JP2004132797A - Method and apparatus for measuring internal impedance of storage battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for measuring the internal impedance of a storage battery without increasing costs in the measurement of electromotive force component to be measured buried in a noise component. <P>SOLUTION: In the method for measuring the internal impedance of the storage battery, the internal impedance of each storage battery of a group of storage batteries to which a plurality of storage batteries are connected in series is measured by using an AC current generation means and an AC voltage measurement means. The method includes a process of substantially setting the waveform of an AC current generated by the AC current generation means to be a sinusoidal wave and a process of treating each of an AC electromotive force component generated at both the ends of the storage battery whose internal impedance is to be measured and that generated at both the ends of a measurement current detection means connected to the AC current generation means in series by a common analog filter and then by a common digital filter. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for measuring the internal impedance of a storage battery.
[0002]
[Prior art]
As a method for measuring the internal impedance of each storage battery of a storage battery group in which a large number of storage batteries are connected in series, a so-called AC four-terminal method is known.
[0003]
The AC four-terminal method is to obtain an internal impedance of a storage battery by passing an alternating current through the storage battery whose internal impedance is to be measured and measuring the generated electromotive force.
[0004]
FIG. 5 shows a principle diagram of the internal impedance measurement of the storage battery by the AC four-terminal method. In FIG. 5, 1 is a storage battery, 2 is a storage battery group, 3 is an alternating current generating means, 4 is an alternating voltage measuring means, and the alternating current generating means 3 and the alternating voltage measuring means 4 are connected in parallel with the storage battery 1. .
[0005]
Here, the storage battery group 2 is a group in which a plurality of storage batteries 1 are connected in series in order to obtain a target voltage value. For example, in the case of a lead storage battery, the electromotive force per storage battery is about 2 V, and six of these are connected in series to obtain an electromotive force of about 12 V, etc., as defined in this specification as storage battery group 2 doing.
[0006]
The alternating current generating means 3 generates an alternating current (denoted as a measurement current in this specification) for measuring the internal impedance of the storage battery 1. The AC current generating means 3 functions as, for example, an AC constant current source, and has an infinite internal impedance in principle.
[0007]
The AC voltage measuring means 4 measures the electromotive force generated in the storage battery 1 by the measurement current generated by the AC current generating means 3. This AC voltage measuring means 4 functions as, for example, an AC voltmeter, and the internal impedance is infinite in principle.
[0008]
By the way, in general, the value of the internal impedance of the storage battery 1 is often 5 mΩ or less, and it is necessary to flow a large measurement current in order to increase the measurement accuracy of the internal impedance.
[0009]
In addition, the storage battery group 2 is often used as a backup for a power supply device. In this case, a ripple current of 50 Hz or 60 Hz, which is the frequency of the commercial power supply, and a harmonic component of the frequency of the commercial power supply is supplied to the storage battery 1. In some cases, the AC electromotive force component due to the measurement current is buried in the AC electromotive force component due to the noise component such as the ripple current, and the measurement accuracy of the internal impedance is greatly reduced.
[0010]
By the way, when measuring the internal impedance of a storage battery, the method of measuring the to-be-measured electromotive force which generate | occur | produced in the storage battery by a synchronous detection means is known (patent document 1). This technique uses a periodicity of the measured electromotive force component to remove a noise component that does not match the cycle of the measured electromotive force component.
[0011]
[Patent Document 1]
JP 2000-502177 A (refer to claim 13, claim 26, specification page 12 line 2 to page 19 line 27)
[0012]
[Problems to be solved by the invention]
However, a circuit and a device for performing synchronous detection are generally complicated and cause an increase in cost when measuring the internal impedance of the storage battery.
[0013]
Accordingly, an object of the present invention is to provide a technique for measuring the internal impedance of a storage battery without incurring an increase in cost when measuring a measured electromotive force component buried in a noise component.
[0014]
[Means for Solving the Problems]
The invention of claim 1 is a storage battery internal impedance measurement method for measuring internal impedance of each storage battery of a storage battery group in which a plurality of storage batteries are connected in series using an alternating current generation means and an alternating voltage measurement means. The waveform of the alternating current generated by the generating means is substantially a sine wave, the measured electromotive force component generated at both ends of the storage battery to be measured for internal impedance, and both ends of the measuring current detecting means connected in series to the alternating current generating means Each of the AC electromotive force components generated in the above is processed by an analog filter having substantially the same characteristics, and then processed by a digital filter having substantially the same characteristics.
[0015]
According to a second aspect of the present invention, in the first aspect of the present invention, the measured electromotive force component generated at both ends of the storage battery to be measured for internal impedance and the AC electromotive force component generated at both ends of the measured current detecting means are shared. The method includes a step of processing with a common digital filter after processing with an analog filter.
[0016]
The invention of claim 3 is an internal impedance measuring device for a storage battery having an alternating current generating means and an alternating voltage measuring means for measuring the internal impedance of each storage battery of a storage battery group in which a plurality of storage batteries are connected in series. A measuring current detecting means is connected in series to the alternating current generating means, the waveform of the alternating current generated by the alternating current generating means is substantially a sine wave, and the alternating voltage measuring means is a single analog filter. An analog signal processing means, a digital signal processing means including a single digital filter, and an input switching means for switching an input to the analog signal processing means.
[0017]
That is, according to the present invention, when measuring the internal impedance of the storage battery, the waveform of the alternating current generated by the alternating current generating means is substantially a sine wave, and the measured electromotive force component generated at both ends of the storage battery to be measured for internal impedance and the above A digital filter having substantially the same characteristics after each of the AC electromotive force components generated at both ends of the measurement current detecting means connected in series to the AC current generating means is processed by an analog filter having substantially the same characteristics Therefore, the influence of noise components other than the frequency component of the alternating current generated by the alternating current generating means is minimized compared to the case where the synchronous detection means is used or the case where only the digital filter is used. Can be realized at a very low cost, and the cost of measuring the measured electromotive force component buried in the noise component can be reduced. It can be measured internal impedance of the battery without causing the flop.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings.
[0019]
FIG. 1 is a block diagram showing an outline of a storage battery internal impedance measuring apparatus according to an embodiment of the present invention. In FIG. 1, 1 is a storage battery, 2 is a storage battery group, 3 is an alternating current generating means, 4 is an alternating voltage measuring means, and the alternating current generating means 3 and the alternating voltage measuring means 4 are connected in parallel with the storage battery 1. The point is the same as in FIG. Further, in FIG. 1, a measurement current detection unit 5 is provided in series with the AC current generation unit 3, and an AC voltage measurement unit 4 is connected to both ends of the measurement current detection unit 5.
[0020]
As each storage battery 1 constituting the storage battery group 2, a lead storage battery or the like is used, but it is effective to use a sealed lead storage battery in which it is difficult to judge deterioration due to a change in liquid level or the like.
[0021]
As described above, the storage battery group 2 includes a plurality of storage batteries 1 connected in series in order to obtain a target voltage value. When the storage battery 1 is a lead storage battery having an electromotive force of about 2 V, six, twelve, and twenty-four can be connected in series to obtain electromotive forces of about 12 V, about 24 V, and about 48 V, respectively.
[0022]
As described above, the AC current generating means 3 generates an AC current (measurement current) for measuring the internal impedance of the storage battery 1 and functions as an AC constant current source. The alternating current generating means 3 may supply an alternating current to the storage battery 1 or may discharge the alternating current from the storage battery 1.
[0023]
By making the waveform of the alternating current generated by the alternating current generating means 3 substantially a sine wave, it is possible to measure the internal impedance of the storage battery 1 with less influence of harmonic components.
[0024]
As described above, the AC voltage measuring unit 4 measures the measured electromotive force generated in the storage battery 1 by the current generated by the AC current generating unit 3.
[0025]
The measurement current detection means 5 detects the alternating current generated by the alternating current generation means 3, and can use, for example, a resistor (shunt resistance) of about 0.1Ω. Further, since the AC voltage measuring means 4 is connected to both ends of the measurement current detecting means 5, the AC voltage measuring means 4 can be used for management of the measurement current.
[0026]
In FIG. 1, the AC voltage measuring unit 4 includes an analog signal processing unit 41, an A / D conversion unit 42, a digital signal processing unit 43, a storage unit 44, and an input switching unit 45.
[0027]
The analog signal processing means 41 has an analog filter function such as a band-pass filter that passes the same frequency as the frequency of the alternating current generated by the alternating current generating means 3, and an alternating current having a gain band at the frequency as necessary. Has an amplifier. The analog filter function can be easily obtained by using a circuit such as an active filter circuit in which a resistor and a capacitor are connected to an operational amplifier. The signal processed by the analog signal processing means 41 is sent to the A / D conversion means 42.
[0028]
The A / D conversion means 42 converts the signal from the analog signal processing means 41 from an analog signal to a digital signal. The signal processed by the A / D conversion means 42 is sent to the digital signal processing means 43.
[0029]
The digital signal processing means 43 performs digital filter processing in order to extract the same frequency as the frequency of the alternating current generated by the alternating current generating means 3 from the signal sent from the A / D conversion means 42. The digital signal processing unit 43 has a function of storing the digital filter processed signal in the storage unit 44 as a measurement result, and a function of controlling the input switching unit 45 based on the measurement procedure stored in the storage unit 44. Have. Further, it is desirable to have a function of sending a signal for controlling the alternating current generating means 3 to the alternating current generating means 3 based on the measurement procedure stored in the storage means 44.
[0030]
The digital signal processing means 43 has a function of calculating an internal impedance based on the measured current value and electromotive force data. The calculation result of the internal impedance is stored in the storage unit 44. If necessary, a means for displaying the calculation result of the internal impedance may be provided inside or outside the AC voltage measuring means 4.
[0031]
The storage unit 44 stores the processing result in the digital signal processing unit 43 and further stores a signal relating to the measurement procedure including a signal for controlling the input switching unit 45. It is desirable that the signal relating to the measurement procedure includes a signal for controlling the alternating current generating means 3.
[0032]
The input switching unit 45 switches a signal input to the analog signal processing unit 41 to the storage battery 1 side or the measured current detection unit 5. As the input switching means 45, for example, a relay (relay) is used, but other switching means can also be applied depending on the situation. When the input switching means 45 is connected to the storage battery 1, the AC voltage measurement means 4 measures the electromotive force of the storage battery 1, and when the input switching means 45 is connected to the measured current detection means 5, The AC voltage measuring unit 4 measures an electromotive force generated when the AC current generated by the AC current generating unit 3 flows to the measurement current detecting unit 5.
[0033]
In this embodiment, the AC voltage measuring means 4 is provided with an analog signal processing means 41 and a digital signal processing means 43. Since the analog signal processing means 41 has an analog filter function, for example, a sinusoidal wave generated by the AC current generating means 3 is used. When the frequency of the alternating current is 16 Hz, the 50 Hz or 60 Hz component, which is the frequency of the main component of noise from the power supply device (not shown) to which the storage battery group 2 is connected, can be suppressed by 20 dB or more in terms of voltage ratio. The noise component input to the digital signal processing means 43 can be efficiently suppressed.
[0034]
If the analog signal processing unit 41 is not used and the digital signal function of the digital signal processing unit 43 is used to achieve the same level of function as that of the present embodiment, the A / The D conversion means 42 is required. For example, in the case where the 12-bit A / D conversion means 42 is used in the present embodiment, the 16-bit or more A / D conversion means 42 having a resolution 10 times higher than that is required, and the A / D conversion means 42 is expensive. There is a problem of becoming.
[0035]
That is, according to the present embodiment, the sinusoidal frequency component generated by the alternating current generating means 3 is extracted while minimizing the influence of the noise component without increasing the resolution of the digital filter processing in the digital signal processing means 43. Can be realized at a very low cost. That is, the internal impedance of the storage battery can be measured without incurring a cost increase when measuring the measured electromotive force component buried in the noise component.
[0036]
Incidentally, as described above, the analog filter function of the analog signal processing means 41 includes a resistor and a capacitor, and the filter characteristics of the analog filter function may change depending on the temperature characteristics thereof. For example, the characteristic value of the analog signal processing means 41 designed to have a gain of 28.8 dB at a temperature of 25 ° C. at the frequency of the measurement current varies by 5% due to the temperature change. It becomes a gain and changes by about -0.9 dB. This value is equivalent to a fluctuation of the measured value of about 5% as a voltage value, and in order to maintain a highly accurate measurement state, the fluctuation is much more than 5% in the operating temperature range of the internal impedance measuring device of the storage battery. It is necessary to select a good part with few characteristics. It is sufficiently possible to obtain a resistor with a characteristic within ± 0.2% in the operating temperature range of the internal impedance measuring device of the storage battery, but it is extremely difficult to achieve this level of temperature characteristic with a capacitor. It becomes very expensive.
[0037]
Therefore, by switching the input of the electromotive force of the storage battery 1 to the analog signal processing means 41 and the electromotive force of the measurement current detection means 5 by the input switching means 45, the analog signal processing means 41 including a common analog filter performs processing. Thereafter, the digital signal processing means 43 including a common digital filter processes the gain fluctuation of the analog filter, which directly causes the measurement error of the electromotive force, and the electromotive force due to the temperature characteristic of the measurement current detection means 5 or the like. The variation can be limited to about the fluctuation amount, and the measurement error of the internal impedance of the storage battery 1 can be reduced.
[0038]
In the present embodiment, as shown in FIG. 1, the measured electromotive force component generated at both ends of the storage battery 1 and the alternating electromotive force component generated at both ends of the measurement current detecting means 5 are analog signal processing including a common analog filter. It is desirable to use an apparatus that performs processing by means 41 and then processing by digital signal processing means 43 including a common digital filter. However, the embodiment of the present invention is not limited to this, and the measurement target that occurs at both ends of storage battery 1 is used. Each of the electromotive force component and the AC electromotive force component generated at both ends of the measurement current detection means 5 is processed by an individual analog filter having substantially the same characteristics (that is, close to a level that does not greatly affect the measurement accuracy). After that, it goes without saying that the processing may be performed by a digital filter having substantially the same characteristics.
[0039]
Next, a method for measuring the internal impedance of the storage battery of the present invention will be described. FIG. 2 is a flowchart showing an outline of a method for measuring internal impedance of a storage battery according to an embodiment of the present invention. As shown in FIG. 2, in the present embodiment, measurement current I is measured (step-1), measured electromotive force V is measured (step-2), and internal impedance Z (= V / I) is measured (step-3). 3).
[0040]
Next, details of Step-1 and Step-2 will be described with reference to the drawings. Below, it demonstrates using the code | symbol of FIG.
[0041]
FIG. 3 is a flowchart showing an example of details of Step-1 in FIG. The contents will be described below.
[0042]
(Step-1A)
The alternating current generating means 3 is operated. In this case, as shown in FIG. 1, a control signal for controlling the alternating current generating means 3 is sent from the digital signal processing means 43.
(Step-1B)
A control signal is sent from the digital signal processing means 43 to the input switching means 45 to switch the input switching means 45 to the measured current detection means 5 side.
(Step-1C)
The signal of electromotive force generated when the alternating current generated by the alternating current generating means 3 flows to the measurement current detecting means 5 is processed by the analog signal processing means 41, and the frequency other than the frequency of the alternating current generated by the alternating current generating means 3 is used. Reduce ingredients.
(Step-1D)
The signal obtained in step-1C is converted into a digital signal by the A / D conversion means 42.
(Step-1E)
The digital signal processing means 43 performs digital filter processing on the digital signal obtained in step -1D.
(Step-1F)
Of the digital signal obtained in the step-1E, a component having the same frequency as the frequency of the alternating current generated by the alternating current generating means 3 is picked up by the digital signal processing means 43 and stored in the storage means 44 as the measured current I. save. Since the component itself having the same frequency as the frequency of the alternating current generated by the alternating current generating means 3 is a voltage, the coefficient of the measuring current detecting means 5 is taken into account (for example, with a shunt resistance having a resistance value of 0.1Ω). Divide by that value if any) and treat as current.
[0043]
Here, when the process of Step-1F is completed, the process of Step-1 is completed, but the process of Step-2 is continued as shown in FIG.
[0044]
FIG. 4 is a flowchart showing an example of details of Step-2 in FIG. The contents will be described below.
[0045]
(Step-2A)
A control signal is sent from the digital signal processing means 43 to the input switching means 45 to switch the input switching means 45 to the storage battery 1 side.
(Step-2B)
A signal of the electromotive force to be measured generated when the alternating current generated by the alternating current generating means 3 flows to the storage battery 1 is processed by the analog signal processing means 41, and the frequency components other than the frequency of the alternating current generated by the alternating current generating means 3 Reduce.
(Step-2C)
The signal obtained in step-2B is converted into a digital signal by the A / D conversion means 42.
(Step-2D)
The digital signal processing means 43 applies digital filter processing to the digital signal obtained in step-2C.
(Step-2E)
Of the digital signal obtained in step -2D, a component having the same frequency as the frequency of the alternating current generated by the alternating current generating means 3 is picked up by the digital signal processing means 43 and stored as measured electromotive force V. 44.
(Step-2F)
The alternating current generating means 3 is stopped. In this case, as shown in FIG. 1, a control signal for controlling the alternating current generating means 3 is sent from the digital signal processing means 43. Needless to say, the AC current generating means 3 may be stopped not after Step-2F but after Step-3.
[0046]
Here, when the process of Step-2F is finished, the process of Step-1 is finished, but the process of Step-3 is continuously performed as shown in FIG.
[0047]
The process of Step-3 shown in FIG. 2 uses the data of the measured current I measured in Step 1 and the data of the measured electromotive force V measured in Step 2, to store the internal impedance Z of the storage battery 1. (= V / I) is obtained. This calculation is performed inside the digital signal processing means 43.
[0048]
2 shows the case where the internal impedance of one storage battery 1 constituting the storage battery group 2 is measured. When the internal impedance of a plurality of storage batteries 1 is to be measured, FIG. Needless to say, after the end of the measurement in the flowchart of FIG.
[0049]
Thus, according to this embodiment, it becomes possible to minimize the influence of noise components other than the frequency component of the alternating current generated by the alternating current generating means, and the measured electromotive force component buried in the noise component can be reduced. Although it is possible to measure the internal impedance of the storage battery without incurring a cost increase in measurement, the embodiment is not limited to the above-described embodiment, and is appropriately within the scope of the matters described in the claims. It goes without saying that changes are possible.
[0050]
【The invention's effect】
As described above, according to the present invention, when measuring the internal impedance of a storage battery, the waveform of the alternating current generated by the alternating current generating means is substantially a sine wave, and the measurement target generated at both ends of the storage battery to be measured for internal impedance. After processing each of the power component and the AC electromotive force component generated at both ends of the measurement current detecting means connected in series with the AC current generating means with an analog filter having substantially the same characteristics, substantially the same characteristics Therefore, it is extremely important to minimize the influence of noise components other than the frequency component of the alternating current generated by the alternating current generating means, compared to the case where the synchronous detecting means is used. It can be realized at low cost, and it does not increase the cost when measuring the measured electromotive force component buried in the noise component. It is possible to measure the impedance.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an outline of a storage battery internal impedance measuring apparatus according to an embodiment of the present invention.
FIG. 2 is a flowchart showing an outline of a method for measuring internal impedance of a storage battery according to an embodiment of the present invention.
FIG. 3 is a flowchart showing an example of details of Step-1 in FIG. 2;
FIG. 4 is a flowchart showing an example of details of step-2 in FIG. 2;
FIG. 5 is a schematic explanatory diagram showing the principle of measuring internal impedance of a storage battery by the AC four-terminal method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Storage battery 2 Storage battery group 3 AC current generation means 4 AC voltage measurement means 5 Measurement current detection means 41 Analog signal processing means 42 A / D conversion means 43 Digital signal processing means 44 Storage means 45 Input switching means

Claims (3)

In the internal impedance measurement method of a storage battery that measures the internal impedance of each storage battery of a storage battery group in which a plurality of storage batteries are connected in series using an alternating current generation means and an alternating voltage measurement means,
A waveform of an alternating current generated by the alternating current generating means is substantially a sine wave, a measured electromotive force component generated at both ends of the storage battery to be measured for internal impedance, and a measurement current detection connected in series to the alternating current generating means A storage battery comprising a step of processing each of the AC electromotive force components generated at both ends of the means with an analog filter having substantially the same characteristics, and then processing with a digital filter having substantially the same characteristics Internal impedance measurement method. The measured electromotive force component generated at both ends of the storage battery to be measured for internal impedance and the AC electromotive force component generated at both ends of the measurement current detecting means are processed by a common analog filter and then processed by a common digital filter. The method for measuring internal impedance of a storage battery according to claim 1, further comprising a step. In the internal impedance measuring device of the storage battery having the alternating current generating means and the alternating voltage measuring means for measuring the internal impedance of each storage battery of the storage battery group in which a plurality of storage batteries are connected in series,
A measuring current detecting means is connected in series to the alternating current generating means, the waveform of the alternating current generated by the alternating current generating means is substantially a sine wave, and the alternating voltage measuring means is a single analog An apparatus for measuring internal impedance of a storage battery, comprising: analog signal processing means including a filter; digital signal processing means including a single digital filter; and input switching means for switching an input to the analog signal processing means.

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