Patent Description:
Recently, due to the exhaustion of fossil energy and environmental pollution, the interest in electric products which are capable of being driven by using electric energy without the use of fossil energy is growing more and more.

Accordingly, with the increasing development and demand of mobile device, electric vehicles, hybrid vehicles, power storage devices, uninterrupted power supplies, and the like, the demands of second batteries as energy sources are rapidly increasing, and also demand forms are being diversified.

Thus, more studies on secondary batteries are being actively carried out to cope with such diverse demands. In general, secondary batteries include nickel-cadmium batteries, nickel-hydrogen batteries, lithium ion batteries, and lithium ion polymer batteries.

Such secondary batteries are classified into lithium based batteries and nickel-hydrogen based batteries. Lithium-based batteries are mainly used for small products such as digital cameras, P-DVDs, MP3Ps, cellular phones, PDAs, portable game devices, power tools, and E-bikes, and nickel hydrogen-based batteries are mainly applied to and used for large products such as electric vehicles or hybrid electric vehicles, which need high output.

To drive electric vehicles or hybrid electric vehicles, a motor has to be driven, which requires high output. Also, in case of the power storage devices for supplying power to buildings or certain areas, a large amount of power that is enough to satisfy power demands has to be supplied. As described above, to provide power having high output or large capacity, a plurality of batteries, each of which is composed of a unit cell assembly, are connected in series or parallel to each other to supply desired output or power.

However, in case of the battery in which a plurality of battery cells are connected to each other, there may be made differences among charge capacities of the unit cells after the unit cells are repeatedly charged and discharged. If the discharging of the battery is continued in the state where the difference in charging capacity exists, it may be difficult to stably operate the battery because a specific unit cell having low charging capacity is overdischarged. On the other hand, if the charging of the battery is continued in the state where the difference in charging capacity exists, a specific unit cell may be overcharged to disturb the safety of the battery.

The difference in charging capacity may cause the overcharging or overdischarging of some of the unit cells. As a result, due to the above-described problem, power may not be stably supplied to a load (e.g., an electric motor, a power grid, and the like).

To solve this problem, various methods for continuously monitoring the charge capacity of the battery cells to balance the charge capacity of the battery cells to a constant level are required.

With regard to this, <CIT> discloses classifying the state of the battery into a plurality of zones and controlling the charge and discharge of the battery correspondingly depending on to which region the current state of the battery corresponds. Further, <CIT> discloses the technique of equally charging the energy storage device in the hybrid electric automobile. <CIT> teaches shifting the location of the battery power request transfer function having a power-SOC profile to maintain the SOC of the battery used in the hybrid automobile to a high level. In addition, <CIT> discloses monitoring the state-of-charge of the energy storage device and controlling the charge and discharge of the energy charging device based on the charge state. <CIT> discloses partitioning the SOC of the battery into seven (<NUM>) regions by six (<NUM>) threshold values and controlling the charge of the battery depending on to which region the SOC of the battery corresponds. The thesis of <NPL>), which relates to the control technique of Vehicle-to-Grid (V2G) for frequency control, discloses performing the adaptive frequency droop control to maintain the SOC of the electric automobile battery constantly. <CIT> discloses calculating the SOC of the battery and controlling the charge and discharge of the battery based on the calculated SOC and the temperature of the battery.

<CIT> describes a method for providing control power for a power network, in which at least one energy store connected to the power network supplies energy to the power network as a function of a frequency deviation from a target frequency of the power network and/or absorbs energy from the power network. A deadband around the target frequency is specified, wherein the frequency deviation from the network frequency is measured with a higher accuracy than the width of the deadband, and a bandwidth is selected within the deadband as a function of a charging state of the energy store, wherein control power is provided outside the bandwidth. The document also describes a device for carrying out such a method, in which the device comprises at least one energy store and a control for controlling or regulating the control power of the energy store, wherein the energy store is connected to a power network such that energy can be supplied to the power network and be drawn from the power network by the device.

An object of the present invention is to provide a system and method for correcting a battery SOC, which is capable of more efficiently correcting a battery SOC value to a predetermined range by adjusting a dead band in charging/discharging directions or adjusting charging/discharging power while charging/discharging a battery.

The object of the present invention is not limited to the aforesaid, but other objects not described herein will be clearly understood by those skilled in the art from descriptions below.

According to an aspect of the present invention, there is provided a system for maintaining a state-of-charging (SOC) of a battery to be charged through power supplied from a power producing device of a battery energy storage system(BESS), within a predetermined range, the system including: an SOC measuring unit configured to measure an SOC value of the battery; a storage unit configured to store preset operation ranges to determine whether charging/discharging of the battery is compensated, wherein values of the operation ranges are changed according to a state of the battery or surrounding environment; a determining unit configured to determine an operation range corresponding to the SOC value of the battery among the preset operation ranges, the determined operation range being a range on which a dead band in charging/discharging directions is based, a frequency correction signal range corresponding to a range of the dead band in charging/discharging directions being used to adjust an amount of a power signal applied to the battery; and an SOC correcting unit configured to adjust the dead band in charging/discharging directions to thereby adjust the frequency correction signal range according to the result determined in the determining unit to maintain the SOC value of the battery within the predetermined range.

According to another aspect of the present invention, there is provided a method for maintaining a state-of-charging (SOC) of a battery to be charged through power supplied from a power producing device of a battery energy storage system (BESS), within a predetermined range, the method including: measuring an SOC value of the battery; comparing the SOC value to preset operation ranges to determine an operation range corresponding to the SOC value, the determined operation range being a range on which a dead band in charging/discharging directions is based, a frequency correction signal range corresponding to a range of the dead band in charging/discharging directions being used to adjust an amount of a power signal applied to the battery, wherein values of the operation ranges are changed according to a state of the battery or surrounding environment; and adjusting the dead band in charging/discharging directions to thereby adjust the frequency correction signal range according to conditions corresponding to the operation range which corresponds to the SOC value to maintain the SOC value of the battery within the predetermined range.

According to the present invention, the SOC correction may be performed by adjusting the dead band section in the charging/discharging directions or adjusting the charging/discharging power while charging/discharging the battery to maintain the SOC value of the battery within a predetermined range. In addition, the probability that the SOC value of the battery reaches about <NUM>% or about <NUM>% may be reduced, and the battery may be reduced in capacity when the battery is designed.

Terms or words used in the specification and claims should not be construed as limited to a lexical meaning, and should be understood as appropriate notions by the inventor based on that he/she is able to define terms to describe his/her invention in the best way to be seen by others.

Therefore, the embodiments described in this specification and the constructions illustrated in the drawings are only preferred embodiments of the present invention. Accordingly, it should be understood that various equivalents and modifications which can substitute the embodiments may be provided at a point of application time of this specification; it is the appended claims that define the invention. Moreover, detailed descriptions related to well-known functions or configurations will be ruled out in order not to unnecessarily obscure subject matters of the present invention.

Hereinafter, a system and method for correcting an SOC of a battery according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

<FIG> is a block diagram of a system for correcting a state-of-charging (SOC) of a battery according to an embodiment of the present invention.

Referring to <FIG>, a system <NUM> for correcting an SOC of a battery includes an SOC measuring unit <NUM>, a storage unit <NUM>, a determining unit <NUM>, and an SOC correcting unit <NUM>.

First, the SOC measuring unit <NUM> measures an SOC value of the battery which is charged through power supplied from a power producing device of a battery energy storage system (BESS). The SOC measuring unit <NUM> may measure the SOC value of the battery at every preset unit time.

Also, the SOC value of the battery, which is measured in the SOC measuring unit <NUM>, is stored in the storage unit <NUM>.

A plurality of operation ranges corresponding to SOC values of the battery are stored in the storage unit <NUM>. The plurality of operation ranges may be previously set to determine whether the charging/discharging of the battery is compensated. The operation range corresponding to the SOC value of the battery may be set to an operation range that are adequate for a lifecycle of the BESS.

For example, if an operation range that is discussed with the company of customer is about <NUM>% to about <NUM>% of the SOC value, and an operation range adequate for the lifecycle of the BESS is about <NUM>% to about <NUM>% of the SOC value, the operation ranges may be set to operation ranges for a reference value. Here, if an operation range is about <NUM>% to about <NUM>% of the SOC value of the battery, which is measured in the SOC measuring unit <NUM>, the operation range may be defined as a first operation range. If an operation range is about <NUM>% to about <NUM>% of the SOC value, the operation range may be defined as a second operation range, and if an operation range is about <NUM>% to about <NUM>% of the SOC value, the operation range may be defined as a third operation range. Since there are many demands to match the SOC value of the battery to a level of about <NUM>%, the second operation range may be determined as a normal range. In this example, the value of each of the operation ranges is set as described above. In the present invention, the values of the operation ranges are changed according to a state of the battery or surrounding environments.

The determining unit <NUM> may compare the measured SOC value of the battery to the plurality of operation ranges stored in the storage unit <NUM> to determine an operation range corresponding to the measured SOC value of the battery among the plurality of operation ranges.

The SOC correcting unit <NUM> stores correction values corresponding to the plurality of operation ranges.

The correction values may be set to correction values different from each other according to the operation ranges. The first correction value corresponding to the first operation range may include conditions for increasing a dead band in a charging direction or decreasing the dead band in a discharging direction.

The second correction value corresponding to the second operation range may include conditions for increasing the dead band in the charging/discharging directions or maintaining the present state, and the third correction value corresponding to the third operation range may include conditions for decreasing the dead band in the charging direction or increasing the dead band in the discharging direction.

The SOC correcting unit <NUM> adjusts the dead band section according to the result determined in the determining unit <NUM> to correct the SOC value of the battery.

For example, when the measured SOC value of the battery corresponds to the first operation range, the SOC correcting unit <NUM> increases the dead band in the charging direction or decreases the dead band in the discharging direction. Since the second operation range corresponds to the normal range, when it is determined that the measured SOC value of the battery corresponds to the second operation range, the present state is maintained. Here, even through the measured SOC value of the battery corresponds to the normal range, the dead band may be increased in the charging direction in consideration of efficiency of the battery.

When the measured SOC value of the battery corresponds to the third operation range, the dead band is decreased in the charging direction or increased in the discharging direction.

As described above, the dead band section in the charging/discharging directions may be adjusted to correct the SOC value of the battery while charging/discharging the battery, thereby maintaining the SOC value within a predetermined range.

<FIG> is a flowchart of a method for correcting the SOC of the battery according to an embodiment of the present invention.

Referring to <FIG>, the SOC measuring unit <NUM> measures an SOC value of a battery which is charged through power supplied from the power producing device of the BESS (S100). The SOC value of the battery may be measured at every preset unit time.

<FIG> is a graph of SOC values of the battery, which are measured at every unit time. Referring to <FIG>, it is seen that an SOC value of the battery is frequently changed in a range of about <NUM>% to about <NUM>%.

The determining unit (<NUM>) compares the measured SOC value of the battery to the plurality of operation ranges stored in the storage unit (see reference numeral <NUM> of <FIG>) to determine an operation range corresponding to the measured SOC value among the plurality of operation ranges (S110).

The plurality of operation ranges corresponding to the SOC values of the battery are stored in the storage unit <NUM>. The plurality of operation ranges may be previously set to determine whether the charging/discharging of the battery is compensated.

The plurality of operation ranges will be described with reference to the graph of <FIG>. Here, an x-axis in the graph may denote a time, and a y-axis in the graph may denote an SOC value of the battery.

Referring to <FIG>, the SOC value of the battery may be partitively set to ranges of about <NUM>% to about <NUM>% (a first operation range: a), about <NUM>% to about <NUM>% (a second operation range: b), and about <NUM>% to about <NUM>% (a third operation range: c).

Since there are many demands to match the present SOC value of the battery to a level of about <NUM>%, it may be determined that the first operation state a is defined as an overcharged state, the second operation range b is defined as a normal range, and the third operation range c is defined as an overcharged state. In this example, the value of each of the operation ranges is set as described above. In the present invention, the values of the operation ranges may be changed in consideration of capacity, charging efficiency, discharging resistance, and the like of the battery.

Next, the SOC correcting unit <NUM> performs SOC correction by using a correction value corresponding to the operation range which corresponds to the measured SOC value (S120). The SOC correction may adjust the dead band section in the charging/discharging directions according to the result determined in the operation S110.

The SOC correction value will be described with reference to the graphs of <FIG>.

<FIG> illustrates a case in which the SOC value of the battery, which is measured in the SOC measuring unit corresponds to the first operation range a of about <NUM>% to about <NUM>%. When the measured SOC value of the battery corresponds to the first operation range, the dead band is increased in the charging direction or decreased in the discharging direction.

When the dead band is increased in the charging direction, a range of the dead band in the charging direction is expanded to reduce a frequency correction signal range corresponding to the range of the dead band. Also, the number of power signal applied to the battery is decreased. Also, probability that the SOC value of the battery reaches about <NUM>% is reduced.

When the dead band in the discharging direction is decreased, the range of the dead band in the discharging direction is decreased, and the frequency correction signal range corresponding to the range of the dead band is increased. Also, the number of power signal applied to the battery is increased. Also, probability that the SOC value of the battery reaches about <NUM>% is reduced.

Referring to <FIG>, when the SOC value of the battery, which is measured in the SOC measuring unit <NUM> corresponds to the second operation range b of about <NUM>% to about <NUM>%, the present state is maintained, or the dead band in the charging/discharging directions is increased in consideration of the efficiency of the battery, as illustrated in <FIG>.

Referring to <FIG>, when the SOC value of the battery, which is measured in the SOC measuring unit <NUM> corresponds to the third operation range c of about <NUM>% to about <NUM>%, the dead band in the charging direction is decreased, the dead band in the discharging direction is increased, as illustrated <FIG>.

When the dead band in the charging direction is decreased, the range of the dead band is decreased, and the frequency correction signal range corresponding to the range of the dead band is increased. Also, the number of power signal applied to the battery is increased, and probability that the SOC value of the battery reaches about <NUM>% is reduced.

As described above, the SOC value of the battery may be measured, and the operation range corresponding to the measured SOC value may be determined. Then, the dead band section may be adjusted by using the correction value corresponding to the operation range to maintain the SOC value within a predetermined range.

<FIG> is a block diagram of a system <NUM> for correcting an SOC of a battery according to another embodiment of the present invention.

First, the SOC measuring unit <NUM> measures an SOC value of the battery which is charged through power supplied from a power producing device of a battery energy storage system (BESS). The SOC value of the battery may be measured at every preset unit time.

The SOC value of the battery, which is measured in the SOC measuring unit <NUM>, is stored in the storage unit <NUM>.

A plurality of operation ranges corresponding to SOC values of the battery are stored in the storage unit <NUM>. The plurality of operation ranges may be previously set to determine whether the charging/discharging of the battery is compensated. The operation ranges corresponding to the SOC value of the battery may be set to operation ranges that are adequate for a lifecycle of the BESS.

For example, if an operation range that is discussed with the company of customer is about <NUM>% to about <NUM>% of the SOC value, and an operation range adequate for a lifecycle of the BESS is about <NUM>% to about <NUM>% of the SOC value, the operation ranges may be set to operation ranges for a reference value. Here, if an operation range is about <NUM>% to about <NUM>% of the SOC value of the battery, which is measured in the SOC measuring unit <NUM>, the operation range may be set to a first operation range. If an operation range is about <NUM>% to about <NUM>% of the SOC value, the operation range may be set to a second operation range, and if an operation range is about <NUM>% to about <NUM>% of the SOC value, the operation range may be set to a third operation range. Since there are many demands to match the SOC value of the battery to a level of about <NUM>%, the second operation range may be determined as a normal range. In this example, the value of each of the operation ranges is set as described above. In the present invention, the values of the operation ranges are changed according to a state of the battery or surrounding environments.

The determining unit <NUM> determines an operation range corresponding to the measured SOC value of the battery among the plurality of operation ranges.

The SOC correcting unit <NUM> stores correction values corresponding to the plurality of operation ranges, respectively.

The SOC correcting unit <NUM> includes a first correcting part 240a, a second correcting part 240b, and a third correcting part 240c. The correcting parts have correction values obtained by using charging/discharging power adjusting manners different from each other, respectively.

The first correcting part 240a includes conditions for increasing or decreasing charging/discharging power in an exponential form. The second correcting part 240b includes conditions for increasing or decreasing the charging/discharging power in a stepped form. Also, a third correcting part 240c includes conditions for increasing or decreasing the charging/discharging power at a predetermined ratio.

The SOC correcting unit <NUM> adjusts the charging/discharging power according to the result determined in the determining unit <NUM> to correct the SOC value of the battery.

For example, when it is determined that the SOC value of the battery corresponds to the first operation range by the determining unit <NUM>, one correcting part of the SOC correcting unit <NUM> is selected to perform the SOC correction by using the correction value of the selected correcting part, which corresponds to the first operation range.

When the measured SOC value of the battery corresponds to the first operation range, the charging power is decreased, or the discharging power is increased. Here, the charging/discharging power may be increased or decreased in the exponential or stepped form or at the predetermined ratio.

Since the second operation range corresponds to the normal range, when it is determined that the measured SOC value of the battery corresponds to the second operation range, the present state is maintained.

When the measured SOC value of the battery corresponds to the third operation range, the charging power is increased, or the discharging power is decreased. Here, the charging/discharging power may be increased or decreased in the exponential or stepped form or at the predetermined ratio.

As described above, since the charging/discharging power is adjusted according to the various conditions to perform the SOC correction, the SOC value of the battery may be maintained within a predetermined range. In addition, the probability that the SOC value of the battery reaches about <NUM>% or about <NUM>% may be reduced, and the battery may be reduced in capacity when the battery is designed.

<FIG> is a flowchart of a method for correcting the SOC of the battery according to another embodiment of the present invention.

Referring to <FIG>, an SOC value of the battery which is charged through power supplied from a power producing device of a battery energy storage system (BESS) is measured (S200). The SOC value of the battery may be measured at every preset unit time. <FIG> is a graph of SOC values of the battery, which is measured at every unit time. Referring to <FIG>, it is seen that an SOC value of the battery is frequently changed in a range of about <NUM>% to about <NUM>%.

The measured SOC value of the battery is compared to the plurality of operation ranges stored in the storage unit (see reference numeral <NUM> of <FIG>) to determine an operation range corresponding to the measured SOC value among the plurality of operation ranges (S210).

Referring to <FIG>, the SOC value of the battery may be partitively set to ranges of about <NUM>% to about <NUM>% (a first operation range: a), about <NUM>% to about <NUM>% (a second operation range: b), and about <NUM>% to about <NUM>% (a third operation range: c). Since there are many demands to match the present SOC value of the battery to a level of about <NUM>%, it may be determined that the first operation state is defined as an overcharged state, the second operation range is defined as a normal range, and the third operation range is defined as an overcharged state. In this example, the value of each of the operation ranges is set as described above. In the present invention, the values of the operation ranges may be changed in consideration of capacity, charging efficiency, discharging resistance, and the like of the battery.

Next, one correcting part of the SOC correcting unit is selected.

The SOC correcting unit <NUM> includes a first correcting part 240a, a second correcting part 240b, and a third correcting part 240c. The correcting parts are operated by using charging/discharging power adjusting manners different from each other, respectively.

Then, the SOC correction is performed by using the correction value corresponding to the operation range which corresponds to the measured SOC value of the battery (S220). The SOC correction may adjust the charging/discharging power according to the result determined in the operation S210.

A method for adjusting the charging/discharging power may include various methods set in the SOC correcting unit <NUM> and will be described with reference to embodiments.

First, <FIG> are graphs of a method for increasing or decreasing the charging/discharging power in the exponential form.

<FIG> illustrates a case in which the SOC value of the battery, which is measured in the SOC measuring unit corresponds to the first operation range a of about <NUM>% to about <NUM>%. When the measured SOC value of the battery corresponds to the first operation range, a correction value by which the charging power is decreased in the exponential form, and the discharging power is increased in the exponential form is applied. The probability that the SOC value of the battery reaches about <NUM>% may be reduced, and the battery may be reduced in capacity when the battery is designed.

<FIG> illustrates a case in which the SOC value of the battery, which is measured in the SOC measuring unit corresponds to the second operation range b of about <NUM>% to about <NUM>%. In this case, it is determined as the normal range to maintain the present state.

Next, <FIG> illustrates a case in which the SOC value of the battery, which is measured in the SOC measuring unit corresponds to the third operation range c of about <NUM>% to about <NUM>%. In this case, a correction value by which the charging power is increased in the exponential form, and the discharging power is decreased in the exponential form is applied.

<FIG> are graphs of a method for increasing or decreasing the charging/discharging power in the stepped form.

<FIG> illustrates a case in which the SOC value of the battery, which is measured in the SOC measuring unit corresponds to the first operation range a of about <NUM>% to about <NUM>%. When the measured SOC value of the battery corresponds to the first operation range, a correction value by which the charging power is decreased in the stepped form, and the discharging power is increased in the stepped form is applied.

Next, <FIG> illustrates a case in which the SOC value of the battery, which is measured in the SOC measuring unit corresponds to the third operation range c of about <NUM>% to about <NUM>%. In this case, a correction value by which the charging power is increased in the stepped form, and the discharging power is decreased in the stepped form is applied.

<FIG> are graphs of a method for increasing or decreasing the charging/discharging power at a predetermined ratio.

<FIG> illustrates a case in which the SOC value of the battery, which is measured in the SOC measuring unit corresponds to the first operation range a of about <NUM>% to about <NUM>%. When the measured SOC value of the battery corresponds to the first operation range, a correction value by which the charging power is decreased at a predetermined ratio is applied.

Next, <FIG> illustrates a case in which the SOC value of the battery, which is measured in the SOC measuring unit corresponds to the third operation range c of about <NUM>% to about <NUM>%. In this case, a correction value by which the discharging power is decreased at a predetermined ratio in comparison to the existing discharging power is applied.

The embodiment of the present invention is to be considered illustrative, and not restrictive, and the present invention is not limited to the foregoing embodiment.

Claim 1:
A system for maintaining a state-of-charging (SOC) of a battery to be charged through power supplied from a power producing device of a battery energy storage system (BESS), within a predetermined range, the system comprising:
an SOC measuring unit (<NUM>) configured to measure an SOC value of the battery;
a storage unit (<NUM>) configured to store preset operation ranges to determine whether charging/discharging of the battery is compensated;
a determining unit (<NUM>) configured to determine an operation range corresponding to the SOC value of the battery among the preset operation ranges, the determined operation range being a range on which a dead band in charging/discharging directions is based, a frequency correction signal range corresponding to a range of the dead band in charging/discharging directions being used to adjust an amount of a power signal applied to the battery; and
an SOC correcting unit (<NUM>) configured to adjust the dead band in charging/discharging directions to thereby adjust the frequency correction signal range according to the result determined in the determining unit to maintain the SOC value of the battery within the predetermined range;
characterised in that the system is further configured to change values of the operation ranges according to a state of the battery or surrounding environment.