KR102632405B1 - Large-scale battery system including fault-current limiting circuit - Google Patents

Abstract

The present invention relates to a battery pack system including a fault current reduction circuit, and more specifically, to a set battery system that reduces and controls the fault current that may occur in a high-power battery system to prevent the possibility of battery explosion and other accidents due to fault current. It's about the battery system.
A battery system including a fault current reduction circuit of the present invention includes: a main power line; a battery string including a plurality of battery cells and connected to provide discharge current of the battery cells to the main power line; a current-limiting resistor for guiding and limiting the path of the fault current between the main power line and the battery string when a fault current occurs; a bypass switch unit connected in parallel with the current-limiting resistor and switched so that the fault current is bypassed by the current-limiting resistor; a current measuring unit for measuring current between the main power line and the battery string; And when the first sampling current measured by the current measuring unit is outside the current size within a predetermined normal range, it is determined that the fault current has occurred and the bypass switch unit is controlled to switch so that the fault current is guided to the current limiting resistance unit. Includes a fault current control unit. As a result, when a fault current occurs, it is possible to reduce the fault current for hundreds of milliseconds and stabilize the system through switching control through fault current prediction, thereby preventing thermal runaway and chain fire explosion of the high-power battery string.

Description

Collective battery system including fault current reduction circuit {LARGE-SCALE BATTERY SYSTEM INCLUDING FAULT-CURRENT LIMITING CIRCUIT}

The present invention relates to a collective battery system, and more specifically, to a collective battery system that prevents the possibility of battery explosion and other accidents due to fault current by reducing and controlling fault current that may occur in a high-power battery system.

High-power battery systems are increasingly being commercialized in various industrial fields.

Passenger electric vehicles use a 20kWh battery as driving power, and electric buses are operated with a 100kWh driving battery. Recently, MW-level ESS has been promoted, while MW-level electric ships, aircraft, and military equipment, as well as home appliances such as high-power vacuum cleaners, are being developed and commercialized one after another.

As the capacity, size, and safety of secondary batteries have improved, and the economic efficiency per unit of power has greatly improved, the scope of use in various industrial fields is increasing, but the risk of accidents due to explosion of secondary batteries is still a problem.

Research is continuing to advance BMS technology, including the commercialization of safety circuits at the battery cell level to ensure the safety of secondary batteries, but there are no reliable measures in place to prevent transient currents, thermal runaway, and explosions caused by system abnormalities. The situation is not there. Battery thermal runaway, fire, and explosion accidents caused by fault current are constantly making news every year, such as electric vehicle driving battery fire accidents and the Boeing Company aircraft shutdown due to a battery fire at Yuasa Corporation in Japan.

Conventionally, methods of using superconductors have been intensively developed as a technology to reduce fault current. Although superconductors are suitable for use in large-scale power facilities, they are difficult to use in electric vehicles, electric ships, aircraft, military equipment, etc. To solve the problem, some research is being conducted to develop ultra-light superconductors.

Thermal runaway of the secondary battery occurs rapidly, and the resulting increase in fault current, heat diffusion, and explosion of tens of kWh to several MWh due to chain occurrence of fire and explosion are highly likely to cause a fatal accident. There is a need for electronic control technology to quickly reduce and control fault current before it occurs.

International Patent Publication WO2011/157305A1 Republic of Korea Patent Publication No. 2009-0026900

The present invention was developed to prevent thermal runaway and chain fire explosion of the conventional battery system described above. When a fault current occurs, it can reduce the fault current for hundreds of milliseconds and stabilize the system through switching control through fault current prediction. The purpose is to provide a collective battery system.

The above object is to provide a collective battery system including a fault current reduction circuit according to an aspect of the present invention, comprising: a main power line; a battery string including a plurality of battery cells and connected to provide discharge current of the battery cells to the main power line; a current-limiting resistor for guiding and limiting the path of the fault current between the main power line and the battery string when a fault current occurs; a bypass switch unit connected in parallel with the current-limiting resistor and switched so that the fault current is bypassed by the current-limiting resistor; a current measuring unit for measuring current between the main power line and the battery string; And when the first sampling current measured by the current measuring unit is outside the current size within a predetermined normal range, it is determined that the fault current has occurred and the bypass switch unit is controlled to switch so that the fault current is guided to the current limiting resistance unit. This can be achieved by a collective battery system including a fault current reduction circuit characterized by including a fault current control unit.

The collective battery system further includes a current-limiting resistance switch unit connected in series with the current-limiting resistance unit to switch whether the fault current is conducted to the current resistance unit, and the fault current control unit controls the current-limiting resistance unit at a predetermined sampling time interval. The bypass switch unit and the current-limiting resistance switch unit may be selectively controlled based on the magnitude of the second sampling current measured by the current measurement unit and the current increase/decrease rate per sampling time compared to the first sampling current. Additionally, the fault current control unit may turn off the current limiting resistance switch unit when the magnitude of the third sampling current expected after the sampling time based on the current increase/decrease rate is greater than or equal to a predetermined risk value.

In addition, the collective battery system further includes a current-limiting resistance switch unit connected in series with the current-limiting resistance unit to switch whether the fault current is conducted to the current resistance unit, and the fault current control unit is the nth current measuring unit. (hereinafter, n is an arbitrary natural number) The current increase/decrease rate is updated based on the sampling current, and the size of the n+1th sampling current expected after the sampling time has elapsed is predetermined based on the updated current increase/decrease rate. If the value is greater than or equal to this value, the current-limiting resistance switch unit may be turned off. Here, the fault current control unit may vary the risk value according to the sampling number n.

In addition, the fault current control unit updates the current increase/decrease rate based on the nth sampling current of the current measuring unit, and determines the size of the n+1th sampling current expected after the sampling time has elapsed based on the updated current increase/decrease rate. If is below a predetermined stable value, the bypass switch unit may be controlled to switch so that the current is not bypassed to the current limiting resistor unit.

In addition, the bypass switch unit may include a two-way switch in which a pair of transistors are connected in parallel, and may further include an inductor on a current path between the main power line and the battery string, and sampling of the current measurement unit. The time interval may be determined according to the time constant.

In addition, the collective battery system further includes a current-limiting resistance switch unit connected in series with the current-limiting resistance unit to switch whether the fault current is conducted to the current resistance unit, and the current measured by the current measuring unit is within the normal range. If it is smaller than that, the fault current control unit selectively controls the current-limiting resistance switch unit based on the size of the second sampling current measured by the current measurement unit at a predetermined sampling time interval and the current increase/decrease rate per sampling time compared to the first sampling current. This can be done through blocking control.

The present invention reduces the fault current for hundreds of milliseconds when a fault current occurs and stabilizes the system through switching control through fault current prediction, thereby preventing thermal runaway and chain fire explosion of high-power battery cells.

1 is a schematic block diagram of a battery system including a fault current reduction circuit according to an embodiment of the present invention;
Figure 2 is a detailed circuit diagram of a battery pack system including a fault current reduction circuit according to an embodiment of the present invention; and
Figure 3 is a flowchart showing a control method of a battery pack system including a fault current reduction circuit according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the attached drawings.

Figure 1 is a schematic block diagram of a battery pack system including a fault current reduction circuit according to an embodiment of the present invention, and Figure 2 is a detailed circuit diagram according to an embodiment of the present invention.

Referring to Figures 1 and 2, the battery system according to an embodiment of the present invention includes a main power line (1), a battery string (2), a current-limiting resistor (3), a bypass switch unit (4), and a current-limiting resistor. It is comprised of a switch unit (5), a current measurement unit (6), an electronic switch unit (7), and a fault current control unit (8).

The main power line (1) is a power line that acts as a bridge to ensure that the power supplied from the battery string (2) is supplied to the entire system. For example, electronic devices such as electric vehicles, electric ships, electric aircraft, and electric submarines are connected to the battery string. It comprehensively refers to any DC network that can receive the power supplied in (2).

The battery string (2) is composed of connecting multiple battery cells in series or in series and parallel, and provides power to the main power line (1) when discharging, while providing power from an external power source or through an internal generator when charging. Charge.

The current limiting resistor (3) is provided to guide and limit the fault current flowing due to any fault that occurs in the system connected to the main power line (1) or the battery string (2). Here, failure includes fire and battery operation interruption due to battery cell penetration, malfunction, overheating, short circuit, electrolyte leak, etc., and refers to an abnormal operating condition caused by an error in any part of the system, and the fault current is the cause of such failure. Also refers to the current generated by .

The current-limiting resistor 3 is provided in parallel with the normal current supply line between the main power line 1 and the battery string 2, and on a bypass path. Figure 2 shows an exemplary configuration with one resistor. The current-limiting resistor 3 is to have a level of resistance or impedance necessary to limit the size of the fault current. For example, it can be determined by considering the system impedance to limit a current of tens of thousands of amperes to a current of several hundred amperes or less. .

The bypass switch unit (4) is used to bypass the fault current to the current limiting resistor unit (3) when a fault current occurs, and is provided on the normal current supply line between the main power line (1) and the battery string (2). . The bypass switch unit 4 may be implemented as a pair of transistors for bypass through conduction and blocking of bidirectional current due to charging and discharging. In the circuit of Figure 2, when the Q1 switch conducts, charging current is provided through Q1 to the battery string 2, and when the Q2 switch conducts, the discharging current of the battery string 2 is supplied through Q2 to the DC network, 2 When all switches are turned off, the current is bypassed to the current-limiting resistor (3).

The current-limiting resistance switch unit 5 is installed to conduct or block the bypassed fault current. When the system impedance is low and the resistance of the current-limiting resistor (3) is small, in order to conduct or block the fault current to the current-limiting resistor (3), an additional switch is connected in series to the current-limiting resistor (3) to switch the current. is required, and in the circuit of Figure 2, the Q3 and Q4 switches are implemented in parallel as a bidirectional switch required according to battery charging and discharging.

The current measuring unit 6 is used to measure the current transmitted between the main power line 1 and the battery string 2, and can be implemented as a current transformer (CT) that converts the current to a size suitable for the controller. Those skilled in the art will understand that in the known field of CT technology, various types of current transformers can be adopted.

The electronic switch (7) is installed to block or supply power exchange between the main power line (1) and the battery string (2) by user operation, and as shown in Figure 2, it uses an electromagnetic contactor (magnetic contactor). It can be implemented with a contactor (MC)) or an electronic switch (magnetic switch (MS)). The electronic switch unit 7 is intended to be used as a main contact point for high power, and a person skilled in the art will easily understand that there is some difference in use from the power semiconductor device or relay used in the bypass switch unit 4.

The fault current control unit (8) is for switching control according to the occurrence of fault current and the fluctuation trend of the fault current. By inputting the measured current value measured and provided by the current measuring unit (6), the bypass switch unit (4) and the current limiter are connected. Stable operation of the system is performed by controlling the resistance switch unit (5) and the electronic switch unit (7).

As shown in Figure 2, the fault current control unit 8 is implemented with a controller and software mounted on it, and includes a battery voltage detection pin, a current input pin input from the CT, and bypass and current limiting resistance switching units 4 and 5. ) of transistors (Q1 to Q4), gator driving signal driver pin, electronic switch (7) control output pin, etc.

In addition, among the elements shown in Figure 2, a varistor (Var.) connected in parallel with the battery string (2) to protect the battery fault current reduction circuit, an inductor to delay the transition time of the fault current, a current transformer, and various stored power A diode (D), fuse, etc. for freewheeling are further included.

Hereinafter, with reference to FIG. 3, the block diagram and operation of the circuit illustrated in FIG. 1 and/or FIG. 2 will be described.

Figure 3 is a flowchart showing a control method of a battery pack system including a fault current reduction circuit according to an embodiment of the present invention.

In terms of operation of the battery string 2, the operating state can be divided into charging and discharging operations. In a normal charging state, Q1 will be in the on state, and the remaining Q2 to Q4 will remain in the off state to transfer power from the main power line (1) to the battery string (2). In a normal discharging state, Q2 will be in the on state. The remaining switches Q1, Q3, and Q4 will be turned off, allowing power to be transferred from the battery string (2) to the main power line (1). The CT of the current measuring unit 6 measures the magnitude of the charge/discharge current continuously or at predetermined sampling time intervals and provides information to the controller (S10).

If the measured current is within a normal range that can be seen as normal operation (S11), the fault current control unit 8 does not perform switching control and keeps Q1 or Q2 in the on state to maintain the charging and discharging state. On the other hand, if the fault current control unit 8 determines that the measured current is outside the normal range and is a fault current (S11), the fault current can be bypassed (S12).

In order for the fault current to be bypassed, in the charging state, Q1 is turned off and Q3 is turned on, and in the discharging state, Q2 is turned off and Q4 is turned on, thereby bypassing the fault current to the current limiting resistor (3). You can.

As described above, the fault current control unit 8 controls the gate signals of transistors Q1 to Q4 to form a bypass path (S12).

After the fault current is first measured, the fault current control unit 8 takes the sampling value of the next fault current (S13). Here, the sampling value of the fault current is a value measured at sampling time intervals in the current measurement unit 6 or in an operation performed in the controller among the values continuously measured by the current measurement unit 6 (software based on the clock). It can be said to be a value that is processed at predetermined time intervals. Here, the sampling interval is preferably determined considering the time delay effect of the inductor shown in Figure 2, and is determined experimentally based on the magnitude of the normal current and fault current and the magnitude of the inductance.

If the secondary measured sampling current is within the normal range (or below a predetermined stable value) (S14), the bypass state is released and the transistors are turned on and off to return to the original normal state (S15).

On the other hand, if the secondary measured sampling current is not within the normal range (S14) and the secondary measured current is greater than a predetermined dangerous value (S16), the main current limiting resistance switch unit (5) is immediately controlled to turn off. Electrically cut off the space between the power line (1) and the battery string (2) (S21).

In step S16, if the measured sampling current is not above the dangerous value, the increase/decrease rate of the fault current is calculated (S17), and the next sampling current is predicted to determine whether the expected current at the next sampling is above the dangerous value (S18, S19) ).

The increase/decrease rate of the fault current can be determined in a linear or non-linear manner depending on the number of samples of the sampled measurement current. If the number of samples is insufficient, it is better to predict the increase/decrease trend of the fault current more clearly by calculating the change rate of the increase rate of the fault current. possible.

The next sampling current can be predicted by comparing the size and increase/decrease rate of the currently sampled measurement current. The 'expected current at next sampling' used as a comparison object in step S19 can be interpreted as 'measured current expected within a predetermined number of sampling times', which can be set arbitrarily in system design.

The important point is when the fault current will increase beyond the dangerous value through the increase/decrease rate, by determining whether the current measured at the next sampling will exceed the dangerous value or whether it will exceed the dangerous value after five or more sampling measurements. , it is possible to determine when to turn off the current-limiting resistance switch unit 5 or monitor whether it will return to a normal state while suppressing the current in a fault state.

Therefore, step S19 can be replaced with a step of determining whether the sampling current next time or within a predetermined number of times exceeds the critical value.

Again, going back to Figure 3, if the size of the next sampling current expected in step S19 is greater than the critical value, the current-limiting resistance switch unit 5 is immediately turned off (S21) to insulate the battery string 2, thereby insulating the battery string. Make sure to prevent thermal runaway in (2).

Meanwhile, if the next sampling current expected in step S19 is smaller than the risk value, the risk value used as the judgment standard is adjusted (S20), then the current sampling value is measured again and the sequential procedure is repeated from step S13.

The increase rate of the fault current is reduced by the inductor in the circuit diagram of Figure 2, and if the fault current continues to be neither returned to normal nor increased beyond the set very dangerous risk value despite repeated sampling times. The current limiting resistance switch unit (5) is turned off to lower the risk value and enable inspection of the fault condition.

If the risk value is lowered, the possibility that step S21, which is the turn-off step of the current-limiting resistance switch unit 5, will be performed after comparing the size of the sampling current measured in step S16 increases, and there is also a possibility that the judgment in step S19 will be judged as yes. This becomes higher.

Although the embodiments of the present invention have been described so far, those skilled in the art will understand that it is possible to partially replace or modify the embodiments of the present invention without departing from the technical spirit of the present invention. will be.

For example, when calculating the sampling increase/decrease rate, it is possible to increase the number of samples, calculate the current increase/decrease rate based on this, and then turn off the current limiting resistance switch unit 5 according to the possibility of returning to the normal state. In this case, a modification is possible so that step S13 is performed if the predetermined sampling number is not met after step S16 in FIG. 3.

Additionally, as described above, it is possible to set the current value estimated and compared in steps S18 and S19 to a value after a predetermined time rather than the next sampling.

The above-described embodiment focuses on the insulation of the battery string 2 due to high current as the fault current increases, but the current is measured even when it is determined that the battery string 2 has failed because the fault current is lower than the normal current. It will be understood that switching control that insulates the battery string (2) from the main power line (1) is also possible.

Therefore, the above-described embodiments of the present invention should be understood as illustrative, and the scope of protection of the present invention should be interpreted as extending to the technical spirit of the invention and equivalents thereof as set forth in the patent claims.

R: Current resistance
CT: current transformer
Q1~Q4: Transistor
Var. : Varistor
D: diode

Claims (9)

In a collective battery system including a fault current reduction circuit,
main power lines;
a battery string including a plurality of battery cells and connected to provide discharge current of the battery cells to the main power line;
a current-limiting resistor for guiding and limiting the path of the fault current between the main power line and the battery string when a fault current occurs;
a bypass switch unit connected in parallel with the current-limiting resistor and switched so that the fault current is bypassed by the current-limiting resistor;
a current measuring unit for measuring current between the main power line and the battery string; and
If the first sampling current measured by the current measuring unit is outside the current size within the predetermined normal range, it is determined that the fault current has occurred, and the bypass switch unit is switched and controlled to guide the fault current to the current limiting resistance unit. It includes a current control unit,
Further comprising an inductor on a current path between the main power line and the battery string,
A collective battery system including a fault current reduction circuit, wherein the sampling time interval of the current measuring unit is determined according to a time constant.
According to paragraph 1,
It further includes a current-limiting resistance switch unit connected in series with the current-limiting resistance unit to switch whether the fault current is conducted to the current-limiting resistance unit,
The fault current control unit controls the bypass switch unit and the current-limiting resistance switch unit based on the magnitude of the second sampling current measured by the current measurement unit at a predetermined sampling time interval and the current increase/decrease rate per sampling time compared to the first sampling current. A collective battery system including a fault current reduction circuit that is selectively controlled.
According to paragraph 2,
The fault current control unit is a set including a fault current reduction circuit, wherein the current limiting resistance switch unit is turned off when the magnitude of the third sampling current expected after the sampling time based on the current increase/decrease rate is greater than a predetermined risk value. battery system.
According to paragraph 1,
It further includes a current-limiting resistance switch unit connected in series with the current-limiting resistance unit to switch whether the fault current is conducted to the current-limiting resistance unit,
The fault current control unit updates the current increase/decrease rate based on the nth (hereinafter, n is an arbitrary natural number) sampling current of the current measurement unit, and n+1 expected after the sampling time based on the updated current increase/decrease rate. A collective battery system including a fault current reduction circuit, characterized in that turning off the current-limiting resistance switch unit when the magnitude of the second sampling current is greater than a predetermined critical value.
According to paragraph 4,
The fault current control unit is a battery system including a fault current reduction circuit, wherein the risk value is varied according to the sampling number n.
According to paragraph 1,
The fault current control unit updates the current increase/decrease rate based on the nth sampling current of the current measurement unit, and the size of the n+1th sampling current expected after the elapse of the sampling time is predetermined based on the updated current increase/decrease rate. A collective battery system including a fault current reduction circuit, characterized in that switching control of the bypass switch unit so that the current is not bypassed to the current limiting resistance unit when the value is lower than the value.
According to any one of claims 1 to 6,
A collective battery system including a fault current reduction circuit, wherein the bypass switch unit includes a bidirectional switch in which a pair of transistors are connected in parallel.
delete According to paragraph 1,
It further includes a current-limiting resistance switch unit connected in series with the current-limiting resistance unit to switch whether the fault current is conducted to the current-limiting resistance unit,
When the measured current of the current measuring unit is less than the normal range, the fault current control unit determines the size of the second sampling current measured by the current measuring unit at a predetermined sampling time interval and the current increase/decrease rate per sampling time compared to the first sampling current. A collective battery system including a fault current reduction circuit, characterized in that the current-limiting resistance switch unit is selectively blocked and controlled based on.

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