JP5609478B2 - Secondary battery charge / discharge device and power storage system - Google Patents

Description

  The present invention relates to a device that charges and charges a rechargeable secondary battery, and a device that discharges the charged secondary battery.

  Development of a power storage technology that stores power using a rechargeable secondary battery that can be repeatedly used and supplies power from the secondary battery to the grid when necessary (for example, see Non-Patent Document 1). Such power storage technology can be used not only to increase fluctuations in power demand and increase the utilization rate of power generation facilities, but also to supplement power generation facilities with large fluctuations in power generation, such as solar power generation and wind power generation. It is applicable (for example, refer nonpatent literature 2).

  The secondary battery used for the above-mentioned uses consists of an aggregate of many batteries. For example, in the case of a lithium ion battery, since one voltage is about 3.6 V, a string is formed by connecting a number of batteries in series, and a series-parallel connection in which the strings are connected in parallel is used. By charging such a large number of batteries, voltage / power capable of grid connection can be supplied when necessary.

Mitsubishi Heavy Industries Technical Report Vol. 41, no. 5. “Development of lithium-ion battery power storage system”, September 2004 Journal of the Institute of Electrical Installation, October 2005, “Application of Redox Flow Battery to Smooth Wind Power Output”

  FIG. 8 is a connection diagram illustrating an example of a state in which strings are connected in parallel as described above. In the figure, a plurality of batteries (secondary batteries) are connected in series in the vertical direction to form one string. Also, three sets of strings S1, S2, S3 are connected in parallel to each other. When charging, current flows into the battery and power is stored. At the time of discharging, current flows out from the battery, and electric power is supplied to the outside.

For the strings S1, S2, and S3, the sum of electromotive forces is E1, E2, and E3, the sum of internal resistances is R1, R2, and R3, the current that flows is i1, i2, and i3. When the total current flowing through the string is I, the following equation is established.
V = E1-i1 * R1 = E2-i2 * R2 = E3-i3 * R3
I = i1 + i2 + i3

  Each battery varies in internal resistance, and the internal resistance varies greatly depending on the degree of deterioration. Therefore, it may be said that R1, R2, and R3 do not have the same value. Therefore, the currents i1, i2, and i3 are usually different values. The depth of charge of the battery changes with the time integration value of the current at the time of charging / discharging. Therefore, if there is a variation in current, the charging depth also varies. Further, when any one of the batteries is fully charged during charging, it is necessary to stop the charging even if the other batteries are not fully charged in order to prevent overcharging. Therefore, not all batteries can be fully charged. Conversely, when discharging power from a battery and supplying power to the outside, when the battery with the lowest charge depth reaches the discharge limit, other batteries will be discharged even if there is a remaining amount to prevent overdischarge. It needs to be stopped.

  In this way, when charging / discharging is performed using a large number of batteries with varying performance as a battery, any one of the batteries pulls the entire foot, so that the overall charge / discharge performance is sufficient. There is a problem that it cannot be used. In order to forcibly eliminate the variation in the remaining amount, it is possible to arrange the remaining amount temporarily by fully charging all the batteries individually or conversely emptying them. However, this requires a special work, and during that time, it cannot be used as a charge / discharge device, resulting in a decrease in utilization rate.

  In view of such conventional problems, an object of the present invention is to provide a charging / discharging device that can more effectively utilize a plurality of secondary batteries having variations in performance, and a power storage system using the same. To do.

( 1 ) The secondary battery charging device of the present invention is configured by connecting a plurality of secondary batteries and a plurality of capacitors in series with each other , and both ends connected in series are connected to an external converter. And when charging the secondary battery by discharging the power storage unit, a part of the capacitors selected from the plurality of capacitors are connected to the secondary battery selected from the plurality of secondary batteries, and the secondary battery when charging the power storage unit by the discharge of the battery, Ru der which the step of charging sequentially connect one of rechargeable batteries to a plurality of capacitors, and a connection device which performs sequentially for each of the secondary batteries .

In the secondary battery charging / discharging device configured as described above, the external converter directly exchanges electric energy with a power storage unit configured by connecting a plurality of capacitors in series with each other. It is not the next battery. Therefore, the degree of freedom of how to use the plurality of secondary batteries is widened, and there is no need to use the plurality of secondary batteries in a fixed circuit configuration. Thereby, even a plurality of secondary batteries having different performances (including types) can be freely used. For example, when the secondary batteries are discharged, the secondary batteries are used in order, so that each battery can be used regardless of the remaining amount, and each battery can be used. Moreover, when charging a secondary battery from a capacitor, it is possible to freely charge each secondary battery by selecting and connecting the secondary battery. In addition, by using a plurality of capacitors connected in series, even if the power storage unit as a whole has a high voltage rating, the voltage across each capacitor is suitable for a voltage that can be output by a secondary battery or for charging a secondary battery. Can be voltage.

( 2 ) Moreover, in the secondary battery charging / discharging device of the above (1) , the connection device may repeatedly perform the steps in order for each secondary battery.
In this case, each secondary battery repeats discharging periodically, and the remaining amount is reduced at an even pace. That is, the electric energy of each battery can be used evenly.

( 3 ) In the secondary battery charge / discharge device according to (1) , the secondary battery may be a single secondary battery or a string connected in series. Good.
In particular, when a plurality of secondary batteries are connected in series, variation in internal resistance and charge depth for each string is likely to occur. Even in such a case, there is no problem by selecting and connecting them in order or connecting them in order. Can be used.

( 4 ) Moreover, in the secondary battery charging / discharging device of the above (1) , different secondary batteries may be included in the plurality of secondary batteries.
Different types often have different voltages, but even in such a case, they can be used without problems by being selectively connected or sequentially connected.

( 5 ) Moreover, in the secondary battery charging / discharging device of (1), it is preferable that a circuit element for suppressing current is interposed between the secondary battery and the power storage unit.
In this case, it is possible to suppress an excessive increase in current at the start of charging / discharging.

( 6 ) Moreover, in the secondary battery charging / discharging device according to (1), it is preferable that the connection device includes a circuit for measuring a voltage between both ends of each secondary battery.
Since secondary batteries are selected or used in order, there are times when they are not used. Therefore, the charging depth can be obtained based on the voltage across the secondary battery when not in use and not connected to the capacitor.

( 7 ) In the secondary battery charge / discharge device of ( 6 ) above, the connection device sets the charge depth based on the voltage at both ends of each unused secondary battery that is not used for connection with the capacitor. In addition, when any of the secondary batteries is charged, a secondary battery having a relatively low charging depth may be preferentially connected to the capacitor.
In this case, the secondary battery with a small remaining amount can be charged to restore the secondary battery to a state where it can be used for discharging.

( 8 ) In the secondary battery charge / discharge device according to (1), the connection between the secondary battery and the capacitor is preferably performed via a semiconductor switching element.
The semiconductor switching element is suitable for high-speed response and excellent in durability.

( 9 ) In the secondary battery charge / discharge device of ( 8 ), the semiconductor switching element may be an FET.
The FET is suitable for high-speed response, and in particular, the SiC-FET is most excellent in terms of high-speed response and withstand voltage.

( 10 ) In the secondary battery charge / discharge device according to ( 8 ) or ( 9 ), the semiconductor switching element is preferably a wide band gap semiconductor made of a material containing SiC, GaN, or diamond. .
These devices have an overwhelmingly superior dielectric strength compared to silicon, and have low switching loss due to their low on-resistance. Also suitable for high-speed response and excellent durability.

( 11 ) Moreover, the electric power storage system provided with the secondary battery charging / discharging apparatus of said (1) and the converter which mediates the input / output of the said secondary battery charging / discharging apparatus and a desired power supply system is comprised. Can do.
By using the above-described secondary battery charging / discharging device, an electric power storage system can be configured using secondary batteries having variations in performance. Therefore, for example, by using a used secondary battery, the power storage system can be configured at low cost.

  According to the secondary battery charging / discharging device and the power storage system of the present invention, it is possible to more effectively utilize a plurality of secondary batteries having variations in performance.

It is a connection diagram showing the principal part of the power storage system according to an embodiment of the present invention. It is a connection diagram which shows the principal part of an electric power storage system in case the structure of a converter is different from FIG. It is a connection diagram which shows the principal part of an electric power storage system in the case of connecting with a DC load system. It is a circuit diagram which shows an example of the detailed circuit structure of the secondary battery charging / discharging apparatus which concerns on one Embodiment of this invention. It is a flowchart which shows an example of the process regarding acquisition of battery information. It is a flowchart which shows an example of the process regarding the operation | movement of charge or discharge. It is a circuit diagram which shows the other example of the detailed circuit structure of a secondary battery charging / discharging apparatus. It is a connection diagram which shows an example of the state which connected the string of the secondary battery in parallel.

<Outline of power storage system>
FIG. 1 is a connection diagram showing a main part of an electric power storage system according to an embodiment of the present invention. In the figure, an electric power storage system linked to an AC load system includes an AC / DC converter 101 that converts AC / DC into each other and a secondary battery charge / discharge device 1. Note that only a capacitor forming a part of the secondary battery charging / discharging device 1 is illustrated, and details will be described later.

  The plurality of capacitors C1 to Cn are connected in series to form a string. The plurality of strings S1, S2,..., Sm are connected to each other in parallel. Note that these numerical values of n and m can be freely configured as necessary, and a plurality of numerical values is also an example. That is, the number of strings may be one, or more basically one capacitor (this will be described later).

FIG. 2 is a connection diagram illustrating a main part of the power storage system when the configuration of the conversion device is different from that in FIG. 1. In this case, the voltage is once adjusted by the DC / DC converter 102 and then connected to the AC load system via the AC / DC converter 101. This configuration is preferable for optimizing the conversion efficiency.
FIG. 3 is a connection diagram showing a main part of the power storage system when interconnected with a DC load system. In this case, only the DC / DC converter 102 is required.
As described above, the converters (101, 102) serve to mediate input / output of the secondary battery charge / discharge device 1 and a desired power supply system.

《Secondary battery charge / discharge device》
FIG. 4 is a circuit diagram showing an example of a detailed circuit configuration of the secondary battery charging / discharging device 1. In the figure, this device 1 is roughly composed of three parts, that is, a plurality of secondary batteries B1 to B8, a power storage unit 2 using capacitors, and a connection device 3. As an example of the “plurality”, there are eight secondary batteries B1 to B8, for example. Each individual secondary battery may be composed of only one individual battery, or may be a string connected in series. In addition, as a secondary battery, a lithium ion battery, a lead acid battery, a nickel metal hydride battery, and other various rechargeable batteries can be used.

  On the other hand, for example, four equal-capacitance capacitors C1 to C4 are connected to each other in series to form a power storage unit 2 forming one string. These capacitors C1 to C4 correspond to, for example, one string of capacitors C1 to Cn in FIG. The power storage unit 2 relays the electric energy by continuously performing the process of storing and releasing the electric energy provided from the secondary battery or the converter (101, 102).

  Here, it is the power storage unit 2 that directly exchanges electric energy with the converters (101, 102), and the voltage appearing as seen from the converters (101, 102) is the power storage unit. Only the voltage at both ends of part 2 is shown. The secondary batteries B <b> 1 to B <b> 8 only need to be able to deliver electric energy to the power storage unit 2 by discharging or to be charged by receiving electric energy from the power storage unit 2. Therefore, the degree of freedom of how to use the plurality of secondary batteries B1 to B8 is widened, and it is not necessary to use a fixed circuit configuration.

  The negative electrodes of the secondary batteries B1 to B8 are all connected to the common negative side electric circuit Ln2. The positive electrode is connected to the plus side electric circuit Lp2 via the switches SB1 to SB8, respectively. The switches SB1 to SB8 are switches that select which secondary batteries B1 to B8 are connected to the plus side electric circuit Lp2. The switches SP1 to SP4 select which portion of the power storage unit 2 is connected to the plus side electric circuit Lp2 via the resistor R. That is, the destinations via the switches SP1 to SP4 are respectively the plus side electric circuit Lp1 on the plus side of the power storage unit 2, the interconnection point of the capacitors C1 and C2, the interconnection point of the capacitors C2 and C3, and the mutual connection of the capacitors C3 and C4. It is a connection point.

  The resistor R is provided for the purpose of suppressing the current flowing therethrough, in particular, suppressing the current at the start of charging / discharging from becoming excessively large. However, in addition to the resistor, a reactor may be used. In short, it is sufficient that a circuit element that suppresses a current flowing between the secondary batteries B1 to B8 and the power storage unit 2 is interposed.

  Further, the switches SN1 to SN4 select which portion of the power storage unit 2 is connected to the minus side electric circuit Ln2. That is, the destinations through the switches SN1 to SN4 are the interconnection points of the capacitors C1 and C2, the interconnection points of the capacitors C2 and C3, the interconnection points of the capacitors C3 and C4, and the negative side on the negative side of the power storage unit 2, respectively. This is the electric circuit Ln1.

The switches SB1 to SB8, SP1 to SP4, and SN1 to SN4 are semiconductor switching elements suitable for high-speed response and excellent in durability. For example, FETs are used. The FET is suitable for high-speed response, and in particular, the SiC-FET is most excellent in terms of high-speed response and withstand voltage. As a material, a wide band gap semiconductor made of a material such as SiC, GaN, or diamond is preferable.
The control device 4 including the CPU individually turns on / off the switches SB1 to SB8, SP1 to SP4, and SN1 to SN4.

  On the other hand, the positive electrodes of the secondary batteries B1 to B8 are connected to the signal circuit Ls via the photocouplers Pc1 to Pc8, respectively. The negative electric circuit Ln2 to which the signal electric circuit Ls and the negative electrodes of the secondary batteries B1 to B8 are connected is connected to the input terminal of the A / D converter 5. That is, when any one photocoupler is turned on, the voltage across the corresponding secondary battery is input to the A / D converter 5. The A / D converter 5 converts the input analog voltage value into a digital voltage value and provides it to the control device 4. The control device 4 turns on / off the photocouplers Pc1 to Pc8.

Next, operation | movement of said secondary battery charging / discharging apparatus 1 is demonstrated. The operation of the secondary battery charge / discharge device includes a process related to the acquisition of battery information and a process related to the operation of charging or discharging, and these processes are performed in parallel.
The photocouplers Pc1 to Pc8, the A / D converter 5, and the control device 4 constitute a circuit that measures the voltage across each of the secondary batteries B1 to B8, and battery information is acquired by this circuit. In addition, in the secondary battery charging / discharging apparatus 1 of this embodiment, since secondary battery B1-B8 is selected or used in order, there exists a secondary battery which is not used. An electromotive force can be measured for a secondary battery that is not used.

  FIG. 5 is a flowchart illustrating an example of processing related to acquisition of battery information. In the figure, first, the control device 4 turns on one of the eight photocouplers Pc1 to Pc8 (all others are turned off) (step S1), and a corresponding secondary battery (hereinafter simply referred to as a battery). Is also measured (step S2). Here, the voltage across the battery that is not currently used does not have a voltage drop due to the internal resistance, and thus substantially represents an electromotive force. On the other hand, the voltage across the battery used is a value lower than the electromotive force by the amount of voltage drop due to the current flowing through the internal resistance.

  Therefore, the control device 4 determines whether or not the battery whose both-ends voltage has been measured is currently in use, that is, whether or not the battery is in use (step S3). If not in use, the measured value is treated as an electromotive force (step S4). If the electromotive force is known, the charging depth can be obtained using the Nernst equation (step S5). On the other hand, if it is in use, the measured value is directly treated as the voltage at both ends (step S6), and the internal resistance is obtained based on the comparison with the already stored electromotive force (step S7).

  Thereafter, the control device 4 returns to step S1, turns on the next photocoupler, and performs the same processing. In step S1, the control device 4 selects, for example, photocouplers Pc1 to Pc8 in order, and next to Pc8, sequentially selects from Pc1. In this way, the battery information is repeatedly acquired cyclically, and the information is updated. The battery information is transmitted from the control device 4 to an external host system (not shown), and becomes a judgment material when the host system instructs the secondary battery charge / discharge device 1 to charge or discharge. Further, the charging depth, that is, the remaining amount as a battery is a selection criterion for selecting which secondary battery to select when charging the secondary battery. Since the internal resistance of the battery increases as it deteriorates, it is possible to determine the replacement time based on the internal resistance and perform a process of issuing a warning prompting the replacement.

FIG. 6 is a flowchart illustrating an example of processing related to charging or discharging operation. First, the control device 4 distinguishes the operation depending on whether the battery is charged or discharged (step S10). Whether to perform the charge / discharge operation depends on an instruction from the host system.
First, the operation for discharging the secondary battery will be described. In addition, the battery used for discharge is basically one (one string).

  First, the control device 4 determines whether or not a battery is currently used, that is, whether any of the switches SB1 to SB8 is on (step S11). Here, at the beginning of capacitor charging, the switches SB1 to SB8 are all turned off. Therefore, the control device 4 connects the next battery in step S13. The next battery mentioned here is any one of the secondary batteries B1 to B8.

  Specifically, the control device 4 turns on a switch (any one of SB1 to SB8) corresponding to the next battery, and connects the battery to the plus side electric circuit Lp2. Then, the control device 4 turns on the switches SP1 and SN1, configures a discharge circuit from the connected battery to the capacitor C1, and charges the capacitor C1 (step S14). Although the time for discharging the battery depends on the capacity of the capacitor C1 and the performance of the battery, it is very short. After the time has elapsed, the switches SP1 and SN1 are turned off.

Subsequently, the control device 4 turns on the switches SP2 and SN2, configures a discharge circuit from the connected battery to the capacitor C2, and charges the capacitor C2 (step S15). The control device 4 turns off the switches SP2 and SN2 after the battery discharge time has elapsed.
Subsequently, the control device 4 turns on the switches SP3 and SN3 to form a discharge circuit from the connected battery to the capacitor C3, and charges the capacitor C3 (step S16). The control device 4 turns off the switches SP3 and SN3 after the battery discharge time has elapsed.
Subsequently, the control device 4 turns on the switches SP4 and SN4 to form a discharge circuit from the connected battery to the capacitor C4, and charges the capacitor C4 (step S17). The control device 4 turns off the switches SP4 and SN4 after the battery discharge time has elapsed.

  After step S17, the control device 4 returns to step S10 and repeats the same processing. Since the battery is already used after the second time, the process proceeds from step S11 to step S12, and the control device 4 turns off the switch (one of SB1 to SB8) corresponding to the battery currently used. The battery is disconnected from the system (step S12). Note that before this disconnection, the switches SP1 to SP4 and SN1 to SN4 are all turned off. In the subsequent step S13, the control device 4 connects the next battery according to a predetermined order. The subsequent steps S14 to S17 are the same as those described above.

  In this way, the connecting device 3 sequentially charges the capacitors C1, C2, C3, and C4 with the battery B1, if the predetermined order is, for example, the order of the batteries B1, B2,... B7, B8. Step of sequentially charging capacitors C1, C2, C3, C4 with battery B2, ... step of sequentially charging capacitors C1, C2, C3, C4 with battery B7, capacitors C1, C2, C3 with battery B8 , C4 are sequentially charged, so that each step is sequentially performed for each secondary battery. When the process of charging with the battery B8 ends, the process returns to the process of charging with the battery B1 again, and the same processing is repeated.

Next, the operation when charging the secondary battery will be described. The number of batteries used for charging (that is, charged) is basically one (one string).
First, based on the above-described battery information, the control device 4 specifies the battery (any one of B1 to B8) having the lowest charging depth as a battery for charging (charging object) as a battery to be selected next ( Step S21).

  Next, the control device 4 turns off the switch (any of SB1 to SB8) corresponding to the currently selected battery, and disconnects the battery from the system (step S22). Note that before this disconnection, the switches SP1 to SP4 and SN1 to SN4 are all turned off. Subsequently, the control device 4 turns on a switch (any one of SB1 to SB8) corresponding to the battery to be selected next, and connects the battery to the plus side electric circuit Lp2 (step S23). Then, the control device 4 turns on the switches SP1 and SN1, configures a charging circuit from the capacitor C1 to the selected battery, and discharges the capacitor C1 (step S24). The time for discharging the capacitor C1 is very short, and after the time has elapsed, the switches SP1 and SN1 are turned off.

Subsequently, the control device 4 turns on the switches SP2 and SN2, configures a charging circuit from the capacitor C2 to the selected battery, and discharges the capacitor C2 (step S25). Further, the control device 4 turns off the switches SP2 and SN2 after the discharge time of the capacitor C2.
Subsequently, the control device 4 turns on the switches SP3 and SN3, configures a charging circuit from the capacitor C3 to the selected battery, and discharges the capacitor C3 (step S26). Further, the control device 4 turns off the switches SP3 and SN3 after the discharge time of the capacitor C3 has elapsed.
Subsequently, the control device 4 turns on the switches SP4 and SN4, configures a charging circuit from the capacitor C4 to the selected battery, and discharges the capacitor C4 (step S27). Further, the control device 4 turns off the switches SP4 and SN4 after the discharge time of the capacitor C4 has elapsed.

In this case, the capacitors C1 to C4 are constantly charged from the converters (101, 102), and the charge lost by the discharge is replenished.
And the control apparatus 4 repeats discharge by said step S24-S27 predetermined times (step S28), and will return to step S10, if the predetermined number is reached.

  Thereafter, the same processing is performed. Since the battery to be charged is specified each time (step S21), when the currently selected battery is excluded from the next selection target, the battery with the lowest charging depth is selected from the remaining batteries. It will be. In this way, batteries with a small remaining amount are sequentially selected. Note that “the charging depth is the lowest among the remaining batteries” is an example of a selection criterion and does not necessarily have to be the lowest. In short, by preferentially selecting a battery having a relatively low charging depth, a battery with a small remaining amount can be restored to a state where it can be selected for discharging.

  In the secondary battery charging / discharging device configured as described above, the external converter (101, 102) directly exchanges electric energy with the power storage unit 2, and is not a secondary battery. The degree of freedom of how to use the secondary battery is expanded, and there is no need to use a plurality of secondary batteries in a fixed circuit configuration. Thereby, even a plurality of secondary batteries having different performances (including types) can be freely used. That is, when the secondary batteries are discharged, the secondary batteries are used in order, so that each battery can be used regardless of the remaining amount, and each battery can be used.

Moreover, the connection apparatus 3 repeats each process in order and repeatedly about each secondary battery B1-B8, and each secondary battery repeats discharge periodically and reduces remaining amount at an equal pace. Go. That is, the electric energy of each battery can be used evenly.
On the other hand, when charging the secondary battery from the capacitor, each secondary battery can be charged freely by selecting and connecting the secondary battery.

In particular, in the case where a plurality of secondary batteries are in series strings, variations in internal resistance and charging depth for each string are likely to occur, but even in such a case, by selecting and connecting or connecting in order, Can be used without problems. By sequentially using the capacitors during charging, the batteries can be used at an equal pace.
In addition, the voltage is often different if the type of battery is different, but even in such a case, it can be used without any problem by selecting and connecting in order.

In addition, by charging or discharging the four capacitors C1 to C4 constituting the power storage unit 2 one by one in order, the voltage is 1/4 of the voltage across the power storage unit 2 and used for discharging or charging. Can do. In addition, the “four capacitors” is merely an example, and as many series capacitors as necessary may be formed.
As described above, by using a plurality of capacitors connected in series, even if the power storage unit 2 as a whole has a high voltage rating, the voltage across each capacitor is the voltage that can be output by the secondary battery or the charging of the secondary battery. It is possible to make the voltage suitable for. Therefore, the secondary batteries B1 to B8 can be used in module units in which a plurality of cells are connected, and a large number of modules need not be connected in series.

  Note that charging or discharging the four capacitors C1 to C4 one by one in order is only an example, and depending on the number of capacitors in series and the voltage, charging or discharging a plurality of two or more. Is also possible. In short, a plurality of capacitors may be charged by individually connecting them to a secondary battery by dividing the capacitors individually or into small groups. The same applies when charging the secondary battery.

  Further, for example, when four capacitors C1 to C4 are provided as one string and these are provided in parallel with two strings (that is, when there are a total of eight capacitors), one set of switches SP1 to SP4 and SN1 to SN4 is provided separately. Thus, the eight capacitors may be configured to be charged or discharged sequentially. The same applies even when more capacitors are provided.

<Others>
In the above embodiment, a configuration in which a plurality of capacitors are connected in series as the power storage unit 2 has been described.
FIG. 7 is a circuit diagram showing another example of the detailed circuit configuration of the secondary battery charging / discharging device 1. The difference from FIG. 4 is that the power storage unit 2 is a single capacitor C1, and accordingly, the switches SP1 to SP4 and SN1 to SN4 of FIG. 4 are not necessary. Also in this case, the connection device 3 is configured to connect the capacitor C1 to a secondary battery selected from the plurality of secondary batteries B1 to B8 or a secondary battery in order, and configure a charging circuit or a discharging circuit. The basic configuration and operation are the same.

  In the above embodiment, when the secondary battery is charged from the capacitor, the selection of the secondary battery is performed based on the charging depth, which is preferable, but the secondary battery can be selected and charged at random. It is.

  Moreover, in the said embodiment, although the battery used for charge or discharge was fundamentally one (1 string), it is also possible to use for every several string and excludes such use. It is not a thing.

  4 and 7 show examples in which the switches SB1 to SB8 are provided on the positive electrode side of the batteries B1 to B8, respectively, it is also possible to provide them on the negative electrode side. For example, the positive electrodes of the batteries B1 to B8 are directly connected to the plus side electric circuit Lp2 without a switch, and the switches SB1 to SB8 are provided between the minus side electric circuit Ln2 and the negative electrodes of the batteries B1 to B8. Also good. In this case, the operation is the same.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

By using the secondary battery charging / discharging device of the present invention, it is possible to configure an electric power storage system using secondary batteries having performance variations including differences in battery types.
In the near future due to the spread of hybrid vehicles and electric vehicles, it is expected that a large number of used secondary battery products will be put on the market. By using the secondary battery charging / discharging device of the present invention, it is possible to effectively use a used secondary battery having such performance variations, and to construct a power storage system at low cost.

1: Secondary battery charge / discharge device 2: Power storage unit 3: Connection device 4: Control device 5: A / D converter 101: AC / DC converter 102: DC / DC converter B1-B8: Secondary batteries C1-C4: Capacitor Pc1 to Pc8: Photocoupler R: Resistance (circuit element)
S1 to Sm: Strings SB1 to SB8, SP1 to SP4, SN1 to SN4: Switch (semiconductor switching element)

Claims (11)

A plurality of secondary batteries;
A plurality of capacitors are connected in series with each other , and both ends connected in series are connected to an external converter, a power storage unit,
When charging the secondary battery by discharging the power storage unit, a part of the capacitors selected from a plurality of capacitors are connected to a secondary battery selected from the plurality of secondary batteries, and the secondary battery is discharged. wherein when charging the power storage unit, one of the step of sequentially connecting charging the secondary battery to a plurality of capacitors, each of the secondary batteries have that rechargeable battery charging and discharging device and a connecting device which performs sequentially for the . The secondary battery charging / discharging device according to claim 1, wherein the connection device repeatedly performs the process in order for each secondary battery . 2. The secondary battery charging / discharging device according to claim 1 , wherein the secondary battery is a string in which a single secondary battery is composed of only one or a plurality of secondary batteries are connected in series . The secondary battery charging / discharging device according to claim 1 , wherein the plurality of secondary batteries include different types of secondary batteries . The secondary battery charging / discharging device according to claim 1 , wherein a circuit element that suppresses a current is interposed between the secondary battery and the power storage unit . The secondary battery charging / discharging device according to claim 1 , wherein the connection device includes a circuit that measures a voltage between both ends of each secondary battery . The connection device obtains a charging depth based on the voltage between both ends of each unused secondary battery that is not used for connection to the capacitor, and when charging any of the secondary batteries, the charging depth The secondary battery charging / discharging device according to claim 6 , wherein a secondary battery having a relatively low voltage is preferentially connected to the capacitor . The secondary battery charge / discharge device according to claim 1, wherein the secondary battery and the capacitor are connected via a semiconductor switching element . The secondary battery charge / discharge device according to claim 8, wherein the semiconductor switching element is an FET . The secondary battery charge / discharge device according to claim 8 or 9, wherein the semiconductor switching element is a wide band gap semiconductor made of a material containing SiC, GaN, or diamond . A power storage system comprising: the secondary battery charge / discharge device according to claim 1; and a conversion device that mediates input / output of the secondary battery charge / discharge device and a desired power supply system .

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