JP7479264B2 - Secondary battery inspection equipment - Google Patents

Description

The present invention relates to a secondary battery inspection device that simultaneously inspects multiple secondary batteries in parallel by charging and discharging the batteries.

A secondary battery inspection device is known that inspects multiple secondary batteries simultaneously in parallel by charging and discharging the multiple secondary batteries. As shown in FIG. 8, this type of secondary battery inspection device 100 includes a bidirectional AC/DC conversion unit 101 connected to a three-phase AC power source P, an insulated bidirectional DC/DC conversion unit 102 connected to the same, a chopper circuit group 103 connected to the same, and a control unit 104 that controls the same. The chopper circuit group 103 includes chopper circuit units 103-1 to 103-N in the same number as the N (N is an integer of 2 or more) secondary batteries B-1 to B-N to be inspected.

When the control unit 104 causes the chopper circuit unit 103-1 to charge the secondary battery B-1, it turns on/off the first switch element SW1 of the chopper circuit unit 103-1 at a predetermined period T while keeping the second switch element SW2 of the chopper circuit unit 103-1 off. At this time, the control unit 104 can arbitrarily control the charging current of the secondary battery B-1 by adjusting the on time of the first switch element SW1 per period, that is, the pulse width of the gate signal given to the first switch element SW1. For example, as shown in FIG. 9, the control unit 104 can increase the charging current from 0 to a set value It in section T1, maintain the charging current at the set value It in the next section T2, and decrease the charging current to 0 in the next section T3.

On the other hand, when the control unit 104 causes the chopper circuit unit 103-1 to discharge the secondary battery B-1, it turns the first switch element SW2 of the chopper circuit unit 103-1 on and off at a predetermined period T while keeping the first switch element SW2 of the chopper circuit unit 103-1 on. At this time, the control unit 104 can arbitrarily control the discharge current of the secondary battery B-1 by adjusting the on time of the second switch element SW2 per period, i.e., the pulse width of the gate signal provided to the second switch element SW2.

Similarly, the control unit 104 can also arbitrarily control the charge and discharge currents of the other secondary batteries B-2 to B-N.

However, when the control unit 104 digitally generates the gate signal, the pulse width of the gate signal becomes discrete. For this reason, the control unit 104 may not be able to generate a pulse signal with the most suitable width to make the charge/discharge current match the set value It. In this case, the control unit 104 tries to maintain the charge/discharge current near the set value It by combining a pulse signal that is one step wider and a pulse signal that is one step narrower that it can generate. For example, the control unit 104 outputs five consecutive pulse signals that are one step wider (see sections A and C in FIG. 10) and then five consecutive pulse signals that are one step narrower (see sections B and D in the same figure). This type of control causes a relatively large ripple of ΔI in the charge/discharge current.

It is known that in order to reduce the amount of ripple ΔI in the charge/discharge current, it is sufficient to alternately output a pulse signal that is one step wider and a pulse signal that is one step narrower (see, for example, Non-Patent Document 1). However, this type of control places an excessive processing burden on the control unit 104, especially when a single control unit 104 must control multiple chopper circuit units 103-1 to 103-N.

“Ripple voltage of chopper circuit”, [online], Energy Chord, [Retrieved September 7, 2020], Internet <URL http://www.energychord.com/children/energy/pe/dcdc/contents/dcdc_chopper_ripple.html>

The present invention was made in consideration of the above circumstances, and aims to provide a secondary battery inspection device that can reduce the amount of ripple in the charge/discharge current compared to conventional devices without increasing the processing burden on the control unit.

In order to solve the above problem, the secondary battery inspection device according to the present invention is a device that inspects N secondary batteries (where N is an integer of 2 or more) simultaneously in parallel by charging and discharging the N secondary batteries, and is equipped with a chopper circuit group including N chopper circuit units connected to one of the N secondary batteries, and a control unit that individually controls each of the N chopper circuit units by outputting pulse signals with a width that is discrete by a predetermined discrete amount, and in controlling each of the N chopper circuit units, the control unit determines the width of an optimal pulse signal that is most suitable for matching the charging and discharging current of the secondary battery to a set value given from the outside in controlling each of the N chopper circuit units, and when the width of the optimal pulse signal differs from the discrete width, generates a pulse signal train by arranging in time at least one small pulse signal whose signal width is narrower than the width of the optimal pulse signal and at least one large pulse signal whose signal width is wider, and the control unit determines the number and arrangement of the small pulse signals and large pulse signals in the pulse signal train by referring to a table prepared in advance.

With this configuration, the table is configured so that the same pulse signal does not occur consecutively as much as possible in the pulse signal train generated by the small pulse signal and the large pulse signal, and if the same pulse signal occurs consecutively, the number of consecutive pulses is as small as possible, thereby making it possible to reduce the amount of ripple in the charge/discharge current more than before. Also, with this configuration, the widths of multiple pulse signals included in the pulse signal train can be determined collectively, so the burden on the control unit does not increase compared to the conventional case.

It is preferable that the control unit of the secondary battery inspection device generates a pulse signal train by treating a pulse signal narrower than the width of the optimal pulse signal and closest to the width of the optimal pulse signal as a small pulse signal, and by treating a pulse signal wider than the width of the optimal pulse signal and closest to the width of the optimal pulse signal as a large pulse signal.

The control unit of the secondary battery inspection device may also be configured to obtain information regarding the number and arrangement of small and large pulse signals to be included in the pulse signal train from the table, for example, based on the remainder when the width of the optimal pulse signal is divided by a discrete amount.

The present invention provides a secondary battery inspection device that can reduce the amount of ripple in the charge/discharge current compared to conventional devices without increasing the processing load on the control unit.

1 is a block diagram of a secondary battery inspection device according to an embodiment of the present invention. 10 is a diagram showing a table used in the secondary battery inspection device according to the embodiment; FIG. 5 is a diagram showing an example of a pulse signal sequence (gate signal) output by a control unit of the secondary battery inspection device according to the embodiment. FIG. 11 is a diagram showing another example of a pulse signal sequence (gate signal) output by the control unit of the secondary battery inspection device according to the embodiment. FIG. 13 is a diagram showing yet another example of a pulse signal sequence (gate signal) output by the control unit of the secondary battery inspection device according to the embodiment. FIG. 1A is a waveform diagram of a charging current by the secondary battery inspection device according to the embodiment, and FIG. 1B is a waveform diagram of a charging current output by a conventional secondary battery inspection device. 13 is a diagram showing a table used in a secondary battery inspection device according to a modified example of the present invention. FIG. 1 is a block diagram of a conventional secondary battery inspection device. FIG. 13 is a diagram showing an example of a change in charging current in a conventional secondary battery inspection device. 11A and 11B are diagrams illustrating an example of a gate signal and a charge/discharge current output by a control unit of a conventional secondary battery testing device.

Below, an embodiment of a secondary battery inspection device according to the present invention will be described with reference to the attached drawings.

[Example]
1 shows a secondary battery inspection device 10 according to an embodiment of the present invention. As shown in the figure, the secondary battery inspection device 10 is for simultaneously and in parallel inspecting N (where N is an integer of 2 or more; 16 in this embodiment) secondary batteries B-1 to B-N, and includes a bidirectional AC/DC conversion unit 11, an insulated bidirectional DC/DC conversion unit 12, a chopper circuit group 13 including N chopper circuit units 13-1 to 13-N, and a control unit 14.

The bidirectional AC/DC conversion unit 11 includes a bridge circuit consisting of six semiconductor switch elements that form three legs. The bidirectional AC/DC conversion unit 11 has AC side input/output terminals connected to a three-phase AC power source P and DC side input/output terminals connected to an insulated bidirectional DC/DC conversion unit 12.

The isolated bidirectional DC/DC conversion unit 12 includes a first bridge circuit consisting of four semiconductor switch elements that form two legs, a second bridge circuit consisting of four semiconductor switch elements that form two legs, and an isolation transformer provided between them. The first bridge circuit of the isolated bidirectional DC/DC conversion unit 12 is connected to the bidirectional AC/DC conversion unit 11. The second bridge circuit of the isolated bidirectional DC/DC conversion unit 12 is connected to the chopper circuit group 13.

The N chopper circuit units 13-1 to 13-N are each a bidirectional buck-boost chopper circuit having a first switch element SW1 and a second switch element SW2. Each of the chopper circuit units 13-1 to 13-N has a first input/output terminal connected to the insulated bidirectional DC/DC conversion unit 12 and a second input/output terminal connected to one of the secondary batteries B-1 to B-N. As shown in FIG. 1, the second input/output terminal of the chopper circuit unit 13-1 is connected to the secondary battery B-1, the second input/output terminal of the chopper circuit unit 13-2 is connected to the secondary battery B-2, ..., the second input/output terminal of the chopper circuit unit 13-N is connected to the secondary battery B-N.

The control unit 14 is configured to individually control the chopper circuit units 13-1 to 13-N using a digitally generated gate signal according to an externally provided set value It.

For example, when the control unit 14 causes the chopper circuit unit 13-1 to charge the secondary battery B-1, it turns the first switch element SW1 of the chopper circuit unit 13-1 on/off at a predetermined period T while keeping the second switch element SW2 of the chopper circuit unit 13-1 off. On the other hand, when the control unit 14 causes the chopper circuit unit 13-1 to discharge the secondary battery B-1, it turns the first switch element SW2 of the chopper circuit unit 13-1 on/off at a predetermined period T while keeping the first switch element SW2 of the chopper circuit unit 13-1 on.

The operation of the control unit 14 will be described in more detail below using an example in which the chopper circuit unit 13-1 is caused to charge the secondary battery B-1.

When the control unit 14 is given "4100 mA" as the set value It for the charging current of the secondary battery B-1, it converts it into a value suitable for internal calculation processing. The control unit 14 performs this conversion using the formula "set value It/3.5". The result of this calculation, "1171.4285...", is a value suitable for calculation processing that corresponds to "4100 mA".

The control unit 14 can adjust the on-time of the first switch element SW1 per cycle, i.e., the pulse width of the gate signal given to the first switch element SW1, in increments of 20, such as "1120", "1140", "1160", "1180", "1200", "1220", etc. The pulse width "1120" is the optimal pulse width for maintaining the charging current at "3920 mA (= 1120 x 3.5)". In other words, when the control unit 14 outputs a pulse signal having a width of "1120" continuously at cycle T as the gate signal of the first switch element SW1, the charging current becomes "3920 mA". Similarly, when the control unit 14 outputs pulse signals having widths of "1140", "1160", "1180", "1200", and "1220" in succession with a period T, the charging current becomes "3990mA", "4060mA", "4130mA", "4200mA", and "4270mA".

As mentioned above, the pulse width of the gate signal is basically determined based on the set value It for the charging current, but the charging current varies depending on the voltage value and resistance value of the secondary battery. For this reason, in practice, the charging current flowing through each secondary battery is detected, and the detected charging current is feedback-controlled to adjust the pulse width to a specified charging current.

The above increment of "20" can be considered to be a discrete amount of the width of the pulse signal that the control unit 14 can output.

Figure 2 shows table 15 stored in control unit 14. Table 15 describes the correspondence between the remainder when the width of the pulse signal most suitable for matching the charging current to the set value It (hereinafter referred to as the "optimum pulse signal") is divided by a discrete amount, and the sequence of small pulse signals and large pulse signals described below. Here, a small pulse signal means a pulse signal whose signal width is one step narrower than the optimum pulse signal, and a large pulse signal means a pulse signal whose signal width is one step wider than the optimum pulse signal. However, if control unit 14 is able to output an optimum pulse signal, the optimum pulse signal will be the small pulse signal.

When the control unit 14 is given a set value It for the charging current of the secondary battery B-1 of "4100 mA," it converts this to "1171.4285..." using the formula "set value It/3.5."

Next, the control unit 14 divides the integer part "1171" of "1171.4285..." by the discrete amount "20" to obtain the remainder "11".

Next, the control unit 14 obtains information "1010101101010101011010" about the number and order of small pulse signals and large pulse signals to be included in the gate signal (pulse signal sequence) to be output, by referring to the remainder "11" column in table 15 shown in FIG. 2. Here, "1" indicates a large pulse signal, and "0" indicates a small pulse signal.

Because the set value It is "4100mA (=1171.4285...)," the pulse width of the small pulse signal is "1160," and the pulse width of the large pulse signal is "1180." In other words, the small pulse signal is a pulse signal that is narrower than the width of the optimal pulse signal and closest to the width of the optimal pulse signal. Since the width of the optimal pulse signal is 1171.4285..., of the pulse signals with widths discrete by a discrete amount of 20... "1120," "1140," "1160," "1180," "1200," "1220,"..., "1160" is the pulse width of the small pulse signal. On the other hand, the large pulse signal is a pulse signal that is wider than the width of the optimal pulse signal and closest to the width of the optimal pulse signal. Since the optimal pulse signal width is 1171.4285..., among the pulse signals with widths discrete by a discrete amount of 20... "1120", "1140", "1160", "1180", "1200", "1220"..., "1180" is the pulse width of the large pulse signal.

The sequence obtained by referring to table 15 is "1010101101010101011010". Based on this, the control unit 14 outputs the pulse signal sequence shown in FIG. 3 as a gate signal. This pulse signal sequence is composed of nine small pulse signals with a width (1160) corresponding to "4060 mA" and eleven large pulse signals with a width (1180) corresponding to "4130 mA", arranged with a period T.

As another example, when the control unit 14 is given "4200 mA" as the set value It for the charging current of the secondary battery B-1, it converts this to "1200" and obtains a remainder of "0". In this case, the pulse width of the small pulse signal is "1200" and the pulse width of the large pulse signal is "1220". Also, the sequence corresponding to the remainder "0" is "000000000000000000000" (see FIG. 2). For this reason, the control unit 14 outputs the pulse signal sequence shown in FIG. 4 as a gate signal. This pulse signal sequence is composed of 20 small pulse signals with a width corresponding to "4200 mA" arranged in a period T.

As yet another example, when the control unit 14 is given "4190 mA" as the set value It for the charging current of the secondary battery B-1, it converts this to "1197.1428..." and obtains a remainder of "17". In this case, the pulse width of the small pulse signal is "1180" and the pulse width of the large pulse signal is "1200". The sequence corresponding to the remainder "17" is "10111111011111011111" (see FIG. 2). For this reason, the control unit 14 outputs the pulse signal sequence shown in FIG. 5 as a gate signal. This pulse signal sequence is composed of three small pulse signals with a width corresponding to "4130 mA" and 17 large pulse signals with a width corresponding to "4200 mA", arranged with a period T.

As can be seen from Fig. 2, the table 15 is configured so that the same pulse signal is not repeated as often as possible, and, if the same pulse signal is repeated for some reason, the number of consecutive pulses is as small as possible. Therefore, the secondary battery inspection device 10 according to this embodiment can reduce the amount of ripple in the charging current compared to the conventional example shown in Fig. 9. For example, the secondary battery inspection device 10 according to this embodiment can reduce the amount of ripple from 18 mA _p-p in the conventional example to 8 mA _p-p (see Fig. 6).

In addition, the secondary battery inspection device 10 according to this embodiment can determine the pulse widths for 20 periods all at once by referring to the table 15. Therefore, the secondary battery inspection device 10 according to this embodiment does not increase the processing load on the control unit 14.

The control unit 14 of the secondary battery inspection device 10 according to this embodiment can also cause the chopper circuit unit 13-1 to discharge the secondary battery B-1 using similar control. In this case, the control unit 14 can refer to a table for discharging, or a table common to charging and discharging. Naturally, the control unit 14 of the secondary battery inspection device 10 according to this embodiment can also cause the other chopper circuit units 13-2 to 13-N to charge and discharge the secondary batteries B-2 to B-N using similar control.

[Modification]
Although the embodiment of the secondary battery inspection device according to the present invention has been described above, the configuration of the present invention is not limited to this.

For example, the table 15 may be configured to determine a pulse signal train including a total of 30 large/small pulse signals (see FIG. 7). This configuration further reduces the processing load on the control unit 14. Note that if the set value It is frequently changed, it is better not to include too many large/small pulse signals in one pulse signal train. This is because the tracking ability to the set value It will decrease.

The number of columns in table 15 can be changed according to the discrete amount of the width of the pulse signal that the control unit 14 can output. For example, if the discrete amount is "10", there will be no remainder of 10 or more, so it is sufficient to prepare table 15 only for cases where the remainder is 0 to 9.

The circuit configuration of the chopper circuit units 13-1 to 13-N can be changed as appropriate. For example, the chopper circuit units 13-1 to 13-N can be step-down chopper circuits that only charge the secondary batteries B-1 to B-N, or step-up chopper circuits that only discharge the secondary batteries B-1 to B-N.

In addition, the formula for converting the set value It to a value suitable for internal calculation processing is not limited to "set value It/3.5".

In addition, the amount of discreteness of the width of the pulse signal that the control unit 14 can output is not limited to "20". In other words, in the present invention, it is sufficient that the width of the pulse signal that the control unit 14 can output is discrete rather than continuous.

10 Secondary battery inspection device 11 Bidirectional AC/DC conversion unit 12 Insulated bidirectional DC/DC conversion unit 13 Chopper circuit group 13-1 to 13-N Chopper circuit unit 14 Control unit 15 Tables B-1 to B-N Secondary battery P Three-phase AC power supply SW1 First switch element SW2 Second switch element

Claims (2)

A secondary battery inspection device that inspects N secondary batteries (where N is an integer of 2 or more) simultaneously in parallel by charging and discharging the N secondary batteries,
a chopper circuit group including N chopper circuit units connected to one of the N secondary batteries;
a control unit that outputs pulse signals having widths that are discrete by a predetermined discrete amount to individually control each of the N chopper circuit units;
Equipped with
the control unit, in controlling each of the N chopper circuit units, determines an optimum pulse signal width most suitable for making the charge/discharge current of the secondary battery coincide with an externally applied set value, and when the width of the optimum pulse signal differs from the discrete width, generates a pulse signal train by arranging in time at least one small pulse signal having a narrower signal width than the width of the optimum pulse signal and at least one large pulse signal having a wider signal width;
Moreover, the control unit determines the number and arrangement of the small pulse signals and the large pulse signals in the pulse signal train by referring to a table prepared in advance ,
The control unit obtains information on the number and arrangement of the small pulse signals and the large pulse signals to be included in the pulse signal train from the table based on the remainder when the width of the optimum pulse signal is divided by the discrete amount.
A secondary battery inspection device comprising: 2. The secondary battery inspection device according to claim 1, wherein the control unit generates the pulse signal train by setting the small pulse signal to a pulse signal having a width narrower than and closest to the width of the optimal pulse signal, and by setting the large pulse signal to a pulse signal having a width wider than and closest to the width of the optimal pulse signal.

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