JP5609488B2 - 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. 10 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) battery charging and discharging device of the present invention, a plurality of secondary batteries is constructed by connecting a plurality of capacitors in series with each other, both ends of which are connected in series, Ru is connected to an external converter A power storage unit, and a connection device configured to connect a part of the capacitors selected from the plurality of capacitors to a secondary battery selected from the plurality of secondary batteries to form a charging circuit or a discharging circuit;
The connection device obtains information including the usage history of the secondary battery, obtains a battery deterioration coefficient indicating the degree of deterioration, and selects the secondary battery. Ru der those characterized by choosing to favor following cell.

In the secondary battery charging / discharging device configured as described in ( 1 ) above, by connecting the power storage unit to an external device, it is the power storage unit that the external device directly exchanges electric energy. The secondary battery can be charged / discharged via the power storage unit. 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. 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.
In addition, when selecting a secondary battery, priority is given to a secondary battery with little deterioration based on the battery deterioration coefficient. The degree of deterioration of the secondary battery can be made uniform. Since deterioration is also the result of use, aligning the degree of deterioration is almost the same as equalizing the frequency of use.

( 2 ) In the secondary battery charging / discharging device of (1 ) , the battery deterioration coefficient is a function of a plurality of parameters, and the parameters include cumulative usage time of each secondary battery. Good.
In this case, the accumulated usage time, which is one of the deterioration factors of the secondary battery, can be reflected in the battery deterioration coefficient.

( 3 ) In the secondary battery charge / discharge device according to (1 ) , the battery deterioration coefficient is a function of a plurality of parameters, and the parameters may include the number of selections.
In this case, the number of selections that is one of the deterioration factors of the secondary battery can be reflected in the battery deterioration coefficient.

( 4 ) In the secondary battery charge / discharge device of (1 ) , the battery deterioration coefficient is a function of a plurality of parameters, and the parameters may include the temperature of each secondary battery.
In this case, the degree of deterioration of the secondary battery and the temperature related to the progress can be reflected in the battery deterioration coefficient.

( 5 ) In the secondary battery charge / discharge device of (1 ) , the battery deterioration coefficient is a function of a plurality of parameters, and the parameters may include cumulative input / output.
In this case, cumulative input / output, which is one of the deterioration factors of the secondary battery, can be reflected in the battery deterioration coefficient.

( 6 ) Moreover, in the secondary battery charging / discharging device according to (1 ) , the connection device includes a circuit for measuring the voltage across each secondary battery, and is not used for connection to the capacitor. About each secondary battery, you may make it obtain | require a charge depth based on the both-ends voltage.
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.

( 7 ) In the secondary battery charging / discharging device of ( 6 ), when charging any secondary battery, the connection device gives priority to a secondary battery that has a low charging depth and little deterioration. You may choose and connect to the capacitor.
In this case, instead of simply giving priority to secondary batteries with a low charging depth (that is, having a low remaining amount), priority is given to low deterioration at the same time. In addition, the usage frequency of the plurality of secondary batteries can be equalized.

( 8 ) In the secondary battery charge / discharge device of ( 6 ) above, when discharging any of the secondary batteries, the connection device gives priority to a secondary battery having a high charge depth and little deterioration. You may select and connect to a capacitor.
In this case, instead of simply giving priority to a secondary battery with a high charge depth (that is, having a lot of remaining power), priority is given to the fact that there is little deterioration. In addition, the usage frequency of the plurality of secondary batteries can be equalized.

( 9 ) 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. You can also.
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. Moreover, the usage frequency of a some secondary battery can be equalized, and each usable secondary battery can be used evenly. Thereby, the dispersion | variation in the lifetime of a secondary battery and the switch which comprises a connection apparatus is also suppressed.

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. FIG. 5 is a circuit diagram of a circuit portion (not shown in FIG. 4) that constitutes a connection device of the secondary battery charge / discharge device together with FIG. It is a flowchart which shows an example of the process regarding acquisition of the information regarding a charge depth and internal resistance. It is a flowchart which shows an example of the process regarding the calculation of a battery deterioration coefficient. 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, and are, for example, FETs. Moreover, it is preferable that it is a wide band gap semiconductor comprised with materials, such as SiC, GaN, or a diamond. FETs are suitable for high-speed response, and SiC-FETs are particularly excellent in terms of high-speed response and withstand voltage. In addition, semiconductors made of these materials have an overwhelmingly superior dielectric strength compared to silicon, and can withstand a voltage of 1000 V or higher with a low on-resistance.
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.

  In the part excluding the power storage unit 2 and the secondary batteries B1 to B8 in FIG. 4, any one of the capacitors C1 to C4 is connected to a secondary battery selected from the plurality of secondary batteries B1 to B8 to be a charging circuit or a discharging circuit. It becomes the connection device 3 which comprises.

  FIG. 5 is a circuit diagram of a circuit portion constituting the connection device 3 of the secondary battery charging / discharging device 1 together with FIG. 4 although not shown in FIG. In the figure, temperature sensors T1 to T8 are provided in the casings of the secondary batteries B1 to B8, respectively. The outputs of the temperature sensors T1 to T8 are converted into digital values by the A / D converters 81 to 88, respectively, and then input to the control device 4. Further, currents (both outflow and inflow) flowing through the secondary batteries B1 to B8 are detected by current sensors H1 to H8 using, for example, Hall elements. Outputs of the current sensors H1 to H8 are converted into digital values by the A / D converters 71 to 78, respectively, and then input to the control device 4.

  A display device (display) 9 for displaying information and an input device 10 for data input are connected to the control device 4. In addition, these apparatuses 9 and 10 can also be installed remotely from the secondary battery charging / discharging apparatus 1 via a communication line.

  Next, operation | movement of said secondary battery charging / discharging apparatus 1 is demonstrated with reference to a flowchart. 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 process related to the acquisition of battery information includes (a) a process for obtaining a charging depth and internal resistance, and (b) a process for obtaining a battery deterioration coefficient indicating the degree of deterioration based on information such as a battery usage history. .

  First, with respect to (a) above, the photocouplers Pc1 to Pc8, the A / D converter 5 and the control device 4 constitute a circuit for measuring the voltage across each of the secondary batteries B1 to B8. And internal resistance information is acquired. 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. 6 is a flowchart illustrating an example of processing related to acquisition of information on the charging depth and internal resistance. 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, 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 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 manner, the information on the charging depth and the internal resistance is cyclically repeated to update the information.

For example the battery is p number, any number from 1 to p and i, the state of charge of the i-th cell and d _i. The charge depth d _i is normalized and expressed as a value of 0 ≦ d _i ≦ 1, 1 is a fully charged state, and the closer to 1, the more remaining.
On the other hand, 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. However, in this embodiment, a criterion different from the internal resistance is used in detecting the deterioration of the battery.

Next, the above item (b) regarding battery deterioration will be described.
When i is used similarly to the charging depth and the battery deterioration coefficient is k _i , k _i is a function of a plurality of parameters. For example, these parameters are defined as follows:
First, since the battery deteriorates according to the accumulated use time, the parameter k _ia of the accumulated use time t of the battery, that is, k _ia (t) is reflected in the battery deterioration coefficient.
Further, since it is understood that the battery deteriorates according to the number of times selected by the switches SB1 to SB8, the parameter k _ib of the selected number n, that is, k _ib (n) is reflected in the battery deterioration coefficient.

In addition, since it is understood that the battery temperature is related to the degree of deterioration and its progress, the parameter k _{ic of} the battery temperature (for example, the mean square of the temperature) T, that is, k _ic (T) is reflected in the battery deterioration coefficient. Let
Further, since the battery deteriorates in accordance with the cumulative input / output, the parameter k _{id of} the cumulative input / output (for example, the integrated value of the current flowing out from the battery or flowing into the battery) x, that is, k _id (x) is used as the battery deterioration coefficient. To reflect.

Therefore, the battery deterioration coefficient k _i is
k _i = k _i (k _ia , k _ib , k _ic , k _id )
_{= K i (k ia (t} ), k ib (n), k ic (T), k id (x))
It becomes. Specifically, for example,
k _i = 1− (1−k _ia (t)) (1−k _ib (n)) (1−k _ic (T)) (1−k _id (x)) (1)
It becomes. Parameters and coefficients are normalized, and 0 ≦ k _ij ≦ 1 (j = a, b, c, d), and 0 ≦ k _i ≦ 1 (i = 1, 2,..., P). is there. The closer the battery deterioration coefficient k _i is to 1, the more the battery is deteriorated, and the closer to 0, the less the deterioration.

In the above formula (1), if any one of the parameters k _ia (t), k _ib (n), k _ic (T), and k _id (x) becomes 1, regardless of the other parameters. Since the term represented by the product of the parentheses regarding the four parameters on the right side of the equation (1) is 0, the battery deterioration coefficient k _i is always 1. This means that even if one element (parameter) is in a state where the battery is most deteriorated, the battery as a whole is treated as being most deteriorated.

A function serving as a criterion for selecting a battery is f when the battery is charged and g when the battery is discharged. f and g are both functions of (d _i , k _i ). At the time of charging, _i , which is the largest function value among the values of f (d _i , k _i ) for the p batteries, that is, the i-th battery is selected. Similarly, at the time of discharging, _i , which is the largest function value among the values of g (d _i , k _i ) for the p batteries, that is, the i-th battery is selected.

For example, the simplest function is
f (d _i , k _i ) = 1 / (d _i · k _i ) (2)
g (d _i , k _i ) = d _i / k _i (3)
Can be considered. That is, when the battery is charged, the function value is increased by both the small charging depth and the small deterioration of the battery according to the equation (2). If the degree of deterioration of the battery is the same, the function value increases as the charging depth decreases. If the charging depth is the same, the function value increases as the deterioration decreases. On the other hand, at the time of discharging the battery, the function value is increased by both the large charging depth and the small deterioration of the battery according to the equation (3). If the degree of deterioration of the battery is the same, the function value increases as the charging depth increases. If the charging depth is the same, the function value increases as the deterioration decreases.

  In addition, although the simple example was shown as said function f and g, the function f and g can select experimentally or empirically appropriate thing according to the structure of a secondary battery charging / discharging apparatus. Each parameter and function may be stored in the control device 4 in advance, but may be set (or changed) from the input device 10 while viewing the display device 9. Moreover, you may enable it to select each parameter and function according to the kind of battery. Furthermore, the upper limit value and lower limit value of the functions f and g may be set. In addition, displaying various information regarding the battery on the display device 9 can also be used for maintenance management.

  FIG. 7 is a flowchart illustrating an example of processing related to the calculation of the battery deterioration coefficient executed by the control device 4. First, the control device 4 determines whether or not a battery is selected (used) (step S01). Here, when the battery is selected, the control device 4 stores the number of selections n (step S02), measures the accumulated usage time t (step S03), and calculates the integrated value of the current as the accumulated input / output x (step S03). S04) and temperature T measurement of each battery (step S05). Then, the control device 4 calculates the battery deterioration coefficient ki (step S06). Thereafter, the process returns to step S01 and the same processing is performed. If no battery is selected, steps S02 to S04 are omitted, and only steps S05 and S06 are performed.

FIG. 8 is a flowchart illustrating an example of processing related to the 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).

Here, based on the above-described charging depth and battery deterioration coefficient, the control device 4 selects the battery (one of B1 to B8) that has the largest function g value for discharging next. (Step S11). In the case where the value of g there are multiple same cell, for example, such as choosing whichever battery deterioration coefficient k _i is small, it is sufficient to define a pre-selected criteria.

  Next, the control device 4 turns off the switch (any one of SB1 to SB8) corresponding to the currently selected battery and disconnects the battery from the system (step S12). 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 S13). Then, the control device 4 turns on the switches SP1 and SN1, configures a discharge circuit from the selected 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 selected 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, configures a discharge circuit from the selected 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 selected 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 specified each time (step S11), when the currently selected battery is excluded from the next selection, the battery having the largest function g value is selected from the remaining batteries. Become. In this way, not only priority is given to a battery with a large remaining amount, but also a priority is given to a battery with little deterioration based on the battery deterioration coefficient. The degree of deterioration of each battery can be made uniform. Since deterioration is also the result of use, aligning the degree of deterioration is almost the same as equalizing the frequency of use. By equalizing the use frequency of the batteries, each usable battery can be used without bias. Thereby, the dispersion | variation in the lifetime of each battery and switch SB1-SB8 is also suppressed.

It is also possible to select and use the same battery continuously. For example, the process of steps S14 to S17 may be repeated for a predetermined number of times and then returned to step S10. However, this is limited to short-time use. It is not preferable to use the same battery for a long time.
In addition, when a battery is selected only with a high charging depth, the same battery may be frequently selected and used. In this case, deterioration of the battery is accelerated. In addition, since the life of the battery switch (any one of SB1 to SB8) is shortened, the burden of maintenance work is increased.

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 selects a battery (any one of B1 to B8) having the largest function f value for charging as a battery to be next selected based on the above-described charging depth and battery deterioration coefficient. It identifies (step S21). Incidentally, if the value of f there are multiple identical batteries, for example, such as choosing whichever battery deterioration coefficient k _i is small, it is sufficient to define a pre-selected criteria.

  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 identified each time (step S21), when the currently selected battery is excluded from the next selection target, the battery with the largest function f value is selected from the remaining batteries. Will be. In this way, not only priority is given to a battery with a small remaining amount, but also priority is given to a battery with low deterioration based on the battery deterioration coefficient. The degree of deterioration of each battery can be made uniform. Since deterioration is also the result of use, aligning the degree of deterioration is almost the same as equalizing the frequency of use. By equalizing the use frequency of the batteries, each usable battery can be used without bias. Thereby, the dispersion | variation in the lifetime of each battery and switch SB1-SB8 is also suppressed.

  Note that if a battery is selected only with a low charging depth, the same battery may be frequently selected and charged. In this case, the deterioration of the battery is accelerated. In addition, since the life of the battery switch (any one of SB1 to SB8) is shortened, the burden of maintenance work is increased.

  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.

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 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 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 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. 9 is a circuit diagram illustrating another example of the detailed circuit configuration of the secondary battery charge / discharge 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 basic configuration and operation of the connecting device 3 is that the capacitor C1 is connected to a secondary battery selected from the plurality of secondary batteries B1 to B8 to form a charging circuit or a discharging circuit.

  Moreover, in the said embodiment, although the battery used for charge or discharge was fundamentally one (1 string), when a battery deterioration coefficient and the charge depth are approximated, it uses by multiple strings. It is also possible and does not exclude such use.

  4 and 9 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 devices B1 to B8: Secondary batteries C1 to C4: Capacitors Pc1 to Pc8: Photocouplers

Claims (9)

A plurality of secondary batteries;
Is constructed by connecting a plurality of capacitors in series with each other, both ends of which are connected in series, and a power storage unit that will be connected to an external converter,
A part of capacitors selected from the plurality of capacitors, and a connection device configured to connect a secondary battery selected from the plurality of secondary batteries to form a charging circuit or a discharging circuit;
The connection device obtains information including the usage history of the secondary battery, obtains a battery deterioration coefficient indicating the degree of deterioration, and selects the secondary battery. A secondary battery charging / discharging device, wherein the secondary battery is selected to give priority. The secondary battery charging / discharging device according to claim 1, wherein the battery deterioration coefficient is a function of a plurality of parameters, and the parameters include a cumulative usage time of each secondary battery . The secondary battery charging / discharging device according to claim 1, wherein the battery deterioration coefficient is a function of a plurality of parameters, and the parameters include the number of selections . The secondary battery charging / discharging device according to claim 1, wherein the battery deterioration coefficient is a function of a plurality of parameters, and the parameters include a temperature of each secondary battery . The secondary battery charging / discharging device according to claim 1, wherein the battery deterioration coefficient is a function of a plurality of parameters, and the parameters include cumulative input / output . The connection device includes a circuit for measuring a voltage at both ends of each secondary battery, and for each unused secondary battery not selected for connection to the capacitor, a charge depth is obtained based on the voltage at both ends. Item 12. The secondary battery charge / discharge device according to Item 1 . The secondary battery according to claim 6, wherein when the secondary battery is charged with any secondary battery, the secondary battery is selected so as to give priority to a secondary battery having a low charging depth and little deterioration, and connected to the capacitor. Battery charge / discharge device. The secondary battery according to claim 6 , wherein when the secondary battery is discharged , the secondary battery is selected to give priority to a secondary battery having a high charging depth and little deterioration, and connects to the capacitor. Battery charge / discharge device. 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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