KR102652875B1 - Apparatus for controlling connections between battery cells - Google Patents

Abstract

The present invention relates to a device that measures the internal resistance of each battery cell connected in series and controls the connection state of the battery cells according to the measured internal resistance. A battery cell connection control device according to an embodiment of the present invention is a device for controlling the connection between a plurality of battery cells constituting a battery module, including a test circuit connected to both ends of the battery cell and the test circuit and the battery cell. It includes a processor that selectively connects, wherein the processor identifies the internal resistance of the battery cell based on the voltage change across the battery cell that occurs before and after connection of the test circuit and the test current flowing in the test circuit, and The connection of the battery cells is controlled according to the size of the identified internal resistance.

Description

Device for controlling connections between battery cells {APPARATUS FOR CONTROLLING CONNECTIONS BETWEEN BATTERY CELLS}

The present invention relates to a device that identifies the internal resistance of each battery cell and controls the connection state of the battery cell according to the identified internal resistance.

The Energy Storage System (ESS) is a system that converts alternating current electricity supplied from the grid into direct current electricity, stores it in a battery, and provides the electricity stored in the battery to the load as needed.

The battery included in the ESS consists of multiple battery cells. Specifically, the ESS includes a battery rack, which is composed of a plurality of battery modules, and the battery module is composed of a plurality of battery cells connected in series.

Meanwhile, it has been confirmed that the main cause of recent ESS fire accidents is local overheating in the battery, which starts the fire and spreads to the entire system. For example, when overvoltage is applied to a battery cell, the insulation between the cathode and anode is destroyed, causing a short circuit, which can cause a fire. In addition, even if overvoltage is not applied, damage to the separator separating the cathode and anode, and an increase in the internal resistance of the battery cell due to poor bonding of the anode and cathode materials and the electrode plate, may also cause abnormal heat during charging and discharging, causing fire. .

In particular, an increase in the internal resistance of the battery cell generates Joule's heat due to charging and discharging current, which not only shortens the life of the battery but can also lead to a fire accident. Therefore, in order to evaluate the soundness of the battery during regular use of the ESS, It is necessary to identify the internal resistance of the battery and exclude battery cells with high internal resistance from the overall battery configuration.

The purpose of the present invention is to identify the internal resistance of each battery cell.

Additionally, the purpose of the present invention is to control the connection state between the battery cell and other battery cells according to the internal resistance of the battery cell.

The objects of the present invention are not limited to the objects mentioned above, and other objects and advantages of the present invention that are not mentioned can be understood by the following description and will be more clearly understood by the examples of the present invention. Additionally, it will be readily apparent that the objects and advantages of the present invention can be realized by the means and combinations thereof indicated in the patent claims.

A battery cell connection control device according to an embodiment of the present invention for achieving the above-described object includes a device for controlling the connection between a plurality of battery cells constituting a battery module, a test circuit connected to both ends of the battery cells, and and a processor that selectively connects the test circuit and the battery cell, wherein the processor determines the state of the battery cell based on a voltage change across the battery cell that occurs before and after connection of the test circuit and a test current flowing in the test circuit. It is characterized by identifying internal resistance and controlling the connection of the battery cells according to the size of the identified internal resistance.

In one embodiment, the test circuit includes a test resistor, a first switch connecting the test resistor to one end of the battery cell, and a second switch connected in parallel to both ends of the battery cell.

In one embodiment, the test circuit further includes a current sensor connected in series with the test resistor and a voltage sensor connected in parallel with both ends of the battery cell.

In one embodiment, the first and second switches are power switching elements that operate under control of the processor.

In one embodiment, the processor identifies the internal resistance by dividing the difference between the voltage across the battery cell before connecting the test circuit and the voltage across the battery cell after connecting the test circuit by the test current.

In one embodiment, the processor calculates the difference between the voltage across the battery cell measured with the first switch turned off and the voltage across the battery cell measured with the first switch turned on. The internal resistance is identified by dividing it by the test current measured with the switch turned on.

In one embodiment, the processor connects the test circuit and the battery cell according to a preset test cycle.

In one embodiment, the processor connects the test circuit and the battery cell according to a preset frequency, and identifies the internal resistance based on the effective value of the voltage across the battery cell and the effective value of the test current. Do it as

In one embodiment, the processor disconnects the battery cell from the battery module when the internal resistance exceeds a reference value.

In one embodiment, the processor turns on the second switch when the internal resistance exceeds a reference value.

The present invention allows users to monitor the fire risk of each battery cell by identifying the internal resistance of each battery cell.

In addition, the present invention can fundamentally prevent the risk of fire due to an increase in the internal resistance of the battery cell by separating the battery cell with high internal resistance from the battery module.

In addition to the above-described effects, specific effects of the present invention are described below while explaining specific details for carrying out the invention.

1 is a diagram illustrating a battery cell connection control device according to an embodiment of the present invention.
2 is an equivalent circuit diagram of a battery cell.
3 is an equivalent circuit diagram of a battery module.
4 and 5 are diagrams showing a battery module being charged or discharged.
Figure 6 is a diagram showing a test circuit connected to a battery cell according to an embodiment of the present invention.
Figure 7 is a diagram showing a test circuit connected to a battery module according to an embodiment of the present invention.
Figures 8 and 9 are diagrams for explaining a method of identifying the internal resistance of a battery cell when the battery cell is being charged or discharged.
Figure 10 is a diagram showing disconnection of a specific battery cell from a battery module.
Figure 11 is an equivalent circuit diagram of the circuit shown in Figure 10.

The above-mentioned objects, features, and advantages will be described in detail later with reference to the attached drawings, so that those skilled in the art will be able to easily implement the technical idea of the present invention. In describing the present invention, if it is determined that a detailed description of known technologies related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description will be omitted. Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the attached drawings. In the drawings, identical reference numerals are used to indicate identical or similar components.

In this specification, first, second, etc. are used to describe various components, but of course, these components are not limited by these terms. These terms are only used to distinguish one component from another component, and unless specifically stated to the contrary, the first component may also be a second component.

Additionally, in this specification, when a component is described as being “connected,” “coupled,” or “connected” to another component, the components may be directly connected or connected to each other, but there are other components between each component. It should be understood that elements may be “interposed,” or each component may be “connected,” “combined,” or “connected” through other components.

Additionally, as used herein, singular expressions include plural expressions, unless the context clearly dictates otherwise. In the present application, terms such as “consists of” or “comprises” should not be construed as necessarily including all of the various components or steps described in the specification, and some of the components or steps may include It may not be included, or it should be interpreted as including additional components or steps.

In addition, in this specification, when referring to "A and/or B", this means A, B or A and B, unless otherwise specified, and when referring to "C to D", this means unless specifically stated to the contrary. Unless otherwise stated, it means C or higher and D or lower.

The present invention relates to a device that identifies the internal resistance of each battery cell and controls the connection state of the battery cell according to the identified internal resistance. Hereinafter, a battery cell connection control device according to an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 11.

1 is a diagram illustrating a battery cell connection control device according to an embodiment of the present invention.

Figure 2 is an equivalent circuit diagram of a battery cell, and Figure 3 is an equivalent circuit diagram of a battery module.

Figures 4 and 5 are diagrams showing how a battery module is being charged or discharged.

FIG. 6 is a diagram showing a test circuit connected to a battery cell according to an embodiment of the present invention, and FIG. 7 is a diagram showing a test circuit connected to a battery module according to an embodiment of the present invention.

FIGS. 8 and 9 are diagrams for explaining a method of identifying the internal resistance of a battery cell when the battery cell is being charged or discharged.

FIG. 10 is a diagram illustrating disconnecting a specific battery cell from a battery module, and FIG. 11 is an equivalent circuit diagram of the circuit shown in FIG. 10.

Referring to FIG. 1, the battery cell connection control device 1 according to an embodiment of the present invention includes a test circuit 10, a processor 20, and a memory (not shown) for operating the processor 20. can do. However, the battery cell connection control device 1 shown in FIG. 1 is according to one embodiment, and its components are not limited to the embodiment shown in FIG. 1, and some components may be added or changed as needed. Or it can be deleted.

The present invention is an apparatus for controlling the connection between a plurality of battery cells 100 constituting a battery module 200. Accordingly, before explaining the operation of the invention in detail, the battery cell 100 and the battery module 200 will be described in detail.

The battery cell 100 of the present invention is used in a secondary battery and may be composed of a voltage source (Vb) for charging and discharging and an internal resistance (Rs).

Referring to FIG. 2, the battery cell 100 can be equivalent to a circuit in which a voltage source (Vb) and an internal resistance (Rs) are connected in series. At this time, the voltage source Vb is a circuit element capable of charging and discharging and may be shown as a capacitor. Hereinafter, for convenience of explanation, the voltage source included in the battery cell 100 will be referred to as cell voltage (Vb).

A plurality of such battery cells 100 may be connected in series to form the battery module 200.

3 as an example, the battery cell 100 may be composed of 60 battery cells 100 connected in series. As described in FIG. 2, each battery cell 100 may include cell voltages (Vb1, Vb2,..., Vb60) and internal resistances (Rs1, Rs2,..., Rs60).

This battery module 200 can be connected to the charge/discharge circuit 300 to be charged or discharged. More specifically, the battery module 200 may be connected to the charge/discharge circuit 300 and may be charged or discharged depending on the voltage level of the charge/discharge circuit 300.

Referring to FIGS. 4 and 5 together, each battery cell 100 constituting the battery module 200 may have a cell voltage (Vb) of 3.7 [V], and the battery module 200 has a charge/discharge circuit. It can be connected to (300). Meanwhile, the charge/discharge circuit 300 includes a charge/discharge voltage (Vs) and a charge/discharge resistance (R _L ), where the charge/discharge resistance (R _L ) is a resistance inside the charge/discharge circuit 300, and the charge/discharge loss It may be a circuit element to represent.

Since 60 battery cells 100 with a cell voltage (Vb) of 3.7 [V] are connected, the voltage of the battery module 200 is 222 [V], and as shown in FIG. 4, the charge and discharge voltage (Vs) is When the voltage is 228 [V], which is greater than the voltage of the battery module 200, current flows toward the battery module 200 and the battery module 200 can be charged. On the other hand, as shown in FIG. 5, when the charge/discharge voltage (Vs) is 216 [V], which is less than the voltage of the battery module 200, current flows toward the charge/discharge circuit 300 and the battery module 200 is discharged. You can.

Each battery cell 100 constituting the battery module 200 can be charged and discharged according to the above-described method. At this time, if the internal resistance (Rs) of a specific battery cell 100 increases due to internal and/or external factors, Joule's heat due to charge/discharge current is generated, and if the heat generation amount is large, the battery cell ( A fire may start in 100) and cause a fire in the battery module 200 and the entire ESS including it.

In order to solve this problem, the present invention monitors the internal resistance (Rs) of the battery cell (100) using the test circuit (10) and disconnects the battery cell (100) with high internal resistance (Rs). Fires caused by an increase in resistance (Rs) can be prevented in advance.

Hereinafter, the specific operation of the present invention will be described.

The test circuit 10 can be connected to both ends of the battery cell 100, and the processor 20 can selectively connect the test circuit 10 and the battery cell 100. More specifically, the test circuit 10 may be connected to both ends of the battery cell 100 through a switch, and the processor 20 electrically connects or connects the test circuit 10 and the battery cell 100 by controlling the switch. It can be released.

Referring to FIG. 6, the test circuit 10 may be connected to both ends of the battery cell 100. The test circuit 10 includes a test resistance (Rt), a first switch (S1) connecting the test resistance (Rt) and one end of the battery cell 100, and a second switch connected in parallel to both ends of the battery cell 100 ( S2), a current sensor (A) connected in series with the test resistance (Rt), and a voltage sensor (V) connected in parallel to both ends of the battery cell 100. However, the test circuit 10 shown in FIG. 6 is according to one embodiment, and the components constituting the circuit are not limited to the embodiment shown in FIG. 6, and some components can be added or changed as needed. Or it can be deleted.

Meanwhile, in FIG. 6, only the test circuit 10 is shown connected to both ends of one battery cell 100, but this is for convenience of explanation, and the test circuit 10 is connected to all battery cells constituting the battery module 200. (100) Can be connected to both ends, respectively. Accordingly, hereinafter, only a single test circuit 10 will be shown and explained, but the operations described later can be applied to all test circuits 10 connected to each battery cell 100.

The processor 20 may generate a control signal (Sc) for opening and closing the first and second switches (S1, S2), and the first and second switches (S1, S2) may respond to the corresponding control signal (Sc). It can operate accordingly. Specifically, the first switch S1 may be opened and closed according to the first control signal Sc1, and the second switch S2 may be opened and closed according to the second control signal Sc2.

To this end, the first and second switches S1 and S2 may be implemented as power switching elements. For example, the first and second switches S1 and S2 may be implemented with an insulated-gate bipolar transistor (IGBT), a bipolar junction transistor (BJT), or a metal oxide semiconductor field effect transistor (MOSFET). At this time, the power switching element may be turned on and off according to a control signal (Sc, for example, a gate signal) provided from the processor 20.

Meanwhile, the current sensor (A) can measure the test current (It), which will be described later, and provide it to the processor 20, and the voltage sensor (V) can measure the voltage (Vt) across the battery cell 100 and provide it to the processor 20. ) can be provided. The processor 20 can identify the internal resistance (Rs) of the battery cell 100 through calculation using values provided from each sensor (A, V).

Hereinafter, the operation of the processor 20 will be described in detail.

The processor 20 selectively connects the test circuit 10 to the battery cell 100, and changes the voltage on both ends of the battery cell 100 that occurs before and after connection of the test circuit 10 and the voltage flowing in the test circuit 10. The internal resistance (Rs) of the battery cell 100 can be identified based on the test current (It).

Referring to FIG. 7 , the processor 20 can selectively connect the test circuit 10 to the battery cell 100 by controlling the first switch S1 on/off.

When the test circuit 10 is connected to the battery cell 100, a portion of the current that charges or discharges the battery cell 100 may flow into the test circuit 10. The processor 20 measures the voltage across the battery cell 100 that occurs before and after connecting the test circuit 10, and measures the test current (It) flowing into the test circuit 10 after connecting the test circuit 10. The internal resistance (Rs) of the battery cell 100 can be identified.

More specifically, the processor 20 tests the difference between the voltage (Vt) at both ends of the battery cell 100 before connecting the test circuit 10 and the voltage (Vt) at both ends of the battery cell 100 after connecting the test circuit 10. The internal resistance (Rs) of the battery cell 100 can be identified by dividing it by the current (It). The principle of identifying the internal resistance (Rs) in this way will be explained below. For convenience of explanation, the voltage (Vt) at both ends of the battery cell (100) is set to the off voltage before connecting the test circuit (10). (Voff), after connecting the test circuit 10, the voltage (Vt) at both ends of the battery cell 100 is expressed as the on voltage (Von).

When the battery module 200 shown in FIG. 7 is charging, the circuit shown in FIG. 7 can be equivalent to FIG. 8, and when the battery module 200 shown in FIG. 7 is discharging, the circuit shown in FIG. The circuit can be equivalent as shown in Figure 9.

Referring to FIGS. 8 and 9, the equivalent composite voltage (Vc) is the cell voltage ( Vb) can be subtracted from the value (Vs-(Vb2+Vb3+...+Vb60)), and the equivalent composite resistance (Rc) can be defined as all battery cells except the battery cell 100 to which the test circuit 10 is connected ( 100) can be defined as the sum of the internal resistance (Rs) and the charge/discharge resistance (R _L ) (R _L +Rs2+Rs3+...+Rs60).

When the first switch (S1) is in the off state, the off voltage may satisfy the equation shown in [Equation 1] below, and the circuit shown in FIG. 8 can be expressed as [Equation 2] according to Kirchhoff's law. ] can satisfy the same equation.

Meanwhile, when the first switch (S1) changes to the on state, the test current (It) flowing in the test circuit (10) can satisfy the equation shown in [Equation 3] below, and the circuit shown in FIG. According to Kirchhoff's law, the equation shown in [Equation 4] below can be satisfied.

가 성립할 수 있으며, 이에 따라 [수학식 5]는 [수학식 6]과 같이 근사될 수 있다.When [Equation 4] is substituted into [Equation 3], the following equation is established as [Equation 5], and the composite resistance is much larger than the internal resistance (Rs1) of the single battery cell 100.

can be established, and accordingly, [Equation 5] can be approximated as [Equation 6].

According to the equations described above, the processor 20 determines the voltage (Vt) at both ends of the battery cell 100 before connecting the test circuit 10 and the voltage (Vt) at both ends of the battery cell 100 after connecting the test circuit 10. The internal resistance (Rs) of the battery cell 100 can be identified by dividing the difference by the test current (It).

More specifically, the processor 20 may measure the off voltage (Voff) through the voltage sensor (V) while the first switch (S1) is controlled to be off. Subsequently, the processor 20 can measure the on voltage (Von) through the voltage sensor (V) while controlling the second switch (S2) to be on, and measure the test current (It) through the current sensor (A). It can be measured. The processor 20 can identify the difference between the off voltage (Voff) and the on voltage (Von) divided by the test current (It) as the internal resistance (Rs) of the battery cell 100, as shown in [Equation 6]. there is.

The processor 20 may identify the internal resistance (Rs) of the battery cell 100 by connecting the test circuit 10 and the battery cell 100 according to a preset test cycle. Here, the preset test cycle can be arbitrarily set by the user and stored in the memory.

By setting the test cycle, real-time monitoring of the battery cell 100 can be provided. For example, if the user sets the test cycle to 1 minute, the processor 20 can identify the internal resistance (Rs) of the battery cell 100 every minute, and the user can identify the internal resistance (Rs) of the battery cell 100 every minute. ) can be monitored for abnormalities.

Meanwhile, since the above-described method of identifying the internal resistance (Rs) uses the voltage across both ends (Vt) and the test current (It) at a specific point in time, noise may occur in identifying the internal resistance (Rs). To prevent this, the processor 20 connects the test circuit 10 and the battery cell 100 according to a preset frequency, and calculates the root mean square (RMS) of the voltage (Vt) across both ends of the battery cell 100. The internal resistance (Rs) of the battery cell 100 can be identified based on the effective value of the test current (It).

For example, the processor 20 may control the first switching element on/off according to a cycle of 500 [Hz]. In this case, the above-mentioned off voltage, on voltage, and test current (It) all have an alternating current waveform with a frequency of 500 [Hz], and the processor 20 calculates the effective value of each voltage (V _off , V _on ) , the internal resistance (Rs) of the battery cell 100 can be identified using the effective value of the test current (It). Specifically, the processor 20 can identify the internal resistance (Rs) according to Equation 7 below.

In this way, when identifying the internal resistance (Rs) using the effective value, the accuracy of identifying the internal resistance (Rs) can be increased.

As described above, the present invention can accurately identify the internal resistance (Rs) of each battery cell 100 in real time, and thus the user can monitor the fire risk of each battery cell 100.

The processor 20 may control the connection of the battery cell 100 according to the size of the internal resistance (Rs) identified according to the method described above.

More specifically, the processor 20 may compare the internal resistance (Rs) of each battery cell 100 with a reference value, and if the internal resistance (Rs) of the battery cell 100 is less than the reference value as a result of the comparison, the corresponding battery cell 100 ) and other battery cells 100 can be maintained. On the other hand, if the internal resistance (Rs) of a specific battery cell 100 exceeds the reference value, the connection between the battery cell 100 and other battery cells 100 may be disconnected.

In other words, the processor 20 may separate the battery cell 100 whose internal resistance (Rs) exceeds the reference value from the battery module 200 among the plurality of battery cells 100 constituting the battery module 200. . Here, the reference value may be arbitrarily set by the user and stored in memory, and may be set to a value lower than the limit resistance that the battery cell 100 can endure.

Referring to FIG. 10, the processor 20 may determine that the internal resistance (Rs1) of the first battery cell 100 exceeds the reference value, and the remaining battery cells 100 except the first battery cell 100 The internal resistance (Rs2, Rs3,…, Rs60) can be judged to be below the standard value. At this time, the processor 20 controls to turn on the second switch S2 of the test circuit 10 connected to the first battery cell 100 to separate the first battery cell 100 from the other battery module 200. You can.

When the second switch S2 is controlled to be on, the second switch S2 may form a bypass path, and the charge/discharge current flowing through the first battery cell 100 flows through the bypass path, that is, the second switch S2. It can flow to switch (S2).

Referring to FIG. 11, when the second switch S2 of the test circuit 10 connected to the first battery cell 100 forms a bypass path, the battery module 200 is connected as shown in FIG. 11. You can. That is, the first battery cell 100 having a high internal resistance (Rs) can be separated from the battery module 200.

As described above, the present invention can fundamentally prevent the risk of fire due to an increase in the internal resistance (Rs) of the battery cell 100 by separating the battery cell 100 with high internal resistance (Rs) from the battery module 200. there is.

As described above, the present invention has been described with reference to the illustrative drawings, but the present invention is not limited to the embodiments and drawings disclosed herein, and various modifications may be made by those skilled in the art within the scope of the technical idea of the present invention. It is obvious that transformation can occur. In addition, although the operational effects according to the configuration of the present invention were not explicitly described and explained while explaining the embodiments of the present invention above, it is natural that the predictable effects due to the configuration should also be recognized.

Claims (10)

In a device for controlling the connection between a plurality of battery cells that are connected in series to each other and constitute a battery module,
a test circuit connected to both ends of the battery cell; and
A processor that selectively connects the test circuit and the battery cell,
The processor determines whether the test circuit is connected based on the voltage change across the battery cells that occurs before and after connection of the test circuit when all battery cells constituting the battery module are being charged or discharged and the test current flowing in the test circuit. Identifying the internal resistance of a battery cell and controlling the connection of the battery cell according to the size of the identified internal resistance,
The internal resistance identification operation is performed independently in each case when the battery cell is charging and discharging.
Battery cell connection control unit.
According to paragraph 1,
The test circuit is
test resistance,
A first switch connecting the test resistor and one end of the battery cell,
Comprising a second switch connected in parallel to both ends of the battery cell
Battery cell connection control unit.
According to paragraph 2,
The test circuit is
A current sensor connected in series with the test resistor,
Further comprising a voltage sensor connected in parallel to both ends of the battery cell.
Battery cell connection control unit.
According to paragraph 2,
The first and second switches are power switching elements that operate under the control of the processor.
Battery cell connection control unit.
According to paragraph 1,
The processor identifies the internal resistance by dividing the difference between the voltage across the battery cell before connecting the test circuit and the voltage across the battery cell after connecting the test circuit by the test current.
Battery cell connection control unit.
According to paragraph 2,
The processor controls the first switch to turn on the difference between the voltage across the battery cell measured with the first switch turned off and the voltage across the battery cell measured with the first switch turned on. Identifying the internal resistance by dividing it by the test current measured in the
Battery cell connection control unit.
According to paragraph 1,
The processor connects the test circuit and the battery cell according to a preset test cycle.
Battery cell connection control unit.
According to paragraph 1,
The processor connects the test circuit and the battery cell according to a preset frequency, and identifies the internal resistance based on the effective value of the voltage across the battery cell and the effective value of the test current.
Battery cell connection control unit.
According to paragraph 1,
The processor disconnects the battery cell from the battery module when the internal resistance exceeds a reference value.
Battery cell connection control unit.
According to paragraph 2,
The processor controls the second switch to turn on when the internal resistance exceeds the reference value.
Battery cell connection control unit.

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