KR101802038B1 - Controlling method for ESS - Google Patents

Abstract

A control method of an energy storage system according to the present invention includes a charging mode in which the battery is fully charged in a charging period of the battery; And a discharge mode in which the battery is fully discharged in a discharge interval of the battery is automatically performed. According to this, it is possible to achieve the effect of saving power charges and preventing deterioration of the system.

Description

[0001] Controlling method for ESS [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method of an energy storage system, and more particularly, to a control method of an energy storage system in which a system, a load, and a battery are connected by switches so that power supply is switched to each other.

Electricity charging systems for industrial and educational high voltage electric power are composed of basic charge, electricity charge, and power factor charge.

The base rate is based on a specific maximum demand power of several months, including the survey month. The maximum demanded power is not calculated at the time of day under light load, and is set to an average power amount of 15 minutes which is the maximum average used power amount. The time reference at this time is based on the time zone of the KEPCO watt hour meter.

The above electric power charge is calculated based on the electric power consumption and the electric power unit cost of the light load / intermediate load / peak load time.

Under the above electricity tariff system, techniques for lowering the electricity tariff as much as possible are known as follows.

First, the power charge can be lowered by lowering the maximum demand power which is a standard for the calculation of the basic charge. This technique is called peak shaving. Another alternative would be to lower the electricity bill. For this purpose, there is a technique of charging the battery at a light load time at a low power unit price, and discharging the battery at an intermediate load or a peak load time period in which the power unit cost is high, thereby lowering the charge amount. This is called load leveling.

The peak load reduction technique and the load control technique are advantageous not only in terms of the electric power cost of the electric power consumer, but also in terms of the electric power supply side. This is because it is difficult to change the power supply amount according to the above-mentioned period, while the power demand varies with a certain pattern when the day and the season are taken as cycles. Accordingly, it can be said that adjusting the power demand to a level similar to the amount of power supply is advantageous in the power industry as a whole.

As a method of controlling the electric power demand, WO2013125909, an apparatus and a method for scheduling a power storage device have been proposed. The method is characterized in establishing an efficient power storage scheme by communicating with a plurality of nodes to periodically control each power storage device. It is also focused on the integrated operation of multiple power storage units in a given area.

Due to the local limitations of such a wide area, there is a limitation in the control method of the energy storage system that can be optimally operated in a specific industrial site or a training site. For example, there is a problem that the life of the battery is shortened because charging and discharging are performed from time to time, rather than from a complete discharge after a full charge. Is a system in which a load is continuously applied to a power conversion system (PCS: Power Control System), which is not desirable from the viewpoint of system load management. This is a priority for peak load reduction technology, and there is a limit to not properly utilizing load control technology.

WO2013125909, APPARATUS AND METHOD FOR SCHEDULING POWER STORAGE DEVICE

The present invention is based on the above problems and proposes a control method of an energy storage system in which charging and discharging are performed with full charge and full discharge based on a predetermined cycle to thereby increase the life of the battery.

The present invention proposes a control method of an energy storage system that can reduce the system load of a power conversion apparatus to extend the life of the power conversion apparatus.

The present invention proposes a control method of an energy storage system capable of minimizing a power charge by operating a peak load reduction technique and a load control technology together.

According to the present invention, in order to suppress the intermittent charging / discharging and increase the service life of the battery, a charging mode in which the battery is fully charged in the charging period of the battery; And a discharge mode in which the battery is completely discharged in a discharge interval of the battery. At this time, no discharge is performed in the charge mode, and no charge is performed in the discharge mode.

Obtaining a rated discharge duration when discharging the battery remaining amount with the rated discharge of the power conversion apparatus in the discharge interval; And discharging the battery with the rated discharge of the power inverter when the remaining time of the discharge interval reaches the rated discharge duration.

A normal charging section for performing charging based on the time of the charging section in the charging mode; And a rapid charging section for charging the battery with a rated charging capacity of the power converter following the normal charging section.

In order to reduce the system load of the power conversion apparatus to extend the lifetime of the power conversion apparatus, when the full charge is reached during the normal charge period and the rapid charge period, the power conversion apparatus enters the standby mode And when the standby mode lasts for a predetermined time, the power conversion apparatus enters a stop mode.

Further, the control unit controls the power conversion apparatus to start up before a certain time before the charging section ends.

Further, if the unit discharge power is larger than the rated discharge capacity of the power inverter, the discharge is discharged to the rated discharge capacity of the power inverter, otherwise, the unit discharge power is discharged.

The present invention relates to a method of operating a peak load reduction technique and a load control technique in order to minimize a power charge by operating together with a peak load reduction technique and a load control technique to obtain a discharge power amount that is insufficient for a first time before the predicted power exceeds a target power, Acquires a unit discharge electric power for discharging the electric energy from the battery for a second time after the present time, and discharges the unit electric discharge electric power for the second time.

At this time, the first time may be equal to or greater than the second time.

Alternatively, when the amount of power consumed in the load for the first time and the target amount of power for the first time are obtained and the amount of power consumption exceeds the target amount of power, And discharges the unit discharge power for the second time with the unit discharge power.

If there is an interval in which the operator does not input a schedule for various uses of the energy storage system, the automatic operation mode described above may be applied to the interval.

According to the present invention, since the full charge and the full discharge are performed, the life of the battery and the battery use efficiency can be extended.

The present invention can extend the lifetime of the power inverter by reducing the system load and unnecessary on-off operation of the power inverter.

The present invention proposes a control method of an energy storage system capable of minimizing a power charge by appropriately operating a peak load reduction technique and a load control technology.

1 is a block diagram briefly illustrating operation of an energy storage system;
2 is an exemplary diagram of power demand and power supply;
3 is a view for explaining a charge mode control method in an automatic operation mode;
4 is an embodiment of a discharge mode control method in an automatic operation mode.
5 shows another embodiment of the discharge mode control method in the automatic operation mode.
6 is a still further embodiment of a discharge mode control method in an automatic operation mode.

Hereinafter, the present invention will be described in detail with reference to the drawings. However, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. It will be understood that they are also included within the scope of the present invention.

The embodiment is characterized by positively controlling charging and discharging of the battery.

The battery has the effect of reducing the overall life of the battery due to frequent charging and discharging operations. In addition, the battery can overheat and operate irreversibly when the charge amount exceeds the maximum charge amount (SOCmax). Further, when the charged amount becomes less than or equal to the minimum charged amount SOCmin, the battery deteriorates and can not recover. In an embodiment of the present invention, the charging and discharging of the battery are performed in a state in which the charging and discharging of the battery is limited to a certain range within the upper and lower limits of the state of charge (SOC) of the battery.

1 is a block diagram briefly illustrating operation of an energy storage system.

1, there is shown a system 1 provided as an external power supply source, a load 3 as a power demanded by the system, a battery 2 serving as an energy storage device of the energy storage system, A load 3 and a power conversion unit 4 for controlling the power distribution of the battery 2 and a control unit 5 for controlling the power conversion unit 4. [

The control unit 5 is provided with predetermined communication means, calculation means and memory. The control unit 5 can process the information obtained from the communication unit by the calculation unit to control the respective components. Various information necessary for the operation of the control unit 5 may be stored in the memory. A switch may be included in the power conversion device 4 to switch the power supply direction.

Under the control of the control unit, the power charge can be reduced while positively coping with the fluctuation of the load (3).

Figure 2 is an exemplary diagram of power demand and power supply.

Referring to Fig. 2, a line indicated by a curve is a line representing a variation of the load 3, which can be referred to as a load variation line. Section of the battery is the light load section as the charge section, the section "C" is the maximum load section as the discharge section, and the section "B" Can be expected. Charging or discharging may not occur in the waiting section.

When the load variation line is referred to, it can be seen that the load becomes the maximum in the section "C" and the load becomes the minimum in the section "A ".

In order to cope with this, the battery 2 may be charged in the "A" period, and the battery 2 may be discharged to the load 3 in the "C" period. The shaded blocks will be approximately equal to the sum of the "A" periods plus the "C" periods. According to this, the maximum demand power (peak) drops from peak 1 to peak 2. Therefore, it can be seen that the peak load reduction technique is operated. Also, if the power rate of the "C" section is higher than the power rate of the section "A "

The above-described diagram can be automatically operated under the control of the control unit 5. [

In Fig. 2, the automatic operation mode applied to the charging section will be described with reference to the charging mode control method shown in Fig.

The charging mode control method allows charging to be performed without burdening the energy storage system such as the power conversion device 4 and the battery 2 up to the maximum charging amount SOCmax of the battery 2. [ For this purpose, the charging mode can charge the battery with the set charging power up to a certain time before the end time between the light ends and charge the battery with the maximum power after a certain time. Here, the predetermined time may be set to 10 minutes before the end of light load.

In addition, the power conversion device 4 can be stopped when the standby state of the power conversion feast 4 is sustained for a certain period of time. According to this, since the power conversion device 4 is switched to the stop state, unnecessary power is wasted and the system can be maintained in a stable state. Here, the duration of the standby state can be set to 5 minutes.

Will be described in more detail with reference to FIG.

The charging mode is initiated between the light ends. In this case, in order to facilitate the calculation of the daily operation history even if the light supply time of the power supply source is started, the charge mode may be set to a predetermined time after the light load time. For example, when the light-load supply time of the power supply source is 23 hours, the start time of the charge mode can be set to 0 hour.

When the light load start time is started, it is determined whether it is a normal charge period (S1). The power supplied to the normal charging section charges the battery 2 with a charging power that can charge the battery during the entire time of the light load time.

The normal charging section will be described by way of example. If the rated capacity of the power converter 4 is 1 MW, the capacity of the battery 2 is 2 MWh, and the light load time is 0 to 9 hours, the battery of 2 MWh is charged for 7 hours The battery can be charged to about 300 kW, which can be fully charged in a short time). The step of determining whether the normal charging interval is applied (S1) may be continuously performed at intervals of 30 seconds.

By performing the normal charging interval, the battery can be gradually charged without requiring the system.

If it is determined in the determining step S1 that the normal charging interval has been satisfied, it is determined whether the current charging amount SOC of the battery is the maximum charging amount SOCmax of the battery (S4). If it is determined that the current amount of charge of the battery does not exceed the maximum charge amount of the battery as a result of the determination of the charge amount of the battery (S5), the current charge amount of the battery exceeds the maximum charge amount of the battery The power conversion device 4 is put in a standby state (S6).

The actual amount of charge of the battery may vary depending on external conditions. Therefore, it may be necessary to continuously judge the state of the battery even in the normal charging section to control the maximum charging amount so as not to exceed the maximum charging amount.

Thereafter, when the standby state S6 of the power conversion apparatus continues for a predetermined time (S7), the power conversion apparatus 4 is stopped (S8) to protect the battery and prevent unnecessary operation. Here, the standby state duration of the power converter can be set to 5 minutes.

In the case where it is determined that the normal charging section is not the normal charging section in the determination step S1 of the normal charging section, for example, it can be set to 2 hours before the ending time under light load. This is for quickly charging the battery to the maximum charge amount when the maximum charge amount is not reached, while the light load time (0-9 hours) is a certain time before the end.

If it is determined in the quick charge interval determination step S2 that it is the fast charge period, it is further determined whether the maximum charge amount SOCmax of the battery has been reached (S9). When the charge amount of the battery reaches the maximum charge amount, (4) enters the standby mode (S7), and thereafter enters the stopping step (S8) of the power conversion apparatus. However, when the maximum charge amount of the battery 2 is not reached in the step S9 of determining the maximum charge amount of the battery, the rated charge capacity of the power conversion device 4 is charged. For example, when the rated output of the power conversion device 4 is 1 MW, the battery is rapidly charged at 1 MW.

If it is determined that both the normal charging period and the fast charging period are not satisfied, the power conversion apparatus 4 is prepared to start up at a predetermined time before the light load time ends (Step S1) S3). Here, the fixed time can be set to 5 minutes. For example, when the light load ends at 9 o'clock, it is determined at 8:55 that the light load end step is reached in the light load end determination step (S3). Thereafter, the process may proceed to step S11 in which the power conversion apparatus is started.

According to this, the power conversion device can be advanced to the discharge mode before the end of the charge mode.

According to the charging mode, the battery can always reach the full charge (maximum charge) stage. By adjusting the charging capacity of the energy storage device in two steps, the system can operate stably. When the operation of the power conversion apparatus is not required, the power conversion apparatus is controlled to be in an off state, thereby preventing unnecessary operation of the system. For example, malfunction of the product due to heat generation can be prevented.

Hereinafter, the automatic operation mode applied to the discharge interval in FIG. 2 will be described.

In the automatic operation mode applied to the discharge period, a discharge mode in which the maximum demand power (peak) supplied from the system 1 is not exceeded the target power, and a discharge mode in which all of the available battery power remaining before the end of the discharge interval A discharge mode capable of discharging can be realized. Each of the discharge modes described above may be operated together in the discharge period. The discharge mode may be operated together as a whole in the discharge period.

As a method for managing the target power supplied from the system, there are a discharge mode using a maximum demand power control controller (DC: Demand Controller) and a discharge mode using a meter or a relay. The discharge mode using the meter or the relay can be used when there is no maximum demand power monitoring and control device. The discharge of all the power of the battery in the discharge period can start before a predetermined time based on the light load start time.

First, a discharge mode using the maximum demand power control apparatus among the automatic operation modes applied to the discharge interval in FIG. 2 will be described with reference to a discharge mode control method shown in FIG.

Referring to FIG. 4, the predicted power is received from the maximum demand power monitoring controller DC provided from the power supply source. At this time, the predicted power may be provided every second and may be provided as an accumulated value of a 15-minute interval. The cumulative value of the 15-minute interval may be a target power reflected at the time of calculating the base rate.

It is determined whether the predicted power exceeds the target power (S31). If not, the battery 2 can be discharged without performing the discharge. Here, the target power may be a maximum demand power agreed by the power supply source and the power demander.

When the predicted power exceeds the target power in the step S31 of comparing the predicted power with the target power, the discharge power amount is calculated (S32), and the unit discharge power is obtained using the discharge power amount ( S33). Here, the discharge power amount is a value for accumulation up to a reference time (here, it may be the current time at any point within 15 minutes). Therefore, the amount of discharge electric power to which the battery 2 is to be discharged can be calculated as (predicted power (kW) - target power (kW)) × reference time (minute) / 60.

For example, when the predicted power is 3050 kW, the target power is 3000 kW, and the reference time is 6 minutes, the discharge power amount is 5 kWh. In other words, the predicted power is an accumulated value for a reference time which is a current time point, which means that the predicted power is exceeded by an average of 50 kW for 6 minutes.

The unit discharge power can be determined with reference to the discharge power amount. The discharge mode using the maximum demand power detection control device may be performed with a cycle of 30 seconds. Therefore, it can be understood that the discharge power amount is output for 30 seconds. The unit discharge power can be calculated as a discharge power amount (kWh) × a reference time (minute) /0.5 (minute).

For example, since the discharge power amount is 5 kWh and the reference time is 6 minutes, the unit discharge power can be calculated as 600 kWh. It can be understood that the unit discharge electric power is discharged from the battery within 30 seconds, which corresponds to the difference between the predicted electric power and the target electric power in the range of the reference time (6 minutes) at the present time. In this case, it is presumed that a considerable amount of power was consumed in the immediately preceding 30 seconds since the discharge would have been similarly performed before.

Thereafter, the unit discharge power is compared with the rated power of the power converter (S34). If the unit discharge power is greater than the rated power of the power conversion apparatus, the battery is discharged with the rated discharge of the power conversion apparatus (S36). Otherwise, the battery is discharged with the unit discharge power (S35) .

As a result, the discharging operation exceeding the rated power does not occur, so that the system is not overloaded. In addition, the discharge amount of the battery which is insufficient until now can be further discharged in the next cycle.

Next, the discharge mode using the meter or the relay in the automatic operation mode applied to the discharge interval in FIG. 2 will be described with reference to the discharge mode control method shown in FIG. This discharge mode control method can be performed with a cycle of 30 seconds.

Referring to FIG. 5, the target amount of power kWh is first obtained (S41), and the amount of power consumption kWh is obtained (S42).

The target power amount represents a cumulative amount of target power up to the current reference time. Therefore, the target amount of electric power can be obtained by the target electric power (kWh) × the reference time (minute) / 60. The amount of power consumption is the cumulative effective power amount from the start of the reference time to the reference time (current time).

Therefore, the amount of power consumption can be obtained from the reference time active power amount (kWh) - the effective power amount (kWh) at the start time of the reference time. The actual amount of electric power can be measured by a relay or a meter installed on the field, and the target amount of electric power can be calculated by being determined in advance by agreement between the electric power supply source and the electric power demanding place.

If the target power amount (kWh) and the power consumption amount (kWh) are obtained, the two values are compared (S43). The target amount of power and the amount of power consumption are compared. If the amount of power consumption is large, the discharge from the battery is not required, and the cycle of the current discharge mode control method can be immediately terminated.

However, if the target amount of power is large by comparing the target amount of power with the amount of power consumption, the battery should be discharged to the unit discharge power, and the process proceeds to step S44 of first obtaining the unit discharge power.

The control method of the present discharge mode is performed at intervals of 30 seconds. It can be understood that the discharge power amount corresponding to the value of the power consumption exceeding the target power amount is output from the battery for 30 seconds. Then, the unit discharge power can be calculated by (power consumption amount (kWh) - target amount of power (kWh)) × reference time (minute) /0.5 (minute).

For example, when the reference time active power amount (kWh) is 5002 kWh and the effective power amount (kWh) at the reference time start time is 4700 kWh, the power consumption amount is 302 kWh. When the target power is 3000 kW and the reference time is 6 minutes, the target power amount becomes 300 kWh. Then, the unit discharge power may be 240 kW.

Thereafter, it is determined whether the unit discharge power is greater than the rated power of the power conversion apparatus (S45). If the unit discharge power is greater than the rated power, the PCS rated discharge is performed (S47). Otherwise, the unit discharge power is discharged (S46).

As a result, the discharging operation exceeding the rated power does not occur, so that the system is not overloaded. In addition, the discharge amount of the battery which is insufficient until now can be further discharged in the next cycle.

Lastly, among the automatic operation modes applied to the discharge period in FIG. 2, a discharge mode that can discharge all remaining power of the battery before the end of the discharge interval is referred to as a discharge mode control method shown in FIG. 6 . This discharge mode control method can be performed with a cycle of 30 seconds.

When this discharge mode control method is performed, firstly, the rated discharge duration time of the power conversion apparatus is obtained (S21). The rated discharge duration of the power inverter represents a time at which the remaining battery capacity can be maintained as the rated discharge of the power inverter at the present time. For example, in the case where the rated discharge of the power conversion apparatus is 1 MW and the remaining amount of the battery is 1.2 MWh, the rated discharge duration of the power conversion apparatus can be grasped as 72 minutes.

Thereafter, the current time is compared with a value obtained by subtracting the rated discharge duration of the power converter from the light load start time (S22). In the comparison step S22, if the current time is large, the rated discharge of the power conversion apparatus is performed (S23). Otherwise, the power supplied from the system, which has already been described, is not exceeded (S24). ≪ / RTI > Here, the light load start time may be the end time of the discharge section.

For example, if the rated discharge duration of the power conversion apparatus is 72 minutes and the light-load start time is 23:00, the rated discharge execution step (S23) of the power conversion apparatus is performed from the current time of 21:38.

According to this operation, one full charge and one full discharge are performed when the battery is in a unit of one day, and the charging / discharging operation repeatedly complicated is not performed. Therefore, the life of the battery is prolonged. Also, by performing the full discharge, the load control technique can be utilized more positively.

The control method of the energy storage system of the present invention may further include the following embodiments.

First, in addition to the automatic operation mode described above, the embodiment may further include a manual mode and a manual schedule mode. The manual mode is characterized in that the operator always manually operates the energy storage system. The passive schedule mode allows the energy storage system to operate in accordance with a plan previously entered by the operator only in a specific start band.

The automatic operation mode proposed in the embodiment can be applied to a time band which is not previously specified as the user's schedule in the manual schedule mode. In this case, the advantages obtained by the automatic operation mode can be obtained.

As another embodiment, one of the plurality of discharge modes applied to the discharge section may be applied and the other may not be applied, and two or more discharge modes may be applied together. When two or more discharge modes are applied together, a more accurate mode may be used selectively or as an average value of the various modes.

According to the present invention, in an energy storage device actually used in an industrial field, the lifetime of the battery and the power conversion device can be maximized, and the peak load reduction technology and the load control technology can be operated together to minimize the power charge.

1: System
2: Battery
3: Load
4: Power converter
5:

Claims (14)

A power control method for an energy storage system including a power conversion system for controlling a power distribution system between a load and a battery, a power supply source system, a power demand source, and a controller for controlling the power conversion system,
In the control unit,
A charging mode in which the battery is fully charged in a charging interval of the battery; And
A discharge mode in which the battery is completely discharged in a discharge interval of the battery is automatically performed,
In the charging mode,
A normal charging section for performing charging based on the time of the charging section; And
If it is determined that the battery is not to be fully charged in the normal charging period before a predetermined time before the charging period ends, And a rapid charging section for charging the battery with the rated charging capacity of the power converter following the normal charging section. The method according to claim 1,
Wherein the discharging is not performed in the charging mode and the charging is not performed in the discharging mode. The method according to claim 1,
Wherein the charge section is a light load section having a small load and the discharge section is a maximum load section. delete The method according to claim 1,
Wherein when the full charge is reached during the normal charge period and the rapid charge period, the power conversion apparatus enters a standby mode. 6. The method of claim 5,
And when the standby mode continues for a predetermined time, enters the power conversion apparatus into a stop mode. The method according to claim 6,
Further comprising the steps of: starting the power conversion apparatus before a predetermined time elapses from the end of the charging period even if the stop mode continues. The method according to claim 1,
In the discharge mode,
Wherein the supply power from the system in the discharge section is controlled so as not to exceed a target power that is preliminarily set as a maximum value. 9. The method of claim 8,
In order to prevent the supply power from exceeding the target power,
Receiving a predicted power, which is an average power accumulated during a reference time in a predetermined period, from the power supply;
Obtaining a discharge power amount corresponding to a difference in the target power from the predicted power during the reference time as a value shortened in the present first time when the predicted power exceeds the target power;
Obtaining a unit discharge power for discharging the discharge electric power amount from the battery for a second time after the present time; And
And if the unit discharge power is greater than the rated discharge capacity of the power inverter, discharging at the rated discharge capacity of the power inverter, otherwise discharging at the unit discharge power. 10. The method of claim 9,
Wherein the first time is greater than or equal to the second time. 9. The method of claim 8,
Obtaining a target amount of power consumed in the load during a first time and a target amount of power that is an accumulation amount of the target power as a target amount of power for the first time;
Acquiring a unit discharge power for discharging a power equal to the difference between the power consumption amount and the target power amount for a second time when the power consumption amount exceeds the target power amount; And
And if the unit discharge power is greater than the rated discharge capacity of the power inverter, discharging at the rated discharge capacity of the power inverter, otherwise discharging at the unit discharge power. 12. The method of claim 11,
Wherein the first time is greater than or equal to the second time. The method according to claim 1,
In the discharge mode,
Obtaining a rated discharge duration at the time of discharging the battery remaining amount with the rated discharge of the power conversion apparatus; And
And discharging the battery with the rated discharge of the power conversion apparatus when the remaining time of the discharge section reaches the rated discharge duration. A control method according to any one of claims 1 to 3 and 5 to 13, wherein the control method is applied to and operated in an interval in which an operator does not input a schedule.

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