JP5732804B2 - Secondary battery charge / discharge device and power storage system - Google Patents

Description

  The present invention relates to an apparatus for charging and charging a rechargeable secondary battery, and an apparatus for discharging 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. 9 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. On the other hand, when the battery is discharged from the battery and supplied to the outside, when the battery with the lowest charging depth reaches the discharge limit, the other batteries cannot be discharged even if there is a remaining amount.

  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.

For example, a secondary battery rechargeable device this comprises a plurality of secondary batteries, is constituted by a capacitor, constituting a first power storage unit connected to an external converter, the capacitor exclusively offer for discharge to the outside A second power storage unit and a capacitor of the first power storage unit connected to a secondary battery selected from the plurality of secondary batteries to form a charging circuit or a discharge circuit, and a capacitor of the second power storage unit Is connected to a secondary battery selected from the plurality of secondary batteries to form a capacitor charging circuit.

  In the secondary battery charging / discharging device configured as described above, the external converter directly exchanges electric energy with the first power storage unit, not the secondary 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 discharging a secondary battery, a secondary battery with a large remaining amount can be preferentially used without being restricted by a secondary battery with a small remaining amount. A secondary battery charging / discharging device using a battery can be provided.

  On the other hand, the provision of the second power storage unit dedicated to discharge to the outside makes it possible to provide a predetermined voltage separately from the first power storage unit based on the electrical energy of the secondary battery. Further, even when the secondary battery is charged via the first power storage unit, the second power storage unit can provide a voltage to the outside separately. Therefore, it is possible to supply a predetermined voltage to the outside via the second power storage unit while charging the secondary battery.

( 1 ) More specifically, the secondary battery charging / discharging device of the present invention is configured by connecting a plurality of secondary batteries and a plurality of capacitors in series to each other and connected to an external conversion device. One capacitor is selected from the plurality of capacitors of the first power storage unit, the second power storage unit configured by a capacitor provided exclusively for external discharge other than the conversion device, and the plurality of two capacitors. A charging circuit or a discharging circuit connected to a secondary battery selected from secondary batteries is sequentially executed for all capacitors of the first power storage unit, and the capacitors of the second power storage unit are connected to the plurality of capacitors. connected to the selected battery from the secondary battery that has a connecting device constituting a capacitor charging circuit.

In the secondary battery charging / discharging device configured as described above ( 1 ), the external converter directly exchanges electric energy with the first power storage unit, not the secondary 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 discharging a secondary battery, a secondary battery with a large remaining amount can be preferentially used without being restricted by a secondary battery with a small remaining amount. A secondary battery charging / discharging device using a battery can be provided. In addition, by using a plurality of capacitors connected in series, even if the overall voltage of the first power storage unit is high, the voltage across each capacitor can be used for the voltage that can be output by the secondary battery or for charging the secondary battery. A suitable voltage can be obtained.

  On the other hand, the provision of the second power storage unit dedicated to discharge to the outside makes it possible to provide a predetermined voltage separately from the first power storage unit based on the electrical energy of the secondary battery. Further, even when the secondary battery is charged via the first power storage unit, the second power storage unit can provide a voltage to the outside separately. Therefore, it is possible to supply a predetermined voltage to the outside via the second power storage unit while charging the secondary battery.

( 2 ) In the secondary battery charge / discharge device of (1 ), it is preferable that the first power storage unit and the second power storage unit are connected in series with each other.
In this case, since the first power storage unit and the second power storage unit can be configured by a plurality of capacitors that form one series body as a whole, the configuration of the entire power storage unit is simple and wasteful.

( 3 ) In the secondary battery charge / discharge device of (1 ) , the second power storage unit may be discharged to the outside during the charging of the first power storage unit by the conversion device.
In this case, for example, a DC voltage can be provided from the second power storage unit to the outside while charging the first power storage unit with regenerative power from the outside.

( 4 ) Moreover, in the secondary battery charge / discharge 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 the secondary battery is selected and used, in other words, there are times when it is 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.

(5) Further, in the secondary battery charging and discharging device of the above (4), connecting device, for each of the secondary batteries of nonuse not be selected for connection to any capacitor, based on the voltage across When obtaining the charge depth and charging any of the secondary batteries, a secondary battery having a relatively low charge depth may be preferentially connected to the capacitor of the first power storage unit.
In this case, a secondary battery with a small remaining amount can be charged, and the secondary battery can be recovered to a state that can be selected for discharging.

(6) Further, in the secondary battery charging and discharging device of the above (4), connecting device, for each of the secondary batteries of nonuse not be selected for connection to any capacitor, based on the voltage across When obtaining the charging depth and discharging any of the secondary batteries, a secondary battery having a relatively high charging depth may be preferentially connected to any of the capacitors.
In this case, a secondary battery having excellent performance at that time can be effectively used in a timely manner without being restricted by a battery having a poor charging depth.

( 7 ) Moreover, comprising the secondary battery charging / discharging apparatus of said ( 1 ), and the power storage system provided with the converter which mediates the input / output of the said secondary battery charging / discharging apparatus and a desired system | strain. it can.
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. In addition, since the second power storage unit dedicated to discharge to the outside is provided, a predetermined voltage can be provided separately from the first power storage unit based on the electrical energy of the secondary battery.

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 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. 5 is a flowchart (subroutine) showing the contents of battery selection / connection processing in FIG. 4. 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 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 the electric power storage system in the case of connecting with a DC load system. 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. This power storage system can be used, for example, as a main battery system in a hybrid car or an electric vehicle.
In the figure, a power storage system connected to a three-phase AC load for driving a motor includes an AC / DC converter 101 that converts AC / DC into each other and a secondary battery charge / discharge device 1. The AC / DC converter 101 can perform conversion from AC to DC and from DC to AC. The secondary battery charging / discharging device 1 is shown only with a part of the capacitor, and other 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. The numerical values of n and m can be freely configured as necessary. In order to drive the vehicle running motor, for example, a voltage of 200 to 500 V is required.
Further, another (unit) capacitor Cd is connected in series with each of the strings S1, S2,..., Sm, and the capacitors Cd are connected in parallel with each other. The voltage across each capacitor Cd is supplied to a DC load. This DC load is a load other than the driving motor, such as a vehicle illumination, air conditioning, instrumentation, etc., and the voltage is, for example, 12V.

《Secondary battery charge / discharge device》
FIG. 2 is a circuit diagram showing an example of a detailed circuit configuration of the secondary battery charge / discharge device 1 according to the embodiment of the present invention. In the figure, the device 1 is roughly divided into a plurality of secondary batteries B1 to B8, a first power storage unit 2a and a second power storage unit 2b configured by capacitors, and a connection device 3 (part surrounded by a two-dot chain line). ) And. As an example of the “plurality” related to the secondary battery, for example, there are eight secondary batteries B1 to B8 illustrated.

  Each of the secondary batteries B <b> 1 to B <b> 8 may be a single battery as a single battery, or may be a string connected in series. However, basically, the voltage across one battery (each of B1 to B8) corresponds to the voltage across one capacitor (each of C1 to C4). 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, the 1st electrical storage part 2a consists of a serial body of a some capacitor. For convenience of illustration and description, three capacitors C1, C2, and C3 are shown. However, in actuality, the number of the two terminals of the first power storage unit 2a needs to correspond to the voltage for the AC load. These capacitors C1 to C3 correspond to the one-string capacitors C1 to Cn in FIG. The 1st electrical storage part 2a performs the process of discharging | emitting while storing the electrical energy provided from either secondary battery B1-B8 or the AC / DC converter 101, and relays electrical energy.

  Here, it is the first power storage unit 2a that directly exchanges electric energy with the AC / DC converter 101, and what appears as a voltage when viewed from the AC / DC converter 101 is the first power storage unit 2a. Only the voltage at both ends. The secondary batteries B <b> 1 to B <b> 8 only need to be able to deliver electric energy to the first power storage unit 2 a by discharging or to be charged by receiving electric energy from the first power storage unit 2 a. 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 second power storage unit 2b is configured by one capacitor C4. However, this one is only an example, and may be a series body of a plurality of capacitors. That is, the number is necessary such that the voltage across the second power storage unit 2b corresponds to the voltage for the DC load. The capacitor C4 corresponds to, for example, the capacitor Cd in FIG. The second power storage unit 2b continuously performs a process of storing and releasing electric energy provided from any of the secondary batteries B1 to B8, and relays power supply from the secondary battery to the DC load. .

  Further, during the charging of the first power storage unit 2a by the external AC / DC converter 101, the second power storage unit 2b can be discharged to the outside. Therefore, it is also possible to supply the DC voltage from the second power storage unit 2b to the outside while charging the first power storage unit 2a with external power (for example, regenerative power). However, unlike the first power storage unit 2a, the capacitor C4 of the second power storage unit 2b is exclusively used for discharge to the outside, and is not used for charging the secondary battery.

  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 first and second power storage units 2a and 2b is connected to the plus side electric circuit Lp2 via the resistor R.

That is, the destinations via the switches SP1 to SP4 are the plus side electric circuit Lp1, the interconnection point of the capacitors C1 and C2, the interconnection point of the capacitors C2 and C3, and the interconnection point of the capacitors C3 and C4 (intermediate electric circuit Lm1). is there.
The AC / DC converter 101 for an AC load (for example, a traveling motor) is connected between the plus-side electric circuit Lp1 and the intermediate electric circuit Lm1. In addition, a DC load (for example, a load such as instrumentation) is connected between the intermediate circuit Lm1 and the minus side circuit Ln1.

  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 first and second power storage units 2a and 2b is provided.

  Further, the switches SN1 to SN4 select which portion of the first and second power storage units 2a and 2b is connected to the minus side electric circuit Ln2. That is, the destinations via the switches SN1 to SN4 are the interconnection point of the capacitors C1 and C2, the interconnection point of the capacitors C2 and C3, the interconnection point of the capacitors C3 and C4 (intermediate electric circuit Lm1), and the negative electric circuit Ln1, respectively. is there.

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 switches SM1 to SM8, 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 of the switches 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 switches SM1 to SM8. As the switches SM1 to SM8, semiconductor switching elements similar to those of the other switches SB1 to SB8, SP1 to SP4, and SN1 to SN4 may be used, or a photocoupler may be used.

  2 except for the first and second power storage units 2a and 2b and the secondary batteries B1 to B8, any one of the capacitors C1 to C3 is selected from the plurality of secondary batteries B1 to B8. Is connected to the secondary battery selected from the plurality of secondary batteries B1 to B8 to form the capacitor charging circuit. Yes.

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 switches SM <b> 1 to SM <b> 8, the A / D converter 5, and the control device 4 constitute a circuit that measures the voltage across each of the secondary batteries B <b> 1 to B <b> 8, and battery information is acquired by this circuit. Note that, in the secondary battery charging / discharging device 1 of the present embodiment, the secondary batteries B1 to B8 are selected and used, and thus non-selected secondary batteries are not used. An electromotive force can be measured for a secondary battery that is not used.

  FIG. 3 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 switches SM1 to SM8 (all others are turned off) (step S1), and the corresponding secondary battery (hereinafter simply referred to as a battery). ) Is measured (step S2). Here, since the voltage across the battery that is not currently used (selected) does not have a voltage drop due to internal resistance, it 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 it is the selected battery (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 switch, and performs the same processing. In step S1, the control device 4 selects, for example, switches SM1 to SM8 in order, and next to SM8 selects in order from SM1. In this way, the battery information is repeatedly acquired cyclically, and the information is updated.
Note that the depth of charge, that is, the remaining amount as a battery, is a selection criterion for selecting which secondary battery to select when charging and discharging. Further, 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. 4 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 outside (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 performs battery selection / connection processing (step S11). FIG. 5 is a flowchart (subroutine) showing the contents of this process. In FIG. 5, based on the battery information described above, the control device 4 specifies the battery (any one of B1 to B8) having the highest charging depth for discharging as the battery to be selected next (step Sx1). ). In addition, about the battery currently selected, since an accurate charge depth cannot be grasped because of a voltage drop, the battery is excluded and the battery (B1 to B8 having the highest charge depth among other batteries) is excluded. Any one of them excluding one in use) may be specified.

  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 Sx2). 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 Sx3).

Here, the control device 4 returns to step S12 in FIG. 4 to turn on the switches SP1 and SN1, configure a discharge circuit from the selected battery to the capacitor C1, and charge the capacitor C1. 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, constitutes a discharge circuit from the selected battery to the capacitor C2, and charges the capacitor C2 (step S13). 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 selected battery to the capacitor C3, and charges the capacitor C3 (step S14). Further, 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 selected battery to the capacitor C4, and charges the capacitor C4 (step S15). The control device 4 turns off the switches SP4 and SN4 after the battery discharge time has elapsed.

  After step S15, the control device 4 returns to step S10 and repeats the same processing. Since the battery is specified each time (steps S11 and Sx1), when the currently selected battery is excluded from the next selection target, the battery having the highest charging depth is selected from the remaining batteries. Become. In this way, batteries with a large remaining amount are sequentially selected. Note that “the charging depth is the highest among the remaining batteries” is an example of a selection criterion and does not necessarily have to be the highest. For example, it is possible to select at random from the batteries with the charge depth of 1 or 2 at random.

In short, by preferentially selecting a battery with a relatively high charge depth, a battery with excellent performance at that time can be used in a timely manner without being constrained by a battery with a low charge depth (low remaining charge). Can be used.
It is also possible to select and use the same battery continuously. However, since the latest charging depth is not known during use, the next battery may be selected after being used continuously a predetermined number of times. Specifically, for example, a flowchart of returning to step S10 after repeating the processes of steps S12 to S15 a predetermined number of times may be used.

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, the control device 4 performs battery selection and connection processing (step S21). The contents of this process are apparently shown in the flowchart (subroutine) in FIG. 5 as in the case described above (step S11). However, the criteria for selecting a battery are different from those described above.
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 Sx1).

  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 Sx2). 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 Sx3).

Returning to FIG. 4, 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 S22). 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 S23). 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 S24). Further, the control device 4 turns off the switches SP3 and SN3 after the discharge time of the capacitor C3 has elapsed.

  When the capacitors C1 to C3 are discharged and the battery is charged as described above, the next capacitor C4 is not used for charging the battery, but self (C4) is charged (capacitor charge) from the battery. As a battery for that purpose, a higher charging depth is suitable. Therefore, the control device 4 again performs battery selection / connection processing (step S25). The contents of this processing are shown in the flowchart (subroutine) in FIG.

  In FIG. 5, the control device 4 specifies the battery (any one of B1 to B8) having the highest charging depth for discharging as the battery to be selected next (step Sx1). 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 Sx2). 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 Sx3).

  Here, the control device 4 turns on the switches SP4 and SN4, configures a charging circuit (capacitor charging circuit) from the selected battery to the capacitor C4, and charges the capacitor C4 (step S26). Further, the control device 4 turns off the switches SP4 and SN4 after a predetermined charging time of the capacitor C4 has elapsed.

  And the control apparatus 4 repeats discharge (capacitor C1-C3) and charge (capacitor C4) by said step S21-S26 predetermined times (step S27), and will return to step S10, if predetermined number of times is reached.

  Thereafter, the same processing is performed. Since the battery to be charged is specified each time (steps S21, Sx1), when the currently selected battery is excluded from the next selection, the battery with the lowest charging depth is selected from the remaining batteries. 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 addition, regarding the capacitor C4, the battery that charges it is specified each time (steps S25, Sx1). Therefore, when the currently selected battery is excluded from the next selection, it is charged among the remaining batteries. The battery with the highest depth will be selected. In this way, batteries with a large remaining amount are sequentially selected. Note that “the charging depth is the highest among the remaining batteries” is an example of a selection criterion and does not necessarily have to be the highest. For example, it is possible to select at random from among those whose charging depth is a predetermined value or more.

  In the secondary battery charging / discharging device 1 configured as described above, it is the first power storage unit 2a that the external AC / DC converter 101 directly exchanges electric energy, 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.

In particular, when a plurality of secondary batteries are connected in series, the internal resistance and charging depth of each string tend to vary, but even in such a case, it can be used without problems by selecting and connecting. it can.
Moreover, although the voltage is often different if the type of battery is different, even in such a case, it can be used without any problem by selecting and connecting.

  In addition, by charging or discharging the three capacitors C1 to C3 constituting the first power storage unit 2a one by one in order, the first power storage unit 2a is discharged with a voltage of 1/3 of the voltage across the entire first power storage unit 2a. Can be used for charging. The “three capacitors” are merely examples, and as many series capacitors as necessary may be configured.

  In this way, by using a plurality of capacitors connected in series, even if the first power storage unit 2a as a whole has a high voltage rating, the voltage across each capacitor is a voltage that can be output by a secondary battery or a secondary battery. The voltage can be suitable for charging. 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.

  On the other hand, by providing the second power storage unit 2b dedicated to discharge to the outside, a predetermined voltage can be provided separately from the first power storage unit 2a based on the electrical energy of the secondary battery. In addition, even when the secondary battery is charged via the first power storage unit 2a, the second power storage unit 2b can provide a voltage to the outside separately. Therefore, for example, while the secondary battery is charged via the first power storage unit 2a by the regenerative power of the traveling motor, the secondary battery is discharged to the DC load for instrumentation or the like via the second power storage unit 2b. It is possible to supply a predetermined voltage (however, charging / discharging of the secondary battery is not performed at the same time in minute units, but is performed before and after time). Thereby, in a hybrid car, an electric vehicle or the like equipped with the secondary battery charging / discharging device 1, a DC12V battery (usually a lead storage battery) can be omitted.

  Moreover, the 1st electrical storage part 2a and the 2nd electrical storage part 2b are mutually connected in series. That is, the 1st electrical storage part 2a and the 2nd electrical storage part 2b are comprised by the several capacitors C1-C4 which comprise one serial body as a whole, and the intermediate | middle electric circuit Lm1 is shared by both. Therefore, the configuration of the entire power storage unit is simple and wasteful.

  Note that charging or discharging a plurality of capacitors connected in series one by one in order is only an example, and depending on the number of capacitors in series and the voltage, a plurality of capacitors of two or more are charged / discharged. It is also possible. In short, a plurality of capacitors may be charged by connecting the plurality of capacitors individually or in small groups to the selected secondary battery in order. The same applies when charging the secondary battery.

  Further, for example, when a plurality of capacitors C1 to C4 are provided as one string and these are provided in parallel in 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.

<< Another Example of Circuit Configuration for Secondary Battery Charge / Discharge Device >>
In the above embodiment, a configuration in which a plurality of capacitors are connected in series as the first power storage unit 2a is shown. This is preferable in that a high voltage can be handled by series connection. However, the number is not necessarily “multiple”.
FIG. 6 is a circuit diagram showing an example of a detailed circuit configuration of such a secondary battery charging / discharging device 1. The difference from FIG. 2 is that the first power storage unit 2a is a single capacitor C1, and accordingly, the switches SP2, SP3, SN2, and SN3 of FIG. 2 are not necessary. Also in this case, the connection device 3 is connected to a secondary battery selected from the plurality of secondary batteries B1 to B8 for the capacitors C1 and C4 to form a charging circuit or a discharging circuit (however, C4 is only charged) The basic configuration and operation are the same.

<Others>
In the above embodiment, the selection of the secondary battery is performed based on the charging depth, which is preferable. However, the secondary battery can be selected and charged or discharged at random. However, in this case, it is necessary to separately charge the battery so that the battery with a small remaining amount is not overdischarged.

  In the above embodiment, the number of batteries used for charging or discharging is basically one (one string). However, when the internal resistance is approximate, it is possible to use a plurality of strings. Yes, it does not exclude such use.

  2 and 6 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.

In addition, although the electric power storage system shown in FIG. 1 demonstrated and demonstrated the system mounted in vehicles, such as a hybrid car and an electric vehicle, the same system is mounted also in a train and regenerative electric power is stored in a battery. Can do. In addition, the second power storage unit can supply a predetermined voltage separately from the main voltage of the first power storage unit to a load other than the driving of the traveling motor.
Furthermore, said secondary battery charging / discharging apparatus 1 can also be applied to the grid connection with a commercial alternating current power supply, and the interconnection with DC load.

  FIG. 7 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 via the AC / DC converter 101. This configuration is preferable for optimizing the conversion efficiency. FIG. 8 is a connection diagram showing a main part of the power storage system when connected to a DC load. 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 system. In any case, there are two types (or more) of voltages to be supplied.
The first power storage unit 2a and the second power storage unit 2b can be further divided into a plurality of systems (corresponding to a plurality of loads). For example, in addition to the voltage of 200V as the first power storage unit, the second power storage unit can be divided into two (or another second power storage unit is provided in series) and a total of three voltages of 24V and 12V can be output. It is also possible to construct a series body of capacitors.

  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.

1: secondary battery charging / discharging device 2a: first power storage unit 2b: second power storage unit 3: connection device 5: A / D converter 101: AC / DC converter 102: DC / DC converters B1 to B8: secondary battery C1 ~ C4: capacitors SB1 to SB8, SP1 to SP4, SN1 to SN4, SM1 to SM8: switch

Claims (7)

A plurality of secondary batteries;
A first power storage unit configured by connecting a plurality of capacitors in series with each other and connected to an external converter;
A second power storage unit configured by a capacitor exclusively for external discharge other than the converter ;
All of the first power storage units are configured such that one capacitor is selected from the plurality of capacitors of the first power storage unit and connected to a secondary battery selected from the plurality of secondary batteries to form a charging circuit or a discharge circuit. And a connection device configured to connect a capacitor of the second power storage unit with a secondary battery selected from the plurality of secondary batteries to form a capacitor charging circuit. Secondary battery charge / discharge device. The secondary battery charge / discharge device according to claim 1, wherein the first power storage unit and the second power storage unit are connected in series to each other . The secondary battery charging / discharging device according to claim 1, wherein discharging from the second power storage unit to the outside is performed during charging of the first power storage unit by the conversion device. 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 the charging depth based on the voltage between both ends of each unused secondary battery that is not selected for connection with any of the capacitors, and when charging any of the secondary batteries The secondary battery charging / discharging device according to claim 4 , wherein a secondary battery having a relatively low charging depth is preferentially connected to the capacitor of the first power storage unit . The connecting device, for each of the secondary batteries of not selected also for connection of non-use with any of the capacitor determines the state of charge based on the voltage across, when discharging one of the secondary battery The secondary battery charging / discharging device according to claim 4, wherein a secondary battery having a relatively high charging depth is preferentially connected to any one of the capacitors. The power storage system provided with the secondary battery charging / discharging apparatus of Claim 1, and the converter which mediates the input-output of the said secondary battery charging / discharging apparatus and a desired system | strain .

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