Battery monitoring device and battery monitoring system

Abstract

To enable the internal state of a battery to be estimated without complicating a structure.SOLUTION: A battery pack 3C is composed of a plurality of battery cells CbA- CbD that are connected in series and supplies electric power to a load 4 that fluctuates in accordance with operation. A battery monitoring device 5 comprises: an information generation unit 13 for generating frequency information indicating a measurement frequency that corresponds to the fluctuating frequency of the load 4; voltage measurement units 14A-14D for measuring an AC voltage value of the measurement frequency of the plurality of battery cells CbA-CbD on the basis of the frequency information generated by the information generation unit 13; and a processing unit 15 for executing various types of processing for detecting the state of the plurality of battery cells CbA-CbD by using the AC voltage values measured by the voltage measurement units 14A-14D as measurement values. The processing unit 15 executes abnormality detection provided for detecting the abnormality state of the plurality of battery cells CbA-CbD on the basis of relative variation of the plurality of measurement values respectively corresponding to the plurality of battery cells CbA-CbD.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a battery monitoring system that includes a plurality of battery monitoring devices that monitor each of a plurality of battery packs connected in series, and an electronic control device that communicates between the plurality of battery monitoring devices, and a battery monitoring device used in the battery monitoring system. [Background technology]

[0002] In recent years, the spread of battery-powered automobiles has led to an increased demand for battery monitoring systems to safely use secondary batteries. Battery monitoring systems are sometimes called Battery Management Systems, or BMS for short. Battery monitoring systems can estimate the internal state of a battery, such as the degree of battery deterioration and the internal temperature of the battery, and abnormalities in the battery state due to internal short circuits, by measuring the AC impedance of the battery.

[0003] Patent Document 1 discloses a battery monitoring device used in a battery monitoring system. The battery monitoring device disclosed in Patent Document 1 includes a current excitation unit that passes a current through the battery under measurement and a current measurement unit that measures the battery current, and includes voltage measurement units that measure the response voltage from the battery in the same number as the number of battery cells, and performs impedance measurement using the current and voltage values ​​obtained from the current and voltage measurement units. Hereinafter, the battery monitoring device disclosed in Patent Document 1 may be referred to as a conventional battery monitoring device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2020 / 003841 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventional battery monitoring devices have problems such as the need for a current excitation unit and a current measurement unit, and the need to improve the accuracy of time synchronization in the current measurement unit and voltage measurement unit in order to improve the accuracy of estimating the internal state of the battery. In particular, a synchronization circuit is required for time synchronization, which raises concerns about problems such as a complex configuration and increased costs.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and its object is to provide a battery monitoring device and a battery monitoring system that can estimate the internal state of a battery without complicating the configuration. [Means for solving the problem]

[0007] The battery monitoring device described in claim 1 is a battery monitoring device used in a battery monitoring system (1, 71) including a plurality of battery monitoring devices (5, 5A, 5B, 5C, 51, 61, 72, 81) that monitors a plurality of assembled batteries (3, 3A, 3B, 3C) connected in series, and an electronic control device (6) that communicates with the plurality of battery monitoring devices. The assembled battery is configured with a plurality of battery cells (Cb, CbA, CbB, CbC, CbD) connected in series, and supplies power to a load (4) that varies depending on the operation. The battery monitoring device includes an information generating unit (13) that generates frequency information representing a measurement frequency corresponding to a frequency of the load fluctuation, a voltage measuring unit (14, 14A, 14B, 14C, 14D) that measures AC voltage values ​​of the multiple battery cells at the measurement frequency based on the frequency information generated by the information generating unit, and a processing unit (15, 53, 63, 74, 83) that executes various processes to detect the state of the multiple battery cells using the AC voltage values ​​measured by the voltage measuring unit as measurement values.

[0008] The processing unit executes an abnormality detection process to detect an abnormal state of the plurality of battery cells based on relative variations in the plurality of measurement values ​​corresponding to each of the plurality of battery cells. A battery monitoring device having such a configuration can detect an abnormal state of a battery cell without requiring a current excitation unit and a current measurement unit as in a conventional battery monitoring device. Therefore, the above configuration makes it possible to estimate the internal state of the battery without complicating the configuration. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating a schematic configuration of a battery monitoring system according to a first embodiment. [Diagram 2] FIG. 1 is a diagram showing a schematic configuration of a battery monitoring device according to a first embodiment; [Diagram 3] FIG. 1 is a diagram showing an example of a waveform of an orthogonal reference signal REFI according to the first embodiment; [Figure 4] FIG. 1 is a diagram showing an example of a waveform of an orthogonal reference signal REFQ according to the first embodiment; [Diagram 5] FIG. 10 is a diagram for explaining a method for setting an abnormality determination threshold according to the first embodiment, showing an example of a battery voltage value histogram and measurement values; [Figure 6] FIG. 1 is a diagram showing a first specific configuration example of a voltage measurement unit according to a first embodiment; [Figure 7] FIG. 11 is a diagram showing a second specific configuration example of the voltage measurement unit according to the first embodiment; [Figure 8] FIG. 11 is a diagram showing a third specific configuration example of the voltage measurement unit according to the first embodiment; [Figure 9] FIG. 1 is a schematic diagram showing a configuration of a battery monitoring device according to a comparative example; [Figure 10] FIG. 13 is a diagram showing an example of a time waveform of an output current of a current excitation unit according to a comparative example; [Figure 11] FIG. 13 is a diagram showing an example of a frequency spectrum of an output current of a current excitation unit according to a comparative example; [Figure 12] FIG. 13 is a diagram showing an example of a voltage frequency spectrum in an ideal state of a cell voltage according to a comparative example; [Figure 13]FIG. 13 is a diagram showing an example of a voltage frequency spectrum in an ideal state of the output of a voltage measuring unit according to a comparative example; [Figure 14] FIG. 11 is a diagram showing a schematic configuration of a battery monitoring device according to a second embodiment; [Figure 15] FIG. 11 is a diagram illustrating a configuration of a processing unit according to a second embodiment. [Figure 16] FIG. 13 is a diagram showing an example of a correction table according to the second embodiment; [Figure 17] FIG. 13 is a diagram for explaining an example of correction processing according to the second embodiment; [Figure 18] FIG. 11 is a diagram showing a schematic configuration of a battery monitoring device according to a third embodiment; [Figure 19] FIG. 13 is a diagram for explaining evaluation based on a difference in voltage values ​​according to the third embodiment; [Figure 20] FIG. 11 is a diagram illustrating a schematic configuration of a battery monitoring system according to a fourth embodiment. [Figure 21] FIG. 13 is a diagram showing a schematic configuration of a battery monitoring device according to a fourth embodiment; [Figure 22] FIG. 13 is a diagram illustrating a configuration of a battery monitoring device according to a fifth embodiment. [Diagram 23] FIG. 1 is a schematic diagram showing a configuration of a battery monitoring system according to a modified example; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, a number of embodiments will be described with reference to the drawings. Note that the same reference numerals are used to designate substantially the same components in the respective embodiments, and the description thereof will be omitted. (First embodiment) The first embodiment will be described below with reference to FIGS.

[0011] <Overall composition> As shown in FIG. 1, a battery monitoring system 1 of this embodiment is a system for monitoring a battery pack 2 mounted on a vehicle such as an automobile. The battery pack 2 is configured with a plurality of battery cells Cb connected in series between a pair of DC power lines L1, L2. Therefore, the same current flows through all of the plurality of battery cells Cb. In this embodiment, each battery cell Cb has the same battery specifications and is configured of a secondary battery such as a lithium ion battery. The "battery specifications" here refer to the type of battery, the battery capacity, the battery voltage value, etc. Therefore, the deterioration patterns of each battery cell Cb are similar.

[0012] In FIG. 1 and other drawings, only a portion of the battery cells Cb is shown. Each predetermined number of battery cells Cb are grouped together as one assembled battery 3. In other words, the assembled battery 3 is composed of some of the battery cells Cb. Specifically, each N number of battery cells Cb are grouped together as one assembled battery 3. Here, N is a positive integer of 2 or more. In other words, the assembled battery 3 is configured with N battery cells Cb connected in series. The battery pack 2 is composed of a plurality of assembled batteries 3 connected in series. However, in FIG. 1 and other drawings, only three assembled batteries 3 out of the plurality of assembled batteries 3 are shown, and alphabets are added to the end of the reference numerals to distinguish between the three assembled batteries 3.

[0013] The battery pack 3A is provided in the uppermost stage of the battery pack 2, i.e., on the side with the highest potential. The battery pack 3C is provided in the lowermost stage of the battery pack 2, i.e., on the side with the lowest potential. The battery pack 3B is provided between the battery pack 3A and the battery pack 3C. The components provided in the battery monitoring system 1 corresponding to each of these three battery packs 3A, 3B, and 3C may also be distinguished by adding the same alphabet to the end of the reference numeral. However, when it is not necessary to distinguish between these components, the alphabet at the end will be omitted and they will be referred to collectively.

[0014] A battery pack 2 consisting of a plurality of assembled batteries 3 supplies power to a load 4 via DC power lines L1 and L2. The load 4 is an inverter, a DC / DC converter, or the like mounted on the same vehicle as the battery pack 2. Therefore, the impedance of the load 4 varies according to the operation of the vehicle. The battery cells Cb are electrically connected to each other and to two adjacent assembled batteries 3 by bus bars, which are conductive members not shown. In the above configuration, a common mode voltage is superimposed on the battery cells Cb. This common mode voltage increases in the upper stage of the battery pack 2, i.e., the battery cells Cb connected to the higher potential side, and the maximum value of the common mode voltage is a relatively high voltage of, for example, several hundred volts.

[0015] The battery monitoring system 1 includes a plurality of battery monitoring devices 5 that monitor the plurality of assembled batteries 3, respectively, and a battery monitoring ECU 6 that communicates with the plurality of battery monitoring devices 5. However, in FIG. 1 and other figures, only three of the plurality of battery monitoring devices 5 are shown: a battery monitoring device 5A that monitors the assembled battery 3A, a battery monitoring device 5B that monitors the assembled battery 3B, and a battery monitoring device 5C that monitors the assembled battery 3C. The battery monitoring device 5 includes a battery monitoring IC 7, which is an integrated circuit in which circuits that perform various operations for battery monitoring are integrated, and a plurality of external elements and circuits provided outside the battery monitoring IC 7. Note that IC is an abbreviation for Integrated Circuit.

[0016] The battery monitoring IC 7 executes various processes for monitoring the battery pack 3. The various processes executed by the battery monitoring IC 7 include a process for detecting the voltage of the battery cells Cb, a process for communicating with an external device, an abnormality detection process (to be described later), and a cell equalization process for equalizing the voltage of each battery cell Cb.

[0017] The battery monitoring ECU 6 is an electronic control device that controls the overall operation of the battery monitoring system 1, and includes an ECU IC8 configured as an IC, and a plurality of external elements and circuits provided outside the ECU IC8. The ECU IC8 executes various processes for overall control of the battery monitoring system 1. The ECU IC8 of the battery monitoring ECU 6 and each of the battery monitoring ICs 7 of the plurality of battery monitoring devices 5 are connected via a communication line 9.

[0018] The ECU IC8 of the battery monitoring ECU 6 communicates with each of the battery monitoring ICs 7 of the battery monitoring devices 5 according to a predetermined communication protocol. In this case, the connection between the battery monitoring ECU 6 and the battery monitoring devices 5 is a star connection. The ECU IC8 of the battery monitoring ECU 6 transmits data such as each command to the battery monitoring ICs 7 of the battery monitoring devices 5 via communication. The battery monitoring ICs 7 of the battery monitoring devices 5 transmit data such as each measurement result obtained by executing each process to the ECU IC8 of the battery monitoring ECU 6 via communication. In this case, a high common mode voltage superimposed on the battery cell Cb is applied to each battery monitoring device 5. Therefore, the battery monitoring ICs 7 of each battery monitoring device 5 and the ECU IC8 of the battery monitoring ECU 6 are insulated from each other by an insulating unit 10. The insulating unit 10 is provided in each of the battery monitoring devices 5 and the battery monitoring ECU 7, and the insulating method thereof may be, for example, an insulating transformer or a capacitance.

[0019] <Battery monitoring device configuration> The battery monitoring device 5 may be configured as shown in Fig. 2. In this case, the battery monitoring device 5C is used as an example to explain the configuration of the battery monitoring device 5, but the other battery monitoring devices 5 including the battery monitoring devices 5A and 5B may also employ a similar configuration.

[0020] In this case, the battery pack 3C is composed of four battery cells Cb, and alphabets are added to the end of the reference numerals to distinguish between the four battery cells Cb. The components provided in the battery monitoring device 5 corresponding to each of the four battery cells CbA, CbB, CbC, and CbD may also be distinguished by adding the same alphabets to the end of the reference numerals. However, when it is not necessary to distinguish between the components, the alphabets at the end will be omitted and they will be referred to collectively.

[0021] 2, the battery monitoring IC 7 of the battery monitoring device 5C includes a control unit 11 that controls the overall operation of the battery monitoring IC 7, a communication I / F 12 for communicating with an external device, an information generating unit 13, voltage measuring units 14A, 14B, 14C, and 14D, and a processing unit 15. Note that I / F is an abbreviation for interface. The information generating unit 13 generates frequency information that indicates a measurement frequency fLo that corresponds to the frequency of the fluctuation of the load 4.

[0022] The control unit 11 communicates with the battery monitoring ECU 6 via the communication I / F 12, thereby being able to acquire from the battery monitoring ECU 6 the operating frequency of the inverter or DC / DC converter which is the load 4, and in turn the frequency value of the fluctuation of the load 4. The control unit 11 can also acquire the frequency value of the fluctuation of the load 4 based on the measurement results by the voltage measurement units 14A to 14D. The control unit 11 generates a frequency command which commands the value of the measurement frequency fLo based on the frequency value of the fluctuation of the load 4 acquired in this manner, and outputs the frequency command to the information generation unit 13. The information generation unit 13 generates frequency information based on the frequency command given by the control unit 11.

[0023] The frequency information may be various information according to the specific configuration of the voltage measurement unit 14, such as orthogonal reference signals REFI and REFQ, which are sine and cosine waves having the same frequency as the measurement frequency fLo, and data indicating the value of the measurement frequency fLo. Fig. 2 illustrates an example in which the frequency information is orthogonal reference signals REFI and REFQ. Specifically, the orthogonal reference signals REFI and REFQ are signals having waveforms as shown in Figs. 3 and 4.

[0024] The voltage measurement unit 14A is provided corresponding to the battery cell CbA and measures the voltage value of the battery cell CbA. The voltage measurement unit 14A receives the voltage VASP of the high potential terminal of the battery cell CbA, the voltage VASN of the low potential terminal of the battery cell CbA, and the orthogonal reference signals REFI and REFQ, which are frequency information generated by the information generation unit 13. Based on the voltages VASP and VASN and the frequency information, the voltage measurement unit 14A measures the voltage change of the battery cell CbA caused by the fluctuation of the load 4, that is, the AC voltage value of the measurement frequency fLo of the battery cell CbA.

[0025] The voltage measurement unit 14B is provided corresponding to the battery cell CbB and measures the voltage value of the battery cell CbB. The voltage measurement unit 14B receives the voltage VBSP of the high potential terminal of the battery cell CbB, the voltage VBSN of the low potential terminal of the battery cell CbB, and the orthogonal reference signals REFI and REFQ, which are frequency information generated by the information generation unit 13. Based on the voltages VBSP and VBSN and the frequency information, the voltage measurement unit 14B measures the voltage change of the battery cell CbB caused by the fluctuation of the load 4, that is, the AC voltage value of the measurement frequency fLo of the battery cell CbB.

[0026] The voltage measurement unit 14C is provided corresponding to the battery cell CbC and measures the voltage value of the battery cell CbC. The voltage measurement unit 14C receives the voltage VCSP of the high potential terminal of the battery cell CbC, the voltage VCSN of the low potential terminal of the battery cell CbC, and the orthogonal reference signals REFI and REFQ, which are frequency information generated by the information generation unit 13. Based on the voltages VCSP and VCSN and the frequency information, the voltage measurement unit 14C measures the voltage change of the battery cell CbC caused by the fluctuation of the load 4, that is, the AC voltage value of the measurement frequency fLo of the battery cell CbC.

[0027] The voltage measurement unit 14D is provided corresponding to the battery cell CbD and measures the voltage value of the battery cell CbD. The voltage measurement unit 14D receives the voltage VDSP of the high potential terminal of the battery cell CbD, the voltage VDSN of the low potential terminal of the battery cell CbD, and the orthogonal reference signals REFI and REFQ, which are frequency information generated by the information generation unit 13. Based on the voltages VDSP and VDSN and the frequency information, the voltage measurement unit 14D measures the voltage change of the battery cell CbD caused by the fluctuation of the load 4, that is, the AC voltage value of the measurement frequency fLo of the battery cell CbD.

[0028] The voltage measuring units 14A to 14D output measurement result information indicating the measurement results of the AC voltage values ​​to the processing unit 15. The measurement result information is various information according to the specific configuration of the voltage measuring unit 14, such as signals indicating the in-phase and quadrature components of the AC voltage having the same frequency as the orthogonal reference signals REFI and REFQ, and a signal indicating the AC voltage amplitude component of the measurement frequency fLo. Fig. 2 illustrates an example in which the measurement result information is signals VABI, VBBI, VCBI, and VDBI indicating the in-phase components of the AC voltage and signals VABQ, VBBQ, VCBQ, and VDBQ indicating the quadrature components.

[0029] The processing unit 15 executes various processes for detecting the states of the battery cells CbA-CbD using the AC voltage values ​​measured by the voltage measuring units 14A-14D as measured values. In this case, the processing unit 15 executes an abnormality detection process for detecting an abnormal state of the battery cells CbA-CbD based on the relative variations in the measured values ​​corresponding to each of the battery cells CbA-CbD.

[0030] The abnormality detection process of this embodiment is performed based on the following concept. That is, variations in the measured values ​​occur due to manufacturing variations in each battery cell Cb and measurement variations by the voltage measurement unit 14. Therefore, the processing unit 15 can determine that a battery cell Cb corresponding to a measured value that shows a greater than expected deviation in voltage value compared to the average voltage value of each battery cell Cb in the assembled battery 3 is an abnormal cell.

[0031] In the abnormality detection process, the processing unit 15 processes a plurality of measurement values ​​corresponding to each of the battery cells CbA to CbD in an integrated manner, that is, performs statistical processing on the plurality of measurement values. In order to perform such processing, it is necessary to determine an abnormality determination threshold, which is a threshold for determining an abnormality, in advance. The abnormality determination threshold can be calculated in advance based on the average voltage value of each of the battery cells CbA to CbD, the variation value of all the battery cells CbA to CbD, past voltage values, etc. For example, as shown in FIG. 5, the abnormality determination threshold can be set to two values ​​ThL and ThH that occur very rarely.

[0032] In the abnormality detection process, the processing unit 15 determines that the battery cell Cb corresponding to the measurement value outside the range of the abnormality determination thresholds ThL and ThH is an abnormal cell. In the case shown in FIG. 5, the measurement values ​​corresponding to the battery cells CbA, CbB, and CbD are not outside the abnormality determination thresholds, so the battery cells CbA, CbB, and CbD are determined to be normal cells. In the case shown in FIG. 5, the measurement value corresponding to the battery cell CbC is outside the abnormality determination thresholds, so the battery cell CbC is determined to be an abnormal cell. Note that the optimal abnormality determination threshold that can accurately detect an abnormal cell changes every moment depending on the battery state, such as the remaining battery capacity and battery temperature of the battery cell Cb. Therefore, it is desirable for the processing unit 15 to dynamically change the abnormality determination threshold depending on the battery state, such as the charging state and temperature state of the battery cell Cb.

[0033] <Specific Configuration of Voltage Measurement Unit 14> As a specific configuration of the voltage measurement unit 14, for example, a first configuration example employing a frequency lock-in method as shown in Fig. 6, a second configuration example employing an FFT method as shown in Fig. 7, or a third configuration example employing a band-pass filter method as shown in Fig. 8 can be adopted. In this case, a specific configuration example of the voltage measurement unit 14 will be described using the voltage measurement unit 14A as an example, but the other voltage measurement units 14 including the voltage measurement units 14B to 14D can also adopt a similar configuration.

[0034] [1] First configuration example As shown in Fig. 6, the voltage measurement unit 14A in the first configuration example includes subtractors 21, 22, 23, an A / D converter 24, a DC offset correction unit 25, a first filter 26, and a quadrature demodulator 27. In this specification, the A / D converter may be abbreviated as ADC. The subtractor 21 subtracts a signal corresponding to an offset value generated by the DC offset correction unit 25 from the voltage VASP. The subtractor 22 subtracts a signal corresponding to an offset value generated by the DC offset correction unit 25 from the voltage VASN. The ADC 24 inputs the output signals of the subtractors 21 and 22, and outputs a digital signal representing the result of A / D conversion of the input signals.

[0035] DC offset correction unit 25 receives the output signal of ADC 24, generates a signal corresponding to an offset value according to the input signal, and outputs the signal to each of subtractors 21 to 23. Subtractor 23 subtracts the signal corresponding to the offset value generated by DC offset correction unit 25 from the output signal of ADC 24. First filter 26 receives the output signal of subtractor 23, performs a predetermined filtering process, and outputs the filtered signal to quadrature demodulator 27.

[0036] The quadrature demodulator 27 includes mixers 28 and 29, and second filters 30 and 31. The output signal of the first filter 26 and the orthogonal reference signal REFI are input to the mixer 28. The output signal of the mixer 28, that is, the signal obtained by multiplying the output signal of the first filter 26 and the orthogonal reference signal REFI, is input to the second filter 30. The output signal of the first filter 26 and the orthogonal reference signal REFQ are input to the mixer 29. The output signal of the mixer 29, that is, the signal obtained by multiplying the output signal of the first filter 26 and the orthogonal reference signal REFQ, is input to the second filter 31.

[0037] The second filter 30 performs a predetermined filtering process on the input signal and outputs the filtered signal as a signal VABI. The second filter 31 performs a predetermined filtering process on the input signal and outputs the filtered signal as a signal VABQ. According to the voltage measurement unit 14A of the first configuration example, the signal VABI representing the in-phase component of the AC voltage and the signal VABQ representing the quadrature component, which have the same frequency as the quadrature reference signals REFI and REFQ, can be output as measurement result information. When the first configuration example is adopted as the voltage measurement unit 14, the processing unit 15 can use the in-phase component, quadrature component, voltage amplitude, voltage phase, etc. of the AC voltage based on the output signal of the voltage measurement unit 14 in the abnormality detection process.

[0038] [2] Second configuration example 7, the voltage measurement unit 14A in the second configuration example is different from the voltage measurement unit 14A in the first configuration example in that it includes an FFT unit 32 instead of the orthogonal demodulator 27. FFT is an abbreviation for Fast Fourier Transform. The output signal of the first filter 26 and the orthogonal reference signal REFI are input to the FFT unit 32.

[0039] The FFT unit 32 performs discrete Fourier transform processing on the output signal of the first filter 26, and can output a signal VABI representing the in-phase component of a frequency bin specified by the orthogonal reference signal REFI and a signal VABQ representing the orthogonal component as measurement result information. When the second configuration example is adopted as the voltage measurement unit 14, the processing unit 15 can use the in-phase component, orthogonal component, voltage amplitude, voltage phase, and the like of the AC voltage based on the output signal of the voltage measurement unit 14 in the abnormality detection processing.

[0040] [3] Third configuration example 8, the voltage measurement unit 14A in the third configuration example is different from the voltage measurement unit 14A in the first configuration example in that it includes a band pass filter 33, a rectifier circuit 34, and a smoothing circuit 35 instead of the first filter 26 and the quadrature demodulator 27. In this specification, the band pass filter may be referred to as a BPF. The output signal of the subtractor 23 is input to the BPF 33.

[0041] The BPF 33 passes only a specific frequency component of the input signal. The BPF 33 is configured to be able to set the specific frequency to be passed based on data representing the value of the measurement frequency fLo, which is frequency information provided by the information generating unit 13. The rectifier circuit 34 receives the output signal of the BPF 33, rectifies the signal, and outputs the signal. The smoothing circuit 35 receives the output signal of the rectifier circuit 34, smoothes the signal, and outputs the signal. The output signal of the smoothing circuit 35 is a signal corresponding to the amplitude component of the AC voltage. Therefore, in this case, the output signal of the smoothing circuit 35 becomes the signal V representing the measurement result information.

[0042] According to the present embodiment described above, the following effects can be obtained. The battery monitoring device 5 of this embodiment includes an information generating unit 13 that generates frequency information representing a measurement frequency fLo corresponding to the frequency of fluctuation of the load 4, a voltage measuring unit 14 that measures the AC voltage values ​​of the measurement frequency of the multiple battery cells Cb based on the frequency information generated by the information generating unit 13, and a processing unit 15 that executes various processes to detect the state of the multiple battery cells Cb using the AC voltage values ​​measured by the voltage measuring unit 14 as measurement values.

[0043] The processing unit 15 executes an abnormality detection process to detect an abnormal state of the multiple battery cells Cb based on the relative variations in the multiple measured values ​​corresponding to each of the multiple battery cells Cb. The battery monitoring device 5 configured in this manner can detect an abnormal state of the battery cells Cb without requiring a current excitation unit and a current measurement unit as in conventional battery monitoring devices. Therefore, according to this embodiment, it is possible to estimate the internal state of the battery without complicating the configuration.

[0044] The effects obtained by this embodiment become clearer when compared with a conventional battery monitoring device. Therefore, a comparative example equivalent to the conventional battery monitoring device will be described and then the comparative example will be compared with this embodiment. As shown in Fig. 9, a battery monitoring device 41 of the comparative example differs from the battery monitoring device 5C of this embodiment shown in Fig. 2 in that it includes a battery monitoring IC 42 instead of the battery monitoring IC 7 and that a current generating unit 43 is added.

[0045] The battery monitoring IC 42 is configured to be able to measure battery impedance based on the AC impedance method. The battery monitoring IC 42 differs from the battery monitoring IC 7 in that an excitation signal processing unit 44 and a current measuring unit 45 are added, and a measuring unit 46 is provided instead of the processing unit 15. In this case, the excitation signal processing unit 44 constitutes a current excitation unit 47 together with a current generating unit 43 provided outside the battery monitoring IC 42.

[0046] The excitation signal processing unit 44 receives the orthogonal reference signal REFI generated by the information generating unit 13. The excitation signal processing unit 44 performs signal processing such as amplification, level conversion, and application of a DC offset signal on the input signal and outputs the result. The current generating unit 43 receives the output signal of the excitation signal processing unit 44 and generates an excitation current to be applied to the battery cells CbA to CbD based on the signal. At this time, the voltage of the high potential side terminal of the battery cell CbD becomes the voltage V1FP, and the voltage of the low potential side terminal of the battery cell CbA becomes the voltage V1FN.

[0047] In this case, the specific configuration of the voltage measurement unit 14 is assumed to be the same as that of the first configuration example shown in Fig. 6. The voltage measurement units 14A to 14D output signals VABI, VBBI, VCBI, and VDBI representing the in-phase components of the AC voltage and signals VABQ, VBBQ, VCBQ, and VDBQ representing the quadrature components to the measurement unit 46. In the following description, the signals VABI, VBBI, VCBI, and VDBI may be collectively referred to as signal VxBI, and the signals VABQ, VBBQ, VCBQ, and VDBQ may be collectively referred to as signal VxBQ.

[0048] The current measurement unit 45 receives signals I1FN and I1FP for measuring the current generated by the current generation unit 43, and orthogonal reference signals REFI and REFQ generated by the information generation unit 13. The current measurement unit 45 has a similar configuration to the voltage measurement unit 14. The current measurement unit 45 outputs a signal I1BI representing an in-phase component of the AC current and a signal I1BQ representing an orthogonal component to the measurement unit 46. The measurement unit 46 executes various processes for measuring the impedance of the battery cell Cb based on the output signal of the voltage measurement unit 14 and the output signal of the current measurement unit 45.

[0049] In the above configuration, when the information generating unit 13 generates the orthogonal reference signals REFI and REFQ during impedance measurement, an excitation current to be applied to the battery cells CbA to CbD is generated by the operation of the current exciting unit 47. The excitation current generated by the current exciting unit 47 includes a DC offset signal as shown in Fig. 10, and also includes an excitation AC current signal of the measurement frequency fLo as shown in Fig. 11.

[0050] The excitation current is applied to the battery pack 3 and is converted into a voltage by the impedance of the battery cells CbA to CbD. Therefore, the frequency spectrum of the voltage generated across each of the battery cells CbA to CbD generates a DC component and a signal at the measurement frequency fLo, as shown in Fig. 12, where the DC component is the sum of the voltage of the battery cell Cb and the product of the impedance of the battery cell Cb and the DC offset signal of the excitation current, and an excitation AC voltage is generated at the measurement frequency fLo, which is the product of the impedance of the battery cell Cb and the excitation AC current.

[0051] Such excitation voltages are input to voltage measurement units 14A-14D connected to the respective battery cells CbA-CbD, where they are synchronously detected by the orthogonal reference signals REFI and REFQ in the voltage measurement units 14A-14D, and then filtered to detect only the excitation AC voltage, which is the same frequency component as the measurement frequency fLo. The voltage measurement unit 14 supplies to the measurement unit 46 a signal VxBQ representing an in-phase component based on the amplitude and phase of the excitation voltage as shown in FIG. 13 and a signal VxBQ representing a quadrature component.

[0052] The excitation current is input to a current measuring unit 45, where it is synchronously detected by orthogonal reference signals REFI and REFQ, and then filtered to detect only the excitation AC current, which is the same frequency component as the measurement frequency fLo. The current measuring unit 45 supplies a signal I1BI representing an in-phase component and I1BQ representing a quadrature component based on the amplitude and phase of the generated excitation current to a measurement unit 46.

[0053] The measurement unit 46 calculates the real and imaginary parts of the impedance by vector dividing the excitation voltage thus input by the excitation current. The measurement unit 46 reports the calculation results to a higher-level system (not shown) via the control unit 11 and the communication I / F 12. According to the battery impedance measurement using the AC impedance method with the configuration of the comparative example, signal detection is performed only for frequency components equal to the measurement frequency fLo, so that the noise removal capability is high and measurements with a good SNR (signal-to-noise ratio) are possible.

[0054] However, the battery monitoring device 41 of the comparative example requires the current excitation unit 47 and the current measurement unit 45, which causes problems of a more complicated configuration and increased manufacturing costs. In addition, in the battery monitoring device 41 of the comparative example, when the current measurement unit 45 and the voltage measurement unit 14 perform measurements using different reference clocks, it is necessary to improve the accuracy of time synchronization in the current measurement unit 45 and the voltage measurement unit 14 in order to improve the accuracy of the impedance measurement and, by extension, the accuracy of the estimation of the internal state of the battery.

[0055] Therefore, the battery monitoring device 41 of the comparative example requires a synchronous circuit, which causes problems of further complicating the configuration and increasing manufacturing costs. In contrast, the battery monitoring device 5 of the present embodiment does not require the current excitation unit 47 and current measurement unit 45 as in the battery monitoring device 41 of the comparative example, and does not require a synchronous circuit. Therefore, according to the present embodiment, it is possible to estimate the internal state of the battery while having a simpler configuration than the comparative example and keeping manufacturing costs low.

[0056] Second embodiment The second embodiment will be described below with reference to FIGS. 14, a battery monitoring IC 52 included in a battery monitoring device 51 of this embodiment is different from the battery monitoring IC 7 of the first embodiment in that it includes a processing unit 53 instead of the processing unit 15. As shown in FIG. 15, the processing unit 53 includes correction tables 54A, 54B, 54C, and 54D, correction processing units 55A, 55B, 55C, and 55D, and an abnormality detection unit 56.

[0057] The measured voltage of the battery cell Cb may vary for each battery cell Cb due to the temperature and wiring of the battery pack 2. In this embodiment, the deviation of the voltage value due to these factors is corrected using a correction table 54. As shown in FIG. 16, the correction table 54 stores correction values ​​corresponding to temperatures and frequencies. The correction processing unit 55 receives the AC voltage values ​​measured by the corresponding voltage measuring units 14 and temperature detection signals indicating the temperatures detected by the temperature sensors (not shown). The temperature sensors are provided so as to be able to detect the temperature at any point of the battery pack 2. The correction processing unit 55 is also configured so as to be able to acquire the value of the current measurement frequency fLo.

[0058] With this configuration, the correction processing unit 55 executes a correction process to correct the AC voltage value measured by the voltage measurement unit 14 using the correction value stored in the correction table 54. As a method of such correction, as shown in FIG. 17, a method of vector calculation of a correction term for a complex voltage value can be mentioned. For example, when the temperature is 0° C. and the measurement frequency fLo is 10 Hz, the AC voltage value before correction is a voltage value V expressed by the formula (1), and the AC voltage value after correction is a voltage value V′ expressed by the formula (2). Note that Im in FIG. 17 and the like represents an imaginary part, and Re represents a real part. The abnormality detection unit 56 executes an abnormality detection process similar to that executed by the processing unit 15 of the first embodiment, using the AC voltage value corrected by the correction process as a measurement value.

[0059] According to the present embodiment described above, it is possible to correct the deviation in the measured voltage for each battery cell Cb caused by the temperature, wiring, etc. of the battery pack 2. Therefore, according to the present embodiment, it is possible to accurately detect an abnormal state of the battery cell Cb without being affected by the temperature, wiring, etc. of the battery pack 2.

[0060] Third embodiment The third embodiment will be described below with reference to FIGS. As shown in Fig. 18, a battery monitoring IC 62 included in a battery monitoring device 61 of this embodiment differs from the battery monitoring IC 7 of the first embodiment in that it includes a processing unit 63 instead of the processing unit 15. The processing unit 63 acquires in advance an initial AC voltage characteristic value corresponding to an AC voltage value in an initial state in which the battery monitoring system 1 is initially operated. As shown in Fig. 19, the processing unit 63 uses the difference between the initial AC voltage characteristic value V0 and the AC voltage value V measured by the voltage measurement unit 14 as a measured value to perform an abnormality detection process similar to that performed by the processing unit 15 of the first embodiment.

[0061] According to the present embodiment described above, the following effects can be obtained. That is, when determining an abnormal state of the battery cell Cb, it is considered that there are cases where it is appropriate to make a judgment by comprehensively looking at the change in the difference, rather than simply integrating the absolute changes. According to the present embodiment, the abnormality detection process is performed using the difference between the initial AC voltage characteristic value V0 and the AC voltage value V as a measured value, and therefore this embodiment is suitable for cases where it is appropriate to make a judgment by comprehensively looking at the change in the difference.

[0062] (Fourth embodiment) The fourth embodiment will be described below with reference to FIGS. As shown in Fig. 20, a battery monitoring system 71 of the present embodiment differs from the battery monitoring system 1 of the first embodiment in that it includes a battery monitoring device 72 instead of the battery monitoring device 5. As shown in Fig. 21, a battery monitoring IC 73 of the battery monitoring device 72 of the present embodiment differs from the battery monitoring IC 7 of the battery monitoring device 5 in that it includes a processing unit 74 instead of the processing unit 15.

[0063] The processing unit 74 executes a transmission process to transmit the AC voltage value measured by the voltage measurement unit 14 as a measured value to the battery monitoring ECU 6. The ECU IC8 of the battery monitoring ECU 6 executes an abnormality detection process to detect an abnormal state of the multiple battery cells Cb based on relative variations in multiple measured values ​​corresponding to each of the multiple battery cells Cb in all of the assembled batteries 3 monitored by the multiple battery monitoring devices 72.

[0064] According to the present embodiment described above, in the abnormality detection process, a plurality of measurement values ​​corresponding to each of all of the battery cells Cb constituting the battery pack 2 are processed in an integrated manner, that is, statistical processing is performed on a plurality of measurement values ​​corresponding to each of all of the battery cells Cb, so that abnormal states of the battery cells Cb can be detected with even greater accuracy.

[0065] Fifth embodiment The fifth embodiment will be described below with reference to FIG. As shown in Fig. 22, the battery monitoring device 81 of this embodiment differs from the battery monitoring device 5 of the first embodiment in that it includes a battery monitoring IC 82 instead of the battery monitoring IC 7, and in that it also includes a current excitation unit 47 similar to the battery monitoring device 41 of the comparative example shown in Fig. 9. The battery monitoring IC 82 differs from the battery monitoring IC 7 in that it also includes an excitation signal processing unit 44 constituting the current excitation unit 47, and in that it also includes a processing unit 83 instead of the processing unit 15. The current excitation unit 47 can generate an AC current having the same frequency as the measurement frequency fLo based on the orthogonal reference signal REFI, which is frequency information generated by the information generating unit 13, and apply the AC current to the battery pack 3.

[0066] In this case, the voltage measurement unit 14 can measure AC voltage values ​​at the measurement frequency fLo of the multiple battery cells Cb during the period in which the AC current generated by the current excitation unit 47 is applied to the battery pack 3. In this case, the processing unit 83 uses the AC voltage values ​​measured by the voltage measurement unit 14 during the period in which the AC current generated by the current excitation unit 47 is applied to the battery pack 3 as measurement values, and executes anomaly detection processing similar to that executed by the processing unit 15 in the first embodiment.

[0067] According to the present embodiment described above, it is possible to estimate the internal state of the battery without complicating the configuration, as in the first embodiment. In this case, a current excitation unit 47 is added to the configuration of the first embodiment, but since the measurement value required for the anomaly detection process is a voltage value, not an impedance value, there is no need to perform high-precision current measurement. Therefore, it is possible to simplify the configuration and reduce the manufacturing cost compared to the comparative example.

[0068] (Other embodiments) The present invention is not limited to the embodiments described above and shown in the drawings, and can be modified, combined, or expanded as desired without departing from the spirit and scope of the present invention. The numerical values ​​and the like shown in the above embodiments are merely examples and are not intended to be limiting. The connection between the battery monitoring ECU 6 and the multiple battery monitoring devices 5 does not have to be limited to a star-type connection, and the connection between the battery monitoring ECU 6 and the multiple battery monitoring devices 5 can also be a daisy-chain type connection, for example, as in a modified battery monitoring system 91 shown in Figure 23.

[0069] Although the present disclosure has been described based on the embodiment, it is understood that the present disclosure is not limited to the embodiment or structure. The present disclosure also includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, and other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and concept of the present disclosure.

[0070] The control unit and the method described in the present disclosure may be realized by a special-purpose computer provided by configuring a processor and a memory programmed to execute one or more functions embodied in a computer program. Alternatively, the control unit and the method described in the present disclosure may be realized by a special-purpose computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the control unit and the method described in the present disclosure may be realized by one or more special-purpose computers configured by a combination of a processor and a memory programmed to execute one or more functions and a processor configured with one or more hardware logic circuits. In addition, the computer program may be stored in a computer-readable non-transitory tangible recording medium as instructions executed by a computer.

[0071] In addition to the inventions described in the claims, the present disclosure includes the following inventions. [1] A battery monitoring device used in a battery monitoring system (1, 71, 91) including a plurality of battery monitoring devices (5, 5A, 5B, 5C, 51, 61, 72, 81) that monitors a plurality of battery packs (3, 3A, 3B, 3C) connected in series, and an electronic control device (6) that communicates with the plurality of battery monitoring devices, The battery pack is configured by connecting a plurality of battery cells (Cb, CbA, CbB, CbC, CbD) in series and supplies power to a load (4) whose power varies depending on the operation of the load (4). an information generating unit (13) that generates frequency information representing a measurement frequency corresponding to a frequency of the load fluctuation; a voltage measurement unit (14, 14A, 14B, 14C, 14D) that measures AC voltage values ​​of the plurality of battery cells at the measurement frequency based on the frequency information generated by the information generation unit; a processing unit (15, 53, 63, 74, 83) that executes various processes for detecting states of the plurality of battery cells by using the AC voltage value measured by the voltage measurement unit as a measurement value; Equipped with The processing unit includes: A battery monitoring device that executes an abnormality detection process to detect an abnormal state of the plurality of battery cells based on a relative variation of the plurality of measurement values ​​corresponding to each of the plurality of battery cells. [2] The processing section (53) A correction process is performed to correct the AC voltage value using a correction table (54, 54A, 54B, 54C, 54D) in which correction values ​​corresponding to temperatures and frequencies are stored; The battery monitoring device according to [1], wherein the abnormality detection process is performed using the AC voltage value corrected by the correction process as the measurement value. [3] The battery monitoring device of claim 1 or 2, wherein the processing unit (63) executes the abnormality detection process by using, as the measurement value, a difference between an initial AC voltage characteristic value corresponding to the AC voltage value in an initial state, which is an initial state when the battery monitoring system is operating, and the AC voltage value measured by the voltage measurement unit. [4] A battery monitoring system including a plurality of battery monitoring devices according to any one of [1] to [3] and an electronic control device that communicates with the plurality of battery monitoring devices, the processing unit (74) of the plurality of battery monitoring devices (72) executes a transmission process of transmitting the AC voltage value measured by the voltage measurement unit to the electronic control device as a measurement value; The electronic control device of the battery monitoring system executes an abnormality detection process to detect an abnormal state of the multiple battery cells based on the relative variation of the multiple measurement values ​​corresponding to each of the multiple battery cells in all of the assembled batteries monitored by the multiple battery monitoring devices. [5] a current excitation unit (47) that generates an AC current having the same frequency as the measurement frequency based on the frequency information generated by the information generation unit and applies the AC current to the battery pack, The battery monitoring device according to any one of claims [1] to [3], wherein the voltage measurement unit measures the AC voltage values ​​of the plurality of battery cells at the measurement frequency during a period in which the AC current generated by the current excitation unit is applied to the battery pack. [Explanation of symbols]

[0072] 1, 71, 91...battery monitoring system, 3, 3A, 3B, 3C...battery pack, 4...load, 5, 5A, 5B, 5C, 51, 61, 72, 81...battery monitoring device, 6...battery monitoring ECU, 13...information generation unit, 14, 14A, 14B, 14C, 14D...voltage measurement unit, 15, 53, 63, 74, 83...processing unit, 47...current excitation unit, 54, 54A, 54B, 54C, 54D...correction table, Cb, CbA, CbB, CbC, CbD...battery cell.

Claims

1. A battery monitoring device used in a battery monitoring system (1, 71, 91) including a plurality of battery monitoring devices (5, 5A, 5B, 5C, 51, 61, 72, 81) that monitors a plurality of battery packs (3, 3A, 3B, 3C) connected in series, and an electronic control device (6) that communicates with the plurality of battery monitoring devices, The battery pack has a configuration in which a plurality of battery cells (Cb, CbA, CbB, CbC, CbD) are connected in series, and supplies power to a load (4) whose power varies depending on the operation of the load (4). An information generating unit (13) that generates frequency information representing a measurement frequency corresponding to a frequency of the load fluctuation; a voltage measurement unit (14, 14A, 14B, 14C, 14D) for measuring AC voltage values ​​of the plurality of battery cells at the measurement frequency based on the frequency information generated by the information generation unit; a processing unit (15, 53, 63, 74, 83) that executes various processes for detecting states of the plurality of battery cells by using the AC voltage value measured by the voltage measurement unit as a measurement value; Equipped with The processing unit includes: A battery monitoring device that executes an abnormality detection process to detect an abnormal state of the plurality of battery cells based on a relative variation of the plurality of measurement values ​​corresponding to each of the plurality of battery cells.

2. The processing section (53) A correction process is performed to correct the AC voltage value using a correction table (54, 54A, 54B, 54C, 54D) in which correction values ​​corresponding to temperatures and frequencies are stored; The battery monitoring device according to claim 1 , wherein the abnormality detection process is performed by using the AC voltage value corrected by the correction process as the measurement value.

3. The battery monitoring device of claim 1 or 2, wherein the processing unit (63) executes the abnormality detection process using, as the measurement value, a difference between an initial AC voltage characteristic value corresponding to the AC voltage value in an initial state, which is an initial state when the battery monitoring system is operating, and the AC voltage value measured by the voltage measurement unit.

4. A battery monitoring system including a plurality of battery monitoring devices according to claim 1 and an electronic control device that communicates with the plurality of battery monitoring devices, The processing unit (74) of the plurality of battery monitoring devices (72) executes a transmission process of transmitting the AC voltage value measured by the voltage measurement unit to the electronic control device as a measurement value, The electronic control device of the battery monitoring system executes an abnormality detection process to detect an abnormal state of the multiple battery cells based on the relative variation of the multiple measurement values ​​corresponding to each of the multiple battery cells in all of the assembled batteries monitored by the multiple battery monitoring devices.

5. a current excitation unit (47) that generates an AC current having the same frequency as the measurement frequency based on the frequency information generated by the information generation unit and applies the AC current to the battery pack; The battery monitoring device according to claim 1 , wherein the voltage measurement unit measures AC voltage values ​​of the plurality of battery cells at the measurement frequency during a period in which the AC current generated by the current excitation unit is applied to the battery pack.

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