Battery measurement device

Abstract

To provide a battery measuring device enabling an error of an impedance to be reduced.SOLUTION: A battery measuring device 50 measuring a state of a battery cell 42, is equipped with: a semiconductor switch element 56a which is provided on a first electric path 81 and causes the battery cell 42 to output an AC signal from; a current measuring amplifier 56c which measures the AC signal flowing in the first electric path; an input / output portion 52 which is provided on a second electric path 82 and measures a response signal of the battery cell 42 to the AC current through the second electric path; and a microcomputer portion 53 which calculates information on a complex impedance on the basis of measurement results of the AC signal and the response signal. The microcomputer portion 53, after the output of the AC signal is started and the measurement results are brought into a stationary state, calculates the information on the complex impedance and outputs a calculation result.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a battery measurement device. [Background technology]

[0002] Conventionally, in order to measure the state of a storage battery, the complex impedance (AC impedance) of the storage battery has been measured (for example, Patent Document 1). In the invention described in Patent Document 1, an AC current such as a sine wave current is passed from an oscillator to the storage battery, and the response signal (voltage fluctuation) and the AC current are measured, and the complex impedance characteristics are calculated based on the measurement results. Then, the deterioration state of the storage battery is determined based on this complex impedance characteristic. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020 / 003841 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the state of the circuit for measuring impedance and the storage battery are not always constant, and the state may change due to the application of AC current. For example, a shunt resistor provided for measuring AC current may generate heat and change its temperature based on the application of AC current. When the temperature of the shunt resistor changes, its resistance value changes, and as a result, the amplitude of the AC current flowing through the storage battery changes. As a result, an error may occur in the measurement result of the AC current, which may cause an error in the impedance.

[0005] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide a battery measurement device that can reduce impedance errors. [Means for solving the problem]

[0006] A battery measuring device for measuring the state of a storage battery as a means for solving the above problems includes a signal control unit for outputting an AC signal from the storage battery or inputting an AC signal to the storage battery, a current measuring unit for measuring the AC signal, a response signal measuring unit for measuring a response signal of the storage battery to the AC signal, and a calculation unit for calculating information related to the complex impedance of the storage battery based on the measurement results of the AC signal measured by the current measuring unit and the response signal measured by the response signal measuring unit, wherein after the signal control unit starts inputting and outputting the AC signal, the calculation unit waits for the measurement result of the AC signal to reach a steady state, and then calculates the information related to the complex impedance and outputs the calculation result.

[0007] Therefore, when calculating information related to the complex impedance, it is possible to reduce the temperature rise caused by the AC signal, suppress errors in the measurement results of the AC signal, and improve the calculation accuracy of the complex impedance. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a power supply system. [Diagram 2] FIG. [Diagram 3] 4 is a flowchart of an impedance calculation process. [Figure 4] 13 is a flowchart of a preparation process. [Diagram 5] 13 is a flowchart of a preparation process according to a second embodiment. [Figure 6] FIG. 13 is a diagram showing the relationship between complex impedance and frequency. [Figure 7] FIG. 13 is a diagram showing the relationship between the phase and current value of the preparatory AC signal at the start. [Figure 8] FIG. 4 is a diagram showing a preparatory AC signal. [Figure 9] 13 is a flowchart of a preparation process according to a third embodiment. [Figure 10] 13 is a flowchart of a preparation process according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (First embodiment) Hereinafter, a first embodiment in which a "battery measurement device" is applied to a power supply system of a vehicle (for example, a hybrid vehicle or an electric vehicle) will be described with reference to the drawings.

[0010] As shown in FIG. 1, the power supply system 10 includes a motor 20 as a rotating electric machine, an inverter 30 as a power converter that supplies a three-phase current to the motor 20, a chargeable and dischargeable battery pack 40, a battery measuring device 50 that measures the state of the battery pack 40, and an ECU 60 that controls the motor 20 and the like.

[0011] The motor 20 is an in-vehicle main engine capable of transmitting power to driving wheels (not shown). In this embodiment, a three-phase permanent magnet synchronous motor is used as the motor 20.

[0012] The inverter 30 is configured with a full-bridge circuit having upper and lower arms in the same number as the number of phases of the phase windings, and the current flowing in each phase winding is adjusted by turning on and off a switch (semiconductor switching element) provided in each arm.

[0013] The inverter 30 is provided with an inverter control device (not shown), which controls current flow by turning on and off each switch in the inverter 30 based on various detection information of the motor 20 and requests for power running and power generation. As a result, the inverter control device supplies power from the battery pack 40 to the motor 20 via the inverter 30, and powers the motor 20. The inverter control device also causes the motor 20 to generate power based on power from the drive wheels, converts the generated power via the inverter 30, and supplies it to the battery pack 40, charging the battery pack 40.

[0014] The battery pack 40 is electrically connected to the motor 20 via the inverter 30. The battery pack 40 has a terminal voltage of, for example, 100 V or more, and is configured by connecting a plurality of battery modules 41 in series. The battery module 41 is configured by connecting a plurality of battery cells 42 in series. For example, a lithium ion battery or a nickel metal hydride battery can be used as the battery cells 42. Each battery cell 42 is a battery having an electrolyte and a plurality of electrodes.

[0015] 1, a positive terminal of an electric load such as an inverter 30 is connected to a positive power supply path L1 connected to a positive power supply terminal of the battery pack 40. Similarly, a negative terminal of an electric load such as an inverter 30 is connected to a negative power supply path L2 connected to a negative power supply terminal of the battery pack 40. Note that a relay switch SMR (system main relay switch) is provided in each of the positive power supply path L1 and the negative power supply path L2, and the relay switch SMR is configured to be able to switch between energization and deenergization.

[0016] The battery measuring device 50 is a device that measures the state of charge (SOC) and state of health (SOH) of each battery cell 42. The battery measuring device 50 is connected to the ECU 60, and outputs the state of each battery cell 42. The configuration of the battery measuring device 50 will be described later.

[0017] The ECU 60 requests the inverter control device to perform power running and generate electricity based on various information, such as accelerator and brake operation information, vehicle speed, and the state of the battery pack 40.

[0018] Next, a detailed description will be given of the battery measuring device 50. As shown in Fig. 2, in the first embodiment, a battery measuring device 50 is provided for each battery cell 42.

[0019] The battery measurement device 50 includes an ASIC unit 50a, a filter unit 55, and a current modulation circuit 56. The ASIC unit 50a includes a stabilized power supply unit 51, an input / output unit 52, a microcomputer unit 53 as a calculation unit, and a communication unit 54.

[0020] The stabilized power supply unit 51 is connected to the power line of the battery cell 42, and supplies power from the battery cell 42 to the input / output unit 52, the microcomputer unit 53, and the communication unit 54. The input / output unit 52, the microcomputer unit 53, and the communication unit 54 are driven based on this power.

[0021] The input / output unit 52 is connected to the battery cell 42 to be measured. More specifically, the input / output unit 52 has a DC voltage input terminal 57 that can input (measure) a DC voltage from the battery cell 42. A filter unit 55 is provided between the battery cell 42 and the DC voltage input terminal 57. That is, an RC filter 55a serving as a filter circuit and a Zener diode 55b serving as a protection element are provided between a positive terminal 57a and a negative terminal 57b of the DC voltage input terminal 57. That is, the RC filter 55a, the Zener diode 55b, and the like are connected in parallel to the battery cell 42.

[0022] Furthermore, the input / output unit 52 has a response signal input terminal 58 for inputting (measuring) a response signal (voltage fluctuation) reflecting the internal complex impedance information of the battery cell 42 between the terminals of the battery cell 42. Therefore, the input / output unit 52 functions as a response signal measurement unit.

[0023] The input / output unit 52 is also connected to the current modulation circuit 56, and has an instruction signal output terminal 59a that outputs an instruction signal to the current modulation circuit 56 to instruct the current modulation circuit 56 on the sine wave signal (AC signal) to be output from the battery cell 42. The input / output unit 52 also has a feedback signal input terminal 59b. The feedback signal input terminal 59b inputs, via the current modulation circuit 56, a current signal that is actually output (flows) from the battery cell 42 as a feedback signal (measurement signal).

[0024] The input / output unit 52 is connected to the microcomputer unit 53 and configured to output, to the microcomputer unit 53, a DC voltage inputted to a DC voltage input terminal 57, a response signal inputted to a response signal input terminal 58, a feedback signal inputted to a feedback signal input terminal 59b, etc. The input / output unit 52 has an internal AD converter and is configured to convert an input analog signal into a digital signal and output it to the microcomputer unit 53.

[0025] The input / output unit 52 is configured to receive an instruction signal from the microcomputer unit 53, and is configured to output an instruction signal from an instruction signal output terminal 59a to the current modulation circuit 56. The input / output unit 52 has an internal DA converter, and is configured to convert the digital signal received from the microcomputer unit 53 into an analog signal and output an instruction signal to the current modulation circuit 56. A DC bias (offset value) is applied to the sine wave signal instructed by the instruction signal to the current modulation circuit 56, so that the sine wave signal does not become a negative current (a reverse current to the battery cell 42).

[0026] The current modulation circuit 56 is a circuit that outputs a predetermined AC signal using the battery cell 42 to be measured as a power source. Specifically, the current modulation circuit 56 has a semiconductor switch element 56a (e.g., a MOSFET) as a signal control unit, and a resistor 56b as a shunt resistor connected in series to the semiconductor switch element 56a. The drain terminal of the semiconductor switch element 56a is connected to the positive power supply terminal of the battery cell 42, and the source terminal of the semiconductor switch element 56a is connected in series to one end of the resistor 56b. The other end of the resistor 56b is connected to the negative power supply terminal of the battery cell 42. The semiconductor switch element 56a is configured to be able to adjust the amount of current flow between the drain terminal and the source terminal. In addition, a resistor may be inserted in series in the current modulation circuit to adjust the voltage applied to the semiconductor switch element 56a depending on the operating region of the semiconductor switch element 56a.

[0027] The current modulation circuit 56 is also provided with a current measurement amplifier 56c (current sense amplifier) ​​as a current measurement unit connected to both ends of the resistor 56b. The current measurement amplifier 56c is configured to measure a signal (current signal) flowing through the resistor 56b and output the measurement signal as a feedback signal to a feedback signal input terminal 59b of the input / output unit 52.

[0028] The current modulation circuit 56 is also provided with a feedback circuit 56d. The feedback circuit 56d is configured to receive an instruction signal from the instruction signal output terminal 59a of the input / output unit 52 and to receive a feedback signal from the current measuring amplifier 56c. The feedback circuit 56d is configured to compare the instruction signal with the feedback signal and to output the result of the comparison to the gate terminal of the semiconductor switch element 56a.

[0029] Based on the signal from the feedback circuit 56d, the semiconductor switch element 56a adjusts the voltage applied between the gate and source to adjust the amount of current between the drain and source so that the sine wave signal (predetermined AC signal) specified by the instruction signal is output from the battery cell 42. If an error occurs between the waveform specified by the instruction signal and the waveform actually flowing through resistor 56b, the semiconductor switch element 56a adjusts the amount of current based on the signal from the feedback circuit 56d so that the error is corrected. This stabilizes the sine wave signal flowing through resistor 56b.

[0030] Next, a method for calculating the complex impedance of the battery cell 42 will be described. The battery measuring device 50 executes an impedance calculation process shown in Fig. 3 at a predetermined cycle. In the impedance calculation process, the microcomputer unit 53 sets a measurement frequency for the complex impedance (step S101). The measurement frequency is set from frequencies within a predetermined measurement range.

[0031] Next, the microcomputer unit 53 determines various parameters of the AC signal (measurement AC signal) to be output from the battery cell 42, and outputs an instruction signal to the input / output unit 52 to instruct the input / output unit 52 to output the measurement AC signal according to the various parameters (step S102). In this embodiment, the measurement AC signal is a sine wave signal. The various parameters are, for example, the amplitude, frequency, offset value, phase, etc. of the AC signal. Specifically, the microcomputer unit 53 determines the frequency of the sine wave signal (measurement AC signal) based on the measurement frequency. Note that, in the first embodiment, the amplitude and offset value of the sine wave signal (measurement AC signal) are predetermined values.

[0032] When the input / output unit 52 receives the instruction signal, it converts it into an analog signal using a DA converter and outputs it to the current modulation circuit 56. Based on the instruction signal, the current modulation circuit 56 outputs a measurement AC signal using the battery cell 42 as a power source. Specifically, based on the signal input via the feedback circuit 56d, the semiconductor switch element 56a adjusts the amount of current so that the measurement AC signal instructed by the instruction signal is output from the battery cell 42. As a result, the measurement AC signal is output from the battery cell 42.

[0033] When a measurement AC signal is output from the battery cell 42, that is, when a disturbance is applied to the battery cell 42, a voltage fluctuation that reflects the internal complex impedance information of the battery cell 42 occurs between the terminals of the battery cell 42. The input / output unit 52 inputs the voltage fluctuation via the response signal input terminal 58 and outputs it as a response signal to the microcomputer unit 53. At that time, the signal is converted into a digital signal by an AD converter and output.

[0034] After executing step S102, the microcomputer unit 53 inputs a response signal from the input / output unit 52 (step S103). The microcomputer unit 53 also acquires a current signal (i.e., a measurement AC signal output from the battery cell 42) flowing through the resistor 56b of the current modulation circuit 56 (step S104). Specifically, the microcomputer unit 53 inputs a feedback signal (measurement signal) as a current signal output from the current measurement amplifier 56c via the input / output unit 52.

[0035] Next, the microcomputer unit 53 calculates information about the complex impedance of the battery cell 42 based on the response signal and the current signal (feedback signal) (step S105). That is, the microcomputer unit 53 calculates all or any of the absolute value and phase of the complex impedance based on the real part of the response signal, the imaginary part of the response signal, the real part of the current signal, and the imaginary part of the current signal, etc. The microcomputer unit 53 outputs the calculation result to the ECU 60 via the communication unit 54 (step S106). Then, the calculation process ends.

[0036] This impedance calculation process is repeatedly executed until complex impedances for a plurality of frequencies within the measurement range are calculated. For example, the calculation process may be repeatedly executed until the measurement range is swept. Based on the calculation result, the ECU 60 creates, for example, a complex impedance plane plot (Cole-Cole plot) and grasps the characteristics of the electrodes, electrolyte, etc., for example, the state of charge (SOC) and state of health (SOH).

[0037] It is not necessary to create the entire Cole-Cole plot, and a part of it may be focused on. For example, the complex impedance of a specific frequency may be measured at regular time intervals while driving, and changes in SOC, SOH, battery temperature, etc. while driving may be understood based on the time change of the complex impedance of the specific frequency. Alternatively, the complex impedance of a specific frequency may be measured at time intervals such as once a day, once a lap, or once a year, and changes in SOH, etc. may be understood based on the time change of the complex impedance of the specific frequency.

[0038] However, after the AC signal starts to be output, the feedback signal (measurement signal) may not be stable for a certain period of time. This may be due to, for example, a current flowing through the circuit, which increases the resistance temperature of resistor 56b and the battery temperature, causing an effect (due to thermal drift). In other words, the resistance value of resistor 56b and the internal resistance of battery cell 42 change with the increase in temperature, causing a change in the measurement signal. If the measurement signal is not stable, the accuracy of the calculation of the complex impedance decreases.

[0039] Therefore, after the current modulation circuit 56 starts outputting an AC signal from the battery cell 42, the microcomputer unit 53 waits until the measurement signal (feedback signal) that is the measurement result reaches a steady state, and then calculates information about the complex impedance and outputs the calculation result. Specifically, the process is as described below.

[0040] Before deciding to calculate the complex impedance and executing the impedance calculation process described above, the battery measuring device 50 executes the preparation process shown in Fig. 4. In the preparation process, the microcomputer unit 53 of the battery measuring device 50 sets various parameters for an AC signal (preparatory AC signal) to be output from the battery cell 42 (step S201). In this embodiment, the preparation AC signal is the same as the measurement AC signal (sine wave signal). That is, the microcomputer unit 53 may set various parameters of the preparation AC signal in the same manner as in step S102. The frequency of the preparation AC signal is the measurement frequency of the complex impedance.

[0041] Next, the microcomputer unit 53 outputs an instruction signal to the input / output unit 52 to instruct the input / output unit 52 to output a preparatory AC signal according to the various parameters set in step S201 (step S202). When the input / output unit 52 receives the instruction signal, it converts the signal into an analog signal using a DA converter and outputs the analog signal to the current modulation circuit 56. Based on the instruction signal, the current modulation circuit 56 causes the preparatory AC signal to be output using the battery cell 42 as a power source.

[0042] Next, the microcomputer unit 53 inputs the measurement signal (feedback signal), which is the current signal output from the current measuring amplifier 56c, via the input / output unit 52, and judges whether the difference (amplitude difference) between the measurement signal input this time and the measurement signal input last time is equal to or less than a predetermined specified change amount (step S203). Note that, after the start of the preparation process, the first time step S203 is processed, a negative judgment is always made.

[0043] If the result of this determination is negative, after a predetermined unit time has elapsed, the microcomputer unit 53 executes the process of step S203 again. That is, the process is repeated until the difference in the measurement signal per unit time becomes equal to or less than the specified change amount. In other words, the preparation process is continued and the impedance calculation process is not executed until the difference in the measurement signal per unit time becomes equal to or less than the specified change amount.

[0044] On the other hand, if the determination result in step S203 is positive, the microcomputer unit 53 determines that the steady state has been reached and determines to execute the impedance calculation process (step S204). Then, the preparation process ends. After the preparation process ends, the microcomputer unit 53 executes the impedance calculation process at predetermined intervals as described above.

[0045] According to the first embodiment, the following effects can be obtained.

[0046] After the current modulation circuit 56 starts outputting the preparatory AC signal from the battery cell 42, the microcomputer unit 53 waits for the measurement signal (feedback signal) that is the measurement result to reach a steady state, and then calculates information about the complex impedance and outputs the calculation result. Therefore, in the impedance calculation process, it is possible to reduce the temperature rise caused by the measurement AC signal, suppress errors in the measurement signal, and improve the calculation accuracy of the complex impedance.

[0047] In addition, it is possible to accurately determine whether or not the steady state has been reached because the determination is based on a measurement signal that is easily affected by the resistance temperature of resistor 56b and the battery temperature of battery cell 42. Another advantage is that it does not require the addition of a special device such as a temperature sensor just to determine the steady state.

[0048] Incidentally, when the battery measuring device 50 is shipped or inspected periodically, an inspection device is connected to the battery measuring device 50 in place of the battery cell 42 at a factory or the like to inspect the performance of the battery measuring device 50. At this time, as described above, by configuring the microcomputer unit 53 to wait for the feedback signal to reach a steady state before calculating information related to the complex impedance, it is possible to reduce errors in the inspection results.

[0049] A detailed description will be given below. First, the flow of the performance inspection by the inspection device will be described. When the microcomputer unit 53 outputs an instruction signal to cause the inspection device (in place of the battery cell 42) to output an AC current by the current modulation circuit 56, the inspection device outputs the AC current corresponding to the instruction signal. At this time, the inspection device measures the output AC current and calculates an inspection voltage to be output as a result (complex number) of multiplication of a predetermined impedance value (inspection impedance value) and the measured current value. Then, the inspection device outputs the calculated inspection voltage to the battery measuring device 50. The battery measuring device 50 calculates and outputs a complex impedance based on the inspection voltage. An operator or the inspection device compares the complex impedance calculated by the battery measuring device 50 with the inspection impedance value to inspect the performance of the battery measuring device 50.

[0050] As described above, in the inspection device, in order to calculate and output the inspection voltage, steps such as input of instruction signal → output of AC current → measurement of AC current → calculation of inspection voltage → output of inspection voltage are required, and a predetermined waiting time is required until the inspection voltage is output. Therefore, if the battery measurement device 50 starts calculating the complex impedance immediately after starting to output the preparatory AC signal, there is a high possibility that an error or erroneous determination will occur in the calculation result because the inspection voltage is not normally output immediately after the start. Therefore, as described above, the microcomputer unit 53 is configured to wait for the feedback signal to become in a steady state after starting to output the preparatory AC signal by the current modulation circuit 56, and then calculate information regarding the complex impedance, thereby reducing the possibility of erroneous determination in the inspection by the above-mentioned inspection device. In other words, in the battery measurement device 50, a predetermined waiting time is set until the inspection voltage is output, so that the possibility of erroneous determination can be reduced.

[0051] (Modification of the first embodiment) Below, a modified example in which the configuration of the first embodiment is partially changed will be described.

[0052] In the first embodiment, if the determination based on the measurement signal (step S203) is positive, it is determined that the steady state has been reached. However, it may be determined that the steady state has been reached when a predetermined preparation time has elapsed since the start of output of the preparation AC signal. The predetermined time may be set based on an experiment, a simulation, or the like. The preparation time may be changed according to the outside air temperature of the vehicle, the resistance temperature of the resistor 56b, or the battery temperature. For example, when the outside air temperature of the vehicle, the resistance temperature of the resistor 56b, or the battery temperature is high, the preparation time may be shortened. In addition, the preparation time may be changed based on the elapsed time since the complex impedance was calculated last time. For example, when the elapsed time since the complex impedance was calculated last time is short, the preparation time may be shortened.

[0053] In the preparation process of the first embodiment, after outputting the preparation AC signal, the microcomputer unit 53 may calculate the complex impedance based on the response signal (voltage fluctuation) to the preparation AC signal and the measurement signal (current signal), and determine whether the difference in the magnitude (absolute value) of the complex impedance (difference from the previous value) is equal to or less than a predetermined specified change amount. In other words, it may determine whether the difference in the complex impedance per unit time is equal to or less than a predetermined specified change amount. Then, when the result of the determination based on this complex impedance is positive, the microcomputer unit 53 may determine that a steady state has been reached, and may decide to execute the impedance calculation process.

[0054] In the first embodiment, a resistance temperature sensor may be provided as a resistance temperature detection unit for detecting the resistance temperature of the resistor 56b, and after outputting a preparatory AC signal, the microcomputer unit 53 may determine whether the measured resistance temperature has reached a predetermined resistance temperature or whether the resistance temperature change amount (amount of change from the previous value) is equal to or less than the predetermined resistance temperature change amount. If the determination based on the resistance temperature is positive, the microcomputer unit 53 may determine that a steady state has been reached and may decide to execute an impedance calculation process.

[0055] In the first embodiment, a battery temperature sensor may be provided as a battery temperature detection unit that detects the battery temperature of the battery cells 42, and after outputting a preparatory AC signal, the microcomputer unit 53 may determine whether the measured battery temperature has reached a predetermined battery temperature or whether the amount of change in battery temperature (amount of change from the previous value) is equal to or less than the predetermined amount of change in battery temperature. If the determination based on the battery temperature is positive, the microcomputer unit 53 may determine that a steady state has been reached and may decide to execute an impedance calculation process.

[0056] The first embodiment may be implemented in combination with the modified example of the first embodiment. For example, two or more selected from the determination based on the measurement signal (step S203), the determination based on the complex impedance, the determination based on the resistance temperature, and the determination based on the battery temperature may be performed, and if all of the determination results are positive, the microcomputer unit 53 may determine that the steady state has been reached.

[0057] Second embodiment The configuration of the first embodiment may be modified as in the following second embodiment. In the second embodiment, differences from the configurations described in the above embodiments will be mainly described below. In addition, the second embodiment will be described using the power supply system 10 of the first embodiment as an example of a basic configuration.

[0058] The preparation process in the second embodiment will be described with reference to Fig. 5. In the preparation process in the second embodiment, the battery measurement device 50 sets various parameters for the preparation AC signal to be output from the battery cell 42 during the preparation process (step S301). In the second embodiment, the preparation AC signal is the same as the measurement AC signal (sine wave signal) in step S101. That is, the frequency of the preparation AC signal in the second embodiment is the measurement frequency.

[0059] Next, the microcomputer unit 53 sets a time (hereinafter referred to as preparation time) that is predicted to be required from the start of output of the preparatory AC signal until a steady state is reached, according to the frequency of the preparatory AC signal (step S302). The preparation time according to the frequency of the preparatory AC signal is set based on experiments, simulations, etc., and is stored in advance. Whether or not a steady state is reached in an experiment or the like may be determined comprehensively based on the measurement signal, the calculation result of the complex impedance, the resistance temperature, the battery temperature, or a combination of these, as in the first embodiment and its modified examples.

[0060] However, it was found that when the measurement frequency is lower than the specified frequency, the measurement signal varies depending on the phase of the preparatory AC signal at the start of output. In other words, it was found that the temperature cannot be raised sufficiently, and the required preparation time varies. A detailed explanation will be given based on FIG. 6. FIG. 6 shows the relationship between the real part of the complex impedance and the measurement frequency. FIG. 6 shows the calculation result of the complex impedance calculated after the preparation time has elapsed since the start of output of the preparatory AC signal. In FIG. 6, the line type is changed depending on the difference in phase at the start of output of the preparatory AC signal. As shown in FIG. 6, when the measurement frequency is equal to or higher than a certain frequency (specified frequency), there is almost no difference in the calculation result even if there is a difference in phase at the start of output of the preparatory AC signal.

[0061] On the other hand, when the measurement frequency is less than a certain frequency (a specified frequency), the difference in phase at the start of output of the preparatory AC signal causes variation in the calculation results. This is considered to be because, when the frequency is small, depending on the phase at the start of output, the proportion of the time period during which the current value based on the preparatory AC signal is greater than the offset value (current bias) during the time until the preparation time has elapsed may be large (see FIG. 7(a)) or small (see FIG. 7(b)). Note that FIG. 7 shows an extreme case for the sake of explanation. On the other hand, when the measurement frequency is equal to or greater than the specified frequency, the current value is averaged by the time the preparation time has elapsed, and its influence is reduced, so it is considered that no variation occurs.

[0062] Therefore, in the second embodiment, the microcomputer unit 53 judges whether or not the frequency of the preparatory AC signal is equal to or higher than a specified frequency (step S303). If the result of the judgment in step S303 is negative (if the frequency is less than the specified frequency), the microcomputer unit 53 sets (adjusts) the phase of the AC signal (step S304). Specifically, the microcomputer unit 53 sets the phase of the preparatory AC signal at the start of output so that the current value of the preparatory AC signal at the start of output is greater than the offset value and the slope of the current based on the preparatory AC signal at the start of output is positive. In other words, when the preparatory AC signal is a sine wave signal as shown in FIG. 8, the phase at the start of output is set to zero (0°).

[0063] After the process of step S304, or if the result of the determination in step S303 is positive (if the frequency is equal to or higher than the specified frequency), the microcomputer unit 53 outputs an instruction signal to the input / output unit 52 to instruct the output of a preparatory AC signal according to the various parameters set in steps S301 and S304 (step S305). When the instruction signal is input, the input / output unit 52 converts the signal into an analog signal by a DA converter and outputs the analog signal to the current modulation circuit 56. Based on the instruction signal, the current modulation circuit 56 causes the preparatory AC signal to be output using the battery cell 42 as a power source.

[0064] Then, the microcomputer unit 53 waits until the preparation time set in step S302 has elapsed (step S306). After the preparation time set in step S302 has elapsed, the microcomputer unit 53 determines that a steady state has been reached and decides to execute an impedance calculation process (step S307). Then, the preparation process ends. After the preparation process ends, the microcomputer unit 53 executes the impedance calculation process at predetermined intervals as described above.

[0065] According to the second embodiment, the following effects can be obtained.

[0066] After the start of output of the preparatory AC signal, the calculation of the complex impedance starts after the preparation time has elapsed. This reduces the temperature rise caused by the measurement AC signal, suppresses errors in the measurement signal, and improves the calculation accuracy of the complex impedance.

[0067] The preparation time is changed according to the frequency of the preparatory AC signal. Therefore, an appropriate preparation time can be set. In addition, when the frequency of the preparatory AC signal (measurement frequency in the above embodiment) is less than a specified frequency, the required preparation time may differ due to the influence of the phase at the start of output. Therefore, when the measurement frequency is less than the specified frequency, the phase at the start of output is adjusted. Specifically, the microcomputer unit 53 sets the phase of the preparatory AC signal at the start of output so that the current value of the preparatory AC signal at the start of output is greater than the offset value and the slope of the current based on the preparatory AC signal at the start of output is positive. For example, when the preparatory AC signal is a sine wave signal, the phase at the start of output is set to zero. This makes it possible to suppress errors in the calculation result and shorten the waiting time.

[0068] (Modification of the second embodiment) Below, a modified example in which the configuration of the second embodiment is partially changed will be described.

[0069] In the second embodiment, the phase of the preparatory AC signal does not need to be adjusted. In this case, the preparation time may be set assuming that the preparation time will be the longest, taking into consideration the influence of the phase of the preparatory AC signal at the start of output. Specifically, the microcomputer unit 53 may set the preparation time assuming that the current value of the AC signal at the start of output is equal to or less than the offset value and that the slope of the current based on the AC signal at the start of output is negative. For example, the microcomputer unit 53 may set the preparation time assuming that the phase of the preparatory AC signal at the start of output is 180°. This simplifies the processing.

[0070] In the second embodiment, when the phase of the preparatory AC signal is not adjusted and the frequency of the preparatory AC signal is less than the specified frequency, the preparation time may be changed according to the phase and frequency of the AC signal at the start of input / output. For example, even if the frequency is the same, the preparation time may be changed depending on whether the proportion of the time period during which the current value based on the preparatory AC signal is greater than the offset value is large (see FIG. 7(a)) or small (see FIG. 7(b)) due to the difference in phase.

[0071] In the second embodiment, the microcomputer unit 53 sets the phase at the start of output to zero (0°), but the phase may be set within a range of 0° or more and less than 90°.

[0072] Third embodiment The configuration of the first embodiment may be modified as in the following third embodiment. In the third embodiment, differences from the configurations described in the above embodiments will be mainly described below. In addition, the third embodiment will be described using the power supply system 10 of the first embodiment as an example of a basic configuration.

[0073] First, a method for determining various parameters of the measurement AC signal in step S101 of the impedance calculation process of the third embodiment will be described. In step S101 of the impedance calculation process, the microcomputer unit 53 estimates the magnitude of the complex impedance. For example, the previously measured complex impedance value (for example, Cole-Cole plot, etc.) may be stored, and the microcomputer unit 53 may estimate the magnitude of the complex impedance based on the measurement frequency. Alternatively, a map of the complex impedance may be created by an experiment or the like, and the magnitude of the complex impedance calculated by referring to the map may be estimated based on parameters related to the battery state, such as the previously measured deterioration level (SOH), the measurement frequency, and the battery temperature. In this case, the microcomputer unit 53 functions as an estimation unit.

[0074] Then, the microcomputer unit 53 sets the amplitude of the measurement AC signal according to the magnitude of the estimated complex impedance. To be more specific, when the magnitude of the complex impedance is small, the amplitude can be increased to perform calculations with higher accuracy. Therefore, when the magnitude of the complex impedance is estimated to be smaller than a predetermined value, the microcomputer unit 53 determines a larger amplitude from among the settable amplitudes. On the other hand, when the magnitude of the complex impedance is large, the amplitude can be reduced to perform calculations with higher accuracy. Therefore, when the magnitude of the complex impedance is estimated to be equal to or larger than a predetermined value, the microcomputer unit 53 determines a smaller amplitude from among the settable amplitudes. Note that the amplitude may be set from among the settable amplitudes so as to be inversely proportional to the magnitude of the complex impedance.

[0075] Next, the preparation process in the third embodiment will be described with reference to Fig. 9. In the preparation process, the battery measurement device 50 sets various parameters for an AC signal (preparatory AC signal) to be output from the battery cell 42 (step S401). In this embodiment, the preparation AC signal is the same as the measurement AC signal (sine wave signal) in step S101. The frequency of the preparation AC signal is the measurement frequency that is set in the impedance calculation process that is executed first.

[0076] Next, the microcomputer unit 53 sets a preparation time required from the start of outputting the preparation AC signal until the steady state is reached based on the amplitude of the preparation AC signal (step S402). In the third embodiment, the amplitude of the preparation AC signal is changed according to the amplitude of the measurement AC signal. It is known that the larger the amplitude of the preparation AC signal, the larger the effective power is, and the easier it is for the resistance 56b and the battery temperature to rise. For this reason, a time proportional to the amplitude of the preparation AC signal may be set as the time required from the start of outputting the preparation AC signal until the steady state is reached. If the amplitude is equal to or greater than a predetermined value, a first time may be set as the preparation time, and if the amplitude is less than the predetermined value, a second time shorter than the first time may be set. An appropriate preparation time according to the amplitude of the preparation AC signal may be identified by experiment or the like.

[0077] Next, the microcomputer unit 53 outputs an instruction signal to the input / output unit 52 to instruct the output of a preparatory AC signal according to the various parameters set in step S401 (step S403). When the instruction signal is input, the input / output unit 52 converts the signal into an analog signal using a DA converter and outputs the analog signal to the current modulation circuit 56. Based on the instruction signal, the current modulation circuit 56 causes the preparatory AC signal to be output using the battery cell 42 as a power source.

[0078] Next, the microcomputer unit 53 judges whether or not the preparation time set in step S402 has elapsed (step S404). If the judgment result is negative, the microcomputer unit 53 executes the process of step S404 again after the predetermined time has elapsed. In other words, it waits until the preparation time has elapsed. On the other hand, if the judgment result in step S404 is positive, the microcomputer unit 53 judges that a steady state has been reached and decides to execute the impedance calculation process (step S405). Then, the preparation process ends. After the preparation process ends, the microcomputer unit 53 executes the impedance calculation process at predetermined intervals as described above.

[0079] According to the third embodiment, the following effects can be obtained.

[0080] After the start of output of the preparatory AC signal, the calculation of the complex impedance starts after the preparation time has elapsed. This reduces the temperature rise caused by the measurement AC signal, suppresses errors in the measurement signal, and improves the calculation accuracy of the complex impedance. At this time, the preparation time is changed according to the amplitude of the preparation AC signal. Therefore, an appropriate preparation time can be set.

[0081] The microcomputer unit 53 sets an appropriate amplitude of the measuring AC signal in accordance with the magnitude of the estimated complex impedance, thereby improving the accuracy of calculating the complex impedance.

[0082] (Fourth embodiment) The configuration of the first embodiment may be modified as in the following fourth embodiment. In the fourth embodiment, differences from the configurations described in the above embodiments will be mainly described below. In addition, the fourth embodiment will be described using the power supply system 10 of the first embodiment as an example of a basic configuration.

[0083] The preparation process in the fourth embodiment will be described with reference to Fig. 10. In the preparation process, the battery measurement device 50 sets various parameters for the preparation AC signal to be output from the battery cell 42 (step S501). In this embodiment, the preparation AC signal is a signal having a larger power (effective power) than the measurement AC signal in step S101. For example, the microcomputer unit 53 sets the preparation AC signal with an amplitude larger than that of the measurement AC signal. The process from step S502 onwards is similar to the process from step S202 onwards in the first embodiment, and therefore detailed description will be omitted.

[0084] According to the fourth embodiment, the following effects can be obtained.

[0085] A preparatory AC signal having a larger effective power than the measurement AC signal is output, and the calculation of the complex impedance starts after the measurement result reaches a steady state. The time until the steady state is reached can be shortened compared to when the various parameters of the preparatory AC signal are set to the same as those of the measurement AC signal.

[0086] (Modification of the fourth embodiment) In step S503 of the fourth embodiment, the determination as to whether or not the steady state has been reached may be made in the same manner as in the first embodiment and its modified examples. That is, one or more determinations may be made from among a determination based on a measurement signal (step S203), a determination based on complex impedance, a determination based on resistance temperature, and a determination based on battery temperature, and if the determination results are positive, the microcomputer unit 53 may determine that the steady state has been reached.

[0087] In the fourth embodiment, a resistance temperature sensor that measures the resistance temperature of resistor 56b and a battery temperature sensor that measures the battery temperature of battery cell 42 may be provided, and various parameters of the preparatory AC signal may be set so as to change the magnitude of power according to the resistance temperature and battery temperature. For example, microcomputer unit 53 may set various parameters of the preparatory AC signal so that the power is larger when the resistance temperature and battery temperature at the start of output of the preparatory AC signal are equal to or lower than a threshold value compared to when they are higher than the threshold value.

[0088] In the fourth embodiment, the microcomputer unit 53 may change various parameters of the preparatory AC signal so as to gradually reduce the power from the start to the steady state. In this way, it is possible to prevent the temperature (resistance temperature and battery temperature) from rising too much. In addition, it is possible to suppress the influence of a sudden change in the current value (induced electromotive force, etc.).

[0089] (Other variations) In the preparation process of the second or third embodiment, various parameters of the preparation AC signal may be set so that the power of the preparation AC signal is greater than that of the measurement AC signal, as in the fourth embodiment. This makes it possible to shorten the preparation time.

[0090] In the above embodiment and modified examples, the battery measuring device 50 may measure the impedance of battery cells 42 connected in parallel. That is, in order to increase the battery capacity, a plurality of battery cells 42 may be connected in parallel and grouped together to form a single unit (battery module). Similarly, the battery measuring device 50 may measure the impedance of battery cells 42 connected in series. That is, a plurality of battery cells 42 may be connected in series and grouped together to form a single unit (battery module).

[0091] In the above embodiment, the battery measurement device 50 may input an AC signal from an external power source to the battery cell 42 (or the battery module 41), measure a response signal (voltage fluctuation) and a current signal in response to the AC signal, and calculate the complex impedance based on the response signal and the current signal.

[0092] In the above embodiment, the preparation time may be changed for each vehicle model.

[0093] The battery measuring device 50 of the above embodiment may be used in a vehicle such as an HEV, an EV, a PHV, an auxiliary battery, an electric airplane, an electric motorcycle, or an electric ship. In the above embodiment, the battery cells 42 may be connected in parallel.

[0094] Although the AC signal in the above embodiment is a sine wave signal, the AC signal may be changed arbitrarily, and may be a square wave, a triangular wave, or the like.

[0095] The disclosure in this specification is not limited to the exemplified embodiments. The disclosure includes the exemplified embodiments and modifications based thereon by those skilled in the art. For example, the disclosure is not limited to the combination of parts and / or elements shown in the embodiments. The disclosure can be implemented by various combinations. The disclosure can have additional parts that can be added to the embodiments. The disclosure includes the omission of parts and / or elements of the embodiments. The disclosure includes the substitution or combination of parts and / or elements between one embodiment and another embodiment. The disclosed technical scope is not limited to the description of the embodiments. Some disclosed technical scopes are indicated by the description of the claims, and should be interpreted as including all modifications within the meaning and scope equivalent to the description of the claims.

[0096] 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. [Explanation of symbols]

[0097] 42... battery cell, 50... battery measuring device, 52... input / output section, 53... microcomputer section, 56a... semiconductor switch element, 56c... current measuring amplifier.

Claims

1. In a battery measuring device (50) for measuring the state of a storage battery (42), A signal control unit (56a) for outputting an AC signal from the storage battery or inputting an AC signal to the storage battery; A current measuring unit (56c) that measures the AC signal; a response signal measurement unit (52) for measuring a response signal of the storage battery in response to the AC signal; a calculation unit (53) that calculates information about a complex impedance of the storage battery based on measurement results of the AC signal measured by the current measurement unit and the response signal measured by the response signal measurement unit, The calculation unit waits for a measurement result of the AC signal to reach a steady state after the signal control unit starts inputting and outputting the AC signal, and then calculates information about the complex impedance and outputs the calculation result. the calculation unit is configured to determine that the measurement result has reached a steady state and output a calculation result when a predetermined preparation time has elapsed since the signal control unit started inputting and outputting the AC signal to the storage battery; The preparation time is set according to a frequency of the AC signal input / output from the start of input / output of the AC signal by the signal control unit until the measurement result reaches a steady state.

2. The AC signal is DC biased; 2. The battery measuring device of claim 1, wherein when the frequency of the AC signal input / output by the signal control unit after the start of input / output of the AC signal until the measurement result reaches a steady state is less than a specified frequency, the phase of the AC signal at the start of input / output is set so that the current value based on the AC signal at the start of input / output is greater than or equal to a DC bias and the slope of the current value based on the AC signal at the start of input / output is positive.

3. In a battery measuring device (50) for measuring the state of a storage battery (42), A signal control unit (56a) for outputting an AC signal from the storage battery or inputting an AC signal to the storage battery; A current measuring unit (56c) that measures the AC signal; a response signal measurement unit (52) for measuring a response signal of the storage battery in response to the AC signal; a calculation unit (53) that calculates information about a complex impedance of the storage battery based on measurement results of the AC signal measured by the current measurement unit and the response signal measured by the response signal measurement unit, The calculation unit waits for a measurement result of the AC signal to reach a steady state after the signal control unit starts inputting and outputting the AC signal, and then calculates information about the complex impedance and outputs the calculation result. the calculation unit is configured to determine that the measurement result has reached a steady state and output a calculation result when a predetermined preparation time has elapsed since the signal control unit started inputting and outputting the AC signal to the storage battery; The preparation time is set according to the amplitude of the AC signal input / output from the start of input / output of the AC signal by the signal control unit until the measurement result reaches a steady state.

4. An estimation unit (53) that estimates a complex impedance of the storage battery, 4. The battery measurement device according to claim 3, wherein an amplitude of an AC signal to be input or output is set in accordance with an absolute value of the complex impedance estimated by the estimation unit.

5. In a battery measuring device (50) for measuring the state of a storage battery (42), A signal control unit (56a) for outputting an AC signal from the storage battery or inputting an AC signal to the storage battery; A current measuring unit (56c) that measures the AC signal; a response signal measurement unit (52) for measuring a response signal of the storage battery in response to the AC signal; a calculation unit (53) that calculates information about a complex impedance of the storage battery based on measurement results of the AC signal measured by the current measurement unit and the response signal measured by the response signal measurement unit, The calculation unit waits for a measurement result of the AC signal to reach a steady state after the signal control unit starts inputting and outputting the AC signal, and then calculates information about the complex impedance and outputs the calculation result. The calculation unit calculates information regarding the complex impedance of the storage battery after the signal control unit starts inputting and outputting the AC signal to the storage battery, and when the change in the magnitude of the complex impedance per unit time becomes equal to or less than a specified change amount, it determines that the measurement results have reached a steady state and outputs the calculation results thereafter.

6. In a battery measuring device (50) for measuring the state of a storage battery (42), A signal control unit (56a) for outputting an AC signal from the storage battery or inputting an AC signal to the storage battery; A current measuring unit (56c) that measures the AC signal; a response signal measurement unit (52) for measuring a response signal of the storage battery in response to the AC signal; a calculation unit (53) that calculates information about a complex impedance of the storage battery based on measurement results of the AC signal measured by the current measurement unit and the response signal measured by the response signal measurement unit, the calculation unit waits for a measurement result of the AC signal to reach a steady state after the signal control unit starts inputting and outputting the AC signal, and then calculates information about the complex impedance and outputs the calculation result; The current measurement unit is configured to measure the AC signal via a shunt resistor, a resistance temperature detection unit for detecting a resistance temperature of the shunt resistor; The calculation unit determines that the measurement result has reached a steady state when the resistance temperature reaches a predetermined resistance temperature or when the amount of change in the resistance temperature per unit time becomes equal to or less than a predetermined amount of change in resistance temperature after the signal control unit starts inputting and outputting the AC signal to the storage battery, calculates information about the complex impedance, and outputs the calculation result.

7. In a battery measuring device (50) for measuring the state of a storage battery (42), A signal control unit (56a) for outputting an AC signal from the storage battery or inputting an AC signal to the storage battery; A current measuring unit (56c) that measures the AC signal; a response signal measurement unit (52) for measuring a response signal of the storage battery in response to the AC signal; a calculation unit (53) that calculates information about a complex impedance of the storage battery based on measurement results of the AC signal measured by the current measurement unit and the response signal measured by the response signal measurement unit, the calculation unit waits for a measurement result of the AC signal to reach a steady state after the signal control unit starts inputting and outputting the AC signal, and then calculates information about the complex impedance and outputs the calculation result; a battery temperature detection unit for detecting a battery temperature of the storage battery; The calculation unit determines that the measurement result has reached a steady state when the battery temperature reaches a predetermined battery temperature or when the amount of change in the battery temperature per unit time becomes equal to or less than a predetermined amount of change in battery temperature after the signal control unit starts inputting and outputting the AC signal to the storage battery, calculates information regarding the complex impedance, and outputs the calculation result.

8. In a battery measuring device (50) for measuring the state of a storage battery (42), A signal control unit (56a) for outputting an AC signal from the storage battery or inputting an AC signal to the storage battery; A current measuring unit (56c) that measures the AC signal; a response signal measurement unit (52) for measuring a response signal of the storage battery in response to the AC signal; a calculation unit (53) that calculates information about a complex impedance of the storage battery based on measurement results of the AC signal measured by the current measurement unit and the response signal measured by the response signal measurement unit, the calculation unit waits for a measurement result of the AC signal to reach a steady state after the signal control unit starts inputting and outputting the AC signal, and then calculates information about the complex impedance and outputs the calculation result; The signal control unit inputs and outputs a measurement AC signal after the measurement result reaches a steady state, and also inputs and outputs a preparatory AC signal having a higher effective power than the measurement AC signal after the signal control unit starts inputting and outputting the AC signal until the measurement result reaches a steady state.

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