KR101671998B1 - Apparatus and Method for estimating battery life - Google Patents

Abstract

The present invention provides an apparatus and method for measuring a capacity deterioration state of a battery. To this end, an apparatus for measuring the capacity deterioration of a battery includes at least one battery used in a plug-in hybrid vehicle or an electric vehicle, a sensing unit sensing voltage, current and temperature of at least one battery, A data processing section for measuring voltage, current and temperature data from the sensing section when the SOC (State Of Charge) is in a predetermined area; and a data processing section for setting at least two points to the voltage data, To the at least one battery equivalent circuit model to calculate the deterioration capacity.

Description

TECHNICAL FIELD [0001] The present invention relates to an apparatus and a method for measuring a capacity deterioration state of a battery,

The present invention relates to an apparatus and method for measuring a capacity deterioration state of a battery, and more particularly, to an apparatus and a method for measuring a capacity deterioration of a battery in a hybrid vehicle, a plug-in hybrid vehicle, or an electric vehicle.

Recently, plug-in hybrid electric vehicles (PHEVs) and electric vehicles (PHEVs) have attracted a great deal of attention due to the importance of environmental considerations in transportation. Particularly, for PHEV and EV, development of battery technology is considered to be very important. This is because the capacity and power of the battery must be greater than in other green vehicles.

However, such a battery generally has a service life, and the internal resistance increases naturally by use, and the output is reduced. And, the usable capacity is also reduced. The performance of these batteries is considered to be important because this degradation can cause degradation in the fuel economy and performance of the plug-in hybrid vehicle.

A patent has already been filed on the reduction in the capacity of the battery and the reduction in the output of the battery. For example, US Patent Nos. US 2004/0220758 and US 2006/0113959 can be mentioned.

However, these patents can be quite disadvantageous for practical applications because they can only be measured with a specific current pattern (e.g., a specific constant current pattern) such as charging. Accordingly, there is a demand for a technique capable of measuring the capacity drop and the output drop regardless of the current magnitude.

It is an object of the present invention to provide an apparatus and method for measuring a capacity drop and an output drop of a battery regardless of the magnitude of a current in a constant current pattern.

It is another object of the present invention to provide an apparatus and method for measuring capacity deterioration in real time.

Still another object of the present invention is to provide an apparatus and a method that can easily measure capacity deterioration.

In order to achieve the above object, the present invention provides a hybrid vehicle comprising at least one battery used in a hybrid vehicle, a plug-in hybrid vehicle, or an electric vehicle, a sensing unit sensing current, voltage and temperature of at least one battery, A data processing section for measuring voltage and current data from the sensing section when SOC (State Of Charge) is in a predetermined region, and a data processing section for setting at least two points in the voltage data, And a calculation unit for calculating the deterioration capacity by applying the voltage data to at least one battery equivalent circuit model.

In addition, a memory unit for storing voltage, current, capacity deterioration, and moving average deterioration capacity may be further included.

In another embodiment, the calculation unit may calculate the moving average deterioration capacity by adding deterioration capacities stored for a predetermined period while the automobile is moving.

According to another aspect of the present invention, there is provided a method of controlling a hybrid vehicle, the method comprising: checking whether current flowing in at least one battery used in a hybrid vehicle, a plug-in hybrid vehicle, or an electric vehicle is a constant current on a charging interval; Measuring at least one battery current and voltage data if the SOC is within a predetermined range; determining at least two points in the measured voltage data; And calculating capacitance deterioration by applying voltage data corresponding to at least two points to at least one battery equivalent circuit model.

In another embodiment, the method may further include calculating a moving average deterioration capacity by adding the deterioration capacities stored for a predetermined period while the automobile moves.

(a₁은 SOC와 기전력(Electromotive Force) 사이의 기울기이고, Δt는 상기 2개의 포인트 간 시간 간격이며, ΔV는 전압차이임)를 이용하여 계산하고, 이동 평균 열화 용량은,

(여기서, 가중치

임 )을 이용하여 계산된다. At this time,

(a ₁ is the slope between the SOC and the electromotive force,? t is the time interval between the two points, and? V is the voltage difference), and the moving average deterioration capacity is

(Here,

Lt; / RTI >

Here, MAQ _n is a moving average value obtained by adding deterioration capacities Q, which are values approximating a predetermined deterioration capacity.

Here, it is assumed that the value of a ₁ varies depending on the characteristics of the battery and the temperature, and even if the capacity decreases, there is no change.

Here, the equivalent circuit model is an electric circuit in which the battery is represented by the total resistance R ^* , the current I, the capacitor C, the terminal voltage V, and the electromotive force Vo parameter.

로 표현할 수 있다. 여기서 NC는 Nominal Capacity로 공칭용량, MAQn은 이동 평균 열화 용량을 가리킨다.
In yet another embodiment, the method may further include calculating a state of health (SOH) of the battery,

. Where NC is the nominal capacity, nominal capacity, and MAQn is the moving average deterioration capacity.

According to the present invention, it is possible to measure the capacity drop and the output drop of the battery regardless of the current magnitude in the constant current pattern.

Another advantage of the present invention is that capacity deterioration can be measured in real time.

Another advantage of the present invention is that it can be applied to a capacity reduction algorithm that can be used on-line, and the form of calculating the capacity deterioration is very simple and the number of necessary data is very small. .

1 is a system configuration diagram for measuring a capacity of a battery according to an embodiment of the present invention.
2 is a block diagram of an MCU (Main Controller Unit) unit of FIG.
FIG. 3A is a schematic view showing a process of measuring the capacity of a battery according to the present invention.
FIG. 3B is a circuit diagram of the equivalent circuit model of FIG. 3A.
4 is a flowchart illustrating a process of measuring a capacity of a battery according to an embodiment of the present invention.
FIG. 5 is a graph showing a period in which a capacity measurement process of a battery according to an embodiment of the present invention is performed.
FIG. 6 is a graph showing the moving average deterioration capacity calculated by summing the deterioration capacities measured using FIGS. 1 to 5 according to another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a system configuration diagram for measuring the capacity deterioration of a battery according to the present invention. This system configuration diagram largely includes a battery pack 100, sensing units 111 to 113 for sensing the voltage, current, and temperature of the battery pack, and a controller for receiving data from the sensing units 111 to 113 to measure the capacity deterioration A battery management system (BMS) unit 110 including a microcontroller unit (MCU) unit 120 and a vehicle controller 140 for receiving deterioration capacities measured by the BMS unit 110. The functions and roles of these components will be described as follows.

In the battery pack 100, the batteries 101 to 10n are configured in series or in parallel, and the battery may be a hybrid battery such as a nickel metal battery or a lithium ion battery. Of course, in an embodiment of the present invention, the battery pack 100 is configured as one pack only for the sake of understanding, but it is also possible to configure the battery pack 100 as a plurality of subpacks.

The BMS unit 110 includes sensing units 111 to 113 and an MCU unit 120 and measures a capacity deterioration of the battery pack 100. [ That is, the sensing units 111 to 113 include a voltage sensing unit 111 for sensing current, voltage, and temperature of the batteries 101 to 10n in the battery pack 100, a current sensing unit 112, (113).

Of course, the temperature sensing unit 113 may sense the temperatures of the battery pack 100 or the batteries 101 to 10n. Here, the current sensing unit 112 may be a hall current transformer that measures a current using a Hall element and outputs an analog current signal corresponding to the measured current, but the present invention is not limited thereto Other devices can be applied as long as they can sense current.

The MCU 120 receives voltage, current, and temperature values of each of the batteries 101 to 10n sensed by the sensing units 111 to 113 and calculates a state of charge (SOC) of the batteries 101 to 10n ) And a SOH (State of Health) value, and calculates the calculated moving average deterioration capacity by averaging the deterioration capacities of the batteries 101 to 10n and the deterioration capacities stored for a predetermined time while the vehicle is moving. The configuration of the MCU for this calculation process is shown in Fig. This will be described later. The SOC, the SOH value, the deterioration capacity value, and the like are stored in the memory unit 130 and transmitted to the vehicle controller 140.

The memory unit 130 may be a memory provided in the MCU unit 120 or may be a separate memory. Therefore, a non-volatile memory such as a hard disk drive, a flash memory, a ferro-electric RAM (FRAM), a phase-change RAM (PRAM), a magnetic RAM (MRAM)

The vehicle controller 140 performs a function for optimally controlling the performance of the main system required for driving the plug-in hybrid vehicle or the electric vehicle. To this end, SOC and SOH values of the battery are transmitted to the vehicle controller 140 using a CAN (Controller Area Network) communication method between the vehicle controller 140 and the MCU unit 120.

2 is a block diagram of the MCU unit of FIG. The MCU unit 120 is provided with a data processing unit 121 for processing the data transmitted from the sensing units 111 to 113, a voltage, current, and temperature values from the data processing unit 121 to estimate SOC and SOH values, A memory unit 130 for storing these values as data, and the like.

The calculation unit 122 receives the voltage, current, and temperature values sensed by the sensing units 111 to 113 through the data processing unit 121, determines a specific interval from these values, And calculates the capacity of the batteries 101 to 10n and the moving average deterioration capacity from them. Of course, these values are stored in real time in the memory unit 130 and transmitted to the vehicle controller 140.

The process of measuring the deterioration capacity of the batteries of the batteries 101 to 10n will now be described. First, for ease of understanding of the present invention, the process of measuring the deterioration capacity of the battery is schematically shown in FIG. 3A. FIG. 3A is a schematic view showing a process of measuring a deterioration capacity of a battery according to the present invention.

Plug-in hybrids or electric cars basically charge the batteries in the car through an electric plug when parking at night. In this case, charging is performed from a low SOC region to a very high region, and the deterioration capacity of the battery is calculated using the SOC.

This deterioration capacity is calculated by the battery model, where the battery model is an equivalent circuit model that simplifies the complex battery model. This equivalent circuit model is shown in Fig. 3B. 3B is a circuit diagram of the equivalent circuit model of FIG. 3A. As shown in the drawing, the concept of the total resistance R ^* , which is a combination of a complicated RC circuit and an internal resistance R ₀ , is introduced, and the model is developed to measure the capacitance drop. A description of the parameters of this equivalent circuit model is shown in Table 1 as follows.

I Current (-: charge, +: discharge) V Terminal voltage V _O Open circuit voltage R ^* Total resistance

Referring to FIG. 3A, when the SOC reaches a predetermined area, data collection for a battery is performed. At this time, since the current I is a constant current, it becomes a constant and the voltage V changes in real time. Therefore, the interval is set 300 by holding V at 2 points or more than 2 points, for example, V ₁ and V ₂ . When these two points are applied to the equivalent circuit model (310), the degradation capacity Q is calculated. In addition, the moving average deterioration capacity is calculated (320) by adding the deterioration capacities Q stored during the movement of the vehicle. Based on this, it can be determined whether the state of the battery is in a capacity-reduced state (330).

Hereinafter, the process of measuring the capacity deterioration of the battery will be described in detail with reference to FIGS. 4 and 5. FIG. 4 is a flowchart illustrating a method for measuring a capacity deterioration of a battery according to the present invention.

Before explaining the capacity deterioration measuring process of the battery with reference to FIG. 4, the following assumption should be made first.

That is, the first assumption is that the current must flow in the form of a constant current during charging, so that there is no change in current. Second, the relationship between SOC and electromotive force must be linear in the SOC of the middle region.

Also, the third should be a constant because there is little change in total resistance in the charge section. Finally, even if there is a drop in capacity, there should be little change in the EMF curve.

The algorithm in the flowchart of FIG. 4 is intended to be activated when a plug-in hybrid vehicle or an electric vehicle is charging. This is shown in Fig. FIG. 5 is a graph showing a period in which a capacity measurement process of a battery according to an embodiment of the present invention is performed. That is, a section where L _m and L _{m + 1} 510 are charged, and a section preceding L _m , between L _m and L _{m + 1} , and after L _{m +1} becomes a data collection section 510. This data collection period 510 has a constant current period composed of n pieces of data.

Therefore, in this data collection period 510, the algorithm of the flowchart of FIG. 4 is activated to collect current and voltage data. Of course, the collection of this data takes place at some time intervals. Here, the time interval means an interval of several hours to several days, and the time interval need not be constant.

That is, the MCU unit 120 checks whether a vehicle such as a plug-in hybrid vehicle or an electric car is in the constant current charging section (step S400). If it is in the constant current charging period, it is confirmed whether the SOC is in a certain region (step S410).

Otherwise, if it is not in the constant current charging interval, or if the SOC is not within a certain range, the algorithm of Fig. 4 is not activated (step S401).

The collection of the current and voltage data starts at the moment when the SOC enters a certain region, and the measurement is ended when the SOC is out of the predetermined SOC region (Step S420). At this time, the necessary data is total current data, which is necessary to confirm that the current flows constantly. When it is confirmed that the current flows constantly, the corresponding voltage data is also stored.

When the current and voltage data are collected, capacity estimation is performed through the equivalent circuit model. That is, a basic equivalent circuit model is utilized. However, as shown in FIG. 3B, the equivalent circuit model used here introduces the concept of the total resistance R ^* , which is the sum of the RC circuit and the internal resistance R ₀ , which can explain the polarization phenomenon.

The formula for this model is: When modeling the equivalent circuit model, we can see that the equation is composed as follows.

Here, the two points, point 1 and point 2, are set as follows (step S430).

Subtracting Equation (1) from Equation (2) yields the following equation.

Here, it can be considered that the currents are the same under the assumption that charging is performed in the constant current mode. Also, assuming that the internal resistance is constant during charging, R ^* is also constant.

Therefore, the above equation (5) can be summarized as follows.

Here, the electromotive force V ₀ is calculated as a function of the SOC. At this time, the relationship between the electromotive force (replaced with the open circuit voltage OCV (open circuit voltage at the time of the battery free load unstable state) and the SOC can be linearized in the SOC of the middle region as shown in the following table.

That is, it can be expressed as the following equation.

Here, the a values have different values depending on the characteristics of the battery and the temperature, respectively. It is also assumed that a _{1, which} is a slope, does not change even if a capacity decrease occurs. In this case, if point 1 and point 2 are set, they can be expressed as follows.

The difference between Equation (8) and Equation (9) can be expressed as the following equation.

If the equations (6) and (10) are summarized, the following equations can be obtained.

Incidentally, the timing at which the algorithm of the flowchart of Fig. 4 is activated is a case of charging with a constant current. Therefore, since the current is constant for a short time, the calculation of the SOC becomes possible through the current counting (Ah counting).

Where 100 means 100 percent SOC and 3600 means 1 hour in seconds.

Since the current is a constant current type, current integration can be expressed as a product of current and time. Therefore, the above equation can be summarized as the following equation.

Where Q is the current battery capacity.

The above equations (11) and (13) are summarized as follows (step S440).

This formula can be used to measure the current capacity of the battery. That is, it is possible to measure the capacity deterioration of the battery in real time when the slope between the current and the point, the voltage difference, and the SOC and the electromotive force are known.

When the battery capacity is calculated, this capacity value is stored in real time, and it is also possible to calculate the moving average deterioration capacity by summing it (step S450). In more detail, the capacity is calculated through the above-described FIG. 1 to FIG. 5, and this capacity is stored in real time.

However, since the decrease in the capacity of the battery occurs over a long period of time, the change is not large at the time of day. Therefore, the final capacity is determined through the moving average value in order to prevent the occurrence of noise and the like.

Therefore, the moving average is to averaged over the previous n values for the measured capacity to measure its optimal value. Here, in order to suppress the occurrence of noise as much as possible, the average value is measured with respect to the remaining values except for the maximum value and the minimum value of the measured capacity.

In the averaging, a larger weight is assigned to the value close to the current measurement. The formula for this is as follows.

이고, MAQ는 이동 평균을 통한 Q의 값이다. 위 수학식 15를 통해 이동 평균 열화 용량을 정할 수 있다.here

And MAQ is the value of Q through the moving average. The moving average deterioration capacity can be determined through Equation (15).

Through the above-described method, it is possible to measure the life (capacity) state of a vehicle such as a plug-in hybrid vehicle or an electric car in real time. Because, in the case of plug-in hybrid electric vehicles and electric vehicles, there is a continuous charging interval, so that the capacity decrease can be calculated during such charging.

Here, the state of health of the battery (SOH) is defined as follows.

Where NC is the nominal capacity, nominal capacity, and MAQ _n is the moving average deterioration capacity.

A graph illustrating the moving average deterioration capacity quantitatively for easy understanding of the present invention is shown in Fig.

That is, FIG. 6 is a graph showing the moving average deterioration capacity calculated by summing the capacities measured using FIGS. 1 to 5 according to another embodiment of the present invention. Referring to FIG. 6, the capacity is measured according to the elapsed time, and only the deteriorated capacity in the box 600 for the moving average is calculated. That is, the capacity of the maximum and minimum values out of the box 600 is excluded.

The estimated values of Q in the hybrid vehicle or electric vehicle according to Figs. 1 to 6 can be expressed as shown in the following table.

That is, as shown in Table 3, the capacity is decreasing with time.

When the capacity reduction algorithm described above in FIGS. 1 to 6 is used, the capacity reduction algorithm that can be used on-line can be applied. Especially, it is very simple compared to the existing models. Algorithms for measuring the existing capacity degradation are very complicated and often difficult to mount on a battery management system. In this case, however, the form of the expression is very simple and the number of data required is very small and can be used quite conveniently.

While the preferred embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art will appreciate that the scope of the present invention is not limited to these embodiments and that many modifications are possible. Accordingly, the scope of the present invention should be defined by the appended claims and their equivalents.

101 ~ 10n: Battery 100: Battery pack
110: BMS unit 111: Voltage sensing unit
112: current sensing unit 113: temperature sensing unit
120: MCU unit 130: memory unit
140: vehicle controller 121: data processor
122:

Claims (10)

At least one battery used in a hybrid vehicle, a plug-in hybrid vehicle, or an electric vehicle,
A sensing unit sensing current, voltage and temperature of the at least one battery;
A data processing unit for measuring the voltage and current data from the sensing unit when the current is a constant current in a charging interval and the SOC (State Of Charge) is in a predetermined range,
Calculating at least two points in the voltage data, calculating the deterioration capacity by applying the voltage data corresponding to the at least two points to the at least one battery equivalent circuit model, and storing the deterioration capacity for a predetermined period of time A calculation unit for calculating the moving average deterioration capacity by adding the deterioration capacities,
/ RTI >
The deterioration capacity,

(a1 is the slope between the SOC and the electromotive force, DELTA t is the time interval between the two points and DELTA V is the voltage difference)
The moving average deterioration capacity,

(Here,

Wherein the weighted value is a weighted value that is closer to the current measurement value, and MAQn is a summed average value of the deteriorated capacity Q, which is a value approximated to a predetermined deteriorated capacity.
delete The method according to claim 1,
And a memory unit that stores the voltage, current, deterioration capacity, and moving average deterioration capacity of the battery.
delete The method according to claim 1,
The value of a ₁ varies depending on the characteristics of the battery and the temperature, and even if the deterioration of the capacity deteriorates,
The equivalent circuit model is an electric circuit in which the battery is represented by parameters such as total resistance (R ^* ), current (I), terminal voltage (V) and electromotive force (Vo). Checking whether a current flowing in at least one battery used in a plug-in hybrid vehicle or an electric vehicle is a constant current on a charging section,
Confirming whether the SOC (State Of Charge) is in a predetermined region if the current is a constant current in the charging section;
Measuring current, voltage and temperature data of the at least one battery if the SOC is within the predetermined range;
Setting at least two points in the measured voltage data,
Applying voltage data corresponding to the at least two points to the at least one battery equivalent circuit model to calculate a deterioration capacity;
Calculating a moving average deterioration capacity by summing the deterioration capacities stored for a predetermined period while the automobile is moving
/ RTI >
The deterioration capacity,

(a1 is the slope between the SOC and the electromotive force, DELTA t is the time interval between the two points and DELTA V is the voltage difference)
The moving average deterioration capacity,

(Here,

, And weights should be weighted more heavily for values close to the current measurement. ), Wherein MAQn is a summed average value of the deterioration capacities Q, which is a value approximating a predetermined deterioration capacity.
delete delete The method according to claim 6,
The value of a ₁ varies depending on the characteristics of the battery and the temperature. Even if the capacity of the battery is deteriorated when the state of charge (SOC) of the battery is in a predetermined region,
Wherein the equivalent circuit model is an electric circuit in which the battery is expressed by parameters such as total resistance (R ^* ), current (I), terminal voltage (V), and electromotive force (Vo). The method according to claim 6,
Further comprising calculating a battery life state (SOH: State of Health)
The battery life state is expressed by the following equation

(NC is a nominal capacity, nominal capacity, and MAQ _n is a moving average deterioration capacity).

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