KR20210158115A - Apparatus and method for balancing battery - Google Patents

Abstract

A battery balancing device according to an embodiment of the present invention includes: a balancing circuit for redistributing the capacity of at least two or more battery packs; and a controller for calculating the power conversion efficiency based on the first input and output current of the balancing circuit unit, changing the output current command value within the arbitrarily set variable range, calculating variable power conversion efficiency based on the second input and output current of the balancing circuit unit corresponding to the variable output current command value, and determining a variable direction based on a result of comparing the variable power conversion efficiency and the power conversion efficiency. Accordingly, regardless of the electrical characteristics (voltage, charge/discharge current, capacity) of the battery pack from which the balancing circuit recovers or transfers energy, a balancing operation of maximum power conversion efficiency is always performed, which eliminates the need for a BMS equipped with a separate active balancing function.

Description

Battery balancing device and method

The present invention relates to a battery balancing apparatus and method.

An electric energy storage system (ESS) performs a function of supplying power to an electronic device after charging electric energy therein, and such an electric energy storage device is composed of a plurality of parallel-connected battery racks, A rack consists of a plurality of series-connected battery cells, modules, and packs. Battery rack is a plurality of series battery cells, modules, and packs due to variations in capacity and resistance, by the battery cells, modules, and packs having the maximum energy during charging, the battery cells, modules, The total energy capacity is determined by the pack. Therefore, balancing between the battery cells, modules, and packs that equalizes the energy of the battery cells, modules, and packs connected in series should be performed.

It is an object of the present invention to provide a battery balancing apparatus and method capable of actively performing battery balancing.

The technical problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

A battery balancing device according to an embodiment of the present invention calculates power conversion efficiency based on a first input and output current of a balancing circuit unit redistributing the capacity of at least two or more battery packs and the balancing circuit unit, and is within an arbitrarily set variable range. After varying the output current command value in the , calculating the variable power conversion efficiency based on the second input and output current of the balancing circuit unit corresponding to the changed output current command value, the variable power conversion efficiency and the power conversion efficiency It may include a control unit that determines the variable direction based on the comparison result.

A BMS for obtaining SOX information of a plurality of cells included in at least two or more battery packs may be further included.

The control unit may set an input current command threshold value and an output current command threshold value based on the SOX information.

The control unit may vary the output current command value within the variable range, so that the changed output current command value does not deviate from the output current command threshold value.

The control unit may calculate an input current command value based on the changed output current command value.

The control unit determines whether the input current command value deviates from the input current command threshold value, and when it does, the output current command value increases or can be adjusted downward.

If the input current command value does not deviate from the input current command threshold value, the control unit is configured based on a second input current corresponding to the input current command value and the second output current corresponding to the variable output current command value. The variable power conversion efficiency may be calculated.

As a result of the comparison, when the variable power conversion efficiency exceeds the power conversion efficiency, the controller may maintain the variable directionality varied within the variable range.

As a result of the comparison, when the variable power conversion efficiency does not exceed the power conversion efficiency, the controller may change the variable directionality varied within the variable range.

As a result of the comparison, the controller may adjust the variable size according to a difference between the variable power conversion efficiency and the power conversion efficiency.

A battery balancing method according to an embodiment of the present invention comprises the steps of calculating power conversion efficiency based on a first input and output current of a balancing circuit unit, and after varying an output current command value within an arbitrarily set variable range, the variable output Calculating the variable power conversion efficiency based on the second input and output currents of the balancing circuit unit corresponding to the current command value and determining the variable direction based on the result of comparing the variable power conversion efficiency and the power conversion efficiency have.

The method may further include obtaining SOX information of a plurality of cells included in at least two or more battery packs.

The method may further include setting an input current command threshold value and an output current command threshold value based on the SOX information.

The output current command value may be varied within the variable range, but the variable output current command value may be varied so as not to deviate from the output current command threshold value.

The method further includes calculating an input current command value based on the changed output current command value.

It is determined whether the input current command value deviates from the input current command threshold value, and if it does, the output current command value is adjusted upward or downward until the input current command value does not deviate from the input current command threshold value It may include further steps.

The calculating of the variable power conversion efficiency may include a second input current corresponding to the input current command value and a second input current corresponding to the input current command value and the variable output current command value if the input current command value does not deviate from the input current command threshold value. The variable power conversion efficiency may be calculated based on the second output current.

As a result of the comparison, when the variable power conversion efficiency exceeds the power conversion efficiency, the variable directionality may be maintained within the variable range.

As a result of the comparison, when the variable power conversion efficiency does not exceed the power conversion efficiency, the variable directionality variable within the variable range may be changed.

As a result of the comparison, the variable size may be adjusted according to a difference between the variable power conversion efficiency and the power conversion efficiency.

The battery balancing apparatus and method according to an embodiment of the present invention can be utilized in a battery rack of an energy storage device configured by connecting waste battery packs in series. In addition, the battery balancing apparatus and method of the present invention can be applied to a PCS (Power Control System) of a slow charger, ESS in which power efficiency is important.

Battery balancing apparatus and method according to an embodiment of the present invention can solve the energy imbalance between the waste battery packs in which the energy deviation exists, thereby maximizing the use cycle of the entire battery rack. In addition, it is possible to minimize damage to the battery rack by preventing overcharging of the waste battery pack, and to maximize the capacity of the energy storage device. This can reduce the cost compared to the existing one, and can provide the effect of reducing the disposal cost of the waste battery.

In addition, the battery balancing apparatus and method according to an embodiment of the present invention is always a balancing operation of the maximum power conversion efficiency regardless of the electrical characteristics (voltage, charge/discharge current, capacity) of the battery pack from which the balancing circuit recovers or transmits energy can be performed, and accordingly, a BMS equipped with a separate active balancing function is unnecessary.

1 is a block diagram showing the configuration of a battery balancing device according to an embodiment of the present invention.
2 is a graph illustrating power conversion efficiency according to an output current command value of a battery balancing circuit according to an embodiment of the present invention.
3 is a graph illustrating a case in which variable directionality is maintained according to an embodiment of the present invention.
4 is a graph illustrating a case in which variable directionality is changed according to an embodiment of the present invention.
5 is a graph showing power conversion efficiency under conditions according to an embodiment of the present invention.
6 is a flowchart illustrating a battery balancing method according to an embodiment of the present invention.

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. In adding reference numerals to the components of each drawing, it should be noted that the same components are given the same reference numerals as much as possible even though they are indicated on different drawings. In addition, in describing the embodiment of the present invention, if it is determined that a detailed description of a related known configuration or function interferes with the understanding of the embodiment of the present invention, the detailed description thereof will be omitted.

In describing the components of the embodiment of the present invention, terms such as first, second, A, B, (a), (b), etc. may be used. These terms are only for distinguishing the elements from other elements, and the essence, order, or order of the elements are not limited by the terms. In addition, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning in the context of the related art, and should not be interpreted in an ideal or excessively formal meaning unless explicitly defined in the present application. does not

1 is a block diagram showing the configuration of a battery balancing device according to an embodiment of the present invention.

As shown in FIG. 1 , the battery balancing apparatus 100 according to an embodiment of the present invention may include a BMS 110 , a balancing circuit unit 120 , a storage unit 130 , and a control unit 140 .

The BMS 110 may acquire status information of at least two or more battery packs. Here, the state information may include voltage, current, temperature, and SOX information of the battery pack. The SOX may include the degree of aging (SOH) of the battery pack, the amount of stored energy (SOC), and the remaining life (SOL) of the battery pack.

The balancing circuit unit 120 may redistribute the capacity of two or more battery packs. According to an embodiment of the present invention, the balancing circuit 120 may include an active balancing circuit.

The storage unit 130 may store at least one algorithm for performing calculation or execution of various commands for the operation of the battery balancing device according to an embodiment of the present invention. The storage unit 130 includes a flash memory, a hard disk, a memory card, a read-only memory (ROM), a random access memory (RAM), and an electrically erasable programmable read-only (EEPROM). Memory), a programmable read-only memory (PROM), a magnetic memory, a magnetic disk, and an optical disk may include at least one storage medium.

The control unit 140 may be implemented by various processing devices such as a microprocessor having a built-in semiconductor chip capable of performing operation or execution of various commands, and based on at least one algorithm stored in the storage unit 130 . to control the overall operation of the battery balancing device according to an embodiment of the present invention.

More specifically, the control unit 140 calculates the power conversion efficiency based on the first input and output currents of the balancing circuit unit 120, varies the output current command value within an arbitrarily set variable range, and then changes the output current command The variable power conversion efficiency is calculated based on the second input and output current of the balancing circuit unit 120 corresponding to the value, and the variable direction is determined based on the result of comparing the variable power conversion efficiency and the power conversion efficiency, and the optimal conversion efficiency can be found.

The controller 140 may set an input current command threshold value and an output current command threshold value based on the SOX information. For reference, setting the output current command threshold (I _out,limit ) and the input current command threshold (I _in,limit ) is separate because different battery packs are connected to the input and output of the balancing circuit unit 120 , respectively. to set the constraint of

The control unit 140 calculates the input power by the product of the first input current and the input voltage input to the balancing circuit unit 120, and the output power by the product of the first output current and the output voltage output from the balancing circuit unit 120 and the power conversion efficiency may be calculated based on the input power and the output power. The input power, output power, and power conversion efficiency can be expressed by Equations 1, 2, and 3 below. Here, the first input current may _{mean an input current corresponding to the current input current command value (I in,ref} ), and the first output current may mean an input current corresponding to the current output current command value (I _out,ref ). It can mean the output current.

<Formula 1>

P _in,p = V _in,p * I _in,p

<Calculation 2>

P _out,p = V _out,p * I _out,p

<Equation 3>

η _p = P _out,p / P _in,p

The controller 140 may vary the output current command value within an arbitrarily set variable range. The variable output current command value can be expressed by Equation 4.

<Equation 4>

I _out,ref' = I _out,ref + dev

Here, the control unit 140 may set the variable range dev arbitrarily, but when the temperature of the battery pack increases, the controller 140 may set the variable range narrowly, and may adjust the variable range for each SOC section. For example, when the SOC is in the range of 0 to 10% (lowest) and 90 to 100% (upper), the control unit 140 may set the variable range narrowly, and in the SOC of 20 to 80% section, expand the range The balancing speed can be improved. In addition, the control unit 140 limits the balancing current to 0.1C when the SOH is 90% to prevent aging due to a decrease in SOH, and limits the balancing current to 0.09C when the SOH is 80%, and the SOH is At 10%, the balancing current can be limited to 0.02C.

2 is a graph illustrating power conversion efficiency according to an output current command value of a battery balancing circuit according to an embodiment of the present invention. As shown in FIG. 2 , when the control unit 140 sets a wide variable range of the output current command value, the speed of estimating the optimal efficiency decreases, but the sensitivity of the algorithm can be improved in the tracking process. In addition, when the control unit 140 narrows the variable range of the output current command value, the sensitivity of the algorithm decreases, but the optimal efficiency estimation speed can be increased. When the control unit 140 sets the variable range by following the graph showing the _{electric conversion efficiency, the greater the d(η dev} -η _p )/d( dev ), the greater the power conversion efficiency curve slope, so the step size of dev is set to be large, the algorithm is driven by giving priority to the algorithm estimation speed, and the slope of the power conversion efficiency curve decreases as _{d(η dev} -η _p )/d( dev ) becomes smaller. By reducing it, it is possible to drive the algorithm by giving priority to the algorithm sensitivity.

The control unit 140 may vary the output current command value so as not to deviate from the output current command threshold value. To this end, the control unit 140 determines whether the variable output command value is out of the output current command threshold value (I _{out, ref'} > I _{out, limit} or I _out,ref' < I _out,limit ) can be determined.

If it is determined that the changed output current command value deviates from the output current command threshold value, the controller 140 may adjust the output current command value upward or downward. On the other hand, if it is determined that the changed output current command value does not deviate from the output current command threshold value, the control unit 140 calculates the input current command value (I _in,ref' ) based on the changed output current command value. have. According to an embodiment, the controller 140 may calculate the input current command value using Equation 5.

<Equation 5>

I _in,ref' =I _out,ref' *[V _out,p / (η _p V _in,p )]

The control unit 140 determines whether the input current command value is out of the input current command threshold value (I _{in, ref'} > I _{in, limit} or It is possible to determine whether _{I in,ref'} < I _{in,limit ).}

When it is determined that the input current command value deviates from the input current command threshold value, the controller 140 may adjust the output current command value upward or downward. Here, when the control unit 140 increases or decreases the output current command value, when the balancing circuit unit 120 increases or decreases the output current command value, the input current command value also increases or decreases. Therefore, the control of the algorithm For unity, it is reduced based on the output current reference value.

If it is determined that the input current command value does not deviate from the input current command threshold value, the control unit 140 is based on the second input current corresponding to the input current command value and the second output current corresponding to the changed output current command value. Calculate the power conversion efficiency. The controller 140 calculates variable input power by multiplying the second input current and the input voltage input to the balancing circuit unit 120 , and outputs a variable output by the product of the second output current and the output voltage output from the balancing circuit unit 120 . Power is calculated, and variable power conversion efficiency may be calculated based on variable input power and variable output power. Variable input power, variable output power, and variable power conversion efficiency can be expressed by the following formulas 6, 7, and 8.

<Calculation 6>

P _{in, dev} = V _{in, dev} * I _{in, dev}

<Calculation 7>

P _{out, dev} = V _{out, dev} * I _{out, dev}

<Calculation 8>

η _dev = P _{out, dev} / P _{in, dev}

The controller 140 may determine the variable direction based on a result of comparing the variable power conversion efficiency and the power conversion efficiency. A more detailed description will be given with reference to FIGS. 3 and 4 .

3 is a graph illustrating a case in which variable directionality is maintained according to an embodiment of the present invention, and FIG. 4 is a graph illustrating a case in which variable directionality is changed according to an embodiment of the present invention.

As illustrated in FIG. 3 , when the variable power conversion efficiency exceeds the current power conversion efficiency, the controller 140 may maintain the variable directionality changed within a variable range. Meanwhile, as shown in FIG. 4 , when the variable power conversion efficiency does not exceed the current power conversion efficiency, the controller 140 may control to change the variable direction changed within a variable range.

In addition, the controller 140 may adjust the variable size according to the difference between the variable power conversion efficiency and the current state of the power conversion efficiency. For example, if the difference is large, the controller 140 may adjust the variable size to be large, and if the difference is small, the controller 140 may adjust the variable size to be small.

5 is a graph showing power conversion efficiency under conditions according to an embodiment of the present invention.

As shown in FIG. 5 , many power conversion efficiency curves may exist according to various voltage, current, temperature, and SOX conditions in the balancing operation of the battery pack, but according to the embodiment of the present invention, the controller 140 controls the variable power By comparing the conversion efficiency with the current power conversion efficiency, the variable direction is determined, so that the optimum power conversion efficiency can be found regardless of the various conditions described above.

6 is a flowchart illustrating a battery balancing method according to an embodiment of the present invention.

As shown in FIG. 6 , the controller 140 may acquire SOX information from the BMS 110 . The SOX may include the degree of aging (SOH) of the battery pack, the amount of stored energy (SOC), and the remaining life (SOL) of the battery pack.

The controller 140 may set an input current command threshold value and an output current command threshold value based on the SOX information (S120). For reference, setting the output current command threshold (I _out,limit ) and the input current command threshold (I _in,limit ) is separate because different battery packs are connected to the input and output of the balancing circuit unit 120 , respectively. to set the constraint of

The control unit 140 calculates the input power by the product of the first input current and the input voltage input to the balancing circuit unit 120, and the output power by the product of the first output current and the output voltage output from the balancing circuit unit 120 , and it is possible to calculate the power conversion efficiency based on the input power and the output power (S130). For calculation methods of input power, output power, and power conversion efficiency, refer to Equations 1, 2, and 3. Here, the first input current may _{mean an input current corresponding to the current input current command value (I in,ref} ), and the first output current may mean an input current corresponding to the current output current command value (I _out,ref ). It can mean the output current.

The control unit 140 may vary the output current command value I _out,ref within an arbitrarily set variable range ( S140 ). Refer to Equation 4 for the variable output current command value.

The control unit 140 may vary the output current command value so as not to deviate from the output current command threshold value. To this end, the control unit 140 determines whether the variable output command value is out of the output current command threshold value (I _{out, ref'} > I _{out, limit} or It can be determined whether I _out,ref' < I _{out,limit ) (S150).}

If it is determined in S150 that the changed output current command value deviates from the output current command threshold (Y), the controller 140 may adjust the output current command value upward or downward (S160). On the other hand, if the control unit 140 determines that the changed output current command value does not deviate from the output current command threshold value in S150 (N), based on the changed output current command value, the input current command value (I _{in, ref')} ) can be calculated (S170). For the calculation method of the input current command value (I _in,ref' ), refer to Equation 5.

The control unit 140 determines whether the input current command value is out of the input current command threshold value (I _{in, ref'} > I _{in, limit} or It can be determined whether I _in,ref' < I _{in,limit ) (S180).}

If it is determined in S180 that the input current command value deviates from the input current command threshold value (Y), the controller 140 may adjust the output current command value upward or downward (S190). Here, when the control unit 140 increases or decreases the output current command value, when the balancing circuit unit 120 increases or decreases the output current command value, the input current command value also increases or decreases. Therefore, the control of the algorithm For unity, it is reduced based on the output current command value.

In S180, if it is determined that the input current command value does not deviate from the input current command threshold value (N), the control unit 140 maintains the changed output current command value as the output current command value (S200), and returns to the input current command value. Power conversion efficiency is calculated based on the corresponding second input current and the second output current corresponding to the changed output current command value (S210).

In S210, the control unit 140 calculates variable input power by multiplying the second input current and the input voltage input to the balancing circuit unit 120, and as a product of the second output current and the output voltage output from the balancing circuit unit 120 The variable output power may be calculated, and the variable power conversion efficiency may be calculated based on the variable input power and the variable output power. For calculation methods of variable input power, variable output power, and variable power conversion efficiency, refer to Equations 6, 7, and 8.

The controller 140 may determine the variable direction based on a result of comparing the variable power conversion efficiency and the power conversion efficiency. To this end, the controller 140 may determine whether the variable power conversion efficiency exceeds the current power conversion efficiency (S220).

If it is determined in S220 that the variable power conversion efficiency exceeds the current power conversion efficiency, the control unit 140 may maintain the variable directionality changed within the variable range (S230). In addition, in S230, the controller 140 may adjust the variable size according to the degree to which the variable power conversion efficiency exceeds the current power conversion efficiency. For example, the controller 140 may greatly change the variable size if the degree of excess is large, and may change the size of the variable if the degree of excess is small. Meanwhile, in S220 , when the variable power conversion efficiency does not exceed the current power conversion efficiency, the controller 140 may control to change the variable direction changed within the variable range ( S240 ). In addition, in S240 , the controller 140 may adjust the variable size according to the degree to which the variable power conversion efficiency does not exceed the current power conversion efficiency. For example, the controller 140 may greatly change the variable size if the degree of not exceeding is large, and may change the variable size to be small if the degree of not exceeding is small.

The above description is merely illustrative of the technical spirit of the present invention, and various modifications and variations will be possible without departing from the essential characteristics of the present invention by those skilled in the art to which the present invention pertains.

Accordingly, the embodiments disclosed in the present invention are not intended to limit the technical spirit of the present invention, but to explain, and the scope of the technical spirit of the present invention is not limited by these embodiments. The protection scope of the present invention should be construed by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

battery balancing device 100
BMS 110
balancing circuit 120
storage 130
control 140

Claims (20)

a balancing circuit for redistributing the capacity of at least two or more battery packs; and
The power conversion efficiency is calculated based on the first input and output currents of the balancing circuit unit, and the output current command value is varied within an arbitrarily set variable range, and then the second input of the balancing circuit unit corresponding to the changed output current command value. , A battery balancing device comprising: a controller that calculates variable power conversion efficiency based on an output current, and determines a variable direction based on a result of comparing the variable power conversion efficiency and the power conversion efficiency. The method according to claim 1,
Battery balancing device further comprising a BMS for obtaining SOX information of a plurality of cells included in at least two or more battery packs. 3. The method according to claim 2,
the control unit
A battery balancing device for setting an input current command threshold value and an output current command threshold value based on the SOX information. 4. The method according to claim 3,
the control unit
A battery balancing device for varying the output current command value within the variable range so that the changed output current command value does not deviate from the output current command threshold value. 5. The method of claim 4,
the control unit
A battery balancing device for calculating an input current command value based on the changed output current command value. 6. The method of claim 5,
the control unit
It is determined whether the input current command value deviates from the input current command threshold value, and if it does, the output current command value is adjusted upward or downward until the input current command value does not deviate from the input current command threshold value battery balancing device. 7. The method of claim 6,
the control unit
If the input current command value does not deviate from the input current command threshold value, the variable power is based on a second input current corresponding to the input current command value and the second output current corresponding to the variable output current command value. A battery balancing device that yields conversion efficiency. The method according to claim 1,
the control unit
As a result of the comparison, when the variable power conversion efficiency exceeds the power conversion efficiency, the battery balancing device maintains the variable directionality varied within the variable range. The method according to claim 1,
the control unit
As a result of the comparison, when the variable power conversion efficiency does not exceed the power conversion efficiency, the battery balancing device changes the variable directionality within the variable range. The method according to claim 1,
the control unit
As a result of the comparison, the battery balancing apparatus adjusts the variable size according to a difference between the variable power conversion efficiency and the power conversion efficiency. calculating power conversion efficiency based on the first input and output currents of the balancing circuit unit;
after varying an output current command value within an arbitrarily set variable range, calculating variable power conversion efficiency based on a second input/output current of the balancing circuit unit corresponding to the changed output current command value; and
and determining a variable direction based on a result of comparing the variable power conversion efficiency and the power conversion efficiency. 12. The method of claim 11,
The battery balancing method further comprising acquiring SOX information of a plurality of cells included in at least two or more battery packs. 13. The method of claim 12,
The battery balancing method further comprising the step of setting an input current command threshold value and an output current command threshold value based on the SOX information. 14. The method of claim 13,
A battery balancing method for varying the output current command value within the variable range so that the changed output current command value does not deviate from the output current command threshold value. 15. The method of claim 14,
The battery balancing method further comprising the step of calculating an input current command value based on the changed output current command value. 16. The method of claim 15,
It is determined whether the input current command value deviates from the input current command threshold value, and if it does, the output current command value is adjusted upward or downward until the input current command value does not deviate from the input current command threshold value A method of balancing a battery further comprising the step. 17. The method of claim 16,
Calculating the variable power conversion efficiency includes:
If the input current command value does not deviate from the input current command threshold value, the variable power is based on a second input current corresponding to the input current command value and the second output current corresponding to the variable output current command value. A battery balancing method that yields conversion efficiency. 12. The method of claim 11,
As a result of the comparison, when the variable power conversion efficiency exceeds the power conversion efficiency, the battery balancing method for maintaining the variable directionality varied within the variable range. 12. The method of claim 11,
As a result of the comparison, when the variable power conversion efficiency does not exceed the power conversion efficiency, the battery balancing method for changing the variable directionality within the variable range. 12. The method of claim 11,
As a result of the comparison, the battery balancing method for adjusting the variable size according to a difference between the variable power conversion efficiency and the power conversion efficiency.

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