JP2012034439A - Dc power supply and power storage system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DC power supply capable of effectively utilizing a plurality of secondary batteries whose remaining amounts vary and a power storage system using the same.SOLUTION: The DC power supply comprises: a plurality of batteries B1 to B12, which are secondary batteries; a connection device 2 capable of connecting both ends of each battery to arbitrary battery positions P11 to P34 on a circuit to constitute the circuit in which these batteries are connected in series and parallel; and a controller to monitor current performance of each battery and designate the connection device 2 battery positions to be selected based on the monitoring results.

Description

  The present invention relates to a DC power supply device that uses a large number of secondary batteries connected in series and parallel.

  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. 15 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. Three sets of strings St1, St2, and St3 are connected in parallel to each other. During charging, a current flows in the direction of the arrow in the figure, and electric power is stored. At the time of discharging, current flows out from the battery in the direction opposite to the arrow direction in the figure, and electric power is supplied to the outside.

  Here, the currents i1, i2, and i3 that flow through the strings St1, St2, and St3 differ depending on the total internal resistance of the entire string, but the current that flows in one string is the same for all the batteries that form the string. Value. Therefore, for example, when discharging from a battery and supplying power to the outside, if the battery with the least remaining amount reaches the discharge limit, other batteries connected in series cannot be used even if the remaining amount is sufficient . In addition, when any one of the batteries is fully charged at the time of charging, the other batteries cannot be charged until they are fully charged in order to prevent overcharging.

  In this way, when charging / discharging is performed using a large number of batteries with different remaining amounts, one of the batteries pulls the entire leg, so that the overall charging / discharging performance cannot be fully utilized. There is a problem. 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 direct-current power supply device that can more effectively utilize a plurality of secondary batteries whose remaining amounts vary, and an electric power storage system using the same. And

  (1) The DC power supply device of the present invention is configured such that a plurality of batteries as secondary batteries and a circuit in which the plurality of batteries are connected in series and parallel are connected to both ends of each battery by any battery on the circuit. A connection device that can be connected to a position, and a control device that monitors the current capacity of each battery and instructs the connection device of the battery position to be selected based on the monitoring result. .

  In the DC power supply device configured as described above, the battery position in the circuit is not fixed but can be freely changed by the connection device. Therefore, based on the current capacity of each battery, for example, by connecting batteries with similar remaining capacity in series to each other, it is possible to effectively use each battery by connecting it to a battery position where the battery capacity is easily exhibited. it can.

(2) In the DC power supply device of (1), the control device detects the remaining amount of each battery, and instructs the connection device to connect the batteries having similar remaining amounts in series with each other. Also good.
In this case, a plurality of batteries having similar remaining amounts are connected to each other in series, so that variations in the remaining amount are reduced, and there is no battery having a relatively small remaining amount in the series body. Therefore, all the batteries connected in series can exhibit their own discharge capability in the same way. In addition, when charging, the variation in the remaining amount is reduced, and there is no battery having a particularly large remaining amount in the series body. Therefore, all the batteries connected in series can be charged in the same way.

(3) In the DC power supply device of (1), the connection device may have a switch on a path connecting both ends of each battery to each battery position on the circuit.
In this case, the battery can be easily connected to an arbitrary battery position by turning on only the switch corresponding to any one of the battery positions and turning off the others. Moreover, if all the switches are turned off, the battery can be disconnected from the circuit.

(4) In the DC power supply device of (2), the control device may periodically detect the remaining amount of each battery and operate the connection device based on the detection result.
In this case, it is possible to change the battery position periodically and always connect the batteries whose remaining amounts are approximate to each other in series.

(5) Further, in the DC power supply device of (3) above, for each battery, the control device turns off all corresponding switches to make the battery open, and the voltage across the battery measured in the battery open state is measured. The remaining amount may be detected based on the above.
In this case, since the battery is in a state in which no current flows, the voltage at both ends becomes an electromotive force, and based on this, the remaining amount (charging depth) can be detected by the Nernst equation.

(6) In the DC power supply device of (3), the switch is preferably a semiconductor switching element.
The semiconductor switching element is suitable for high-speed response and has excellent durability.

(7) In the DC power supply device of (6), the semiconductor switching element is preferably an FET, a SiC semiconductor, or a SiC-FET.
These elements are suitable for high-speed response. In particular, SiC-FET is most excellent in terms of high-speed response and withstand voltage.

  (8) On the other hand, in the power storage system of the present invention, in order to form a circuit in which a plurality of batteries as secondary batteries and the plurality of batteries are connected in series and parallel, both ends of each battery are arbitrarily connected on the circuit. DC power supply having a connection device that can be connected to the battery position of the battery, and a control device that monitors the current capacity of each battery and instructs the connection device of the battery position to be selected based on the monitoring result And a conversion device that mediates between the DC power supply device and a desired power supply system.

  In the DC power supply device in the power storage system configured as described above, the battery position in the circuit is not fixed but can be freely changed by the connection device. Therefore, based on the current capacity of each battery, for example, by connecting batteries with similar remaining capacity in series to each other, it is possible to effectively use each battery by connecting it to a battery position where the battery capacity is easily exhibited. it can.

  According to the direct-current power supply device and the power storage system of the present invention, it is possible to more effectively utilize a plurality of secondary batteries whose remaining amounts vary.

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. As an example of a DC power supply device according to an embodiment of the present invention, a circuit in which 12 batteries are connected in series and parallel is shown first. It is the figure which removed the battery from FIG. 4 and showed those battery positions. It is a figure which shows the number of wiring required with respect to the outside, when connecting a battery from the outside with respect to the virtual circuit which a battery should be connected in series and parallel. It is a circuit diagram of the connection circuit which provided the external switch circuit with respect to the virtual serial / parallel circuit. It is a correspondence figure which shows which battery position can connect both ends of a battery when which switch is turned on. It is the circuit diagram which provided the connection apparatus similar to FIG. 7 about each of each of 12 batteries. It is a circuit diagram which shows an example of a structure of the control apparatus which monitors the residual amount (charge depth) of a battery. It is a flowchart which shows operation | movement of a DC power supply device. It is a subroutine which shows the detail of the process of step K1 of FIG. It is a flowchart of a subroutine as a modified version of FIG. It is a figure which shows the example of a series-parallel circuit different from FIG. It is a connection diagram which shows an example of the state which connected the string 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, a power storage system linked to an AC load system is constituted by an AC / DC converter 101 that converts AC / DC into each other and a DC power supply device 1.

The plurality of batteries (secondary batteries) B1 to Bn are connected to each other in series to form a string. The plurality of strings St1, St2,..., Stm are connected in parallel to each other. The numerical values of n and m can be freely configured as necessary.
As the secondary battery, a lithium ion battery, a lead storage battery, a nickel metal hydride battery, and other various rechargeable batteries can be used.

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 as an intermediary between the DC power supply 1 and a desired power supply system.

《DC power supply device》
FIG. 4 shows a circuit in which twelve batteries B <b> 1 to B <b> 12 that are secondary batteries are connected in series and parallel as an example of the DC power supply device 1. It should be noted that the 12 series of 3 series × 4 parallel is simply a numerical value that is easy to see for explanation, and in fact, a large number of series necessary for the grid connection and the required load system. Or a parallel number is required.

  If the batteries are fixedly connected as shown in FIG. 4, it is natural that “changing seats” of the batteries cannot be realized except by recreating the circuit. When used in a fixed connection, for example, the remaining amount of one battery in three series bodies is significantly smaller than the other two, and when the discharge limit is reached, no further discharge is possible. Therefore, the remaining two batteries that have a remaining capacity will be charged. With this, the ability of each battery cannot be fully utilized.

Therefore, consider a connection device that changes seats, that is, changes the battery position.
FIG. 5 is a diagram showing the battery positions P11 to P34 after removing the batteries B1 to B12 from FIG. If the twelve batteries can be connected from the outside to any of the twelve battery positions P11 to P34, the batteries can be “replaced”.

  FIG. 6 is a diagram illustrating the number of wirings required for the outside when the battery is connected from the outside to a virtual circuit to which the battery is to be connected in series and parallel. That is, in addition to the positive-side electric circuit Lp and the negative-side electric circuit Ln, a total of ten electric circuits L1 to L8 in the middle of the series are required to connect the batteries.

  FIG. 7 is a circuit diagram of the connection circuit 2 in which an external switch circuit is provided for the virtual series-parallel circuit. The electric paths L1 to L8 may be a positive electrode of the battery B1 and a negative electrode depending on how they are connected. Therefore, 18 switches are required as a whole. Thus, as shown in the figure, both ends of the battery B1 can be connected to all the battery positions P11 to P34 via the ten electric circuits via the 18 switches S1 to S18.

  As said switch S1-S18, the semiconductor switching element suitable for a high-speed response and excellent in durability is suitable, for example, is FET, SiC semiconductor, or SiC-FET. These elements are suitable for high-speed response. In particular, SiC-FETs are most excellent in terms of high-speed response and withstand voltage.

  FIG. 8 is a correspondence diagram showing which battery positions P11 to P34 can be connected to both ends of the battery B1 by turning on which switch. A black circle in the figure indicates that the switch is turned on, and the switch is off when there is no black circle. For example, if the switches S1 and S2 are turned on and the others are turned off, the battery B1 is connected to the battery position P11. If the switches S1 and S3 are turned on and the others are turned off, the battery B1 is connected to the battery position P12.

  Similarly, both ends of the battery B1 can be connected to any one of the battery positions P11 to P34 by turning on the two switches in the corresponding diagram. In this way, by turning on only the switch corresponding to any one of the battery positions and turning off the others, the battery can be easily connected to an arbitrary battery position. Moreover, if all the switches are turned off, the battery can be disconnected from the circuit.

  FIG. 9 is a circuit diagram in which the same connection device 2 is provided for each of the twelve batteries B1 to B12 (although the illustration of the batteries B2 to B11 in the middle is omitted, the configuration is the same). is there.). However, the ten electric circuits Lp, Ln, L1 to L8 connected to the battery position are shared by 12 sets of switch groups. With such a connection device 2, both ends of the 12 batteries B <b> 1 to B <b> 12 can be connected to 12 battery positions P <b> 11 to P <b> 34 in any combination (arrangement).

  Next, a control device that gives instructions on how to connect them will be described. FIG. 10 is a circuit diagram illustrating an example of the configuration of the control device 3 that monitors the remaining amount (charge depth) of the batteries B1 to B12. Here, the part other than the batteries B <b> 1 to B <b> 12 is the control device 3. This circuit is provided together with the circuit of FIG. In FIG. 10, the positive electrodes of the batteries B1 to B12 are connected to the positive-side measurement circuit MLp via the positive-side switches Sp1 to Sp12, respectively. In addition, the negative electrodes of the batteries B1 to B12 are connected to the measurement-side electric circuit MLn on the negative electrode side via the switches Sn1 to Sn12 on the negative electrode side, respectively. As the switches Sp1 to Sp12 and Sn1 to Sn12, for example, photocouplers are preferable from the viewpoint of insulation, but other semiconductor switching elements can also be used.

  The positive and negative measurement circuits MLp and MLn are connected to the input terminal of the A / D converter 4. An output of the A / D converter 4 is provided to a control unit 5 including a CPU. The control unit 5 gives an on / off command to the drive unit (driver) 6 to each switch (switches S1 to S18 × 12 sets, switches Sp1 to Sp12, switches Sn1 to Sn12).

  The switches Sp1 to Sp12 and Sn1 to Sn12 are one set arranged on the positive electrode side and the negative electrode side with respect to the batteries B1 to B12, that is, (Sp1 and Sn1), (Sp2 and Sn2),. And Sn11) or (Sp12 and Sn12) are driven by the control unit 5 and the drive unit 6 so that they are always turned on / off simultaneously. Further, when any one set of switches is turned on, the other 11 sets are off. When any one of the switches is turned on, the voltage across the corresponding battery is input to the A / D converter 4. The A / D converter 4 converts the input analog voltage value into a digital voltage value and provides it to the control unit 5.

  Thus, the both-ends voltage of each battery B1-B12 can be measured. In the connection device 2, the both-end voltage measured for a battery in which all the related switches S <b> 1 to S <b> 18 are off, that is, a battery that is not used represents an electromotive force. If the electromotive force is known, the remaining amount (charging depth) can be obtained using the Nernst equation.

Next, the operation of the DC power supply device configured as described above will be described with reference to the flowcharts of FIGS.
For example, it is assumed that the DC power supply device 1 in which 12 batteries B1 to B12 are connected in series and parallel as shown in FIG. In FIG. 11, first, the control unit 5 (FIG. 10) obtains the remaining amount of each battery (step K1).

  FIG. 12 is a subroutine showing details of the process in step K1. In FIG. 12, the control unit 5 turns off all output switches S1 to S18 of one battery to be measured (step K11). As a result, the battery is disconnected from the series-parallel circuit, and the battery is opened. Although the battery string is disconnected, no current flows through the string of the battery. However, since the subroutine process is finished in a short time, the power supply is not greatly affected.

  Subsequently, the control unit 5 turns on the measurement switches Spx, Snx (x is any one of 1 to 12) of the battery (step K12). And the control part 5 measures the both-ends voltage of the said battery (step K13). The both-end voltage measured here is an electromotive force, and the control unit 5 obtains the remaining battery level (charging depth) by the Nernst equation based on the electromotive force. And the control part 5 repeatedly performs step K11-13 until it measures the both-ends voltage about all the batteries, and calculates | requires the residual amount of a battery (step K14). Further, the control unit 5 stores the electromotive force and remaining amount data for each battery, and updates the data every time the same processing is performed next time, and always holds the latest data. When the measurement is completed for all the batteries (Yes in Step K14), the control unit 5 turns off all the measurement switches Sp1 to Sp12 and Sn1 to Sn12, and proceeds to Step K2 in FIG.

  In FIG. 11, the control unit 5 sorts the batteries B1 to B12 in descending order of remaining amount (step K2), and divides them into four groups in order of increasing remaining amount (step K3). The order in which the remaining amount is large is merely an example, and conversely, the order may be small. In short, the three groups in each group are sorted so that the remaining battery levels are similar (including the same).

  Then, the control unit 5 operates the connection device 2 via the drive unit 6 so as to form one string in which three batteries of one group are connected in series with each other, and the corresponding battery positions P11 to P34. Each battery is connected (step K4). In this way, in each of the four strings, three batteries having similar remaining amounts are connected in series.

  That is, in the DC power supply device 1 configured as described above, the battery position in the series-parallel circuit is not fixed but can be freely changed by the connection device 2, so that the batteries having similar remaining amounts are connected in series with each other. As a result, the variation in the remaining amount is reduced, and there is no battery having a relatively small remaining amount in the series body (one string). Therefore, all the batteries connected in series can exhibit their own discharge capability in the same way. That is, each battery can be used effectively.

  Further, when a predetermined time elapses in a state where each battery is connected to each battery position, the state of each battery changes. Therefore, the control unit 5 waits for a predetermined time to elapse (step K5), and when it elapses, executes the same processing from step K1 again. In this way, it is possible to change the battery position periodically and always connect the batteries whose remaining amounts are approximate to each other in series (one string).

  In the above description, the DC power supply device 1 in which the twelve batteries B1 to B12 are connected in series and parallel has been described as supplying current to the outside by discharging, but each battery is charged from the outside. In such a case, the same processing can be applied. As a result, even during charging, variation in the remaining amount of each battery in one string is reduced, and there is no battery having a particularly large remaining amount in the series body. Therefore, all the batteries connected in series can be charged in the same way. That is, also in this case, each battery can be used effectively.

<Others>
In the above-described embodiment, attention is paid only to the remaining capacity as the capacity of the battery to be monitored. For example, the internal resistance is an index indicating the capacity of the battery. Among new articles, the internal resistance is relatively small, and the internal resistance increases as it deteriorates. The internal resistance can be obtained based on a comparison between the voltage across the battery during discharge and the above-described electromotive force.

  For example, FIG. 13 is a flowchart of a subroutine as a modified version of FIG. In FIG. 13, the control unit 5 first turns on a battery Spx, Snx (x is any one of 1 to 12) for measuring a battery in use (discharged) as a measurement target. (Step K10). And the control part 5 measures a both-ends voltage (step K11). This both-ends voltage includes a voltage drop due to an internal resistance.

  Next, the control unit 5 turns off all the output switches S1 to S18 of the battery (step K12). As a result, the battery is disconnected from the series-parallel circuit, and the battery is opened. Although the battery string is disconnected, no current flows through the string of the battery. However, since the subroutine process is finished in a short time, the power supply is not greatly affected.

  Then, the control part 5 measures the both-ends voltage of the said battery (step K13). The both-end voltage measured here is an electromotive force, and the control unit 5 obtains the remaining battery level (charging depth) by the Nernst equation based on this electromotive force. Moreover, the control part 5 calculates | requires internal resistance based on the comparison of the both-ends voltage measured by step K11, and an electromotive force.

  And the control part 5 repeatedly performs the same measurement process (step K10-K13) about all the batteries (step K14). In addition, the control unit 5 stores the electromotive force, the remaining amount, and the internal resistance data for each battery, and updates the data every time the same processing is performed, and always holds the latest data. When the measurement is completed for all the batteries (Yes in step K14), the control unit 5 turns off all the measurement switches Sp1 to Sp12 and Sn1 to Sn12, and returns to step K2 in FIG.

  By monitoring the internal resistance in addition to the remaining amount as described above, batteries with a very large internal resistance are excluded from being included in the string while being basically grouped based on the remaining amount. Or some warning may be issued to prompt the exchange.

  In the above embodiment, the series-parallel circuit as shown in FIG. 4 has been described as an example. However, for example, when the same 12 batteries are used, a series-parallel circuit as shown in FIG. In this case, the series body is constituted by three parallel sets of two batteries connected in series with each other. Further, two sets of the series bodies are connected in parallel with each other to constitute the entire circuit. Yes. In such a case, each battery should just be arrange | positioned in a battery position so that the residual amount as a whole of two parallel bodies may mutually approximate in 3 sets which comprise a serial body. For example, when batteries are arranged as shown in the figure, (B1 + B9), (B5 + B7), (B11 + B3) are approximate to each other, and (B4 + B8), (B10 + B2), (B12 + B6) are Approximate.

  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 direct-current power supply device of the present invention, it is possible to configure a power storage system by effectively utilizing batteries having a variation in remaining amount while skillfully rearranging the batteries.
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 direct-current power supply device of the present invention, it is possible to effectively use such a used secondary battery having a variation in the remaining amount and the internal resistance, and to construct a power storage system at a low cost.

1: DC power supply device 2: Connection device 3: Control device 101: AC / DC converter 102: DC / DC converter B1-B12: Batteries P11-P34: Battery positions S1-S18: Switch

Claims (8)

A plurality of secondary batteries,
A connection device capable of connecting both ends of each battery to an arbitrary battery position on the circuit in order to configure a circuit in which the plurality of batteries are connected in series and parallel;
A direct-current power supply device comprising: a control device that monitors a current capacity of each battery and instructs the connection device of a battery position to be selected based on a monitoring result.   The DC power supply device according to claim 1, wherein the control device detects the remaining amount of each battery and instructs the connecting device to connect batteries having similar remaining amounts in series.   The DC power supply device according to claim 1, wherein the connection device has a switch on a path connecting both ends of each battery to each battery position on the circuit.   The DC power supply device according to claim 2, wherein the control device periodically detects a remaining amount of each battery and operates the connection device based on the detection result.   4. The direct current according to claim 3, wherein for each battery, the control device turns off all corresponding switches to bring the battery into an open state, and detects the remaining amount based on a voltage across the battery measured in the battery open state. Power supply.   The DC power supply device according to claim 3, wherein the switch is a semiconductor switching element.   The DC power supply device according to claim 6, wherein the semiconductor switching element is an FET, a SiC semiconductor, or a SiC-FET. A plurality of batteries as secondary batteries, and a connection device capable of connecting both ends of each battery to an arbitrary battery position on the circuit to form a circuit in which the plurality of batteries are connected in series and parallel; A direct current power supply device having a control device for monitoring the current capacity of each battery and instructing the connection device of the battery position to be selected based on the monitoring result; and
A power storage system comprising a conversion device that mediates between the DC power supply device and a desired power supply system.

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