and step S1122 are Figure 7 Step S720 is the same as step S722.

[0212] In step S1130 , the control unit 130 determines a third weight and a fourth weight having a negative correlation and a positive correlation with the duration of the second state, respectively.

[0213] In step S1132 , the control unit 130 determines that the SOC of the battery B in the current cycle is equal to a weighted average of the first estimated SOC and the second estimated SOC by the third weight and the fourth weight.

[0214] Step S1130 and step S1132 are Fig. 9 Step S930 is the same as step S932.

[0215] Fig.12 is a flow chart exemplarily showing a method for determining whether a battery is being charged / discharged at a constant current. Fig.12 The method can be Figure 6 Step S610, Figure 7 Step S710, Fig. 9 Step S910 or Fig.11 A set of subroutines of at least one of step S1110.

[0216] In step S1210, the current time series data is filtered using a high pass filter (HPF). The high pass filter is a filter that removes signal components less than a predetermined cutoff frequency and allows signal components greater than the cutoff frequency to pass through it. When the battery B is in the second state or is at rest, the output value of the high pass filter may be 0, and in other states, the output value of the high pass filter may not be 0. As the fluctuation of the current flowing in the battery B is smaller, the output value of the high pass filter is closer to 0.

[0217] In step S1220, the control unit 130 determines whether the output value of the high-pass filter is within a reference range (e.g., -0.001 to 0.001). When the value of step S1220 is "yes", the process can move to step S1230. The reference range can be appropriately preset according to the filtering accuracy of the high-pass filter and the detection accuracy of the current detection unit 113. When the value of step S1220 is "no", the process moves to Figure 6 Step S620, Figure 7 Step S720, Fig. 9 Step S910 and Fig.11 Any one of steps S1120.

[0218] In step S1230, the control unit 130 determines whether the current value is 0 [A]. When the value of step S1230 is "yes", the process moves to Figure 6 Step S620, Figure 7 Step S720, Fig. 9 Step S910 and Fig.11 When the value of step S1230 is "No", the process moves to Figure 6 Step S630, Figure 7 Step S730, Fig. 9 Step S930 or Fig.11 Any one of steps S1130.

[0219] Although Figure 6 Step S610, Figure 7 Step S710, Fig. 9 Step S910 and Fig.11 Step S1110 has been described as a subroutine of step S540, but it should be understood as an example. Figure 5 Step S520 or step S530 is performed by the current value determined in step S510 before step S520 or step S530 Figure 6 Step S610, Figure 7 Step S710, Fig. 9 Step S910 or Fig.11 At least one of step S1110.

[0220] The embodiments of the present disclosure described above are not implemented only by devices and methods, but can be implemented by a program that implements functions corresponding to the configuration of the embodiments of the present disclosure or a recording medium on which the program is recorded, and those skilled in the art can easily implement such an implementation according to the disclosure of the embodiments described above.

[0221] Although the present disclosure has been described above with respect to a limited number of embodiments and drawings, the present disclosure is not limited thereto, and it will be apparent to those skilled in the art that various modifications and changes may be made thereto within the technical aspects of the present disclosure and the equivalent scope of the appended claims.

[0222] In addition, since those skilled in the art can make many substitutions, modifications and changes to the present disclosure without departing from the technical aspects of the present disclosure, the present disclosure is not limited to the foregoing embodiments and drawings, and some or all of the embodiments may be selectively combined to make various modifications to the present disclosure.

Claims

1. A battery management system for a battery having a characteristic that a voltage variation section changes according to a current rate, the battery management system comprising: a sensing unit configured to detect a terminal voltage and a charge / discharge current of the battery; a memory unit configured to store a first Kalman filter that is a state of charge (SOC) estimation logic using an equivalent circuit model and a state of charge (SOC)-open circuit voltage (OCV) curve of the battery, and a second Kalman filter that is a SOC estimation logic using a constant current charge / discharge map of the battery; as well as a control unit configured to determine a voltage value of the detected terminal voltage and a current value of the detected charging / discharging current, Wherein, the control unit is configured as: determining a first estimated SOC by inputting the voltage value, the current value, and the estimated SOC in the previous cycle into the first Kalman filter, determining a second estimated SOC by inputting the current value and the estimated SOC in the previous cycle into the second Kalman filter; as well as The SOC of the battery in a current cycle is determined based on at least one of the first estimated SOC and the second estimated SOC.

2. The battery management system according to claim 1, wherein: The control unit is configured to: determining whether the battery is in a first state in which the battery is not being charged / discharged with a constant current or a second state in which the battery is being charged / discharged with the constant current based on the current value or current time series data indicating a time-dependent change history of the charge / discharge current, In response to determining that the battery is in the first state, determining the SOC of the battery in the current cycle to be equal to the first estimated SOC, and In response to determining that the battery is in the second state, the SOC of the battery in the current cycle is determined to be equal to the second estimated SOC.

3. The battery management system according to claim 1, wherein: The control unit is configured to: determining whether the battery is in a first state in which the battery is not being charged / discharged with a constant current or a second state in which the battery is being charged / discharged with the constant current based on the current value or current time series data indicating a time-dependent change history of the charge / discharge current, In response to determining that the battery is in the first state, determining a first weight having a positive correlation with a duration of the first state and a second weight having a negative correlation with the duration of the first state, and The SOC of the battery in the current cycle is determined to be equal to a weighted average of the first estimated SOC and the second estimated SOC by the first weight and the second weight.

4. The battery management system according to claim 3, wherein: The first weight is greater than the second weight, and The sum of the first weight and the second weight is 1.

5. The battery management system according to claim 1, wherein: The control unit is configured to: determining whether the battery is in a first state in which the battery is not being charged / discharged with a constant current or a second state in which the battery is being charged / discharged with the constant current based on the current value or current time series data indicating a time-dependent change history of the charge / discharge current, In response to determining that the battery is in the second state, determining a third weight having a negative correlation with a duration of the second state and a fourth weight having a positive correlation with the duration of the second state, and The first estimated SOC and the second estimated SOC are determined as the SOC of the battery in the current cycle by a weighted average of the third weight and the fourth weight.

6. The battery management system according to claim 5, wherein: The third weight is less than the fourth weight, and The sum of the third weight and the fourth weight is 1.

7. The battery management system according to claim 1, wherein: The constant current charge / discharge diagram includes: a plurality of charging curves indicating a relationship between the SOC and the voltage of the battery during constant current charging using a plurality of current rates; and a plurality of discharge curves indicating a relationship between the SOC and the voltage of the battery during constant current discharge using the plurality of current rates, and Wherein, in response to providing any one of the plurality of charging curves and the plurality of discharging curves to the second Kalman filter, the second estimated SOC is output from the second Kalman filter.

8. The battery management system according to claim 7, wherein: The control unit is configured to: In response to the battery being charged at the constant current, providing any one of the plurality of charging curves associated with a current rate corresponding to the current value to the second Kalman filter, and In response to the battery being discharged at the constant current, any one of the plurality of discharge curves associated with a current rate corresponding to the current value is provided to the second Kalman filter.

9. A battery pack comprising the battery management system according to any one of claims 1 to 8.

10. An electric vehicle comprising the battery pack according to claim 9.

11. A battery management method for a battery having a characteristic that a voltage variation section changes according to a current rate, the battery management method comprising: detecting a terminal voltage and a charge / discharge current of the battery and determining a voltage value of the detected terminal voltage and a current value of the detected charge / discharge current; determining a first estimated state of charge (SOC) by inputting the voltage value, the current value, and an estimated state of charge (SOC) in a previous cycle into a first Kalman filter, the first Kalman filter being an SOC estimation logic using an equivalent circuit model of the battery and an SOC-open circuit voltage (OCV) curve; determining a second estimated SOC by inputting the current value and the estimated SOC in the previous cycle to a second Kalman filter, the second Kalman filter being an SOC estimation logic using a constant current charge / discharge map of the battery; as well as The SOC of the battery in a current cycle is determined based on at least one of the first estimated SOC and the second estimated SOC.

12. The battery management method according to claim 11, wherein: Determining the SOC of the battery in the current cycle includes: determining whether the battery is in a first state in which the battery is not being charged / discharged with a constant current or a second state in which the battery is being charged / discharged with the constant current based on the current value or current time series data indicating a time-dependent change history of the charge / discharge current; In response to determining that the battery is in the first state, determining the first estimated SOC as the SOC of the battery in the current cycle; and In response to determining that the battery is in the second state, the second estimated SOC is determined as the SOC of the battery in the current cycle.

13. The battery management method according to claim 11, wherein: Determining the SOC of the battery in the current cycle includes: determining whether the battery is in a first state in which the battery is not being charged / discharged with a constant current or a second state in which the battery is being charged / discharged with the constant current based on the current value or current time series data indicating a time-dependent change history of the charge / discharge current; In response to determining that the battery is in the first state, determining a first weight having a positive correlation with a duration of the first state and a second weight having a negative correlation with the duration of the first state; and The first estimated SOC and the second estimated SOC are determined as the SOC of the battery in the current cycle by a weighted average of the first weight and the second weight.

14. The battery management method according to claim 11, wherein: Determining the SOC of the battery in the current cycle includes: determining whether the battery is in a first state in which the battery is not being charged / discharged with a constant current or a second state in which the battery is being charged / discharged with the constant current based on the current value or current time series data indicating a time-dependent change history of the charge / discharge current; In response to determining that the battery is in the second state, determining a third weight having a negative correlation with a duration of the second state and a fourth weight having a positive correlation with the duration of the second state; and The first estimated SOC and the second estimated SOC are determined as the SOC of the battery in the current cycle by a weighted average of the third weight and the fourth weight.

15. The battery management method according to claim 11, wherein: The constant current charge / discharge diagram includes: a plurality of charging curves indicating a relationship between the SOC and the voltage of the battery during constant current charging using a plurality of current rates; and a plurality of discharge curves indicating a relationship between the SOC and the voltage of the battery during constant current discharge using the plurality of current rates, and Wherein, in response to providing any one of the plurality of charging curves and the plurality of discharging curves to the second Kalman filter, the second estimated SOC is output from the second Kalman filter.

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