Impedance Calculation Device

Abstract

To provide an impedance calculation device capable of precisely calculating impedance of a rechargeable battery.SOLUTION: An impedance calculation device calculates impedance of a rechargeable battery by applying an AC signal to the rechargeable battery from a signal application section during an impedance calculation period. The impedance calculation device includes: an error calculation section for calculating an impedance error of the rechargeable battery by applying an AC signal at a prescribed frequency in which at least one of the real number component and the imaginary number component of the impedance of the rechargeable battery becomes a prescribed value during an error calculation period; an impedance calculation section for calculating the impedance of a rechargeable battery during the impedance calculation period; and a correction section for correcting the impedance of a rechargeable battery calculated by the impedance calculation section on the basis of the impedance error. Calculation of the impedance error by the error calculation section and calculation of impedance by the impedance calculation section are performed by conduction of the same closed circuit including the rechargeable battery and the signal application section.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an impedance calculation device that calculates the impedance of a storage battery. [Background technology]

[0002] Conventionally, there is known a device that uses the impedance of a storage battery to monitor the state of the storage battery. In this device, an AC signal is applied to the storage battery, and the impedance of the storage battery is calculated in that state. Then, the state of the storage battery, such as deterioration of the storage battery, is monitored based on the calculated impedance.

[0003] In this device, when calculating the impedance of the storage battery, an AC signal is applied to the storage battery, so that a current flows through the electrical path that applies the AC signal to the storage battery, and a magnetic flux is generated by the current. If an induced electromotive force is generated in a voltage response detection circuit including the storage battery by this magnetic flux, the accuracy of the impedance calculation decreases. As a technology for suppressing the decrease in the accuracy of the impedance calculation due to the induced electromotive force, a technology using a four-terminal method is known (for example, Patent Document 1). In this technology, when calculating the resistance values ​​of the first and second objects to be measured, a first electrical path that supplies a first DC current to the first object to be measured and a second electrical path that supplies a second DC current to the second object to be measured are arranged in parallel. Then, first and second DC currents of opposite polarity and equal magnitude are simultaneously passed through the first and second electrical paths. This makes it possible to cancel out the magnetic fluxes generated in the first and second objects to be measured due to the transient states of the first and second DC currents, and to prevent the generation of induced electromotive forces in each electrical path. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2010-2199 A Summary of the Invention [Problem to be solved by the invention]

[0005] The above technique has many limitations on the layout of the electrical path and the direct current flowing through the electrical path, which causes inconveniences such as limitations on devices that can be used. There is still room for improvement in the technique for calculating the impedance of a storage battery.

[0006] The present invention has been made in consideration of the above circumstances, and has an object to provide an impedance calculation device that can accurately calculate the impedance of a storage battery. [Means for solving the problem]

[0007] The means for solving the above problem is An impedance calculation device that is applied to a power supply system including a storage battery, and calculates an impedance of the storage battery by applying an AC signal to the storage battery by a signal application unit during a predetermined impedance calculation period, an error calculation unit that applies the AC signal having a specified frequency such that at least one of a real component and an imaginary component of the impedance of the storage battery becomes a specified value during an error calculation period different from the impedance calculation period, and calculates an impedance error of the storage battery; an impedance calculation unit that calculates an impedance of the storage battery during the impedance calculation period; a correction unit that corrects the impedance of the storage battery calculated by the impedance calculation unit based on the impedance error, The calculation of the impedance error by the error calculation unit and the calculation of the impedance by the impedance calculation unit are performed by using the same closed circuit including the storage battery and the signal application unit while the closed circuit is energized.

[0008] According to the above configuration, the shape of a closed circuit (for example, the first closed circuit LC1 in FIG. 4) including the storage battery and the signal application unit is constant when the impedance error is calculated in the error calculation period and when the impedance is calculated in the impedance calculation period. Therefore, when the impedance is calculated in the impedance calculation period, the error caused by the induced electromotive force generated in the closed circuit can be appropriately corrected using the impedance error calculated in the error calculation period. As a result, the impedance of the storage battery can be calculated with high accuracy. [Brief description of the drawings]

[0009] [Figure 1] 1 is an overall configuration diagram of a power supply system according to a first embodiment. [Diagram 2] 4A and 4B are diagrams showing an equivalent circuit model of an internal resistance and frequency characteristics of impedance. [Diagram 3] 5 is a flowchart showing the procedure of a correction process according to the first embodiment. [Figure 4] A diagram showing a closed circuit that generates an induced electromotive force. [Diagram 5] An explanation of Faraday's law and Biot-Savart's law. [Figure 6] FIG. 13 is a diagram showing the correspondence relationship between the logarithm of a calculated frequency and the imaginary component of impedance. [Figure 7] FIG. 4 is an overall configuration diagram of a power supply system according to a modified example of the first embodiment. [Figure 8] 10 is a flowchart showing the procedure of a correction process according to a second embodiment. [Figure 9] FIG. 11 is an overall configuration diagram of a power supply system according to a third embodiment. [Figure 10] FIG. 13 is an overall configuration diagram of a power supply system according to a fourth embodiment. [Figure 11] 13 is a flowchart showing the procedure of a correction process according to a fourth embodiment. [Figure 12] FIG. 13 is an overall configuration diagram of a battery management system according to a fifth embodiment. [Figure 13] FIG. 13 is a diagram showing the overall configuration of a battery management system according to another embodiment. [Figure 14]FIG. 13 is a diagram showing the overall configuration of a battery management system according to another embodiment. [Figure 15] FIG. 13 is a diagram showing the overall configuration of a battery management system according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] (First embodiment) Hereinafter, a first embodiment in which an impedance calculation device according to the present invention is applied to a power supply system 10 of a vehicle (for example, a hybrid vehicle or an electric vehicle) will be described with reference to the drawings.

[0011] As shown in FIG. 1, a power supply system 10 includes a motor 20 as a rotating electric machine, an inverter 30, a storage battery 40, a current modulation circuit 50, and a control device 60 as an impedance calculation device.

[0012] 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.

[0013] The inverter 30 includes a full-bridge circuit having upper and lower arms in the same number as the number of phases of the phase windings of the motor 20, and the current flowing in each phase winding is adjusted by switching operations of a switch (semiconductor switching element) provided in each arm. The inverter 30 also includes a smoothing capacitor and a resistive element connected in parallel to the full-bridge circuit.

[0014] Each switch of the inverter 30 is connected to the control device 60, and the control device 60 performs switching operations on each switch based on various detection information of the motor 20 and requests for power running and regenerative power generation. As a result, the storage battery 40 inputs and outputs power to and from the motor 20 via the inverter 30. Specifically, the storage battery 40 discharges when the motor 20 is powered, and supplies power to the motor 20 via the inverter 30. Furthermore, when the motor 20 is generating power through regenerative power generation, the motor 20 generates power based on the power from the driving wheels, and supplies the generated power to the storage battery 40 via the inverter 30 to charge the storage battery 40.

[0015] The storage battery 40 has an inter-terminal voltage of, for example, 100 V or more, and is an assembled battery configured by connecting a plurality of battery cells in series. The battery cells are, for example, lithium ion batteries. The storage battery 40 has an internal resistance 42 together with an assembly 41 of battery cells.

[0016] 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 terminal of the storage battery 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 terminal of the storage battery 40. A first switch SW1 and a second switch SW2 serving as a system main relay switch are provided in the positive power supply path L1 and the negative power supply path L2 between the storage battery 40 and the electric load, and the first and second switches SW1 and SW2 are configured to be able to switch between energizing and deenergizing the electric load. In this embodiment, the first and second switches SW1 and SW2 correspond to "load side switches."

[0017] The storage battery 40 is configured to be chargeable by a charger 80 external to the power supply system 10, such as a home commercial power source. The storage battery 40 is connected to a first connection terminal TC1 and a second connection terminal TC2, and is configured to be connectable to the charger 80 via the first and second connection terminals TC1 and TC2.

[0018] The first connection terminal TC1 is connected to the positive power supply path L1 via the positive charging path L3. In the positive power supply path L1, a connection point PA between the positive charging path L3 and the positive power supply path L1 is located closer to the storage battery 40 than the first switch SW1. In the positive charging path L3, a third switch SW3 is provided between the first connection terminal TC1 and the connection point PA. In addition, the second connection terminal TC1 is connected to the negative power supply path L2 via the negative charging path L4. In the negative power supply path L2, a connection point PB between the negative charging path L4 and the negative power supply path L2 is located closer to the storage battery 40 than the second switch SW2. In the negative charging path L4, a fourth switch SW4 is provided between the second connection terminal TC2 and the connection point PB. In this embodiment, the third and fourth switches SW3 and SW4 correspond to "charger side switches".

[0019] The current modulation circuit 50 is a circuit that uses the storage battery 40 as a power source and causes the storage battery 40 to output a predetermined AC signal using the power output from the storage battery 40. The AC signal is, for example, a sine wave signal. The current modulation circuit 50 has a semiconductor switch element 51 (for example, a MOSFET) and a resistor 52 connected in series to the semiconductor switch element 51. The drain terminal of the semiconductor switch element 51 is connected to the positive power supply path L1, and the source terminal of the semiconductor switch element 51 is connected in series to one end of the resistor 52. The other end of the resistor 52 is connected to the negative power supply path L2. The semiconductor switch element 51 is configured to be able to adjust the amount of current passing between the drain terminal and the source terminal.

[0020] The current modulation circuit 50 also includes a current detection amplifier 54 connected across the resistor 52. The current detection amplifier 54 detects the current flowing through the resistor 52, and outputs the detected value as a feedback signal.

[0021] The current modulation circuit 50 is also provided with a feedback circuit 53. The feedback circuit 53 is configured to receive an instruction signal from the control device 60 and a feedback signal from the current detection amplifier 54. The feedback circuit 53 is configured to compare the instruction signal with the feedback signal and output the result to the gate terminal of the semiconductor switch element 51.

[0022] Based on the signal from the feedback circuit 53, the semiconductor switch element 51 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 as the AC signal instructed by the instruction signal is output from the storage battery 40. If an error occurs between the waveform instructed by the instruction signal and the waveform actually flowing through the resistor 52, the semiconductor switch element 51 adjusts the amount of current so that the error is corrected based on the feedback signal from the feedback circuit 53. This stabilizes the sine wave signal flowing through the resistor 52.

[0023] The power supply system 10 includes a voltage sensor 61 , a current sensor 62 , a temperature sensor 63 , and a pressure sensor 64 .

[0024] The voltage sensor 61 is connected in parallel to the storage battery 40, and detects a fluctuating voltage Vs, which is a terminal-to-terminal voltage between the positive and negative terminals of the storage battery 40. When no instruction signal is input from the control device 60, the fluctuating voltage Vs becomes the DC voltage of the storage battery 40. The current sensor 62 is connected in series to the negative power supply path L2 side of the series connection of the semiconductor switch element 51 and the resistor 52 in the current modulation circuit 50, and detects a fluctuating current Im, which is a current flowing from the storage battery 40 to the resistor 52, that is, a current flowing to the storage battery 40. When the control device 60 detects a feedback signal from the current detection amplifier 54, it is possible to detect the fluctuating current Im from this feedback signal, and it is possible to omit the current sensor 62.

[0025] The temperature sensor 63 detects a battery temperature TB which is the temperature of the storage battery 40. The pressure sensor 64 detects the pressure on the storage battery 40, specifically, the battery pressure PR which is the internal pressure of the storage battery 40. The detection values ​​of the sensors 61-64 are input to the control device 60.

[0026] The control device 60 includes a well-known microcomputer including a CPU, a ROM, a RAM, a flash memory, and the like. The control device 60 operates by receiving power from the storage battery 40, and realizes various functions for controlling the vehicle by referring to the calculation programs and control data in the ROM. Specifically, the control device 60 controls the open / close states of the first to fourth switches SW1 to SW4. The control device 60 also inputs an instruction signal to the current modulation circuit 50 based on the input detection value, causes the storage battery 40 to output an AC signal, and calculates the internal resistance 42 of the storage battery 40.

[0027] The upper side of FIG. 2 shows an equivalent circuit model of the internal resistance 42 of the storage battery 40. In this embodiment, the equivalent circuit model is expressed as a series connection of each resistance model of an ohmic resistance model, a reaction resistance model, and a diffusion resistance model. The ohmic resistance model represents the current resistance of the electrodes and electrolyte constituting the storage battery 40, and is expressed as a series connection of a coil component LX and a first resistance component RA. The reaction resistance model represents the resistance due to the electrode interface reaction at the electrode, and is expressed as a parallel connection of a second resistance component RB and a capacitance component CX. The diffusion resistance model represents the resistance associated with the diffusion of lithium ions into the electrode active material applied to the electrode surface, and is expressed as a third resistance component RC connected in series to the second resistance component RB. That is, the storage battery 40 has resistance components RA to RC, a coil component LX, and a capacitance component CX as circuit components of the equivalent circuit model of the internal resistance 42, and the value of the internal resistance 42 is expressed as an impedance ZB, which is a complex impedance, by these components. The control device 60 calculates this impedance ZB.

[0028] The frequency characteristic of the impedance ZB is shown at the bottom of FIG. 2. The impedance ZB changes depending on the frequency F of the AC signal instructed by the instruction signal, and in the low frequency region, the real component ZR of the impedance ZB increases as the applied frequency F decreases. The imaginary component ZI of the impedance ZB becomes zero at the first specific frequency Ftg1. Hereinafter, the impedance ZB at the first specific frequency Ftg1 is referred to as the ohmic resistance RH. In the frequency range higher than the first specific frequency Ftg1, the ohmic resistance model becomes dominant, and the absolute value of the imaginary component ZI increases as the applied frequency F increases (the imaginary component ZI increases). In this embodiment, the first specific frequency Ftg1 corresponds to the "specified frequency, ohmic frequency."

[0029] On the other hand, in a frequency range lower than the first specific frequency Ftg1, the imaginary component ZI has a maximum value at the second specific frequency Ftg2. In a frequency range lower than the first specific frequency Ftg1 and higher than the second specific frequency Ftg2, the reaction resistance model becomes dominant, and as the applied frequency F decreases, the absolute value of the imaginary component ZI increases and then decreases. Also, in a frequency range lower than the second specific frequency Ftg2, the diffusion resistance model becomes dominant, and as the applied frequency F decreases, the absolute value of the imaginary component ZI increases (the imaginary component ZI decreases).

[0030] 1, the control device 60 is connected to an IG switch 65. The IG switch 65 is a start switch for the vehicle. The control device 60 monitors the open / closed state of the IG switch 65.

[0031] Incidentally, it is known that the impedance ZB is affected by the induced electromotive force Vid. Here, the induced electromotive force Vid is, for example, an electromagnetic induction electromotive force induced in a voltage response detection circuit including the storage battery 40 by a magnetic flux generated by a current flowing through an electric path such as the positive power supply path L1 or the negative power supply path L2. In the power supply system 10 that outputs an AC signal to the storage battery 40 in order to calculate the impedance ZB of the storage battery 40 as in this embodiment, a current flows through the electric path when the storage battery 40 outputs an AC signal, and an induced electromotive force Vid is generated in the storage battery 40. When the induced electromotive force Vid is generated in the storage battery 40, the calculation accuracy (precision) of the impedance ZB decreases.

[0032] 2, the impedance ZB when no induced electromotive force Vid is generated in the storage battery 40 is shown by a solid line, and the impedance Z when the induced electromotive force Vid is generated is shown by a dashed line. Hereinafter, the impedance ZB when no induced electromotive force Vid is generated will be referred to as the specific impedance ZB.

[0033] As shown in Fig. 2, the imaginary component ZI of the impedance Z does not become zero at the first specific frequency Ftg1. The inventors have repeatedly studied the reason why the imaginary component ZI of the impedance Z does not become zero at the first specific frequency Ftg1, and have found that the cause is an error (difference) ΔZ due to the induced electromotive force Vid. The inventors have focused on this point and have found that the impedance Z can be calculated with high accuracy by correcting the impedance Z based on the error ΔZ, which is the imaginary component ZI of the impedance Z at the first specific frequency Ftg1.

[0034] Based on the above findings, in this embodiment, an AC signal of a first specific frequency Ftg1 that makes the imaginary component ZI of the specific impedance ZB zero is applied to the storage battery 40 during the error calculation period TG to calculate the error ΔZ. In other words, if the imaginary component ZI of the impedance Z calculated by applying the AC signal of the first specific frequency Ftg1 is not zero, the imaginary component ZI can be calculated as the error ΔZ due to the induced electromotive force Vid. Then, when the impedance Z of the storage battery 40 is calculated during an impedance calculation period TI different from the error calculation period TG, a correction process is performed to correct the impedance Z of the storage battery 40 based on this error ΔZ. This makes it possible to accurately calculate the impedance Z of the storage battery 40 by suppressing the influence of the induced electromotive force Vid.

[0035] A flowchart of the correction process of this embodiment is shown in Fig. 3. The control device 60 repeatedly performs the correction process at each predetermined control period.

[0036] When the control process is started, first, in step S10, it is determined whether or not it is the impedance calculation period TI. For example, during the charging period of the storage battery 40 by the charger 80, the IG switch 65 is switched to the open state, and the inverter 30 is stopped. In this embodiment, a form in which the error calculation period TG is set during the charging period of the storage battery 40 by the charger 80 is illustrated. If it is determined that it is the error calculation period TG and a negative determination is made in step S10, the first and second switches SW1 and SW2 are opened in step S12. That is, in this embodiment, the error ΔZ is calculated during the open period of the first and second switches SW1 and SW2.

[0037] During the charging period of the storage battery 40, the charger 80 is connected to the first and second connection terminals TC1 and TC2. Then, the third and fourth switches SW3 and SW4 are closed to charge the storage battery 40. When the charging of the storage battery 40 is completed, the third and fourth switches SW3 and SW4 are opened. In this embodiment, during the connection period between the first and second connection terminals TC1 and TC2 and the charger 80, the error ΔZ is calculated during the open period of the third and fourth switches SW3 and SW4 before the charging of the storage battery 40 starts, or during the open period of the third and fourth switches SW3 and SW4 after the charging of the storage battery 40 is completed. That is, in this embodiment, the error ΔZ is calculated during the connection period between the first and second connection terminals TC1 and TC2 and the charger 80, and during the open period of the third and fourth switches SW3 and SW4. Therefore, in step S12, the first and second switches SW1 and SW2 as well as the third and fourth switches SW3 and SW4 are opened.

[0038] In step S14, the battery temperature TB of the storage battery 40 is acquired using the temperature sensor 63, and in step S16, the battery pressure PR of the storage battery 40 is acquired using the pressure sensor 64. In the following step S18, the SOC of the storage battery 40 is calculated. For example, during a period in which power supply to the storage battery 40 is stopped, the SOC of the storage battery 40 can be calculated based on the open circuit voltage OCV, which is a voltage value acquired from the voltage sensor 61. In this embodiment, the processes of steps S14 to S18 correspond to a "parameter acquisition unit."

[0039] In step S20, a first specific frequency Ftg1 for calculating the ohmic resistance RH of the storage battery 40 is set based on the battery temperature TB, battery pressure PR, and SOC acquired in steps S14 to S18. The first specific frequency Ftg1 is a frequency correlated with the battery temperature TB, battery pressure PR, and SOC.

[0040] For example, in step S14, if the amount of change in the battery temperature TB detected by the temperature sensor 63 during a specified time is within a predetermined range of change, the battery temperature TB is in an equilibrium state, and therefore the average value is acquired as the battery temperature TB of the storage battery 40. Then, in step S20, an instruction signal corresponding to the acquired battery temperature TB is applied to the current modulation circuit 50. Specifically, the storage unit 66 of the control device 60 stores correlation information indicating the relationship between the first specific frequency Ftg1 and each battery parameter, such as the battery temperature TB, the battery pressure PR, and the SOC. In step S20, the correlation information stored in the storage unit 66 is used to set the first specific frequency Ftg1 corresponding to the battery temperature TB, the battery pressure PR, and the SOC acquired in steps S14 to S18.

[0041] In step S22, the AC signal of the first specific frequency Ftg1 set in step S20 is applied to the storage battery 40 to calculate the impedance Z of the storage battery 40. Note that in step S22, since an induced electromotive force Vid is generated in the storage battery 40 when the AC signal of the first specific frequency Ftg1 is applied to the storage battery 40, the impedance Z when the induced electromotive force Vid is generated is calculated, not the impedance ZB when the induced electromotive force Vid is not generated.

[0042] In step S24, an error ΔZ, which is the imaginary component ZI of the impedance Z calculated in step S22, is calculated. In the following step S26, an error parameter Σm, which is a value obtained by dividing the error ΔZ calculated in step S24 by a specific angular frequency ωm, which is an angular frequency corresponding to the first specific frequency Ftg1, is calculated, and the correction process ends. The calculated error parameter Σm is stored in the storage unit 66 of the control device 60. The specific angular frequency ωm and the error parameter Σm are expressed as the following (Equation 1) and (Equation 2). In this embodiment, the specific angular frequency ωm corresponds to a "specified angular frequency", and the error parameter Σm corresponds to an "impedance error".

[0043] ωm=2π×Ftg1 (Eq. 1) Σm=ΔZ / ωm (Equation 2) In this embodiment, in (Equation 2), the error ΔZ is the value of only the imaginary component ZI. If the calculated error parameter Σm is not included in a predetermined specified range, the error parameter Σm may be calculated again. In this embodiment, the process of step S24 corresponds to the "error calculation unit."

[0044] On the other hand, in step S10, if it is not the error calculation period TG, it is determined that it is the impedance calculation period TI, and an affirmative determination is made in step S10, and the process proceeds to step S28. In step S28, it is determined whether the vehicle is traveling. Whether the vehicle is traveling is determined using a vehicle speed sensor or the like (not shown). For example, while the vehicle is traveling, the impedance Z may be calculated to estimate the temperature of the storage battery 40. When the impedance Z is calculated while the vehicle is traveling, an affirmative determination is made in step S28, and in the subsequent step S30, the first and second switches SW1 and SW2 are closed, and the third and fourth switches SW3 and SW4 are opened.

[0045] Furthermore, for example, while the vehicle is stopped, the impedance Z may be calculated in order to calculate the SOC of the storage battery 40. When the impedance Z is calculated while the vehicle is stopped, a negative determination is made in step S28, and in the subsequent step S32, the first to fourth switches SW1 to SW4 are closed.

[0046] In step S34, a calculation frequency F0 for calculating the impedance Z of the storage battery 40 is set. Here, the calculation frequency F0 is set based on the running state of the vehicle and the operating state of the inverter 30. It is preferable that the calculation frequency F0 is a frequency that is as far away as possible from the frequency of vibrations caused by the running of the vehicle and the frequency of electrical signals caused by the operation of the inverter, and that satisfies the purpose of calculating the impedance Z.

[0047] In step S36, an AC signal having the calculated frequency F0 set in step S34 is applied to the storage battery 40 to calculate the impedance Z of the storage battery 40. In this embodiment, the process of step S36 corresponds to an "impedance calculation unit."

[0048] In step S38, the impedance Z calculated in step S36 is corrected based on the error parameter Σm calculated in step S24, and the correction process is terminated. Specifically, a correction value HV is calculated by multiplying the error parameter Σm by the calculated frequency ω0, which is the angular frequency corresponding to the calculated frequency F0. Then, the impedance Z calculated in step S36 is corrected by subtracting the correction value HV from the impedance Z calculated in step S36. The calculated frequency ω0 and the correction value HV are expressed as the following (Equation 3) and (Equation 4).

[0049] ω0=2π×F0 (Formula 3) HV=ω0×Σm···(Formula 4) In this embodiment, the process of step S38 corresponds to a "correction unit."

[0050] Next, an example of the correction process is shown in Fig. 4 to Fig. 6. Fig. 4 shows a simplified configuration diagram of the power supply system 10 in the error calculation period TG. In the error calculation period TG, the first and second switches SW1 and SW2 are open. In Fig. 4, for ease of understanding, the motor 20, the first and second connection terminals TC1 and TC2, the third and fourth switches SW3 and SW4, the control device 60, the temperature sensor 63, the pressure sensor 64, and the IG switch 65 are omitted.

[0051] During the error calculation period TG, when the current modulation circuit 50 applies an AC signal of the first specific frequency Ftg1 to the storage battery 40, an induced electromotive force Vid is generated in the storage battery 40. In this case, the impedance Z of the storage battery 40 calculated by the IV method is expressed as shown in the following (Equation 5) using the fluctuating voltage Vs detected by the voltage sensor 61 and the fluctuating current Im detected by the current sensor 62.

[0052] Z=(Vs+Vid) / Im=Vs / Im+Vid / Im...(Formula 5) In the right-hand side of the above (Equation 5), the first term represents the specific impedance ZB, and the second term represents the error ΔZ due to the induced electromotive force Vid.

[0053] Here, let us consider the error ΔZ. The induced electromotive force Vid that constitutes the error ΔZ is expressed by the following (Equation 6) according to Faraday's law.

[0054]

number

[0055]

number

[0056]

number

[0057]

number

[0058]

number

[0059]

number

[0060] Z = ZB-jωmΣm (Eq. 15) According to the above (Equation 15), the following can be understood. That is, when an AC signal of the first specific frequency Ftg1 is applied to the storage battery 40 during the error calculation period TG, the imaginary component ZI of the specific impedance ZB becomes zero. Therefore, if the imaginary component ZI of the calculated impedance Z is not zero, the error ΔZ, which is the imaginary component ZI, is divided by the specific angular frequency ωm to calculate the error parameter Σm.

[0061] As described above, the error parameter Σm does not vary with time t, and is a value determined by the shape of the first closed circuit LC1. In other words, if the shape of the first closed circuit LC1 is constant, the error parameter Σm has a constant value regardless of time t. Therefore, if the error parameter Σm can be calculated in the error calculation period TG, the induced electromotive force Vid generated by the first closed circuit LC1 can be corrected in the impedance calculation period TI different from the error calculation period TG using the error parameter Σm calculated in the error calculation period TG.

[0062] The phase of the impedance Z calculated during an impedance calculation period TI when the induced electromotive force Vid(LC2) generated by the second closed circuit LC2 is zero, such as during a stop period of the inverter 30 while the vehicle is stopped, is set to θ (β=θ). The phase of the specific impedance ZB is set to α (β=α). In this case, the real component ZR, imaginary component ZI, and phase θ of the impedance Z are expressed as the following (Equation 16) to (Equation 18) using the calculation frequency ω0 during the impedance calculation period TI.

[0063]

number

[0064] FIG. 6 shows the correspondence relationship between the logarithm of the calculated frequency F0 and the imaginary component ZI of the impedance Z. As shown in FIG. 6, the imaginary component ZI before correction, indicated by a white circle, is calculated to be smaller than the imaginary component ZI after correction, indicated by a black circle. Therefore, by using the error parameter Σm, the impedance Z can be corrected so that the imaginary component ZI of the impedance Z becomes larger. Also, as shown in (Equation 4) and (Equation 15) to (Equation 17), since the correction value HV is proportional to the calculated frequency ω0, that is, the calculated frequency F0, the difference between the imaginary component ZI after correction and the imaginary component ZI before correction becomes larger as the calculated frequency F0 becomes higher. Therefore, by using the error parameter Σm, the influence of the induced electromotive force Vid can be suppressed and the impedance Z can be calculated with high accuracy, particularly in the high frequency region of the calculated frequency F0.

[0065] According to the present embodiment described above in detail, the following effects can be obtained.

[0066] In this embodiment, during the error calculation period TG, an AC signal of a first specific frequency Ftg1 at which the imaginary component ZI of the specific impedance ZB of the storage battery 40 becomes zero is applied to the storage battery 40, and an error ΔZ is calculated using the AC signal and a response signal to the AC signal. In other words, if the imaginary component ZI of the impedance Z calculated by applying the AC signal of the first specific frequency Ftg1 is not zero, the imaginary component ZI can be calculated as the error ΔZ due to the induced electromotive force Vid. Then, when the impedance Z of the storage battery 40 is calculated during an impedance calculation period TI different from the error calculation period TG, the impedance Z of the storage battery 40 is corrected based on this error ΔZ. This makes it possible to accurately calculate the impedance Z of the storage battery 40 by suppressing the influence of the induced electromotive force Vid.

[0067] Specifically, when an induced electromotive force Vid that has an effect on a voltage fluctuation circuit including the storage battery 40 by an amount equal to or greater than a specified error is not generated, the real component ZR of the impedance Z calculated by applying an AC signal of a first specific frequency Ftg1, which is an ohmic frequency, to the storage battery 40 becomes an ohmic resistance RH, and the imaginary component ZI becomes zero. In this embodiment, when calculating the error ΔZ, an AC signal of the first specific frequency Ftg1 is applied to the storage battery 40. Therefore, if the imaginary component ZI of the calculated impedance Z is not zero, the imaginary component ZI can be calculated as the error ΔZ.

[0068] The first specific frequency Ftg1 varies depending on the battery temperature TB, the battery pressure PR, and the SOC of the storage battery 40. In this embodiment, battery parameters such as the battery temperature TB, the battery pressure PR, and the SOC of the storage battery 40 are acquired, and an AC signal of the first specific frequency Ftg1 corresponding to these battery parameters is applied to calculate the error ΔZ of the storage battery 40. Therefore, the influence of the variations in the battery temperature TB, the battery pressure PR, and the SOC of the storage battery 40 can be suppressed, and the impedance Z of the storage battery 40 can be calculated with high accuracy.

[0069] The error ΔZ is affected by the current flowing through the inverter 30, such as the influence of the smoothing capacitor constituting the inverter 30 and the stray capacitance of the switches constituting the inverter 30. Therefore, if the error ΔZ is calculated during the current-carrying period of the inverter 30 when the first and second switches SW1 and SW2 are closed, the calculation accuracy of the error ΔZ decreases. In this regard, in this embodiment, the error ΔZ is calculated during the open period of the first and second switches SW1 and SW2. This makes it possible to calculate the error ΔZ due to the induced electromotive force Vid caused by the AC signal for calculating the impedance Z while suppressing the influence of the current flowing through the inverter 30, and to accurately calculate the impedance Z of the storage battery 40.

[0070] Like the error ΔZ, the impedance Z is affected by the current flowing through the inverter 30. In this regard, in this embodiment, if the vehicle is stopped, the impedance Z is calculated during the open period of the first and second switches SW1, SW2. This makes it possible to calculate the impedance Z while suppressing the effects of noise and the like due to the current flowing through the inverter 30, and therefore makes it possible to accurately calculate the impedance Z of the storage battery 40.

[0071] Furthermore, if the vehicle is running, the impedance Z is calculated during the energizing period of the inverter 30 when the first and second switches SW1, SW2 are closed. This makes it possible to detect the error ΔZ in the energizing period of the inverter 30 after calculating the error ΔZ due to the induced electromotive force Vid caused by the AC signal for calculating the impedance Z, and to calculate the effect of the current flowing through the inverter 30.

[0072] (Modification of the first embodiment) The closed circuit LC is not limited to the closed circuit connected to the storage battery 40. For example, in the current modulation circuit 50 in Fig. 1, a detection circuit for detecting the fluctuating current Im, which is configured by the resistor 52 and the current detection amplifier 54, also serves as the closed circuit LC that generates the induced electromotive force Vid.

[0073] 7, when an external closed circuit LCX that is not connected to the storage battery 40 is present near the power supply system 10, the external closed circuit LCX also becomes a closed circuit LC that generates an induced electromotive force Vid. The external closed circuit LCX may be provided inside the vehicle or outside the vehicle. The induced electromotive force Vid(LCX) generated by the external closed circuit LCX when an AC signal of the first specific frequency Ftg1 is applied to the storage battery 40 is expressed as shown in (Equation 19) using the angular frequency ωx of the external current Ix(t) flowing through the external closed circuit LCX, the external current Ix(t), the error parameter Σx of the external closed circuit LCX, and the phase difference Δx between the fluctuating current Im(t) and the external current Ix(t).

[0074]

number

[0075]

number

[0076]

number

[0077] Second embodiment The second embodiment will be described below with reference to FIG. 8, focusing on the differences from the first embodiment.

[0078] The present embodiment differs from the first embodiment in that the error ΔZ and the impedance Z are calculated during power running of the motor 20 or during regenerative power generation in the control process.

[0079] A flowchart of the correction process of this embodiment is shown in Fig. 8. When the control process starts, first in step S40, it is determined whether the motor 20 is powered or generating regenerative power. For example, the control device 60 acquires the rotation speed of the motor 20 using a rotation angle sensor (not shown), and determines whether the motor 20 is powered or generating regenerative power based on this rotation speed.

[0080] When the motor 20 is powered or during regenerative power generation, a charging / discharging current of the storage battery 40 flows between the storage battery 40 and the motor 20. In this embodiment, an example is shown in which the error calculation period TG and the impedance calculation period TI are set when the motor 20 is powered or during regenerative power generation. If a positive determination is made in step S40, the process proceeds to step S10. On the other hand, if a negative determination is made in step S40, the control process ends.

[0081] In step S10, it is determined whether or not it is the impedance calculation period TI. If it is determined that it is the error calculation period TG and the determination in step S10 is negative, the first and second switches SW1 and SW2 are closed in step S42. That is, in this embodiment, during the closing period of the first and second switches SW1 and SW2, the error ΔZ is calculated using the charge / discharge current of the storage battery 40. In general, during the power running of the motor 20 or during regenerative power generation, the charger 80 is not connected to the first and second connection terminals TC1 and TC2. Therefore, in step S42, the third and fourth switches SW3 and SW4 are opened, and the process proceeds to step S14.

[0082] On the other hand, if it is determined that it is the impedance calculation period TI and the determination in step S10 is affirmative, the process proceeds to step S30. That is, in this embodiment, the first and second switches SW1 and SW2 are closed, and the impedance Z is calculated using the charge / discharge current of the storage battery 40 during the closed period of the first and second switches SW1 and SW2, and the third and fourth switches SW3 and SW4 are opened.

[0083] According to the present embodiment described above in detail, the following effects can be obtained.

[0084] The storage battery 40 inputs and outputs power to and from the motor 20 via the inverter 30. In this embodiment, the error ΔZ is calculated during the period when the first and second switches SW1, SW2 are closed. This makes it possible to calculate the error ΔZ by using the charge / discharge current of the storage battery 40 that flows between the storage battery 40 and the motor 20.

[0085] The impedance Z is affected by the current flowing through the inverter 30, and if the effect of the current differs from that at the time of calculating the error ΔZ, the accuracy of correcting the impedance Z based on the error ΔZ decreases. In this regard, in this embodiment, the inverter 30 is calculated during the closing period of the first and second switches SW1, SW2, as in the calculation of the error ΔZ. This makes it possible to calculate the impedance Z while suppressing the effect of the current flowing through the inverter 30, and therefore to calculate the impedance Z with high accuracy. Furthermore, according to this embodiment, the impedance Z can be calculated while the storage battery 40 is being charged and discharged.

[0086] Third embodiment The third embodiment will be described below with reference to FIG. 9, focusing on the differences from the first embodiment.

[0087] This embodiment differs from the first embodiment in that power is input to the storage battery 40 to cause the storage battery 40 to output a predetermined AC signal. As shown in Fig. 9, the power supply system 10 includes a transmitting device 67 instead of the current modulation circuit 50. The transmitting device 67 is connected in series to the current sensor 62 on the positive power supply path L1 side of the current sensor 62, and outputs a predetermined AC signal to the storage battery 40 in response to a command signal from the control device 60.

[0088] According to the present embodiment described above in detail, it is possible to obtain the same effects as those of the first embodiment.

[0089] (Fourth embodiment) The fourth embodiment will be described below with reference to FIGS. 10 and 11, focusing on the differences from the third embodiment.

[0090] This embodiment differs from the third embodiment in that a transmitting device 67 and a current sensor 62 are provided on the charger 80 side. As shown in Fig. 10, the transmitting device 67 and the current sensor 62 are connected in series between the charger 80 and the second connection terminal TC2 with the charger 80 connected to the first and second connection terminals TC1 and TC2. The transmitting device 67 outputs a predetermined AC signal to the storage battery 40 in response to an instruction signal from the control device 60, and the current sensor 62 detects the fluctuating current Im and inputs the detected fluctuating current Im to the control device 60.

[0091] A flowchart of the correction process of this embodiment is shown in Fig. 11. This embodiment differs from the third embodiment in that the error AZ and the impedance Z are calculated during the charging period of the storage battery 40 by the charger 80 in the control process.

[0092] When the control process starts, first, in step S50, it is determined whether or not it is a charging period for the storage battery 40 by the charger 80. For example, the control device 60 determines, based on the fluctuating current Im input from the current sensor 62, whether or not it is a charging period for the storage battery 40 by the charger 80.

[0093] During the charging period of the storage battery 40, a charging current for the storage battery 40 flows from the charger 80 to the storage battery 40. In this embodiment, an embodiment in which an error calculation period TG and an impedance calculation period TI are set during the charging period of the storage battery 40 is illustrated. If a positive determination is made in step S50, the process proceeds to step S10. On the other hand, if a negative determination is made in step S50, the control process ends.

[0094] In step S10, it is determined whether or not it is the impedance calculation period TI. If it is determined that it is the error calculation period TG and the determination in step S10 is negative, in step S52, the first and second switches SW1 and SW2 are opened, and the third and fourth switches SW3 and SW4 are closed, and the process proceeds to step S14. That is, in this embodiment, during the open period of the first and second switches SW1 and SW2, the error ΔZ is calculated using the charging current of the storage battery 40.

[0095] On the other hand, if it is determined that it is the impedance calculation period TI and an affirmative determination is made in step S10, the first and second switches SW1 and SW2 are opened and the third and fourth switches SW3 and SW4 are closed in step S54, and the process proceeds to step S34. That is, in this embodiment, the impedance Z is calculated using the charge / discharge current of the storage battery 40 while the first and second switches SW1 and SW2 are open.

[0096] According to the present embodiment described above in detail, the following effects can be obtained.

[0097] The storage battery 40 may input and output power to and from the motor 20 via the inverter 30, and may be chargeable by a charger 80 external to the power supply system 10. In this embodiment, the error ΔZ is calculated during the charging period of the storage battery 40 by the charger 80. This makes it possible to calculate the error ΔZ using the charging current of the storage battery 40 that flows from the charger 80 to the storage battery 40. Furthermore, during the charging period of the storage battery 40, the third and fourth switches SW3 and SW4 are closed and the first and second switches SW1 and SW2 are open. Therefore, it is possible to calculate the error ΔZ while suppressing the influence of the current flowing through the inverter 30, such as the influence of the smoothing capacitor that constitutes the inverter 30 and the stray capacitance of the switches that constitute the inverter 30.

[0098] The impedance Z is affected by the current flowing through the inverter 30. In this embodiment, the impedance Z is calculated while the first and second switches SW1, SW2 are open and while the third and fourth switches SW3, SW4 are closed. This makes it possible to calculate the impedance Z using the charging current of the storage battery 40 that flows from the charger 80 to the storage battery 40, and also makes it possible to calculate the impedance Z while suppressing the effects of noise and the like caused by this charging current leaking to the inverter 30.

[0099] Fifth embodiment The fifth embodiment will be described below with reference to FIG. 12, focusing on the differences from the first embodiment.

[0100] This embodiment differs from the first embodiment in that the error ΔZ is calculated by the charge control device 81 of the charger 80, not by the control device 60 of the power supply system 10. Hereinafter, a fourth embodiment will be described in which the battery management system according to the present invention is applied to a battery management system 100 that manages a storage battery 40 provided in a power supply system 10 of a vehicle.

[0101] As shown in FIG. 12, the battery management system 100 includes a charger 80, a management server 90 as an external device, a data analysis device 91, and a user interface 92.

[0102] The charger 80 is connected to the power supply system 10 to charge the storage battery 40 of the power supply system 10, and includes a charge control device 81 as an impedance calculation device, a constant current source 82, and a current sensor 83. Hereinafter, for the sake of distinction, the current sensor 62 will be referred to as a first current sensor 62, and the current sensor 83 will be referred to as a second current sensor 83.

[0103] The constant current source 82 is configured to be connectable to the first connection terminal TC1 and the second connection terminal TC2 of the power supply system 10 via the charging path L8, and flows a charging current to the storage battery 40 in response to a charging instruction from the charging control device 81, thereby charging the storage battery 40. The second current sensor 83 is connected in series to the constant current source 82 in the charging path L8, and detects the charging current. In this embodiment, a current sensor with higher accuracy than the first current sensor 62 of the power supply system 10 is used as the second current sensor 83.

[0104] The charging control device 81 includes a well-known microcomputer including a CPU, a ROM, a RAM, a flash memory, and the like. The charging control device 81 operates by receiving power from a constant current source 82, and realizes various functions for charging the storage battery 40 by referring to the arithmetic program and control data in the ROM. Specifically, the charging control device 81 outputs a charging instruction to the constant current source 82, and notifies the control device 60 of the power supply system 10 via the communication unit 84 that charging will start. Upon receiving the notification via the communication unit 68, the control device 60 opens the first and second switches SW1 and SW2, and closes the third and fourth switches SW3 and SW4.

[0105] The charging control device 81 also realizes various functions for managing the storage battery 40. Specifically, the charging control device 81 notifies the control device 60 of the calculation of the error ΔZ during the charging period of the storage battery 40 by the charger 80. Upon receiving the notification, the control device 60 inputs an instruction signal to the current modulation circuit 50 to generate a fluctuating current Im and a fluctuating voltage Vs based on the charging current. The control device 60 acquires the imaginary component of the fluctuating current Im using the first current sensor 62, and acquires the real component and the imaginary component of the fluctuating voltage Vs using the voltage sensor 61. The control device 60 transmits these acquired values ​​to the charging control device 81.

[0106] The charging control device 81 acquires the imaginary component of the fluctuating current Im and the real and imaginary components of the fluctuating voltage Vs from the control device 60. The charging control device 81 also acquires the real component of the fluctuating current Im using the second current sensor 83. Note that the first current sensor 62, the voltage sensor 61, and the second current sensor 83 can acquire the fluctuating voltage Vs and the fluctuating current Im in synchronization with each other by the synchronization process between the control device 60 and the charging control device 81 via the communication units 68 and 84. The charging control device 81 calculates the error ΔZ using these values, and corrects the impedance Z using the calculated error ΔZ. Note that the impedance Z used for the correction may be calculated during a charging period of the storage battery 40 that is different from the period during which the error ΔZ is calculated, or may be measured by the control device 60 and stored in the storage unit 66 before the charging period of the storage battery 40.

[0107] Then, the charging control device 81 transmits the battery information JD to the management server 90 via the communication unit 84. The battery information JD includes the error ΔZ and the corrected impedance Z, as well as identification information JS for identifying the storage battery 40 that calculated these values ​​and information specifying the time of calculation. As the identification information JS, the serial number of the storage battery 40 or the vehicle number (vehicle registration number) of the vehicle on which the power supply system 10 is mounted can be used.

[0108] The management server 90 is, for example, a data server, and stores the battery information JD transmitted from the charging control device 81. The management server 90 uses the identification information JS included in the battery information JD to associate the battery information JD with the identification information JS and stores it. Therefore, even if battery information JD for the same storage battery 40 is transmitted from different charging control devices 81, the battery information JD can be associated and stored using the identification information JS.

[0109] The data analysis device 91 analyzes the battery information JD stored in the management server 90 via the communication unit 93. Specifically, the data analysis device 91 analyzes the change in the corrected impedance Z for each storage battery 40, that is, for each vehicle, and analyzes the degree and rate of deterioration of the storage battery 40. This makes it possible to detect, for example, differences in the rate of deterioration of the storage battery 40 depending on the vehicle model.

[0110] The charging control device 81 also transmits the charging information JE to a user interface 92 via the communication unit 84. The user interface 92 is a mobile terminal of the vehicle owner, such as a smartphone or a tablet terminal. The charging information JE also includes information related to a state of charge (SOC) indicating the charge state of the storage battery 40, a charging time required to charge the storage battery 40, and a maximum amount of power that can be charged into the storage battery 40. These pieces of information are calculated by the charging control device 81 based on the calculated corrected impedance Z.

[0111] The vehicle owner can check the charging information JE via the user interface 92 and recognize the degree of deterioration of the storage battery 40, for example, based on the maximum amount of power that can be charged to the storage battery 40. The vehicle owner can also check the charging time of the storage battery 40, and if charging is not going to be completed in time, can instruct the charging control device 81 to increase the charging current. Furthermore, if charging is not going to be completed in time, the vehicle owner can instruct the charging control device 81 to stop charging midway. This allows the charging control device 81 to flexibly respond to changes in the vehicle owner's own schedule.

[0112] According to the present embodiment described above in detail, the following effects can be obtained.

[0113] In this embodiment, the error ΔZ is calculated by the charge control device 81 of the charger 80. Therefore, for multiple storage batteries 40 included in multiple power supply systems 10, the error ΔZ can be calculated using a common charge control device 81 included in the charger 80, and the impedance Z can be corrected.

[0114] In this embodiment, the management server 90 stores the battery information JD including the corrected impedance Z in association with the identification information JS of the storage battery 40. Therefore, even if a certain storage battery 40 is charged by different chargers 80, the battery information JD transmitted from these chargers 80 is associated with each other by the identification information JS in the management server 90. This allows the management server 90 to collectively manage the battery information JD for the same storage battery 40.

[0115] In this embodiment, the error ΔZ is calculated during the charging period of the storage battery 40 by the charger 80. By calculating the error ΔZ during the charging period, it is possible to calculate the error ΔZ even if the time required for the error ΔZ is long, and it is possible to ensure an opportunity to calculate the error ΔZ.

[0116] The on-board first current sensor 62 needs to maintain a wide current measurement range in order to detect the current flowing through the storage battery 40 while the vehicle is traveling, and it is difficult to improve the detection accuracy over the entire range. In this embodiment, a current sensor with higher accuracy than the first current sensor 62 of the power supply system 10 is used as the second current sensor 83 provided in the charger 80. Therefore, by acquiring the real component of the fluctuating current Im using the second current sensor 83, the error ΔZ can be calculated with high accuracy.

[0117] (Modification of the fifth embodiment) Instead of the current modulation circuit 50, the constant current source 82 of the charger 80 may be used to output a predetermined AC signal to the storage battery 40. In this case, the current modulation circuit 50 may be omitted. The constant current source 82 may be a constant voltage source that applies a constant voltage to the storage battery 40 in response to a charge instruction from the charge control device 81 to charge the storage battery 40.

[0118] (Other embodiments) Each of the above embodiments may be modified as follows.

[0119] The storage battery 40 is not limited to a lithium ion battery, but may be a lead storage battery or a nickel metal hydride battery.

[0120] In the above-mentioned embodiments, the storage battery 40 is configured by a battery cell assembly 41, but may be configured by a single cell. Also, as shown in FIG. 13, a plurality of storage batteries 40 may be connected in series. In this case, a voltage sensor 61 is provided for each storage battery 40, and detects the fluctuating voltage Vs of the corresponding storage battery 40. The control device 60 acquires the fluctuating voltage Vs from each voltage sensor 61. Also, the control device 60 acquires the battery temperature TB and the battery pressure PR from the temperature sensor 63 and the pressure sensor 64 provided in each storage battery 40, and calculates the impedance Z of each storage battery 40. As shown in FIG. 14, the same is true when the storage battery 40 is caused to output a predetermined AC signal by inputting power to the storage battery 40. As a result, not only the error ΔZ of each storage battery 40 but also the error ΔZ of the entire plurality of storage batteries 40 can be obtained.

[0121] 15, in the power supply system 10 including the current modulation circuit 50 and the current sensor 62, the current modulation circuit 50 and the current sensor 62 may also be provided for each storage battery 40. The current modulation circuit 50 applies an AC signal of a first specific frequency Ftg1 to the corresponding storage battery 40. At least one of the current modulation circuit 50 and the current sensor 62 detects the fluctuating current Im of the corresponding storage battery 40. The control device 60 acquires the fluctuating current Im from at least one of the current modulation circuit 50 and the current sensor 62 provided in each storage battery 40, and calculates the impedance Z of each storage battery 40.

[0122] The specified frequency is not limited to the first specific frequency Ftg1, i.e., the ohmic frequency, but may be a frequency γ at which at least one of the real component ZR and imaginary component ZI of the impedance Z of the storage battery 40 becomes a specified value. In this case, the error ΔZ may occur not only in the imaginary component ZI but also in the real component ZR. When the error ΔZ occurs in the imaginary component ZI and the real component ZR, the error parameter Σm and the frequency γ can be obtained by using simultaneous equations of an equation corresponding to the error in the imaginary component ZI and an equation corresponding to the error in the real component ZR.

[0123] In the first embodiment, the impedance calculation period TI can be any period other than the error calculation period TG, whether the vehicle is running or stopped, but the present invention is not limited to this, and the impedance calculation period TI may be only a period when the vehicle is stopped. This allows the impedance Z to be calculated with the first and second switches SW1 and SW2 in a closed state, and allows the impedance Z of the storage battery 40 to be calculated with high accuracy in a low-noise environment.

[0124] In the first embodiment, the error calculation period TG is the period during which the storage battery 40 is charged by the charger 80, but this is not limited to this. For example, the error calculation period TG may be a predetermined inspection period when the storage battery 40 is shipped from a factory.

[0125] Moreover, the error calculation period TG may be a predetermined inspection period during maintenance of a vehicle equipped with the storage battery 40. In these error calculation periods TG, an AC signal of the first specific frequency Ftg1 is applied from an external power supply to the storage battery 40 before it is installed in the vehicle or while it is installed in the vehicle, and the error ΔZ is calculated.

[0126] Also, the period during which the IG switch 65 is switched to the open state may be set as the error calculation period TG, and the period during which the IG switch 65 is switched to the closed state may be set as the impedance calculation period TI. Furthermore, the stop period of the inverter 30 may be set as the error calculation period TG, and the operation period of the inverter 30 may be set as the impedance calculation period TI.

[0127] In the first embodiment, the first specific frequency Ftg1, which is an ohmic frequency, is exemplified as the specified frequency, but the specified frequency is not limited to this. The specified frequency may be any frequency at which it is known that the imaginary component ZI of the specific impedance ZB of the storage battery 40 is a specified value. In this case, the error ΔZ can be calculated from the imaginary component ZI of the impedance Z by using the imaginary component ZI of the specific impedance ZB and a correction formula.

[0128] In the above-described first embodiment, the battery temperature TB, the battery pressure PR, and the SOC are acquired as battery parameters, but the present invention is not limited to this. At least one of the battery parameters, the battery temperature TB, the battery pressure PR, and the SOC, may be acquired.

[0129] In the above embodiment, an example was described in which the power supply system 10 was provided with one storage battery 40. However, this is not limited to this, and the power supply system 10 may be provided with a plurality of storage batteries 40 connected in series or in parallel.

[0130] In the above embodiment, an example was shown in which the error ΔZ is calculated by the control device 60 of the power supply system 10 and the charge control device 81 of the charger 80, but this is not limited to the above, and the error ΔZ may be calculated by a dedicated device for calculating the error ΔZ.

[0131] The control device 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 device 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 device 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 the computer. [Explanation of symbols]

[0132] 10...power supply system, 40...storage battery, 60...control device, Ftg1...first specific frequency, Z...impedance.

Claims

1. An impedance calculation device (60) that is applied to a power supply system (10) including a storage battery (40) and calculates an impedance (Z) of the storage battery by applying an AC signal to the storage battery by a signal application unit (50, 67) during a predetermined impedance calculation period, an error calculation unit that applies the AC signal having a specified frequency (Ftg1) at which at least one of a real component and an imaginary component of the impedance of the storage battery becomes a specified value during an error calculation period different from the impedance calculation period, and calculates an impedance error of the storage battery; an impedance calculation unit that calculates an impedance of the storage battery during the impedance calculation period; a correction unit that corrects the impedance of the storage battery calculated by the impedance calculation unit based on the impedance error, an impedance calculation device, wherein the calculation of the impedance error by the error calculation unit and the calculation of the impedance by the impedance calculation unit are performed using the same closed circuit including the storage battery and the signal application unit while the closed circuit is energized.

2. The specified frequency is an ohmic frequency (Ftg1) for calculating the ohmic resistance (RH) of the storage battery, The error calculation unit calculates, as the impedance error, an error parameter (Σm) which is a value obtained by dividing an imaginary component of the impedance of the storage battery calculated by applying the AC signal of the ohmic frequency by a specified angular frequency corresponding to the specified frequency; The impedance calculation device according to claim 1 , wherein the correction unit corrects the impedance of the storage battery calculated by the impedance calculation unit based on the error parameter.

3. The storage battery is an on-board storage battery mounted on a vehicle, The impedance calculation device according to claim 1 , wherein the error calculation unit calculates the impedance error of the storage battery when the storage battery is not mounted on the vehicle.

4. The storage battery is an on-board storage battery mounted on a vehicle, The impedance calculation unit calculates an impedance of the storage battery while the vehicle is stopped, The impedance calculation device according to claim 1 , wherein the correction unit corrects the impedance of the storage battery calculated by the impedance calculation unit based on the impedance error while the vehicle is stopped.

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