WO2015115766A1

WO2015115766A1 - Voltage equalization circuit

Info

Publication number: WO2015115766A1
Application number: PCT/KR2015/000821
Authority: WO
Inventors: 김성민
Original assignee: 킴스테크날리지 주식회사
Priority date: 2014-01-29
Filing date: 2015-01-27
Publication date: 2015-08-06
Also published as: KR20150090436A

Abstract

A voltage equalization circuit is disclosed. This circuit comprises: a series-string configured to include electronic energy storage cells connected in series; a reference voltage generator which generates a voltage equalization reference voltage; a target voltage generator which generates a voltage equalization target voltage, and to which the reference voltage is input; and a voltage controller, to which the target voltage is input, which is connected to the electronic energy storage cell of the series-string, and which equalizes a voltage of the electronic energy storage cell. Herein, the target voltage generator generates the target voltage by adding the reference voltage to a negative terminal voltage of an objective electronic energy storage cell of the series-string or by subtracting the reference voltage from a positive terminal voltage of the objective electronic energy storage cell.

Description

Voltage equalization circuit

The present invention relates to a voltage equalization circuit of an electrical energy storage device, and more particularly, to a voltage equalization circuit for performing voltage equalization between electrical energy storage cells in an electrical energy storage device configured by connecting electrical energy storage cells in series. .

In general, electric energy storage cells such as secondary batteries and capacitors have a rated voltage of only a few volts, but most applications require voltages of tens to hundreds of volts. do. For this reason, recent electric energy storage devices (Electric Energy Storage Device) has been manufactured in a structure in which hundreds of electric energy storage cells are connected in series.

In order for an electrical energy storage cell such as a battery or a capacitor to operate normally, charging and discharging must be performed within an allowable operating voltage range. When the electrical energy storage cell operates in an area outside the permitted operating voltage range, for example, when the battery is operated in an under-voltage or over-voltage state, the life of the electrical energy storage cell is abruptly shortened or There is a risk of an accident such as an explosion or fire.

In order to increase the lifespan and increase the safety of the electric energy storage device, it is necessary to maintain the voltage between the electric energy storage cells evenly at the electric energy storage cell level.

In order to maintain an equal voltage between the electrical energy storage cells connected in series at the dimension of the electrical energy storage cell, the electrical energy storage cells connected in series must have the same characteristics. That is, the make, model, capacity, leakage current, etc. must be the same, and even the same manufacturing date and the same lot number are required. Under these conditions, the electrical energy storage cells having the same characteristics must maintain the same characteristics and the same state of charge during operation in series connection.

However, the electrical energy storage cell is inevitable to some extent, such as a manufacturing capacity deviation. In addition to the characteristic deviation, the characteristic may change depending on environmental factors such as temperature deviation. As such, an electric energy storage device including a plurality of electrical energy storage cells connected in series may have a temperature deviation or an aging deviation between the electric energy storage cells depending on the position of the electric energy storage cells. Although small, the characteristic deviation increases as the usage time of the electrical energy storage device increases. For this reason, it is very difficult to continuously maintain voltage equalization between electrical energy storage cells only by the electrical energy storage cells themselves.

Various devices have been developed for voltage equalization between electrical energy storage cells to solve this problem.

1 is a circuit diagram of a voltage equalizer using a voltage divider and an op amp according to the prior art, which is a circuit diagram disclosed in US Patent No. 5,773,159.

Referring to FIG. 1, the voltage equalization method of the voltage equalizer disclosed in US Patent No. 5,773,159 shows that the input voltage and the output voltage are the same when the op amps (OA ₁ ,... OA _n-1 ) are used as voltage followers. It is used. That is, when the voltage divider is configured by connecting the resistors R ₁ , R ₂ , ..., R _N having the same resistance value in series as the number of series of the electric energy storage cell, the voltage applied across each resistor is averaged. The voltages of the nodes Y ₁ ,..., And Y _n-1 connecting voltages and resistances are integer multiples of the average voltage. The goal of voltage equalization is to equalize the voltage by inputting the node voltage of the voltage divider to the op amp and connecting the op amp output to the nodes of the electrical energy storage cells of the same order since the voltage of each electric energy storage cell is an average value. However, this method works relatively smoothly when the number of serials is small, but it is difficult to operate smoothly when the number of serials increases. For example, if six electrical energy storage cells are connected in series and 12V is applied to both ends, if a resistor divider is composed of six resistors, node 1 is 2V, node 2 is 4V, and node 3 is 6V. , Node 4 voltage is 8V, node 5 voltage is 10V. If the voltage of the first electrical energy storage cell is 2.5V, the voltage of the sixth electrical energy storage cell is 1.5V and the remaining electrical energy storage cells have an average voltage of 2V, the first time of the string in which the electrical energy storage cells are connected in series Node voltage is 2.5V, node 2 is 4.5V, node 3 is 6.5V, node 4 is 8.5V, node 5 is 10.5V. Since the input of OP1 is 2V, which is the voltage of node 1 of voltage divider, the output of OP1 is 2V and the output of OP1 is connected to node 1 of the electrical energy storage cell with voltage of 2.5V. The cell is discharged through op amp 1. On the other hand, in the case of the second op amp, the corresponding input voltage is the node voltage of 4 V, and thus the output voltage of the second op amp is 4 V and the output is connected to the second node of the electric energy storage cell having the node voltage of 4.5 V. Therefore, the second electrical energy storage cell is also discharged through the second op amp. However, since the voltage of the second electrical energy storage cell is an average voltage, the second electrical energy storage cell is a cell that is normally equalized, but there is a problem of discharging the electrical energy storage cell by mistaken for overvoltage. This occurs in the third, fourth and fifth electrical energy storage cells. This is a problem with the method of comparing the node voltage. In other words, since the charging voltage cannot be clearly known only by the node voltage, it is difficult to expect accurate operation. As the number of series increases, the exact operation becomes more difficult.

2 is a circuit diagram of another type of voltage equalization device according to the prior art, which is a circuit diagram disclosed in US Patent No. 7,342,768.

Referring to FIG. 2, the voltage equalization method of the voltage equalizer disclosed in US Pat. No. 7,342,768 uses a voltage divider function of a resistor and a voltage follower of an op amp as shown in FIG. will be. That is, as shown in FIG. 2, the voltage equalizer disclosed in US Pat. No. 7,342,768 consists of a plurality of capacitors 202 coupled to multiple voltage equalization modules 204a-204e. Capacitor 202 may be connected to a power source and / or a load via

connections

205a and 205b. The multiple voltage equalization modules 204a to 204e are designed in a layout structure of overlapping topologies in two series as shown in FIG. 2 to form a cooperative relationship with each other. The conventional voltage equalization device disclosed in the US Patent No. 7,342,768 has no problem in misunderstanding the state of the electrical energy storage cell as shown in FIG. 1 by using two series. However, since voltage equalization has to be propagated sequentially through adjacent cells, when the number of series is large, voltage equalization speed is slow and voltage equalization accuracy is disadvantageous. For example, if 40V is applied to a series string in which ten electrical energy storage cells are connected in series, the average voltage is 4.9V for the first electrical energy storage cell and 3.9V for the remaining nine electrical energy storage cells. There is no voltage equalization operation because the voltages of the two electrical energy storage cells are the same in the other units except the unit in which the electrical energy storage cell having the voltage of 4.0V but the voltage is 4.9V. The voltage equalization is started after the energy of the electric energy storage cell with the voltage of 4.9V is propagated to the adjacent cell so that the voltage difference between the electric energy storage cells of each module is generated. Therefore, the voltage equalization rate is also slow.

As described above, in the conventional voltage equalization method using a voltage divider and an op amp, many modified forms have been developed due to the structural simplicity, but the above-mentioned problems remain.

The problem to be solved by the present invention to solve the above problems is to improve the voltage equalization precision and speed of the voltage equalization circuit and to provide a simple and inexpensive voltage equalization circuit.

In order to solve the above-mentioned problems in an electric energy storage device composed of a series string in which an electric energy storage cell such as a secondary battery or a capacitor is connected in series,

The voltage equalization circuit of the electrical energy storage device according to the present invention includes a series string in which the electrical energy storage cells are connected in series; A reference voltage generator for generating a voltage equalization reference voltage; a target voltage generator for inputting the reference voltage to generate a voltage equalization target voltage; And a voltage controller to which the target voltage is input and connected to the electrical energy storage cell of the series string to equalize the voltage of the electrical energy storage cell, wherein the target voltage generator comprises: a cathode of the target electrical energy storage cell of the series string; The target voltage may be generated by adding the reference voltage to a terminal voltage or by subtracting the reference voltage from a positive terminal voltage of a target electric energy storage cell.

The voltage equalization circuit according to the present invention can be configured at low cost with fast voltage equalization and excellent voltage equalization accuracy with a simple structure.

1 is a circuit diagram illustrating a voltage equalization method according to the related art.

2 is a circuit diagram illustrating another voltage equalization method according to the related art.

3 is a circuit diagram of a voltage equalization circuit according to an embodiment of the present invention.

4 is a circuit diagram of a voltage equalization circuit according to another embodiment of the present invention.

5 is a circuit diagram of a voltage equalization circuit according to another embodiment of the present invention.

6 is a circuit diagram of a voltage equalization circuit according to another embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

FIG. 3 is a circuit diagram of a voltage equalization circuit according to an embodiment of the present invention. In FIG. 3, a circuit diagram in which four electric energy storage cells C1, C2, C3, and C4, such as a secondary battery or an ultracapacitor, is connected in series is illustrated. do. This is merely to simplify the circuit configuration to facilitate the understanding of the description, the present invention is not limited thereto. Accordingly, it is assumed that each of the following target voltage generators and voltage controllers included in the voltage equalization circuit according to the embodiment of the present invention is configured as three.

Referring to FIG. 3, a voltage equalization circuit according to an embodiment of the present invention may include three first to third voltage equalization target voltage generators OP1V, OP2V, and OP3V that generate a voltage equalization target voltage, and the voltage equalization target voltage. Three first to third voltage controllers OP1P, OP2P, and OP3P for performing voltage equalization of the electrical energy storage cells C1, C2, C3, and C4 according to the input of the control circuit.

The reference voltage Vref input to the positive input terminal of each of the voltage equalization target voltage generators OP1V, OP2V, and OP3V is a voltage for voltage equalization operation of each of the electrical energy storage cells C1, C2, C3, and C4. to be. The reference voltage Vref may be an average voltage of the electrical energy storage cells C1, C2, C3, and C4 connected in series. In some cases, the average voltage may be a processed voltage. Here, when the reference voltage (Vref) is the average voltage, the reference voltage (Vref) is a differential dividing the total voltage connected in series by a voltage divider or an electrical energy storage cell in series with a resistor having the same resistance value in series Can be generated using means such as amplifiers. In this embodiment, it is assumed that the average voltage of the electrical energy storage cells (C1, C2, C3, C4) as a reference voltage.

Each of the voltage equalization target voltage generators OP1V, OP2V, and OP3V may be implemented using a summing amplifier using an op amp having a gain of 1. The voltage equalization target voltage is generated by adding the reference voltage Vref to the cathode voltages VC1, VC2, and VC3 of the electrical energy storage cells C1, C2, C3, and C4 that are to be voltage equalized. For example, the first voltage equalization target voltage generator OP1V generates the target voltage VC1 + Vref plus the negative voltage VC1 of the electrical energy storage cell C1 and the reference voltage Vref, and the second voltage equalization target voltage. The generator OP2V generates the target voltage VC2 + Vref plus the cathode voltage VC2 and the reference voltage Vref of the electrical energy storage cell C2. Similarly, the third voltage equalization target voltage generator OP3V generates the target voltage VC3 + Vref. Of course, the voltage equalization target voltage may be generated by subtracting the reference voltage from the anode voltage of the electrical energy storage cells C1, C2, C3, and C4 that are the voltage equalization targets. In this case, a differential amplifier circuit is used.

When the voltage equalization target voltage is generated as described above, voltage equalization may be performed on the node voltage of the series string of the electrical energy storage cells, not the charging voltage of the electrical energy storage cells C1, C2, C3, and C4. Simple voltage controllers (OP1P, OP2P, OP3P) such as op amps can be used for voltage control.

The voltage controllers OP1P, OP2P, and OP3P function as voltage followers of the op amp, and feedback resistors Rf for feeding back the output terminals of the voltage controllers OP1P, OP2P, and OP3P to the negative input terminal. The load resistors RL connected to the outputs of the voltage controllers OP1P, OP2P, and OP3P may be omitted as necessary. In FIG. 3, the feedback configuration of the voltage controllers OP1P, OP2P, and OP3P is connected to the negative input terminal of the voltage controllers OP1P, OP2P, and OP3P. Accordingly, a node formed between the op amp output terminal and the load resistor RL may be connected to the negative input terminal of the voltage controllers OP1P, OP2P, and OP3P.

In the voltage equalization method according to the prior art as shown in FIG. 1, not only the node voltage of the voltage divider which is the voltage equalization target voltage and the state of charge of the target electric energy storage cell, but also the state of charge of all the electric energy storage cells lower than the node voltage. It is difficult to accurately determine the state of charge of the target electric energy storage cell because it operates by comparing the state of charge of the target electric energy storage cell through the accumulated electric energy storage cell serial string node voltage.

In contrast, in the present invention, the reference voltage is added (subtracted in the case of the positive voltage) to the negative electrode (or positive voltage) of the target electric energy storage cell to generate a voltage equalization target voltage to generate the voltage equalization target voltage. It is possible to exclude the influence of the state of charge of the electrical energy storage cell other than the state of charge. By doing so, it is possible to accurately measure the state of charge of the target electrical energy storage cell to achieve accurate voltage equalization through charge or discharge according to the state of charge.

Since the voltage equalization method according to an embodiment of the present invention proceeds simultaneously in the entire electrical energy storage cells connected in series, the voltage equalization is faster than the sequential progress according to the prior art of FIG. 2. Therefore, even if the number of series increases, it is possible to achieve voltage equalization more accurately and quickly than the conventional technique by a simple method.

Meanwhile, the embodiment of FIG. 3 describes an example in which a voltage controller for performing voltage equalization of an electric energy storage cell is implemented as an op amp. In this case, since the current capable of charging and discharging using the op amp may be small, when the capacity of the electrical energy storage cell is large, the voltage equalization speed may be lowered. In addition, when the op amp is used as the target voltage generator OP1V to OP3V and the voltage controller OP1P to OP3P, as shown in FIG. 3, the output voltage of the general op amp is about 1 to 2 V lower than the op amp input power supply voltage. Therefore, it is preferable to use a rail-to-rail type op amp that can increase the output voltage to the op amp input power supply voltage.

Referring to FIG. 4, the voltage equalization circuit according to another embodiment of the present invention configures a current amplifier 40 to be applied to an output terminal of each of the voltage controllers OP1P, OP2P, and OP3P illustrated in FIG. 3. Has a circuit configuration that increases. In FIG. 4, only the current amplifier 40 connected to the output terminal of the third voltage controller OP3P shown in FIG. 3 is shown for simplicity of the drawing. As shown in FIG. 4, the current amplifier 40 has two transistors Q1 and Q2 connected in series between Vcc and ground and the output terminals of the third voltage controller OP3P. It includes two resistors (R1, R2) respectively connected to the input terminal (base terminal) of the. The output node 42 of this current amplifier 40 is connected to the series string node 44 which connects the electrical energy storage cell C3 and the electrical energy storage cell C4 in series. The negative input terminal of the third voltage controller OP3P is connected to the

output node

42 or 44 of the current amplifier 40 to form a feedback line. In this way, by configuring the current amplifier 40 at the output terminal of each of the voltage controllers OP1P, OP2P, and OP3P, it is possible to increase the current that can be applied.

Referring to FIG. 5, the voltage equalization circuit according to another embodiment of the present invention performs voltage equalization by configuring one transistor Tn at an output terminal of the voltage controller OPnP unlike other embodiments of FIG. 4. . Specifically, in another embodiment of the present invention, the output terminal of the voltage controller OPnP is connected to the transistor Tn base, and the emitter of the transistor Tn and the anode terminal of the electrical energy storage cell Cn have a load resistance ( And a feedback line electrically connected by RL, the emitter of transistor Tn being connected to the negative input of the voltage controller OPnP. If the reference voltage Vref, the input of the voltage equalization target voltage generator OPnV, is set as small as dV from the average voltage, a voltage difference equal to dV is generated across the load resistance RL even after voltage equalization and a corresponding current is applied. Flow. If the voltage of the electrical energy storage cell is lower than Vref-dV, the discharge through the voltage controller OPnP is stopped.

Referring back to FIG. 5, as the voltage of the electrical energy storage cell Cn is higher, the voltage difference across the load resistor RL increases and the current increases. The voltage equalization operation is similar to the passive method in which a resistor is connected across the electrical energy storage cell.

By using the point that the discharge current changes according to the voltage, voltage equalization can be performed without charging the electrical energy storage cell. In the voltage equalization circuit as shown in FIG. 3, when the electric energy storage cell Cn is charged by the voltage equalization operation, not only the electric energy storage cell Cn is charged, but all voltages lower than the electric energy storage cell Cn. The electrical energy storage cell is charged. In order to effectively equalize voltage, only a specific electric energy storage cell should be charged or discharged, but this is not simple in the charging operation. On the other hand, the discharge operation is relatively easy to discharge only a specific electric energy storage cell. 5 can perform the voltage equalization operation more accurately by performing the voltage equalization operation only with the discharge function using this point.

In the passive method, the smaller the resistance, the greater the voltage equalization effect, but the smaller the resistance, the leakage current increases. However, in FIG. 5, when the voltage of the electrical energy storage cell Cn is smaller than the average voltage, the discharge operation is stopped. . Therefore, the leakage current does not increase significantly even with a small resistor. For example, if a resistance of 50 Ohm is connected in parallel to an electric energy storage cell with a voltage of 2.5V, the current flowing through the resistor is 50mA. However, in FIG. 5, when the average voltage is 2.5V and the dV is 0.05V, when the load resistance RL is 50 Ohm, the current flowing through the load resistor RL is only 1mA. When the load resistance RL is 1 Ohm, the current flowing through the load resistor RL is 50 mA. 5 operates like the passive method, but the voltage equalization rate is much faster than the passive method, the voltage equalization accuracy is high, and the leakage current through the resistor is very small.

In the method as shown in FIG. 5, the load resistor RL is connected in parallel to the electrical energy storage cell Cn, and the voltage controller OPnP is connected in series to the load resistor RL, and the lower limit voltage for stopping the voltage equalization operation. Passive voltage equalization method with a lower limit voltage is controlled by the same reference voltage as the average voltage.

On the other hand, in the voltage equalization circuit as shown in FIG. 3, it is difficult to equalize voltages for the electric energy storage cells positioned at the highest voltage. In order to facilitate the following description, FIG. 3 includes four electrical energy storage cells, and the voltage of the fourth electrical energy storage cell (C4) is the highest, and the voltages of the remaining three electrical energy storage cells except the electrical energy storage cell # 4. A case where the controller OPnP is connected will be described.

In theory, as shown in FIG. 3, the remaining electrical energy storage cells except for the fourth electrical energy storage cell reach voltage equalization, and the four electrical energy storage cells naturally reach voltage equalization. However, in practice, the voltages of the remaining storage cells except for the fourth electrical energy storage cell are slightly different from the theoretical values due to the offset or resistance deviation of the op amp. The voltage will deviate significantly from the target value. It is difficult to correct this because the voltage controller is not connected to the 4th electrical energy storage cell. Since the positive voltage of the 4th electrical energy storage cell has a fixed value, in order to connect the voltage controller to the 4th electrical energy storage cell, the target voltage is generated by subtracting the reference voltage from the positive voltage of the 4th electrical energy storage cell. Can be connected to the cathode of No. 4 electrical energy storage cell. However, in this case, the voltage controller of the 3rd electrical energy storage cell and the voltage controller of the 4th electrical energy storage cell are connected to the same point, and the voltages of the two voltage controllers are different from each other due to offset or resistance error. Difficult to do

6 is a view for explaining a voltage equalization circuit according to another embodiment of the present invention, Figure 6a is a view showing the configuration of a controller for adjusting the reference voltage according to an embodiment of the present invention, Figure 6b is a view A circuit diagram of a voltage equalization circuit using a reference voltage regulated by the controller shown in 6a.

6B illustrates that in the embodiment of FIG. 3, the anode voltage V ⁺ C3 of the third electrical energy storage cell C3 is equal to the average voltage (V ⁺ C4-V ^- C1) at the total voltage (V ⁺ C4). / 4) includes a controller as shown in Figure 6a to adjust the reference voltage to be equal to the subtracted voltage. According to another embodiment of the present invention, the error caused by offset or resistance error in the target voltage generator and the voltage controller in the above-described embodiment is offset by slightly adjusting the reference voltage Vref. By doing so, it is possible to prevent the voltage error from accumulating in the fourth electrical energy storage cell C4.

6 illustrates an example in which the voltage controller is not installed in the electrical energy storage cell positioned at the highest voltage, even when the voltage controller is not installed in the lowest or middle portion. Can be prevented.

In this method, even when the voltage controller is connected to the cathode of the fourth electrical energy storage cell C4, the voltage controller voltage of the third electrical energy storage cell C3 and the voltage controller voltage of the fourth electrical energy storage cell C4 are maintained. It is more effective to reduce the deviation of.

As described above, the present invention provides a voltage equalization method between electrical energy storage cells in an electrical energy storage device in which electrical energy storage cells are connected in series. The electrical energy storage cell is an electric double layer capacitor, such as an electric double layer capacitor. Lead Acid Battery, NiMH Battery, NiCd Battery, Lithium Ion Battery, Aluminum Electrolytic Capacitor, as well as Ultracapacitor Can be used.

As mentioned above, although this invention was demonstrated in detail with reference to attached drawing, this is only an illustration, It is clear that various deformation | transformation and a change are possible within the scope of the technical idea of this invention. Therefore, the protection scope of the present invention should not be limited to the above-described embodiment, but should be determined to include the scope according to the description of the following claims and their equivalents.

Claims

In the voltage equalization circuit of the electrical energy storage device,

A series string comprising electrical energy storage cells connected in series;

A reference voltage generator for generating a voltage equalization reference voltage;

A target voltage generator configured to input the reference voltage to generate a voltage equalization target voltage; And

A voltage controller inputted to the target voltage and connected to the electrical energy storage cell of the series string to equalize the voltage of the electrical energy storage cell;

The target voltage generator,

And adding the reference voltage to the negative terminal voltage of the target electric energy storage cell of the series string or subtracting the reference voltage from the positive terminal voltage of the target electric energy storage cell to generate the target voltage.
The method of claim 1,

The voltage controller includes an op amp A voltage equalization circuit, characterized in that.
The method of claim 1,

And the target voltage generator comprises an op amp.
The method of claim 1,

And a discharge resistor is connected in parallel to the electrical energy storage cell of the series string, and the voltage controller is connected in series to the discharge resistor.
The method of claim 2,

And an amplifier for amplifying the current at the op amp output stage.
The method of claim 2 or 3,

The op amp comprises a rail-to-rail (Oil amplifier) of the voltage equalization circuit, characterized in that.
The method of claim 1,

And a controller capable of adjusting the reference voltage.
In the voltage equalization circuit of the electrical energy storage device,

A series string comprising electrical energy storage cells connected in series;

A discharge resistor connected in parallel to the electrical energy storage cell of the series string;

A reference voltage generator for generating a voltage equalization reference voltage; And

And a voltage controller configured to equalize the voltage of the electrical energy storage cell of the series string by receiving the reference voltage.

And the discharge resistor and the voltage controller are connected in series.
In the voltage equalization circuit of the electrical energy storage device,

A series string comprising electrical energy storage cells connected in series;

A reference voltage generator for generating a voltage equalization reference voltage; And

A voltage controller configured to equalize a voltage of the electrical energy storage cell by inputting the voltage equalization reference voltage and being connected to the electrical energy storage cell of the series string;

And at least one electric energy storage cell to which the voltage controller is not connected, further comprising a controller for adjusting the voltage equalization reference voltage using the voltage of the electric energy storage cell to which the voltage controller is not connected. Voltage equalization circuit.