JP5924516B2 - Battery impedance measuring device - Google Patents

Description

  The present invention relates to a battery impedance measuring device used for a battery monitoring device, and more specifically, in real time, the impedance of a battery is measured on-site (site) such as an automobile, a power plant, or a household power storage system that actually uses the battery. It is related with the battery impedance measuring device which can be measured by.

  Rechargeable secondary batteries can be used as driving motor drive power sources for hybrid and electric vehicles, and can store energy with relatively little environmental impact, such as solar and wind power generation that does not rely on fossil fuels. From the point of view, it is also being widely used in industry, public institutions and general households.

  Generally, these secondary batteries are configured as battery modules that can obtain a desired output voltage by connecting a predetermined number of battery cells in series, and a predetermined number of battery modules that can obtain a desired output voltage are connected in parallel. Thus, the battery pack is configured to obtain a desired current capacity (AH).

  By the way, secondary batteries mounted on automobiles as driving motor drive power sources are considered to be mainly lithium ion batteries for the time being because of convenience such as charging time and cruising distance.

FIG. 15 is a block diagram showing an example of a battery system using a conventional secondary battery. In FIG. 15, the battery module 10 includes a plurality of battery cells 11 _{1 to} 11 _n and a current sensor 12 connected in series, and is connected in series with a load L.

The battery impedance measuring device 20 includes a plurality of A / D converters 21 _{1 to} 21 _{n +} provided to individually correspond to the plurality of battery cells 11 _{1 to} 11 _n and the current sensor 12 constituting the battery module 10. ₁ and a processing device 23 to which the output data of these A / D converters 21 _{1 to} 21 _{n + 1} are input via the internal bus 22.

The output voltage of each battery cell 11 _{1 to} 11 _n of battery module 10 and the detection signal of current sensor 12 are respectively input to corresponding A / D converters 21 _{1 to} 21 _{n + 1} and converted into digital signals. Output data of the A / D converters 21 _{1 to} 21 _{n + 1} is input to the processing device 23 via the internal bus 22.

The processing device 23 obtains, for example, internal resistance values of the battery cells 11 _{1 to} 11 _n based on output data of the A / D converters 21 _{1 to} 21 _{n + 1} and extracts a desired current from the internal resistance values. In this case, the voltage drop is estimated, and these data are transmitted to the upper battery system control unit 40 via the external bus 30.

  The battery system control unit 40 controls the battery module 10 and the load device L so that the load device L can be stably driven with the current output voltage of the battery module 10 based on the data input from the battery impedance measuring device 20. .

  One index for evaluating the performance of the secondary battery constituting such a battery module 10 is an internal impedance characteristic as shown in FIGS. 16 and 17. FIG. 16 is an example of impedance characteristics when a fully charged battery is left in a high temperature state, and FIG. 17 is an example of impedance characteristics when charging and discharging are repeated in a high temperature state. 16 and 17, the left diagram shows a Cole-Cole plot in which complex impedance based on the AC impedance measurement result is plotted in complex coordinates, and the right diagram shows a Bode diagram representing the impedance frequency characteristic.

  The left diagram of FIG. 16 shows a process in which the AC impedance increases as the leaving period becomes longer, for example, 1 year, 2 years,. The left diagram of FIG. 17 shows a process in which the AC impedance increases as charge / discharge is repeated, for example, 50 times, 100 times,.

  When the impedance increases, the battery voltage drop when taking out the current increases, and a sufficient output voltage cannot be obtained. The part with the low frequency in each figure on the right corresponds to continuing to step on the accelerator of the automobile for a long time. From these data, it can be inferred that the voltage drop increases steadily because the impedance increases at the low frequency part. That is, the output characteristics change as the battery deteriorates, and a sufficient output cannot be taken out.

  FIG. 18 is a block diagram showing an example of a conventional measurement circuit for measuring the AC impedance of the secondary battery, and the same reference numerals are given to portions common to FIG. In FIG. 18, a sweep signal generator 50 is connected to both ends of a series circuit of a battery 10 and a current sensor 12. The sweep signal generator 50 outputs an AC signal whose output frequency sweeps and changes in a range including the frequency characteristic region shown in the right diagrams of FIGS. 16 and 17 to the series circuit of the battery 10 and the current sensor 12.

  The AC voltage monitor 60 measures the AC voltage across the battery 10 and inputs it to the impedance calculation device 80. The alternating current monitor 70 measures the alternating current flowing through the current sensor 12 and inputs it to the impedance calculation device 80.

  The impedance calculation device 80 calculates the complex impedance of the battery 10 that is the ratio of the measured voltage of the AC voltage monitor 60 and the measured current of the AC current monitor 70 at each frequency of the output signal of the sweep signal generator 50. By plotting these calculated complex impedances on the complex plane, a Cole-Cole plot as shown in FIGS. 16 and 17 can be obtained.

  From the Cole-Cole plot created in this way, for example, each parameter of the equivalent circuit of the battery 10 as shown in FIG. 19 can be estimated. In the equivalent circuit of FIG. 19, the DC power supply E, the resistor R1, the parallel circuit of the resistor R2 and the capacitor C2, the parallel circuit of the resistor R3 and the capacitor C3, and the parallel circuit of the resistor R4 and the inductance L4 are connected in series. Has been. Such impedance measurement by the AC method is described in detail in Patent Document 1 including an automatic measurement method.

Japanese Patent Laid-Open No. 2003-4780

  As described above, various information on the battery can be obtained by measuring the internal impedance characteristics of the battery. Therefore, on-site (such as automobiles, power plants, and household power storage systems that actually use the battery) If the internal impedance characteristics of the battery can be measured in the field), it is possible to grasp the current state of the battery based on the information and to control the battery so that it can be effectively utilized at all times according to the current state of the battery.

However, in the conventional system configuration shown in FIG. 15, although the internal resistance values of the battery cells 11 _{1 to} 11 _n can be obtained, data communication between the processing device 23 and the battery system control unit 40 is intermittent. Therefore, the voltage data of each of the battery cells 11 _{1 to} 11 _n becomes discrete data having a period of, for example, 100 ms or more.

As a result, voltage, current, remains to be able to detect a reference to the state of each battery cell 11 ₁ to 11 _n a table composed like temperature, information often jammed the battery cells 11 ₁ to The internal impedance characteristics of 11 _n cannot be measured.

  Further, according to the conventional measurement circuit shown in FIG. 18, the sweep signal generator 50 is necessary, and the implementation of the measurement circuit as shown in FIG. 18 for each on-site cell is realized in terms of cost and space. It is difficult.

  The present invention solves these problems, and an object of the present invention is to provide an interior of a battery used in a battery monitoring device on-site such as an automobile, a power plant, or a household power storage system that actually uses the battery. The object is to realize a battery impedance measuring apparatus capable of measuring impedance characteristics in real time.

In order to achieve such an object, the invention described in claim 1 of the present invention is:
A plurality of battery cells connected in series, an impedance measuring device used in a battery monitoring device that measures and monitors a battery module that drives an actual load in a state that causes a load fluctuation including a high frequency range in real time,
A discrete Fourier transform of the voltage waveform data and current waveform data of each cell, and a DFT operation unit that calculates impedance by dividing the discrete Fourier transform result of the voltage waveform data by the discrete Fourier transform result of the current waveform data;
Based on the analysis conditions including the impedance calculated by the DFT calculation unit, the weighting function, and the frequency range , weighting is performed on the difference between the measured impedance and the impedance at the same frequency obtained from the circuit constant, and the voltage waveform of each cell Alternatively, a circuit constant estimation calculation unit that reduces weighting in a frequency region where the amplitude of the current waveform is small and increases weighting in a frequency region where the amplitude of the voltage waveform or current waveform of each cell is large ,
It is comprised by these.

The invention of claim 2
A plurality of battery cells connected in series, an impedance measuring device used in a battery monitoring device that measures and monitors a battery module that drives an actual load in a state that causes a load fluctuation including a high frequency range in real time,
A spike data correction unit that performs spike correction on the voltage waveform data and current waveform data of each cell;
A DFT operation unit that calculates the impedance by subjecting the voltage waveform data and current waveform data of each cell subjected to spike correction to discrete Fourier transform, and dividing the discrete Fourier transform result of the voltage waveform data by the discrete Fourier transform result of the current waveform data When,
Based on the analysis conditions including the impedance calculated by the DFT calculation unit, the weighting function, and the frequency range , weighting is performed on the difference between the measured impedance and the impedance at the same frequency obtained from the circuit constant, and the voltage waveform of each cell Alternatively, a circuit constant estimation calculation unit that reduces weighting in a frequency region where the amplitude of the current waveform is small and increases weighting in a frequency region where the amplitude of the voltage waveform or current waveform of each cell is large ,
It is comprised by these.

  As a result, the internal impedance characteristics of the battery can be measured and the battery state can be monitored in real time at an on-site site such as an automobile, a power plant or a household power storage system that actually uses the battery.

It is a block diagram which shows the specific example of the battery monitoring apparatus with which the battery impedance measuring apparatus based on this invention is used. 4 is a block diagram illustrating a specific example of a power / impedance calculation unit 24. FIG. It is a sample impedance characteristic example figure. It is a characteristic example figure of the rectangular wave pulse f (t). It is explanatory drawing which shows the specific example of weighting. It is explanatory drawing which shows the example of a result estimated constant by weighting. It is a block diagram which shows one Example of this invention. It is a response measurement example figure of a constant current pulse. It is a Nyquist plot example figure. FIG. 20 is an explanatory diagram of a measurement result of each circuit constant in the equivalent circuit of FIG. 19 and an impedance characteristic curve for fitting calculated based on the measurement result. It is a comparative example figure of the sample impedance characteristic by the presence or absence of spike detection. It is a block diagram which shows the other Example of this invention. It is a flowchart explaining the flow of the process for correct | amending an inductance L component. FIG. 14 is an explanatory diagram illustrating an example of a result of equivalent circuit fitting of waveform data with spikes corrected by the procedure of the flowchart of FIG. 13. It is a block diagram which shows an example of the battery system using the conventional secondary battery. It is an impedance characteristic example figure at the time of leaving the fully charged battery in a high temperature state. It is an impedance characteristic example figure when charging / discharging is repeated in a high temperature state. It is a block diagram which shows an example of the conventional measurement circuit which measures the alternating current impedance of a secondary battery. It is an equivalent circuit example figure of a battery.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a specific example of a battery monitoring apparatus in which a battery impedance measuring apparatus according to the present invention is used, and parts common to FIG. In FIG. 1, a battery impedance measuring device 20 includes a plurality of n power / impedance calculation units 24 _{1 to} 24 provided corresponding to a plurality of n battery cells 11 _{1 to} 11 _n constituting the battery module 10. _n , the battery module state management unit 26 to which the output data of the power / impedance calculation units 24 _{1 to} 24 _n are input via the internal bus 25, and the accelerator constituting the driving system of the automobile as the load device L And an accelerator work monitoring unit 27 that monitors the movement of L1.

  In the drive system of the automobile as the load device L, an accelerator L1, an inverter L2, and a motor L3 are substantially connected in series. The inverter L2 is connected in series with the battery module 10 and is supplied with driving power necessary for rotationally driving the motor L3 from the battery module 10. The motor L3 is controlled so as to rotate at a rotational speed intended by the driver by controlling the amount of driving power supplied to the inverter L2 in accordance with the movement of the accelerator L1 operated by the driver, for example.

The movement of the accelerator L1 accompanying the driver's pedal operation is continuously monitored and detected by the accelerator work monitoring unit 27, and the detection signal is calculated by each power / impedance calculation via the battery module state management unit 26 and the internal bus 25. Are input to the units 24 _{1 to} 24 _n .

The power / impedance calculators 24 _{1 to} 24 _n receive voltage signals from the corresponding battery cells 11 _{1 to} 11 _n and current signals from the current sensor 12.

Here, the movement of the accelerator L1 due to the driver's pedal operation is such that the output voltage waveform of each of the battery cells 11 _{1 to} 11 _{n and} the output current waveform of the current sensor 12 rise in a staircase wave including a broadband frequency component. It will give a fall change.

The power / impedance calculation units 24 _{1 to} 24 _n perform discrete Fourier transform (DFT) or fast Fourier transform (FFT) on the waveform data including these broadband frequency components, and based on the result, an equivalent circuit in a desired frequency domain. Estimate a constant. As a result, the internal impedance characteristics of the battery can be measured on-site such as in an automobile or a plant that actually uses the battery, and the battery state can be monitored in real time.

The battery module state management unit 26 captures instantaneous power information and internal impedance information of each of the battery cells 11 _{1 to} 11 _n constituting the battery module 10 measured by the power / impedance calculation units 24 _{1 to} 24 _n , and Is transmitted to the host battery system control unit 40 via the external bus 30.

The battery system control unit 40 controls the battery module 10 and the load device L so that the load device L can be stably driven with the current output voltage of the battery module 10 based on the data input from the battery impedance measuring device 20. Based on the trend of changes in the instantaneous energy consumption of each battery cell 11 _{1 to} 11 _n and the change trend of internal impedance information, the performance status of each battery cell 11 _{1 to} 11 _n is grasped, and an alarm for encouraging charging is transmitted. Or by analyzing the tendency of performance deterioration and outputting the replacement time prediction data of the battery module 10.

FIG. 2 is a block diagram illustrating a specific example of the power / impedance calculation unit 24. In FIG. 2, the voltage signal V of each battery cell 11 _{1 to} 11 _n is input to the A / D converter 24b via the anti-aliasing filter 24a, and the output data of the A / D converter 24b is equivalent circuit parameter measuring unit 24c. Is input.

  The current signal I from the current sensor 12 is input to the A / D converter 24e via the antialiasing filter 24d, and the output data of the A / D converter 24e is input to the equivalent circuit parameter measurement unit 24c.

  The A / D converters 24b and 24e are configured by a battery module state management unit 26 → accelerator change amount detection unit 24f → clock control unit 24g → variable clock generation unit 24h, and an accelerator change detected and output from the accelerator work monitoring unit 27. It is driven by a variable clock system generated based on the signal. As a result, clocks based on the driver's accelerator work such as start, acceleration, high speed driving, low speed driving, deceleration, stop, reverse, and their speed are generated, and the voltage signal V and current signal I in each state are generated. Converted to digital data.

Note that the sampling clock frequency of the A / D converters 24b and 24e can be changed according to the frequency band in which the internal impedance of each of the battery cells 11 _{1 to} 11 _n is to be measured. For example, when measuring the internal impedance up to 1 kHz, the sampling clock frequency is set to 2 Ksample / s, and the low-pass bands of the antialias filters 24 a and 24 d are set to 1 kHz or less.

The equivalent circuit parameter measurement unit 24c is connected to an equivalent circuit information storage unit 24i that stores information on equivalent circuits such as equivalent circuit patterns of the battery cells 11 _{1 to} 11 _n to be measured. Each parameter of the equivalent circuit measured by the equivalent circuit parameter measurement unit 24 c is taken into the battery module state management unit 26 via the internal bus 25.

The output data of the A / D converters 24b and 24e is also input to the power measuring unit 24j. Thereby, the power measurement unit 24j measures the instantaneous power of each of the battery cells 11 _{1 to} 11 _n and stores the measurement result in the power information storage unit 24k. The power information stored in the power information storage unit 24k is taken into the battery module state management unit 26 via the internal bus 25.

  In recent years, research has been conducted to determine the impedance characteristics by applying a sine wave at a constant voltage or constant current to a battery, and estimating the battery characteristics by estimating the temperature characteristics of charge / discharge, the remaining charge level, and the degree of performance deterioration. It is actively done.

  When the impedance characteristic is obtained from a sweep measurement of a single sine wave, the amplitude considering the A / D resolution of the A / D converter can be set for each frequency unit. On the other hand, in the case of a waveform including a plurality of frequency components such as a pulse, the amplitude of each frequency component cannot be controlled. In this case, at a certain frequency component, the A / D resolution is insufficient and correct impedance cannot be obtained. Furthermore, if the constant estimation of the equivalent circuit model is performed using this data, an estimation result with a large error may be obtained.

  In the sample data of FIG. 3, (A) is an impedance characteristic curve obtained from an impedance characteristic obtained from a sinusoidal waveform input response corresponding to the equivalent circuit of FIG. 19 and a constant fitting. The sine wave is swept in a frequency range of 1 Hz to 2.5 kHz and measured while securing a sufficient sample rate at each measurement frequency point. These circuit constants are assumed to be true values.

  (B) is the result obtained from the pulse input response. However, R4 and L4 are constants obtained by a sinusoidal waveform input response. Measurement is performed at a sample rate of 1 kHz, and discrete Fourier transform is performed in a frequency range of 1 to 450 Hz. Since the sample rate is low, the inductance component that should be seen on the high frequency side is not captured. Moreover, the results vary as the frequency increases. These variations are considered to be related to the amplitude of each frequency component included in the pulse and the A / D resolution of the A / D converter.

  Here, a square wave pulse f (t) is expanded in a Fourier series, and frequency components included in the waveform are considered. The rectangular wave pulse f (t) can be expressed as shown in FIG.

However, W is a pulse width, T is a period, and m is an integer of 0 or more.
As shown in the above equation, depending on the frequency, the amplitude am becomes extremely small with respect to the A / D resolution, and the result may vary greatly in the vicinity of this frequency.

  This variation may impair the estimation accuracy of the equivalent circuit constant, but some weighting calculation is considered effective in order to suppress the influence of the variation.

  As a specific example, consider the case where the Gauss-Newton method is used to estimate circuit constants. If the deviation from the true value of the circuit constant is ΔR2, ΔC2, ΔR3, ΔC3, it can be expressed as follows.

  ΔZn is the difference between the nth actually measured impedance and the impedance at the same frequency obtained by calculation from the current circuit constant. J represents the Jacobian, and T represents the transpose of the matrix. The above calculation is repeated until the circuit constants converge. Here, the weighting p (j) is introduced, and the circuit constant estimation calculation is performed by the following equation.

  By reducing the weighting in the frequency range where the amplitude is small and conversely increasing the weighting in the frequency region where the amplitude is large, an effect of suppressing the influence of variation can be expected.

When the input response has a shape close to a pulse, for example, weighting as shown in FIG. 5 is considered effective from the nature of the Fourier series. Here, k is an integer greater than or equal to ₀ , f ₀ is a frequency when the DFT calculation section is one cycle, and f _j is a j-th order frequency of f ₀ .

  FIG. 6 is an explanatory diagram showing an example of the result of constant estimation by the above weighting. (A) shows an example diagram of sample impedance characteristics, and (B) shows the deviation of the constant from the true value when estimated with and without weighting. All constants are constant estimation results close to true values.

  FIG. 7 is a block diagram showing an embodiment of the present invention having a weighting calculation function, and shows a specific example of an equivalent circuit parameter measurement unit 24c constituting the power / impedance calculation unit 24 of FIG. The output data of the A / D converters 24b and 24e are sequentially stored in the waveform data storage unit c1.

  The DFT operation unit c2 performs discrete Fourier transform on the waveform data of the voltage signal and current signal sequentially stored in the waveform data storage unit c1, and divides the result of discrete Fourier transform of the voltage signal by the result of discrete Fourier transform of the current signal. The impedance is calculated, and the calculated impedance data is stored in the impedance data storage unit c3. Depending on the form of the waveform data, the FFT processing unit can be used in place of the DFT calculation unit c2 to speed up the calculation process.

  The circuit constant estimation calculation unit c4 performs weighting calculation of each data based on the impedance data stored in the impedance data storage unit c3 and the weighting function and frequency range set from the analysis condition storage unit c5.

  As described above, in the process of performing the estimation calculation by the circuit constant estimation calculation unit c4, it is possible to improve the constant estimation accuracy by weighting each data according to the conditions such as the frequency domain and the measurement accuracy.

  When a current (voltage) with a fast pulse rise is applied to a battery having a large inductance component, a spike-like voltage (current) is generated. At this time, if the sample rate of the A / D converter is not sufficiently high, the spike portion may be sampled or not sampled as shown in FIG. 8 depending on the sample timing.

  FIGS. 8A and 8B are diagrams of measurement examples of constant current pulse responses. FIG. 8A shows a case where the voltage spike portion is sampled, and FIG. 8B shows a case where the voltage spike portion is not sampled.

  When calculating the impedance of the battery, the calculation result of the impedance is significantly different between the case where the spike portion is sampled and the case where the spike portion is not sampled, and a non-reproducible result is obtained.

  FIG. 9 is an example diagram of a Nyquist plot obtained from each data. “−Δ−” is a result obtained from a sine waveform input. As described above, this is a result of measuring each frequency one by one while securing a sufficient sample rate. Note that since the sine waveform is sufficiently smooth, a spike response as seen with a pulse input does not occur. Hereinafter, the result of “−Δ−” is regarded as a true value.

  “-□-” is a result of performing a discrete Fourier transform on data in which spikes are detected. Since there is not enough sunplate to capture the spike part, it is far from the true value of “-△-” as a whole.

  “− × −” is the result of performing a discrete Fourier transform on data for which no spike was detected. Since the spike portion was not captured, it does not extend downward with respect to the imaginary axis direction, and the inductance component is missing. From these, it is clear that the appearance of the characteristics is remarkably different between the case where the spike is detected and the case where the spike is not detected.

  The inductance of a battery is structurally determined, and there is an idea that it does not change with time due to electrode or solution deterioration. As described above, the spike is caused by the inductance of the battery. However, in the deterioration diagnosis of the battery, only the R and C components are required, and the L component may not be measured. In such a case, if the information on the negative side (upper part of the graph) of the imaginary axis of the graph is accurate and sufficient, the R (resistance) and C (conductance) of the battery can be estimated and the deterioration of the battery can be diagnosed.

  FIG. 10 shows impedance characteristics measured by sweeping a sine wave in a predetermined frequency range of 1 Hz to 2.5 kHz and securing a sufficient sample rate at each measurement frequency point, and this is expressed as a constant in the equivalent circuit model of FIG. It is an impedance characteristic curve derived from constants R1, R2, R3, C2, C3, L4, R4 obtained by fitting. Hereinafter, these measurement results are assumed to be true values.

  FIG. 11 is a comparative example of sample impedance characteristics depending on the presence or absence of spike detection. (A) shows data in which spikes were detected in the pulse response, and (B) shows data in which spikes were not detected in the pulse response. However, R4 and L4 are excluded from the equivalent circuit model for data in which the inductance L component is not detected.

  (C) shows the deviation of each constant from the true value due to the presence or absence of spike detection. In R and C, a result close to the true value can be obtained by performing fitting based on data in which no spike is detected. In other words, even if the sample rate is insufficient, it is shown that it is possible to estimate the circuit constants of R and C sufficiently if the waveform has no spikes, but a waveform without spikes is obtained with good reproducibility. It is difficult.

  Therefore, it is considered to correct the data showing the L component from the pulse response data measured at the low sample rate and estimate the R and C of the equivalent circuit with high reproducibility and high accuracy.

  FIG. 12 is a block diagram showing another embodiment of the present invention having a spike correction function, and parts common to FIG. The spike data correction unit c7 in FIG. 12 performs spike correction on the waveform data stored in the waveform data storage unit c1. The circuit constant estimation calculation unit c4 estimates circuit constants by constant fitting based on spike-corrected impedance data stored in the impedance data storage unit c3 and analysis conditions set from the analysis condition storage unit c5. The impedance characteristic curve derived from the obtained constant is calculated. The calculation result of the circuit constant estimation calculation unit c4 is stored in the circuit constant storage unit c6.

  FIG. 13 is a flowchart for explaining the flow of processing for correcting the inductance L component of the waveform data with spikes by the spike data correction unit c7. In FIG. 13, i (t) is t-th current sampling data, and v (t) is t-th voltage sampling data. sr is a coefficient for detecting spikes. The trigger is a trigger level for detecting the rise and fall of the pulse.

  In step S1, waveform data having a data length of t = 1 is selected, and in step S2, it is determined whether or not i (t)> trigger condition is satisfied with T = t in order to determine whether or not the pulse rises. To do. If this condition is satisfied, it is determined that the pulse is rising, and the process proceeds to step S3 where T = t and flag = FALSE.

  In step S4, it is determined whether or not a condition of v (t)> sr * v (t + 1) is satisfied in order to determine whether or not a spike is detected. If this condition is satisfied, it is determined that a spike has been detected, and the process proceeds to step S5 where flag = TRUE, v (t) = v (t-1), and i (t) = i (t-1). . Subsequently, the process proceeds to step S6 for selecting waveform data having a data length of t = T. If the condition in step S4 is not satisfied, it is determined that there is no spike, and the process directly proceeds to step S6.

  In step S7, it is determined whether i (t) <trigger condition is satisfied or not in order to determine whether or not the pulse falls. If this condition is satisfied, it is determined that the pulse falls, and it is further determined in step S8 whether or not flag = TRUE to determine whether spike correction is performed. If this condition is satisfied, it is determined that spike correction is present, and the process proceeds to step S9 where v (t) = v (t-1) and i (t) = i (t-1), and a series of processes is performed. Exit. If the condition of step S8 is not satisfied, the series of processing is terminated with no spike correction.

  FIG. 14 is an explanatory diagram showing an example of the result of equivalent circuit fitting of waveform data with spikes corrected by the procedure of the flowchart of FIG. (A) shows an example diagram of sample impedance characteristics, and (B) shows a deviation from the true value of the constant before and after correction. The corrected constants are close to true values for all constants.

  The power / impedance calculation unit 24 used in the present invention can be packaged in an extremely small size by using a semiconductor integrated circuit technology. It is sufficient if space can be secured.

  Further, in each of the above embodiments, the example of measuring the internal impedance of each battery cell of the battery module mounted on the automobile has been described, but also for monitoring the storage battery provided in a power plant other than the automobile, a household power storage system, etc. It is valid.

  As described above, according to the battery impedance measuring apparatus of the present invention, the internal impedance characteristics of the battery are measured on-site such as an automobile, a power plant, or a household power storage system that actually uses the battery. A battery monitoring device that can monitor the state in real time can be realized.

24c Equivalent circuit parameter measurement unit c1 Waveform data storage unit c2 DFT calculation unit c3 Impedance data storage unit c4 Circuit constant estimation calculation unit c5 Analysis condition storage unit c6 Circuit constant storage unit c7 Spike data correction unit

Claims (2)

A plurality of battery cells connected in series, an impedance measuring device used in a battery monitoring device that measures and monitors a battery module that drives an actual load in a state that causes a load fluctuation including a high frequency range in real time,
A discrete Fourier transform of the voltage waveform data and current waveform data of each cell, and a DFT operation unit that calculates impedance by dividing the discrete Fourier transform result of the voltage waveform data by the discrete Fourier transform result of the current waveform data;
Based on the analysis conditions including the impedance calculated by the DFT calculation unit, the weighting function, and the frequency range , weighting is performed on the difference between the measured impedance and the impedance at the same frequency obtained from the circuit constant, and the voltage waveform of each cell Alternatively, a circuit constant estimation calculation unit that reduces weighting in a frequency region where the amplitude of the current waveform is small and increases weighting in a frequency region where the amplitude of the voltage waveform or current waveform of each cell is large ,
And a battery impedance measuring device. A plurality of battery cells connected in series, an impedance measuring device used in a battery monitoring device that measures and monitors a battery module that drives an actual load in a state that causes a load fluctuation including a high frequency range in real time,
A spike data correction unit that performs spike correction on the voltage waveform data and current waveform data of each cell;
A DFT operation unit that calculates the impedance by subjecting the voltage waveform data and current waveform data of each cell subjected to spike correction to discrete Fourier transform, and dividing the discrete Fourier transform result of the voltage waveform data by the discrete Fourier transform result of the current waveform data When,
Based on the analysis conditions including the impedance calculated by the DFT calculation unit, the weighting function, and the frequency range , weighting is performed on the difference between the measured impedance and the impedance at the same frequency obtained from the circuit constant, and the voltage waveform of each cell Alternatively, a circuit constant estimation calculation unit that reduces weighting in a frequency region where the amplitude of the current waveform is small and increases weighting in a frequency region where the amplitude of the voltage waveform or current waveform of each cell is large ,
And a battery impedance measuring device.