JP2013160613A - Storage battery characteristics derivation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a storage battery characteristics derivation device capable of deriving an equivalent circuit constant of a storage battery with high precision.SOLUTION: A storage battery characteristics derivation device includes a current waveform analysis part that analyzes pulsed charging and discharging current waveforms during the transient response of the storage battery and a constant derivation part that derives part of an equivalent circuit constant of the storage battery based on each data on the charging and discharging currents of the storage battery and a voltage across the storage battery when the charging and discharging current waveforms analyzed by the current waveform analysis part satisfy a first condition and that derives another equivalent circuit constant of the storage battery based on each data of the charging and discharging currents of the storage battery and a voltage across the storage battery when the charging and discharging current waveforms analyzed by the current waveform analysis part satisfy a second condition. The equivalent circuit constant of the storage battery includes a first constant that is dominant at a frequency during a transient response when the first condition is satisfied and a second constant that is dominant at a frequency during a transient response when the second condition is satisfied. A pulse width and a pulse frequency during the transient response when the first condition is satisfied differ from a pulse width and a pulse frequency during the transient response when the second condition is satisfied, respectively.

Description

  The present invention relates to a storage battery characteristic deriving device for deriving an equivalent circuit constant of a storage battery.

  FIG. 7 is a block diagram showing a configuration of an apparatus for measuring the internal impedance of the storage battery. In the apparatus shown in FIG. 7, an AC signal (also referred to as “perturbation signal”) is supplied to the storage battery, and at this time, the internal impedance of the storage battery is calculated based on the current flowing through the storage battery and the terminal voltage. Since the apparatus requires a configuration for supplying an AC signal, it is difficult to reduce the size, and the place of use or installation is limited. For example, it is not realistic to mount the device on a vehicle or the like in which a space for mounting components is limited. However, vehicles such as EVs (Electric Vehicles) and HEVs (Hybrid Electrical Vehicles) have a storage battery, and it is very important to manage the characteristics or state of the storage battery in the vehicle.

  FIG. 8 is a Nyquist diagram showing an example of the internal impedance characteristics of the storage battery. Moreover, FIG. 9 is a figure which shows the equivalent circuit of a storage battery. As shown in FIG. 8, the internal impedance characteristics of the storage battery differ for each frequency. In FIG. 8, the inductance component is dominant at a frequency of 1 kHz or higher, the conductance component is dominant at a frequency of 1 Hz to 1 kHz, and a characteristic corresponding to CPE (Constant Phase Element) is shown at a frequency of 1 Hz or lower. ing. The battery characteristic evaluation apparatus described in Patent Document 1 does not include an AC signal generator, and identifies circuit constants for an equivalent circuit model based on the current-voltage characteristics of the storage battery.

JP 2011-141228 A

  However, in order to derive the internal impedance characteristics of a storage battery, even if the circuit constant for the equivalent circuit model of the storage battery is estimated from the output value of the transient response waveform obtained from the storage battery, the estimated value is uniform over the entire frequency band. It is only an optimized value. That is, depending on the frequency, the estimation accuracy of the internal impedance characteristics of the storage battery may be low. FIG. 10 is a diagram illustrating an example of a current waveform and a response waveform of the voltage between terminals when the storage battery is pulse-discharged for 5 seconds. FIG. 11 is a Nyquist diagram showing a difference between an actual internal impedance characteristic of the storage battery indicated by a cross point and an estimated internal impedance characteristic indicated by a solid line.

  In the example shown in FIG. 11, since the arcs with two time constants are different between the actual characteristics and the estimated characteristics, the internal impedance characteristics in the high frequency band after 1 Hz are different between the actual value and the estimated value. This difference is due to the fact that fitting is performed with a much longer time waveform for a characteristic having a small time constant, that is, a minute time in which the change is noticeable. That is, in the example shown in FIG. 10, since fitting is performed with waveform data for 10 seconds, characteristics in the vicinity of 0.1 Hz to 1 Hz, which have a large number of time samples, are focused on the high frequency side after 1 Hz. This is because the error becomes relatively large. As a result, the accuracy of the estimated value of the equivalent circuit constant of the storage battery decreases.

  An object of the present invention is to provide a storage battery characteristic deriving device capable of accurately deriving an equivalent circuit constant of a storage battery.

  In order to solve the above problems and achieve the object, the storage battery characteristic deriving device of the invention according to claim 1 is an equivalent circuit constant of a storage battery (for example, storage cells C1, C2,... Cn in the embodiment). Is a storage battery characteristic deriving device (for example, cell impedance calculation units 13, 131, 132,... 13n in the embodiment), and analyzes the waveform of the charge / discharge current during the pulse-like transient response of the storage battery. The charge / discharge current and both ends of the storage battery when the waveform of the charge / discharge current analyzed by the current waveform analysis unit (for example, the current waveform analysis unit 121 in the embodiment) and the current waveform analysis unit satisfies the first condition Based on each data of voltage, the equivalent circuit constant of a part of the storage battery is derived, and the charge / discharge current of the storage battery when the waveform of the charge / discharge current analyzed by the current waveform analysis unit satisfies the second condition, and Both A constant deriving unit (for example, the arithmetic unit 125 in the embodiment) for deriving another equivalent circuit constant of the storage battery based on each data of the voltage, and the equivalent circuit constant of the storage battery is the first circuit constant A first constant that is dominant in the frequency at the time of the transient response when the second condition is satisfied, and a second constant that is dominant in the frequency at the time of the transient response when the second condition is satisfied, The pulse width and pulse frequency during the transient response when the condition is satisfied are different from the pulse width and pulse frequency during the transient response when the second condition is satisfied.

  Furthermore, in the storage battery characteristic deriving device according to the second aspect of the present invention, the constant deriving unit calculates the internal impedance of the storage battery from a value obtained by frequency-converting each data of the charge / discharge current and the voltage at both ends of the storage battery. The calculation is performed for each frequency, the internal impedance characteristic of the storage battery is derived, and the equivalent circuit constant of the storage battery is derived based on the derived internal impedance characteristic.

  Furthermore, in the storage battery characteristic deriving device according to the third aspect of the present invention, the constant deriving unit is obtained by frequency-converting each data of the charge / discharge current and the both-end voltage of the storage battery when the first condition is satisfied. The charge / discharge current and the voltage at both ends of the storage battery when the second condition is satisfied while the first constant derived from the internal impedance characteristics of the storage battery derived from the measured value is fixed. The second constant is derived based on a characteristic obtained by synthesizing the internal impedance characteristic of the storage battery derived from the value obtained by the conversion and the internal impedance characteristic derived previously.

  According to the storage battery characteristic deriving device of the invention described in claims 1 to 3, the equivalent circuit constant of the storage battery can be derived with high accuracy.

Block diagram showing the relationship between a storage battery mounted on a vehicle and a part of an electric drive system Block diagram showing the internal configuration of the cell impedance calculation unit The graph which shows each waveform of the electric current I which satisfy | fills the 1st condition, and the voltage V between the terminals synchronized Nyquist diagram showing the actual internal impedance characteristics of the storage cell indicated by a cross point and the internal impedance characteristics indicated by the solid line calculated based on the current I and the inter-terminal voltage V shown in FIG. The graph which shows each waveform of the electric current I which satisfy | fills 2nd conditions, and the voltage V between the terminals synchronized The actual internal impedance characteristic of the storage cell indicated by the cross point, the internal impedance characteristic calculated based on the low frequency side of the internal impedance characteristic indicated by the solid line in FIG. 4, the current I and the inter-terminal voltage V shown in FIG. Nyquist diagram showing internal impedance characteristics combined with high frequency side The block diagram which shows the structure of the apparatus which measures the internal impedance of a storage battery Nyquist diagram showing an example of internal impedance characteristics of storage battery Diagram showing equivalent circuit of storage battery The figure which shows an example of the response waveform of the electric current waveform at the time of the pulse discharge of a storage battery for 5 second, and the voltage between terminals Nyquist diagram showing the difference between the actual internal impedance characteristic of the storage battery indicated by the cross point and the estimated internal impedance characteristic indicated by the solid line

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a relationship between a storage battery mounted on a vehicle and a part of an electric drive system. A vehicle such as EV (Electric Vehicle) or HEV (Hybrid Electrical Vehicle) is provided with a system shown in FIG. In this system, electric power is supplied from the assembled battery 11 to the electric motor MOT via the inverter INV. The assembled battery 11 has a plurality of power storage cells C1, C2,... Cn connected in series. In addition, the system includes cell impedance calculation units 131, 132,... 13n corresponding to each of the plurality of power storage cells, and a set for managing the state of the assembled battery 11 based on information obtained from each cell impedance calculation unit. A battery state management unit 15 is provided.

  Further, voltage sensors 171, 172,... 17n are provided in parallel in each of the plurality of power storage cells C1, C2,. Voltage sensors 171, 172,... 17n detect inter-terminal voltages V1, V2,. A current sensor 19 is provided on the current path from the assembled battery 11 to the inverter INV. The current sensor 19 detects a discharge current (hereinafter simply referred to as “current”) I flowing through the path from the assembled battery 11 to the inverter INV. Information indicating the inter-terminal voltage detected by each voltage sensor and information indicating the current detected by the current sensor 19 are input to the corresponding cell impedance calculation unit. The cell impedance calculators 131, 132,... 13n calculate the internal impedance of the storage cell by calculating the equivalent circuit constant of the corresponding storage cell.

  FIG. 2 is a block diagram showing an internal configuration of the cell impedance calculation unit. As shown in FIG. 2, the cell impedance calculation unit 13 includes low-pass filters (LPF) 101v and 101i, AD converters (ADC) 103v and 103i, a clock generation unit 105, a control unit 107, a condition storage unit 109, And an equivalent circuit constant calculation unit 111. The LPF 101v outputs only the low frequency component of the signal indicating the inter-terminal voltage V detected by the corresponding voltage sensor. The ADC 103v AD-converts the signal output from the LPF 101v and outputs the signal to the equivalent circuit constant calculation unit 111. The LPF 101 i outputs only the low frequency component of the signal indicating the current I detected by the current sensor 19. The ADC 103 i AD-converts the signal output from the LPF 101 i and outputs it to the equivalent circuit constant calculation unit 111. Note that the ADCs 103v and 103i perform AD conversion only while the clock signal is input in accordance with the clock signal generated by the clock generation unit 105.

  When receiving the operation start command from the assembled battery state management unit 15, the control unit 107 instructs the clock generation unit 105 to generate a clock signal having a predetermined sample rate. Further, when the control unit 107 receives the operation start command, the control unit 107 instructs the equivalent circuit constant calculation unit 111 to analyze the waveform indicated by the signal indicating the current I output from the ADC 103i. Note that the sample rate of the clock signal instructed by the control unit 107 to the clock generation unit 105 may vary depending on the analysis result of the current I performed by the equivalent circuit constant calculation unit 111. For example, the control unit 107 sets the sample rate to 1 kHz or more when the discharge pulse width of the current I is 5 seconds or longer and the state after the discharge interruption continues for 5 seconds or longer, and the discharge pulse width of the current I is 50 ± 10 m. In the case of the second and the state after the discharge interruption is 50 ± 10 milliseconds, the sample rate may be set to 10 kHz or more.

  The condition storage unit 109 stores a sample rate condition of the clock signal that the control unit 107 instructs the clock generation unit 105. In addition, the condition storage unit 109 stores conditions when the equivalent circuit constant calculation unit 111 calculates the equivalent circuit constant of the storage cell. The condition for calculating the equivalent circuit constant is the first condition in which the discharge pulse width of the current I is 5 seconds or more and the state after the discharge interruption is a low frequency pulse shape lasting 5 seconds or more, and the current I The discharge pulse width is 50 ± 10 ms, and the state after the discharge interruption is composed of a second condition having a high-frequency pulse shape of 50 ± 10 ms.

  The equivalent circuit constant calculation unit 111 includes a current waveform analysis unit 121, a data storage unit 123, and a calculation unit 125. In response to the analysis instruction obtained from the control unit 107, the current waveform analysis unit 121 analyzes the waveform of the signal indicating the current I output from the ADC 103i. Furthermore, the current waveform analysis unit 121 operates the calculation unit 125 when the waveform indicated by the analysis result satisfies either the first condition or the second condition described above stored in the condition storage unit 109. Instruct. Immediately after the ignition switch of the vehicle equipped with the system shown in FIG. 1 is turned on, the assembled battery 11 is controlled to perform pulse discharge at different frequencies. Therefore, the first condition and the second condition are obtained at different timings immediately after the ignition switch of the vehicle is turned on.

  The data storage unit 123 stores the data of the voltage V between the terminals output from the ADC 103v and the data of the current I output from the ADC 103i in a time-synchronized state. The calculation unit 125 calculates the equivalent circuit constant of the storage cell from the data of the voltage V and the current I between the terminals stored in the data storage unit 123.

Hereinafter, the calculation method of the equivalent circuit constant of the storage cell by the calculation unit 125 will be described in detail with reference to FIGS.
First, the calculation unit 125 reads the data of the voltage V between the terminals and the data of the current I while satisfying the first condition from the data storage unit 123, and discretely calculates the data of the voltage V and the current I between the terminals. Perform Fourier transform. Further, the calculation unit 125 calculates an internal impedance (Z = V / I) for each of a plurality of frequencies obtained by the discrete Fourier transform.

  FIG. 3 is a graph showing waveforms of the current I satisfying the first condition and the synchronized inter-terminal voltage V. The current I shown in FIG. 3 is a relatively low-frequency pulse wave having a discharge pulse width of about 5 seconds and a state after interruption of discharge lasts for about 5 seconds. Since the pulse wave is composed of a composite sine wave whose first term is a sine wave of about 0.1 Hz, an accurate internal impedance can be obtained at a low frequency around 0.1 Hz.

  The arithmetic unit 125 estimates the equivalent circuit constant of the storage cell having the previously calculated internal impedance characteristic indicated by the solid line in FIG. 4 by curve fitting. The equivalent circuit constant is estimated by curve fitting based on an optimal solution search algorithm such as a gradient method, a discovery method, or a direct method.

As shown in FIG. 9, the equivalent circuit of the storage cell is composed of resistors R1, R2, R3 and capacitors C2, C3 and CPE. Note that the impedance of CPE is represented by 1 / T (jω) ^p . Therefore, the equivalent circuit constants R1, R2, R3, C2, C3, T (CPE constant), and p (CPE index) are estimated by the calculation unit 125 performing curve fitting. Note that the initial value of the constant is arbitrary. However, it is desirable to use constants in the characteristics of the storage cell before deterioration.

  4 is a Nyquist diagram showing an actual internal impedance characteristic of the storage cell indicated by a cross point, and an internal impedance characteristic indicated by a solid line calculated based on the current I and the inter-terminal voltage V shown in FIG. As shown in FIG. 4, the internal impedance on the low frequency side is calculated with high accuracy, but the calculation accuracy of the internal impedance on the high frequency side is low. For this reason, in the present embodiment, the calculation unit 125 subsequently reads the data of the voltage V between the terminals and the data of the current I while satisfying the second condition from the data storage unit 123, Discrete Fourier transform is performed on each data of the current I. Further, the calculation unit 125 calculates an internal impedance (Z = V / I) for each of a plurality of frequencies obtained by the discrete Fourier transform.

  FIG. 5 is a graph showing each waveform of the current I satisfying the second condition and the synchronized voltage V between the terminals. The current I shown in FIG. 5 has a discharge pulse width of about 0.05 seconds (= 50 milliseconds), and the state after the discharge interruption continues for about 0.95 seconds. The calculation unit 125 extracts data for 0.1 seconds from the beginning in order to derive the internal impedance characteristics on the high frequency side. Since the relatively high-frequency pulse wave indicated by the extracted data is composed of a composite sine wave whose first term is a sine wave of 10 Hz, an accurate internal impedance can be obtained at a high frequency around 10 Hz. Therefore, the arithmetic unit 125 combines the previously calculated low-frequency internal impedance and the high-frequency internal impedance calculated this time. 6 is calculated based on the actual internal impedance characteristic of the storage cell indicated by the cross point, the low frequency side of the internal impedance characteristic indicated by the solid line in FIG. 4, the current I and the inter-terminal voltage V shown in FIG. It is a Nyquist diagram which shows the internal impedance characteristic which synthesize | combined the high frequency side of the internal impedance characteristic.

  As described above, the CPE variable component is dominant in the internal impedance of the frequency of 1 Hz or less. The arithmetic unit 125, while maintaining the T and p related to the CPE constant among the equivalent circuit constants of the storage cell having the internal impedance characteristic calculated earlier indicated by the solid line in FIG. R2, R3, C2, and C3 are estimated again by curve fitting. The calculation unit 125 sends the equivalent circuit constants R1, R2, R3, C2, C3, T, and p of the storage cell estimated in this way to the assembled battery state management unit 15.

  As described above, according to the present embodiment, the internal impedance characteristics of the storage cell are derived based on the current I and the inter-terminal voltage V obtained during the low-frequency pulse discharge, and during the high-frequency pulse discharge. It is also derived based on the obtained current I and inter-terminal voltage V. In addition, when estimating the equivalent circuit constant that is fitted to the curve indicated by the internal impedance characteristics of the storage cell, the constant (T, p) related to the CPE that is predominantly involved on the low frequency side and the dominant on the high frequency side. The constants (R1, R2, R3, C2, C3) involved in are specified stepwise. As described above, the estimated value of the equivalent circuit constant of the storage cell is derived from the internal impedance characteristics in an appropriate frequency band. As a result, the equivalent circuit constant of the storage cell can be estimated with high accuracy.

  In the above description, first, among the equivalent circuit constants of the storage cell estimated after obtaining the internal impedance characteristics based on the current I and the inter-terminal voltage V obtained during the low-frequency pulse discharge, the constants related to the CPE After specifying (T, p), the remaining constants (R1, R2, R3, C2, C3) are specified based on the synthesized internal impedance characteristics described above. However, first, some of the equivalent circuit constants (R1, R2, R2, R2, R2) of the equivalent circuit constants of the storage cell estimated after obtaining the internal impedance characteristics based on the current I and the inter-terminal voltage V obtained during high-frequency pulse discharge. After specifying R3, C2, and C3), the constant (T, p) related to CPE may be specified based on the synthesized internal impedance characteristics described above.

  Further, in the above description, when calculating the internal impedance of the storage cell, discrete Fourier transform is performed on each data of the voltage V and current I between the terminals at the time of low frequency pulse discharge and at the time of high frequency pulse discharge. However, the equivalent circuit constant of the storage cell may be estimated by performing Laplace conversion on each of the terminal voltage V and current I during low-frequency pulse discharge and high-frequency pulse discharge. .

  In the above description, the discharge current is described as an example of the current I detected by the current sensor 19, but the charging current to the assembled battery 11 may be the current I.

INV inverter MOT motors C1, C2,... Cn battery cell 11 assembled batteries 13, 131, 132,... 13n cell impedance calculation unit 15 assembled battery state management units 171, 172, ... 17n voltage sensor 19 current sensors 101v, 101i low-pass filter ( LPF)
103v, 103i AD converter (ADC)
105 Clock Generation Unit 107 Control Unit 109 Condition Storage Unit 111 Equivalent Circuit Constant Calculation Unit 121 Current Waveform Analysis Unit 123 Data Storage Unit 125 Calculation Unit

Claims (3)

A storage battery characteristic deriving device for deriving an equivalent circuit constant of a storage battery,
A current waveform analyzer for analyzing a waveform of a charge / discharge current at the time of a pulsed transient response of the storage battery;
Based on each data of the charging / discharging current of the storage battery and the voltage at both ends when the waveform of the charging / discharging current analyzed by the current waveform analysis unit satisfies the first condition, an equivalent circuit constant of a part of the storage battery is derived. The other equivalent circuit constants of the storage battery are derived based on the data of the charge / discharge current of the storage battery and the voltage at both ends when the waveform of the charge / discharge current analyzed by the current waveform analysis unit satisfies the second condition. A constant derivation unit,
The equivalent circuit constant of the storage battery is a first constant that is dominant in the frequency at the time of transient response when the first condition is satisfied and a frequency that is dominant in the frequency at the time of transient response when the second condition is satisfied. Including two constants,
The storage battery characteristic deriving device, wherein the pulse width and pulse frequency at the time of transient response when satisfying the first condition are different from the pulse width and pulse frequency at the time of transient response when satisfying the second condition, respectively. . The storage battery characteristic deriving device according to claim 1,
The constant derivation unit calculates the internal impedance of the storage battery for each frequency from a value obtained by frequency-converting each data of the charge / discharge current and both-end voltage of the storage battery, and derives the internal impedance characteristic of the storage battery, An apparatus for deriving storage battery characteristics, wherein an equivalent circuit constant of the storage battery is derived based on the derived internal impedance characteristics. The storage battery characteristic deriving device according to claim 2,
The constant deriving unit is derived based on the internal impedance characteristics of the storage battery derived from values obtained by frequency-converting each data of the charging / discharging current and both-end voltage of the storage battery when the first condition is satisfied. The internal impedance characteristics of the storage battery derived from the values obtained by frequency-converting the data of the charge / discharge current and the voltage at both ends of the storage battery when the second condition is satisfied while the first constant is a fixed value A storage battery characteristic deriving device, wherein the second constant is derived based on a characteristic obtained by combining the internal impedance characteristic derived previously and the internal impedance characteristic.

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