KR102412722B1 - Control method of multi-functional energy storage system - Google Patents

Abstract

An embodiment includes a first functional step of performing a first function by charging and discharging an Energy Storage System (ESS) having a first state-of-health (SOC) state at a time point; a second functional step of charging and discharging the ESS having a second SOC state at a time point to perform a second function; and before switching from the first functional stage to the second functional stage or from the second functional stage to the first functional stage, making the ESS into the second SOC state or the first SOC state through charging or discharging An ESS control method including the SOC change step is provided.

Description

Multifunctional energy storage device control method {CONTROL METHOD OF MULTI-FUNCTIONAL ENERGY STORAGE SYSTEM}

This embodiment relates to a method of controlling an energy storage device that performs a multi-function.

As renewable energy generation increases, the introduction of ESS (Energy Storage System) is also increasing.

Since renewable energy generation is mainly unpredictable, the difference in supply and demand disturbs the power grid, and ESS can contribute to the stability of the power grid by absorbing this difference.

Recently, the demand for ESS in densely populated residential areas such as apartments is also increasing. In these areas, electricity is stored in ESS during times when electricity prices are low and then electricity from ESS is utilized during times when electricity prices are high. For other reasons, there are cases where high power cannot be used instantaneously due to the limitations of the power reception facilities in these areas. Recently, as the number of electric vehicles increases, the introduction of ESS to use such high power is increasing.

As described above, ESS enables more efficient use of electricity by dispersing or concentrating the supply and consumption of electricity.

In order to alleviate the problem of high investment cost of ESS, it is necessary to increase the utilization ratio and utilization time of ESS, and it is necessary to further advance the development of related technologies.

Against this background, an object of the present embodiment is, in one aspect, to provide a technology for increasing the utilization rate of the ESS. In another aspect, an object of the present embodiment is to provide a technology for increasing the utilization time of an ESS.

In order to achieve the above object, one embodiment, a first functional step of performing a first function by charging and discharging an ESS (Energy Storage System) having a first state-of-health (SOC) state at a time point; a second functional step of charging and discharging the ESS having a second SOC state at a time point to perform a second function; and before switching from the first functional stage to the second functional stage or from the second functional stage to the first functional stage, making the ESS into the second SOC state or the first SOC state through charging or discharging An ESS control method including the SOC change step is provided.

The first function may be voltage regulation or frequency regulation of a power grid interlocked with the ESS, and the second function may be a demand response using the ESS.

In the ESS control method, in the second function step, when the ESS absorbs the over-generation of the power grid, the second SOC may be set lower than the first SOC.

The first SOC may be 0.5.

The ESS control method further includes a control step of determining the performance of the first functional step or the second functional step, wherein, in the control step, when the performance of the first functional step or the second functional step is predicted , it is possible to determine the execution of the SOC change step.

The ESS control method compares a monitoring value and a threshold value in the control step, and when the monitoring value enters within a predetermined range from the threshold value, predicts the performance of the first functional step and performs the SOC change step can decide

The threshold value may be determined by one of a safety priority mode, an intermediate mode, and an economy priority mode selected by a user manipulation signal.

The input ratio of the ESS in the first function may also be determined by the determined mode.

The ESS control method further comprises a DR receiving step of receiving a DR (Demand Response) signal including a DR (Demand Response) time and a DR amount, and in the control step, the DR time is closer to within a certain time. In this case, it is possible to predict the performance of the second functional step and determine the execution of the SOC change step.

The ESS control method may reset the second SOC according to the DR time and the DR amount in the control step.

As described above, according to the present embodiment, it is possible to increase the utilization ratio of the ESS by using the ESS for multiple functions. In addition, according to this embodiment, it is possible to increase the utilization time of the ESS by making the wear of the ESS minimum or optimal for the same use.

1 is a block diagram of a power grid system according to an embodiment.
2 is a view showing a wear index of a battery according to an embodiment.
3 is a block diagram of a control device according to an embodiment.
4 is a diagram illustrating a frequency curve and a threshold value of a power grid according to an embodiment.
5 is a layout view of a user manipulation button according to an exemplary embodiment.
6 is a diagram for explaining a second function according to an embodiment.
7 is a flowchart of an ESS control method according to an embodiment.
8 is a flowchart of a method for performing a first function according to an embodiment.
9 is a flowchart of a method for performing a second function according to an embodiment.

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 present invention, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted.

In addition, in describing the components 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. When it is described that a component is “connected”, “coupled” or “connected” to another component, the component may be directly connected or connected to the other component, but another component is formed between each component. It should be understood that elements may also be “connected,” “coupled,” or “connected.”

1 is a block diagram of a power grid system according to an embodiment.

Referring to FIG. 1 , the microgrid 100 may be connected to the first power grid 180 through a connection panel 170 . The first power grid 180 may be a commercial power grid and may be a macro grid higher than the microgrid 100 .

A second power grid 160 may be included in the microgrid 100 , and the ESS 110 , the load 140 , and the renewable energy power generation source 150 , etc. may be connected to the second power grid 160 .

The ESS 110 is a large-capacity energy storage device, and may generally be configured with a battery, and may be configured with other energy storage devices such as a flywheel, depending on the embodiment.

The ESS 110 may supply current to or receive current from the first power grid 180 through the power conversion device 120 . In addition, the ESS 110 may supply current to or receive current from the second power grid 160 through the power conversion device 120 . In the drawing, the current supplied from the microgrid 100 to the first power grid 180 is represented by the first current i1 , and the current supplied from the second power grid 160 to a configuration other than the ESS 110 . is represented by the second current i2, and the current supplied from the ESS 110 to the power grid system is represented by the third current i3.

The sum of the second current (i2) and the third current (i3) is equal to the first current (i1). Since the second current (i2) is uncontrolled, the microgrid 100 controls the third current (i1). It is possible to control the first current i1.

The third current i3 input and output from the ESS 110 may be controlled by the power converter 120 , and the power converter 120 may be controlled by the controller 130 . Hereinafter, it may be understood that the control device 130 controls the third current i3 as substantially controlling the power conversion device 120 . The third current i3 may be understood as an input/output current of the ESS 110 , or may be understood as a charge/discharge current of the ESS 110 .

The ESS 110 may perform multiple functions in order to increase the utilization ratio. For example, the ESS 110 controls the maximum output current for the first current i1 , the demand response for the first power grid 180 , and voltage regulation for the first power grid 180 or the second power grid 160 . Alternatively, a function such as frequency regulation may be performed. The ESS 110 may perform two or more functions at the same time, or may sequentially perform one or more functions for each time zone.

At this time, the ESS 110 may perform each function in consideration of the wear index.

2 is a diagram illustrating a wear index of a battery according to an exemplary embodiment.

Referring to FIG. 2 , the wear index of the battery may vary according to state-of-charge (SOC). Here, the wear index is a value representing a reduction ratio of the battery life to the unit charge/discharge amount, and as the wear index increases, it means that the battery life is greatly reduced when the same charge/discharge current is input/output to the battery.

In the embodiment shown in FIG. 2 , the wear index of the battery may increase as the SOC increases. The wear index when SOC is 0.8 may be greater than the wear index when SOC is 0.4. Although not shown, in other batteries, the wear index is the smallest when the SOC is 0.5, and the wear index may increase as the SOC is further away from 0.5.

The control device can increase the utilization time of the ESS by performing each function of the ESS in the optimal SOC state in consideration of the wear index.

3 is a block diagram of a control device according to an embodiment.

Referring to FIG. 3 , the control device 130 includes a first function unit 210 , a second function unit 220 , a control unit 230 , a UI unit 240 , UI: User Interface), a signal receiving unit 250 and It may include an SOC change unit 260 and the like.

The first function unit 210 may perform a first function by charging and discharging the ESS. The first function may be voltage regulation or frequency regulation of the power grid interlocked with the ESS.

The first function unit 210 may perform the first function by charging and discharging the ESS having the first SOC state at the starting point (time point) of the function. The first SOC state is a state in which the wear index of the ESS is considered, and may be, for example, 0.5.

When voltage regulation or frequency regulation is performed, the SOC of the ESS may fluctuate within a certain range. Such a certain range should correspond to the safe operating range of the ESS. The safe operating range is generally determined from SOC 0.1 or more to SOC 0.9 or less, and the control device 130 determines the first SOC at the time of function so that the SOC variation range of the ESS by voltage regulation or frequency regulation falls within this safe operating range. can

And, the control device 130 may determine the first SOC of the functional time in consideration of the wear index. In general, the wear index is the smallest in the vicinity of 0.5 of the ESS, and the wear index increases as the distance from 0.5 is increased.

The second function unit 220 may perform a second function by charging and discharging the ESS. The second function may be a demand response function. The second function unit 220 may absorb the excess power of the power grid by using the ESS, and may supply the insufficient amount of power to the power grid using the ESS.

When the second function unit 220 performs the demand response function, the SOC of the ESS may increase or decrease in one direction. In this case, the control device may determine the time point SOC (second SOC) of the second function so that the SOC of the ESS according to the execution of the second function falls within the safe operating range. And, the control device may determine the second SOC so that the wear of the ESS is minimized in consideration of the wear index.

For example, assuming that the SOC of the ESS increases by 0.4 according to the performance of demand response, the second SOC in consideration of the safe operating range may be a value of 0.5 or less to 0.1 or more. The second SOC may be determined such that the index is minimized. In general, when the ESS absorbs over-generation of the power grid, the second SOC may be set lower than the first SOC. And, conversely, when the ESS supplements the excessive demand of the power grid, the second SOC may be set higher than the first SOC.

The SOC change unit 260 may change the SOC state of the ESS to the first SOC state or the second SOC state prior to performing the functions of the first functional unit 210 and the second functional unit 220 . For example, when the ESS switches from performing the first function to performing the second function, the SOC change unit 260 may charge or discharge the ESS to change the SOC to the second SOC. Alternatively, the SOC change unit 260 may change the SOC to the first SOC by charging or discharging the ESS when the ESS switches from performing the second function to performing the first function.

The control unit 230 may control the overall configuration of the control device 130 . For example, the controller 230 may determine whether to operate each component. The control unit 230 may determine the operation of the first function unit 210 or the second function unit 220 and operate the first function unit 210 or the second function unit 220 .

Further, when the performance of the first function or the second function is predicted, the control unit 230 may operate the SOC change unit 260 to change the SOC of the ESS.

The UI unit 240 may provide information to the user by outputting information generated by the control device 130 to the display device. In addition, the UI unit 240 may recognize a user manipulation signal through a keyboard, mouse, touch screen, or the like, and transmit the user manipulation signal to the controller 230 .

The signal receiving unit 250 is a component capable of communicating with the outside, and receives a DR (Demand Response) signal from the power grid management device and sets the DR time and DR amount included in the DR signal to the control unit 230 and/or the second function unit. It can be passed to (220).

4 is a diagram illustrating a frequency curve and a threshold value of a power grid according to an embodiment.

Referring to FIG. 4 , as shown in the first curve 310 , the frequency of the power grid may vary with time. The frequency fluctuates according to the imbalance between supply and demand in the power grid. If supply and demand match, the frequency may be kept constant. However, if supply and demand imbalance occurs, the frequency may rise or fall.

When the frequency of the power grid is out of a certain range, some devices connected to the power grid may fail. In order to prevent such a failure, the power grid system may manage the frequency of the power grid in a certain range.

The first functional unit included in the control device sets the upper limit value 320 and the lower limit threshold value 330, and when the frequency of the power grid becomes greater than the upper limit threshold value 320 or smaller than the lower limit threshold value 330, the ESS It can be operated to compensate for the imbalance of supply and demand in the power grid.

In this control, the control device may determine the SOC (first SOC) at the time of function so that the reduction in the lifespan of the ESS is minimized. In addition, prior to performing the frequency regulation function, the SOC of the ESS may be changed to the first SOC.

The control device may predict performance of the first function, for example, a frequency regulation function. The control device may monitor the frequency of the power grid, compare the monitoring value and the threshold value, and when the monitoring value enters within a predetermined range from the threshold value, predict the performance of the first function and change the SOC of the ESS to the first SOC.

4, the preliminary upper limit threshold value 340 and the preliminary lower limit threshold value 350 are further illustrated. When the monitoring value exceeds the preliminary upper limit threshold value 340 or falls below the preliminary lower limit threshold value 350, the control device may determine that the performance of the first function is predicted and change the SOC of the ESS to the first SOC.

These thresholds and preliminary thresholds may be determined by a user's input, and the control device according to an embodiment provides three modes, a stability priority mode, an intermediate mode, and an economy priority mode, through the display device for the convenience of the user. , a threshold value may be determined using a user manipulation signal for this.

5 is a layout view of a user manipulation button according to an exemplary embodiment.

Referring to FIG. 5 , a first button 410 , a second button 420 , and a third button 430 may be disposed on the display device 400 .

When the first button 410 is determined by a user manipulation, the control mode is set to the stability priority mode, and the control device may set the threshold value close to the target value. And, when the third button 430 is determined by user manipulation, the control mode is set to the economical priority mode, and the control device may set the threshold value away from the target value. And, when the second button 420 is determined by the user manipulation, the control mode is set to the intermediate mode, and the threshold value may be set to a value between the set values in the stability priority mode and the economic efficiency priority mode.

The control device may determine the threshold value according to the user manipulation signal, and may also determine the input ratio of the ESS in each mode. For example, the control device may set the input ratio of the ESS to be higher in the stability priority mode than in the economic efficiency priority mode.

6 is a diagram for explaining a second function according to an embodiment.

Referring to FIG. 6 , a difference 530 between the power generation curve 510 and the load curve 520 for the power grid may occur over time, and this difference 530 may cause problems related to imbalance in supply and demand of the power grid. .

In order to minimize the difference 530 , the power grid management device may reduce the supply-demand imbalance by transmitting the DR signal 540 to the microgrid including the ESS.

In DR (Demand Response), the power grid management device and the control device can recognize each other according to a prior contract, and information related thereto can be transmitted from the power grid management device to the control device before the start of the demand response.

The control device may perform the second function in the DR times T1 to T2 included in the DR signal 540 . In this case, the control device may optimally determine the start SOC (second SOC) of the second function in order to minimize the reduction in the lifespan of the ESS, and change the SOC of the ESS to the second SOC before the second function is performed.

The determination of the second SOC may be differently determined according to the total accumulated DR amount 550 of the DR time. For example, depending on the size of the total accumulated DR amount 550, the SOC variation of the ESS may be 0.4 or 0.5. The control device may determine the second SOC in consideration of the safe operating range and wear index of the ESS. In addition, the control device may change the SOC of the ESS to the second SOC before the second function is performed.

For example, when the control device approaches within a predetermined time from the time point T1 of the DR time, the control device may predict the performance of the second function and change the SOC of the ESS to the second SOC.

7 is a flowchart of an ESS control method according to an embodiment.

Referring to FIG. 7 , the control device may perform the first function by charging and discharging the ESS having the first SOC state at the time of the first function ( S600 ).

Then, the control device may perform the second function by charging and discharging the ESS having the second SOC state at the time of the second function ( S602 ).

In addition, the control device controls the ESS through charging or discharging before switching from the first function step (S600) to the second function step (S602) or from the second function step (S602) to the first function step (S600). The second SOC state or the first SOC state may be made (S604).

Here, the first function may be voltage regulation or frequency regulation of the power grid interlocked with the ESS, and the second function may be a demand response using the ESS.

When the ESS absorbs over-generation of the power grid in the second function step S602, the second SOC may be set lower than the first SOC.

The first SOC may be 0.5.

The control method may further include a control step (not shown) of determining whether to perform the first function step S600 or the second function step S602, and in the control step, the first function step S600 or the second function step S602 When the performance of the function step S602 is predicted, the control device may determine to perform the SOC changing step S604 .

In the control step, the control device compares the monitoring value with the threshold value, and when the monitoring value enters within a certain range from the threshold value, predicts the performance of the first function step S600 and determines the performance of the SOC change step S604 can

Here, the threshold value may be determined by one of the safety priority mode, the intermediate mode, and the economy priority mode selected by the user manipulation signal.

Also, the input ratio of the ESS in the first function may be determined by the determined mode.

The control method further includes a step (not shown) of receiving a DR signal including a DR time and a DR amount, and in the control step, when the control device approaches within a predetermined time at the time of the DR time, a second functional step ( It is possible to predict the performance of S602) and determine the performance of the SOC change step (S604).

And, in the control step, the control device may reset the second SOC according to the DR time and DR amount.

8 is a flowchart of a method for performing a first function according to an embodiment.

Referring to FIG. 8 , the control device may set a threshold value according to a user manipulation signal ( S700 ).

Then, the control device may monitor a specific value of the power grid - for example, voltage or frequency (S702).

When the monitoring value approaches the threshold value, the control device may determine that the first function is predicted to be performed (S704).

And, when the performance of the first function is predicted, the control device may change the SOC of the ESS to the first SOC suitable for the performance of the first function ( S706 ).

Then, the control device may control the ESS in the first SOC state to perform the first function (S708).

9 is a flowchart of a method for performing a second function according to an embodiment.

Referring to FIG. 9 , the control device may receive a DR signal including a DR time and a DR amount ( S800 ).

Then, the control device may monitor the time (S802).

And, when the time approaches the time of the DR time, the control device may determine that the performance of the second function is predicted ( S804 ).

Then, the control device may reset the second SOC according to the DR time and DR amount (S806) and change the SOC of the ESS to the second SOC (S808).

Then, the control device may perform the second function by using the ESS (S810).

As described above, according to the present embodiment, it is possible to increase the utilization ratio of the ESS by using the ESS for multiple functions. In addition, according to this embodiment, it is possible to increase the utilization time of the ESS by making the wear of the ESS minimum or optimal for the same use.

Terms such as "include", "comprise" or "have" described above mean that the corresponding component may be embedded, unless otherwise stated, and does not exclude other components. It should be construed as being able to further include other components. All terms, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs, unless otherwise defined. Terms commonly used, such as those defined in the dictionary, should be interpreted as being consistent with the meaning of the context of the related art, and should not be interpreted in an ideal or excessively formal meaning unless explicitly defined in the present invention.

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.

Claims (10)

a first functional step of performing the first function by charging and discharging an Energy Storage System (ESS) having a first state-of-charge (SOC) state at the start time of the first function;
a second functional step of charging and discharging the ESS having a second SOC state at the start time of a second function to perform the second function; and
SOC that puts the ESS into the second SOC state or the first SOC state through charging or discharging before switching from the first functional stage to the second functional stage or from the second functional stage to the first functional stage change step
including,
The first function is voltage regulation or frequency regulation of the power grid interlocked with the ESS, and the second function is a demand response using the ESS,
In the second function step, when the ESS absorbs the over-generation of the power grid, the second SOC is set lower than the first SOC. delete delete According to claim 1,
The first SOC is 0.5 ESS control method. According to claim 1,
Further comprising a control step of determining the performance of the first functional step or the second functional step,
In the control step,
The ESS control method for determining the execution of the SOC changing step when the performance of the first functional step or the second functional step is predicted. 6. The method of claim 5,
In the control step,
An ESS control method for comparing a monitoring value and a threshold value, and predicting the performance of the first functional step and determining the execution of the SOC changing step when the monitoring value enters within a predetermined range from the threshold value. a first functional step of performing the first function by charging and discharging an Energy Storage System (ESS) having a first state-of-charge (SOC) state at the start time of the first function;
a second functional step of charging and discharging the ESS having a second SOC state at the start time of a second function to perform the second function; and
SOC that puts the ESS into the second SOC state or the first SOC state through charging or discharging before switching from the first functional stage to the second functional stage or from the second functional stage to the first functional stage change step
including,
Further comprising a control step of determining the performance of the first functional step or the second functional step,
In the control step, when the performance of the first functional step or the second functional step is predicted, it is determined that the SOC changing step is performed,
In the control step, a monitoring value and a threshold value are compared, and when the monitoring value enters within a predetermined range from the threshold value, the performance of the first functional step is predicted and the execution of the SOC changing step is determined,
The threshold value is an ESS control method that is determined by one of a safety priority mode, an intermediate mode, and an economy priority mode selected by a user manipulation signal. 8. The method of claim 7,
The ESS control method in which the input ratio of the ESS in the first function is also determined by the determined mode. 8. The method of claim 7,
Further comprising a DR receiving step of receiving a DR (Demand Response) signal including a DR (Demand Response) time and DR amount,
In the control step,
ESS control method for predicting the performance of the second functional step and determining the execution of the SOC changing step when the DR time point is approached within a predetermined time. 10. The method of claim 9,
In the control step,
ESS control method for resetting the second SOC according to the DR time and the DR amount.

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