KR20140001383A - Apparatus and method thereof for presuming state of charge of battery - Google Patents

Abstract

One embodiment relates to presuming of a SOC of a battery by selecting and compounding an electric current integration and an OCV presuming method in accordance with a state of capacity of the battery (polarized voltage,voltage value,operation state information, battery temperature, and electric current on a battery). The battery sets as a primary SOC by the OCV presuming method in which unused at predetermined specific time; presumes the SOC in accordance with the electric current integration below predetermined specific battery temperature; estimates the SOC in accordance with the OCV above the predetermined specific battery temperature; thereby improving precision of the SOC in accordance with distinguished ratio in the range of the predetermined specific temperature. [Reference numerals] (AA) Start; (BB) End; (S201) Measuring OCV and estimating initial SOC; (S203) Renewing the SOC by am integration method; (S205) Integration method + estimating the SOC by the OCV; (S207) Estimating the SOC by the OCV

Description

Apparatus and method for estimating battery capacity status {APPARATUS AND METHOD THEREOF FOR PRESUMING STATE OF CHARGE OF BATTERY}

The embodiment relates to an apparatus and a method for estimating a battery capacity state (SOC, STATE OF CHARGE) using an open circuit voltage (OCV) and / or a current integration scheme based on battery state information.

There are various methods of measuring the capacity state (SOC, state of charge in a battery charge / discharge state or remaining capacity state) of a secondary battery.

For example, the SOC may be estimated by the open voltage (OCV), or the SOC may be estimated based on the current integration method.

At this time, the disadvantage of SOC estimation by the current integration method is that it is difficult to know the initial SOC at the time of battery use accurately, and SOC error may occur largely in the section due to the SOC drop phenomenon in which the end SOC decreases rapidly.

On the other hand, the disadvantage of the SOC estimation method by OCV is that the OCV changes rapidly with respect to the battery temperature change in the low temperature range, so that the SOC error increases, and the charge OCV and the discharge OCV differ due to the hysteresis effect. In applying the -SOC relationship, when the charging current flows, it follows the OCV-SOC relationship at the time of charging by a certain ratio, and when the discharge current flows, the ratio of the OCV-SOC at the time of discharge to a certain ratio. There is a problem to decide whether to follow.

The embodiment proposes to estimate the SOC by selecting / combining the current integration method and the OCV estimation method based on the battery state information (polarization voltage, voltage value, operating state, battery temperature or battery current flow).

The embodiment proposes to perform the initial SOC measurement of the battery based on the OCV method.

  In the embodiment, the SOC is estimated based on the current integration method below the predetermined temperature of the battery, the SOC is estimated based on the OCV above the predetermined temperature of the battery, and the current integration method and the OCV method are preset in the predetermined temperature range. It is suggested that the SOC is estimated as the ratio is applied based on temperature.

The embodiment proposes to estimate the SOC based on the current integration method when the direction of the current changes or the flow of the current is interrupted according to the charge / discharge switching during the SOC estimation by the OCV.

 In the embodiment, when the temperature of the battery rises while the SOC estimation is performed by the current integration method, it is proposed to reduce the estimated ratio by the integrated current method and increase the estimated ratio by the OCV method.

An apparatus for estimating battery capacity state according to an embodiment may include: a voltage sensing unit measuring a voltage value of a battery; In the SOC estimation method using the OCV and current integration method, the SOC based on the current integration method is estimated below the predetermined battery temperature, and the SOC based on the OCV is estimated above the predetermined battery temperature. A temperature sensing unit for measuring the temperature of the battery to set the current integration method and the estimation by the OCV to be performed based on a predetermined ratio; A current sensing unit for measuring the direction of the current to switch to the current integration method when the direction of the current changes or the flow is interrupted while the SOC estimation by the OCV is in progress, among the SOC estimation methods by the OCV and the current integration method; A memory unit storing an associated table for applying an SOC to at least one of a battery temperature, a voltage value, a current value, a current direction, and a battery use time; An SOC estimator for estimating the SOC under the control of the controller in each of the above cases;

An input unit / display unit for inputting a user command and outputting an estimated SOC result; And a controller for controlling the components and controlling SOC estimation by OCV at a time point of operation of a predetermined battery.

The battery capacity state estimation method may include estimating an initial SOC of a battery based on an OCV method; Estimating the SOC based on the current integration method when the temperature of the battery is less than or equal to a predetermined temperature; If the temperature of the battery is a predetermined temperature range, the SOC is estimated while the current integration method and the OCV method are variably applied at a predetermined ratio in response to the temperature change; And estimating the SOC based on the OCV method when the temperature of the battery is greater than or equal to a predetermined temperature.

The embodiment can increase accuracy by estimating the SOC of the battery by selecting / combining the current integration method and the OCV estimation method based on the battery state information (polarization voltage, voltage value, operating state, battery temperature or battery current flow).

In the embodiment, since the battery is not used for a predetermined time, for example, when there is no polarization voltage or the polarization voltage is less than a predetermined value, the accurate SOC can be obtained by setting the initial SOC by obtaining the battery SOC by the OCV estimation method.

According to the embodiment, the SOC is estimated based on the current integration method below the predetermined temperature of the battery, the SOC based on the OCV is estimated above the temperature of the predetermined battery, and the current integration method and the estimation by the OCV are preset in the predetermined temperature range. The accuracy of the SOC can be increased by performing the ratio according to the set ratio.

According to the embodiment, when the direction of the current changes or the flow is interrupted such as switching the charge / discharge during the SOC estimation by the OCV, the accurate SOC estimation can be performed through the SOC estimation by the current integration method. When the temperature value increases, the SOC estimation by the OCV is applied as the main ratio among the OCV and SOC estimation methods by the current integration method (reduce the estimation ratio by the current integration method and increase the estimation ratio by the OCV). Can increase.

1 is a block diagram illustrating respective components for checking a state of a battery according to an exemplary embodiment.
FIG. 2 is a flowchart illustrating SOC estimation based on OCV and SOC estimation based on temperature according to an embodiment.
Figure 3 is a flow chart showing an example of the integrated integration method and OCV method usage and its application rate depending on the battery temperature
Figure 4 shows the estimation of the SOC by switching to the current integration method when the direction of the current is changed or the flow is interrupted based on the conversion to charge / discharge, etc. during the SOC estimation by OCV, when the temperature rises due to the use of the battery Flowchart showing estimating SOC by gradually increasing the ratio by OCV method as shown in Table 1.

Hereinafter, a battery capacity state (SOC) estimating apparatus and method will be described with reference to the accompanying drawings.

First, the terms used in the embodiments of the present invention are selected as general terms that are widely used at present, but in some cases, the terms selected by the applicant are arbitrarily selected. , It should be understood that the present embodiment should be grasped as an operation / meaning of a term that is not a name of a simple term.

In the description of the embodiment, the state of charge (SOC) is a meaning including a charge / discharge state of the battery or a remaining capacity state of the battery, and indicates the capacity state of the battery in each state.

Also, in the description of the embodiments, the connections, connections, or contacts between the components means that they are not only directly connected, but also include mechanical connections, electrical connections, or connections through other components, / Wireless connection is also included.

In an embodiment, the division of the charge and the discharge may be determined based on the polarization voltage inside the battery, and the polarity of the polarization voltage is determined by accumulating values according to the current direction. When the current has negative (-) polarity, negative (-) values accumulate. When the current is positive (+) polarity, positive polarity accumulates.

When there is no current flow, the polarization voltage converges to zero. When the value of the polarization voltage becomes zero, the SOC is maintained at the last polarity

In other words, when distinguishing between the charging and discharging state, it may be simply based on the current direction, but in this case, it may not sufficiently reflect the state inside the battery. Since the OCV (Open Circuit Voltage), which is a reference in the same battery capacity state (SOC), differs greatly, the battery capacity state (SOC) greatly changes when the current is changed based on the current.

For example, if the battery is charged at 15A for 30 minutes and then discharged at 1A for 10 seconds, the final direction of current is discharge but the state of charge (SOC) inside the battery is closer to charging. When determining the state of charging and discharging of the battery, the magnitude of the current and the duration of the current must be fully considered. Therefore, according to another embodiment of the present invention, the part meeting the criteria is determined as the polarization voltage component inside the battery to determine the states of charge and discharge. The polarization voltage is the internal component of the battery, which changes with the polarity and duration of the current.

1 is a block diagram illustrating respective components for checking a state of a battery according to an exemplary embodiment.

Referring to FIG. 1, the battery capacity estimating method according to an embodiment of the present disclosure may be implemented through the battery 100, the load 107, and respective components.

The type of the battery 100 is not particularly limited, and may include a lithium ion battery, a lithium polymer battery, a nickel cadmium battery, a nickel hydride battery, a nickel zinc battery, and the like, which are rechargeable and require a state of charge.

The type of the load 107 is not particularly limited, and may include a portable electronic device such as a video camera, a mobile phone, a portable PC, a PMP, an MP3 player, a motor of a vehicle or an electric / hybrid vehicle, a DC to DC converter, and the like. .

In addition, the configuration of Figure 1, the voltage sensing unit 101 for measuring the polarization voltage and / and voltage value of the battery; In the SOC estimation method using the OCV and current integration method, the SOC based on the current integration method is estimated below the predetermined battery temperature, and the SOC based on the OCV is estimated above the predetermined battery temperature, and the current is determined in the predetermined temperature range. A temperature sensing unit 102 for measuring the temperature of the battery in order to set the integration method and the estimation by the OCV to be performed based on a predetermined ratio; A current sensing unit (103) for measuring the direction of the current to switch to the current integration method when the direction of the current changes or the flow is interrupted during the SOC estimation by the OCV and the current integration method; A memory unit 104 storing a related table for applying SOC to at least one of a battery temperature, a voltage value, a current value, a current direction, and a battery usage time; An SOC estimator 109 for estimating the SOC under the control of the controller in each of the above cases; An input / display section 106 for inputting a user command or outputting an estimated SOC result; And a controller 105 for controlling the components and controlling SOC estimation by OCV at a time point of use of a predetermined battery.

Through the above configurations, the present embodiment selects / combines the current integration method and the OCV estimation method based on the state information of the battery (polarization voltage, voltage value, operating state, battery temperature, or battery current flow). The accuracy of the estimate can be increased.

FIG. 2 shows the OCV in the SOC estimation method using the OCV and the current integration method in the case where the battery is not used for a predetermined time or when the polarization voltage of the battery is measured and there is no polarization voltage or the polarization voltage is less than the predetermined value. The initial SOC is estimated based on the method, and when the battery temperature is lower than the predetermined battery temperature (-10 degrees or less), the SOC is estimated by the current integration method, and the current integration method and the OCV method are performed at the predetermined intermediate temperature (-10 degrees to 0 degrees). Are estimated in combination with each other. If the battery temperature is equal to or greater than a predetermined battery temperature (0 degrees), the SOC based on the OCV is estimated.

Each of the predetermined temperatures may be changed according to the climate of each country or the state of the battery as an embodiment.

The present invention is to estimate the SOC by using or combining the current integration method and / or OCV method independently based on the battery temperature.

In general, in a hybrid electric vehicle or an electric vehicle using a high voltage battery, it is very important to know the SOC of the battery, and also to inform the driver of the battery capacity, for example, the remaining capacity while driving.

As a method of calculating the SOC of the battery while driving, it is commonly used to calculate the current SOC by measuring the amount of charge and discharge current. The current SOC is calculated by integrating the amount of charge / discharge current measured in a specific SOC as a reference. It is estimated and updated.

In the process of calculating the SOC, the SOC, which is a reference for integrating the charge / discharge currents, is appropriately set, that is, the initial value of the SOC (remaining capacity) of the battery (hereinafter referred to as 'initial SOC') prior to driving is appropriately set. In this embodiment, an initial SOC is estimated using an open circuit voltage (hereinafter, referred to as an 'OCV'). (S 201).

Here, the estimation of the initial SOC by the OCV will be described using an example of the initial measurement while the battery is kept turned off for at least two hours. In addition, the SOC value measured in the absence or near polarization voltage is set as the initial SOC.

In other words, before operating the vehicle or immediately after the vehicle's ignition key is turned on, the OCV is measured to estimate the SOC therefrom, and the estimated SOC is set as the initial SOC that is the integration reference, and the subsequent charging is performed. The current SOC is updated by integrating the amount of discharge current.

In the embodiment, when the temperature of the battery is low (for example, -10 degrees or less), the SOC is estimated by the current integration method, and at a predetermined intermediate temperature (for example, -10 degrees to 0 degrees), The combination of the OCV method is used to estimate the SOC based on the OCV if the battery temperature is above a predetermined temperature (eg 0 degrees) (S 203, S 205, S 207).

As shown in FIG. 2, when the ignition key of the vehicle is turned on, the initial SOC is estimated from the OCV measured at this time, and the current SOC is updated by a current integration method that integrates the current amount charged / discharged thereafter.

The equation for calculating the SOC by the current integration method in the battery SOC estimation process is shown in Equation (1) below.

However, according to several experiments and papers, it is not reliable to estimate SOC simply by continuously measuring OCV values because OCV changes with temperature and time.

In addition, OCV is not known when the battery is being charged or discharged, and since the chemistry inside the battery is not stabilized after a certain time (usually 2-3 hours or more) after charging / discharging is completed, SOC It cannot be estimated based on OCV.

Therefore, under the assumption that charging / discharging has been stopped for a sufficient time (assuming that the internal chemistry of the battery is stabilized), the OCV is measured immediately after the start-up key on, the initial SOC is estimated therefrom, and then the charge / discharge current is integrated to Updating SOC.

On the other hand, the current integration method is very useful for SOC estimation, but since it uses the initial SOC obtained from OCV immediately after starting, it continuously accumulates the amount of current during charging / discharging of the vehicle. The error gradually diverges or converges to zero due to the period (voltage drop due to battery aging, etc.).

In particular, when the charging / discharging is repeated, the actual charging / discharging efficiency changes in the battery, and when the charging / discharging frequently occurs during driving, the SOC that is accumulated and updated from the initial SOC immediately after startup is charged / discharged. As it progresses, the actual value is gradually different.

Therefore, in the low temperature range of the battery (-10 degrees or less), the current integration method is applied to overcome the shortcomings of the OCV estimation method, and when the battery temperature rises above a certain temperature (more than 0 degrees) as the battery is used, an OCV estimation cushion is generated. At the intermediate temperature (-10 degrees to 0 degrees), the SOC can be increased by adding a certain ratio of SOC obtained by current integration and a certain ratio of SOC obtained by OCV estimation.

(SOC = A x SOC_current integration + B x SOC_OCV estimate, A + B = 1)

Also, if the direction of current is reversed (charge / discharge) or the flow stops while applying OCV method, switch to current integration method (SOC = A x SOC_current integration + B x SOC_OCV estimation, A = 1, B = 0 As time goes by (e.g. as the battery is used, or when the voltage of the battery is below a predetermined value), A is decreased, B is increased to reduce the rate of dependence on the current integration method, and OCV estimation The ratio depending on the method is estimated by increasing.

Examples of the current integration method and the OCV method use and application ratio according to the battery temperature in the embodiment of the present invention are as follows.

     Battery temperature     Application of current integration method       OCV application rate       -Less than 10 degrees          100%            0%       -9 degrees           90%           10%       -8 degrees           80%           20%       -7 degrees           70%           30%       -6 degrees           60%           40%       -5 degrees           50%           50%       -4 degrees           40%           60%       -3 degrees           30%           70%       -2 degrees           20%           80%       -1 degree           10%           90%          0 degrees            0%          100%

3 is a flowchart illustrating an example of using the integrated accumulation method and the OCV method according to the battery temperature, and an application ratio thereof.

More specifically, in the low temperature region (for example, -10 degrees or less), the current integration method is applied to overcome the disadvantage of the OCV estimation method, and when the battery temperature rises above a predetermined temperature as the battery is used, the OCV estimation is performed. In the pre-determined temperature range, the SOC obtained by the current integration method and the SOC obtained by the OCV estimation method are summed (SOC = A x SOC_current integration + B x SOC_OCV estimation, A + B). = 1), which is a flowchart showing improvement in accuracy by obtaining an SOC.

In the above, the ratio of each other can be adjusted according to the temperature.

It demonstrates with reference to FIG.

Measure the temperature of the battery. (S 301).

If the measured temperature of the battery is below a predetermined temperature, the SOC is estimated based on the current integration method. (S 303, S 305).

On the other hand, as a result of the step determination, if the temperature of the battery is not less than the predetermined temperature, check whether the temperature of the battery is a predetermined temperature range, or if the temperature rises due to the use of the battery, the temperature range of the predetermined temperature range Check if it is (S 307).

As a result of the above check, if the temperature of the battery is within a predetermined temperature range, the predetermined ratio of SOC obtained by the current integration method and the predetermined ratio of SOC obtained by the OCV estimation method are summed (SOC = A x SOC_current integration + B x SOC_OCV). Estimate, A + B = 1) and SOC. (S 309).

On the other hand, if the temperature of the battery is not a predetermined temperature range as a result of the check, it is confirmed whether the temperature of the battery is more than the predetermined temperature to estimate the SOC by OCV. (S 311, S 313)).

FIG. 4 shows the SOC estimation by switching to the current integration method when the direction of the current is changed or the flow is interrupted based on the switching to charging / discharging during the SOC estimation by the OCV, and the temperature rises due to the use of the battery. As shown in Table 1, it is a flowchart showing estimating SOC by gradually increasing the ratio by the OCV method.

Referring to FIG. 4, the SOC of the battery is estimated based on the OCV method. (S 401).

If the direction of the current is reversed or the flow stops while estimating the SOC based on the OCV method, it is switched to the current integration method (SOC = A x SOC_current integration + B x SOC_OCV estimation, A = 1, B = 0). Estimate the SOC. (S 403, S 405)

After that, when the temperature of the battery increases due to the use of the battery, the SOC is estimated by increasing the ratio based on the OCV method and decreasing the ratio based on the current integration method. (S 407, S 409)

In other words, as the temperature of the battery increases with time, the ratio by the current integration method is lowered and the ratio by the OCV is increased.

The battery capacity state estimation method according to the embodiment can also be applied to general battery capacity estimation.

For example, the type of the battery 100 is not particularly limited and can be applied to a lithium ion battery, a lithium polymer battery, a nickel-cadmium battery, a nickel-hydrogen battery, a nickel-zinc battery, etc., .

Further, the technical idea of the present embodiment is not limited to the above-described embodiment and the attached drawings, but is construed according to the appended claims.

It will be apparent to those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims, As will be described below.

101: voltage sensing unit, 102: temperature sensing unit, 103: current sensing unit, 104: memory unit, 105: control unit

Claims (11)

A voltage sensing unit measuring a voltage value of the battery;
In the SOC estimation method using the OCV and current integration method, the SOC based on the current integration method is estimated below the predetermined battery temperature, and the SOC based on the OCV is estimated above the predetermined battery temperature. A temperature sensing unit for measuring the temperature of the battery to set the current integration method and the estimation by the OCV to be performed based on a predetermined ratio;
A current sensing unit for measuring the direction of the current to switch to the current integration method when the direction of the current changes or the flow is interrupted while the SOC estimation by the OCV is in progress, among the SOC estimation methods by the OCV and the current integration method;
A memory unit storing an associated table for applying an SOC to at least one of a battery temperature, a voltage value, a current value, a current direction, and a battery use time;
An SOC estimator for estimating the SOC under the control of the controller in each of the above cases;
An input unit / display unit for inputting a user command and outputting an estimated SOC result; And
And a controller for controlling the components and controlling SOC estimation by OCV at an operation time of a predetermined battery.
The battery capacity state estimation apparatus according to claim 1, wherein the SOC is estimated based on a current integration method at -10 degrees or less which is a predetermined temperature.
The battery capacity state estimation apparatus according to claim 1, wherein the SOC is estimated based on OCV at a temperature equal to or greater than 0 degree which is a predetermined temperature.
The apparatus of claim 1, wherein the SOC is estimated by applying a current integration method and an OCV method at a predetermined ratio within a predetermined range of −10 to 0 degrees.
Estimating an initial SOC of the battery based on the OCV method;
Estimating the SOC based on the current integration method when the temperature of the battery is less than or equal to a predetermined temperature;
If the temperature of the battery is a predetermined temperature range, the SOC is estimated while the current integration method and the OCV method are variably applied at a predetermined ratio in response to the temperature change; And
Estimating the SOC based on the OCV method when the temperature of the battery is greater than or equal to a predetermined temperature.
The method of claim 5, wherein the initial SOC of the battery is an SOC initially detected when the battery has not been operated for a predetermined time.
6. The method of claim 5, wherein the SOC is estimated as the ratio of the battery increases in proportion to the OCV method as the temperature increases.
Estimating the SOC of the battery based on the OCV method;
Checking whether the flow direction of the current is changed; And
And determining the SOC based on the current integration method when the current flow direction is changed as a result of the checking.
The method of claim 8, further comprising: estimating the SOC while the temperature of the battery rises and the current integration method and the OCV method are variably applied at a predetermined ratio in response to the temperature change; The battery capacity state estimation method further comprises.
10. The method of claim 9, wherein the SOC is estimated in a predetermined temperature range of the battery while decreasing the ratio by the current integrating method as the temperature increases.
9. The method of claim 8, wherein changing the current flow direction includes at least one of changing the current flow direction and stopping the current flow.

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