KR102695066B1 - Apparatus and method for monitoring state of ess - Google Patents

Abstract

A battery condition monitoring device and method are proposed to check the deterioration status of a battery in real time and to correct the state of charge. The proposed battery condition monitoring device and method measure the microcapacity of a battery based on the terminal voltage of the battery, estimate the discharge capacity of the battery using the microcapacity and a linear regression model, and estimate and update the state of charge of the battery based on the SOC function and the estimated discharge capacity.

Description

{APPARATUS AND METHOD FOR MONITORING STATE OF ESS}

The present invention relates to a battery status monitoring device and method, and more particularly, to a battery status monitoring device and method for monitoring the battery status of an energy storage system (ESS).

Recently, fires in energy storage systems (ESS) have been occurring frequently, but the exact cause of the fires has not been identified. Some believe that the cause is a malfunction of the battery, power conversion system (PCS), or battery management system (BMS).

In general, energy storage devices are composed of a plurality of lithium secondary batteries in a series-parallel combination. If, due to battery aging, deviations in capacity, inter-cell voltage, and state of charge (SOC) occur in the series-parallel combination, and some of the cells among the plurality of cells operate abnormally, those some of the cells may be at risk of overcharge and overdischarge. Referring to FIGS. 1 and 2, due to those some of the cells, the entire battery pack may experience performance degradation (i.e., reduction in battery operation range) and, in severe cases, may be at risk of explosion and fire.

Since batteries have a sealed structure and indicators of their condition vary depending on the chemical state inside, there is a lack of technology to precisely monitor and analyze the condition of the battery.

Since the state of charge (SOC) and state of health (SOH) are determined by the chemical state inside the battery, it is difficult to accurately measure SOC and SOH from the outside. Due to this measurement difficulty, estimation techniques rather than measurement techniques have been introduced for battery SOC and SOH.

The most commonly known SOC estimation method is the current integration method. The current integration method is based on the definition of SOC and is a method of counting the total amount of charge that the battery can output, calculating the battery output current by integrating it over time.

In particular, the method of integrating current while discharging at a constant current is the most accurate method for estimating SOC, and the SOC estimated by this current integration method is used as a reference value for evaluating the accuracy of SOC measured by other methods.

However, the SOC estimation by the current integration method has the disadvantage of taking a long time to obtain the result value, and if all the current input and output to the battery is integrated rather than the current discharged at a constant current, there is also the problem that the accuracy of the SOC is lower than that of other methods due to error accumulation.

As an alternative to the problems of the current integration method, the OCV (open circuit voltage) method has been proposed. The OCV method is a method of estimating the SOC using the terminal voltage of the battery in a state where there is no current input or output to the battery. It has the advantage of being able to measure the SOC without consuming the charge stored inside the battery, and when the battery has not been charged or discharged for a long time, the accuracy of SOC estimation by the OCV method is known to be higher than that by the current integration method.

However, the OCV method has a problem in that it cannot estimate the state of charge in real time using only the OCV method because the accuracy is high only when the battery is in a stable state and the accuracy is low when the battery is in an unstable state.

There is a need to develop a technology that can improve the problems of these conventional methods and estimate SOC in real time with higher accuracy.

In addition, the SOH changes depending on the use of the battery, and this change in SOH also affects the SOC. Accordingly, the development of technology that can estimate SOH more accurately is required for more accurate estimation of SOC and accurate recognition of the battery condition.

Existing SOC and SOH estimation technologies can cause incorrect status judgments as errors in measurement and battery status estimation accumulate, putting the battery at risk of overcharge, overdischarge, and explosion. To address this, existing technologies update the battery status by identifying the performance status offline.

The present invention has been proposed to solve the above-mentioned conventional problems, and aims to provide a battery status monitoring device and method that can check the deterioration status of a battery in real time and correct the charging status.

That is, the present invention aims to provide a battery status monitoring device and method that determines the deterioration status of a battery through microcapacitance in a specific terminal voltage range that can explain the discharge capacity, and corrects the charge status in real time with higher accuracy than existing technologies to more accurately determine the battery deterioration status.

In order to achieve the above object, a battery state monitoring device according to an embodiment of the present invention includes a storage unit that stores a SOC function for estimating a state of charge of a battery, an acquisition unit that acquires charge/discharge current and terminal voltage of the battery, a micro-capacity measurement unit that measures a micro-capacity of the battery based on the terminal voltage acquired by the acquisition unit, a discharge capacity estimation unit that estimates a discharge capacity of the battery using the micro-capacity measured by the micro-capacity measurement unit and a linear regression model, a SOC estimation unit that estimates a state of charge of the battery based on the SOC function and the discharge capacity estimated by the discharge capacity estimation unit, and a SOC update unit that updates the SOC function stored in the storage unit based on the discharge capacity estimated by the discharge capacity estimation unit.

The storage unit can store one of the following functions as the SOC function: an accumulation function including the initial state of charge of the battery, the charge/discharge current, and the discharge capacity as factors; and an open circuit voltage function, which is the terminal voltage of the battery after the charge/discharge current is in a state of zero for a set period of time.

The microcapacity measuring unit can measure microcapacity by accumulating the charge/discharge current acquired from the acquisition unit in a preset voltage range for the terminal voltage acquired from the acquisition unit. At this time, the microcapacity measuring unit varies the voltage range based on the size of the charge/discharge current, and the charge/discharge current has a fixed value within the error range when measuring microcapacity.

The storage unit further stores an SOH function for estimating the deterioration state of the battery, and the SOH function may include the initial discharge capacity and the current discharge capacity of the battery as factors.

The battery condition monitoring device according to an embodiment of the present invention may further include an SOH estimation unit that estimates the deterioration state of the battery based on the SOH function stored in the storage unit. At this time, the SOH estimation unit can estimate the discharge capacity of the battery by substituting the initial discharge capacity and the current discharge capacity among the discharge capacities of the battery estimated by the discharge capacity estimation unit into the SOH function.

The battery status monitoring device according to an embodiment of the present invention may further include an internal resistance measuring unit that measures the internal resistance of the battery based on the amount of change in the step current and terminal voltage of the battery. At this time, the discharge capacity estimation unit may estimate the discharge capacity of the battery based on the internal resistance measured by the internal resistance measuring unit and the linear regression model.

In order to achieve the above object, a battery status monitoring method according to an embodiment of the present invention includes the steps of acquiring charge/discharge current and terminal voltage of a battery, measuring a micro-capacity of the battery based on the terminal voltage acquired in the acquiring step, estimating a discharge capacity of the battery using the measured micro-capacity and a linear regression model in the micro-capacity measuring step, estimating a state of charge of the battery based on a stored SOC function and the estimated discharge capacity in the discharge capacity estimation step, and updating the SOC function based on the estimated discharge capacity in the discharge capacity estimation step.

At this time, the SOC function may be one of a function of an accumulation function that includes the initial state of charge of the battery, the charge/discharge current, and the discharge capacity as factors, and an open circuit voltage function that is the terminal voltage of the battery after the charge/discharge current is in a state of zero for a set time.

In the step of measuring the microcapacitance, the microcapacitance can be measured by accumulating the charge/discharge current acquired in the step of acquiring in a preset voltage range for the terminal voltage acquired in the step of acquiring. At this time, the step of measuring the microcapacitance includes a step of varying the voltage range based on the size of the charge/discharge current, and the charge/discharge current has a fixed value within the error range when measuring the microcapacitance.

The battery condition monitoring method according to an embodiment of the present invention may further include a step of estimating the deterioration state of the battery based on the SOH function. At this time, the SOH function includes the initial discharge capacity and the current discharge capacity of the battery as factors, and in the step of estimating the deterioration state, the initial discharge capacity and the current discharge capacity among the discharge capacities of the battery estimated in the step of estimating the discharge capacity are substituted into the SOH function to estimate the deterioration state of the battery.

The battery status monitoring method according to an embodiment of the present invention may further include a step of measuring the internal resistance of the battery based on the amount of change in the step current and terminal voltage of the battery. At this time, in the step of estimating the discharge capacity, the discharge capacity of the battery can be estimated based on the internal resistance measured in the step of measuring the internal resistance and the linear regression model.

According to the present invention, the battery condition monitoring device and method have the effect of being able to measure SOC reflecting aging in real time in estimating the battery condition.

In addition, the battery condition monitoring device and method have the effect of more accurately estimating the state of health (SOH) of the battery compared to the conventional method in estimating the battery condition.

In addition, while conventionally, the aged battery capacity was judged by performing full charge and full discharge offline and the aged battery capacity was applied to reflect the aging of the battery, the battery condition monitoring device and method can diagnose the deterioration condition of the battery through microcapacity and internal resistance even while the battery is in operation.

In addition, the battery condition monitoring device and method are effective in preventing battery accidents by diagnosing the condition of deterioration even when the battery is in operation.

In addition, the battery condition monitoring device and method have the effect of accurately monitoring the condition and lifespan of the battery by estimating a more accurate state of charge and deterioration state using a statistical model.

Figures 1 and 2 are drawings for explaining the risk of explosion and fire of a battery pack included in a typical energy storage device.
FIG. 3 is a drawing for explaining a battery system to which a battery status monitoring device according to an embodiment of the present invention is applied.
FIG. 4 is a drawing for explaining a battery status monitoring device according to an embodiment of the present invention.
Figures 5 and 6 are drawings for explaining the microcapacitance measuring unit of Figure 4.
Figures 7 to 11 are drawings for explaining the discharge capacity estimation unit of Figure 4.
FIG. 12 is a drawing for explaining a modified example of a battery status monitoring device according to an embodiment of the present invention.
FIG. 13 and FIG. 14 are flowcharts for explaining a battery status monitoring method according to an embodiment of the present invention.
FIG. 15 is a flowchart for explaining a SOC estimation and correction method of a battery status monitoring method according to an embodiment of the present invention.
FIG. 16 is a flowchart for explaining a SOH estimation method of a battery condition monitoring method according to an embodiment of the present invention.
Figures 17 to 21 are drawings for explaining the discharge capacity estimation step of Figure 16.
FIG. 22 is a flowchart illustrating a modified example of a battery status monitoring method according to an embodiment of the present invention.

Hereinafter, in order to explain in detail the technical idea of the present invention to a degree that a person having ordinary skill in the art to which the present invention pertains can easily practice the present invention, the most preferred embodiment of the present invention will be described with reference to the accompanying drawings. First, when adding reference symbols to components in each drawing, it should be noted that the same components are given the same symbols as much as possible even if they are shown in different drawings. In addition, when explaining the present invention, if it is determined that a specific description of a related known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted.

First, a battery system to which a battery status monitoring device according to an embodiment of the present invention is applied will be described with reference to the attached drawings as follows. FIG. 3 is a drawing for explaining a battery system to which a battery status monitoring device according to an embodiment of the present invention is applied.

Referring to FIG. 3, the battery system is configured to include a battery (10), a load (20), a charger (30), and a battery status monitoring device (100).

The battery (10) converts electrical energy into chemical energy or converts chemical energy into electrical energy. Examples of the battery (10) include a lithium ion battery, a lithium polymer battery, etc.

The battery (10) includes at least two terminals. A voltage having a negative (-) polarity can be supplied to the first terminal, and a voltage having a positive (+) polarity can be supplied to the second terminal.

Hereinafter, the voltage between a terminal with a negative (-) polarity and a terminal with a positive (+) polarity is defined as the terminal voltage (Vb). The current flowing in and out through the terminal of the battery (10) is defined as the charge/discharge current (Ib). Hereinafter, for convenience of explanation, the current input to the terminal of the battery (e.g., charge current) is defined in the positive (+) direction, and the current supplied externally from the terminal of the battery (e.g., discharge current) is defined in the negative (-) direction.

The load (20) operates using the discharge current of the battery (10). The load (20) receives power from the charger (30) at a time when the charger (30) supplies power. The load (20) operates using the discharge current of the battery (10) at a time when the charger (30) does not supply power.

The charger (30) converts external power and supplies it to the battery (10). The charger (30) has a built-in device called a power conversion device or converter.

The battery condition monitoring device (100) estimates the SOC and SOH of the battery (10). The battery condition monitoring device (100) monitors the charge/discharge current (Ib) and terminal voltage (Vb) of the battery (10), and estimates the state of charge (SOC) and state of deterioration (SOH) of the battery (10) using these values.

Hereinafter, a battery status monitoring device according to an embodiment of the present invention will be described in detail with reference to the attached drawings.

The battery condition monitoring device (100) determines the deterioration state of the battery and updates the SOC function. That is, the battery condition monitoring device (100) monitors the charge/discharge current and terminal voltage of the battery. The battery condition monitoring device (100) estimates the SOC using the SOC (state-of-charge) function that uses the discharge capacity as a factor. The battery condition monitoring device (100) accumulates the charge/discharge current within a preset range for the measured terminal voltage to measure the microcapacity. At this time, the charge/discharge current in the microcapacity range of the battery condition monitoring device (100) may have a constant size or a size within a constant deviation. Accordingly, the range of the microcapacity may be set differently depending on the size of the charge/discharge current.

The battery condition monitoring device (100) estimates the discharge capacity using a linear regression model that calculates the discharge capacity by using the measured microcapacity as a factor. The battery condition monitoring device (100) determines the deterioration of the battery using the estimated discharge capacity. At this time, the battery condition monitoring device (100) applies the measured microcapacity and total capacity using the monitored charge/discharge current and terminal voltage to the linear regression model, and estimates the discharge capacity using the microcapacity to determine the deterioration of the battery.

The battery condition monitoring device (100) updates the SOC function to correct the charging state of the battery. At this time, the battery condition monitoring device (100) corrects the SOC function by using the estimated discharge capacity and the accumulated value of the charge/discharge current over time.

To this end, referring to FIG. 4, the battery status monitoring device (100) is configured to include a storage unit (110).

The storage unit (110) stores a SOC function for estimating the state of charge (SOC). The storage unit (110) stores a SOC function (see Mathematical Formula 1 below), which is a current accumulation function.

Here, SOCi is the initial state of charge, Ib is the charge/discharge current, and Cn is the discharge capacity.

The SOC function (i.e., current accumulation function) calculates the state of charge (SOC) by dividing the accumulated charge/discharge current (Ib) over time by the discharge capacity (Cn). The SOC function includes the discharge capacity (Cn) as a factor.

The SOC function may also be an OCV (open circuit voltage) function. The OCV function may be a terminal voltage measured when the internal state of the battery (10) is stable after the charge/discharge current (Ib) has been in a zero state for a certain period of time. The OCV function is a function that matches the relationship between OCV and SOC as a 1:1 function.

When the SOC function is a current integration function, the discharge capacity (Cn) is used in the numerator. When the discharge capacity (Cn) is used as a factor in the SOC function, the estimated state of charge (SOC) also changes according to the change in the discharge capacity (Cn). For example, when the SOC function is a current integration function, if the discharge capacity (Cn) changes, the numerator may change, which may cause the state of charge (SOC) to change.

When the SOC function is an OCV function, the SOC function can be generated in a form in which the OCV function changes according to the discharge capacity (Cn). Even when the SOC function is an OCV function, the OCV function (i.e., the OCV curve) fluctuates according to the discharge capacity (Cn), and the state of charge (SOC) estimated from it fluctuates.

The storage unit (110) stores a SOH function for estimating the state of degradation (SOH). As an example, the storage unit (110) stores an SOH function defined as in the following mathematical expression 2.

Here, Cni is the initial discharge capacity, which can be measured collectively when the battery (10) is shipped from the factory. Cnc can be defined as the current discharge capacity. For example, the final discharge capacity (Cnf) can be defined as 80% of the initial discharge capacity (Cni).

The battery monitoring device further includes an acquisition unit (120) that acquires the charge/discharge current and terminal voltage of the battery. The acquisition unit (120) is configured to include a current sensor for measuring the charge/discharge current and a voltage sensor for measuring the terminal voltage. At this time, the charge/discharge current flowing into and out of the battery is measured using the current sensor, and the terminal voltage of the battery is measured using the voltage sensor.

The battery monitoring device further includes a microcapacity measuring unit (130) that measures microcapacity using the terminal voltage acquired from the acquisition unit (120).

The micro-capacity measuring unit (130) measures the micro-capacity by accumulating the charge and discharge current in a preset range (i.e., voltage range) for the terminal voltage of the battery acquired from the acquisition unit (120). For example, the micro-capacity measuring unit (130) measures the micro-capacity by accumulating the charge and discharge current from when the terminal voltage of the battery is approximately 3.5 V to approximately 3.6 V. At this time, the micro-capacity measuring unit (130) can preset the lower voltage (i.e., 3.5 V) and the upper voltage (i.e., 3.6 V) of the voltage range.

The charge/discharge current when measuring microcapacitance can have a constant size or a size within a certain deviation. For example, when measuring microcapacitance, the charge/discharge current maintains a size of 1A or a size within a certain error range from 1A.

Meanwhile, referring to FIG. 5, when measuring microcapacity, the capacity may vary depending on the size of the charge/discharge current, and thus the range of the microcapacity may also vary. Accordingly, the microcapacity measuring unit (130) may set the voltage range for measuring the microcapacity differently depending on the size of the charge/discharge current. That is, the microcapacity measuring unit (130) may set the voltage range for measuring the microcapacity differently when the charge/discharge current is 1 A and when the charge/discharge current is 2 A.

Referring to FIG. 6, the battery (10) can be modeled as an inductor (L), a first internal resistance (Ri1), a second internal resistance (Ri2), an electric double layer (Cdl), a diffusion layer (Zw), and an OCV (OCV).

When a charge/discharge current (Ib) flows into and out of a battery (10), a voltage is formed across the first internal resistance (Ri1) and the second internal resistance (Ri2) depending on the size of the charge/discharge current (Ib), and the terminal voltage (Vb) of the battery (10) also fluctuates depending on the fluctuation of this voltage.

When the charge/discharge current (Ib) has a constant value for a constant period of time as a direct current, the inductor (L), electric double layer (Cdl), and diffusion layer (Zw) are ignored, and the terminal voltage (Vb) changes only by the first internal resistance (Ri1) and the second internal resistance (Ri2). The microcapacity measuring unit (130) sets the voltage range in which the microcapacity is measured differently according to the size of the charge/discharge current according to the circuit model of the battery.

In practice, the microcapacity measuring unit (130) can measure the microcapacity by accumulating the charge/discharge current (Ib) in a preset OCV range for the OCV (OCV). At this time, since it is difficult for the microcapacity measuring unit (130) to directly determine the OCV, the voltage range is set as a terminal voltage as an alternative to the OCV (OCV). Here, the microcapacity measuring unit (130) sets the voltage range differently according to the size of the charge/discharge current, and the size of the charge/discharge current can be the charge/discharge current at the start and end points of measuring the microcapacity.

The battery monitoring device further includes a discharge capacity estimation unit (140) that estimates the discharge capacity using the microcapacity measured by the microcapacity measurement unit (130) and a linear regression model.

The discharge capacity estimation unit (140) estimates the discharge capacity using a linear regression model that calculates the discharge capacity by using the microcapacity measured by the microcapacity measurement unit (130) as a factor.

Referring to FIGS. 7 and 8, a certain relationship is established between the microcapacity and the discharge capacity. FIG. 7 shows a conceptual diagram of a linear regression model between the microcapacity and the discharge capacity, and illustrates a schematic diagram of a linear regression model between the microcapacity and the discharge capacity established using experimental data of the microcapacity and the total capacity. FIG. 8 illustrates a linear regression model used for the microcapacity and the discharge capacity according to aging.

The linear regression model for estimating the discharge capacity can be expressed as in the following mathematical equations 3 and 4. At this time, the coefficients of the regression model are determined by the least squares method. The least squares method produces regression coefficients that minimize the sum of squares of the errors (SSE, mathematical equation 4).

Here, is the estimated data of discharge capacity, and is the regression coefficient calculated by the least squares method, is the actual data of microcapacity, is the actual data of discharge capacity, refers to the residual, which is the difference between the estimated value and the actual value.

The discharge capacity estimation unit (140) measures the discharge capacity in real time using the linear regression model described above.

Meanwhile, conditions for measuring microcapacity (e.g., conditions for charge/discharge current and conditions for voltage range) may be intentionally satisfied by the charger, but the discharge capacity estimation unit (140) searches for a partial situation that satisfies the conditions for measuring microcapacity in a situation arbitrarily formed by the load or the charger, and estimates the discharge capacity in that situation.

The voltage range for measuring microcapacitance can be set to a range that occurs frequently depending on the load and charger conditions, or it can be set by finding a range with a high correlation between microcapacitance and discharge capacity.

Figures 9 and 10 are examples of the estimation performance for the linear regression model of the microcapacity and discharge capacity according to the cycle, and it can be seen that the estimation performance is within about 0.5%.

Referring to Fig. 11, which is a graph matching the correlation between microcapacitance and discharge capacity in the terminal voltage range through an experiment, it was confirmed that the correlation between microcapacitance (horizontal axis) and discharge capacity (vertical axis) was high in a specific voltage range (approximately in the range of 3.6 V to 3.7 V) among many voltage ranges. Through an experiment, a user can search for a range in which the correlation between microcapacitance and discharge capacity is high and set the voltage range to that range.

The discharge capacity estimation unit (140) may also measure the initial discharge capacity, which is the discharge capacity of the initial state of the battery. At this time, the measurement of the initial discharge capacity may be performed according to the definition of the discharge capacity. The measurement of the initial discharge capacity may be performed by a device other than the discharge capacity estimation unit (140) (for example, a test device in a factory). At this time, the discharge capacity estimation unit (140) receives a value for the initial discharge capacity from another device by an appropriate input device and stores it.

The discharge capacity estimation unit (140) can estimate the current discharge capacity, which is the discharge capacity in the current state, by using the microcapacity measured by the microcapacity measurement unit (130) and a linear regression model.

The battery monitoring device further includes a SOC estimation unit (150) that estimates the state of charge of the battery using the SOC function stored in the storage unit (110).

The SOC estimation unit (150) detects a SOC function that uses the discharge capacity as a factor from the storage unit (110). The SOC estimation unit (150) estimates the state of charge of the battery using the detected SOC function. At this time, the SOC estimation unit (150) estimates the state of charge of the battery using the SOC function, which is one of the current accumulation function that calculates the accumulated value of the charge/discharge current over time by dividing it by the discharge capacity or the OCV function that includes a different OCV curve depending on the discharge capacity.

The battery monitoring device further includes a SOC update unit (160) that updates the SOC function stored in the storage unit (110) using the discharge capacity estimated by the discharge capacity estimation unit (140).

The battery monitoring device may further include an SOH estimation unit (170) that estimates the deterioration state of the battery by using the initial discharge capacity and the current discharge capacity estimated by the discharge capacity estimation unit (140). At this time, the SOH estimation unit (170) estimates the deterioration state of the battery by comparing the current discharge capacity estimated by the discharge capacity estimation unit (140) to the initial discharge capacity.

Meanwhile, the battery monitoring device can estimate the discharge capacity using the internal resistance when it cannot measure the microcapacity. To this end, as shown in Fig. 12, the battery monitoring device can further include an internal resistance measuring unit (180) that measures the internal resistance of the battery.

The internal resistance measuring unit (180) can measure the internal resistance through the step current. The battery condition monitoring device (100) measures the internal resistance by using the amount of change in the size of the step current and the amount of change in the terminal voltage according to it. The step current can have the characteristics of a direct current in a certain section immediately before and after the size changes. The internal resistance measuring unit (180) measures only the internal resistance by excluding the inductor, electric double layer, and diffusion layer with reference to the battery circuit model (Fig. XX) according to the characteristics of the step current.

The discharge capacity estimation unit (140) configures the correlation between the internal resistance (Ri) and the discharge capacity (Cn) as a linear regression model. At this time, the discharge capacity estimation unit (140) estimates the discharge capacity (Cn) by inputting the internal resistance (Ri) of the battery measured in real time by the internal resistance measurement unit (180) into the configured linear regression model.

The discharge capacity estimation unit (140) may estimate the discharge capacity using a linear regression model that includes microcapacitance and internal resistance as factors. The discharge capacity estimation unit (140) may configure a linear regression model so that microcapacitance and internal resistance are mutually related according to experimental data, or may configure the linear regression model independently of each other.

Hereinafter, a battery status monitoring method according to an embodiment of the present invention will be described in detail with reference to the attached drawings. FIG. 13 and FIG. 14 are drawings for explaining a battery status monitoring method according to an embodiment of the present invention.

Referring to FIGS. 13 and 14, the battery status monitoring device (100) monitors the charge/discharge current and terminal voltage of the battery (S110).

The battery condition monitoring device (100) estimates the state of charge (SOC) using a state-of-charge (SOC) function that uses discharge capacity as a factor (S120).

The battery condition monitoring device (100) measures the micro-capacity by accumulating the charge/discharge current within a preset range for the measured terminal voltage (S130). At this time, the charge/discharge current in the micro-capacity range may have a constant size or a size within a certain deviation. Accordingly, the battery condition monitoring device (100) may set the micro-capacity range differently depending on the size of the charge/discharge current.

The battery condition monitoring device (100) estimates the discharge capacity using a linear regression model that calculates the discharge capacity by using the measured microcapacity as a factor (S140).

The battery condition monitoring device (100) determines the deterioration of the battery using the estimated discharge capacity (S150). At this time, the battery condition monitoring device (100) applies the measured micro-capacity and total capacity using the monitored charge/discharge current and terminal voltage to a linear regression model, and estimates the discharge capacity using the micro-capacity to determine the deterioration of the battery.

The battery condition monitoring device (100) updates the SOC function to correct the charging state of the battery (S160). At this time, the battery condition monitoring device (100) corrects the SOC function by using the estimated discharge capacity and the accumulated value of the charge/discharge current over time.

Hereinafter, the SOC estimation and correction method of the battery condition monitoring method according to an embodiment of the present invention will be described in detail with reference to the attached drawings. FIG. 15 is a flowchart for explaining the SOC estimation and correction method of the battery condition monitoring method according to an embodiment of the present invention.

Referring to FIG. 15, the battery status monitoring device (100) monitors the charge/discharge current and terminal voltage of the battery (S210). At this time, the battery status monitoring device (100) includes a current sensor for measuring the charge/discharge current and a voltage sensor for measuring the terminal voltage. That is, the battery status monitoring device (100) measures the charge/discharge current flowing into and out of the battery using the current sensor, and measures the terminal voltage of the battery using the voltage sensor.

The battery condition monitoring device (100) estimates the state of charge of the battery by using the SOC function that uses the discharge capacity as a factor (S220). At this time, the battery condition monitoring device (100) estimates the state of charge of the battery by using the SOC function that uses the discharge capacity as a factor. Here, the SOC function may be a current accumulation function that calculates by dividing the value of the charge/discharge current accumulated over time by the discharge capacity.

Meanwhile, the battery condition monitoring device (100) can also estimate the state of charge of the battery by using the SOC function composed of the OCV function. At this time, the SOCV function includes different OCV curves depending on the discharge capacity.

The battery condition monitoring device (100) measures microcapacity (S230). That is, the battery condition monitoring device (100) measures microcapacity by accumulating charge and discharge current within a preset range (i.e., voltage range) for terminal voltage. At this time, the charge and discharge current within the voltage range may have a constant size or a size within a constant deviation. Accordingly, the battery condition monitoring device (100) may set the voltage range for measuring microcapacity differently depending on the size of the charge and discharge current.

The battery condition monitoring device (100) estimates the discharge capacity using the microcapacity measured in step S230 and the linear regression model (S240). That is, the battery condition monitoring device (100) estimates the discharge capacity using a linear regression model that calculates the discharge capacity using the microcapacity as a factor.

The battery condition monitoring device (100) updates the SOC function using the discharge capacity estimated in step S240 (S250). Thereafter, the battery condition monitoring device (100) continuously estimates the state of charge of the battery by continuously repeating steps S210 to S250.

Hereinafter, the SOH estimation method of the battery condition monitoring method according to an embodiment of the present invention will be described in detail with reference to the attached drawings. FIG. 16 is a flowchart for explaining the SOH estimation method of the battery condition monitoring method according to an embodiment of the present invention.

Referring to FIG. 16, the battery status monitoring device (100) monitors the charge/discharge current and terminal voltage of the battery (S310). At this time, the battery status monitoring device (100) includes a current sensor for measuring the charge/discharge current and a voltage sensor for measuring the terminal voltage. That is, the battery status monitoring device (100) measures the charge/discharge current flowing into and out of the battery using the current sensor, and measures the terminal voltage of the battery using the voltage sensor.

The battery condition monitoring device (100) measures the initial discharge capacity, which is the discharge capacity of the initial state of the battery (S320). That is, the measurement of the initial discharge capacity can be performed according to the definition of the discharge capacity. The measurement of the initial discharge capacity can be performed by a device other than the battery condition monitoring device (100) (e.g., a test device in a factory). In this case, the battery condition monitoring device (100) receives the value of the initial discharge capacity from the other device by an appropriate input device and stores it.

The battery condition monitoring device (100) measures microcapacity (S330). That is, the battery condition monitoring device (100) measures microcapacity by accumulating charge and discharge current within a preset range (i.e., voltage range) for terminal voltage. At this time, the charge and discharge current within the voltage range may have a constant size or a size within a constant deviation. Accordingly, the battery condition monitoring device (100) may set the voltage range for measuring microcapacity differently depending on the size of the charge and discharge current.

The battery condition monitoring device (100) estimates the current discharge capacity, which is the discharge capacity in the current state, using the microcapacity measured in step S330 and the linear regression model (S340). That is, the battery condition monitoring device (100) estimates the discharge capacity using a linear regression model that calculates the discharge capacity using the microcapacity as a factor.

The battery condition monitoring device (100) estimates the deterioration state of the battery using the initial discharge capacity and the current discharge capacity (S350). That is, the battery condition monitoring device (100) estimates the deterioration state of the battery by comparing the current discharge capacity estimated in step S340 with the initial discharge capacity measured in step S320.

Meanwhile, in Fig. 16, the battery condition monitoring device (100) may estimate the discharge capacity using internal resistance if it is unable to measure the microcapacity at step S330.

The battery condition monitoring device (100) configures a linear regression model for the correlation between the internal resistance (Ri) and the discharge capacity (Cn) (see FIGS. 17 to 20). The battery condition monitoring device (100) estimates the discharge capacity (Cn) by inputting the internal resistance (Ri) measured in real time from the battery into the configured linear regression model. At this time, the battery condition monitoring device (100) estimates the discharge capacity using a linear regression model that includes both the microcapacity and the internal resistance as factors. The battery condition monitoring device (100) may configure a linear regression model so that the microcapacity and the internal resistance are mutually correlated according to experimental data, or may configure the linear regression model independently of each other.

The battery condition monitoring device (100) can measure internal resistance through a step current. The step current can have the characteristics of a direct current in a certain section immediately before and after the size changes. The battery condition monitoring device (100) can measure only the internal resistance, excluding the inductor, electric double layer, and diffusion layer in the battery circuit model (see FIG. 6), according to the characteristics of this step current.

As shown in Figure 21, the estimated error of the discharge capacity estimated through the internal resistance applied to the linear regression model is shown. The discharge capacity can be used as an indicator of the deterioration state, so its error is the same as the error in judging the deterioration state.

Hereinafter, a modified example of a battery status monitoring method according to an embodiment of the present invention will be described in detail with reference to the attached drawings. FIG. 22 is a flowchart for explaining a modified example of a battery status monitoring method according to an embodiment of the present invention.

Referring to FIG. 22, the battery status monitoring device (100) can monitor the charge/discharge current and terminal voltage of the battery (S410). At this time, the battery status monitoring device (100) includes a current sensor for measuring the charge/discharge current and a voltage sensor for measuring the terminal voltage. That is, the battery status monitoring device (100) measures the charge/discharge current flowing into and out of the battery using the current sensor, and measures the terminal voltage of the battery using the voltage sensor.

The battery condition monitoring device (100) estimates the state of charge of the battery by using the SOC function that uses the discharge capacity as a factor (S420). At this time, the battery condition monitoring device (100) estimates the state of charge of the battery by using the SOC function that uses the discharge capacity as a factor. Here, the SOC function may be a current accumulation function that calculates by dividing the value of the charge/discharge current accumulated over time by the discharge capacity.

Meanwhile, the battery condition monitoring device (100) can also estimate the state of charge of the battery by using the SOC function composed of the OCV function. At this time, the SOCV function includes different OCV curves depending on the discharge capacity.

The battery condition monitoring device (100) measures microcapacity by accumulating charge and discharge current in a preset range (i.e., voltage range) for the terminal voltage (S430). That is, the battery condition monitoring device (100) measures microcapacity by accumulating charge and discharge current in a preset range (i.e., voltage range) for the terminal voltage. At this time, the charge and discharge current within the voltage range may have a constant size or a size within a constant deviation. Accordingly, the battery condition monitoring device (100) may set the voltage range for measuring microcapacity differently depending on the size of the charge and discharge current.

The battery status monitoring device (100) measures internal resistance (S440). At this time, the battery status monitoring device (100) measures internal resistance using the amount of change in the size of the step current and the amount of change in the terminal voltage according to it.

The battery condition monitoring device (100) estimates the discharge capacity by applying the estimated or measured micro-capacity and internal resistance to a linear regression model that calculates the discharge capacity using the micro-capacity and internal resistance as factors (S450).

The battery condition monitoring device (100) updates the SOC function with the estimated discharge capacity and estimates the deterioration state (S910). Through this, the battery condition monitoring device (100) can estimate the state of charge of the battery with higher accuracy in real time. In addition, the battery condition monitoring device (100) can estimate the deterioration state reflecting the aging of the battery more accurately.

Although the preferred embodiments of the present invention have been described above, it is understood that various modifications may be made, and that those skilled in the art will be able to make various modifications and variations without departing from the scope of the claims of the present invention.

10: Battery 20: Load
30: Charger 100: Battery status monitoring device
110: Storage section 120: Acquisition section
130: Micro-capacity measuring section 140: Discharge capacity estimation section
150: SOC Estimation Section 160: SOC Renewal Section
170: SOH estimation section 180: Internal resistance measurement section

Claims (20)

A storage unit that stores the SOC function for estimating the state of charge of the battery;
An acquisition unit that acquires the charge/discharge current and terminal voltage of the above battery;
A micro-capacity measuring unit for measuring the micro-capacity of the battery based on the terminal voltage acquired from the above acquisition unit;
A discharge capacity estimation unit that estimates the discharge capacity of the battery using the micro-capacity measured by the micro-capacity measuring unit and a linear regression model;
A SOC estimation unit that estimates the state of charge of the battery based on the discharge capacity estimated by the SOC function and the discharge capacity estimation unit; and
A battery status monitoring device including a SOC update unit that updates the SOC function stored in the storage unit based on the discharge capacity estimated by the discharge capacity estimation unit. In the first paragraph,
The above storage unit is a battery state monitoring device that stores one of a storage function including an initial charge state of the battery, a charge/discharge current, and a discharge capacity as factors, and an open circuit voltage function, which is a terminal voltage of the battery after the charge/discharge current is in a state of zero for a set period of time, as a SOC function. In the first paragraph,
The above micro-capacity measuring unit is a battery status monitoring device that measures micro-capacity by accumulating the charge/discharge current acquired from the acquisition unit in a preset voltage range for the terminal voltage acquired from the acquisition unit. In the third paragraph,
The above microcapacity measuring unit is a battery status monitoring device that varies the voltage range based on the size of the charge/discharge current. In the third paragraph,
The above charging/discharging current is a battery status monitoring device having a fixed value within the error range when measuring the microcapacity. In the first paragraph,
The above storage unit further stores an SOH function for estimating the deterioration state of the battery,
The above SOH function is a battery condition monitoring device that includes the initial discharge capacity and the current discharge capacity of the battery as factors. In the first paragraph,
A battery condition monitoring device further comprising an SOH estimation unit that estimates the deterioration state of the battery based on the SOH function stored in the storage unit. In Article 7,
The above SOH estimation unit is a battery condition monitoring device that estimates the deterioration state of the battery by substituting the initial discharge capacity and the current discharge capacity among the discharge capacities of the battery estimated by the discharge capacity estimation unit into the SOH function. In the first paragraph,
A battery status monitoring device further comprising an internal resistance measuring unit that measures the internal resistance of the battery based on the amount of change in the step current and terminal voltage of the battery. In Article 9,
The above discharge capacity estimation unit is a battery status monitoring device that estimates the discharge capacity of the battery based on the internal resistance measured by the internal resistance measurement unit and a linear regression model. In a battery status monitoring method using a battery status monitoring device,
Step of acquiring the charge/discharge current and terminal voltage of the battery;
A step of measuring the micro-capacity of the battery based on the terminal voltage acquired in the above acquiring step;
A step of estimating the discharge capacity of the battery using the measured microcapacity and the linear regression model in the step of measuring the microcapacity;
A step of estimating the state of charge of the battery based on the stored SOC function and the discharge capacity estimated in the step of estimating the discharge capacity; and
A battery condition monitoring method including a step of updating the SOC function based on the discharge capacity estimated in the step of estimating the discharge capacity. In Article 11,
A battery state monitoring method wherein the above SOC function is a function of one of an accumulation function including the initial charge state of the battery, charge/discharge current, and discharge capacity as factors, and an open circuit voltage function which is the terminal voltage of the battery after the charge/discharge current is in a state of zero for a set time. In Article 11,
A battery status monitoring method in which, in the step of measuring the microcapacity, the charge/discharge current acquired in the step of acquiring is accumulated in a preset voltage range for the terminal voltage acquired in the step of acquiring, thereby measuring the microcapacity. In Article 13,
A battery condition monitoring method, wherein the step of measuring the microcapacity includes a step of varying the voltage range based on the size of the charge/discharge current. In Article 13,
A battery status monitoring method in which the above charge/discharge current has a fixed value within the error range when measuring the microcapacity. In Article 11,
A battery condition monitoring method further comprising a step of estimating a deterioration state of the battery based on an SOH function. In Article 16,
The above SOH function is a battery condition monitoring method including the initial discharge capacity and the current discharge capacity of the battery as factors. In Article 16,
A battery condition monitoring method in which, in the step of estimating the deterioration state, the deterioration state of the battery is estimated by substituting the initial discharge capacity and the current discharge capacity among the discharge capacities of the battery estimated in the step of estimating the discharge capacity into the SOH function. In Article 11,
A battery status monitoring method further comprising a step of measuring the internal resistance of the battery based on the amount of change in the step current and terminal voltage of the battery. In Article 19,
A battery status monitoring method for estimating the discharge capacity in the step of estimating the discharge capacity of the battery based on the internal resistance measured in the step of measuring the internal resistance and a linear regression model.

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