Battery monitoring system and method and transportation system having the battery monitoring system

Abstract

The waveform designator (53) designates a given waveform of the AC signal by using a specific frequency as a reference. The signal controller (56) causes the storage battery (42) to output a response signal based on its own power. The detector detects a frequency component in the response signal corresponding to the reference frequency of the AC signal based on the product of the reference frequency and the response signal. The calculator calculates the complex impedance of the storage battery based on the frequency component in the response signal. The noise determiner (53) determines whether there is a noise signal corresponding to the reference frequency of the AC signal before the signal controller causes the storage battery to output the AC signal. The noise controller (53) avoids or eliminates the noise signal.

Description

Technical Field

[0001] The present disclosure relates to a battery monitoring system and method and a transportation system having the battery monitoring system. Background Art

[0002] Conventionally, in order to monitor the state of a battery, the complex impedance of the battery is measured. That is, the power controller applies a rectangular wave signal to the battery and calculates the complex impedance characteristics based on the response signal returned from the battery. Then, the degradation state of the battery is determined based on the complex impedance characteristics.

[0003] However, when the complex impedance of a battery mounted on a vehicle is measured using this complex impedance measurement method, there are problems as described below: That is, since the vehicle includes many noise sources such as inverters, the detection of the complex impedance is generally inaccurate. Summary of the invention

[0004] Therefore, the present disclosure is made to solve the above-mentioned problems, and its purpose is to provide an improved battery monitoring system that can accurately detect complex impedance. According to one aspect of the present disclosure, a new battery monitoring system (50) for monitoring the state of a storage battery (42) including an electrolyte and a plurality of electrodes includes a waveform designator (i.e., the function of the above-mentioned microcomputer (53)), and the above-mentioned waveform designator specifies a prescribed waveform (and frequency) of an AC signal by specifying at least one frequency as a reference. The battery monitoring system also includes a signal controller (i.e., the function of a current modulation circuit (56)), and the above-mentioned signal controller causes the storage battery (42) to output an AC signal as a response signal based on its own power. The battery monitoring system also includes a response signal input unit (i.e., the function of a lock-in amplifier (52)), and the above-mentioned response signal input unit receives an AC signal from the storage battery as a response signal. The battery monitoring system further includes a frequency component detector (i.e., a function of a lock-in amplifier (52)), which detects an AC signal having a frequency component corresponding to the frequency of the AC signal in the response signal based on the product of a reference signal and a response signal received as an input of a response signal input unit (i.e., a function of the lock-in amplifier (52)). The battery monitoring system further includes a calculator (i.e., a function of the microcomputer (53)), which calculates the complex impedance of the storage battery based on the frequency component of the AC signal detected by the detector in the response signal. The battery monitoring system further includes a noise determiner (i.e., a function of the microcomputer (53)), which determines whether there is a noise signal having a frequency corresponding to the reference frequency of the AC signal before the signal controller causes the storage battery to output the AC signal. The battery monitoring system further includes a noise controller (i.e., a function of the microcomputer (53)), which avoids or removes the noise signal when the noise determiner recognizes that there is a noise signal.

[0005] Therefore, according to one aspect of the present disclosure, the signal controller outputs a prescribed AC signal based on the power supplied by the battery as the monitoring target. Therefore, when the AC signal is input to the battery, no additional power supply is required, thereby reducing the number of components and correspondingly miniaturizing the system at a low cost.

[0006] In addition, since peripheral circuits such as a protection element, a filter circuit, etc. are generally connected to a battery mounted on a vehicle, the current of the AC signal input to the battery partially leaks to the peripheral circuits. Therefore, when the complex impedance is calculated based on a response signal generated in response to the input of the AC signal to the battery, an error is generated in the response signal, thereby deteriorating the detection accuracy of the complex impedance.

[0007] However, according to the configuration described above of the first aspect of the present disclosure, since a prescribed AC signal is output based on the power supplied by the battery, a closed loop can be formed by the signal controller and the battery. Therefore, current leakage from the battery can be substantially eliminated, thereby reducing or suppressing errors.

[0008] Furthermore, by the configuration as described above, the detector detects the frequency component in the response signal corresponding to the frequency of the AC signal. Subsequently, the calculator calculates the complex impedance based on the frequency component in the response signal detected by the detector. Therefore, the complex impedance can be calculated with high accuracy while avoiding the influence of noise signals such as white noise. In particular, even if many noise signals are easily generated in the vehicle battery, the complex impedance of the vehicle battery can be accurately calculated.

[0009] In addition, as described above, the frequency component corresponding to the frequency of the AC signal in the response signal is detected. However, when there is a noise signal having the same frequency as the AC signal, especially having the same phase as the AC signal (in the response signal), such a noise signal is also detected, and an error may occur. In particular, since various devices such as an inverter device in a vehicle operate at various driving frequencies, it is likely that a noise signal as described above with a given frequency is generated and output. However, the influence of the noise signal having the same frequency as the AC signal can be suppressed, so that the complex impedance can be accurately detected even if the noise signal exists.

[0010] Another aspect of the present disclosure provides a novel transportation system having a battery monitoring system (50) for monitoring the state of a storage battery (42) including an electrolyte and a plurality of electrodes. The battery monitoring system further includes a waveform designator (i.e., a function of the microcomputer (53)), which specifies a given waveform of an AC signal by specifying a frequency that specifically belongs to a given measurable range. The battery monitoring system further includes a storage unit (i.e., a function of the microcomputer (53)), which stores the given measurable frequency. The battery monitoring system further includes a signal controller (i.e., a function of a current modulation circuit (56)), which causes the storage battery to output an AC signal as a response signal based on its own power as a monitoring target. The battery monitoring system further includes a response signal input unit (i.e., a function of a lock-in amplifier (52)), which receives a response signal from the storage battery (42). The battery monitoring system further includes a frequency component detector (i.e., a function of a lock-in amplifier (52)) that detects an AC signal having a frequency component corresponding to a reference frequency of the AC signal in the response signal. The frequency component detector (i.e., a function of the lock-in amplifier (52)) detects the AC signal having the frequency component based on the product of the reference frequency and the response signal input to the response signal input unit. The battery monitoring system further includes a calculator (i.e., a function of the microcomputer (53)) that calculates the complex impedance of the storage battery (42) based on the frequency component in the response signal detected by the detector. The given frequency excludes the frequency of a noise signal output from a noise generating source installed on the transportation system or a noise source connected to the transportation system.

[0011] In addition, another aspect of the present disclosure provides a novel battery monitoring method for monitoring the state of a storage battery (42). The monitoring method includes the following steps: specifying a specified waveform and frequency of an AC signal by specifying a frequency as a reference; determining whether there is a noise signal having a frequency corresponding to the reference frequency of the AC signal; and avoiding or removing the noise signal when it is determined that the noise signal exists. The battery monitoring method also includes the following steps: causing the storage battery (42) to output an AC signal as a response signal based on its own power; receiving a response signal from the storage battery (42); and detecting an AC signal having a frequency component corresponding to the reference frequency in the response signal based on the product of the reference frequency and the response signal. The battery monitoring method also includes the step of calculating the complex impedance of the storage battery based on the frequency component of the AC signal as the response signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Thus, a more complete appreciation of the present disclosure and many of its attendant advantages may be more readily obtained by reference to the following detailed description, so that substantially the same may be better understood when considered in conjunction with the accompanying drawings, wherein:

[0013] Figure 1 is a schematic diagram showing a power supply system according to a first embodiment of the present disclosure;

[0014] Figure 2 is a diagram showing a configuration of a battery monitoring system according to a first embodiment of the present disclosure;

[0015] Figure 3 is a flowchart showing an impedance calculation process according to a first embodiment of the present disclosure;

[0016] Figure 4 is a flowchart showing a response signal detection process according to the first embodiment of the present disclosure;

[0017] Figure 5 is a flowchart showing a noise signal detection process according to the first embodiment of the present disclosure;

[0018] Fig. 6A and Figure 6B is a diagram showing a connection position according to a first embodiment of the present disclosure;

[0019] Figure 7 is a flowchart showing an impedance calculation process according to a second embodiment of the present disclosure;

[0020] Figure 8 is a flowchart showing an impedance calculation process according to a third embodiment of the present disclosure;

[0021] Fig. 9 is a flowchart showing an impedance calculation process according to a fourth embodiment of the present disclosure;

[0022] Fig.10 is a flowchart showing an impedance calculation process according to a fifth embodiment of the present disclosure;

[0023] Fig.11 is a diagram showing a configuration of a battery monitoring system according to a sixth embodiment of the present disclosure;

[0024] Fig.12 is a flowchart showing a response signal detection process according to a sixth embodiment of the present disclosure; and

[0025] Fig.13 is a diagram showing a configuration of a battery monitoring system according to still another embodiment of the present disclosure. DETAILED DESCRIPTION

[0026] Conventionally, in order to monitor the state of a storage battery, the complex impedance of the storage battery is measured as discussed in Japanese Patent No. 6226261 (JP6226261B2). That is, JP6226261B2 describes that a power controller applies a rectangular wave signal to a storage battery and calculates a complex impedance characteristic based on a response signal returned from the storage battery. Subsequently, the deterioration state of the storage battery or the like is determined based on the complex impedance characteristic.

[0027] However, when such a complex impedance measurement method is used to measure the complex impedance of a battery mounted on a vehicle, there arises a problem as described below: That is, since the vehicle includes many noise sources such as an inverter, the detection of the complex impedance is generally inaccurate.

[0028] Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views thereof, and reference Figure 1 (First embodiment) will be described.

[0029] That is, as shown below, except Figure 1 The battery monitoring system as the first embodiment described in the other drawings is used in a power supply system mounted on a vehicle (eg, a hybrid vehicle, an electric vehicle).

[0030] Specifically, Figure 1 As shown, the power supply system 10 includes: a motor 20 as a rotating electric machine; an inverter 30 as a power converter for allowing a three-phase current to flow into the motor 20; and a battery pack 40 that can be charged and discharged. The power supply system 10 also includes: a battery monitoring system 50 for monitoring the state of the battery pack 40; and an ECU (engine control unit) 60 for controlling the motor 20 and the like.

[0031] The electric motor 20 is a vehicle-mounted main unit capable of transmitting power to driving wheels (not shown). In the present embodiment, as the electric motor 20, a three-phase permanent magnet synchronous motor is used.

[0032] The inverter 30 includes a full-bridge circuit having the same number of upper arms and lower arms as the number of phases of the phase windings, so as to adjust the current flowing through each phase winding by turning on or off a switch (for example, a semiconductor switching element such as an IGBT (insulated gate bipolar transistor)) provided in each of the upper arms and the lower arms.

[0033] The inverter 30 has an inverter control device (not shown) that performs power-on control by turning on or off each switch provided in the inverter 30 based on various detection information generated in the motor 20 and the demand for power running drive and power generation. Thus, the inverter control device supplies power from the assembled battery 40 to the motor 20 via the inverter 30, so that the motor 20 performs power running drive. In addition, the inverter control device causes the motor 20 to generate power based on the power transmitted from the driving wheels, and converts the generated power and supplies the converted power to the assembled battery 40 to charge the assembled battery 40.

[0034] In addition, the assembled battery 40 is electrically connected to the motor 20 via the inverter 30. For example, the assembled battery 40 has a terminal voltage of about 100V or more. The assembled battery 40 includes a plurality of battery modules 41 connected in series with each other. Each of the battery modules 41 includes a plurality of battery cells 42 connected in series with each other. As the battery cells 42, for example, lithium-ion batteries and nickel metal hydride batteries can be used. Each battery cell 42 includes an electrolyte and a plurality of electrodes.

[0035] Furthermore, the positive electrode side power supply path L1 is connected at one end thereof to the positive electrode side power supply terminal of the assembled battery 40, and at the other end thereof to the positive electrode side terminal of an electric load such as the inverter 30. Similarly, the negative electrode side power supply path L2 is connected at one end thereof to the negative electrode side power supply terminal of the assembled battery 40, and at the other end thereof to the negative electrode side terminal of an electric load such as the inverter 30. Furthermore, a relay switch SMR (e.g., a system main relay switch) is provided in each of the positive electrode side power supply path L1 and the negative electrode side power supply path L2 to switch the circuit between a power-on state and a power-off state.

[0036] In addition, the battery monitoring system 50 monitors the power storage state (i.e., SOC (State of Charge)) and the degradation state (i.e., SOH (State of Health)) of each battery cell 42. In the first embodiment, the battery monitoring system 50 is provided for each battery cell 42. The battery monitoring system 50 is connected to the ECU (Engine Control Unit) 60 to output data of such states of the battery cell 42 to the ECU 60. The details of the configuration of the battery monitoring system 50 will be described later.

[0037] The ECU 60 sends data indicating a request for power running driving and power generation to the inverter control device based on various information, such as operation information of the accelerator and the brake, the vehicle speed, and the state of the assembled battery 40.

[0038] Now, refer to Figure 2The battery monitoring system 50 is described in more detail below. As described above, in the first embodiment, the battery monitoring system 50 is provided for each battery unit 42 .

[0039] Specifically, the battery monitoring system 50 includes an ASIC (Application Specific Integrated Circuit) unit 50a, a filter unit 55, and a current modulation circuit 56. The ASIC unit 50a includes a stabilized power supply unit 51, a lock-in amplifier 52, and a microcomputer 53 as a calculator. The ASIC unit 50a also includes a communication unit 54 and a voltage measurement unit 57.

[0040] The stable power supply unit 51 is connected to the power line extending to the battery unit 42 to supply the power supplied from the battery unit 42 to the lock-in amplifier 52, the microcomputer 53, and the communication unit 54 (as shown by the dotted arrow). The stable power supply unit 51 also supplies power to the voltage measuring unit 57 (as shown by the dotted arrow). Therefore, the lock-in amplifier 52, the microcomputer 53, and the communication unit 54 are driven based on the power. The voltage measuring unit 57 is also driven based on the power.

[0041] In addition, for example, the voltage measuring unit 57 includes a differential amplifier and is connected to the battery cell 42 used as a monitoring target. Specifically, the voltage measuring unit 57 has a group of DC voltage input terminals 57a, 57b capable of receiving and measuring the DC voltage from the battery cell 42. In addition, the filter unit 55 is arranged between the battery cell 42 and the group of DC voltage input terminals 57a, 57b. More specifically, an RC filter 55a used as a filter circuit and a Zener diode 55b used as a protection element are arranged between the DC voltage input terminal 57a on the positive electrode side and the DC voltage input terminal 57b on the negative electrode side. That is, each of the RC filter 55a and the Zener diode 55b is connected in parallel with the battery cell 42.

[0042] In addition, the voltage measuring unit 57 is connected to the microcomputer 53 to output a DC voltage to the microcomputer 53 when receiving an input of the DC voltage. In addition, the voltage measuring unit 57 is connected to an AD converter (not shown) to convert an analog signal input to the AD converter into a digital signal and output the conversion result to the microcomputer 53.

[0043] Similarly, the lock-in amplifier 52 is also connected to the battery cell 42 as the monitoring target. The lock-in amplifier 52 has a set of response signal input terminals 58 for receiving an input of a response signal (i.e., a voltage change) reflecting the internal complex impedance (information) of the battery cell 42 between the terminals of the battery cell 42. Therefore, according to one embodiment of the present disclosure, the lock-in amplifier 52 is used as a response signal receiver.

[0044] In addition, the lock-in amplifier 52 is also connected to a current modulation circuit 56 used as a signal controller. Specifically, the lock-in amplifier 52 has an indication signal output terminal 59a for outputting an indication signal to the current modulation circuit 56. The indication signal instructs the battery cell 42 to output a sine wave signal (i.e., an AC signal). In addition, the lock-in amplifier 52 also has a feedback signal input terminal 59b. That is, the feedback signal input terminal 59b receives a current signal actually output from the battery cell 42 (i.e., flowing through the battery cell 42) as a feedback signal via the current modulation circuit 56.

[0045] Furthermore, the lock-in amplifier 52 is also connected to the microcomputer 53. Specifically, the lock-in amplifier 52 outputs the response signal received via the response signal input terminal 58 and the feedback signal received via the feedback signal input terminal 59b to the microcomputer 53. Furthermore, the lock-in amplifier 52 has an AD converter therein to convert an analog signal as an input into a digital signal and outputs such a conversion result to the microcomputer 53.

[0046] In addition, the lock-in amplifier 52 is capable of receiving a signal from the microcomputer 53. The lock-in amplifier 52 is also capable of outputting an indication signal to the current modulation circuit 56 via the indication signal output terminal 59a based on an instruction sent from the microcomputer 53. In addition, the lock-in amplifier 52 also has a DA converter therein to convert a digital signal into an analog signal, and outputs the analog signal as an indication signal to the current modulation circuit 56. In addition, a DC bias is applied to the sine wave signal output to the current modulation circuit 56 as an instruction so that the sine wave signal does not become a negative current (i.e., a reflux relative to the battery cell 42). In addition, the current modulation circuit 56 causes the battery cell 42 to output a prescribed AC signal (i.e., a sine wave signal) based on the power supplied by the battery cell 42 as a monitoring target. Specifically, the current modulation circuit 56 has: a semiconductor switching element 56a (e.g., a MOSFET (metal oxide semiconductor field effect transistor)) as a switching unit; and a resistor 56b connected in series to the semiconductor switching element 56a. In addition, the drain terminal of the semiconductor switching element 56a is connected to the positive electrode terminal of the battery cell 42. 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 electrode terminal of the battery cell 42. In addition, the semiconductor switch element 56a is capable of adjusting the amount of conduction (i.e., the amount of current flowing between the drain terminal and the source terminal). In addition, in order to adjust the voltage applied to the semiconductor switch element 56a according to the operating area of ​​the semiconductor switch element 56a, a resistor is sometimes inserted in series in the current modulation circuit 56.

[0047] Here, the positive electrode terminal and the negative electrode terminal of the battery cell 42 are connected to their corresponding electrodes (i.e., the positive electrode and the negative electrode). In addition, the group of response signal input terminals 58 is desirably connected to the positions closest to the positive electrode and the negative electrode of the battery cell 42. That is, the positive electrode terminal and the negative electrode terminal are desirably closest to the corresponding electrodes of the battery cell 42. Similarly, the connection portions of the group of DC voltage input terminals 57a, 57b are desirably located closest to the electrodes. In addition, when the response signal input terminal is located at the nearest position, these connection portions are located next to the corresponding connection portions of the response signal input terminal 58. Thereby, the influence of the voltage drop caused by the main current or the balancing current can be substantially minimized.

[0048] In addition, a current detection amplifier 56c is provided as a current detector in the current modulation circuit 56 and is connected to both ends of the resistor 56b. The current detection amplifier 56c detects a signal (i.e., a current signal) input via the resistor 56b and outputs this detection signal to the feedback signal input terminal 59b of the lock-in amplifier 52 as a feedback signal.

[0049] In addition, a feedback circuit 56d is also provided in the current modulation circuit 56. The feedback circuit 56d receives an input of an indication signal from the indication signal output terminal 59a of the lock-in amplifier 52. The feedback circuit 56d also receives an input of a feedback signal from the current detection amplifier 56c. Subsequently, the feedback circuit 56d compares the indication signal with the feedback signal and outputs the comparison result to the gate terminal of the semiconductor switch element 56a.

[0050] In addition, the semiconductor switch element 56a adjusts the voltage applied between the gate and the source and the amount of current flowing between the drain and the source based on the signal sent from the feedback circuit 56d, so that the battery cell 42 outputs the sine wave signal (prescribed AC signal) indicated by the indication signal. Therefore, if there is an error between the waveform indicated by the indication signal and the current waveform actually flowing through the resistor 56b, the semiconductor switch element 56a adjusts the amount of current based on the signal sent from the feedback circuit 56d to correct the error. As a result, the sine wave signal of the current flowing through the resistor 56b becomes stable.

[0051] Now, sometimes a method for calculating the complex impedance of the battery cell 42 will be described with reference to applicable drawings. Typically, in order to calculate the complex impedance of the battery, an AC signal (i.e., a current signal) is input to (i.e., a signal current flows through) the battery to obtain a voltage change generated in the battery. Subsequently, the complex impedance is calculated based on the AC signal and the voltage change. However, with the battery cell 42 as described above mounted on the vehicle, since peripheral circuits such as protection elements (e.g., Zener diodes 55b), filter circuits (e.g., RC filters 55a) are generally connected to the battery cell 42, the current of the AC signal to be input to the battery cell 42 partially leaks to the peripheral circuit. Therefore, the voltage change cannot be accurately received as an input. In addition, the battery cell 42 of the vehicle can be affected by many noise signals generated therein. For example, white noise (signal) and resonance with a given frequency generated by the drive frequency of the inverter 30 are exemplified.

[0052] Therefore, according to the present embodiment, in order to solve the above-mentioned problem, the complex impedance is calculated in a manner which will be described in detail below.

[0053] Specifically, the microcomputer 53 of the battery monitoring system 50 periodically executes the following Figure 3 The impedance calculation process shown. In the impedance calculation process, in step S101, the microcomputer 53 first specifies a measurement frequency for measuring the complex impedance (of the battery cell 52) (by specifying a given waveform of the AC signal output by the battery cell 52). The measurement frequency is specified according to the type of the battery cell 42. For example, when the battery cell 42 adopts a lithium-ion battery, the frequency is selected from the practically measurable range of about several MHz to about several kHz to effectively measure its complex impedance. Therefore, through this process, the microcomputer 53 corresponds to a waveform commander according to one embodiment of the present disclosure.

[0054] Subsequently, in step S102, the microcomputer 53 determines whether the measured frequency is within a given range. Here, the specified frequency range represents a range (noise range) in which a noise signal with a constant frequency is likely to be generated. For example, the noise signal caused by the inverter 30 as a noise source has a frequency substantially the same as the driving frequency of the inverter 30, or has a higher harmonic component of the driving frequency. The noise signal may also include a resonant frequency caused by an L (inductance) component and a C (capacitance) component, and the L (inductance) component and the C (capacitance) component include the parasitic inductance and parasitic capacitance of the inverter 30, respectively. The noise signal may also include higher harmonics of the resonant frequency. Therefore, it is possible to predict a frequency range in which a noise signal with a constant frequency is likely to be generated. In view of this, a specified frequency range is determined based on the driving frequency of a noise source such as the inverter 30 or an experimental result. That is, a specified frequency range in which a noise signal with a constant frequency is likely to be generated is determined based on the frequency of the noise signal output from the noise source, and the specified frequency range is stored in the microcomputer 53 used as a storage unit.

[0055] Furthermore, if the determination performed in step S102 is negative (NO in step S102), then in step S103, microcomputer 53 notifies lock-in amplifier 52 of the measurement frequency and instructs lock-in amplifier 52 to detect a frequency component of the measurement frequency in the response signal.

[0056] More specifically, in step S103, the microcomputer 53 determines the frequency of the sine wave signal (i.e., the prescribed AC signal) based on the measured frequency. Then, the microcomputer 53 outputs an instruction signal for instructing the output of the sine wave signal to the lock-in amplifier 52, so that the lock-in amplifier 52 performs the so-called lock detection for detecting the response signal. Now, the following will refer to Figure 4 The response signal detection process performed by the lock-in amplifier 52 is described in detail.

[0057] That is, in step S201, upon receiving the input of the instruction signal from the microcomputer 53, the lock-in amplifier 52 causes the battery cell 42 to output a sine wave signal to the battery cell 42 based on the instruction signal, based on the power supplied from the battery cell 42. Specifically, the lock-in amplifier 52 converts the sine wave signal represented by the input instruction signal into an analog signal by using a DA converter, and outputs this conversion result to the current modulation circuit 56. Thus, based on the power supplied by the battery cell 42, the current modulation circuit 56 causes the battery cell 42 to output a sine wave signal based on the instruction signal. More specifically, the semiconductor switch element 56a adjusts the amount of current based on the signal input to itself via the feedback circuit 56d, so that the battery cell 42 outputs a sine wave signal represented by the instruction signal. Thus, interference is applied to the battery cell 42, and a sine wave signal is output from the battery cell 42.

[0058] Therefore, when the battery cell 42 is forced to output a sine wave signal therefrom, a voltage change that reflects the internal complex impedance of the battery cell 42 occurs between the terminals of the battery cell 42. Therefore, in step S202, the lock-in amplifier 52 receives an input of the voltage change as a response signal via the response signal input terminal 58. At this time, the AD converter converts the voltage change into a digital signal.

[0059] Subsequently, the lock-in amplifier 52 multiplies the reference signal determined according to the sinusoidal signal to be output (from the battery cell 42) by the response signal as its input. The reference signal may be, for example, the measurement frequency as described above. Then, in step S203, the lock-in amplifier 52 performs a lock detection based on the value obtained by the product as described above, and the lock detection detects (i.e., extracts) the frequency component (i.e., the DC component as the detection target) in the frequency (i.e., the measurement frequency) of the sinusoidal signal as the response signal. Specifically, the frequency component (i.e., the DC component as the target) is detected by using a low-pass filter. Here, the sinusoidal signal represented by the indication signal to be output is used as a reference signal. However, the reference signal may be a signal (i.e., a feedback signal) that actually flows through the resistor 56b.

[0060] Then, in step S204, the lock-in amplifier 52 outputs the frequency component extracted from the response signal to the microcomputer 53. Thus, the lock-in detection of detecting the response signal is terminated.

[0061] In the following, we refer again to Figure 3 The impedance calculation process will be described.

[0062] When the microcomputer 53 receives the input of the frequency component in the response signal sent from the lock-in amplifier 52 after the processing in step S103 is completed, the processing proceeds to step S104. In step S104, the microcomputer 53 calculates all or any of the real part, imaginary part, absolute value and phase of the complex impedance based on the frequency component in the response signal input thereto and the current signal output from the battery cell 42. That is, the current signal can be obtained based on the feedback signal or the sine wave signal outputted by the indication signal. In addition, the current signal can be obtained by performing a lock-in detection for detecting the measurement frequency component in the feedback signal.

[0063] Subsequently, in step S105, the microcomputer 53 outputs the calculated complex impedance to the ECU 60 via the communication unit 54. Thus, the impedance calculation process is terminated.

[0064] Now, the processing performed when the judgment performed in step S102 is affirmative will be described below. That is, the processing performed when the measurement frequency falls within the prescribed frequency range and thus a noise signal with a constant frequency is likely to occur will be described. Specifically, when the judgment performed in step S102 is affirmative, in step S106, the microcomputer 53 instructs the lock-in amplifier 52 to detect the noise signal (i.e., background noise).

[0065] Therefore, in step S106, if the reference Figure 5 As described in detail, when no disturbance is applied to the battery cell 42, the microcomputer 53 causes the lock-in amplifier 52 to perform lock detection for detecting a noise signal (ie, background noise). Figure 5 As described above, the noise signal detection process is performed by the lock-in amplifier 52 .

[0066] Specifically, in step S301, when detection of a noise signal (e.g., background noise) is instructed, the lock-in amplifier 52 receives an input of a voltage change caused in the battery cell 42 as a noise signal via the response signal input terminal 58. That is, during a normal state in which no interference is applied to the battery cell 42, the lock-in amplifier 52 receives an input of a voltage change caused in the battery cell 42. At this time, the lock-in amplifier 52 receives an input of a voltage change as a digital signal converted from an analog signal by the AD converter.

[0067] Then, the lock-in amplifier 52 multiplies the reference signal corresponding to the sine wave signal output from the storage battery (42) by the noise signal as input. Then, in step S302, the lock-in amplifier 52 performs lock detection based on the value obtained by this multiplication to extract the sine wave signal having a frequency component (i.e., a DC component) corresponding to the measurement frequency.

[0068] Here, in step S302, the lock detection may be repeated as many times as needed, and the average value obtained thereby may be calculated. In addition, when AD conversion is performed, the noise signal may be added multiple times and leveled. Thus, only the noise component with the aligned phase can be detected as background noise, while the noise component with the misaligned phase is ignored so as not to be background noise.

[0069] Then, in step S303, the lock-in amplifier 52 outputs the frequency component of the noise signal extracted in this manner to the microcomputer 53. Thus, the lock-in detection for detecting the noise signal is terminated.

[0070] In the following, we refer again to Figure 3 The impedance calculation process is described in detail.

[0071] When the processing of step S106 is completed and the input of the frequency component of the noise signal is received from the lock-in amplifier 52, the microcomputer 53 performs the processing of step S107. That is, in step S107, the microcomputer 53 determines whether the frequency component of the noise signal as input is greater than a prescribed reference value. Through this processing, the microcomputer 53 determines whether there is a noise signal. Therefore, the microcomputer 53 of the present embodiment corresponds to a noise determiner according to one embodiment of the present disclosure.

[0072] Specifically, if the determination performed in step S107 is negative, that is, the noise signal is not greater than a prescribed reference value, the process proceeds to step S103.

[0073] On the contrary, if the determination performed in step S107 is affirmative, then in step S108, the microcomputer 53 notifies the lock-in amplifier 52 of the measurement frequency to instruct the lock-in amplifier 52 to detect the frequency component of the measurement frequency in the response signal (with the noise signal). Figure 4 The described processing is similar, when the sine wave signal flows to the microcomputer 53 via the battery cell 42 as the response signal (with the noise signal), the microcomputer 53 causes the lock-in amplifier 52 to input (i.e., provide) the voltage change caused in the battery cell 42. At this time, the microcomputer 53 causes the lock-in amplifier 52 to perform the so-called lock-in detection to detect the frequency component of the frequency of the sine wave signal (i.e., the measurement frequency) in the response signal (with the noise signal). Here, the frequency component in the response signal input in step S108 necessarily contains an error caused by the noise signal.

[0074] Subsequently, when the processing of step S108 is completed and the microcomputer 53 receives the input of the frequency component in the response signal from the lock-in amplifier 52, the processing proceeds to step S109. In step S109, similar to the processing performed in step S106, the microcomputer 53 again instructs the lock-in amplifier 52 to detect the noise signal in step S109. Then, the lock detection for detecting the noise signal is performed. However, since the lock detection for detecting the noise signal is roughly the same as the lock detection performed in step S106, its detailed description will be omitted below.

[0075] In addition, in the processing performed from step S106 to step S109, the phase of the reference signal needs to be adjusted to approximately the same value. That is, if the phase of the reference signal changes, the lock detection cannot be performed normally (sufficiently). In view of this, as a countermeasure, the reference signal output once in step S106 is continuously output in other steps other than step S106 to consistently maintain the same phase as the noise component.

[0076] Furthermore, after the processing of step S109 is completed and the frequency component of the noise signal is input from the lock-in amplifier 52, the processing proceeds to step S110, and the microcomputer 53 performs its processing. In step S110, the microcomputer 53 compares the frequency component in the noise signal input to itself during the processing of step S106 with the frequency component in the noise signal input during the processing of step S109. Subsequently, in step S110, the microcomputer 53 determines whether the difference (i.e., the difference in amplitude) of the noise signal is less than or equal to the threshold value. That is, the microcomputer 53 determines whether the noise signal changes before and after the frequency component in the response signal is obtained.

[0077] In addition, in step S111, if the judgment performed in step S110 is affirmative (i.e., no change), the microcomputer 53 removes the noise signal from the frequency component of the response signal input to itself during the processing of step S108. More specifically, the microcomputer 53 compares the frequency component in the response signal input to itself during the processing of step S108 with the frequency component in the noise signal input to itself during the processing of step S106 (or step S109), and removes the noise signal. In short, the microcomputer 53 removes the noise signal by subtracting the frequency component of the noise signal from the frequency component in the response signal. Therefore, the microcomputer 53 corresponds to a noise controller according to one embodiment of the present disclosure.

[0078] Then, the process proceeds to step S104. Then, in step S104, the microcomputer 53 calculates all or any of the real part, imaginary part, absolute value and phase of the complex impedance based on the frequency component in the response signal calculated in step S111 and the current signal output from the battery cell 42.

[0079] On the contrary, if the judgment performed in step S110 is negative (i.e., there is a change), then in step S112, the microcomputer 53 judges whether the number of measurements of the response signal is less than or equal to the prescribed number of times. If the judgment is affirmative, the process proceeds to step S106 again. At this time, the number of measurements of the response signal is increased by 1. At the start or end of the impedance calculation process, the number of measurements is cleared.

[0080] On the contrary, if the determination performed in step S112 is negative, then in step S113, the microcomputer 53 outputs an abnormal signal to the ECU 60 via the communication unit 54 to inform the ECU 60 that the microcomputer 53 cannot accurately input the response signal thereto. This is because the background noise changes drastically and does not fall within the practical measurable range as the response signal within a given period of time. Then, the impedance calculation process is terminated.

[0081] The impedance calculation process is repeatedly performed until complex impedances at multiple frequencies respectively included in the measurable range are calculated. In addition, based on such calculation results, the ECU 60 generates, for example, a complex impedance plane diagram (i.e., a Kerr diagram) to identify the characteristics of the electrode and the electrolyte, etc. For example, the ECU 60 can identify the power storage state (i.e., SOC) and the degradation state (i.e., SOH).

[0082] Furthermore, it is not always necessary to completely generate the Cole diagram, but the Cole diagram may be generated only partially. For example, based on the change in complex impedance measured for a given frequency at a given interval during vehicle travel, it can be known that SOC, SOH, battery temperature, etc. caused during vehicle travel change over time. Alternatively, when complex impedance is measured for a specified frequency at a certain interval such as every other day, every other week, every other year, etc., it can also be known that SOH, etc. change over time based on the change in complex impedance obtained for the specified frequency.

[0083] Therefore, the battery monitoring system 50 of the first embodiment described above can obtain the advantages described below.

[0084] First, as described above, the lock-in amplifier 52 detects the frequency component in the response signal corresponding to the measurement frequency based on the value obtained by multiplying the response signal by the reference signal. Then, the microcomputer 53 calculates the complex impedance based on the frequency component in the response signal and the sine wave signal (i.e., the current signal). Therefore, by performing the so-called lock-in detection in this way, only the frequency component identical to the measurement frequency of the sine wave signal can be extracted from the response signal. Therefore, the complex impedance can be calculated with high accuracy while avoiding the interference of white noise and pink noise. In particular, when used in a vehicle, the complex impedance can be accurately calculated even if a large amount of noise is generated. In addition, since it is almost not disturbed by noise, the current (i.e., the sine wave signal) output from the battery cell 42 can be minimized. Therefore, the power consumption and the temperature rise of each of the battery cell 42 and the semiconductor switch element 56a can be suppressed.

[0085] In addition, when the frequency component in the response signal corresponding to the measurement frequency is measured in the manner described above, and there is a noise signal having the same frequency as the measurement frequency (i.e., included therein), the noise signal is also detected, thereby possibly generating an error. In particular, in a vehicle, various devices such as an inverter operate at a prescribed drive frequency, thereby being likely to output a noise signal at a prescribed frequency. For example, even in the first embodiment, the inverter 30 sometimes operates at a prescribed drive frequency.

[0086] In view of this, before outputting the sine wave signal from the battery unit 42, it is determined whether there is a noise signal to be output corresponding to the frequency (ie, the measurement frequency) of the sine wave signal indicated by the microcomputer 53. Then, if there is such a noise signal, the noise signal is removed.

[0087] More specifically, the microcomputer 53 subtracts the frequency component of the noise signal from the frequency component in the response signal, and calculates the complex impedance based on the frequency component in the response signal obtained after this subtraction and the current signal output from the battery cell 42. Thus, even when there is a noise signal having the same frequency as the measurement frequency, the influence of the noise signal can be suppressed or reduced, thereby enabling highly accurate detection of the complex impedance.

[0088] Furthermore, before the battery cell 42 outputs the sinusoidal wave signal, the lock-in amplifier 52 receives an input of a noise signal flowing through the battery cell 42. Then, the lock-in amplifier 52 detects a frequency component in the noise signal corresponding to the sinusoidal wave signal based on a value obtained by multiplying the noise signal by a reference signal determined according to the sinusoidal wave signal indicated by the indication signal to be output.

[0089] Thus, as in the case of calculating complex impedance, since the frequency component in the noise signal corresponding to the measurement frequency is subjected to lock detection, the noise signal can be removed with high accuracy. In addition, since the noise signal is identified using the lock amplifier 52, the system can be simplified.

[0090] In addition, as described above, in the vehicle, since the inverter 30 and the like operate at a prescribed driving frequency, a noise signal is likely to be generated based on the prescribed driving frequency in a specific frequency band. In view of this, when the measurement frequency specified in step S101 is within the prescribed frequency range, the microcomputer 53 determines whether a noise signal exists. Thus, it is possible to easily determine whether a noise signal exists based on the measurement frequency.

[0091] Furthermore, when it is determined that a noise signal may exist, the microcomputer 53 determines whether the noise signal actually exists based on the determination of whether the frequency component in the noise signal detected by the lock-in amplifier 52 is greater than the reference value by using lock-in detection. Thus, it is possible to determine whether a noise signal actually exists with high accuracy.

[0092] Furthermore, the current modulation circuit 56 causes the battery cell 42 as the monitoring target to output a sinusoidal wave signal (i.e., a prescribed AC signal) based on the power supplied by the battery cell 42. Therefore, there is no need for an external power supply to input a sinusoidal wave signal to the battery cell 42, thereby being able to reduce the number of components and miniaturize the system at low cost.

[0093] In addition, since peripheral circuits such as protection elements, filter circuits, etc. are generally connected to the battery mounted on the vehicle, when an AC signal is input to the battery, current partially leaks to the peripheral circuits. For example, also in the first embodiment, the RC filter 55a and the Zener diode 55b are connected to the battery cell 42, and when an AC signal is input to the battery cell 42, current partially leaks to these circuits. Therefore, when an AC signal is input to the battery cell 42 and complex impedance is calculated based on a response signal from the battery cell 42, an error occurs in the response signal due to the influence of the current leakage, thereby deteriorating the detection accuracy of the complex impedance detection.

[0094] However, in the battery monitoring system 50 of the first embodiment, since the sinusoidal wave signal output is controlled based on the power supplied from the battery cell 42, a closed loop can be formed by including the current modulation circuit 56 and the battery cell 42. Therefore, current does not leak from the battery cell 42, so that errors in the response signal can be suppressed.

[0095] In addition, sometimes an error occurs between the signal actually flowing through the resistor 56b (included in the current modulation circuit 56) and the sine wave signal output from the battery cell 42, resulting in an error in the response signal. In view of this, according to the first embodiment of the present disclosure, the feedback circuit 56d (in the current modulation circuit 56) is configured to perform feedback based on the comparison between the feedback signal (i.e., the detection signal) and the indication signal when the semiconductor switch element 56a is indicated. Thereby, the sine wave signal can be continuously and accurately output from the battery cell 42 according to the indication.

[0096] In addition, when the current modulation circuit 56 is instructed by the instruction signal to obtain the waveform of the sine wave signal, the instruction signal is converted from a digital signal to an analog signal, which may cause an error during the conversion. In this case, if a filter circuit or the like is provided between the lock-in amplifier 52 and the current modulation circuit 56 to smooth the waveform of the instruction signal, the error can be suppressed. However, this will increase the size of the system or become expensive.

[0097] In addition, when the complex impedance is calculated, since the battery cell 42 of the vehicle generally has a large capacity, the measurement range of the measurement frequency tends to be wider. Therefore, the size of the filter circuit is likely to increase accordingly. Therefore, in the first embodiment, feedback control is performed to suppress the error in the waveform of the indication signal during signal conversion. Thus, the filter circuit does not need to be configured between the lock-in amplifier 52 and the current modulation circuit 56. As an exception, an anti-aliasing filter can be used for AD conversion as needed.

[0098] In addition, the current modulation circuit 56 is configured to detect the signal (i.e., current) flowing through the resistor 56b and output this detection signal to the lock-in amplifier 52 as a feedback signal. The lock-in amplifier 52 is configured to be able to use the feedback signal as the current signal. Thus, if the feedback signal (i.e., the signal actually flowing through the resistor 56b) is used, even when an error occurs between the signal actually flowing through the resistor 56b and the sine wave signal to be output (i.e., output instructed by the microcomputer), the calculation accuracy of the complex impedance can be improved.

[0099] In this way, when the error is corrected by using the feedback signal, the battery monitoring system 50 can be miniaturized because the filter circuit can be omitted from between the lock-in amplifier 52 and the current modulation circuit 56. In addition, as described above, although the anti-aliasing filter for AD conversion is used as needed, since a relatively high cutoff frequency can be used, an element with a small constant can be used, thereby also miniaturizing the system.

[0100] Furthermore, in the first embodiment, since the response signal input terminal 58 is connected to the terminal portion closest to the electrode of the battery cell 42, the influence of the impedance component generated by the terminal portion of the battery cell 42 is suppressed or reduced, thereby further improving the calculation accuracy of the complex impedance. To describe in more detail, the pair of terminals 42a of the battery cell 42 has the following structure: Fig. 6A and Figure 6B Therefore, the set of response signal input terminals 58 is preferably connected to a Fig. 6A The corresponding portion of the electrode shown is closer to Figure 6B The corresponding part of the electrode shown can thus further improve the calculation accuracy of the complex impedance. Figure 6B As shown, the connection portion of the set of response signal input terminals 58 is preferably closer to the electrode than the connection portion of the current modulation circuit 56 .

[0101] Now, the following will refer to Figure 7 The battery monitoring system 50 according to the second embodiment is described. As shown in the figure, in the second embodiment, the impedance calculation process is different from the impedance calculation process performed in the first embodiment. Specifically, Figure 7 As shown, in the impedance calculation process of the second embodiment, the process of step S102 is omitted. That is, regardless of the value of the measurement frequency, the frequency component in the noise signal corresponding to the measurement frequency is subjected to lock detection, and whether the noise signal exists is judged based on the magnitude of the frequency component. Hereinafter, the same reference numerals are marked to the same or equivalent parts in each embodiment described below, and the description is incorporated herein by reference.

[0102] Now, the following will refer to Figure 8 The battery monitoring system 50 according to the third embodiment is described. As shown in the figure, in the third embodiment, the impedance calculation process is different from the impedance calculation process of the first embodiment being performed again. Specifically, Figure 8 As shown, in the impedance calculation process of the third embodiment, it is not determined whether a noise signal exists. That is, the processes of steps S102, S103, and S107 are omitted.

[0103] Therefore, regardless of the presence or absence of the noise signal, the microcomputer 53 performs lock detection every time to detect the frequency component corresponding to the measurement frequency in the noise signal. Then, the microcomputer 53 removes the detected frequency component of the noise signal from the frequency component of the response signal.

[0104] Now, the following will refer to Fig. 9 The battery monitoring system 50 according to the fourth embodiment will be described. As shown in the figure, in the fourth embodiment, the impedance calculation process is again different from the impedance calculation process performed in the first embodiment. That is, Fig. 9 As shown, as described below, in the impedance calculation process of the fourth embodiment, the noise signal is not removed but avoided.

[0105] Specifically, the microcomputer 53 of the battery monitoring system 50 periodically executes the following Fig. 9 The impedance calculation process is shown. Fig. 9 In the impedance calculation process, since the processes from step S101 to step S105 are substantially the same as those in the first embodiment, description thereof will not be repeated.

[0106] Hereinafter, the processing performed in the fourth embodiment when the determination performed in step S102 is affirmative will be described. That is, the processing performed when the measurement frequency is included in the prescribed frequency range and thus a noise signal having a prescribed frequency is likely to occur will be described.

[0107] Specifically, if the determination performed in step S102 is positive, the microcomputer 53 changes the measurement frequency in step S401. In order to change the measurement frequency, any method can be adopted, and only the new measurement frequency is required to deviate from the frequency range. After the processing of step S401 is completed, the processing proceeds to the processing of step S102. Thus, the microcomputer 53 can easily avoid noise signals.

[0108] Now, the following will refer to Fig.10 The battery monitoring system 50 according to the fifth embodiment is described. As shown in the figure, in the fifth embodiment, the impedance calculation process is different from the impedance calculation process performed in the first embodiment. Specifically, Fig.10As shown, as described below, in the impedance calculation process of the fifth embodiment, the noise signal is not removed but avoided.

[0109] Specifically, the microcomputer 53 of the battery monitoring system 50 periodically executes the following Fig.10 As shown in the figure, in the impedance calculation process, similar to the process of step S101, in step S501, the microcomputer 53 specifies a measurement frequency for calculating complex impedance. The measurement frequency is specified from the frequencies included in the prescribed measurement range.

[0110] Subsequently, in step S502, the microcomputer 53 instructs the lock-in amplifier 52 to detect the noise signal (i.e., background noise), as performed in the process of step S106. Specifically, in step S502, the microcomputer 53 causes the lock-in amplifier 52 to perform lock detection to detect the noise signal (i.e., background noise) that can be detected when no interference is applied to the battery cell 42. Here, since the previous reference Figure 5 The lock detection of the noise signal performed by the lock-in amplifier 52 is described, and thus a detailed description thereof will not be repeated.

[0111] When the processing of step S502 is completed and the frequency component of the noise signal is input thereto, in step S503, the microcomputer 53 determines whether the frequency component of the noise signal as input is greater than the reference value. If the determination is negative, that is, the noise signal is not greater than the reference value, then in step S504, the microcomputer 53 notifies the lock-in amplifier 52 of the measurement frequency performed in step S103, and instructs the lock-in amplifier 52 to detect the frequency component corresponding to the measurement frequency in the response signal. Here, since the previous reference Figure 4 The lock detection of the response signal performed by the lock-in amplifier 52 is described, and thus the same description is not repeated.

[0112] Subsequently, in step S505, upon receiving the frequency component of the response signal, the microcomputer 53 calculates all or any of the real part, imaginary part, absolute value, and phase of the complex impedance based on the frequency component in the received response signal and the current signal output from the battery cell. Here, the current signal may be obtained based on a feedback signal or a sine wave signal indicated by the indication signal to be output.

[0113] Subsequently, in step S506, the microcomputer 53 outputs the calculated complex impedance to the ECU 60 via the communication unit 54. Then, the impedance calculation process is terminated.

[0114] On the contrary, if the judgment performed in step S503 is affirmative, then in step S507, the microcomputer 53 judges whether the number of times when the lock detection of the noise signal is performed is less than or equal to the prescribed value. Similarly, similar to the processing performed in step S401 of the fourth embodiment, any method of changing the measurement frequency can be adopted. When the processing of step S508 is completed, the processing proceeds to step S502. Similarly, similar to the processing performed in step S401 of the fourth embodiment, any method of changing the measurement frequency can be adopted. When the processing of step S508 is completed, the processing proceeds to step S502.

[0115] Furthermore, in contrast, if the determination in step S507 is negative, then in step S509, the microcomputer 53 outputs an abnormality signal to the ECU 60 via the communication unit 54 to notify that the microcomputer 53 cannot accurately receive the response signal. Then, the impedance calculation process is terminated.

[0116] Therefore, by executing the impedance calculation process as shown in the fifth embodiment, the microcomputer 53 can easily and effectively avoid the noise signal.

[0117] Now, the following will refer to Fig.11 A battery monitoring system 50 according to a sixth embodiment is described. Specifically, the battery monitoring system 50 of the sixth embodiment performs so-called two-phase lock detection, as will be described in detail below.

[0118] That is, Fig.11 As shown, in the lock-in amplifier 52, the preamplifier 152 is set as an amplifier so as to receive the voltage change of the battery cell 42 through a set of response signal input terminals 58 when outputting a sine wave signal. The preamplifier 152 amplifies the voltage change input through the response signal input terminal 58 and outputs the amplified result as a response signal. That is, since the amplitude of the response signal is relatively weak when compared with the voltage of the battery cell 42, the preamplifier 152 is set to enhance and improve the detection accuracy of the response signal. Here, although one stage of the preamplifier 152 is set in the sixth embodiment, multiple stages of the preamplifier 152 may be used.

[0119] In addition, if Fig.11 As shown, a capacitor C1 is provided between the positive electrode terminal of the battery cell 42 and the response signal input terminal 58 located closer to the positive electrode (i.e., the positive electrode terminal) of the preamplifier 152 to remove the DC component. Thus, the DC component (the portion that is not related to the internal complex impedance information) can be removed from the voltage change of the battery cell 42, thereby improving the detection accuracy of the response signal.

[0120] Furthermore, an AD converter 154 is provided in the lock-in amplifier 52 to convert a response signal (ie, an analog signal) output from the preamplifier 152 into a digital signal and output this conversion result from the preamplifier 152 .

[0121] The AD converter 154 is also connected to each of the first multiplier 156 and the second multiplier 157 to input a response signal thereto.

[0122] In addition, an oscillation circuit 158, which will be described in detail later, is connected to the first multiplier 156 to input a first reference signal thereto. The first multiplier 156 multiplies the response signal by the first reference signal, thereby calculating a value proportional to the real part of the response signal corresponding to the measurement frequency. Then, the first multiplier 156 outputs the value proportional to the response signal to the microcomputer 53 via the low-pass filter 159. Fig.11 In , the real part of the response signal is represented as Re|Vr|.

[0123] In addition, the oscillation circuit 158 ​​is also connected to the second multiplier 157 via the phase shift circuit 160 to input the second reference signal thereto. The phase of the second reference signal is advanced by 90 degrees (i.e., π / 2) relative to the phase of the first reference signal. That is, the phase shift circuit 160 advances the phase of the sine wave signal (i.e., the first reference signal) received from the oscillation circuit 158 ​​as its input, and outputs such an advanced signal as the second reference signal.

[0124] The second multiplier 157 also multiplies the second reference signal by the response signal, thereby calculating a value proportional to the imaginary part of the response signal. Then, the second multiplier 157 outputs the value proportional to the imaginary part of the response signal to the microcomputer 53 via the low-pass filter 161. Fig.11 , the imaginary part of the response signal is represented as Im|Vr|. Therefore, the real part and the imaginary part of the response signal together correspond to the frequency component of the response signal corresponding to the measurement frequency.

[0125] In addition, the oscillation circuit 158 ​​outputs a sine wave signal determined according to the measurement frequency. As described above, the oscillation circuit 158 ​​outputs a sine wave signal to the first multiplier 156 and the phase shift circuit 160, respectively, as a first reference signal. In addition, the oscillation circuit 158 ​​is also connected to the indication signal output terminal 59a via the DA converter 162 to output the sine wave signal as an indication signal thereto.

[0126] Furthermore, the feedback signal input terminal 59b is connected to the microcomputer 53 via the AD converter 163. Therefore, the microcomputer 53 receives an input of a feedback signal (ie, a detection signal) from the feedback signal input terminal 59b.

[0127] Therefore, the microcomputer 53 receives input of values ​​proportional to the real and imaginary parts of the response signal, thereby calculating the real and imaginary parts of the complex impedance based on these values. At the same time, the microcomputer 53 calculates (i.e., corrects) the real and imaginary parts of the complex impedance based on the received feedback signal, taking into account the amplitude of the actual flowing signal and the deviation from the phase of the reference signal.

[0128] In addition, the microcomputer 53 also calculates the absolute value and phase of the complex impedance. Specifically, since the real part and the imaginary part of the response signal can be known by performing two-phase lock detection, the absolute value and the phase of the complex impedance can be calculated by the formula |Vr|e jθv It can be represented on a polar coordinate display as (the voltage of the response signal), where θv represents the phase of the response signal. Similarly, its current can be expressed by the formula |I|e jθi Therefore, since the equation V = ZI is well known, when the polar coordinate display of the complex impedance is given by the formula |Z|e j θz When it is expressed, the first equation described below can be established, where j represents the equation j that satisfies 2 = the imaginary unit of -1.

[0129] |Z|e jθz =|Vr|e jθv / |I|e jθi

[0130] Therefore, the absolute value of the complex impedance is obtained by calculating the formula |Z|=|Vr| / |I|. In addition, the phase can be obtained by calculating the formula θv-θi. Then, the microcomputer 53 outputs this calculation result to the ECU 60 via the communication unit 54. Fig.11 As shown, the absolute value of the complex impedance is represented by |Z|. The phase of the complex impedance is represented by arg(Z).

[0131] Now, the following will refer to Fig.12 The lock detection performed in the sixth embodiment is described. Fig.12 An exemplary process performed when the microcomputer 53 notifies the lock-in amplifier 52 of the measurement frequency in step S103 and the like so that the lock-in amplifier 52 acquires a frequency component corresponding to the measurement frequency from the response signal is described.

[0132] Specifically, the oscillation circuit 158 ​​of the lock-in amplifier 52 determines the frequency of the sine wave signal (i.e., the specified AC signal) based on the measurement frequency indicated by the microcomputer 53. Subsequently, in step S601, the oscillation circuit 158 ​​outputs an indication signal from the indication signal output terminal 59a to the current modulation circuit 56 via the DA converter 162 to indicate that the current modulation circuit 56 outputs a sine wave signal. When this digital signal is converted into an analog signal by the DA converter 162, an appropriate offset value (i.e., DC bias) is added to the digital signal and converted together. Specifically, the offset value can be expected to be determined by the microcomputer 53 based on the DC voltage of the battery cell 42. This DC voltage of the battery cell 42 can be measured by the voltage measuring unit 57.

[0133] Thus, based on the electric power supplied from the battery cell 42 , the current modulation circuit 56 causes the battery cell 42 to output a sinusoidal wave signal based on the instruction signal.

[0134] Furthermore, when a sinusoidal wave signal is output from the battery cell 42, a voltage change that reflects the internal complex impedance of the battery cell 42 occurs between the positive electrode terminal and the negative electrode terminal of the battery cell 42. Then, in step S602, the preamplifier 152 in the lock-in amplifier 52 receives an input of the voltage change via the response signal input terminal 58 and outputs the input as a response signal.

[0135] Here, when input to the response signal input terminal 58, the DC component of the voltage change is removed by the capacitor C1, so that only the characteristic part of the voltage change is extracted. In addition, the preamplifier 152 amplifies the voltage change weakened by removing the DC component, and outputs this amplification result as a response signal. At this time, the AD converter 154 converts the response signal input via the signal switching unit (not shown) into a digital signal and outputs this conversion result. Here, the size of the DC component removed by the capacitor C1 is preferably determined according to the DC voltage of the battery cell 42. Similarly, the voltage change amount to be amplified is preferably determined according to the DC voltage of the battery cell 42.

[0136] Furthermore, in step S603, the first multiplier 156 multiplies the response signal inputted to itself from the AD converter 154 by the sine wave signal (i.e., the first reference signal) inputted to itself from the oscillation circuit 158, thereby calculating a value proportional to the real part of the response signal. Similarly, the second multiplier 157 multiplies the response signal by the second reference signal inputted to itself from the phase shift circuit 160, thereby calculating a value proportional to the imaginary part of the response signal.

[0137] Then, in step S604, the lock-in amplifier 52 outputs the proportional values ​​to the microcomputer 53 via the low-pass filter 159 and the low-pass filter 161. Here, when the proportional values ​​pass through the low-pass filter 159 and the low-pass filter 161, signals other than the DC component are attenuated or removed.

[0138] When the lock detection is performed to detect the noise signal, the process of step S601 is omitted. That is, the lock detection to detect the noise signal is performed without outputting the instruction signal for instructing the current modulation circuit 56 to output the sine wave signal.

[0139] Therefore, according to the battery monitoring system 50 of the sixth embodiment, various advantages described below can be obtained.

[0140] First, the lock-in amplifier 52 detects a value proportional to the real part of the response signal based on a value obtained by multiplying the response signal as an input by a first reference signal. In addition, the lock-in amplifier 52 detects a value proportional to the imaginary part of the response signal based on a value obtained by multiplying the response signal by a second reference signal including a sine wave signal whose phase has been shifted. Subsequently, the microcomputer 53 calculates the complex impedance based on these values. Therefore, by performing the so-called two-phase lock detection in this way, only the frequency component that is the same as the measurement frequency can be extracted from the response signal. Thus, white noise and pink noise can be easily processed, so that the complex impedance can be calculated with high accuracy. In addition, by performing the two-phase lock detection, the phase adjustment between the reference signal and the response signal can be omitted.

[0141] Hereinafter, various modifications of the above-described embodiment of the present disclosure are described. First, although the battery monitoring system 50 is provided for each battery cell 42 in the above-described embodiment, the battery monitoring system 50 may be provided for each unit (e.g., battery module 41, battery pack 40) of the battery cell 42. In this case, the functions of the battery monitoring systems 50 may be shared with each other.

[0142] For example, Fig.13 As shown, the stable power supply unit 301, the communication unit 54, and the microcomputer 53 can be shared. In this case, the negative electrode potential of each battery cell 42 may sometimes be different. Therefore, the reference potential of each electrical signal used when sending the information of each battery cell 42 is sometimes different from each other. In view of this, it is necessary to input each electrical signal to the function of the microcomputer 53 according to the difference in the reference potential to perform calculations. As a signal transmission device that transmits signals between different reference potentials, capacitors, transformers, radio waves, and light can be exemplified.

[0143] Secondly, in the embodiment described above, the battery monitoring system 50 can perform an equalization process to equalize the power storage state and voltage of each battery cell 42. The equalization process includes a process of discharging a battery cell 42 that is in a higher power storage state than other battery cells 42 to equalize the power storage state with the power storage state of other battery cells 42. Thus, since the power storage state of each battery cell 42 is consistent with each other, partial overcharge of the battery cell 42 can be suppressed or reduced. In addition, when performing the equalization process, the battery monitoring system 50 can discharge the battery cell 42 by using the current modulation circuit 56. In this case, the battery monitoring system 50 functions as a discharge controller.

[0144] More specifically, in the modification described above, when a discharge instruction is received from the ECU 60 or the like according to the power storage state of each battery cell 42, or one of the power storage state and the voltage of the battery cell 42 becomes greater than a prescribed value, the microcomputer 53 outputs an instruction signal to the current modulation circuit 56 so that the battery cell 42 outputs a sine wave signal, a periodic function such as a rectangular wave, or a DC signal. Subsequently, the microcomputer 53 continuously outputs the instruction signal until the input of the discharge instruction becomes non-existent, or the power storage state or the voltage of the battery cell 42 becomes less than a prescribed value. Thus, the equalization process is completed.

[0145] Furthermore, when the battery cell 42 is discharged for the purpose of equalization processing, the complex impedance can be calculated by causing the battery cell 42 to output a sine wave signal. Thus, power consumption can be suppressed or reduced. Here, the current output for the purpose of equalization is generally weak to suppress or reduce power consumption and minimize the system. Therefore, even if a weak current is used as in the above-mentioned modification, it is particularly advantageous to adopt the equalization processing in the battery monitoring system 50 because the complex impedance is accurately calculated therein based on the lock detection.

[0146] In addition, in the above-described embodiment, the filter unit 55 does not necessarily have to include only components. For example, a wiring system, a connector contact portion, a pattern wiring system formed on a printed circuit board, and a solid pattern may be included to constitute the filter unit 55. In addition, a mixture of these devices and components may also be used.

[0147] Furthermore, in the embodiment described above, a filter circuit may be provided between the current modulation circuit 56 and the lock-in amplifier 52. Thus, an error generally caused when the indication signal is converted into an analog signal may be suppressed or reduced.

[0148] Furthermore, in the embodiment described above, the feedback circuit 56d may be omitted. Furthermore, the current flowing through the resistor 56b is not necessarily detected by the current detection amplifier 56c. Furthermore, the microcomputer 53 may not receive the feedback signal.

[0149] Furthermore, although the voltage measuring unit 57 is provided to detect the DC voltage in the embodiment described above, it is not necessary to detect the DC voltage.

[0150] Furthermore, the battery monitoring system 50 of the above-described embodiment can be used in various vehicles such as HEV (hybrid electric vehicle), EV (electric vehicle), PHV (plug-in hybrid electric vehicle), etc. The battery monitoring system 50 of the above-described embodiment can also be used in auxiliary batteries, electric aircraft, and electric motorcycles. The battery monitoring system 50 of the above-described embodiment can also be used in electric ships.

[0151] Furthermore, in the embodiment described above, the battery cells 42 may be connected in parallel to each other.

[0152] Furthermore, in the embodiment described above, the state of the battery can be monitored for each battery module 41. In this case, specifically, when the communication unit 54 is provided for each battery module 41, the communication from each communication unit 54 to the ECU 60 sometimes becomes a so-called insulation communication requiring a different potential standard, such as when an insulation transformer or a capacitor is used.

[0153] Furthermore, in the embodiment described above, the feedback signal can be detected by using lock detection including two-phase lock detection. Thus, by measuring the feedback signal using lock detection, the amplitude and phase of the current signal actually output from the battery cell 42 can be accurately measured even when noise is included. Furthermore, if the feedback signal is used to calculate the complex impedance, its calculation accuracy can be effectively improved.

[0154] Here, when the measured frequency component of the current signal such as the feedback signal is obtained by applying the lock detection and used for calculating the complex impedance, it is also necessary to compare with the lock detection period during which the current signal is detected. Figure 3, to remove the noise component. For example, the timing for performing lock detection on the current signal may be before or after the measurement of the response signal, or before and after the measurement of the response signal. In this case, when the detection of the current signal is performed before and after the measurement of the response signal, and when the difference in the noise component obtained before and after the measurement of the response signal is greater than a prescribed reference value, the measurement process is performed again. In addition, when the difference in the noise component obtained before and after the measurement does not decrease to less than a prescribed reference value even if the measurement is repeated a prescribed number of times, an abnormal signal is output to the ECU 60, and the impedance calculation process is terminated.

[0155] Furthermore, in the embodiment described above, the current signal to be output from the battery unit 42 is not limited to a sine wave signal, and may be a signal such as a rectangular wave, a triangular wave, or the like as long as it is an AC signal.

[0156] In addition, in the above-described embodiment, the ECU 60 may include a plurality of ECU elements. For example, a plurality of ECU elements may be provided for each function. In addition, a plurality of ECU elements may be provided for each control target. For example, the plurality of ECU elements may be divided into a battery-specific ECU element and an inverter-specific ECU element.

[0157] In addition, in the embodiment described above, when the battery cell 42 (i.e., the battery module 41 or the assembled battery 40) outputs a sine wave signal (i.e., a response signal) based on an instruction, the battery cell 42 can be used as a power source for a peripheral circuit. On the contrary, the battery cell 42 (i.e., the battery module 41 or the assembled battery 40) can be configured so that when the battery cell 42 outputs a sine wave signal (i.e., a response signal) based on an instruction, it cannot be used as a power source for a peripheral circuit.

[0158] In addition, the method of changing the measurement frequency performed in each process of step S401 of the fourth embodiment and step S508 of the fifth embodiment can be performed as described below. That is, referring to the previously acquired complex impedance plane diagram (i.e., Kerr diagram), the frequency closest to the current measurement frequency is identified from the frequencies expected to cause a complex impedance change amount smaller than a specified value, and the frequency is used as the measurement frequency. In this case, whether the change amount is relatively small can be identified by the difference amount. In addition, the battery state (e.g., the temperature, SOC of the battery cell 42) acquired last time can be compared with the current battery state to predict the current complex impedance plane diagram, and the frequency can be predicted based on the complex impedance plane diagram.

[0159] Furthermore, in the embodiment described above, as the noise source, not only a noise source such as the inverter 30 mounted on the vehicle but also a noise source such as a quick charger temporarily connected to the vehicle may be included.

[0160] In addition, in the embodiment described above, the measurement range specified for calculating the complex impedance (see step S101, etc.) can be determined based on the frequency of the noise signal output from the noise source installed on the vehicle (e.g., inverter 30) or the noise source temporarily connected to the vehicle (e.g., fast charger). Specifically, a range of frequencies that can avoid noise signals can be adopted. For example, as a method of specifying the measurement range, a mapping of frequencies for predicting noise generation is obtained in advance, and frequencies other than the frequencies on the mapping can be specified. Thus, it is not necessary to determine the noise or remove the noise.

[0161] In addition, as another example, one or more fixed frequencies are predetermined, and a given measurement frequency is selectively specified from the fixed frequencies. Here, for example, the fixed frequencies can be determined from the frequencies included in the measurement range as described above. In addition, a mapping of frequencies for predicting noise generation can be obtained in advance, and a fixed frequency can be determined to avoid the frequency on the mapping. In addition, both selecting a fixed frequency and specifying a frequency from the measurement range can be adopted simultaneously.

Claims

1. A battery monitoring system for monitoring the state of a battery comprising an electrolyte and a plurality of electrodes, the battery monitoring system comprising: a waveform designator that designates a waveform of an AC signal output from the battery, the waveform defining at least one frequency thereof as a reference frequency; a signal controller that causes the storage battery to output an AC signal as a response signal, the storage battery outputting the AC signal based on its own power; a response signal input unit, the response signal input unit receiving the AC signal of the response signal from the battery; a frequency component detector that detects an AC signal having a frequency component corresponding to the reference frequency included in the response signal, the frequency component detector detecting the AC signal through lock detection performed based on a product of the reference frequency and the response signal received by the response signal input unit; a calculator that calculates a complex impedance of the battery based on the frequency component of the AC signal detected by the frequency component detector in the response signal; a noise determiner for determining whether there is a noise signal having a frequency corresponding to the reference frequency of the AC signal before the signal controller causes the storage battery to output the AC signal; as well as a noise controller, wherein when the noise determiner identifies the presence of the noise signal, the noise controller removes the noise signal at least before the calculator calculates the complex impedance of the battery, When the noise determiner determines whether a noise signal is present, the phase of the AC signal specified by the waveform designator is the same as the phase of the AC signal specified by the waveform designator when the response signal input unit inputs a response signal, The frequency component detector is configured to input a noise signal flowing through the battery before the signal controller causes the AC signal to be output, and detect a frequency component corresponding to the frequency of the AC signal in the noise signal based on a product of the noise signal and a reference frequency determined based on the AC signal specified by the waveform specifyor, the noise determiner determines whether there is a noise signal corresponding to the frequency of the AC signal specified by the waveform specifyer based on the frequency component of the noise signal detected by the frequency component detector, The noise controller subtracts the frequency component of the noise signal detected by the frequency component detector from the frequency component of the response signal detected by the frequency component detector before the complex impedance is calculated by the calculator. The calculator calculates the complex impedance of the battery based on the calculation result of the noise controller.

2. The battery monitoring system according to claim 1, wherein: The noise determiner identifies whether the noise signal exists when the reference frequency of the AC signal is within a given noise range.

3. The battery monitoring system according to claim 1, wherein: The noise controller instructs the signal controller to cause the battery to output the AC signal by changing the frequency of the AC signal.

4. A method for monitoring the state of a battery, comprising: A given waveform of an AC signal is specified by indicating a frequency as a reference frequency; determining whether there is a noise signal flowing through the battery and having a frequency corresponding to the reference frequency; causing the storage battery to output an AC signal as a response signal based on its own power; receiving the AC signal of the response signal from the battery; When it is determined that the noise signal exists, removing the noise signal from the response signal; Based on the product of the reference frequency and the response signal, detecting an AC signal of a frequency component in the response signal corresponding to the reference frequency of the AC signal; as well as calculating the complex impedance of the battery based on the frequency component of the AC signal in the response signal, When determining whether there is a noise signal, the phase of the AC signal specified is the same as the phase of the AC signal specified when receiving the response signal, Before outputting the AC signal, a noise signal flowing through the battery is input, and a frequency component corresponding to the frequency of the AC signal in the noise signal is detected based on a product of the noise signal and a reference frequency determined according to the specified AC signal, Based on the frequency component of the detected noise signal, it is determined whether there is a noise signal corresponding to the specified frequency of the AC signal, Before calculating the complex impedance, the frequency component of the detected noise signal is subtracted from the frequency component of the detected response signal. And the complex impedance of the battery is calculated based on the calculation result.

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