KR102532263B1 - Balancing devices for battery management systems - Google Patents

Abstract

The present invention relates to a balancing device of a battery management system, and relates to a balancing device of a battery management system for controlling energy transfer between batteries that do not share the same winding and are separated from each other and connected to the same position relative to the winding. In addition, the present invention provides a source battery cell including a source battery and a source switch for controlling discharge of the source battery in response to a source control signal; a source sub-battery cell including a source sub-battery and a source sub-switch for controlling discharging of the source sub-battery in response to a source sub-control signal; a target battery cell including a target battery and a target switch for controlling charging of the target battery in response to a target control signal; a target sub-battery cell including a target sub-battery and a target sub-switch for controlling charging of the target sub-battery in response to a target sub-control signal; and during a first period in which the source switch maintains an on state and the target sub switch maintains an on state and a second period in which the source switch maintains an on state and the target sub switch maintains an on state of the source switch A battery management system including a control circuit providing the source control signal for maintaining the on state, the target control signal for maintaining the on state of the target switch, and the target sub control signal for maintaining the on state of the target sub switch A balancing device is provided.

Description

Balancing devices for battery management systems

The present invention relates to a balancing device of a battery management system, and more particularly, to a balancing device of a battery management system for controlling energy transfer between batteries that do not share the same winding and are separated from each other and connected to the same position relative to the winding.

Recently, technologies for efficiently using electric energy, such as an electric vehicle, a smart grid, or an energy storage system (ESS), are being developed.

In particular, with the spread of renewable energy, interest in energy storage systems that can maximize the efficiency of energy use and storage and quality of power as the core of the smart grid is increasing.

The energy storage system may include a large-capacity battery module having a number of battery cells, and is a technology for storing surplus power (surplus energy) in the power system to supply it when and where it is needed, and can optimize the quality and efficiency of power. refers to a system that has

A device for more efficiently and stably managing the battery module is a battery management system.

The battery management system may be connected to a plurality of battery cells, read a voltage value of each battery cell through an A/D converter (analog to digital converter), and then control charging or discharging of the battery cells.

When a plurality of batteries are connected and used as one battery module, a voltage difference may occur between the batteries due to chemical differences, physical property differences, or use period differences of the batteries constituting the battery module.

Since the life span of the battery module may be shortened due to the voltage difference between the batteries, a problem in that the entire packaged battery module must be replaced with a new battery module may occur due to performance degradation such as a voltage drop of one single cell (single battery cell). can

Therefore, when charging or discharging large-capacity batteries used in energy storage systems (ESSs) and electric vehicles, a cell balancing process by a battery management system may be required to maintain the same voltage of each battery cell.

As balancing between batteries, a passive balancing method and an active balancing method may be suggested.

A passive balancing method can be achieved by removing an excess of a battery having more energy than other batteries through a resistor or the like.

However, there is a problem in that heat generated in the process of removing excess energy may cause other problems in the battery module, and energy consumption is severe in the balancing process.

On the other hand, the active balancing method may be performed by transferring energy of a battery having more energy than other batteries to a battery having less energy.

Since the active balancing method can be performed by arranging switches in battery cells and controlling each switch, there is an advantage in that energy is wasted less than the passive balancing method.

Meanwhile, in a cell balancing circuit in which one winding per two battery cells is shared and used, there are conventionally two types of methods for transferring energy between battery cells.

One is a method of transferring energy between adjacent cells (buck-boost method). This is used when energy is transferred between two adjacent cells sharing one winding.

Another is to transfer energy between distant cells that do not share the same winding. However, at this time, energy is transferred only between cells connected to different positions relative to the winding (flyback method).

If there is a need to transfer energy between cells that are separated from each other because they do not share the same winding and are connected to the same position relative to the winding, the two methods described above must be used sequentially. In this case, when energy is transferred, one more battery cell is passed through, and a balancing circuit is further operated, so that energy transfer efficiency and transfer speed are reduced.

Xu, S. Li, C. Mi, Z. Chen, and B. Cao, "SOC Based Battery Cell Balancing with a Novel Topology and Reduced Component Count," Energies, vol. 6, p. 2726, 2013.

The present invention was invented to solve the above conventional problems, to provide a balancing device of a battery management system for controlling energy transfer between batteries that do not share the same winding and are separated from each other and connected to the same position relative to the winding there is.

One aspect of the apparatus of the present invention includes a source battery cell including a source battery and a source switch for controlling discharge of the source battery in response to a source control signal; a source sub-battery cell including a source sub-battery and a source sub-switch for controlling discharging of the source sub-battery in response to a source sub-control signal; a target battery cell including a target battery and a target switch for controlling charging of the target battery in response to a target control signal; a target sub-battery cell including a target sub-battery and a target sub-switch for controlling charging of the target sub-battery in response to a target sub-control signal; and during a first period in which the source switch maintains an on state and the target sub switch maintains an on state and a second period in which the source switch maintains an on state and the target sub switch maintains an on state of the source switch and a control circuit providing the source control signal for maintaining the on state, the target control signal for maintaining the on state of the target switch, and the target sub control signal for maintaining the on state of the target sub switch.

In addition, the source battery and the source sub-battery of one aspect of the device of the present invention are directly connected and share a source winding, and the target battery and the target sub-battery are directly connected and share a target winding.

In addition, the control circuit of one aspect of the device of the present invention turns on the source switch and the target sub-switch during the first period so that the source winding and the target winding are magnetically coupled.

In addition, the control circuit of one aspect of the device of the present invention maintains the source switch in the on state during the second period, turns off the target sub switch and turns on the target switch so that the current discharged from the source battery is to be delivered to the target battery.

In addition, the control circuit of one aspect of the apparatus of the present invention turns off the target sub-switch during the second period and turns on the target switch after the dead time has elapsed.

In addition, the control circuit of one aspect of the device of the present invention turns off the source switch and the target switch during the third period.

In addition, the control circuit of one aspect of the device of the present invention turns off both the source switch and the target switch during the fourth period until the first current becomes zero after the second current becomes zero. It allows current to flow while charging the source sub-battery.

The present invention as described above relates to a control method in the case where energy must be transferred between batteries that are separated from each other and connected to the same location compared to the windings because they do not share the same winding in a balancing circuit, and energy transfer efficiency is achieved by directly transferring energy between batteries can increase

In addition, the present invention relates to a control method in a case where energy must be transferred between batteries that are separated from each other and connected to the same location compared to the windings because they do not share the same winding in a balancing circuit, and by directly transferring energy between batteries, the energy transfer rate is increased. can be raised

The accompanying drawings, which are included as part of the detailed description to aid understanding of the present invention, provide examples of the present invention and explain the technical idea of the present invention together with the detailed description.
1 is a configuration diagram illustrating a balancing device of a battery management system according to an embodiment of the present invention.
FIG. 2 is a circuit diagram showing in more detail battery cells of some of the balancing devices of the battery management system according to the embodiment of FIG. 1 and a control circuit for controlling the corresponding battery cells.
3 to 6 are diagrams illustrating current changes of a balancing device of a battery management system operating according to an embodiment of the present invention.
FIG. 7 is a diagram illustrating a current change according to FIGS. 3 to 6 and a corresponding voltage change.

The present invention can apply various transformations and can have various embodiments. Hereinafter, specific embodiments will be described in detail based on the accompanying drawings.

The following examples are provided to facilitate a comprehensive understanding of the methods, apparatus and/or systems described herein. However, this is only an example and the present invention is not limited thereto.

In describing the embodiments of the present invention, if it is determined that the detailed description of the known technology related to the present invention may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted. In addition, terms to be described later are terms defined in consideration of functions in the present invention, which may vary according to the intention or custom of a user or operator. Therefore, the definition should be made based on the contents throughout this specification. Terms used in the detailed description are only for describing the embodiments of the present invention, and should not be limiting. Unless expressly used otherwise, singular forms of expression include plural forms. In this description, expressions such as "comprising" or "comprising" are intended to indicate any characteristic, number, step, operation, element, portion or combination thereof, one or more other than those described. It should not be construed to exclude the existence or possibility of any other feature, number, step, operation, element, part or combination thereof.

In addition, terms such as first and second may be used to describe various components, but the components are not limited by the terms, and the terms are used for the purpose of distinguishing one component from another. used only as

Hereinafter, embodiments illustrating a battery management system according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a configuration diagram illustrating a balancing device of a battery management system according to an embodiment of the present invention.

Referring to FIG. 1 , a balancing device of a battery management system may include a plurality of battery cells and a control circuit 300 generating control signals for controlling each battery cell.

In more detail, the balancing device of the battery management system includes a battery string 100 connected in series and a balancing circuit 200 for balancing each battery constituting the battery string 100 and a balancing circuit 200 It may include a control circuit 300 that generates a control signal for controlling the operation.

The balancing circuit 200 may include switches corresponding to respective batteries in order to control the batteries constituting the battery string 100 . Here, a battery cell may be understood as a unit including one battery and a switch directly connected to the battery. The balancing circuit 200 may include windings arranged to transfer energy between each battery cell and a core connected to each winding.

The control circuit 300 measures or detects various states of the batteries constituting the battery string 100, and measures the temperature of the battery module, the ambient temperature of the battery module, the voltage of the battery module, and the discharge (or charge) current of the battery module. (or the value obtained by multiplying the rated capacity (Ah) of the battery module by the C-rate (current rate)), etc., it is possible to control for battery protection, inform the operator of the battery condition, and place the battery module in an appropriate state. It can have the function of managing with .

The control circuit 300 measures the voltage, current, and temperature of each battery cell to calculate cell balancing and SOC (State of Charge), and to ensure safety, charging, and energy storage system (ESS). Alternatively, discharge can be controlled.

To this end, the control circuit 300 includes a measurement unit for measuring the open circuit voltage of each battery cell, and an open circuit voltage higher than the reference voltage for energy balancing between battery cells according to the measurement result of the measurement unit. A controller that determines a battery cell as a source battery cell and determines a battery cell having an open-circuit voltage lower than the reference voltage as a target battery cell and provides a control signal so that energy is transferred from the source battery cell to the target battery cell, and the control signal generated by the controller A gate driving circuit for generating a gate signal for turning on or off the switch may be included.

Here, the reference voltage may be set in various ways according to a designer of a balancing device of a battery management system or a balancing method. The source battery may mean a battery that supplies energy according to the determination of the control circuit 300, and the target battery may mean a battery that receives the energy from the source battery according to the determination of the control circuit 300.

A battery cell including a source battery and a source switch for controlling the source battery may be referred to as a source battery cell. Also, a battery cell including a target battery and a target switch for controlling the target battery may be referred to as a target battery cell.

Also, the source sub battery may refer to a battery directly connected to the source battery and share a source winding, and the target sub battery may refer to a battery directly connected to the target battery and sharing a target winding.

A battery cell including a source sub-battery and a source sub-switch for controlling the source sub-battery may be referred to as a source sub-battery cell. Also, a battery cell including a target sub-battery and a target sub-switch for controlling the target sub-battery may be referred to as a target sub-battery cell.

Since the source battery, the source sub-battery, the target battery, and the target sub-battery may refer to various batteries of the battery string 100, they will be described below as first to fourth batteries. In addition, the source switch, the source sub-switch, the target switch, and the target sub-switch may also be described as first to fourth switches, etc., and a source battery cell including them, a source sub-battery cell, a target battery cell, and a target sub-switch. Battery cells may also be described as first to fourth battery cells.

FIG. 2 is a circuit diagram showing battery cells of some of the balancing devices of the battery management system according to the embodiment of FIG. 1 and a control circuit 300 for controlling the corresponding battery cells in more detail.

Referring to FIG. 2 , the balancing device of the battery management system may include a battery string 100 , a balancing circuit 200 and a control circuit 300 .

2 is a circuit diagram illustrating battery cells of some of the balancing devices of the battery management system. Referring to FIG. 2 , it can be seen that one battery cell is constituted by including one battery, a switch connected to the battery in parallel, and a winding connected to the battery and the switch.

The balancing device of the battery management system includes a battery string 100 and a balancing circuit 200 in which the battery cell units are continuously disposed when two battery cells paired to share the same winding are considered as one unit, It can be seen that it includes a control circuit 300 that provides a control signal for controlling each battery cell.

To balance the voltages of the battery cells, the control circuit 300 may transfer current from a battery cell having a high battery voltage to a battery cell having a low battery voltage.

2 illustrates and expresses arbitrary four battery cells (CELL1 to CELL4) among a plurality of battery cells constituting the balancing device of the battery management system.

Referring to FIG. 2 , a first battery cell CELL1 and a second battery cell CELL2 are disposed adjacent to each other to share a first winding L1, and a third battery cell CELL3 and a fourth battery cell CELL4 It can be seen that is disposed adjacent to share the second winding (L2). The second battery cell CELL2 and the third battery cell CELL3 may be disposed adjacent to each other, or may be disposed such that one or more other battery cell units are included therebetween.

In more detail, the battery string 100 of the balancing device of the battery management system may include a plurality of batteries C1, C2, C3, and C4, and the balancing circuit 200 for energy balancing between the batteries It may include a switch and windings (L1, S1, S2, L2, S3, S4).

2, the first battery cell CELL1 may include a first battery C1, a first switch S1, and a first winding L1, and the second battery cell CELL2 may include a second battery C2. ), a second switch S2 and a first winding L1.

The first battery cell CELL1 and the second battery cell CELL2 may be disposed adjacent to each other. The first battery C1 and the second battery C2 may be disposed adjacent to each other with positive and negative poles having opposite polarities.

The first battery cell CELL1 and the second battery cell CELL2 may share the first winding L1. That is, one end of the first winding L1 is connected to both the first battery C1 and the second battery C2, and the other end of the first winding L1 is connected to the first switch S1 and the second switch S2. ) can all be connected.

As described above, only the polarity of the batteries connected to one end of the first winding L1 that the first battery cell CELL1 and the second battery cell CELL2 share are different, and other configurations may be the same.

In addition, as described above, since two battery cells adjacent to each other are continuously arranged, an even number of battery cells included in the balancing device of the battery management system may be configured.

The third battery cell CELL3 of FIG. 2 may include a third battery C3, a third switch S3 and a second winding L2 in the same manner as the first battery cell CELL1 described above. 4 Battery cell CELL4 also includes a fourth battery C4 and a fourth switch S4 like the above-described second battery cell CELL2, and a second winding shared with the third battery cell CELL3. (L2) may be included.

The number of battery cells included in the balancing device of the battery management system may be variously set according to a designer's intention or the level of voltage required by a system requiring a balancing device of the corresponding battery management system.

Hereinafter, the first battery cell CELL1 and the second battery cell CELL2 may be understood as any two battery cells in a balancing device of a battery management system that share a first winding L1 and are adjacent to each other, and a third battery cell. (CELL3) and the fourth battery cell (CELL4) share the second winding (L2) and can be understood as any two battery cells in the balancing device of the adjacent battery management system.

A more detailed configuration of the battery cells is as follows.

The first to fourth batteries C1 to C4 may be any of the batteries constituting the battery string 100, of which the first battery C1 and the second battery C2 are directly connected to each other, , the third battery C3 and the fourth battery C4 may be directly connected to each other.

The first to fourth switches S1 to S4 are switches for controlling charging or discharging of batteries C1 to C4 included in corresponding battery cells CELL1 to CELL4 . The first to fourth switches S1 to S4 are various switches for switching the flow of current, and examples thereof include a bipolar junction transistor (BJT), a metal oxide semiconductor (MOSFET), and an insulated gate bipolar transistor (IGBT).

The first switch S1 may be turned on or turned off in response to the first control signal CON1 provided from the control circuit 300, and the second switch S2 may be provided from the control circuit 300. The third switch S3 is turned on in response to the third control signal CON3 provided from the control circuit 300. Alternatively, it may be turned off, and the fourth switch S4 may be turned on or off in response to the fourth control signal CON4 provided from the control circuit 300 .

The first winding L1 and the second winding L2 may be connected to one core or different cores to transfer energy.

The first winding L1 shared by the first battery cell CELL1 and the second battery cell CELL2 has a magnetizing inductance that shares magnetic flux with windings in the same core and magnetic flux of the first winding L1. Leakage inductance affected by may occur. Lm may mean magnetization inductance of the first winding L1 and windings sharing a core with the first winding L1, and Lleak1 may mean leakage inductance of the first winding L1.

Here, the leakage inductance may mean a value for a ratio indicating how much discharged energy is transferred to a cell to be charged. Also, the second winding L2 may be modeled by dividing the magnetization inductance Lm and the leakage inductance Lleak2.

Here, the leakage inductance refers to leakage inductance included in the multi-winding transformer itself, inductance on windings used for connection, or inductance additionally connected to a circuit.

For energy transfer between battery cells, a conventional buck boost method and a flyback method are known.

Buck boost type energy transfer can be used to transfer energy between battery cells sharing the same winding.

For example, in FIG. 2 , energy is transferred between the first battery C1 and the second battery C2 or when energy is transferred between the third battery C3 and the fourth battery C4.

In addition, a fly-back type of energy transfer may be used when energy is transferred between battery cells connected to different windings.

For example, in FIG. 2 , it is used to transfer energy between the first battery C1 and the fourth battery C4 or between the second battery C2 and the third battery C3.

When energy is to be transferred in the buck-boost method, the energy of the first battery C1 is transferred to the second battery C2 through the first winding L1 or the energy of the second battery C2 is transferred to the first winding ( It can be transferred to the first battery C1 through L1). In addition, the energy of the third battery C3 is transferred to the fourth battery C4 through the second winding L2 or the energy of the fourth battery C4 is transferred to the third battery C3 through the second winding L2. ) can also be passed.

If energy is to be transferred in a flyback method, the energy of the first battery (C1) is transferred to the fourth battery (C4) through the first winding (L1) and the second winding (L2) or to the second battery (C2). The energy of may be transferred to the third battery C3 through the first winding L1 and the second winding L2. In addition, the energy of the third battery C3 is transferred to the second battery C2 through the second winding L2 and the first winding L1, or the energy of the fourth battery C4 is transferred to the second winding L2. and may be transferred to the first battery C1 through the first winding L1.

On the other hand, unlike described above, when energy is transferred between different windings and batteries connected to the same location (upper side of all windings or lower side of all windings), there is no method of directly transferring energy according to the prior art. For example, when energy is transferred between the first battery (C1) and the third battery (C3) in FIG. 2 or between the second battery (C2) and the fourth battery (C4), energy is directly transferred. There was no method, and energy was delivered in the form of using the buck-boost method and the flyback method sequentially (or in reverse order).

As a result, in the process of energy transfer, the second battery C2 or the third battery C3 located in the middle is passed through once more, and the operation of the balancing circuit 200 increases, resulting in increased loss and reduced energy transfer efficiency. In addition, the time required for energy transfer is also increased.

The present invention relates to a control method in the case where energy must be transferred between batteries that are separated from each other and connected to the same location compared to the windings because they do not share the same winding in the balancing circuit 200, and is referred to as a forward method.

In the forward method, as shown in FIGS. 3 and 7, the control circuit 300 operates the first switch S1 and the fourth switch during the first period (from the start time point t0 to the first time point t1). By turning S4 on, the first current iL1 flows in the first winding L1 and the second current iL2 flows in the second winding L2, so that the first winding L1 and the second winding L2 ) to be magnetically coupled (t0-t1).

After that, as shown in FIGS. 4 and 7, the control circuit 300 turns off the fourth switch S4 during the second period (from the first time point t1 to the second time point t2) and turns off the third switch. (S3) is turned on. At this time, the first switch S1 is continuously turned on. Then, the current discharged from the first battery C1 is transferred to the third battery S3 (t1-t2).

Next, as shown in FIGS. 5 and 7, after the control circuit 300 turns on the first switch S1 and the third switch S3 during the set second period (t1-t2), the third During the period (from the second time point t2 to the third time point t3), both the first switch S1 and the third switch S3 are turned off.

At this time, when the first switch S1 is turned off, the first current iL1 flows to charge the second battery C2 and the third battery C3 until the second current iL2 becomes zero. ) flows in the form of charging (t2-t3).

At this time, referring to FIGS. 6 and 7 , the control circuit 300 operates the first switch S1 and the third switch S3 during the fourth period (from the third time point t3 to the fourth time point t4). ) are all turned off to allow current to flow while charging the second battery C2 until the first current iL1 becomes zero after the second current iL2 becomes zero (t3). -t4). Here, as shown in the drawing, during the fourth period, the second current iL2 is reduced to zero ( zero), the first current iL1 flows through the body diode (parasitic diode) of the second switch S2 (source sub switch) that is turned off, and the first current iL1 It is to use something that can charge the second battery C2 until it becomes zero.

On the other hand, when referring to FIGS. 3 and 7, it is ideal that the first switch S1 and the fourth switch S4 are simultaneously turned on at t0, but even if one of the two switches is turned on first with a slight time difference, does not exist.

4 and 7, it is ideal to turn on the third switch S3 as soon as the fourth switch S4 is turned off at t1, but if the third switch S3 and the fourth switch S4 are turned on at the same time, the third Since a short path is formed through the battery C3 and the fourth battery C4, it should be implemented to give some dead time for safety.

At this time, it does not matter if the first switch S1 is turned off and then turned on for a certain period of time at t1.

5 and 7, it is ideal to turn off the first switch S1 and the third switch S3 at t2 at the same time, but it does not matter if there is a slight time difference between turning off the two switches (it does not matter which one of them is turned off first does not exist.)

The present invention as described above relates to a control method in the case where energy must be transferred between batteries that are separated from each other and connected to the same location compared to the windings because they do not share the same winding in a balancing circuit, and energy transfer efficiency is achieved by directly transferring energy between batteries can increase

In addition, the present invention relates to a control method in a case where energy must be transferred between batteries that are separated from each other and connected to the same location compared to the windings because they do not share the same winding in a balancing circuit, and by directly transferring energy between batteries, the energy transfer rate is increased. can be raised

100: battery string 200: balancing circuit
300: control circuit

Claims (7)

a source battery cell including a source battery and a source switch for controlling discharging of the source battery in response to a source control signal;
a source sub-battery cell including a source sub-battery and a source sub-switch for controlling discharging of the source sub-battery in response to a source sub-control signal;
a target battery cell including a target battery and a target switch for controlling charging of the target battery in response to a target control signal;
a target sub-battery cell including a target sub-battery and a target sub-switch for controlling charging of the target sub-battery in response to a target sub-control signal; and
During a first period in which the source switch maintains an on state and the target sub switch maintains an on state and a second period in which the source switch maintains an on state and the target sub switch maintains an on state, the source switch A control circuit providing the source control signal for maintaining the on state, the target control signal for maintaining the on state of the target switch, and the target sub control signal for maintaining the on state of the target sub switch,
The source battery and the source sub-battery are directly connected and share a source winding, and the target battery and the target sub-battery are directly connected and share a target winding;
The control circuit turns on the source switch and the target sub-switch during the first period so that the source winding and the target winding are magnetically coupled, and turns on the source switch during the second period state, turn off the target sub switch, and turn on the target switch to control the current discharged from the source battery to be transferred to the target battery. delete delete delete According to claim 1,
The control circuit turns off the target sub-switch during the second period and turns on the target switch after a dead time has passed. According to claim 1,
The control circuit is a balancing device of a battery management system for turning off a source switch and a target switch during a third period after the second period. According to claim 6,
The control circuit turns off both the source switch and the target switch, and after the second current of the target winding flowing through the body diode of the target switch becomes zero, through the body diode of the source sub switch A balancing device of a battery management system that controls current to flow while charging the source sub-battery until the first current flowing in the source winding becomes zero.

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