Battery control device and battery control method

Abstract

The present invention comprises: a current sensor 14 that detects a state of a battery; and a battery controller 12 that estimates the SOC of the battery on the basis of detection data and computes an allowable current for charging and discharging of the battery. The battery controller associates an equivalent circuit model including a resistive element and a capacitive element with the resistive element, the capacitive element, the state of the battery, and the SOC, and computes the allowable current on the basis of a battery data table. The battery controller uses the estimated SOC as an average SOC, obtains a local SOC on the basis of the average SOC and the amount of charge in the capacitive element, and computes the allowable current by referring to the battery data table on the basis of the local SOC and the detection data.

Description

Battery control device and battery control method

[0001] The present invention relates to a battery control device and a battery control method.

[0002] In recent years, the use of battery control devices incorporating multiple batteries, such as energy storage devices for mobile vehicles, energy storage devices for grid connection stabilization, and emergency energy storage devices, has been expanding. To ensure optimal performance, battery control devices must accurately calculate the battery's state of charge (SOC), state of health (SOH), and maximum charge / discharge current (allowable current). SOC is an indicator of how fully charged the battery is, or how much charge remains in the battery that can be discharged. SOH is an indicator of how much the battery has deteriorated from its initial state. Allowable current is the maximum current that the battery can charge or discharge without exceeding its upper and lower voltage limits.

[0003] A battery's allowable current includes the allowable charging current, which represents the allowable current during charging, and the allowable discharge current, which represents the allowable current during discharging. When the State of Charge (SOC) is high, the allowable charging current decreases and the allowable discharge current increases. Conversely, when the SOC is low, the allowable charging current increases and the allowable discharge current decreases. A battery control device accurately determines the allowable current to maximize the battery's charge and discharge performance. If the battery control device misestimates the allowable current, it can lead to deviations from the upper and lower limits of the battery voltage. Therefore, establishing a highly accurate method for detecting the allowable current is important. As prior art related to the detection of allowable current, for example, the battery state detection device disclosed in Patent Document 1 is known.

[0004] Japanese Patent Publication No. 2016-023968

[0005] Prior art relating to Patent Document 1 describes a battery state detection device that, based on the estimated SOC, refers to a battery data table to determine the OCV, DC resistance, and polarization resistance, and predicts the allowable current by dividing the difference between the current OCV and the upper and lower limit voltages by the calculated internal resistance.

[0006] However, even with the allowable current estimated by the prior art described above, it is desirable to suppress the deviation of the battery voltage from the upper and lower limits due to charging and discharging the battery with a high current. Therefore, the present invention aims to provide a battery control device that can predict even the rapid rise or fall of the battery voltage when charging and discharging the battery with a high current, with a low computational load using an equivalent circuit, and thus can determine the allowable current with high accuracy.

[0007] To achieve the above objective, the present invention provides a battery control device for controlling the charging and discharging of a battery, comprising: a detection unit for detecting the battery state; a charging state estimation unit for estimating the charging state of the battery based on the detection data from the detection unit; and an allowable current calculation unit for calculating the allowable current for charging and discharging the battery based on an equivalent circuit model of the battery, which includes a resistive element and a capacitor element, and a data structure relating the resistive element, the capacitor element, the battery state, and the charging state, wherein the allowable current calculation unit takes the charging state estimated by the charging state estimation unit as a first charging state, determines a second charging state based on the first charging state and the charge amount of the capacitor element, and calculates the allowable current by referring to the data structure based on the second charging state and the detection data detected by the detection unit.

[0008] According to the present invention, it is possible to provide a battery control device and a battery control method that can predict even the rapid rise or fall of the battery voltage when the battery is charged or discharged with a large current, while having a low computational load using an equivalent circuit, and therefore can determine the allowable current with high accuracy.

[0009] This is a block diagram showing the hardware configuration of a battery system equipped with an embodiment of the battery control device according to the present invention. This is a functional block diagram of the battery controller of the battery control device. This is a waveform diagram showing the voltage behavior of the battery when a rectangular wave current is applied to the battery. This is a block diagram of the equivalent circuit of the battery. This is a diagram showing the battery parameter table. This is a diagram showing the SOC dependence of Ro in the battery parameter table. This is a diagram showing the SOC dependence of Rp in the battery parameter table. This is an example of a flowchart of the control operation of the allowable current calculation unit. This is a diagram showing the transition of the battery voltage when the control of the present invention is used. This is a diagram showing the transition of the battery voltage when the control of the present invention is not used. This is a diagram showing an example of the display of the battery control device indicator. This is a circuit diagram showing another example of the equivalent circuit. This is a circuit diagram showing yet another example of the equivalent circuit.

[0010] Embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a block diagram showing the hardware configuration of a battery system 100 equipped with an embodiment of the battery control device 1 according to the present invention. The battery system 100 includes a battery control device 1, an inverter 2, a load 3 such as a motor, and a higher-level controller 4. The output voltage of the battery control device 1 is a DC voltage that fluctuates depending on the remaining capacity of the battery and the output current, and may not be suitable for directly supplying power to the load 3. Therefore, the inverter 2 converts the output voltage of the battery control device 1 into a three-phase AC and supplies it to the load 3. The battery control device 1 and the inverter 2 are controlled by the higher-level controller 4.

[0011] The same configuration applies when supplying DC voltage, other multiphase AC, or single-phase AC to load 3. When load 3 outputs power, by making inverter 2 a bidirectional inverter, the power output by load 3 can be stored in the battery module in battery control device 1. By connecting a charging system in parallel with inverter 2, it is also possible to charge the battery module as needed.

[0012] The battery control device 1 transmits information regarding the battery status, such as the state of charge (SOC), state of health (SOH), maximum charge / discharge current (allowable current value), battery temperature, and whether or not there is a battery abnormality, to the higher-level controller 4. Based on this information, the higher-level controller 4 performs energy management and detects battery abnormalities. If the higher-level controller 4 determines that the battery control device 1 should be disconnected from the inverter 2 or load 3, it transmits a disconnection command to the battery control device 1.

[0013] The battery control device 1 comprises one or more battery modules 11 consisting of multiple batteries, a battery controller 12 that monitors, estimates, and controls the state of the batteries, a relay 13 that intermittently switches the output of the battery control device 1, a current sensor 14 that measures the current flowing through the battery modules 11, a voltage sensor 15 that measures the voltage of the battery modules 11, a leakage current sensor 16 that measures the insulation resistance between the battery control device 1 and ground, a temperature sensor 17 that measures the battery temperature, and a circuit breaker 18 that is controlled according to the output voltage of the battery control device 1. The battery control device 1 comprises two battery modules 11 connected in series via the circuit breaker 18. The battery controller 12 comprises a CPU 121 that performs various calculations and a storage unit 122 that stores a data table, which will be described later.

[0014] The battery module 11 has multiple individual batteries and includes circuits for measuring the internal temperature of the battery module 11 and the voltage of each individual battery, as well as circuits for charging and discharging each individual battery as needed. This makes it possible to monitor and adjust the voltage of each individual battery, and to measure temperature information necessary for estimating the battery state, whose characteristics change with temperature.

[0015] A current sensor 14 and a pair of relays 13 are connected in series to the series-connected battery modules 11. The current sensor 14 measures the current value necessary to monitor and estimate the state of the battery modules 11. By controlling the opening and closing of the pair of relays 13 based on commands from the higher-level controller 4, the output of the battery control device 1 can be interrupted or connected. If the voltage of the battery modules 11 becomes a high voltage, for example, 100V or more, a switch can be added in series with the relays 13 to manually interrupt the power input and output to the battery control device 1. By forcibly interrupting the power using a switch, it is possible to prevent short circuits and other problems during the assembly and disassembly of the battery control device 1, and during accident response to equipment equipped with the battery control device 1.

[0016] When multiple battery modules 11 are connected in parallel, a relay 13, a switch, and a current sensor 14 may be provided in each row, or a relay 13, a switch, and a current sensor 14 may be provided only in the output section of the battery control device 1. Alternatively, a relay 13, a switch, and a current sensor 14 may be provided in both each row and the output section of the battery control device 1.

[0017] Relay 13 may consist of a single relay device, or it may consist of a combination of a main relay, a precharge relay, and a resistor. In the latter configuration, the precharge relay and the resistor are connected in series, and the main relay is connected in parallel. When connecting relay 13 to the line of battery control device 1, the precharge relay is connected first. Since the current flowing through the precharge relay is limited by the resistor connected in series, the inrush current caused by a single relay device can be limited. Then, the battery controller 12 connects the main relay after the current flowing through the precharge relay has become sufficiently small. The timing of connecting the main relay may be based on the current flowing through the precharge relay, or on the voltage across the resistor or the terminal voltage of the main relay. The time elapsed since connecting the precharge relay may also be used as a reference.

[0018] The voltage sensor 15 measures the voltage value necessary for monitoring and estimating the state of the battery module 11. The voltage sensor 15 is connected in parallel to one or more battery modules 11. A leakage current sensor 16 is connected to the battery module 11 to detect a state in which leakage current may occur, i.e., a state in which the insulation resistance has decreased, before leakage current occurs, thereby preventing accidents.

[0019] The measured values ​​from the battery module 11, current sensor 14, voltage sensor 15, and leakage sensor 16 are transmitted to the battery controller 12. Based on the received measured values, the battery controller 12 monitors, estimates, and controls the battery state of the battery module 11. Control here includes, for example, charging and discharging each unit battery to equalize the voltage of each unit battery, power control of each sensor, addressing of each sensor, and control of the relay 13 connected to the battery controller 12. The CPU 121 performs the calculations necessary for monitoring, estimating, and controlling the battery state.

[0020] The battery control device 1 may include a fan for system cooling, which can be controlled by the battery controller 12. By having the battery control device 1 handle the cooling, the battery controller 12 can reduce the amount of communication it has to do with the higher-level controller 4.

[0021] In the example shown in Figure 1, the voltage sensor 15 and leakage sensor 16 are separate components from the battery controller 12, providing flexibility in system design. However, the voltage sensor 15 and leakage sensor 16 could also be built into the battery controller 12. This reduces the number of harnesses and the effort required for sensor installation. However, building the sensors into the battery controller 1 may limit the scale of the battery control device 1 that can be handled (maximum output voltage, current, etc.), so in such cases, it is preferable to use separate components for the sensors.

[0022] Figure 2 is a functional block diagram of the battery controller 12. The CPU 121 of the battery controller 12 executes a program to realize a system comprising multiple functional blocks (degradation state estimation unit 1201, charge state estimation unit 1202, parameter calculation unit 1203, allowable current calculation unit 1204). The configurations specified by "units" such as the degradation state estimation unit 1201 are functions realized by the program. "Units" may be replaced with other terms such as "means," "module," or "unit" in addition to "function." Functional blocks may be realized by hardware such as integrated circuits. The battery controller 12 includes a storage unit 122. The storage unit 122 holds a battery data table 1205.

[0023] The degradation state estimation unit 1201 and the charge state estimation unit 1202 receive current I, voltage V, and temperature T from a sensor group 1400 including a current sensor 14, a voltage sensor 15, and a temperature sensor 17. Based on this input information, the degradation state estimation unit 1201 estimates the degradation state of the battery. The target of estimation can be any indicator that represents the degradation state of the battery. For example, a decrease in battery capacity can be used. The decrease in battery capacity can be estimated by the following method, for example.

[0024] The degradation state estimation unit 1201 integrates the charge and discharge amounts Q_AB from one time point A to another time point B. The degradation state estimation unit 1201 refers to the charge state estimation unit 1202 to calculate OCV_A at time A and OCV_B at time B, and refers to the initial state battery data table 1205 to find the charge and discharge amount Q_AB corresponding to OCV_A and the charge and discharge amount Q'_AB corresponding to OCV_B. The degradation state estimation unit 1201 uses (Q'_AB) / (Q_AB) as the capacity reduction rate (SOHQ). The degradation state estimation unit 1201 uses the capacity reduction rate, or the capacity reduction amount Q_deg obtained by multiplying the capacity reduction rate by the initial battery capacity Q_0, as an indicator of the battery's degradation state.

[0025] The State of Health (SOH) may also be calculated using the resistance increase rate. For example, the ratio of the internal resistance in the initial state of the battery to the current internal resistance is defined as the resistance increase rate, and this resistance increase rate is defined as the SOH. Alternatively, the SOH of the positive and negative electrodes of a battery may be determined based on the capacity decrease rate and resistance increase rate of each electrode.

[0026] The charge state estimation unit 1202 estimates the battery's charge state based on the current I, voltage V, and temperature T output from the sensor group 1400 (14, 15, 17) and a model of the battery's equivalent circuit. The battery controller 12 uses the equivalent circuit model of a lithium-ion battery to evaluate the battery's performance in the charge state. The equivalent circuit model will be explained with reference to Figures 3 and 4.

[0027] Figure 3 is a graph showing an example of the voltage behavior of a battery when a square wave current is applied to it. (A) shows the square wave current I applied to the battery, and (B) shows the battery voltage V. In both cases, the horizontal axis is elapsed time. When the square wave current I of (A) 31 is applied to the battery, the battery voltage V, that is, the battery's CCV (closed circuit voltage), changes as shown in the waveform 32 of (B). This voltage V waveform 32 can be broadly divided into three components: the DC voltage component I × Ro (DC resistance component), the polarization voltage component Vp, and the OCV fluctuation component ΔOCV.

[0028] The first component, the DC voltage component I × Ro, responds instantaneously to changes in current I. That is, it rises rapidly in conjunction with the rising edge of current I, remains at a constant level, and then disappears as current I falls. The second component, the polarization voltage component Vp, fluctuates with a delay in response to changes in current I. That is, it gradually rises after the rising edge of current I and gradually decreases after the falling edge of current I. The third component, the OCV fluctuation component ΔOCV, represents the change in the battery's OCV, which is the OCV value before charging began. １ OCV is the OCV value after charging has started. ２ This corresponds to the difference between the two values. This OCV fluctuation component ΔOCV corresponds to the change in the battery's charge state according to the amount of charge and discharge.

[0029] Figure 4 shows an example of an equivalent circuit model of a battery (cell) 10. In Figure 4, Ro represents the DC resistance component of the resistive element. The charge state estimation unit 1202 calculates the DC voltage component I × Ro by multiplying the DC resistance component Ro by the current I. Rp represents the polarization resistance component of the resistive element, and Cp represents the polarization capacitance component of the capacitor element connected in parallel with the resistive element. RpCp is connected in series with Ro. The battery voltage (CCV) is obtained by adding the polarization voltage component Vp, the DC resistance component Ro, and the open-circuit voltage OCV. The charge state estimation unit 1202 determines the polarization voltage component Vp from the current I and the charge / discharge time t. Vp = I × Rp × (1 - exp[-t / RpCp])

[0030] As can be seen from the equivalent circuit shown in Figure 4, the polarization voltage component Vp exhibits exponential fluctuations based on the time constant RpCp. One factor that causes polarization of the internal resistance in a battery is the lithium concentration distribution inside and on the surface of the electrode active material particles. That is, the state in which polarization progresses and charge accumulates at Cp on the equivalent circuit corresponds to the state in which lithium accumulates on the surface of the negative electrode active material particles of the battery during charging, creating a lithium concentration difference between the surface and the interior. The amount of charge accumulated at Cp corresponds to the difference between the average SOC (first charge state) and the local SOC (second charge state) on the surface of the electrode active material particles. The average SOC compensates for fluctuations in SOC in different parts and localities inside the battery and indicates the average charge state. If all parts inside the battery are uniformly charged or discharged, the average SOC will be the same value as the local SOC. If the charge state differs in different parts and localities inside the battery, the average SOC will be a different value from the average value of the local SOC.

[0031] In the allowable current calculated using the prior art described in Patent Document 1, the battery voltage sometimes deviated from the upper and lower voltage limits. This is because a concentration distribution of lithium ions occurs inside the electrodes during charging and discharging, resulting in a non-uniform state of charge (SOC), but conventional SOC estimation methods based on current-integrated capacity cannot reflect this SOC distribution.

[0032] To calculate the maximum current while ensuring that the battery voltage does not deviate from its upper or lower limits, the battery control device utilizes the battery's open-circuit voltage (OCV) and several parameters related to the battery's internal state, such as internal resistance. In energy storage devices, particularly those for mobile vehicles where irregular currents constantly flow or for grid-connected stabilization, it is necessary to consider not only the internal resistance (DC resistance) that causes voltage changes at the moment current flows through the battery, but also the effect of internal resistance (polarization resistance) that causes voltage changes when current is continuously flowing.

[0033] The allowable current calculation unit 1204 uses local SOC, which includes the influence of lithium ion distribution, rather than average SOC, to calculate the allowable current of a lithium-ion battery. The accumulation of lithium affects the amount of charge of the capacitor element. Therefore, the allowable current calculation unit 1204 can determine the local SOC, which is influenced by the distribution of lithium ions, based on the average SOC and the amount of charge of the capacitor element. The amount of charge accumulated in Cp corresponds to the difference between the local SOC and the average SOC. The allowable current calculation unit 1204 can calculate this difference based on the amount of charge of the capacitor element and calculate the local SOC by subtracting this from the average SOC or adding it to the average SOC. To convert the amount of charge of the capacitor element into this difference, for example, a specific conversion coefficient obtained by experiment or computer simulation can be multiplied by the amount of charge.

[0034] The charge state estimation unit 1202 calculates the average SOC of the battery from the relationship between the charge / discharge charge and SOC, for example, based on the charge / discharge charge ΔQ obtained by integrating the current I. Alternatively, the charge state estimation unit 1202 may calculate the average SOC of the battery based on the OCV of the battery obtained by analyzing the battery's CCV using an equivalent circuit model. Specifically, the charge state estimation unit 1202 estimates the battery's charge state using the battery temperature, current, and voltage detected by the sensor group 1400 and the battery's data table 1205. Alternatively, the charge state estimation unit 1202 may calculate the average SOC of the battery by combining the average SOC of the battery obtained from the integration of current I and the average SOC of the battery obtained from the analysis of the battery's CCV using a method such as weighted averaging.

[0035] Parameters such as DC resistance and polarization resistance change depending on the battery's State of Charge (SOC) and temperature. Therefore, the battery controller 12 prepares a data table 1205 or function that associates the SOC and temperature with the values ​​of parameters such as DC resistance and polarization resistance. The battery controller 12 then estimates the SOC based on measurement information of current, voltage, and temperature, and uses the data table 1205 or function to determine the parameter values ​​based on the SOC.

[0036] As shown in Figure 5, the battery data table 1205 stores the DC resistance component Ro (Ω), polarization resistance Rp (Ω), and polarization capacitance Cp (F) in relation to their respective temperatures T (Celsius), SOC (%), and OCV (V). The battery data table 1205 stores the SOC as SOC １ ~SOC Ｍ For each of these, the OCV V_1.1 to V_M.L, DC resistance component Ro_1.1 to Ro_M.L, polarization resistance Rp_1.1 to Rp_M.L, and polarization capacitance Cp_1.1 to Cp_M.L are recorded when the temperature T (Celsius) is T_1 to T_L. The battery data table 1205 is an example of a data structure that has battery performance parameters. The DC resistance component Ro (Ω), polarization resistance Rp (Ω), and polarization capacitance Cp (F) of the equivalent circuit model are examples of battery performance parameters, respectively.

[0037] The relationship between temperature, state of temperature (SOC), OCV, DC resistance, polarization resistance, and polarization capacitance may be defined as a function (graph) as a data structure. Figure 6A is, for example, a graph of SOC and DC resistance component Ro at 25 degrees Celsius, and Figure 6B is a graph of SOC and polarization resistance Rp at 25 degrees Celsius. Similar graphs are obtained for OCV and polarization capacitance Cp. The same definitions apply to temperatures other than 25 degrees Celsius.

[0038] Parameter calculation unit 1203 calculates the current parameter values of the DC resistance component Ro (Ω), polarization resistance Rp (Ω), and polarization capacitance Cp (F) based on the battery degradation state estimated by the degradation state estimation unit 1201. The parameter calculation unit 1203 updates the parameter values calculated for the parameter values in the initial state of the battery and registers them in the battery data table 1205. This application cites Japanese Patent Application Laid-Open No. 2020-134279 for the details of the parameter calculation.

[0039] Allowable current calculation unit 1204 refers to the DC resistance, polarization resistance, and polarization capacitance of the battery stored in the battery data table 1205 based on the current SOC and temperature of the battery, and calculates the internal resistance and allowable current of the battery. The calculation of the allowable current is for maintaining the safety of the battery control device 1 by limiting the current so as not to exceed the reference value as part of the safety function for preventing overvoltage of the battery.

[0040] Figure 7 is an example of a flowchart of the control operation during discharge of the allowable current calculation unit 1204. The allowable current calculation unit 1204 refers to the battery data table 1205 based on the average SOC from the charge state estimation unit 1202 and the temperature T from the sensor group 1400, and acquires the OCV, DC resistance, polarization resistance, and polarization capacitance. The allowable current calculation unit 1204 can calculate the allowable current by dividing the absolute value of the difference between the OCV and the limit voltage (lower limit voltage or upper limit voltage) by the internal resistance. The allowable current calculation unit 1204 calculates a candidate for the discharge allowable current (candidate allowable current Imax_m) (S700).

[0041] The candidate for the discharge allowable current is calculated using, for example, the following formula. Imax_1 = (|OCV - Vmin|) / R Vmin is the lower limit voltage and R is the internal resistance of the battery. The internal resistance R of the battery is calculated using, for example, the following formula. R = Ro + Rp(1 - e －ｔ／ＲｐＣｐ ) t is the time (seconds).

[0042] Next, the allowable current calculation unit 1204 calculates the average SOC after n seconds based on the discharged charge amount ΔQ obtained by integrating the allowable current (Imax_m) over the discharge time (n seconds) and the SOC at the start of discharge (S701). Next, the allowable current calculation unit 1204 calculates the charge amount of the capacitor element. The allowable current calculation unit 1204 multiplies the charge amount Q of the capacitor element by the specific conversion coefficient as described above to calculate the differential SOC (ΔSOC), which is the difference between the average SOC and the local SOC (S702). The allowable current calculation unit 1204 calculates the local SOC (effective SOC) by subtracting the differential SOC from the average SOC.

[0043] Based on the local SOC and the temperature, the allowable current calculation unit 1204 refers to the battery data table 1205 to extract Ro, Rp, and Cp. Then, the allowable current calculation unit 1204 substitutes the extracted values into the formula for the internal resistance R to calculate the internal resistance R of the battery after n seconds (S703). Next, the allowable current calculation unit 1204 calculates (Imax_1)*R to predict the battery voltage after n seconds (S704).

[0044] Next, the allowable current calculation unit 1204 compares the battery voltage after n seconds (S704) with the lower limit voltage to determine whether the battery voltage has deviated from the lower limit voltage (S705). If the allowable current calculation unit 1204 rejects this determination, that is, if it determines that the battery voltage is within the lower limit voltage, it notifies the charge / discharge execution function of the battery controller 12 of the candidate allowable current (S700) as the confirmed allowable current (S707), and terminates the flowchart. On the other hand, if the allowable current calculation unit 1204 affirms this determination, that is, if it determines that the battery voltage has deviated from the lower limit voltage, it multiplies the candidate allowable current by a predetermined correction coefficient, slightly increases it, updates the candidate allowable current (k) (S706), returns to step S701, calculates the battery voltage based on the updated candidate allowable current (k), and repeatedly determines whether it has deviated from the upper or lower limit voltages. By repeatedly executing this control flow, the allowable current calculation unit 1204 can detect an allowable current that takes into account the Li concentration distribution on the surface and inside the electrode active material particles, and that avoids deviation from the battery voltage limit voltage (upper or lower limit voltage). Figure 7 illustrates an example of the control operation flowchart of the allowable current calculation unit 1204 during discharge, but this can be applied to the control operation during charging. In this case, the upper limit voltage can be used instead of the lower limit voltage, and the correction coefficient can be changed to one that slightly reduces the candidate allowable current.

[0045] Here, Figures 8 and 9 will be used to provide a supplementary explanation of the control operation in Figure 7. Figure 8 shows an example where the internal resistance is calculated based on the average SOC, and the optimization of the allowable current based on Figure 7 is not performed. Figure 8 shows the relationship between the SOC (average SOC, local SOC) and the battery voltage (Voltage) with respect to the discharge current (Current). By utilizing these characteristics, the allowable current calculation unit 1204 can predict the changes in SOC and voltage. In Figure 8, T １ (A) shows the current time, and the changes in SOC and battery voltage up to n seconds later are shown. １indicates that the aforementioned Imax_1 (discharge allowable current) has been input to the battery for n seconds. (B) shows that during that time, lithium accumulates on the surface of the electrode active material particles and the local SOC deviates from the average SOC (ΔL1). When the local SOC enters a region where the progress of lithium accumulation becomes highly resistive, the differential ΔV of the voltage drop becomes large and the battery voltage exceeds the lower limit voltage (V Ｌｉｍｉｔ ) and goes beyond it.

[0046] FIG. 9 shows that the allowable current calculation unit 1204 executes the optimization process of the allowable current value (FIG. 7), and finally, by suppressing the SOC distribution as shown in (B) with the determined allowable current: Imax determined as the allowable current (ΔL2 < ΔL1), it becomes possible to suppress the battery voltage to a state where the voltage has no inflection point. As a result, it is possible to prevent the battery voltage from deviating from the lower limit voltage (V Ｌｉｍｉｔ ).

[0047] FIG. 10 shows a display example of the indicator 900 of the battery control device 1. This may be displayed on a monitor or the like of a mobile terminal device, or may be transmitted to a higher-level system. The battery control device 1 outputs, as outputs, in addition to general voltage, temperature, current, SOC, SOHR, and SOHQ, the local SOC and allowable current value inside the battery specific to the present invention. Therefore, the user of the battery control device 1 can know the allowable current predicted with high accuracy.

[0048] Note that equivalent circuits other than those shown in this embodiment can also be used. For example, an equivalent circuit having an RC parallel part representing each of the positive electrode side and the negative electrode side as shown in FIG. 11A can also be used. In this case, instead of the battery data table 1205, a positive electrode data table and a negative electrode data table having a similar configuration are provided. Also, for example, an equivalent circuit capable of simulating the current distribution 1500 and SOC distribution 1502 in the electrode depth direction as shown in FIG. 11B can be used. In this case, the present invention can be applied by setting the average SOC and local SOC in each RC parallel circuit in the depth direction.

[0049] According to the embodiments described above, the first disclosure is a battery control device 1 for controlling the charging and discharging of a battery cell 10, comprising: a detection unit (sensor group) 1400 for detecting the battery state; a charge state estimation unit 1202 for estimating the charge state (SOC) of the battery based on detection data from the detection unit; and an allowable current calculation unit 1204 for calculating the allowable current for charging and discharging the battery based on an equivalent circuit model of the battery, which includes a resistive element and a capacitor element (Figure 4), and a battery data table 1205 that associates the resistive element, the capacitor element, the battery state, and the charge state. The allowable current calculation unit 1204 is characterized in that it takes the SOC estimated by the charge state estimation unit 1202 as the first SOC (average SOC), determines a second SOC (local SOC) based on the average SOC and the charge amount of the capacitor element, and calculates the allowable current by referring to the battery data table based on the local SOC and the detection data. According to the first disclosure, a battery control device is provided that can predict even the rapid rise or fall of the battery voltage when the battery is charged or discharged with a large current, with a low computational load using an equivalent circuit, and therefore can determine the allowable current with high accuracy.

[0050] Furthermore, the second disclosure is characterized in that, in the first disclosure, the charge amount of the capacitor element includes the effect of lithium accumulated on the surface of the electrode active material particles. According to the second disclosure, the allowable current can be determined with high accuracy by excluding the effect based on lithium accumulation.

[0051] Furthermore, the third disclosure is characterized in that, in the first or second disclosure, the allowable current calculation unit 1204 multiplies the charge amount of the capacitor element by a predetermined coefficient and subtracts this from the average SOC to obtain the local SOC. According to the third disclosure, the local SOC can be easily determined.

[0052] Furthermore, the fourth disclosure is characterized in that, in any of the first to third disclosures, the allowable current calculation unit 1204 refers to a battery data table to determine the internal resistance of the battery cell 10, and determines the allowable current based on the difference between the open-circuit voltage of the battery and the limiting voltage (upper or lower limit voltage), and the internal resistance.

[0053] Furthermore, the fifth disclosure is characterized in that, in any of the first to fourth disclosures, when determining the allowable current, the allowable current calculation unit 1204 sets candidate allowable currents that are candidates for the determined allowable current, determines the battery voltage based on the candidate allowable current, compares the battery voltage with the limiting voltage, corrects the candidate allowable current if the battery voltage deviates from the range of the limiting voltage, and if the battery voltage based on the corrected candidate allowable current falls within the range of the limiting voltage, the corrected candidate allowable current becomes the determined allowable current. This makes it possible to predict the allowable current with high accuracy while reliably preventing the battery voltage from deviating from the range of the limiting voltage.

[0054] The sixth disclosure is a battery control method for controlling the charging and discharging of a battery, characterized in that it detects the battery state, estimates the charge state of the battery based on the detected data, and calculates an allowable current for charging and discharging the battery based on an equivalent circuit model of the battery which includes a resistive element and a capacitor element, and a data structure relating the resistive element, the capacitor element, the battery state, and the charge state, and the calculation of the allowable current is characterized in that the estimated charge state is set as the first charge state, a second charge state is determined based on the first charge state and the charge amount of the capacitor element, and the allowable current is calculated by referring to the data structure based on the second charge state and the detected data detected by the detection unit.

[0055] The present invention is not limited to the configurations described in the embodiments, but can be appropriately configured based on the content described in the claims. The above embodiments are examples for carrying out the present invention. When carrying out the present invention, only some of the configurations of the embodiments may be implemented. When carrying out the present invention, additional configurations not described in the embodiments may be implemented. When carrying out the present invention, some of the configurations of the embodiments may be replaced with configurations not described in the embodiments. Modules, means, and units may be configured by combining electronic circuits.

[0056] 1 Battery control device 2 Inverter 3 Load 4 Higher-level controller 10 Battery cell 11 Battery module 12 Battery controller 13 Relay 14 Current sensor 15 Voltage sensor 16 Leakage sensor 17 Temperature sensor 18 Circuit breaker 100 Battery system 121 CPU 122 Memory unit 1201 Degradation state estimation unit 1202 Charge state estimation unit 1203 Parameter calculation unit 1204 Allowable current calculation unit 1205 Battery data table

Claims

A battery control device that controls the charging and discharging of a battery, A detection unit for detecting the battery status, A charge state estimation unit that estimates the charge state of the battery based on the detection data from the detection unit, and, The equivalent circuit model of the battery includes a resistive element and a capacitor element, and an allowable current calculation unit that calculates the allowable current for charging and discharging the battery based on the equivalent circuit model, the resistive element, the capacitor element, the battery state, and the charging state. The allowable current calculation unit is, The charge state estimated by the charge state estimation unit is defined as the first charge state, and a second charge state is determined based on the first charge state and the charge amount of the capacitor element. Based on the second charging state and the detected data, the allowable current is calculated by referring to the data structure. Battery control device. 　 The charge amount of the capacitor element includes the effect of lithium accumulated on the surface of the electrode active material particles. The battery control device according to claim 1. 　 The allowable current calculation unit multiplies the charge amount of the capacitor element by a predetermined coefficient and subtracts this from the first charge state to determine the second charge state. The battery control device according to claim 1. 　 The allowable current calculation unit is, The internal resistance of the battery is determined by referring to the aforementioned data structure. The allowable current is determined based on the difference between the open-circuit voltage and the limiting voltage of the battery, and its internal resistance. The battery control device according to claim 1. 　 When determining the allowable current, the allowable current calculation unit, Set candidate allowable currents that are candidates for the confirmed allowable current, Based on the candidate allowable current, determine the battery voltage. The battery voltage is compared with the limiting voltage, If the battery voltage deviates from the range of the limiting voltage, the candidate allowable current is corrected. If the battery voltage based on the corrected candidate allowable current falls within the range of the limiting voltage, the corrected candidate allowable current shall be set as the confirmed allowable current. The battery control device according to claim 4. 　 A battery control method for controlling the charging and discharging of a battery, Detects the battery status, Based on the detected data, the charge state of the battery is estimated, and then, Based on the equivalent circuit model of the battery, which includes a resistive element and a capacitive element, and a data structure relating the resistive element, the capacitive element, the battery state, and the charging state, the allowable current for charging and discharging the battery is calculated. The calculation of the allowable current is as follows: The estimated charge state is defined as the first charge state, and the second charge state is determined based on the first charge state and the charge amount of the capacitor element. Based on the second charging state and the detected data, the allowable current is calculated by referring to the data structure. Battery control method.

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