KR20030039735A - Method and system for equability of voltage in electric energy storage system and circuit element for equability of voltage - Google Patents

Abstract

PURPOSE: A voltage equalizing method and a voltage equalizing apparatus and a unit element for voltage equalization are provided to maintain the voltage being applied to each cell constant, while allowing for ease of construction of the serial module electrical energy storage device. CONSTITUTION: A voltage equalizing method comprises the first step of detecting a reference voltage obtained by averaging voltages of cells(30) in a serial module electrical energy storage device(31); the second step of comparing the reference voltage detected in the first step with the voltages applied to both ends of each cell; and the third step of selectively discharging cells in such a manner that the difference between the reference voltage and the voltages applied to both ends of each cell is maintained in a predetermined range.

Description

Method and system for equability of voltage in electric energy storage system and circuit element for equability of voltage

The present invention relates to a method for equalizing a voltage in an electrical energy storage device and an apparatus for performing the same, and more particularly, to a method for equalizing a voltage applied to each cell in an electrical energy storage device in which each cell is connected in series, and to perform the same. It relates to a device for.

As a clean energy source in automobiles and the like recently, electric energy storage devices such as batteries, electric double layer capacitors, or electrochemical capacitors are widely used. However, since the battery, the electric double layer capacitor, or the electrochemical capacitor may have difficulty in increasing the voltage or power capacity per one, a plurality of cells, the electric double layer capacitor, or the electrochemical capacitor may be connected in series. It is used as an electric energy storage device (hereinafter, a series module electric energy storage device) to raise the operating voltage. In this case, one battery or capacitor connected in series in the series module electric energy storage device is called a unit cell, and the unit cell is configured such that an initial electric energy storage capacity is the same.

However, the serial module electric energy storage device maintains a charged state or charges when charged by capacity deviation, leakage current variation, self discharge variation, resistance variation, temperature variation, etc., capable of storing electrical energy in each unit cell. At this time, the voltage of each cell becomes uneven. In particular, when the voltage of each cell is out of an appropriate range, the life of the cell is shortened or the cell is destroyed, thereby reducing the reliability of the electrical energy storage device.

In order to solve the above problems, the operating voltage in each cell is used below the rated voltage. However, the above method has an effect of preventing damage to the cell due to overvoltage at the beginning of use, but does not fundamentally solve the unevenness of voltage generated in each cell during operation.

As another method, as shown in FIG. 1, one voltage comparison element 12 is connected to each cell 10 in parallel at both ends of each cell 10 included in the series module electric energy storage device. Both ends of each cell 10 are provided with one breathing resistor 14 for each cell 10 in parallel. A switch 16 is connected to the breathing resistor 14 in series to short-circuit or open the breathing resistor 14 with both ends of the cells according to a signal input from the voltage comparing element 12. Equipped. Therefore, when the voltage in each cell exceeds the set voltage, the switch 16 is turned on to discharge the cell through the breathing resistor 14, so that the voltage range of each cell 10 can be properly maintained.

However, when the above method is used, the voltage nonuniformity generated within the set voltage cannot be solved. If the rated voltage in each of the cells 10 decreases compared to the initial state, and the set voltage is higher than the rated voltage, the discharge of the cell 10 starts when the cell is already overvoltage applied. do. As a result, the variation in the performance degradation rate in each cell 10 may occur due to the voltage non-uniformity, which may result in a reduction in the life of the energy storage device.

In addition, as a method for reducing the voltage deviation caused by the self-discharge deviation or leakage current deviation in the cell when the state of charge of the series module electrical energy storage device is maintained for a long time or connected to an external power source, As described above, the resistors 22 are connected in parallel between the anode and the cathode of each cell 20. Thus, leakage current or self discharge in each of the cells 20 is increased to compensate for the voltage deviation. However, since the method does not selectively discharge only the cell 20 to which the overvoltage is applied, it does not solve the voltage nonuniformity of the cell 20 due to the capacity variation or the voltage variation before charge start.

It is therefore a first object of the present invention to provide a method for maintaining a uniform voltage applied to each cell in a series module electrical energy storage device.

It is a second object of the present invention to provide an apparatus for maintaining a uniform voltage applied to each cell in a series module electrical energy storage device.

It is a third object of the present invention to provide a unit element that can be mounted in each cell in order to maintain a uniform voltage applied to each cell of the series module electrical energy storage device.

1 is a block diagram showing an example of a device for voltage equalization in a conventional electrical energy storage device.

2 is a block diagram showing an example of a device for voltage equalization in a conventional electrical energy storage device.

3 is a block diagram of a voltage equalization device that can be used in the series module electrical energy storage device according to the first embodiment of the present invention.

4 is a configuration diagram of a voltage equalization device that can be used in the series module electrical energy storage device according to the second embodiment of the present invention.

5A to 5B are diagrams for explaining the operation of the voltage equalizer in a given cell.

FIG. 6 is a block diagram illustrating a voltage equalization unit device mounted in each cell of an electrical energy storage device according to an embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

30 cell 31 serial module electrical energy storage device

32: voltage dividing line 32a: resistance

34: voltage comparison element 36: discharge line

36a: breathing resistor 36b: switch

In order to achieve the first object, the present invention, in the electrical energy storage device in which a plurality of cells having the same initial electrical energy storage capacity is connected in series, detecting a reference voltage for each cell, the reference voltage and each cell Comparing the voltages applied across both ends of the cell, and selectively discharging each cell so that a voltage difference between the reference voltage and the voltages applied across the cells is maintained within a predetermined range. Provides a method of voltage equalization of a device.

In order to achieve the second object, the present invention provides an electric energy storage device in which a plurality of cells having the same initial electric energy storage capacity are connected in series. A voltage comparator for comparing the applied reference voltage with voltages applied to both ends of each cell, and selectively discharging each cell so that the voltage difference between the reference voltage and the voltage applied at both ends of each cell is maintained within a predetermined range. Provided is a voltage equalization device of an electrical energy storage device having a discharge unit.

In order to achieve the third object, the present invention provides a voltage comparator for connecting a resistor having a predetermined resistance value, both ends of the resistor, and a voltage comparator connected to the voltage comparator, and comparing the voltages at both ends of the resistor. Two first connection lines for connecting to both ends of the object, a second connection line branched on the two first connection lines to connect the first connection lines, and a discharge line on the second connection line. Provided is a voltage equalization unit device mounted to each cell of the serial module electrical energy storage device having a.

When the voltage equalization method and apparatus are used, the reference voltage for voltage equalization is detected by the electric energy storage device itself, so that the voltage of each cell is uniformly maintained in the entire operating voltage region. In addition, the voltage equalizing unit elements may be attached to each cell of the series module energy storage device to maintain the voltage of the cell uniformly regardless of the number of cells included in the energy storage device.

Therefore, by using the voltage equalization method, apparatus, and unit device, the reliability of the series module electric energy storage device can be improved, and further, the reduction of the electric energy storage amount can be prevented.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a block diagram of a voltage equalization device that can be used in the series module electrical energy storage device according to the first embodiment of the present invention.

Referring to FIG. 3, there is provided a series module electrical energy storage device 31 formed by serially connecting an electrical energy storage device such as a cell, an electrical double layer capacitor, or an electrochemical capacitor. In the present embodiment, a series module electric energy storage device 31 formed by connecting cells in series will be described. In the series module electric energy storage device 31, one battery connected in series is called a unit cell 30, and the unit cells 30 are configured to have the same initial electric energy storage capacity.

A voltage dividing line 32 is connected to the anode and the cathode of the input and output terminals of the energy storage device 31 of the series module, and divides the voltages at both ends of each cell for each cell. The voltage dividing line 32 detects a reference voltage as a reference for determining whether an overvoltage is applied to each cell of the energy storage device of the series module. The reference voltage detected by the voltage dividing line 32 is an average voltage for each cell, which is a value obtained by dividing the voltage applied to the voltage dividing line by the number N of the cells 30 provided in the voltage dividing line. Specifically, the voltage dividing line 32 is composed of a line connecting the resistors 32a having the same resistance value in series by the number N of the cells 30. The reference voltage is a voltage applied to one resistor in the voltage dividing line 32.

A voltage comparison unit for comparing the reference voltage and the voltage applied to both ends of each cell 30 is provided. The voltage comparison unit has a configuration in which voltage comparison elements 34 provided in the same number as the number of cells are connected to both the cell 30 and the resistor 32a of the divided line 32. Referring to one cell 30, the one voltage comparison element 34 is connected to both ends of the one cell 30. In addition, both ends of any one resistor 32a and the one voltage comparator 34 are connected to each of the divided lines 32. Accordingly, the voltage comparing element compares the voltage applied across the cell 30 with the voltage applied across the resistor 32a of the divided line 32.

A discharge unit for selectively discharging each cell 30 is provided such that a voltage difference between the reference voltage and the voltage applied to both ends of each cell 30 is maintained within a predetermined range. The discharge unit has a configuration in which discharge lines 36 are connected to both ends of each cell in parallel. Therefore, the discharge lines 36 are connected in parallel to both ends of the cells 30, respectively, and provided as many as the number of cells 30.

Specifically, the discharge line is connected to the breathing resistor 36a and the switch in series. The switch is connected to the voltage comparing element 34 and turned on / off according to a signal input from the voltage comparing element 34. The switch 36b short-circuits or opens the breathing resistor 36a according to a signal input from the voltage comparing element 34, and is connected to the breathing resistor 36a when the breathing resistor 36a is short-circuited. Discharge is performed at both ends of the cell 30.

At this time, the discharge line 36 is branched in a line connecting both ends of the one cell 30 and the voltage comparison element 34, as shown, to be connected in parallel at both ends of each of the cells 30 Can be.

4 is a configuration diagram of a voltage equalization device that can be used in the series module electrical energy storage device according to the second embodiment of the present invention.

In FIG. 4, only the connection of the voltage divider line in the voltage equalization device described with reference to FIG. 3 is different. Other elements are the same, and the same elements use the same reference numerals.

Referring to FIG. 4, in the energy storage device 31 of the serial module, the cells 30 connected in series are divided to designate unit cells 30a, 30b, and 30c, and the plurality of unit cells 30a, 30b, Connect the divided lines L1, L2 and L3 to both ends of 30c). Accordingly, the energy storage device 31 has the same number of divided lines L1, L2, and L3 as the number of the unit cells 30a, 30b, and 30c. The divided lines L1, L2, and L3 detect a reference voltage as a reference for determining whether overvoltage is applied to each of the cells provided in the divided lines L1, L2, and L3. The reference voltage is a value obtained by dividing the voltage applied to each of the divided lines L1, L2, and L3 by the number of cells 30 provided in the divided lines L1, L2, and L3, respectively. The reference voltages detected in lines L1, L2, and L3 may have the same value or may have different values.

In detail, each of the divided lines L1, L2, and L3 includes a resistor 32a having the same resistance value, and the number N1 of the cells 30 provided in the divided lines L1, L2, and L3. , N2 and N3). In each of the divided lines L1, L2, and L3, voltages applied across both resistors become reference voltages. The divided voltage lines L1, L2, and L3 may be useful when the number of cells connected in series to the energy storage device is large.

A voltage comparison unit for comparing the reference voltage and the voltage applied to both ends of each cell is provided. Specifically, the voltage comparison unit compares the voltage applied to both ends of one resistor in a predetermined divided line and the voltage applied to both ends of one cell 30 provided in the energy storage device 31, respectively. The discharge unit for selectively discharging each of the cells 30 so that the voltage difference between the reference voltage and the voltage applied to both ends of each cell 30 is maintained within a predetermined range at the voltage compared from the voltage comparing unit. It is provided. Since the configuration of the voltage comparator and the discharge unit is the same as that of the first embodiment, description thereof is omitted.

Hereinafter, a method of operating the voltage equalization device that can be used in the series module electric energy storage device described with reference to FIGS. 3 to 4 to uniform the voltage of each cell will be described in detail.

A series module electric energy storage device 31 is formed by connecting cells having the same initial electric energy storage capacity in series. The energy storage device 31 detects a reference voltage for each cell 30. The reference voltage is detected by dividing the output voltage of the electrical energy storage device 31 for each cell 30, or the partial output voltage output for each predetermined portion of the electrical energy storage device 31 for each cell. It can be detected by partial pressure.

In FIG. 3, a voltage dividing line 32 for dividing the output voltage of the electric energy storage device 31 for each cell 30 is provided. In FIG. 4, a predetermined portion of the electric energy storage device 31 is provided. The divided lines L1, L2, and L3 are provided for dividing the partial output voltage output by the respective cells.

First, a method of detecting a reference voltage will be described with reference to FIG. 3. The voltage dividing line 32 is connected to the positive electrode and the negative electrode of the input / output terminal of the electrical energy storage device 31 of the series module, and the voltage dividing line 32 includes the number N of cells 30 included in the energy device. As many resistors 32a as N are connected. If the output voltages output from the positive and negative terminals of the input and output terminals of the energy storage device 31 are V, then the voltage applied across the resistor 32a connected in series to the voltage dividing line 32 is The output voltage V / number of resistances N is obtained. The voltage V / N applied across the one resistor 32a is detected as a reference voltage corresponding to each cell.

Alternatively, a method of detecting the reference voltage will be described with reference to FIG. 4. In the electric energy storage device 31 of the series module, the cells connected in series are divided to designate a plurality of unit cells 30a, 30b, and 30c including a plurality of series connected cells. Cells connected to both ends of the plurality of unit cells 30a, 30b, and 30c, respectively, are provided in the unit cells 30a, 30b, and 30c with voltages applied to the unit cells 30a, 30b, and 30c. The partial pressure lines L1, L2, and L3 for partial pressure separation are provided. Hereinafter, an example will be described in which one electrical energy storage device 31 includes first to third voltage dividing lines L1, L2, and L3.

The first to third voltage dividing lines L1, L2, and L3 have the same resistance value as the number of cells N1, N2, and N3 provided in the respective voltage dividing lines L1, L2, and L3. The resistor 32a is connected. When the voltages applied to both ends of the first to third voltage dividing lines L1, L2, and L3 are V1, V2, and V3, respectively, the voltages applied to both ends of one resistor connected in series to the first voltage dividing line are V1 / N1, the voltage applied across one resistor connected in series with the second voltage divider line is V2 / N2, and V3 / N3 in the third voltage divider line. In this case, V1 / N1, V2 / N2, and V3 / N3, which are voltages applied across one resistor in the first to third voltage dividing lines, are respectively reference voltages for one cell.

If there is no voltage deviation between the cells 30 included in the energy storage device 31, the values of the reference voltages obtained by the two methods described above are the same. In addition, the voltage applied to one cell 30 in the energy storage device 31 is equal to the reference voltage.

However, the result can be expected assuming that there is no voltage deviation of each of the cells 30 provided in the energy storage device, and in fact, one of the divided lines is provided because of the voltage deviation of each of the cells 30. The reference voltage applied across the resistor and the voltage applied to any one cell in the divided line are not equal.

Then, when the voltage applied across the resistor in the divided line and the voltage applied to the predetermined cell provided in the divided line are not the same, the operation of the voltage equalizer in the predetermined cell is shown in FIG. 5A. It demonstrates with reference to FIG. 5B.

The voltage applied across the resistor 52a provided in the voltage dividing line 52 and the voltage applied to the predetermined cell 52 provided in the voltage dividing line 52 may cause the voltage comparison element 34 to operate. Use it to compare. In addition, the switch 56b may be used only when the difference between the voltage applied to the cell 50 and the voltage applied across the one resistor 52a constituting the divided line 52 is higher than the set value through the comparison. 5B. When the switch 56b is ON, the breathing resistor 56a is shorted and the cell 50 is discharged through the breathing resistor 56a. The voltage applied to 50 becomes low. At this time, if the difference between the voltage applied to the cell 50 and the voltage applied across the one resistor 52a is smaller than the set value, the switch 56b is turned off and the breathing resistor 56a is opened. Thus, the discharge of the cell 50 is stopped. (FIG. 5A).

In the above description, one cell 50 has been described as an example, but a series of operations in which the cell 50 is discharged or stopped is simultaneously performed in each of the cells constituting the series module electric energy storage device. Therefore, the voltage applied to each of the cells becomes uniform.

FIG. 6 is a block diagram illustrating a voltage equalization unit device mounted in each cell of an electrical energy storage device according to an embodiment of the present invention.

Referring to FIG. 6, a resistor 100 having a predetermined resistance value is provided. In addition, a voltage comparison element 102 connected to both ends of the resistor 100 is provided. Two connection lines 104 are connected to the voltage comparing element 102 and connected to both ends of the target to be compared with the voltage at both ends of the resistor 102. And a discharge line 106 branched on the two connection lines 104 and connected to the first connection lines 104.

The voltage equalizing unit element 110 having the above-described configuration includes a plurality of cells having the same initial electrical energy storage capacity as the number of cells connected in series in an electrical energy storage device in series. .

In the voltage equalizing unit device, an end of the connection line 104 is connected in parallel to both ends of the series-connected cell in an electrical energy storage device. In addition, the plurality of voltage equalization unit elements 110 are used by connecting the resistors 100 provided in the respective elements in series.

The resistor 100 connected in series may be connected in parallel to the positive electrode and the negative electrode of the input and output terminals of the series module energy storage device.

The discharge line has a configuration in which the breathing resistor 106a and the switch 106b are connected in series. In addition, the switch 106b is connected to the voltage comparing element 106b to open or short the breathing resistor 106a with each of the cells according to a signal input from the voltage comparing element 106b.

By forming the unit device 110 mounted in each cell, by connecting the unit device 110 as many as the number of cells irrespective of the number of cells connected in series to the energy storage device of the series module the energy storage device It is possible to equalize the voltage of cells connected in series at.

If the maximum voltage applied to the series module electrical energy storage device is limited, any voltage below the maximum voltage may be applied to maintain uniform voltages applied to the cells.

The effect that can be expected in the present invention described above,

First, the voltage equalization device is provided for each cell irrespective of the number of cells provided in the series module electric energy storage device, so that the series module electric energy storage device can be easily configured.

Second, since the reference voltage for voltage equalization is detected by the series module electrical energy storage device itself, the voltage at each cell regardless of the voltage applied to the series module electrical energy storage device without having a separate circuit for each voltage region. Can be equalized.

Third, by equalizing the voltage applied to each cell, it is possible to improve the reliability of the series module electrical energy storage device.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

Claims (15)

Detecting a reference voltage which is an average voltage for each cell in an electrical energy storage device having a plurality of cells having the same electrical energy storage capacity connected in series; Comparing the reference voltage with a voltage applied across each cell; And selectively discharging each cell so that the voltage difference between the reference voltage and the voltage applied across the respective cells is maintained within a predetermined range. The method of claim 1, wherein the detecting of the reference voltage is performed by dividing an output voltage of the electrical energy storage device for each cell. The method of claim 1, wherein the detecting of the reference voltage is performed by dividing a partial output voltage output by each part of the electrical energy storage device for each cell. . In an electrical energy storage device in which a plurality of cells having the same electrical energy storage capacity are connected in series, reference voltage detecting means for detecting a reference voltage which is an average voltage for each cell; Voltage comparison means for comparing the detected reference voltage with a voltage applied across each cell; And discharging means for selectively discharging each of the cells such that the voltage difference between the reference voltage and the voltage applied to both ends of each cell is maintained within a predetermined range. 5. The electrical energy according to claim 4, wherein the reference voltage detecting means comprises a circuit in which resistors having the same resistance value are formed in series by the same number as the number of cells connected in series between both ends of the cells connected in series. Voltage equalization device of storage device. 6. The voltage equalization device of claim 5, wherein the reference voltage detection means is connected in parallel to an input and an output terminal of the energy storage device. The electrical energy storage device of claim 5, wherein the reference voltage detecting means is connected in parallel to both ends of the plurality of unit cells formed by dividing the cells connected in series in the energy storage device by a predetermined unit. Voltage equalizer. 5. The voltage comparison device of claim 4, wherein a voltage comparison device is connected to one end of each resistor provided in the voltage divider and one end of each cell, respectively, and the voltage applied to both ends of each resistor. And a voltage equalizing device configured to compare voltages applied across the cell. 5. The voltage equalization device of claim 4, wherein the discharging means has a structure in which discharge lines for discharging the respective cells are connected in parallel to both ends of the respective cells. The method of claim 9, wherein the discharge line, Breathing resistance; And And a switch connected in series with the breathing resistor and connected to the voltage comparing element to open or short the breathing resistor with each of the cells according to a signal input from the voltage comparing element. Voltage equalizer. A resistor having a predetermined resistance value; A voltage comparing element connecting both ends of the resistor; Two connection lines connected to the voltage comparing element and connected to both ends of the target to be compared with the voltage at both ends of the resistor; And And a discharge line branched on the two first connection lines and connected to the first connection lines, respectively. 12. The method of claim 11, wherein the voltage equalization unit device is used in the electrical energy storage device having a plurality of cells having the same electrical energy storage capacity in series with a plurality of the same number as the number of cells connected in series. Voltage equalization unit element mounted on each cell of an electrical energy storage device. The voltage equalization unit device of claim 12, wherein the plurality of voltage equalization unit devices are connected to each other in series with a resistor provided in the device. The voltage equalization unit device of claim 13, wherein the resistors connected in series are connected to both ends of the energy storage device in parallel. The method of claim 11, wherein the discharge line Breathing resistance; And And a switch connected in series with the breathing resistor and connected to the voltage comparing element to open or short the breathing resistor with each of the cells according to a signal input from the voltage comparing element. Voltage equalization unit element mounted in each cell.