Managing device, electrical storage device, managing method and program

Abstract

To provide a managing device and the like that can improve a charging acceptability function of an electric storage element.SOLUTION: A managing device comprises: an acquisition unit that acquires a current value and voltage value of an electric storage element; and a calculation unit that calculates a current limit value along a current limit characteristic of the electric storage element on the basis of internal resistance of the electric storage element, and the acquired current value and voltage value.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a management device for energy storage elements, an energy storage device, a management method, and a program. [Background technology]

[0002] Constant current constant voltage (CCCV) charging is a widely known method for charging storage elements. CCCV charging is a method in which charging is performed at a constant current (CC) in the initial stage of charging, and then switched to constant voltage (CV) when the storage element reaches a specified voltage value.

[0003] Patent Document 1 discloses a charging device that provides a region between CC charging and CV charging in which charging is performed while reducing the charging current. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5525862 Summary of the Invention [Problem to be solved by the invention]

[0005] If a region in which charging is performed while the charging current is reduced is provided between CC charging and CV charging, the charge acceptance performance of the storage element cannot be fully utilized depending on the charging current in this region.

[0006] An object of the present disclosure is to provide a technique capable of improving the charge acceptance performance of an energy storage element. [Means for solving the problem]

[0007] A management device according to one embodiment of the present disclosure includes an acquisition unit that acquires a current value and a voltage value of a storage element, and a calculation unit that calculates a current limiting value in accordance with the current limiting characteristics of the storage element based on the internal resistance of the storage element and the acquired current value and voltage value. Effect of the Invention

[0008] According to the present disclosure, the management device can improve the charge acceptance performance of the energy storage element. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing an overview of a solar power generation system. [Diagram 2] 1 is a block diagram showing an example of the configuration of a power storage device and a charging device in which a management device according to a first embodiment is mounted; [Diagram 3] FIG. 2 is a plan view of an electric storage element (battery). [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Diagram 5] 5A and 5B are diagrams illustrating a concept of a method for calculating a current limit value. [Figure 6] 11 is a diagram illustrating a case where a current limit value is calculated using a predetermined coefficient. FIG. [Figure 7] 11 is a diagram illustrating a case where a current limit value is calculated using a predetermined coefficient. FIG. [Figure 8] 10 is a flowchart illustrating an example of a calculation process of a current limit value. [Figure 9] 13 is a diagram illustrating the concept of a method for calculating a current limit value in the second embodiment. FIG. [Figure 10] 10 is a flowchart illustrating an example of a calculation process procedure for a current limit value in the second embodiment. [Figure 11] 13 is a diagram illustrating the concept of a method for calculating a current limit value in the third embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The management device includes an acquisition unit for acquiring a current value and a voltage value of the storage element, and an internal resistance value of the storage element. and a calculation unit that calculates a current limiting value in accordance with a current limiting characteristic of the storage element based on the acquired current value and voltage value.

[0011] Here, the "current limiting characteristic" refers to a profile that indicates the relationship between the voltage value of the storage element and the current limiting value. The "current limit value" refers to the limit value (upper limit value) of the charging current value of the storage element. The "internal resistance" may be the ohmic resistance of the power storage element, or may be the ohmic resistance plus non-ohmic resistance.

[0012] The management device calculates a current limit value in accordance with the current limit characteristic, i.e., a target value, using a current limit characteristic that defines the relationship between the voltage value of the storage element and the current limit value. The management device may calculate, for example, a current limit value on the current limit characteristic, or a current limit value that is approximate to the current limit value on the current limit characteristic. The calculated current limit value is transmitted, for example, to an external charging device. The external charging device charges the storage element so as not to exceed the current limit value received from the management device.

[0013] The current limit value is calculated based on the current value and voltage value of the storage element (at the time of estimation) and the internal resistance of the storage element stored in advance in, for example, a storage unit of the management device. For the current value and voltage value, the change in the current value and voltage value when the current limit value is applied is predicted based on the internal resistance of the storage element, and a current value (current limit value) is obtained such that the predicted current value and voltage value are in line with the current limit characteristic. According to this method, the deviation between the calculated current limit value and the current limit characteristic can be reduced compared to the case where the current limit value is calculated by uniformly adding a predetermined coefficient set in advance to the current value without predicting the change in the current value and voltage value. Therefore, the charge acceptance performance of the storage element can be fully utilized. This makes it possible to realize advanced energy management by cooperating with the charging device while maintaining the safety of the storage element (preventing the occurrence of abnormal events such as excessive heat generation and electrodeposition).

[0014] In the management device, the current limiting characteristic may include a first region and a second region in which the current limiting value decreases according to an increase in the voltage value of the storage element, and the calculation unit may calculate the current limiting value along the second region of the current limiting characteristic. The first region may be a region in which the current limit value is constant regardless of the voltage value of the power storage element.

[0015] The first and second regions may both be regions in which the voltage value of the storage element is lower than the voltage during constant voltage (CV) charging in constant current constant voltage (CCCV) charging. The management device reduces the second region of the current limiting characteristics, i.e., the current limiting value after constant current (CC) charging, in accordance with an increase in the voltage value, while taking into account the internal resistance. This makes it possible to delay the timing of reducing the current limiting value (expand the constant current charging region) compared to conventional methods, thereby improving the charge acceptance performance of the storage element.

[0016] In the management device, the calculation unit may calculate, as the current limit value, a value at which an estimated current value estimated based on the current value, voltage value, and internal resistance using an equivalent circuit model of the storage element intersects with the current limit characteristic.

[0017] According to the above configuration, the management device uses an equivalent circuit model of the energy storage element to obtain an estimated current value corresponding to the current value and voltage value of the energy storage element at the estimation time. The estimated current value can be easily calculated from the internal resistance of the energy storage element obtained in advance from actual measurement data, etc. By calculating the intersection between the estimated current value and the current limiting characteristic, it is possible to easily and accurately calculate a current limiting value that is suitable for the state of the current value and voltage value of the energy storage element at the estimation time.

[0018] In the management device, the calculation unit calculates at least one of a state of charge and a temperature of the storage element. The current limiting value may be calculated based on the internal resistance corresponding to the

[0019] The state of charge may be, for example, the SOC (State of Charge) of the storage element. According to the above configuration, since the current limit value is calculated based on the internal resistance corresponding to the state of charge or temperature of the storage element, the current limit value that appropriately reflects the state of the storage element can be calculated, and the charge acceptance performance can be further improved.

[0020] In the management device, the calculation unit may calculate the current limit value based on the internal resistance corrected using a correction coefficient.

[0021] The correction coefficient may represent, for example, the rate at which the current limit value is increased or decreased. By correcting the internal resistance using the correction coefficient, the degree of freedom in calculating the current limit value is increased.

[0022] The management device may vary the correction coefficient in response to the current value.

[0023] According to the above configuration, by changing the correction coefficient according to the current value of the storage element at the estimation time, the state of the current value of the storage element can be reflected in the calculation of the current limit value, and a more suitable current limit value can be calculated.

[0024] The management device may change the correction coefficient based on a result of comparison between the acquired current value and voltage value of the storage element and the current limiting characteristic of the storage element.

[0025] The comparison result between the current limiting characteristic and the current value and voltage value at the time of estimation of the storage element may be, for example, a comparison result between the magnitude relationship of the current value and voltage value at the time of estimation of the storage element and the current limiting characteristic. By changing the correction coefficient based on the comparison result between the current value and voltage value at the time of estimation of the storage element and the current limiting characteristic, the state of the current value and voltage value of the storage element can be reflected in the calculation of the current limiting value, and a more suitable current limiting value can be calculated.

[0026] The power storage device includes a power storage element and any one of the management devices described above.

[0027] The management method involves a computer executing a process to acquire current and voltage values ​​of a storage element, and to calculate a current limiting value in accordance with the current limiting characteristics of the storage element based on the internal resistance of the storage element and the acquired current and voltage values.

[0028] The program causes the computer to execute a process of acquiring current and voltage values ​​of a storage element, and calculating a current limiting value in accordance with the current limiting characteristics of the storage element based on the internal resistance of the storage element and the acquired current and voltage values.

[0029] Hereinafter, the present disclosure will be specifically described with reference to the drawings showing the embodiments thereof.

[0030] (First embodiment) Fig. 1 shows an overview of a solar power generation system. The solar power generation system includes a solar power generation device P, a power storage device 10, and a charging device 20. The solar power generation device P converts sunlight into electricity and outputs it. The electricity generated by the solar power generation device P is supplied to a load 60 via the charging device 20. Furthermore, surplus electricity generated by the solar power generation device P is stored in the power storage device 10 via the charging device 20. Instead of the solar power generation device P, a power generation device using other renewable energy such as wind power (renewable energy power generation device) may be used.

[0031] The charging device 20 may be, for example, a power conditioner. The charging device 20 is connected to the solar power generation device P, the power storage device 10, the load 60, and the power system 70 via lines and the like. The charging device 20 converts the direct current generated by the solar power generation device P into alternating current. The charging device 20 outputs the converted alternating current to a power load 60 such as a home electrical appliance or a motor (power load) of a facility. The charging device 20 also supplies power received from the power system 70 to the load 60 and the power storage device 10. The power storage device 10 receives power from the solar power generation device P or the power system 70 via the charging device 20 and stores the received power.

[0032] FIG. 2 is a block diagram showing an example of the configuration of the power storage device 10 and the charging device 20 equipped with the management device 40 according to the first embodiment. As shown in FIG. 2, the power storage device 10 includes a battery pack 31 including a plurality of secondary batteries (hereinafter also simply referred to as batteries) 30, a BMU (Battery Management Unit) 40 that manages each battery 30, a current interrupt device 51, a current measuring resistor 52, and a temperature sensor 53. The BMU 40 is an example of the management device 40. The battery 30 is an example of the power storage element 30. As an example, the battery 30 is a lithium ion secondary battery. The battery 30 is not limited to a battery pack, and may be a single cell. A power storage element other than a battery may be used. A part of the functions of the BMU 40 may be assigned to a monitoring device (for example, a CMU: Cell Monitoring Unit) not shown.

[0033] The battery pack 31, the current interruption device 51, and the current measurement resistor 52 are connected in series via an electric path L. The positive electrode of the battery pack 31 is connected to a positive external terminal 54 via the current measurement resistor 52 and the current interruption device 51. The negative electrode of the battery pack 31 is connected to a negative external terminal 55.

[0034] 2 shows an example in which the current measurement resistor 52 is connected to the positive electrode of the battery pack 31. Alternatively, the current measurement resistor 52 may be connected to the negative electrode of the battery pack 31.

[0035] The current interruption device 51 can be configured with a mechanical switch (e.g., a relay) or a semiconductor switch such as a FET or a transistor. The current interruption device 51 is connected to the BMU 40, and is switched on / off in response to a control signal from the BMU 40. The BMU 40 turns off the current interruption device 51 to interrupt the flow of electricity between the battery pack 31 and the positive external terminal 54.

[0036] The current measurement resistor 52 is a resistor that measures the current of the current path L. The current measurement resistor 52 can measure the current of the assembled battery 31 (batteries 30) by measuring the voltage across the current measurement resistor 52, i.e., the voltage corresponding to the current of the assembled battery 31, over time. The current measurement resistor 52 is connected to the BMU 40, and outputs a signal related to the measured current to the BMU 40. Discharging and charging can be determined from the polarity (positive or negative) of the voltage across the current measurement resistor 52.

[0037] The temperature sensor 53 is disposed near the battery pack 31 and measures, by contact or non-contact, the temperature of the battery pack 31 or the surroundings of the battery pack 31 in a time series manner. The temperature sensor 53 is connected to the BMU 40 and outputs a signal related to the detected temperature to the BMU 40.

[0038] The BMU 40 includes a control unit 41, a memory unit 42, a voltage detection circuit 43, an input / output unit 44, and a communication unit 45. The BMU 40 constantly acquires measurement data including the voltage value, current value, and temperature of the battery 30, and calculates a current limit value for controlling charging of the battery 30 based on the acquired measurement data.

[0039] The control unit 41 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), The control unit 41 is an arithmetic circuit equipped with a RAM (Random Access Memory) and the like. The CPU included in the control unit 41 executes various computer programs stored in the ROM and storage unit 42, and controls the operation of each of the above-mentioned hardware components, thereby making the entire device function as a management device of the present disclosure. The control unit 41 may have functions such as a timer that measures the elapsed time from when an instruction to start measurement is given until when an instruction to end measurement is given, a counter that counts numbers, and a clock that outputs date and time information.

[0040] The storage unit 42 is a non-volatile storage device such as a flash memory. Various computer programs and data are stored in the storage unit 42. The computer programs (computer program products) stored in the storage unit 42 include a program 421 for performing processing related to charging control of the battery 30. The data stored in the storage unit 42 includes control data 422 used in the program 421.

[0041] The control data 422 includes information such as, for example, a current limit characteristic corresponding to the battery 30, an equivalent circuit model of the battery 30 used in the simulation, and various correction coefficients used in the calculation process. The current limit characteristic is a profile indicating the relationship between the voltage of the battery 30 and the current limit value, and is stored, for example, as a functional formula indicating the profile. Alternatively, the current limit characteristic may be stored as a curve indicating the profile, or data of representative points that allow the profile to be drawn by approximation may be stored.

[0042] The equivalent circuit model is described by configuration information indicating the circuit configuration, and the values ​​of each element constituting the equivalent circuit model. The storage unit 42 stores the configuration information indicating the circuit configuration, and the values ​​of each element. The control unit 41 may acquire information on the current limiting characteristics, the equivalent circuit model, and various correction coefficients in advance, for example, by communicating with an external device (not shown), and store the acquired information in the control data 422. The control data 422 may be updated at a predetermined time interval, taking into account deterioration of the battery 30.

[0043] The computer program stored in the storage unit 42 may be provided by a non-transitory recording medium 42A on which the computer program is readably recorded. The recording medium 42A is a portable memory such as a CD-ROM, a USB memory, or a Secure Digital (SD) card. The control unit 41 reads a desired computer program from the recording medium 42A using a reading device (not shown) and stores the read computer program in the storage unit 42. Alternatively, the computer program may be provided by communication. The program 421 may be deployed to be executed on a single computer or on multiple computers located at one site or distributed across multiple sites and interconnected by a communication network.

[0044] The voltage detection circuit 43 is connected to both ends of each battery 30 via a signal line, and measures the terminal voltage of each battery 30 and the total voltage of the assembled battery 31 in time series. The control unit 41 obtains the terminal voltage of each battery 30 and the total voltage of the assembled battery 31 via the voltage detection circuit 43.

[0045] The input / output unit 44 includes an input / output interface for connecting an external device. The external device connected to the input / output unit 44 includes a current measuring resistor 52 and a temperature sensor 53. The input / output unit 44 receives input of signals related to the current measured by the current measuring resistor 52 and the temperature measured by the temperature sensor 53. The control unit 41 acquires current and temperature data through the input / output unit 44. A display device (not shown) such as a liquid crystal display may be connected to the input / output unit 44. The control unit 41 outputs the calculation result of the current limit value for the battery 30 from the input / output unit 44 to the display device.

[0046] The communication unit 45 includes a communication interface for communicating with the charging device 20 via a network or the like. The communication unit 45 may be, for example, a wireless communication interface such as WiFi (registered trademark), Bluetooth (registered trademark), 4G, or 5G, or may be a wired communication interface such as CAN. The control unit 41 receives the calculation result of the current limit value for the battery 30, If a current limit value is obtained, the communication unit 45 transmits information based on the calculation result to the charging device 20. The charging device 20 receives the information transmitted from the communication unit 45, and charges the battery 30 based on the received information within a range that does not exceed the current limit value. The communication unit 45 may be communicably connected to an external device such as a personal computer or smartphone used by a user or administrator via a network interface card (not shown), and may output information based on the calculation result to these external devices. The management device 40 may include an alarm unit such as an LED lamp or a buzzer to notify the user of the calculation result.

[0047] The charging device 20 includes a current measuring resistor 21, a charging circuit 22, and a control unit 23. The charging device 20 is connected to external terminals 54, 55 of the power storage device 10. The control unit 23 is a control device for controlling the current measuring resistor 21 and the charging circuit 22, and includes a CPU, a memory, an input / output interface, a communication interface (none of which are shown), and the like. The control unit 23 controls the magnitude of the charging current via the charging circuit 22 based on the current limit value received from the BMU 40. The current measuring resistor 21 measures the charging current.

[0048] 2 shows an example in which the management device is a BMU 40. Alternatively, the management device may be located at a location remote from the battery 30. The management device may include a server device located at a location remote from the battery 30 and communicatively connected to the BMU. There is no limitation on the location where the current limit value is calculated, and the calculation may be performed, for example, by the server device. In this case, measurement data measured on the battery 30 may be transmitted to the server device by communication.

[0049] FIG. 3 is a plan view of an energy storage element (battery) 30. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3. An example of the configuration of the battery 30 will be described with reference to FIGS. 3 and 4. As described above, the battery 30 is, for example, a lithium ion secondary battery. The battery 30 is configured by housing a flat-shaped wound electrode body 301 and an electrolyte (not shown) in a hollow rectangular parallelepiped case 302. A positive electrode terminal 304 and a negative electrode terminal 305 for external connection are provided on a lid portion 303 of the case 302. The positive electrode terminal 304 and the negative electrode terminal 305 are electrically connected to a positive electrode current collector 306 and a negative electrode current collector 307, respectively. The case 302 is made of a lightweight metal material with high thermal conductivity, such as aluminum.

[0050] Although not shown in detail, the wound electrode body 301 is constructed by stacking a sheet-shaped positive electrode and a sheet-shaped negative electrode with two sheet-shaped separators between them and winding them (vertically or horizontally). The positive electrode and the negative electrode are arranged so as to be shifted from each other in the width direction of the sheet.

[0051] The positive electrode is an electrode plate in which a positive electrode active material layer is formed on the surface of a long strip-shaped positive electrode substrate made of, for example, aluminum, an aluminum alloy, or the like. The positive electrode active material layer contains a positive electrode active material. As the positive electrode active material used in the positive electrode active material layer, a material capable of absorbing and releasing lithium ions can be used. As the positive electrode active material, for example, LiFePO4 can be used, but it is not limited thereto. The positive electrode active material layer may further contain a conductive assistant, a binder, etc. One end in the width direction of the positive electrode is provided with a region where the positive electrode active material layer is not formed, and a positive electrode current collector 306 is joined to this region.

[0052] The negative electrode is an electrode plate in which a negative electrode active material layer is formed on the surface of a long strip-shaped negative electrode base material made of, for example, copper or a copper alloy. The negative electrode active material layer contains a negative electrode active material. The negative electrode active material can be a material capable of absorbing and releasing lithium ions. Examples of the negative electrode active material include graphite, hard carbon, and soft carbon. The negative electrode active material layer may further contain a binder, a thickener, and the like. A region where the negative electrode active material layer is not formed is provided at the other end in the width direction of the negative electrode, and a negative electrode current collector 307 is joined to this region.

[0053] The separator is made of a porous resin film, and examples of the porous resin film that can be used include a porous resin film made of a resin such as polyethylene (PE) or polypropylene (PP).

[0054] The electrolyte enclosed in the case 82 can be the same as that in a conventional lithium ion secondary battery. For example, an electrolyte containing a supporting salt in an organic solvent can be used. As the organic solvent, for example, aprotic solvents such as carbonates, esters, and ethers can be used. As the supporting salt, for example, lithium ions such as LiPF6, LiBF4, and LiClO4 can be used. The electrolyte may contain various additives such as a gas generating agent, a film forming agent, a dispersing agent, and a thickening agent.

[0055] 3 and 4, a square lithium ion battery including a wound electrode body 301 has been described as an example of the battery 30. Alternatively, the battery 30 may be a lithium ion battery including a laminated electrode body, or may be a cylindrical lithium ion battery, a laminated lithium ion battery, or the like. Furthermore, the battery 30 may be an all-solid-state lithium ion battery that uses a solid for the electrolyte.

[0056] Fig. 5 is a diagram for explaining the concept of a method for calculating a current limit value in this embodiment. The method for calculating a current limit value in this embodiment will be specifically explained using Fig. 5. The vertical axis of the graph shown in Fig. 5 is the current limit value (amperes [A]), and the horizontal axis is the voltage (volts [V]). In Fig. 5, the thick solid line indicates the current limit characteristic of battery 30. The voltage (voltage value) means the maximum battery voltage (maximum terminal voltage) of battery 30 included in battery pack 31.

[0057] The current limit characteristic is shown as a function of the voltage (voltage value) and the current limit value of the battery 30. As shown in FIG. shift The first area up to , the voltage of battery 30 is V shift From V c and a second region up to the voltage of the battery 30 being V c The third above V shift is the maximum current I allowed for the battery 30 max It may be the maximum voltage in the region where V can flow, or it may be a fixed value set for each battery 30. c may be the maximum charging voltage allowed for the battery 30, and is a fixed value set for each battery 30. V c The voltage may be a CV voltage of CV charging. In one region, the current limit value is constant regardless of the voltage of the battery 30, and in the second region, the current limit value decreases linearly with increasing voltage of the battery 30. The current limit characteristic is not limited to this form.

[0058] The first region in this embodiment corresponds to a region in which the battery 30 is CC-charged. The second region corresponds to a region in which, after CC charging, the battery 30 is charged while the charging current is reduced as the voltage of the battery 30 increases. The third region corresponds to a region in which the voltage of the battery 30 reaches the maximum charging voltage V c If the temperature rises above this level, stop charging. The current limiting characteristic may be generated in advance for each type of battery 30 and stored in the control data 422 of the storage unit 42. This increases the versatility of the BMU 40.

[0059] In FIG. 5, for ease of explanation, V shift and V c The difference between the actual current limiting characteristics and V shift and V c It is preferable that the difference between V and V is small (for example, 10 mV). shift and V c By making the difference between V and V smaller, i.e., making the second region narrower, the charge acceptance performance of the battery 30 can be improved. shift and V c The difference between them is zero, i.e., V shift =V c may be also possible.

[0060] The control unit 41 of the BMU 40 outputs a current limit value specified based on the current limit characteristic to the charging device 20 when charging or discharging the battery 30. The control unit 41 calculates a current limit value according to the state of the battery 30 at a predetermined interval. In the first region in this embodiment, the current limit value is , regardless of the voltage of the battery 30, the maximum current I max In the second region, the battery 30 The target current limit value differs depending on the voltage of the battery 30. Therefore, the control unit 41 calculates the current limit value for the next stage (next control cycle timing) based on the current value and voltage value of the battery 30 so as to conform to the current limit characteristic.

[0061] The current limit value indicated by the current limit characteristic is the upper limit value of the charging current. By setting the value on the current limit characteristic to the next stage current limit value, the charging limit can be made more lenient. For example, charging using solar power can be accepted without being restricted excessively to the safe side from the viewpoint of battery protection. In particular, by calculating the current limit value so as to be in line with the second region of the current limit characteristic, the charging characteristics (charge acceptance performance) of the battery 30 can be improved.

[0062] In this embodiment, the control unit 41 calculates the current limit value using the current (at the time of calculation) current and voltage values ​​of the battery 30 and the internal resistance of the battery 30. The control unit 41 calculates the next-stage current limit value so that the current and voltage values ​​of the battery 30 become equal to the current limit value and voltage value defined by the current limit characteristic. As a specific example, the control unit 41 calculates the intersection point between the current limit characteristic and a straight line indicating an estimated current value calculated from the current current and voltage values.

[0063] In Figure 5, the black dots indicate the current (calculation time) voltage V n and current I n 5 shows a plot of the current limiting characteristic and the line showing the estimated current value. The thin solid line in Fig. 5 shows a straight line showing the estimated current value. In Fig. 5, the white dots indicate the plot of the intersection between the current limiting characteristic and the line showing the estimated current value.

[0064] The estimated current value of the battery 30 can be obtained by an equivalent circuit model of the battery 30. The battery 30 can be a simplified equivalent circuit model that includes, for example, a constant voltage source connected in series between the positive and negative terminals, and a DC resistor for simulating an ohmic resistance component (DC resistance component).

[0065] The constant voltage source is a voltage source that outputs a DC voltage. The voltage output by the constant voltage source is the open circuit voltage (OCV) of the battery 30. The OCV is given as a function of the SOC, for example. The DC resistor is for simulating the DC resistance component (DC impedance) of the battery 30, and has an internal resistance (resistance element) R i Includes internal resistance R i is given as a value that varies depending on the current, voltage, SOC, temperature, etc.

[0066] The equivalent circuit model is the current (calculation point n) terminal voltage V n , current I n , internal resistance R i , and the open circuit voltage OCV, it can be expressed by the following equation (1).

[0067]

number

[0068] By transforming equation (1), we obtain the following equation (2).

[0069]

number

[0070] As shown in equation (2), the voltage V of the battery 30 n and current I n The function formula is 1 / R i In other words, as shown by the thin solid line in Figure 5, , the voltage of battery 30 V n and current I n is (V n ,I n ) with a slope of 1 / R i The magnitude of the change varies along a straight line having the following relationship:

[0071] The current limit value I, which takes into account the changes in the voltage and current of the battery 30, is calculated by calculating the intersection between the line indicating the estimated current value estimated by the equivalent circuit model, which is indicated by the white dot ◯ in FIG. 5, and the current limit characteristic. limit is obtained.

[0072] The current limit value I is the intersection point between the line showing the estimated current value and the current limit characteristic. limit and the said Flow Limit Value I limit The voltage value V' corresponding to n are calculated using the following equations (3) and (4), respectively. can be.

[0073]

number

[0074]

number

[0075] In equations (3) and (4), the maximum current I max , maximum voltage V shift , maximum charging voltage V c are respectively: This is a fixed value that is set in advance for each battery 30. i is the temperature and SOC of the battery 30 The control unit 41 stores the internal resistance R i Remember the following: The internal resistance R of the battery 30, which corresponds to the temperature and state of charge of the battery 30 i Read out the internal resistance R i The two-dimensional table data is generated based on the actual measurement data of a battery test, for example. i teeth, For example, it may be a fixed value such as the maximum value of the internal resistance of the battery 30.

[0076] The internal resistance R i may be a parameter that depends only on temperature. i may be calculated by sequential calculation using an equivalent circuit model.

[0077] The open circuit voltage OCV is calculated by the following formula (5).

[0078]

number

[0079] In equation (5), the voltage V n and current I n may use measurement data obtained by the voltage detection circuit 43 and the current measurement resistor 52, respectively.

[0080] The calculated current limit value I limit is the maximum current I max If it is greater than the current limit value I limit Maximum current I max and the voltage value V'n is calculated using the following formula (6) instead of the above formula (4).

[0081]

number

[0082] From the above, the measurement data of the current voltage, current, temperature, etc. of the battery 30, the internal resistance R i ,maximum current I max , maximum voltage V shift , maximum charging voltage V c Using the current limiting characteristic, Flow Limit Value I limit and voltage value V' n can be calculated.

[0083] For comparison, a case where the current limit value is calculated using a preset coefficient α will be described. Figures 6 and 7 are diagrams for explaining a case where the current limit value is calculated using the preset coefficient α. Figure 6 shows a case where the preset coefficient α is set to a relatively small value. The voltage V of the battery 30 at the current time point n is n and current I n (Black dots in Fig. 6) n The value obtained by adding a predetermined coefficient α to Current Limit limit As shown in Figure 6, the current I n When the current value is increased by a predetermined coefficient α from the n+1 point (the dotted circle in FIG. 6), the voltage value also increases with the increase in the current value. n+1 and current I n+1 shifts in the direction of increasing voltage (white dot in Fig. 6). Here, the current I n+1 is the current limit value limit Since the given coefficient α is relatively small, the voltage V n+1 and current I n+1 is a value far from the current limiting characteristic. In order to approach the current limiting characteristic, it is necessary to repeatedly increase the current limiting value in stages.

[0084] FIG. 7 shows a case where the predetermined coefficient α is set to a relatively large value. As shown in FIG. 7, the current I n When the current value is increased by a predetermined coefficient α from the n+1 point, if the predetermined coefficient α is a relatively large value, the voltage V n+1 and current I n+1 However, the voltage V n+1 and current I n+1 However, there is a risk of exceeding the current limiting characteristics. When the charging current is limited using the predetermined coefficient α, if the predetermined coefficient α is small, the maximum power of the battery 30 cannot be instantaneously received, whereas if the predetermined coefficient α is large, the risk of overshooting increases, making it difficult to make appropriate adjustments.

[0085] According to the method of the present embodiment, the current voltage V n and current I n By predicting the changes in the current value and voltage value when the current limiting value is applied based on this, and then specifying the target value, it is possible to suitably calculate the target value in accordance with the current limiting characteristics.

[0086] 8 is a flowchart showing an example of a calculation process for a current limit value. The control unit 41 of the BMU 40 executes the following process in accordance with the program 421. The control unit 41 may repeatedly execute the following process at predetermined or appropriate time intervals, for example.

[0087] The control unit 41 of the BMU 40 detects the current value I of the battery 30 (at the time of estimation) through the voltage detection circuit 43, the current measurement resistor 52, and the temperature sensor 53. n , voltage value V n and temperature (step S11). When the BMU 40 is installed in a remote location, the control unit 41 receives the measurement data of the battery 30 by communication via the communication unit 45. The control unit 41 functions as an acquisition unit that acquires the measurement data including the current value, voltage value, and temperature.

[0088] The control unit 41 detects the internal resistance R i (Step S12). The control unit 41 Then, referring to an internal resistance table stored in advance in the control data 422 of the storage unit 42, the internal resistance R according to the acquired temperature and SOC of the battery 30 is calculated. i Identify the internal resistance R i By reading out the internal resistance R i The SOC of the battery 30 may be obtained, for example, by calculating the total SOC of the battery 30. Alternatively, the control unit 41 may calculate the internal resistance R corresponding only to the temperature of the battery 30 by a current integration method based on the history of measurement data. i The control unit 41 may specify the equivalent circuit model. The internal resistance R i The control unit 41 may calculate the current limit value. Internal resistance R i The internal resistance R i may be used continuously.

[0089] The control unit 41 reads out the current limiting characteristic pre-stored in the control data 422 of the storage unit 42 (step S13).

[0090] The control unit 41 determines the current value I n , voltage value V n , internal resistance R i Based on the current limiting characteristics, Flow Limit Value I limit (Step S14). Specifically, the control unit 41 calculates the current value I n , voltage value V n , and internal resistance R i The control unit 41 substitutes the current limit value I into the above-mentioned equations (3) to (5) and performs arithmetic processing of each equation to calculate an intersection point between a straight line indicating an estimated current value estimated by the equivalent circuit model and the current limit characteristic. limit and voltage value V' n Calculate The control unit 41 functions as a calculation unit that calculates the current limit value.

[0091] In step S14, the control unit 41 calculates the current limit value I limitis the maximum current I max If it is greater than the current limit value I limit Maximum current I max and the voltage value V' n is calculated using the above formula (6).

[0092] The control unit 41 calculates the current limit value I limit to the charging device 20 (step S15 ), and the series of processes ends. limit and voltage value V' n Charge It may be transmitted to the device 20.

[0093] The charging device 20 is configured to set a current limit value I limit The charging device 20 receives the current limit. Value I limit The charging current is controlled so as not to exceed the to charge the battery 30.

[0094] In the above-mentioned step S14, the control unit 41 calculates the current limit value I limit and voltage Value V′ n It is preferable to perform a check process to determine whether the current limit value I limit The calculation accuracy of the current limit value I limit and voltage value V' n Alternatively, the control unit 41 may calculate the current limit value I limit of This can reduce the calculation load on the control unit 41.

[0095] In the above, the voltage behavior of the battery 30 is simulated by an equivalent circuit model including a DC resistor for simulating an ohmic resistance component. Alternatively, the battery 30 may be represented as an equivalent circuit model including an RC parallel circuit for simulating a non-ohmic resistance (transient polarization characteristic) in addition to a DC resistor for simulating an ohmic resistance component. The RC parallel circuit may be either one stage or multiple stages. By using an internal resistance including an ohmic resistance and a non-ohmic resistance, the estimation accuracy of the estimated current value can be improved.

[0096] According to this embodiment, the charging of the battery 30 can be controlled by a current limit value on the current limit characteristic. The battery 30 can be instantly charged using the maximum current value allowed for the battery 30, and the charging characteristics of the battery 30 can be improved.

[0097] Second embodiment In the second embodiment, the internal resistance R i The following mainly describes the above differences. Other configurations are the same as those in the first embodiment, so the same reference numerals are used for the common configurations and detailed description thereof will be omitted.

[0098] 9 is a diagram illustrating the concept of a method for calculating the current limit value in the second embodiment. For example, the internal resistance R i However, this differs from the internal resistance of the actual battery 30. This sets the current limit value I limit The actual current and voltage values ​​when current flows are in line with the current limiting characteristics. The predicted voltage value V' n In addition, for example, when it takes time for the current limit value output by the BMU 40 to be applied due to the length of the communication interval between the BMU 40 and the charging device 20, the charging control speed in the charging device 20, etc., it is predicted that the actual current value and voltage value will not match the current limit characteristic. Taking into account the deviation of the internal resistance and the response delay, the current limit value I limit By making it smaller or larger than the basic value Therefore, the actual current and voltage values ​​can be made to approximate the current limiting characteristics.

[0099] As explained in the first embodiment, the current limit value I limit is estimated by the equivalent circuit model. The line showing the estimated current value can be calculated as the intersection point of the current limit characteristic and the line showing the estimated current value. The line showing the estimated current value has a slope of 1 / R i It has an internal resistance R i By multiplying by the correction coefficient k, the single-point chain in Fig. 9 is obtained. As shown by the line or the two-dot chain line, the slope of the straight line showing the estimated current value is calculated by dividing the internal resistance R i Do not correct The current limit value I limit , the internal resistance R i can be made smaller or larger than when not corrected. The control unit 41 of the BMU 40 obtains a correction coefficient k according to the state of the battery 30 in advance, and stores the correction coefficient k in the control data 422 of the storage unit 42. The correction coefficient k is set to an appropriate value based on the degree of increase or decrease in the current limit value for the battery 30 according to, for example, a deviation in internal resistance or a response delay.

[0100] 10 is a flowchart showing an example of a calculation process of a current limit value in the second embodiment. The control unit 41 of the BMU 40 acquires current measurement data of the battery 30 (step S21). The control unit 41 calculates the internal resistance R i Get The control unit 41 reads out the current limiting characteristic (step S23). The processes of steps S21 to S23 are similar to those of steps S11 to S13 shown in FIG.

[0101] The control unit 41 reads out the correction coefficient k from the control data 422 of the storage unit 42 to obtain the correction coefficient k (step S24). The control unit 41 calculates the current limit value (step S25). limit and voltage value V' n In calculating The internal resistance R determined based on the internal resistance table i Using the value multiplied by the correction coefficient k, The control unit 41 calculates the current limit value I limit and voltage value V' n The control unit 41 can calculate the internal resistance R i Add or subtract the correction coefficient k to And the internal resistance R i may be corrected.

[0102] The control unit 41 calculates the current limit value I limit to the charging device 20 (step S26 ), and the series of processes is terminated.

[0103] According to this embodiment, the internal resistance R i By correcting the current Limit I limit The speed of raising or lowering the internal resistance R i This allows for suitable control of charging by taking into account changes in the charging speed and response delays of the charging device 20.

[0104] Third embodiment In the third embodiment, the internal resistance R i Change the correction coefficient of The following mainly describes the above-mentioned differences. Since the other configurations are similar to those of the first and second embodiments, the same reference numerals are used for the common configurations and detailed description thereof will be omitted.

[0105] 11 is a diagram illustrating the concept of a method for calculating the current limit value in the third embodiment. i When correcting by the correction coefficient k, the current value and voltage value of the battery 30 are It is preferable to vary the correction factor k.

[0106] As shown in FIG. 11, for example, in the case of a current a where the current value and voltage value of the battery 30 are below the current limit characteristic (the current value and voltage value of the battery 30 are smaller than the limit current value and voltage value of the current limit characteristic), the current limit value I limit Calculate The correction coefficient ka is selected so as to reduce the slope of the straight line showing the estimated current value. In the case of the current b where the current value and voltage value of the battery 30 are above the current limit characteristic (the current value and voltage value of the battery 30 are greater than the limit current value and voltage value of the current limit characteristic), the current limit value I is selected so as to quickly approach the target value. limit The slope of the line showing the estimated current value is increased. In the case of the current c where the current and voltage values ​​of the battery 30 are above the current limiting characteristics and the voltage value is equal to or higher than the maximum charging voltage Vc, the battery 30 is set to the target value earlier. The current limit value I limit The slope of the line showing the estimated current value is calculated as As an example, when the internal resistance of the battery 30 when it is new is used as a reference, the correction coefficient ka for the current battery a may be 1.5, the correction coefficient kb for the current battery b may be 1.0, and the correction coefficient kc for the current battery c may be 0.5.

[0107] The control unit 41 of the BMU 40 acquires in advance a correction coefficient table in which the states of the current value and voltage value of the battery 30 correspond to a correction coefficient k that indicates the rate of increasing or decreasing the current limit value, and stores the correction coefficient table in the control data 422 of the storage unit 42. The correction coefficient k may be set to a plurality of values ​​according to the states of the current value and voltage value of the battery 30, for example, when the current value and voltage value of the battery 30 are above the current limit characteristic, when the current value and voltage value of the battery 30 are below the current limit characteristic, etc. Alternatively, the correction coefficient k may be set to a plurality of values ​​according to the current value of the battery 30, for example.

[0108] The control unit 41 determines the current limit value I limit and voltage value V' n When calculating the internal resistance table The internal resistance Ri The calculation is performed using a value obtained by multiplying this by a correction coefficient k. In this case, the control unit 41 refers to the correction coefficient table and obtains the correction coefficient k according to the current current value and voltage value of the battery 30. Specifically, the control unit 41 compares the current current value and voltage value of the battery 30 with the current limiting characteristic to determine which is larger, and selects the correction coefficient k according to the comparison result. The control unit 41 may obtain the correction coefficient k according to the current current value of the battery 30.

[0109] According to this embodiment, the current limit value I limit The speed at which the current limit is increased or decreased can be adjusted. By taking into account the state of the current value or the current value and voltage value of the battery 30 relative to the charging characteristics, charging can be controlled more appropriately.

[0110] In the above embodiment, the power storage device 10 including the management device 40 is applied to a solar power generation system. The management device, the management method, and the program may be applied to other facilities and vehicles (e.g., automobiles, motorcycles, railroad cars, industrial vehicles, etc.), industrial equipment (e.g., aviation, space, marine, harbor, etc.), power supply equipment, etc.

[0111] In the above embodiment, the power storage device 10 is configured such that one assembled battery 31 is managed by a management device 40. Alternatively, the power storage device 10 may include a bank in which a plurality of assembled batteries (modules) in which a plurality of batteries are connected in series are connected in series, and a management device that manages the bank. The management device may be a simple management device (cell monitoring unit: CMU) that acquires measurement data and transmits the data to a higher-level control device.

[0112] The embodiments disclosed herein are illustrative in all respects and should not be considered as limiting. The technical features described in each embodiment can be combined with each other, and the scope of the present invention is intended to include all modifications within the scope of the claims and the scope equivalent to the claims. [Explanation of symbols]

[0113] 10. Energy storage device 20 Charging device 30 Energy storage element (battery) 31 Battery pack 40 Management unit (BMU) 41 Control section 42 Storage section 43 Voltage detection circuit 44 Input / output section 45 Communications Department 421 Program 422 Control Data 42A Recording media

Claims

1. An acquisition unit that acquires a current value and a voltage value of the storage element; a calculation unit that calculates a current limit value according to a current limit characteristic of the storage element based on an internal resistance of the storage element and the acquired current value and voltage value; A management device comprising:

2. the current limiting characteristic includes a first region and a second region in which the current limiting value decreases in response to an increase in a voltage value of the storage element, The calculation unit calculates the current limiting value along the second region of the current limiting characteristic. The management device according to claim 1 .

3. The calculation unit calculates, as the current limit value, a value at which an estimated current value estimated based on the current value, the voltage value, and the internal resistance using an equivalent circuit model of the storage element intersects with the current limit characteristic. The management device according to claim 1 or 2.

4. The calculation unit calculates the current limit value based on the internal resistance corresponding to at least one of a state of charge and a temperature of the power storage element. The management device according to any one of claims 1 to 3.

5. The calculation unit calculates the current limit value based on the internal resistance corrected using a correction coefficient. The management device according to any one of claims 1 to 4.

6. The correction coefficient is changed according to the current value. The management device according to claim 5 .

7. The correction coefficient is changed based on a comparison result between the acquired current value and voltage value of the storage element and the current limiting characteristic of the storage element. The management device according to claim 5 .

8. A storage element; The management device according to any one of claims 1 to 7. Energy storage device.

9. Acquire the current value and voltage value of the storage element, Calculating a current limit value according to the current limiting characteristics of the storage element based on the internal resistance of the storage element and the acquired current value and voltage value. A method of managing how a process is carried out by a computer.

10. Acquire the current value and voltage value of the storage element, Calculating a current limit value according to the current limiting characteristics of the storage element based on the internal resistance of the storage element and the acquired current value and voltage value. A program that causes a computer to execute a process.

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