KR20150005073A - Method and apparatus for estimating SOC in constant current state, battery management system and energy storage system comprising the same - Google Patents

Abstract

A method of estimating a state of charge (SOC) in a constant current state comprises: (A) determining whether a charging/discharging current of a battery lies within a constant current range; (B) when the charging/discharging current of a battery is determined to lie within the constant current range in step (A), counting a constant current duration (T1); and (C) estimating a final SOC by compensating for a current accumulation-based SOC (SOCi) through an open circuit voltage (OCV)-based SOC (SOCv) compensation according to the duration counted in step (B). According to the invention, an accumulated error due to an SOC estimation is reduced in a device constantly operating for a long time, such that the SOC can be accurately estimated, overcharging and overdischarging of the battery can be reduced, and a lifespan of the battery can be elongated. Furthermore, since a compensation ratio is adjusted according to a current value, battery cells can be managed efficiently.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an SOC estimating method, an apparatus, a battery management system and an energy storage system including the same,

The present invention relates to a method and an apparatus for estimating an SOC, and more particularly, to a method, an apparatus, a battery management system and an energy storage system for estimating an SOC in a constant current.

The importance of renewable energy is increasing due to climate change due to global warming and exhaustion of various fossil fuels. However, since most of renewable energy is based on natural energy, there is a disadvantage that efficiency and output fluctuate and power generation can not be controlled easily. In fact, renewable energy using sunlight or wind power can acquire energy intermittently, which makes it difficult to match the obtained energy with the consumption pattern. Therefore, in order for renewable energy to be widely used, an energy storage system (ESS: Energy Storage System), which is a means for storing energy generated intermittently and stably supplying energy, is needed.

Energy Storage System (ESS) is a system that can store generated power and supply power in a stable manner according to demand pattern. It is a system that stores excess generated power in a power plant and temporarily transmits power when power is insufficient. It says.

An energy storage system is a "power reservoir" that stores electricity on a large scale and is used when necessary. It is a technology that stores electric power in an energy storage means to supply the remaining power and energy to the required time and place. Energy is stored in energy storage means such as pumped storage, compressed air storage, and large secondary batteries without generating power from the power plant directly to the home or factory, Thereby increasing energy efficiency.

The pumped-storage and compressed-air storage systems, which occupy most of the current energy storage means, will become less profitable in the future due to the problem of securing the installation space. The secondary battery system, which is relatively easy to maintain and manage, Is rapidly emerging.

1 is a block diagram of a general energy storage system. The energy storage system shown in FIG. 1 includes a battery system (not shown) including first to nth racks R1 to Rn and a battery monitoring system 12 10, a power conversion system 14, and an energy management system 16.

The first rack R1 includes a first battery module B1.1 to an nth battery module B1.n and a first battery management system BMS.B, The first battery module Bn.1 to the nth battery module Bn.n and the first battery management system BMS.B. In addition, each of the battery modules B1.1 to Bn.n includes a plurality of battery cells (not shown) and a plurality of second battery management systems (BMS.A).

The battery system 10 is for charging and storing energy and discharging energy when necessary. The power conversion system 14 is connected to a grid, which is a power grid, to convert a direct current to an alternating current or to convert an alternating current to a direct current And the energy management system 16 is for controlling the battery system 10 and the power conversion system 14 in consideration of an internal load, a battery condition, and the like.

On the other hand, the first battery management system (BMS.B) included in the first rack (R1) to the nth rack (Rn) calculates the state of charge (SOC) The first battery module to the n-th battery module, and the first rack (R1) to the n-th rack (Rn). Also, the second battery management system (BMS.A) included in the first to n-th battery modules senses the voltage, current, and temperature of the plurality of battery cells included in the battery module, and performs cell balancing And to efficiently manage battery cells.

On the other hand, the battery cell may be dangerous if it is charged significantly higher than the rated charge range, and battery life may be shortened when discharged below the rated charge range. Therefore, it is required to grasp the accurate charging state of the battery cell in order to charge or discharge the battery cell within the rated charging range.

Factors affecting the state of charge of the battery cell include, for example, factors such as the chemical reaction of each battery cell, the internal impedance of the cell, the rate of self-discharge, the reduction of the actual capacity, and the variation of the operating temperature.

The temperature mismatch in the cell is an important factor in the imbalance of the cell charge state. For example, a battery cell has a "self-discharge" which is a function of battery temperature, and a high temperature battery typically exhibits a higher self-discharge rate than a low temperature battery. As a result, a battery with a higher temperature exhibits a lower charge over time than a battery with a lower temperature.

Also, when the battery cells are repeatedly charged and discharged, the actual capacity is reduced. In estimating the charged state of the battery, if the estimation error increases, the battery cells can not be efficiently managed and the energy efficiency of the battery cells is lowered. do. Therefore, if the state of charge of the battery is accurately estimated, it is possible to efficiently manage the battery cell, thereby extending the service life of the battery cell and efficiently using the battery cell.

The SOC estimating method, apparatus, and battery management system including the same according to the present invention are applied to the first battery management system (BMS.B) included in the first rack to the nth rack of the energy storage system, But also to the second battery management system (BMS.A) included in the first to n-th battery modules. However, the present invention is not limited to this, and may be applied to a battery management system included in any type of apparatus or system using a battery cell, such as an electric vehicle.

Particularly, since the energy storage system includes a large number of battery modules including a plurality of battery cells, it is very important to accurately estimate the state of charge of the battery cells and to efficiently manage the battery cells to improve energy efficiency.

In order to estimate the state of charge (hereinafter referred to as SOC) of the battery cell, the conventional battery management system estimates the SOC by integrating the input and output currents, that is, the charge and discharge currents. This current integration based SOC estimation is based on the fact that when the initial SOC is known, the SOC of the battery cell can be estimated by integrating the charging current and the discharging current while charging and discharging the battery cell.

However, although the SOC estimation based on the current integration can estimate the SOC relatively accurately in a short period of time, when the long-term SOC is estimated, since the current sensor has a basic measurement error in measuring the input / output current of the battery cell, The error of the current measurement is accumulated. In order to estimate the SOC, it is necessary to perform repetitive calculations for continuously integrating the current. In this case, since the calculation error is accumulated due to the iterative calculation, the SOC estimation error accumulates. Therefore, There is a problem that the error increases with the elapse of time.

Another SOC estimation method is a method of estimating the SOC based on an open circuit voltage (hereinafter referred to as OCV) of the battery. Since the OCV and SOC exhibit a good linear relationship, the SOC is estimated based on the table indicating the relationship between the OCV and the SOC, based on the fact that the SOC can be estimated by estimating the OCV. That is, the SOC is estimated based on the correlation between the voltage of the battery cell and the charging state of the battery cell.

In order to estimate the SOC based on the OCV, it is first necessary to know the OCV. Since the OCV is an open-circuit voltage, the device using the battery cell is in a state in which no electricity is used, The OCV should be determined by measuring the voltage. However, since this is not easy, we actually estimate the OCV based on the voltage, current, and internal resistance of the battery cell and then estimate the SOC based on the estimated OCV.

However, when the load is applied, the voltage of the battery cell is distorted due to the voltage drop of the internal resistance of the battery. Therefore, when the SOC is estimated based on the OCV in a device in which the load fluctuation is severe, the SOC estimation error becomes large. Therefore, when the load is applied, the SOC is not normally estimated based on OCV.

Therefore, when the low current section lasts for a predetermined time or longer, the SOC is estimated based on the OCV of the battery cell, and when the current exceeding the predetermined current is input / output through the battery cell, the SOC is estimated based on the current integration .

The patent documents described in the following prior art documents disclose that when charging or discharging of a battery occurs during a running operation of an electric vehicle and charging and discharging of the battery do not occur due to constant speed running or stopping, The relationship between the voltage corresponding to the first time point at which the effect of the resistance component due to the internal resistance of the battery is eliminated during the period in which the battery is not charged and discharged and the first time point, The OCV is estimated using the relationship between the voltage corresponding to the second time point after a predetermined time elapses from the time point at which the polarization phenomenon due to the electrolyte diffusion is removed after the effect of the resistance component due to the resistance is removed, , And sets the SOC based on the estimated OCV.

The conventional SOC estimating method as described above only discloses accurate estimation of the SOC during a period during which charging and discharging does not occur. Therefore, there is no mention of a method of accurately estimating the SOC during charging / discharging, Therefore, while charging / discharging is occurring, the SOC should be estimated using the SOC estimation method by current integration.

However, as a method of estimating the SOC based on the current computation, as described above, since the current measurement errors are accumulated as time elapses and the calculation errors are accumulated in the SOC estimation, It is difficult to efficiently manage the battery cells. As a result, the efficiency of the energy storage system is lowered and the life of the battery cells is shortened.

Accordingly, there is a need for an SOC estimation method and apparatus capable of efficiently managing a battery cell by accurately estimating SOC by reducing cumulative error caused by SOC estimation in a device operating for a long period of time.

KR10-0805116

SUMMARY OF THE INVENTION It is an object of the present invention to provide an apparatus and method for estimating SOC by accurately estimating SOC by reducing cumulative error caused by SOC estimation in a device operating for a long time, And a method of estimating the SOC at the constant current.

Another object of the present invention is to provide a constant current SOC estimating apparatus capable of efficiently managing a battery cell by accurately estimating an SOC by reducing an accumulated error caused by SOC estimation in a device operating for a long period of time .

Another object of the present invention is to provide a battery having a constant current SOC estimating device capable of efficiently managing a battery cell by accurately estimating an SOC by reducing an accumulated error due to SOC estimation in a device operating for a long period of time, Management system.

Another problem to be solved by the present invention is to provide an apparatus and method for estimating an SOC of a battery cell by accurately estimating SOC by reducing cumulative error caused by SOC estimation in a device operating for a long period of time, Storage system.

According to an aspect of the present invention, there is provided a method of estimating an SOC during a constant current,

(A) determining whether a charge / discharge current of the battery is in a constant current section;

(B) counting a constant current duration (T1) when the charge / discharge current of the battery is determined to be in a constant current period in the step (A); And

(C) estimating a final SOC by correcting SOC (SOCi) based on current integration through SOC (SOCv) compensation based on the open circuit voltage (OCV) according to the duration counted in step (B) .

In the SOC estimation method for a constant current according to an embodiment of the present invention, the step (C)

(C1) receiving an SOC (SOCi) based on current integration;

(C2) receiving an OCV based SOC (SOCv); And

And calibrating SOCi through SOCv compensation according to the counted duration of C3 to estimate the final SOC.

In the SOC estimation method for a constant current according to an embodiment of the present invention, the step (C) may include estimating a final SOC by correcting SOCi by increasing the SOCv compensation ratio in proportion to the constant current duration.

In the SOC estimation method for a constant current according to an embodiment of the present invention, the step (A) may include a step of determining whether a charge / discharge current of the battery is within a predetermined range for a predetermined period.

In the SOC estimating method for a constant current according to an embodiment of the present invention, the predetermined period may be 60 seconds.

In the SOC estimation method for a constant current according to an embodiment of the present invention, the step (C) may include a step of determining an SOCv compensation rate for the SOCv compensation.

In the SOC estimating method for a constant current according to an embodiment of the present invention, the SOCv compensation rate may be adjusted according to a charge / discharge current of the battery.

In the SOC estimation method for a constant current according to an embodiment of the present invention, the SOCv compensation rate is calculated by Rate = T1 / Time (I), where T1 is a constant current duration, The charge / discharge current, Time (I), may be a time to charge or discharge a predetermined ratio of the total SOC when charging or discharging with the current I.

In the SOC estimation method for a constant current according to an embodiment of the present invention, the step (C)

(C4) determining if the SOCv compensation ratio is greater than or equal to one;

(C5) estimating a final SOC based on the OCV if the SOCv compensation ratio is greater than or equal to 1 in the step (C4); And

(C6) If the SOCv compensation ratio is less than 1 in the step (C4), the SOCv based on the current integration may be corrected through the SOCv compensation according to the compensation ratio to estimate the final SOC.

In the SOC estimating method for a constant current according to an exemplary embodiment of the present invention, the step of estimating a final SOC in the step (C6) may include calculating a final SOC based on a final SOC = Rate x SOCv + (1-Rate) x SOCi And a step of estimating.

An SOC estimating apparatus for a constant current according to an embodiment of the present invention includes:

A constant current section determining unit for determining whether a charge / discharge current of the battery is in a constant current section;

A constant current duration time counting unit for counting a constant current duration T1; And

And a final SOC estimator for estimating a final SOC by correcting the SOC (SOCi) based on the current integration through SOC (SOCv) compensation based on the open circuit voltage (OCV) according to the duration counted by the constant current duration counting unit .

In the constant current SOC estimating apparatus according to an embodiment of the present invention, the final SOC estimating unit receives the SOC (SOCi) based on the current integration from the current integration based SOC (SOCi) estimating unit, The OCV-based SOC (SOCv) is received and the final SOC can be estimated by correcting SOCi through SOCv compensation according to the counted duration.

In the constant current SOC estimating apparatus according to an embodiment of the present invention, the final SOC estimating unit may estimate the final SOC by correcting SOCi by increasing the SOCv compensation ratio in proportion to the constant current duration.

In the constant current SOC estimating apparatus according to an embodiment of the present invention, the constant current period determining unit may determine whether the charge / discharge current of the battery is within a predetermined range for a predetermined period.

In the constant current SOC estimating apparatus according to an embodiment of the present invention, the predetermined period may be 60 seconds.

In the constant current SOC estimating apparatus according to an embodiment of the present invention, the final SOC estimating unit may determine an SOCv compensation rate for the SOCv compensation.

In the constant current SOC estimating apparatus according to an embodiment of the present invention, the SOCv compensation rate may be adjusted according to the charge / discharge current of the battery.

In the constant current SOC estimating apparatus according to an embodiment of the present invention, the SOCv compensation rate is calculated by Rate = T1 / Time (I), where T1 is a constant current duration, The charge / discharge current, Time (I), may be a time to charge or discharge a predetermined ratio of the total SOC when charging or discharging with the current I.

The final SOC estimating unit may determine whether the SOCv compensation ratio is greater than or equal to 1 and if the SOCv compensation ratio is greater than or equal to 1, And if the SOCv compensation ratio is less than 1, the final SOC can be estimated by correcting the SOC (SOCi) based on the current integration through the SOCv compensation according to the compensation ratio.

In the constant current SOC estimating apparatus according to an embodiment of the present invention, the final SOC estimating unit may estimate a final SOC based on a final SOC = Rate × SOCv + (1-Rate) × SOCi.

The battery management system according to an embodiment of the present invention includes the SOC estimating unit for the constant current.

The energy storage system according to an embodiment of the present invention includes the SOC estimating apparatus for the constant current.

The features and advantages of the present invention will become more apparent from the following detailed description based on the accompanying drawings.

Prior to that, terms and words used in the present specification and claims should not be construed in a conventional and dictionary sense, and the inventor may properly define the concept of the term in order to best explain its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

According to the method of estimating SOC during constant current according to the present invention, it is possible to accurately estimate the SOC by reducing the cumulative error caused by the SOC estimation in an apparatus that operates constantly for a long period of time. Thus, overcharge and overdischarge of the battery can be prevented, The battery life can be increased and the battery cell can be effectively managed by adjusting the compensation ratio according to the current value.

1 is a block diagram illustrating a typical energy storage system.
BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an SOC estimating apparatus,
3 is a block diagram illustrating an SOC estimating apparatus for a constant current according to an embodiment of the present invention.
4 is a graph showing a SOC estimation method in a constant current according to an embodiment of the present invention.
5 is a detailed flowchart illustrating an SOC estimation method in a constant current according to an embodiment of the present invention.
6 is a graph showing a change in a current change and an SOCv compensation rate according to an SOC estimation method in a constant current according to an embodiment of the present invention.
FIG. 7 is a graph showing a change in the SOC estimation value according to the SOC estimation method in the constant current according to an embodiment of the present invention and a change in the SOC estimation value according to the related art.

BRIEF DESCRIPTION OF THE DRAWINGS The objectives, specific advantages and novel features of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: FIG.

It should be noted that, in the present specification, the reference numerals are added to the constituent elements of the drawings, and the same constituent elements are assigned the same number as much as possible even if they are displayed on different drawings.

Also, the terms "first", "second", "once", "other end", and the like are used to distinguish one component from another, and the fact that the component is limited by the terms no.

Further, when it is described that a component is connected to another component, this includes a case where the component is directly connected and a case where the component is connected with another component in between, and when the component is described as including any component , Which means that it can include other components, not excluding other components.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following description of the present invention, detailed description of related arts which may unnecessarily obscure the gist of the present invention will be omitted.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a diagram illustrating an SOC estimation system to which an SOC estimating apparatus for a constant current according to an embodiment of the present invention is applied.

The SOC estimation system shown in FIG. 2 includes a sensing unit 22 for sensing battery current, battery voltage and temperature from a plurality of battery cells 20, a battery current output from the sensing unit 22, a temperature, (SOCi) estimator 24 for estimating SOC based on the current integration by inputting actual capacity based SOC (SOH_C), battery voltage, battery current and temperature output from sensing unit 22, An SOC (SOCv) estimator 26 based on an open circuit voltage (OCV) for inputting a battery internal resistance value IR to estimate an SOC based on an open circuit voltage (OCV) A final SOC estimating unit 28 for estimating the SOC finally based on the SOCi outputted from the SOCi estimating unit 24 and the SOCv outputted from the SOCv estimating unit 26. [

2, the previous SOC acquires the previous SOC by delaying the SOC output from the final SOC estimator 28, and the actual capacity reference SOC (SOH_C) is the actual SOC (SOH_C) (SOH_C) estimating unit (not shown) that estimates the SOC of the actual capacity reference SOC.

2, the final SOC estimating device 28 is a part to which an SOC estimating device and method for a constant current according to an embodiment of the present invention is applied. The final SOC estimating device 28 includes an SOCi estimating part 24, SOCv outputted from the SOCv estimator 26, and the current output from the sensing unit 22, and finally estimates the SOC.

In general, the final SOC estimation device estimates the SOC (SOCv) based on the open circuit voltage (OCV) of the battery cell when the low-current section lasts for a certain period of time, The SOC (SOCi) is estimated based on the current integration.

However, in the above-described final SOC estimation method, since the voltage of the battery cell is distorted by the voltage drop of the internal resistance of the battery cell when the load is applied, the SOC estimation through the open circuit voltage is not performed SOC is estimated only by current integration. Therefore, since the current measurement error accumulates with time, and the calculation error is accumulated when the SOC estimation is performed, the SOC is estimated based on the current integration in the device that operates for a long time such as the energy storage system, The battery cell can not be efficiently managed, the efficiency of the energy storage system is lowered, and the life of the battery cell is shortened.

However, even if the load is applied and the device charges and discharges for a long time, the OCV can be accurately estimated because the constant voltage current lasts for a certain time, that is, the voltage change is small when the current change is small. In the present invention, the SOC estimation based on the current integration is compensated by gradually increasing the OCV-based SOC compensation ratio in proportion to the constant current duration in the constant current section in which the constant current is maintained for a predetermined time or more using the stable voltage characteristic in the constant current section, Reduce cumulative error of SOC estimation (SOCi) based on current integration.

Therefore, the SOC estimation based on the current integration based on the accurate SOC estimation in a short time and the cumulative error of the SOC estimation based on the current integration for a long time can be reduced, and the SOC estimation based on the open circuit voltage Can be obtained at the same time.

FIG. 3 is a block diagram illustrating an SOC estimating apparatus for a constant current according to an embodiment of the present invention, and FIG. 4 is a flowchart illustrating a SOC estimating method for a constant current according to an embodiment of the present invention.

The constant current SOC estimating apparatus according to an embodiment of the present invention shown in FIG. 3 includes a constant current period determining unit 30 for determining whether a charge / discharge current of a battery is in a constant current period, a constant current duration time (SOCi) based on the current integration based on the SOC (SOCv) compensation based on the open circuit voltage (OCV) according to the duration time T1 counted by the constant current duration counting unit 32 and the constant current duration counting unit 32, ) To estimate a final SOC.

The constant current section determining unit 30, the constant current duration counting unit 32 and the final SOC estimating unit 34 may be configured as a control unit (not shown) such as a microcontroller unit (MCU) , But is not limited thereto.

The constant current section determination unit 30 monitors the battery current output from the sensing unit 22 to determine whether the current is within a predetermined range for a predetermined period of time or longer and determines whether the current is within the constant current range (step S400). If it is determined in step S400 that the constant current section is not in the constant current section, it is determined whether the constant current section is still in the constant current section.

If the constant current section determining unit 30 determines that the current is in the constant current period in step S400, the constant current duration counting unit 32 starts counting the constant current duration (step S410).

The final SOC estimating unit 34 calculates a constant current based on the SOCi outputted from the SOCi estimating unit 24, the SOCv outputted from the SOCv estimating unit 26 and the constant current output time counted by the constant current duration counting unit 32 SOC (SOCi) based on current integration is corrected through SOCv compensation over time to estimate final SOC (step S420).

The method of finally estimating the SOC by the final SOC estimating unit 34 in step S420 will be described in detail with reference to a flowchart showing the SOC estimation method in the constant current according to the embodiment of the present invention shown in Fig. 5 do.

The constant current section determination unit 30 monitors the battery current output from the sensing unit 22 to determine whether the current is within a predetermined range for a predetermined period of time or longer and determines whether the current is within the constant current range (step S500). If it is determined in step S500 that the constant current section is not in the constant current section, it is determined whether the constant current section is still in the constant current section.

If the constant current section determining unit 30 determines that the current is in the constant current period in step S500, the constant current duration counting unit 32 starts counting the constant current duration T1 (step S510).

The final SOC estimating unit 34 determines an SOCv compensation rate (Rate) for SOCv compensation (step S520). The SOCv compensation ratio (Rate) is determined according to the charging / discharging current of the battery as shown in Equation (1).

In the above equation, T1 denotes a constant current duration, I denotes a charging / discharging current of the battery, and Time (I) denotes a time to charge or discharge a predetermined ratio of the total SOC when charging or discharging with the current I. That is, the SOCv compensation rate (Rate) is differently applied depending on the battery charge / discharge current (I). For example, Time (I) can be set to a time for charging / discharging 50% of the charging capacity of the battery cell. If the current (I) is large, the charging time is shortened so that the value of Time (I) becomes small. When the current (I) is small, the charging time becomes long and the value of Time (I) becomes large.

In step S530, it is determined whether the SOCv compensation rate (Rate) is 1 or more.

When the SOCv compensation rate is less than 1, the SOCv compensation ratio is increased in proportion to the constant current duration through the SOCv compensation according to the SOCv compensation ratio (Rate) to compensate the SOCv to estimate the final SOC (Step S550).

On the other hand, when the compensation rate (Rate) is 1 or more, only the OCV-based SOC estimation is applied in estimating the final SOC as shown in Equation (3).

As described above, in the present invention, in estimating the final SOC in the final SOC estimating unit 34, the ratio of SOC estimation (SOCi) based on the cumulative integration is reduced in proportion to the duration of the constant current section, (OCV) based SOC estimation (SOCv) ratio. Therefore, it is possible to reduce the accumulation of errors in the SOC estimation based on the cumulative totalization over time, through the SOCv compensation (Rate × SOCv).

Also, when the SOCv compensation rate (Rate) is 1 or more, only the SOC estimation based on the open circuit voltage (OCV) is applied to the final SOC estimation without applying the SOC estimation based on the current integration in estimating the final SOC. Since the SOCv compensation ratio (Rate) is 1 or more, it means that the constant current reaches the target SOC and the constant current is stably maintained for a long time. Therefore, in estimating the final SOC, the final SOC estimator 34 estimates the open circuit voltage OCV) based on SOC estimation (SOCv).

6 is a graph showing a change in current and an SOCv compensation rate according to an SOC estimation method in a constant current according to an embodiment of the present invention.

In the interval from time a to time b, the battery cell is continuously discharging in a period in which the current (I) is indicated by -5 A (amperes). Since this is a constant current duration period in which the constant current is constantly maintained, The SOCv compensation rate increases and becomes 1 in the end.

On the other hand, at time b, the current changes from -5A (ampere) to 0A (ampere), which means that the battery cell becomes an open circuit state in a discharged state.

FIG. 7 is a graph showing a change in the SOC estimation value according to the SOC estimation method in the constant current according to an embodiment of the present invention and a change in the SOC estimation value according to the prior art.

In FIG. 7, c represents the estimated final SOC when applying the SOC estimation method according to the present invention, and d represents the estimated final SOC when the conventional final SOC estimation method is applied.

In FIG. 7, e is an actual SOC since it is a stabilized SOC after the open circuit state lasts for a predetermined period. From time b onwards, the final SOC estimated by the conventional final SOC estimation method is the final It can be seen that the final SOC estimated by the SOC estimating method in the constant current of the present invention does not differ from the actual final SOC while the SOC converges to the actual final SOC after a long time. That is, it can be seen that the SOC estimating method according to the present invention estimates the SOC accurately close to the actual final SOC.

The methods discussed herein may be implemented using various means, depending on the application. For example, these methods may be implemented in the form of hardware, firmware, software, or any combination thereof. In an embodiment involving hardware, the control unit may comprise one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), field programmable gate arrays (FPGAs), processors, controllers, micro- Processors, electronic devices, other electronic units designed to perform the functions discussed herein, or a combination thereof.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not to be limited to the disclosed embodiments, but, on the contrary, It is evident that it can be modified or improved.

It will be understood by 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 by the appended claims.

SOCi: current integration based SOC
SOCv: Open circuit voltage based SOC
30: Constant current section determination section
32: Constant current duration counting section
34: Final SOC estimation unit

Claims (22)

(A) determining whether a charge / discharge current of the battery is in a constant current section;
(B) counting a constant current duration (T1) when the charge / discharge current of the battery is determined to be in a constant current period in the step (A); And
(C) estimating a final SOC by correcting SOC (SOCi) based on current integration through SOC (SOCv) compensation based on an open circuit voltage (OCV) according to the duration counted in step (B) SOC estimation method for constant current. The method of claim 1, wherein the step (C)
(C1) receiving an SOC (SOCi) based on current integration;
(C2) receiving an OCV based SOC (SOCv); And
And estimating a final SOC by correcting the SOCi through SOCv compensation according to the counted duration of the current (C3). The method according to claim 2, wherein the step (C)
Estimating a final SOC by correcting the SOCi by increasing the SOCv compensation ratio in proportion to the constant current duration. 4. The method of claim 3, wherein the step (A)
And determining whether the charge / discharge current of the battery is within a predetermined range for a predetermined period of time. The method of claim 4, wherein the predetermined period is 60 seconds. The method of claim 1, wherein the step (C) comprises determining an SOCv compensation rate for the SOCv compensation. 7. The method of claim 6, wherein the SOCv compensation ratio (Rate) is adjusted according to a charge / discharge current of the battery. 8. The method of claim 7, wherein the SOCv compensation ratio (Rate)
(I) is the charge / discharge current of the battery, and Time (I) is the charge / discharge current of the battery, T1 is the constant current duration, I is the charge / discharge current of the battery, And a time for discharging the SOC. The method of claim 8, wherein the step (C)
(C4) determining if the SOCv compensation ratio is greater than or equal to one;
(C5) estimating a final SOC based on the OCV if the SOCv compensation ratio is greater than or equal to 1 in the step (C4); And
(C6) correcting the SOC (SOCi) based on the current integration through the SOCv compensation according to the compensation ratio and estimating the final SOC when the SOCv compensation ratio is less than 1 in the step (C4) SOC estimation method for constant current. The method of claim 9, wherein estimating the final SOC in step (C6)
Estimating a final SOC based on a final SOC = Rate x SOCv + (1-Rate) x SOCi. A constant current section determining unit for determining whether a charge / discharge current of the battery is in a constant current section;
A constant current duration time counting unit for counting a constant current duration T1; And
And a final SOC estimator for estimating a final SOC by correcting the SOC (SOCi) based on the current integration through SOC (SOCv) compensation based on the open circuit voltage (OCV) according to the duration counted by the constant current duration counting unit SOC estimation device for constant current. 12. The apparatus of claim 11, wherein the final SOC estimator comprises:
(SOCi) based on the current integration from the current integration based SOC (SOCi) estimating unit, receives the OCV based SOC (SOCv) from the OCV based SOC estimating unit, and calculates SOC And estimates a final SOC. 14. The apparatus of claim 12, wherein the final SOC estimator comprises:
And the final SOC is estimated by correcting the SOCi by increasing the SOCv compensation ratio in proportion to the constant current duration. 14. The constant current circuit according to claim 13,
And determines whether the charge / discharge current of the battery is within a predetermined range for a predetermined period of time. 15. The apparatus of claim 14, wherein the predetermined period is 60 seconds. 12. The apparatus of claim 11, wherein the final SOC estimator determines an SOCv compensation rate for the SOCv compensation. 17. The apparatus of claim 16, wherein the SOCv compensation ratio (Rate) is adjusted according to a charge / discharge current of the battery. 18. The method of claim 17, wherein the SOCv compensation ratio (Rate)
(I) is the charge / discharge current of the battery, and Time (I) is the charge / discharge current of the battery, T1 is the constant current duration, I is the charge / discharge current of the battery, (SOC) of the constant current. 19. The apparatus of claim 18, wherein the final SOC estimator comprises:
Determining whether the SOCv compensation ratio is greater than or equal to one,
If the SOCv compensation ratio is greater than or equal to 1, the final SOC is estimated based on the OCV,
Wherein the SOC estimation unit estimates the final SOC by correcting the SOC based on the current integration through the SOCv compensation according to the compensation ratio when the SOCv compensation ratio is less than one. 21. The apparatus of claim 19, wherein the final SOC estimator comprises:
Estimating a final SOC based on a final SOC = Rate x SOCv + (1-Rate) x SOCi. A battery management system comprising an SOC estimating device for a constant current according to any one of claims 11 to 20. An energy storage system comprising an SOC estimating unit for a constant current according to any one of claims 11 to 20.

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