JP2002142375A - Power storage system and control method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a power storage system wherein the charging voltages of two sets of storage battery modules are equalized using a single charger. SOLUTION: The positive pole of a first storage battery module 16a and the anode of a first diode 13a and the negative pole of a second storage battery module 16b and the cathode of a second diode 13b are series connected with each other, respectively, and the diodes 13a and 13b are parallel connected with switching elements 14a and 14b, respectively. A third switching element 15 is connected between the anode of the first diode 13a and the cathode of the second diode 13b. With this constitution, the first storage battery module 16a and the second storage battery module 16b are charged independently from each other by turning on and off the two switching elements 14a and 14b. Thus passage of overcurrent due to differences in terminal voltage between the battery modules and back flow of currents to the charger due to high voltage during discharging are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power storage device and a control method thereof, and more particularly, to a charging device for a power storage device connected in parallel and a control method thereof.

[0002]

2. Description of the Related Art Conventionally, a power storage device and a control method thereof are
In general, the present invention is applied to a charging / discharging device having a higher performance and a control method thereof for a storage battery in which a plurality of storage batteries are used in parallel.

In the prior art, when the storage battery modules are connected in parallel and charged / discharged, if the terminal voltages of the respective storage battery modules are different, an excessive current flows from the higher voltage storage battery module to the lower voltage storage battery module. Is supplied and is known to adversely affect both storage battery modules.

In order to solve the above problem, a circuit shown in FIG. 7 is generally known. FIG. 7 showing a general prior art example 1 shows that each positive electrode of two sets of storage battery modules 1a and 1b is connected to one terminal of a charger 2, and each negative electrode of storage battery modules 1a and 1b Diode 3
a, 3b through the anode and cathode
Is connected to the other terminal.

In this configuration, if, for example, the terminal voltage of the storage battery module 1a> the terminal voltage of the storage battery module 1b, the current flowing from the storage battery module 1a to the storage battery module 1b is reduced by the reverse current preventing diode 3a.
Therefore, no excessive current flows between the storage battery modules. When the terminal voltage of the storage battery module 1a <the terminal voltage of the storage battery module 1b, the backflow prevention diode 3b is reverse-biased to prevent the current flowing from the storage battery module 1b into the storage battery module 1a.

However, in the configuration of FIG. 7, since the voltage drop of the diodes 3a and 3b when charging the storage battery modules 1a and 1b is large, the loss generated in the diodes cannot be ignored. A configuration in which this point is improved is the invention of Japanese Unexamined Patent Publication No. Hei 9-140065 of Invention Example 1 of the prior application.

FIG. 8 shows a basic circuit configuration of Japanese Patent Application No. 9-140065. This circuit comprises a diode 1a,
1b are connected in parallel with the switching elements 4a, 4b, respectively, and the charging control circuits 6a, 6b connect the switching elements 4a, 4b.
b on / off is controlled. Although omitted, 6b
Has the same configuration as the charge control circuit 6a and performs the same operation. Next, the operation of the charging device will be described in detail with reference to FIG.

In the initial state, the switch elements 4a and 4b are in the off state and the terminal voltage of the battery module 1a> the terminal voltage of the battery module 1b. In this case, the diode 3a is reverse-biased and the diode 3b is forward-biased. When reverse bias detection is operated so that the switching element 4b is turned on when the diode 3b is forward-biased, the equivalent resistance of the charging path of the storage battery module 1b having a lower voltage is lower than that of the storage battery module 1a having a higher voltage. The charging current from the charger 2 mainly flows into the storage battery module having a lower voltage. In this case, the current from the storage battery module having the higher voltage is blocked by the diode 3a and does not flow.

As the charging of the storage battery module 1b having a lower voltage progresses, the terminal voltage increases, and when the terminal voltages of the storage battery modules 1a and 1b become equal, the diode 3a also shifts to the forward bias state, The detection 5 turns on the switch element 4a. Thereafter, since the switching elements 4a and 4b are turned on, the equivalent resistances of the charging paths of the two storage battery modules become equal, and the charging current flows shunting to the two switching elements, so that the loss of both diodes can be reduced.

Japanese Patent Application Laid-Open No. 10-174284 of Invention Example 2 of the prior application
The publication discloses a circuit for switching two sets of capacitor banks connected in parallel from parallel to series. FIG. 9 shows the main configuration of the circuit of the present invention.

In FIG. 9 showing Invention Example 2 of the prior application, 7a,
7b is a diode bank, 8a and 8b are capacitor banks in which a plurality of electric double layer capacitors and the like are connected in series and parallel. Capacitor banks, from the perspective of storing power,
It is considered equivalent to a battery module. This circuit compares the voltage of the capacitor bank 8a with the reference voltage source 11 and turns off the switch element 10 until the voltage of the capacitor banks 8a and 8b drops to half the full charge.
When the output voltage becomes equal to or less than / 2, the series-parallel switching circuit 9 controls the switch element 10 to be turned on and the capacitor banks 8a and 8b to be in series. That is, this circuit is a circuit invented so that when the discharge of the capacitor bank advances, the two capacitor banks are switched from parallel to series to suppress the width of the voltage fluctuation value of the outputs 12a and 12b of the capacitor bank. is there.

[0012]

However, the circuits shown in FIGS. 7 and 8 showing the prior art are circuits suitable for uniformly charging storage battery modules connected in parallel, but discharging the storage battery modules. At this time, there is no technical idea of performing connection for connecting the storage battery modules in series. Therefore, even if the switching element is connected in parallel with the diode and the circuit is changed so as to create a path for the discharge current, the voltage of the storage battery module is supplied to the output terminal as it is at the time of discharge. However, there is a problem that a voltage higher than that of the storage battery module cannot be supplied to the load connected to the output terminal.

FIG. 9 shows a circuit configuration in which a capacitor bank (equivalent to a storage battery module) connected in parallel is connected in series when the capacitor bank is discharged. About twice the voltage of the capacitor bank can be supplied to the output terminal. However, when charging the capacitor banks 8a and 8b connected in parallel, there is a problem that the charging current is not supplied to both capacitor banks because the diodes 7a and 7b are reverse-biased.

The electromotive force of a single cell of a storage battery is as low as about 2 V for a lead storage battery, about 1.2 V for a nickel-cadmium battery or a nickel-metal hydride battery, and about 3 to 4 V for a lithium ion battery. For this reason, one or more of these single cells connected in series are often packed and used as a storage battery module (assembled battery). When a higher voltage is required, the storage battery modules are connected in series. However, there is a problem that the voltage of the storage battery modules varies when the storage battery modules connected in series are charged.

The present invention is suitable for use in a charging device in which storage battery modules are connected in series, and in particular, a power storage device in which the charging voltages of two sets of storage battery modules are equalized by a single charger, and a control method thereof. The purpose is to provide.

[0016]

In order to achieve the above object, a power storage device according to the first aspect of the present invention has a structure in which two storage battery modules and a predetermined charger are connected between positive and negative output terminals. A first diode in which the positive electrode and the anode of the first of the two storage battery modules are connected in series between the positive and negative output terminals,
A second diode in which the negative electrode and the cathode of the second storage battery module are connected in series, and a first switch element and a second switch element connected in parallel with the first diode and the second diode, respectively. A third switch element connected between the anode of the first diode and the cathode of the second diode, and by turning on / off the first switch element and the second switch element,
The charging of the first storage battery module and the charging of the second storage battery module are performed independently of each other.

Further, when the third switch element is turned on / off,
By the OFF control, between the positive and negative output terminals, output the first storage battery module and the second storage battery module connected in series, the first switch element, the second switch element, each of the third switch element An on / off signal generation circuit for a switch element for controlling on / off operation, wherein the first storage battery module and the second storage battery module are intermittently charged to alternately charge the first storage battery module and the first storage battery module; And a voltage detecting means connected in parallel to the second storage battery module and a comparing / judging means for comparing and judging the voltage value detected by the voltage detecting means. According to the result of
The charging priority of the first storage battery module and the second storage battery module is determined.

According to a sixth aspect of the present invention, there is provided a method for controlling a power storage device, wherein two storage battery modules and a predetermined charger are connected between positive and negative output terminals. In the meantime, the positive electrode of the first storage battery module and the anode of the first diode are connected in series, and the negative electrode of the second storage battery module and the cathode of the second diode are connected in series, and the first diode and the second diode are connected in series. A first storage battery module in which each of the two diodes is connected in parallel with the first switch element and the second switch element, and a third switch element is connected between an anode of the first diode and a cathode of the second diode. And the second storage battery module are connected in series to output the total voltage of the two storage battery modules between the positive and negative output terminals,
ON / OFF of the first switch element and the second switch element
When turned off, the first storage battery module and the second storage battery module are charged independently of each other.

The first storage battery module and the second storage battery module may be charged intermittently by charging them alternately.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a power storage device and a control method thereof according to the present invention will be described in detail with reference to the accompanying drawings. FIGS. 1 to 6 show an embodiment of a power storage device and a control method thereof according to the present invention.

(First Embodiment) An embodiment of the present invention will be described below with reference to the drawings. First, FIGS. 1 to 4
Shows a power storage device as a -th embodiment of the present invention. The power storage device 18 of the first embodiment includes the charger 2
And output terminals 17a and 17b of the power storage device.

Power storage device 18 is connected to output terminal 17 of charger 2.
It is configured in an “H” shape between a and 17b. One side of this H shape is configured by connecting the first switch element 14a in parallel with the first diode 13a, and connecting the anode of the first diode 13a to the positive electrode of the first storage battery module 16a. . The other side of the H shape connects the second switch element 14b in parallel with the second diode 13b,
The cathode of the second diode 13b is connected to the negative electrode of the second storage battery module 16b.

The connection side connecting the left and right sides of the H-shape is formed by the anode of the first diode 13a and the second diode 13a.
The third switch element 15 is connected between the cathodes b.

The first diode 1 corresponding to the upper side
The cathode of 3a and the positive electrode of the second storage battery module 16b are connected, and the anode of the second diode 13b corresponding to the lower side and the negative electrode of the first storage battery module 16a are connected. Further, the charger 2 is connected to the cathode of the first diode 13a and the negative electrode of the first storage battery module 16a, and the positive electrode of the second storage battery module 16b is connected to the discharge terminal 1
7a, and the anode of the second diode 13b is connected to the discharge terminal 17b. The on / off control of each switch element is driven by an on / off signal generation circuit 19.

First switch element 14 in this circuit
a, the second switch element 14b and the third switch element 15 perform the on / off operation shown in FIG. When the third switch element 15 is turned on immediately after the on signals of the first switch element 14a and the second switch element 14b are switched to the off signal, for example, the first storage battery module 16a turns on the first switch element 14a. And the third switch element 15 may be short-circuited by a low impedance path. Therefore, it is desirable to provide a dead time.

Each of the storage battery modules 16a, 16b
Is charged by a pulse current, an on / off signal is repeatedly given to the first switch element 14a and the second switch element 14b during the charging operation as shown in FIG. In this case, each switch element is turned on and off such that the second switch element 14b is turned on during the off period of the first switch element 14a and the second switch element 14b is turned off during the on period of the first switch element 14a. Off-phase control. Thereby, the peak value of the charging current supplied from the charger 2 can be reduced. The charging by the pulse current is particularly effective in trickle charging for supplementing the self-discharge capacity of the storage battery modules 16a and 16b.

The switch elements 14a, 14b, and 15 shown in the first embodiment of FIG. 1 are required to have low resistance in the ON state, and therefore, use of a power MOS-FET can be considered. In this case, it is necessary to connect the switch element in consideration of the polarity of the built-in diode parasitically existing between the drain and the source of the power MOS-FET.

FIG. 4 shows an example of an n-channel MOS
-An example of connection when an FET is used as a switch element is shown. In the figure, symbols S1 to S3 indicate the source of each MOS-FET, symbols G1 to G3 indicate the gate of each MOS-FET, and symbols D1 to D3 indicate the drain of each MOS-FET.

The built-in diodes (20a to 20c) are present in an equivalent circuit direction in which the source is the anode and the drain is the cathode. MO equivalent to the third switch element
The connection direction of the S-FET is important. If the symbols D3 and S3 are connected in reverse, the storage battery module is short-circuited when the MOS-FET 21a or 21b is turned on.
The drain of the FET 21c needs to be connected to the anode of the first diode 13a, and the source of the MOS-FET 21c needs to be connected to the cathode of the second diode 13b.

In the first embodiment of FIG. 1, when two sets of storage battery modules 16a and 16b are connected in series and discharged, if the voltage of each storage battery module varies, then the first switch element 21a And the second switch element 21b is turned on to turn on the storage battery modules 16a, 16b.
When charging the battery, a large current may flow from the storage battery module having a high terminal voltage to the storage battery module having a low terminal voltage. The storage battery modules 16a, 16b
Is discharged, the voltages of the two storage battery modules are added, so that the voltage becomes higher than the voltage of the charger 2, and there is a possibility that a reverse current flows from the storage battery module to the charger 2. Further, at the time of charging, the voltage of the charger 2 is applied to the output terminals 17a and 17b of the power storage device.
There is a possibility that a low voltage is supplied to the load connected to the output terminals 17a and 17b.

(Second Embodiment) In order to avoid these effects, voltage measuring means for two sets of storage battery modules 16a and 16b are provided, and the switch element of the storage battery module having a low detection value is turned on first to charge. Then, when the voltages of the two storage battery modules 16a and 16b become substantially equal, the remaining switch elements are turned on. In addition, a backflow prevention unit that flows out of the storage battery module to the charger and a discharge terminal are shut off when the storage battery module is charged.

An invention based on the above technical idea is shown in FIG. 5 as a second embodiment. Fourth switch element 2
2 indicates that the first switch element 14a and the second switch element 14b are turned on and the respective storage battery modules 16a, 1
6b is turned on while charging the third switch element 1
When 5 is turned on, it operates to shift to the off state.

When performing pulse charging, the fourth switch element 22 may repeat the on / off operation in synchronization with the first switch element 14a or the second switch element 14b. It is desirable to control the ON / OFF signal generation circuit 19 of the switch element so as to always supply the ON signal. Although not shown in FIG. 5, the end of charging is detected by detecting the V of the storage battery modules 16a and 16b.
(Terminal voltage), -ΔV, T (temperature), ΔT, and a timer, and then supplementary charge or trickle charge is performed. Here, the end of charge, supplementary charge, and trickle charge are performed. The sum of the periods is referred to as a charging period.

The first switch element 14a and the second switch element 14b are turned off, and the third switch element 15a is turned off.
The ON / OFF signal generation circuit 19 of the switch element supplies the ON signal to the fifth switch element 23 at the same time. By this operation, the two storage battery modules 16 are connected to the output terminals 17a and 17b of the power storage device 2.
a and 16b are supplied. The terminal voltage of the storage battery module during discharge is detected by the voltage detection circuit 24a or 24b, and when the comparison / judgment circuit 25 detects that either of the storage battery modules has reached the discharge end voltage, the on / off signal of the switch element is generated. The circuit 19 sends an off signal to the fifth switch element 23. This allows
It prevents each storage battery module 16a, 16b from being over-discharged.

Next, when charging the discharged storage battery modules, the voltages detected by the voltage detection circuits 24a and 24b of the storage battery modules 16a and 16b are compared and compared.
Processing is performed by the determination circuit 25. For example, the terminal voltage of the first storage battery module 16a> the second storage battery module 16b
In this case, if there is a period during which the first switch element 14a and the second switch element 14b are simultaneously turned on, the first storage battery module 16a
6b may supply a large current. To avoid this, the switch element connected in series with the low-voltage storage battery module is operated first to charge the low-voltage storage battery module, and the two storage battery modules 16a,
When the voltages at 16b become substantially equal, the remaining switch elements are operated. With this configuration, it is possible to prevent an excessive current flowing from the storage battery module having a high terminal voltage to the storage battery module having a low terminal voltage.

In both the first and second embodiments described above, the first switch element 14a
Or, during the ON operation of the second switch element 14b, it should be absolutely avoided that the third switch element 15 is turned on, and even if the first switch element 14a and the second switch element 14b are turned on at the same time. Although it is good, it is to be avoided that the first switch element 14a to the second switch element 14b and the third switch element 15 are simultaneously turned on, and the first switch element 14a to the second switch element 14b
, It is necessary to provide a dead time and operate the third switch element 15 to turn on.

Further, in the sense of double confirmation, [(third switch element is ON) ∩ (first switch element is OFF)]
By providing a logic circuit for confirming {[(third switch element is on)} (second switch element is off)], it is possible to prevent the worst state of short circuit of the storage battery module from continuing.

(Modifications / Applications) FIG. 6 shows a modification / application of the first embodiment and the second embodiment.
The power storage devices of the first embodiment and the second embodiment can be connected in series, and this series connection is effective when outputting a high voltage. FIG. 6 illustrates an example in which the power storage devices of the first embodiment are connected in two stages in series.

(Effects and Effects of Each Embodiment) According to the above embodiment, the first switch element is turned on when charging the first storage battery module and the second storage battery module is charged when charging the second storage battery module. By turning on the second switch element, the charging current from the charger is supplied to each storage battery module. The first and second switch elements may be kept on during the charging period. However, when each storage battery module is charged by a pulse current, the first and second switch elements may be repeatedly turned on and off. .

At the time of discharging, by turning off the first switch element and the second switch element and turning on the third switch element, the first storage battery module and the second storage battery module are connected in series, and the output terminal Is supplied with the total voltage of both battery modules. Further, in the power storage device, a voltage measuring unit of the two storage battery modules, a state control unit of the first switch element or the second switch element based on a detection value of the voltage measuring unit, and a signal from the storage battery module to the charger. Means for preventing backflow from flowing out and means for shutting off the discharge terminal when charging the storage battery module are provided to prevent a low voltage during charging from being supplied to the output terminal and an excessive current flowing due to a difference in terminal voltage between both battery modules. At the same time, the current is prevented from flowing back into the charger due to the high voltage during the discharging.

Further, in the above power storage device, when the first switch element and the second switch element are conductive, the third switch element is turned off, and the first switch element and the second switch element are connected. When the switch element is in a non-conductive state, a control signal is sent to each switch element so as to make the third switch element conductive, and the storage battery module is connected to the first or second switch element and the third switch. A short circuit is prevented by the simultaneous conduction of the elements.

As a result, when the first switch element, the second switch element, and the third switch element are all off, even if there is a difference between the voltages of the first storage battery module and the second storage battery module. Since the first diode and the second diode prevent an excessive current flowing between the two battery modules, there is no possibility that the battery module is deteriorated by this. Further, the voltage of the storage battery module is detected during charging, and a switch element connected in series with the voltage module having a low terminal voltage is configured to be turned on first, and when the terminal voltages are charged substantially equally, the other switch is turned on. By configuring the elements to be turned on, it is possible to prevent an excessive current flowing through both storage battery modules.

After the storage battery module is fully charged, each switch element can be turned on / off at an appropriate time ratio to trickle charge each storage battery module with an equal voltage.

Further, by turning on the third switch element after turning off the first switch element and the second switch element, the first storage battery module and the second storage battery module are connected in series. Can output about twice the voltage value of each storage battery module.

When the third switch element is turned on during a transition period during which the first switch element or the second switch element is on or off, a short circuit of the storage battery module is formed by the switch elements. Therefore, the third switch element is turned on with a dead time after the first and second switch elements are turned off, so that a short-circuit current does not flow.

[0046]

As is apparent from the above description, the power storage device and the control method thereof according to the present invention provide a power storage device and a control method therefor between the positive and negative output terminals, the positive electrode of the first of the two storage battery modules and the anode of the first diode. Are connected in series, the negative electrode of the second storage battery module and the cathode of the second diode are connected in series, each of the first diode and the second diode, and the first switch element and the second switch element. Are connected in parallel, a third switch element is connected between the anode of the first diode and the cathode of the second diode, and the first switch element and the second switch element The charging of the storage battery module and the charging of the second storage battery module are performed independently of each other.

Therefore, even if there is a difference between the voltages of the first storage battery module and the second storage battery module, independent charging is performed, and an excessive current flowing between the two storage battery modules through a low impedance path is prevented. .
For this reason, promotion of deterioration of the storage battery module is prevented.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a main part of a configuration of a power storage device as a first embodiment of a power storage device and a control method thereof according to the present invention.

FIG. 2 is a first diagram illustrating a timing of providing an operation signal to a switch element according to the first embodiment.

FIG. 3 is a second diagram showing the timing of providing an operation signal to the switch element of the first embodiment.

FIG. 4 is a specific connection diagram in which an n-channel MOS-FET is applied to the first embodiment.

FIG. 5 is a circuit diagram showing a main configuration of a power storage device as a second embodiment of the present invention.

FIG. 6 is a circuit diagram showing a connection method when power storage devices of the present invention are connected in series.

FIG. 7 is a circuit diagram showing a conventional parallel charging circuit.

FIG. 8 is a circuit diagram of a conventional parallel charging circuit with reduced loss.

FIG. 9 shows a conventional series-parallel switching circuit of a capacitor bank (corresponding to a storage battery module).

[Explanation of symbols]

1a, 1b Storage battery module 2 Charger 3a, 3b Diode 4a, 4b Switch element 5 Reverse bias voltage detection circuit 6a, 6b Charge control circuit 7a, 7b Diode 8a, 8b Capacitor bank 9 Series / parallel switching circuit 10 Switch element 11 Reference voltage source 12a, 12b Output terminals of capacitor bank 13a, 13b First diode and second diode 14a, 14b First switch element and second switch element 15 Third switch element 16a, 16b First storage battery module and Second storage battery module 17a, 17b Output terminal of power storage device 18 Power storage device 19 On / off signal generation circuit of switch element 20a, 20b, 20c Built-in diodes 21a, 21b, 21c n-channel MOS-FET 22 Fourth switch element 2 The fifth switch element 24a, 24b voltage detection circuit 25 compares and determines circuit

Claims (7)

[Claims] 1. A power storage device configured to have two storage battery modules and a predetermined charger connected between positive and negative output terminals to perform charging and discharging, and between the positive and negative output terminals, a first of the two. A first diode in which the positive electrode and the anode of the storage battery module are connected in series, and a second diode in which the negative electrode and the cathode of the second storage battery module are connected in series, the first diode and the second A first switch element and a second switch element connected in parallel with each of the diodes; and a third switch element connected between an anode of the first diode and a cathode of the second diode. By turning on / off the first switch element and the second switch element, the first storage battery module and the second storage battery module Photoelectrically, power storage device and executes independently of each other. 2. An output in which the first storage battery module and the second storage battery module are connected in series between the positive and negative output terminals by on / off control of the third switch element. The power storage device according to claim 1. 3. An on / off signal generation circuit for a switch element for controlling on / off operation of each of the first switch element, the second switch element, and the third switch element. The power storage device according to claim 1, wherein: 4. The power storage device according to claim 1, wherein the charging of the first storage battery module and the charging of the second storage battery module are intermittent charging in which the charging is performed alternately. . 5. A voltage detection means connected in parallel to the first storage battery module and the second storage battery module, and a comparison / judgment means for comparing / determining a voltage value detected by the voltage detection means. 5. The battery pack according to claim 1, further comprising: determining a charging priority of the first storage battery module and the second storage battery module based on a result of the comparison and determination by the comparison and determination unit. 6. The power storage device according to claim 1. 6. A method for controlling a power storage device comprising two storage battery modules and a predetermined charger connected between positive and negative output terminals, wherein a positive electrode of a first storage battery module is connected between the positive and negative output terminals. The anode of the first diode is connected in series, and the negative electrode of the second storage battery module and the cathode of the second diode are connected in series, and each of the first diode and the second diode is connected to the first diode. A switch element and a second switch element are connected in parallel; a third switch element is connected between an anode of the first diode and a cathode of the second diode; the first storage battery module and the second storage battery Connecting the modules in series to output a total voltage of the two storage battery modules between the positive and negative output terminals; The on / off of pre said second switching element, said first to one charge independently of one another execution of the storage battery module and the second accumulator module, a control method of a power storage device, characterized in that. 7. The control method for a power storage device according to claim 6, wherein the first storage battery module and the second storage battery module are charged intermittently by charging them alternately.