KR20210039267A - Battery system and method for controlling battery system - Google Patents

Abstract

According to an embodiment of the present invention, provided is a battery system which can improve balancing efficiency. The battery system comprises: a battery module including a plurality of battery cells; a monitoring unit monitoring a parameter of each of the plurality of battery cells; and a control unit using the parameter to determine whether an abnormal battery cell exists in the battery module, and controlling to calculate a reference voltage for balancing the plurality of battery cells and to perform cell balancing to an equalization target region when it is determined that the abnormal battery cell exists.

Description

Battery system and battery system control method {BATTERY SYSTEM AND METHOD FOR CONTROLLING BATTERY SYSTEM}

The present disclosure relates to a battery system and a method of controlling the battery system.

Rechargeable or secondary batteries differ from primary batteries that provide only irreversible conversion of chemical substances into electrical energy in that charging and discharging can be repeated. Low-capacity rechargeable batteries are used as power supplies for small electronic devices such as mobile phones, notebook computers, and camcorders, and high-capacity rechargeable batteries are used as power supplies for hybrid vehicles and the like.

In general, a secondary battery includes an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, a case for accommodating the electrode assembly, and an electrode terminal electrically connected to the electrode assembly. In order to enable charging and discharging of the battery through an electrochemical reaction between the positive electrode, the negative electrode, and the electrolyte solution, an electrolyte solution is injected into the case. The shape of the case, such as a cylinder or a rectangle, depends on the application of the battery.

The rechargeable battery can be used as a battery module formed of a plurality of unit battery cells coupled in series and/or parallel to provide a high energy density, for example for driving a motor of a hybrid vehicle. That is, the battery module is formed by interconnecting electrode terminals of a plurality of unit battery cells according to the amount of power required to implement, for example, a high-power rechargeable battery for an electric vehicle. One or more battery modules are mechanically and electrically integrated to constitute a battery system, a thermal management system is mounted, and set up to communicate with one or more electrical consumers.

In order to meet the dynamic power demands of the various electrical consumers connected to the battery system, static control of battery power output and charging alone is not sufficient. Therefore, information must be exchanged steadily or intermittently between the battery system and the controllers of electricity consumers. This information includes the actual state of charge (SoC), potential electrical performance, charging capacity, and internal resistance of the battery system, as well as actual or predicted power demand or consumer surplus.

For monitoring, control, and/or setting of the above-described parameters, a battery management unit (BMU) and/or a battery management system (BMS) are included. This control unit may be an integral part of the battery system and may be disposed within a common housing or may be part of a remote control unit that communicates with the battery system via a suitable communication bus. The BMS/BMU is typically connected not only to each battery module in the battery system, but also to the controllers of one or more electricity consumers. Typically each battery module includes a cell supervision circuit (CSC) configured to maintain communication with a BMS/BMU and a different battery module. The CSC may be further configured to monitor the cell voltage of battery cells of some or each battery module and to actively or passively balance the voltage of individual battery cells within the module.

It is an object of the present invention to provide a battery system and a battery system control method that overcomes or reduces at least some of the disadvantages of the prior art and prevents invalid cell balancing.

It is also an object of the present invention to provide a battery system and a battery system control method that are balanced (top-balanced, mid-balanced, or bottom-balanced) in an equalization target region (a target equalization voltage region or an equalization target SoC region).

The battery system according to an embodiment determines whether there are abnormal battery cells in the battery module using a battery module including a plurality of battery cells, a monitoring unit monitoring parameters of each of the plurality of battery cells, and the parameters, and the battery module When it is determined that there are abnormal battery cells in the battery, a control unit that calculates a reference voltage for balancing the plurality of battery cells and controls to perform cell balancing to the equalization target region is included.

The abnormal battery cell is at least one of a weak cell, a high-impedance cell, and an internal short-circuit cell.

The equalization target area is one of a top-balancing area, a mid-balancing area, and a bottom-balancing area.

The control unit uses the state of charge (SoC) calculated at any two points in time to determine if there is an SoC shift cell in the battery module.

The control unit compares the voltage (OCV) measured in the dormant period before charging or discharging with the OCV measured in the dormant period after charging or discharging to determine if there is an SoC shift cell in the battery module.

The control unit uses the parameter to calculate the capacity of each of the plurality of battery cells, and compares the capacities to determine whether there is a weak cell in the battery module.

The control unit calculates a resistance value of each of the plurality of battery cells by using the parameter, and determines whether there is a high-impedance cell in the battery module by comparing the resistance values.

The control unit determines a minimum voltage cell other than the abnormal cell among the plurality of battery cells as the spare cell, and calculates a reference voltage by using the SoC difference between the spare cell and the abnormal cell in the equalization target area.

,

,

을 사용하여 기준 전압을 계산하고,

은 예비 셀의 SoC이며,

은 균등화 목표 영역에서의 최소 전압 셀의 SoC이고,

은 예비 셀의 전압이며,

는 기준 전압이다.The control unit is a formula,

,

,

Calculate the reference voltage using

Is the SoC of the spare cell,

Is the SoC of the minimum voltage cell in the equalization target region,

Is the voltage of the spare cell,

Is the reference voltage.

The control unit compensates the reference voltage according to the time when cell balancing is performed.

,

을 사용하여 기준 전압을 보상하고,

는 밸런싱 전류이고

는 셀 밸런싱이 수행된 시간이며,

는 셀 밸런싱의 듀티비이고,

은 배터리 모듈 내에 포함된 예비 셀의 용량이며, K는 상수이다.The control unit is a formula,

,

To compensate for the reference voltage,

Is the balancing current

Is the time when cell balancing was performed,

Is the duty ratio of cell balancing,

Is the capacity of the spare cell included in the battery module, and K is a constant.

A method for controlling a battery system according to an embodiment includes the steps of monitoring parameters of each of a plurality of battery cells included in the battery module, determining whether there are abnormal battery cells in the battery module using the parameters, and abnormal battery cells in the battery module. If it is determined that is present, calculating a reference voltage for balancing a plurality of battery cells, and performing cell balancing to an equalization target region using the reference voltage.

Determining whether there is an abnormal battery cell includes determining whether there is an SoC shift cell in the battery module using a state of charge (SoC) calculated at two arbitrary points in time.

The step of determining whether there is an abnormal battery cell is to compare the open circuit voltage (OCV) measured in the idle period before charging or discharging and the OCV measured in the idle period after charging or discharging, and the SoC shift cell in the battery module It includes determining if there is.

Determining whether there is an abnormal battery cell includes calculating a capacity of each of the plurality of battery cells by using a parameter, and determining whether there is a weak cell in the battery module by comparing the capacities.

Determining whether there is an abnormal battery cell includes calculating a resistance value of each of the plurality of battery cells using a parameter, and determining whether a high-impedance cell exists in the battery module by comparing the resistance values.

The calculating of the reference voltage includes determining a minimum voltage cell other than the abnormal cell among the plurality of battery cells as a spare cell, and calculating the reference voltage using the SoC difference between the spare cell and the abnormal cell in the equalization target area. Includes steps.

It further includes compensating the reference voltage according to the time when the cell balancing is performed.

The abnormal battery cell is at least one of a weak cell, a high-impedance cell, and an internal short-circuit cell.

The equalization target area is one of a top-balancing area, a mid-balancing area, and a bottom-balancing area.

One or more disadvantages of the prior art can be avoided or at least reduced by the present invention.

According to the present invention, there is an effect of increasing the balancing efficiency.

According to the present invention, there is an effect of maximizing the capacity of the battery delivered to the load.

Features will become apparent to those skilled in the art by describing exemplary embodiments in detail with reference to the accompanying drawings.
1 is an exemplary diagram showing cell banks in a battery module.
2 is an exemplary view showing a weak cell in a battery module.
3 is an exemplary view showing a state in which a battery module including a weak cell is balanced according to a conventional balancing method.
4 is a graph showing a cell imbalance state of a battery module including a weak cell.
5 is a block diagram showing a battery system according to an embodiment.
6 is a flowchart illustrating a method of controlling a battery system according to an exemplary embodiment.
FIG. 7 is a flow chart specifically showing an example of an abnormal cell diagnosis step of FIG. 6.
8 are graphs showing cell voltage changes of an SoC shift cell.
9 are graphs showing a change in cell voltage of a weak cell.
10 are graphs showing cell voltage changes of a high-impedance cell.
11 is a flow chart specifically showing an example of the SoC shift cell determination step of FIG. 7.
12 is a graph showing voltage changes for each section of a battery cell.
13 is a graph showing the SoC of the SoC shift cell.
14 is a flow chart specifically showing an example of a cell balancing standard and target setting step of FIG. 6.
15 is a graph illustrating a case in which the minimum voltage cell is an abnormal cell at the end of charging.
16 is a flow chart specifically showing an example of a cell balancing step of FIG. 6.
17 is a graph illustrating a case of compensating a voltage of a virtual reference cell when cell balancing is performed.
18 is a graph showing an example of a reference cell voltage calculated when cell balancing is performed.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Hereinafter, operating effects according to embodiments of the present invention and a method of implementing the same will be described with reference to the accompanying drawings. In the drawings, the same reference numerals denote the same elements, and redundant descriptions are omitted. However, the present invention may be embodied in various forms, and should not be construed as being limited only to the embodiments shown here. Rather, these embodiments are provided by way of example so that the present disclosure may be thorough and complete, and will fully convey aspects and features of the present invention to those skilled in the art.

Accordingly, processes, elements, and techniques that are deemed not necessary to a person skilled in the art for a thorough understanding of aspects and features of the present invention may not be described. In the drawings, the relative sizes of devices, layers, and regions may be exaggerated for clarity.

As used herein, the term “and/or” includes any and all combinations of one or more associated and listed items. Also, the use of "can" when describing embodiments of the present invention means "one or more embodiments of the present invention." In the following description of the embodiments of the present invention, terms in the singular form may include the plural form unless the context clearly indicates different.

The terms “first” and “second” are used to describe various elements, but it will be understood that these elements should not be limited by these terms. This term is only used to distinguish one element from another. For example, a first element may be referred to as a second element, and likewise, a second element may be referred to as a first element without departing from the scope of the present invention. As used herein, the term “and/or” includes any and all combinations of one or more related and listed items. An expression such as "at least one" modifies the entire list of elements, prior to the list of elements, and does not modify individual elements of the list.

The terms "substantially", "about" and similar terms used herein are used as terms of approximation and are not used as terms of degree, and measured values or calculations that can be recognized by those of ordinary skill in the art. It is intended to account for the intrinsic deviation of the values. Further, when the term “substantially” is used in combination with a feature that can be expressed using a number, the term “substantial” denotes a range of +/-5% of the value centered on that value.

1 is an exemplary diagram showing cell banks in a battery module. In the battery module 10, the cell banks B1, B2, and B3 are connected in series. As shown in (a) of Figure 1, one bank (B1) may include one battery cell 100, or as shown in Figure 1 (b) and (c), one The banks B2/B3 may include a plurality of battery cells 100 connected in parallel. In general, when a number of battery cells are connected in series or parallel, the voltage is measured and monitored based on the cells (or banks) connected in series.

It is ideal that the electrical characteristics such as voltage (SoC) and resistance of the battery cells are uniform.However, there may be manufacturing distribution, differences in deterioration occurring while using the battery, and battery cell abnormalities.Therefore, the voltage between battery cells (or banks) connected in series Or there is a difference in state of charge (SoC). A state in which the voltage or the state of charge (SoC) between the battery cells (or banks) connected in series as described above is not equal is referred to as a cell imbalance state. If there is a cell imbalance, the usable capacity of the battery decreases, the possibility of the cell being overcharged increases, and this may cause a problem of accelerating deterioration. Therefore, cell balancing is to make the cell voltage or the state of charge (SoC) uniform in such a cell unbalance state, and is important for stable operation of the battery.

Cell balancing is performed to equalize the voltage or the state of charge (SoC) of the battery cells (or banks) connected in series when the voltage or the state of charge (SoC) is not equal, that is, when a cell imbalance exists. As a first method, passive balancing is a method of balancing by consuming energy of a cell having a high voltage or state of charge (SoC). As a method of consuming energy, it is common to discharge the cell through a resistor. As a second method, active balancing transfers the energy of a cell with a high voltage or state of charge (SoC) to a cell with a low voltage or state of charge (SoC) to determine the voltage or state of charge (SoC) between the two cells. It is to equalize. Active balancing is ideal in terms of transferring energy to other cells (or banks) without consuming energy, but it requires many parts, which increases manufacturing cost, and it is difficult to control active balancing. Therefore, in general, passive balancing is mainly used.

In order to perform cell balancing by passive balancing, it is necessary to determine which cell (or bank) energy should be consumed. For example, which cells (or banks) should be discharged, which cells (or banks) should be equalized based on voltage or state of charge (SoC), and when to perform cell balancing should be determined. . In addition, if there is a difference in capacity of the cells (or banks), even if cell balancing is performed, imbalance may occur in any voltage or any state of charge (SoC) region, so that any voltage or state of charge (SoC) region (leveling target region Or to be equalized at the point). This can be called a cell balancing strategy.

If the cell balancing strategy is too simple or if the cause of the cell imbalance is not taken into account in the cell balancing strategy, it may result in a different cell balancing operation than intended, that is, invalid cell balancing. Invalid cell balancing means that the cell balancing performed to equalize the voltage or state of charge (SoC) of the cells (or banks) connected in series acts in a direction opposite to equalization as a result.

For example, when a weak cell (or bank) exists in the battery module 10, invalid cell balancing may occur. This will be described with reference to FIGS. 2 to 4.

FIG. 2 is an exemplary view showing a weak cell in a battery module, FIG. 3 is an exemplary view showing a state in which a battery module including a weak cell is balanced according to a conventional balancing method, and FIG. 4 is a battery module including a weak cell It is a graph showing the cell imbalance state of.

As shown in FIG. 2, the weak cell is a cell 100b (or bank) that is significantly smaller than the cells (or banks) 100a, 100c, and 100d with different capacities among the cells (or banks) connected in series. to be.

As shown in (a) of FIG. 3, since the voltage of the weak cell 100b is the minimum voltage in the low voltage region, cell balancing is performed on the other cells 100a, 100c, and 100d, and the weak cell 100b The voltage of must be equalized to the target voltage.

As shown in (b) of FIG. 3, since the cell voltage is equalized in the intermediate voltage region, cell balancing is not performed.

As shown in (c) of FIG. 3, since the voltage of the cell 100d is the minimum voltage in the high voltage region, cell balancing must be performed on the cells 100a, 100c, and 100b.

As shown in (a) of FIG. 4, if aiming for top balancing in a high voltage region such that the voltage is equalized in a high region, a weak cell ( Cell balancing performed based on the voltage of 100b) may lead to cell imbalance in the medium voltage region and the high voltage region. Therefore, performing cell balancing in a low voltage region results in cell imbalance, contrary to the intention to equalize in a high voltage region, resulting in invalid cell balancing.

As shown in (b) of FIG. 4, in the low voltage region, the voltage of the weak cell 100b becomes the minimum voltage, and when cell balancing is performed based on this, cells 100a, 100c, and other cells 100a, 100c, and other cells 100a, 100c, and The difference in capacity between 100d) results in an enlarged cell imbalance in the high voltage region. As a method for preventing such invalid cell balancing, the voltage for starting cell balancing can be increased. In this case, regardless of the presence or absence of a weak cell, the voltage range in which cell balancing is operated decreases, and the time during which cell balancing can be performed during charging decreases, and thus cell balancing efficiency is deteriorated.

In order to prevent such invalid cell balancing, increase cell balancing efficiency, and provide a balanced (eg, top-balanced) state in the equalization target voltage region, the battery system and the battery system control method of the present disclosure are abnormal. Cell is diagnosed and cell balancing is performed based on a virtual reference cell voltage (or SoC).

5 is a block diagram showing a battery system according to an embodiment. As shown, the battery system includes a battery module 10, a balancing unit 20, a monitoring unit 30, a control unit 40, and a memory unit 50.

The battery module 10 includes a plurality of unit battery cells 100 coupled in series and/or in parallel. The battery module 10 includes a plurality of cell banks 110a, 110b, 110c, and 100n connected in series.

The balancing unit includes a plurality of balancing circuits 120 connected in parallel to each of the cell banks 110a, 110b, 110c, and 100n. Each of the balancing circuits 120 may include a balancing resistor (not shown) and a balancing switching element (not shown). The balancing circuit 120 operates by a signal transmitted from the outside of the balancing unit 20 to lower the voltage of the cells or banks connected in parallel.

The monitoring unit 30 is connected to the cell banks 110a, 110b, 110c, and 100n to detect voltages of each of the cell banks 110a, 110b, 110c, and 100n. Meanwhile, in FIG. 5, a case in which each of the cell banks 110a, 110b, 110c, and 100n connected to the monitoring unit 30 includes a plurality of cells connected in parallel with each other is illustrated as an example, but the present invention is limited thereto. Since it is not, one cell bank may include only one cell, as described with reference to FIG. 1.

In addition, the monitoring unit 30 may detect current flowing through the cell banks 110a, 110b, 110c, and 100n, and the temperature of each of the cell banks 110a, 110b, 110c, and 100n.

The control unit 40 receives information on parameters such as voltage, current, and temperature detected from the monitoring unit 30, and based on this, the state of charge (SoC) of each bank and the state of health (SoH) of each bank. ), the state of the battery such as the state of power (SoP) of each bank can be calculated.

In addition, the control unit 40 may calculate the remaining capacity of each of the cell banks 110a, 110b, 110c, and 100n using at least an open circuit voltage (OCV), SoH, and SoC. Additionally, the control unit 40 may predict the current capacity of each of the cell banks 110a, 110b, 110c, and 100n by considering the temperature of each of the cell banks 110a, 110b, 110c, and 100n.

The control unit 40 may diagnose abnormal cells using parameters such as voltage, current, and temperature detected from the monitoring unit 30 and battery status information such as SoC and capacity. For example, the control unit 40 may determine an abnormal cell bank (or cell), and also determine the type of imbalance of the abnormal cell bank (or cell).

The control unit 40 may set cell balancing criteria and targets according to the presence or absence of abnormal cells, abnormal types of abnormal cells, and the like. The control unit 40 may transmit a control signal to the balancing unit 20 so that cell balancing is performed according to a set reference and target.

The control unit 40 may be a battery management unit (BMU) and/or a battery management system (BMS), and the balancing unit 20 and the monitoring unit 30 may be a cell monitoring circuit ( CSC: may be a cell supervision circuit.

The memory unit 50 includes information on parameters such as voltage, current, and temperature obtained from the monitoring unit 30, a state of charge (SoC) of each bank calculated by the control unit 40, and a state of SoH (state) of each bank. of health), battery state information such as a state of power (SoP) of each bank, and diagnostic information of each bank determined by the control unit 40 may be stored. The diagnostic information may be information determined by the control unit 40 based on at least one of parameter and state information. For example, when a parameter such as a voltage value is obtained in the idle period, the control unit 40 calculates and compares the charging state (SoC) of each bank based on the voltage value, and banks with different charging state (SoC) Information on a lower bank than may be stored in the memory unit 50. Thereafter, when charging is performed and a voltage value is obtained again in the idle period, the control unit 40 calculates and compares the charging state (SoC) of each bank based on the voltage value again, and the charging state after charging (SoC) Is a lower bank than other banks and a bank having a lower charge state (SoC) before charging (SoC) stored in the memory unit 50 is identical to that of the other banks, and the corresponding bank is referred to as a Soc shift bank (cell). You can decide.

A method of controlling the battery system will be described with reference to FIG. 6.

6 is a flowchart illustrating a method of controlling a battery system according to an exemplary embodiment. As shown, the control unit 40 diagnoses an abnormal cell (or bank) (S10). The types of abnormal cells include SoC shift cells, weak cells, and high-impedance cells. The control unit 40 determines an abnormal cell bank (or cell) using parameters such as voltage, current, and temperature detected from the monitoring unit 30 and battery status information such as SoC and capacity, and determines the abnormal cell bank. The type of abnormality of (or cell) can also be determined.

The control unit 40 may detect abnormal cells using a statistical method or machine learning for the SoC of each cell, a capacity, a voltage increase rate according to an increase in capacity, and a battery resistance.

The control unit 40 will be described with reference to FIGS. 7 to 10 with respect to the step of diagnosing an abnormal cell (or bank).

7 is a flow chart specifically showing an example of the abnormal cell diagnosis step of FIG. 6, FIG. 8 is a graph showing a change in cell voltage of an SoC shift cell, and FIG. 9 is a graph showing a change in cell voltage of a weak cell, and FIG. 10 Are graphs showing cell voltage change of a high-impedance cell.

As shown in FIG. 7, the control unit 40 determines an SoC shift cell (S100), a weak cell (S110), and a high-impedance cell (S120).

First, in the SoC shift cell, the capacity of the cell (or bank) has a similar value due to the difference in self-discharge between cells (or banks), capacity distribution, capacity fluctuation, cell abnormality, etc., but different cells (or banks) ), the SoC may be higher or lower than that of the cells (or banks).

Referring to FIG. 8, (a) of FIG. 8 shows a graph of voltage values when the battery module 10 is balanced in a high voltage region. In both the high voltage region and the low voltage region, the voltage values of the cells (or banks) included in the battery module 10 have similar values.

8B and 8C show graphs of voltage values when there is a cell in which SoC shift exists. If there is an SoC shift, a balancing operation can be performed based on a minimum voltage cell like a conventional cell balancing, and a range of a voltage at which the cell balancing operates can be set widely from a low voltage to a high voltage.

Next, the weak cell may be a cell (or bank) having a lower capacity than other cells (or banks) due to an aging difference between cells (or banks), cell abnormalities, and the like.

Referring to FIG. 9, (a) of FIG. 9 shows a balancing state in which a battery module including a weak cell is equalized in a high voltage region. In (a) of FIG. 9, a cell imbalance state appears in the low voltage region and the medium voltage region, but when equalization in the high voltage region is the goal of balancing, it is equalized in the high voltage region to achieve the goal of balancing, so additional cell balancing is performed. There is no need to do it.

9B and 9C show a balancing state in a low voltage region that is equalized in a low voltage region in a low voltage region (bottom balanced) and a balancing in a middle voltage region that is equalized in a medium voltage region. Indicates the state. When equalization in the high voltage region is the goal of balancing, it is necessary to perform additional cell balancing to reach a state as shown in (a) of FIG. 9.

Next, the high-impedance cell is a cell with a higher internal impedance or equivalent resistance compared to other cells (or banks) due to connection problems between cells (or banks), deterioration differences, cell abnormalities, etc. Bank).

Referring to FIG. 10, (a) of FIG. 10 shows a balancing state in a high voltage region equalized in a high voltage region in a battery module including a high-impedance cell. In (a) of FIG. 10, a cell imbalance state appears in the low voltage region and the medium voltage region, but when equalization in the high voltage region is the goal of balancing, it is equalized in the high voltage region to achieve the balancing goal, so additional cell balancing is performed. no need.

10B and 10C illustrate a case where the SoC of the high-impedance cell is moved upward and the SoC of the high-impedance cell is moved downward, respectively. When equalization in the high voltage region is the goal of balancing, it is necessary to perform additional cell balancing to reach a state as shown in FIG. 10A.

Next, the control unit 40 sets a reference voltage for cell balancing and a target for cell balancing (S20). The control unit 40 may set a reference voltage for cell balancing and a target for cell balancing in consideration of the presence or absence of the abnormal cell and the abnormal type of the abnormal cell. For example, if a weak cell and a high-impedance cell are present in the battery module 10, the control unit 40 is a weak cell and a high-impedance cell, even if the weak cell and the high-impedance cell are cells having the minimum voltage. May not be set as the reference cell for cell balancing. In this case, the control unit 40 may set a virtual reference cell and perform cell balancing by comparing voltages between other cells and the virtual reference cell.

Next, the control unit 40 performs cell balancing (S30). The control unit 40 may generate a control signal so that a voltage of a cell to be subjected to cell balancing is lowered by the balancing circuit 120 and supply it to the balancing unit 20.

A method for controlling such a battery system will be described in detail with reference to the following drawings.

First, a method of determining the SoC shift cell by the control unit 40 will be described with reference to FIGS. 11 to 13.

11 is a flow chart specifically showing an example of the SoC shift cell determination step of FIG. 7, FIG. 12 is a graph showing voltage changes for each section of a battery cell, and FIG. 13 is a graph showing the SoC of the SoC shift cell.

Referring to FIG. 11, the control unit 40 calculates the SoC of each cell based on the voltage value obtained in the first idle period (S101). For example, the control unit 40 may calculate the SoC of each cell in section A of FIG. 12.

Next, the control unit 40 determines whether charging or discharging is performed (S103).

If it is determined that charging or discharging has been performed, the control unit 40 calculates the SoC of each cell based on the voltage value obtained in the second idle period (S105). For example, the control unit 40 may calculate the SoC of each cell in section C of FIG. 12.

Alternatively, if the control unit 40 can predict the SOC of each cell in real time, the two separated by charging or discharging a certain amount or more for each cell (or bank) without performing the steps (S101, S103, S105). It is also possible to obtain two SOC values. For example, the control unit 40 may use the SoC of each cell (or bank) predicted by the BMU or BMS.

Next, the control unit 40 calculates the SoC deviation of each cell by using the SoC calculated in step S101 and the SoC calculated in step S105 (S107). For example, referring to FIG. 13, SoC distribution of each of the banks is shown.

The control unit 40 determines a bank (or cell) having an exceptional SoC as an SoC shift cell (S109). For example, the control unit 40 determines a bank (or cell) having an SoC higher by a predetermined value compared to other cells as the SoC shift cell in which the SoC is moved upward, and has a SoC lower by a predetermined value than other cells. The bank (or cell) can be determined as the SoC shift cell in which the SoC has been moved up or down. That is, a cell with a remarkably higher SOC compared to an average cell is shifted high, and a cell with a remarkably low SOC is shifted low.

Using the SoC of each cell measured at two arbitrary points in time, if the SoC of a certain cell is higher than the average or median value of the SoC of all the cells by a predetermined value or more, the control unit 40 transfers the corresponding cell to the cell in which the SoC shift has occurred. Can be determined as. For example, in two SoC data (the SoC calculated in step S101 and the SoC calculated in step S105) separated by charging or discharging a certain amount or more, the control unit 40 If it is higher or lower than the SoC of the predetermined value, it may be determined that the corresponding cell is a cell in which the SoC shift has occurred.

In addition, when the SoC of each cell cannot be calculated, the control unit 40 may determine the SoC shift cell by using the OCV acquired in the idle period. For example, the control unit 40 may determine a bank (or cell) having an abnormal ΔOCV value as an SoC shift cell by substituting the SoC with an OCV value in the above steps (S101 to S109).

In addition, the control unit 40 may calculate the capacity of each cell, and use this to determine the weak cell. The control unit 40 may calculate the current capacity of each of the cell banks using at least OCV, SoH, SoC, and the like, and may determine a cell that is smaller by a predetermined capacity value or more than other cells as a weak cell.

Alternatively, the control unit 40 may determine the weak cell using the charge/discharge characteristic without using the capacity. Since the weak cell has a small capacity, the rate of change in voltage with respect to capacity increase or decrease is greater than that of an average cell (or bank). In the case of charging, for example, a weak cell has a larger voltage increase for the same charging capacity. The control unit 40 can determine a weak cell using such dV/dQ characteristics.

For example, in the case of a weak cell, since the voltage change amount (ΔV) is generally larger than that of other cells, the control unit 40 calculates the change amount (ΔV) of each cell voltage for a capacity change by ΔQ to generate the weak cell. Can be judged.

As another example, in the case of a weak cell, since the capacity change amount (ΔQ) is generally smaller than that of other cells in a fixed voltage period, the capacity change amount (ΔQ) for each cell is determined during the fixed voltage period [VA, VB] (ΔV). It is possible to calculate and determine the weak cell.

In addition, the control unit 40 may calculate an internal resistance value of each cell, and use this to determine a high-impedance cell and an internal short-circuit cell.

The control unit 40 may diagnose abnormal cells by measuring changes in voltage, current, and time of each cell in the idle period and the charging/discharging period, and calculating a change in capacity, and the like. In addition, parameters measured by the monitoring unit 30 and information calculated by the control unit 40 are recognized or classified by an outlier detection or machine learning algorithm. , The control unit 40 may detect an abnormal cell having significantly different parameters compared to other cells.

Next, a method of setting a reference voltage for performing cell balancing and a target for cell balancing will be described with reference to FIGS. 14 and 15.

14 is a flowchart illustrating an example of a cell balancing reference and target setting step of FIG. 6 in detail, and FIG. 15 is a graph illustrating a case in which the minimum voltage cell is an abnormal cell at the end of charging.

As shown, when the diagnosis of the abnormal cell is completed, the control unit 40 determines whether the battery module 10 is equalized in the equalization target area (S200). Here, it is described that the control unit 40 determines whether to balance in the high voltage region, but the control unit 40 may determine whether to balance in the low voltage region/medium voltage region according to the application or purpose of use, It is not limited thereto.

If the battery module 10 is determined to be in the equalization state in the high voltage region, since there is no need to perform cell balancing, the control unit 40 ends the cell balancing.

The control unit 40 determines whether there is an abnormal cell in the battery module 10 (S210).

When it is determined that there is an abnormal cell in the battery module 10, the control unit 40 determines whether there is a reference cell (S220). The reference cell is a cell serving as a reference for cell balancing, and balancing may be performed so that the voltage or SoC of another cell is the same/similar to the voltage or SoC of the reference cell.

The control unit 40 determines that there are no abnormal cells in the battery module 10, and there are abnormal cells in the battery module 10, but the control unit 40 has a minimum voltage in the equalization target area (for example, at the end of charging). If the cell is not an abnormal cell, that is, at least one of a weak cell, a high-impedance cell, and an internal short-circuit cell, the minimum voltage cell is determined as a reference cell (S230).

When it is determined that there is no reference cell, the control unit 40 determines the virtual cell as the reference cell (S240). If aiming for equalization in the high voltage region, the virtual cell can be calculated as follows.

First, the control unit 40 sets a reserved cell index (r) for a reference cell at a time of cut-off time. The control unit 40 uses the abnormal type information of the acquired abnormal cell in step S10 when setting the cell index.

이 되고, 여기서,

은 상기 예비 셀(예를 들어, 최소 전압 셀)의 SoC이며,

는 균등화 목표 셀(이 예에서는 최소 전압 셀)의 SoC이고,

은 최소 전압 셀의 SoC이다. 또한,

이 되며, 여기서,

는 가상 기준 셀의 ΔV이다. 정리하면,

이다. For example, when only SoC shift cells exist in the battery module 10, the control unit 40 sets the index of the cell having the minimum voltage at the end of charging as the spare cell index r. in this case

Becomes, where,

Is the SoC of the spare cell (e.g., the minimum voltage cell),

Is the SoC of the equalization target cell (minimum voltage cell in this example),

Is the SoC of the minimum voltage cell. Also,

Becomes, where,

Is the ΔV of the virtual reference cell. In short,

to be.

That is, when only the SoC shift cell exists in the battery module 10, the control unit 40 performs cell balancing based on the voltage of the cell having the minimum voltage at the end of charging.

As another example, as shown in FIG. 15, when at least one of a weak cell, a high-impedance cell, and an internal short cell exists in the battery module 10, a method of determining a virtual reference cell will be described.

)은 다음의 수학식 1 내지 3을 사용하여 계산될 수 있다.The control unit 40 may set the preliminary cell index to an index of a cell that is a minimum voltage among cells excluding a weak cell, a high-impedance cell, and an internal short cell. In addition, the virtual reference cell voltage (

) Can be calculated using the following equations 1 to 3.

)은 하기의 수학식 4 내지 6와 같이 r번째 셀(즉, 균등화 목표 영역에서 최소 전압을 가지는 셀)의 셀 전압으로 설정될 수 있다.In addition, even if at least one of a weak cell, a high-impedance cell, and an internal short-circuit cell is present in the battery module 10, the cell having the minimum voltage in the equalization target area (for example, at the end of charging) is a weak cell and a high- If it does not correspond to at least one of the impedance cell and the internal short-circuit cell, as described above, the minimum voltage cell becomes the reference cell. In this case, the virtual reference cell voltage (

) May be set as the cell voltage of the r-th cell (ie, a cell having a minimum voltage in the equalization target region) as shown in Equations 4 to 6 below.

는 균등화 목표 영역(예를 들어, 충전 종료 시점)에서 예비 셀과 최소 전압 셀의 SoC 차이를 의미한다. 셀 밸런싱을 위한 가상의 기준 셀의 SOC는 예비 셀(r)의 SOC를

만큼 아래로 시프트시킨 것이며 가상의 기준 셀의 전압(

)은 예비 셀(r)의 전압을

에 해당하는 전압(

)만큼 아래로 시프트시킨 것이다. 이러한 가상 기준 셀 전압은 도 15의 (a) 및 (b)에서 점선으로 도시되어 있다.However, as shown in FIG. 15, when the cell having the minimum voltage in the equalization target region (eg, at the end of charging) is at least one of a weak cell, a high-impedance cell, and an internal short-circuit cell, the cell having the minimum voltage is used as the reference cell. If determined, invalid cell balancing may occur. Therefore, the preliminary cell index r may be set as the index of a cell that is the minimum voltage among cells other than this. At this time

Denotes the SoC difference between the spare cell and the minimum voltage cell in the equalization target area (eg, at the end of charging). The SOC of the virtual reference cell for cell balancing is the SOC of the spare cell (r).

Is shifted down by, and the voltage of the virtual reference cell (

) Is the voltage of the spare cell (r)

The voltage corresponding to (

) Shifted down. This virtual reference cell voltage is shown by dotted lines in FIGS. 15A and 15B.

는 충전 종료 시의 예비 셀과 최소 전압 셀의 SoC 차이를 의미한다.In Equation 1 above,

Denotes the difference in SoC between the spare cell and the minimum voltage cell at the end of charging.

Next, the control unit 40 determines the target cell for cell balancing (S250). The cell to be subjected to cell balancing refers to a cell to which cell balancing is to be performed. The control unit 40 may determine a cell that is not equalized based on the reference cell voltage in the equalization target region (eg, when charging ends) as the cell balancing target. For example, if the voltage of any cell in the equalization target area (for example, at the end of charging) has a voltage higher than a predetermined voltage than the reference cell voltage, the control unit 40 determines that the cell is an unbalanced cell, and , Can be determined as a cell balancing target.

Next, a cell balancing operation will be described in detail with reference to FIGS. 16 to 18.

16 is a flow chart specifically showing an example of a cell balancing step of FIG. 6, FIG. 17 is a graph illustrating a case of compensating the voltage of a virtual reference cell when cell balancing is performed, and FIG. 18 is a It is a graph showing an example of the reference cell voltage calculated when performed.

Referring to FIG. 16, the control unit 40 determines whether a condition for starting cell balancing is satisfied (S300). For example, when a voltage (or SoC)/current/temperature condition for starting cell balancing is satisfied, a balancing state in a target region for equalization, and a failure state, cell balancing may be started.

Then, the control unit 40 may generate a control signal for starting cell balancing. The balancing unit 20 performs cell balancing according to the control signal (S310). Cell balancing can be performed during charging or idle periods.

When the voltage of the spare cell used to obtain the virtual reference cell voltage decreases due to cell balancing, the control unit 40 compensates the virtual reference cell voltage in consideration of this (S320).

)에 의해 셀 밸런싱의 대상이 될 수 있다. 그리고 예비 셀에 대해 셀 밸런싱이 수행되면, 가상의 기준 셀 전압을 구하는 식(

)에서

이 셀 밸런싱이 수행된 만큼(

) 전압이 감소하므로 이를 보상할 필요가 있다. 따라서 균등화 목표 지점에서 예비 셀과 최소 전압 셀의 SOC 차이에 해당하는

에서 셀 밸런싱에 의한 예비 셀의 SOC 변화량을 차감할 필요가 있다.The spare cell also has a voltage (or SOC) difference (

) Can be the target of cell balancing. And when the cell balancing is performed for the spare cell, the equation for obtaining the virtual reference cell voltage (

)in

As long as this cell balancing was performed (

) As the voltage decreases, it needs to be compensated. Therefore, at the target point of equalization, the SOC difference between the spare cell and the minimum voltage cell

It is necessary to subtract the SOC change amount of the spare cell due to cell balancing.

에 대한 보상은 다음의 수학식 7 내지 9로 표현할 수 있다.When performing cell balancing for spare cells,

Compensation for can be expressed by the following equations 7 to 9.

는 밸런싱 전류이고

는 셀 밸런싱이 동작한 시간,

는 셀 밸런싱 듀티비,

은 예비 셀(r)의 용량이다. 상기의 수학식 2에 의해

와

가 일정 시간마다(예를 들어, 1분 간격마다) 갱신될 수 있다.here

Is the balancing current

Is the time when cell balancing was activated,

Is the cell balancing duty ratio,

Is the capacity of the spare cell r. By Equation 2 above

Wow

May be updated every predetermined time (eg, every 1 minute interval).

In relation to this, as shown in FIG. 17, when the spare cell is the target of cell balancing, the voltage of the uncompensated virtual reference cell is higher than the voltage of the cell having the minimum voltage in the equalization target area (in FIG. 17 at the end of charging). Since it may be lowered, an error of excessive cell balancing may occur. Therefore, when the spare cell becomes the target of cell balancing, the voltage of the virtual reference cell must be compensated.

)을 구하기 위해서는

에 해당하는 전압(

)을

에서 차감해야 한다.Hypothetical reference cell voltage (

In order to obtain)

The voltage corresponding to (

)of

Should be deducted from.

는 다음과 같이 근사 될 수 있다.It means the difference in SOC between the virtual reference cell and the spare cell at the equalization target point.

Can be approximated as

For example, if equalization is aimed at the charging cut-off point, the virtual reference cell voltage in the idle period may be approximated as shown in Equations 10 and 11.

Can be approximated as (In the idle period, convert the voltage of the spare cell to SoC, and from this value minus the difference between the virtual reference cell and the spare cell, which is obtained or approximated at the equalization target point, that is, the SoC of the virtual reference cell is obtained, and it is converted back to OCV. One value can approximate the voltage of a virtual reference cell)

는 앞에서 설명한 것과 같이 주기적으로 계산되어 보상에 반영할 수 있다. 이를 고려하면 휴지 구간에서의 가상의 기준 셀 전압은

과 같이 근사된다. 전 구간에서는

,

에서

를 전압으로 변환해야 하는데, 휴지 구간과 달리 SoC-OCV 관계를 이용하여 근사할 수 없기 때문에 충전 시 예비 셀의 SOC가 소정 비율만큼 증가할 때의 전압 증가량으로부터 1% ΔSOC 증가에 대한 ΔV를 구하고, 이를

에 곱하여

를 근사할 수 있다. 즉

로 근사한 값을 이용하여 가상 기준 셀의 전압을 근사한다 충전 구간에서의 가상 기준 셀의 전압(

)은 이전의 SoC의 소정 비율 증가분에 대응하는 전압을 계산하여 현재의 가상 기준 셀의 전압(

) 계산에 사용하므로, 도 18에서 도시된 바와 같이, 불연속적일 수 있다. To compensate for the virtual reference cell voltage when the spare cell becomes the target of cell balancing in the idle period

Is calculated periodically as described above and can be reflected in the compensation. Considering this, the virtual reference cell voltage in the idle period is

It is approximated as In all sections

,

in

Is converted to a voltage, but unlike the idle period, since it cannot be approximated using the SoC-OCV relationship, ΔV for 1% ΔSOC increase is obtained from the voltage increase when the SOC of the spare cell increases by a predetermined ratio during charging. This

By multiplying

Can be approximated. In other words

The voltage of the virtual reference cell is approximated by using the approximate value with the voltage of the virtual reference cell in the charging period (

) Is the voltage of the current virtual reference cell (

) Since it is used for calculation, as shown in FIG. 18, it may be discontinuous.

Next, the control unit 40 determines whether a condition for ending cell balancing is satisfied (S330). For example, the control unit 40 satisfies a voltage (or SoC)/current/temperature condition capable of terminating cell balancing, satisfies a balancing state in a high voltage region, or performs cell balancing when a failure state You can quit.

According to embodiments, there is an effect of maximizing battery capacity delivered to a load by preventing invalid cell balancing and providing a battery system balanced (eg, top-balanced) in an equalization target region.

The electronic or electrical device and/or any other related device or component according to the embodiments of the present invention described herein may be any suitable hardware, firmware (e.g., application-specific integrated circuit (ASIC)). )), software, or a combination of software, firmware, and hardware. For example, the various components of these devices may be formed on one integrated circuit (IC) chip or on individual IC chips. In addition, various components of these devices may be implemented on a flexible printed circuit film, a tape carrier package (TCP), a printed circuit board (PCB), or a single substrate. I can. The electrical connections or interconnections described herein are implemented by means of wires or conductive elements, for example on a PCB or other kind of circuit carrier. Conductive elements may include metallization, such as for example surface metallizations, and/or pins and/or conductive polymers or ceramics. In addition, electrical energy may be transmitted via a wireless connection, for example using electromagnetic radiation and/or light.

In addition, the various components of these devices are processes that run on one or more processors to perform the various functions described herein, run within one or more computing devices, execute computer program instructions, and interact with other system components. Or it could be a thread. Computer program instructions are stored in memory that can be implemented in a computing device using standard memory devices, such as random access memory (RAM). Computer program instructions may also be stored on other non-transitory computer readable media such as, for example, a CD-ROM, a flash drive, or the like.

In addition, those skilled in the art would appreciate that the functionality of various computing devices may be combined or integrated into a single computing device, or that the functionality of a particular computing device is distributed across one or more other computing devices without departing from the scope of the exemplary embodiments of the present invention. Be aware that it can be.

Claims (20)

A battery module including a plurality of battery cells,
A monitoring unit for monitoring parameters of each of the plurality of battery cells, and
Using the parameter, it is determined whether there are abnormal battery cells in the battery module, and when it is determined that there are abnormal battery cells in the battery module, a reference voltage for balancing the plurality of battery cells is calculated, and a cell to an equalization target area Control unit that controls to perform balancing
Battery system comprising a. The method of claim 1,
The abnormal battery cell is at least one of a weak cell, a high-impedance cell, and an internal short-circuit cell,
Battery system. The method of claim 1,
The equalization target area is any one of a top-balancing area, a mid-balancing area, and a bottom-balancing area,
Battery system. The method of claim 1,
The control unit determines whether there is an SoC shift cell in the battery module using a state of charge (SoC) calculated at any two time points,
Battery system. The method of claim 1,
The control unit determines whether there is an SoC shift cell in the battery module by comparing the voltage (OCV) measured in the idle period before charging or discharging with the OCV measured in the idle period after the charging or discharging. doing,
Battery system. The method of claim 1,
The control unit calculates the capacity of each of the plurality of battery cells using the parameter, and determines whether there is a weak cell in the battery module by comparing the capacities,
Battery system. The method of claim 1,
The control unit calculates a resistance value of each of the plurality of battery cells using the parameter, and determines whether there is a high-impedance cell in the battery module by comparing the resistance values,
Battery system. The method of claim 1,
The control unit determines a minimum voltage cell other than the abnormal cell among the plurality of battery cells as a spare cell, and calculates the reference voltage using the SoC difference between the spare cell and the abnormal cell in the equalization target region. ,
Battery system. The method of claim 8,
The control unit is a formula,

,

,

Calculate the reference voltage using

Is the SoC of the spare cell,

Is the SoC of the minimum voltage cell in the equalization target region,

Is the voltage of the spare cell,

Is the reference voltage,
Battery system. The method of claim 9,
The control unit compensates the reference voltage according to the time at which the cell balancing is performed,
Battery system. The method of claim 10,
The control unit is a formula,

,

,
Compensate the reference voltage using

Is the balancing current

Is the time when the cell balancing was performed,

Is the duty ratio of the cell balancing,

Is the capacity of the spare cell included in the battery module, and K is a constant,
Battery system. Monitoring parameters of each of the plurality of battery cells included in the battery module,
Determining whether there are abnormal battery cells in the battery module using the parameter,
If it is determined that there are abnormal battery cells in the battery module, calculating a reference voltage for balancing the plurality of battery cells, and
Performing cell balancing to an equalization target region using the reference voltage
Battery system control method comprising a. The method of claim 12,
The step of determining whether there is an abnormal battery cell,
Using the state of charge (SoC) calculated at any two time points, determining whether there is an SoC shift cell in the battery module,
Battery system control method. The method of claim 12,
The step of determining whether there is an abnormal battery cell,
Comprising the step of comparing an open circuit voltage (OCV) measured in a dormant period before charging or discharging with an OCV measured in a dormant period after the charging or discharging, and determining whether there is an SoC shift cell in the battery module. doing,
Battery system control method. The method of claim 12,
The step of determining whether there is an abnormal battery cell,
Calculating the capacity of each of the plurality of battery cells using the parameter, and
Comprising the step of comparing the capacities to determine whether there is a weak cell in the battery module,
Battery system control method. The method of claim 12,
The step of determining whether there is an abnormal battery cell,
Calculating a resistance value of each of the plurality of battery cells using the parameter, and
Comprising the step of comparing the resistance values to determine whether there is a high-impedance cell in the battery module,
Battery system control method. The method of claim 12,
The step of calculating the reference voltage,
Determining a minimum voltage cell other than the abnormal cell among the plurality of battery cells as a spare cell, and
Comprising the step of calculating the reference voltage using the SoC difference between the spare cell and the abnormal cell in the equalization target region,
Battery system control method. The method of claim 12,
Compensating the reference voltage according to the time at which the cell balancing has been performed. The method of claim 12,
The abnormal battery cell is at least one of a weak cell, a high-impedance cell, and an internal short-circuit cell,
Battery system control method. The method of claim 12,
The equalization target area is any one of a top-balancing area, a mid-balancing area, and a bottom-balancing area,
Battery system control method.

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