KR20160112628A - Ship, control system for ESS and method thereof - Google Patents

Abstract

A ship, and a control system and method for an energy storage system (ESS) are provided. The ship, according to an embodiment of the present invention, comprises: an ESS which is charged with the power generated from a generator and discharges the charged power to be supplied to power equipment; a receiver which receives the sailing procedure and real-time position information of the ship; and a controller which provides a charge signal or a discharge signal to the ESS on the basis of the sailing procedure and real-time position information of the ship. Therefore, the present invention improves power efficiency.

Description

Ship, ESS control system and method {Ship, control system for ESS and method thereof}

The present invention relates to a ship, an ESS control system and method, and more particularly, to a ship, an ESS control system, and a method capable of charging or discharging electric power.

An energy storage system (ESS) is a storage device that stores excess power generated by a generator and temporarily delivers power when the power is insufficient.

Generally, an ESS includes a battery that is connected to a power generation system to charge the overproduced power and discharge the charged power to power the power system (e.g., load).

Korean Published Patent Application No. 10-2015-0011301 (May 30, 2015)

An object of the present invention is to provide a ship, an ESS control system and a method capable of improving power efficiency.

The problems to be solved by the present invention are not limited to the above-mentioned problems, and other matters not mentioned can be clearly understood by those skilled in the art from the following description.

To achieve the above object, according to one aspect of the present invention, there is provided an energy storage system comprising: an ESS (Energy Storage System) which is filled with electric power generated by a generator and discharges charged electric power to supply electric power to the electric power facility; A receiver for receiving ship's navigation information and real-time location information; And a controller for providing a charge signal or a discharge signal to the ESS based on the lane information and the real time location information.

The ESS may include a battery and a converter connected to the battery and the generator to convert the produced power into DC power and convert the charging power into AC power.

The lane information may include at least one of input / output information of a ship, operation information of a ship, information of Emission Control Areas (ECA), and information of ship marine power (AMP).

Also, the controller compares the lane information and the real-time location information to determine whether it is a first viewpoint or a second viewpoint, provides a charge signal to the ESS when the first viewpoint is present, The discharge signal can be supplied to the discharge cell.

The controller may determine that the first time when the amount of power produced by the generator during the voyage is greater than the amount of power supplied to the power facility, and when the amount of power produced by the power generator is less than the amount of power supplied, It can be judged.

Also, the controller may determine that the position of the ship included in the real-time position information is within the emission control area (ECA) region as the second time point.

Also, the controller may determine the time point before entering the emission control area (ECA) as the first time point.

Further, at the time of entering the emission control area, the ESS can be fully charged.

Also, the controller may determine the time point before entering the AMP non-existing port as the first time point.

Also, at the beginning of the riding operation for the AMP non-existing port, the ESS can be fully charged.

The controller may determine the first time when the charged amount of the ESS is less than the thruster operating power at a point in time before entering the AMP presence port. When the charged amount of the ESS is greater than the thruster operating power, It can be determined as the second time point.

Also, at the start of the riding operation for the AMP presence port, the ESS can maintain the thruster operating power amount.

The power management system may further include a power management system (PMS) for providing a first signal for increasing the operating rate to the generator at the first time point and providing a second signal for lowering the utilization rate to the generator at the second time point have.

According to an aspect of the present invention, there is provided an ESS control system including an ESS (Energy Storage System) that is charged with electric power generated by a generator and discharges charged electric power to supply electric power to the electric power facility; A navigation system for storing ship information of the ship; A measurement system for measuring real-time position information of the ship; A receiver for receiving the navigation information from the navigation system and receiving the real-time location information from the measurement system; And a controller for providing a charge signal or a discharge signal to the ESS based on the lane information and the real time location information.

Also, the controller compares the lane information and the real-time location information to determine whether it is a first viewpoint or a second viewpoint, provides a charge signal to the ESS when the first viewpoint is present, The discharge signal can be supplied to the discharge cell.

The power management system may further include a power management system (PMS) for providing a first signal for increasing the operating rate to the generator at the first time point and providing a second signal for lowering the utilization rate to the generator at the second time point have.

According to an aspect of the present invention, there is provided an ESS control method including: a first receiving step of receiving ship information; A second receiving step of receiving real-time position information of the ship; And a control step of providing a charge signal or a discharge signal to the ESS based on the lane information and the real time location information.

The control step may include a determining step of comparing the lane departure information with the real time location information to determine whether the lane departure time is a first time point or a second time point, providing a charging signal to the ESS when the first time point is present, And providing a discharge signal to the ESS when the ESS is at a time point.

The method may further include the step of providing a first signal for increasing the operating rate of the generator at the first time point and providing a second signal for lowering the utilization rate of the generator at the second time point.

Other specific details of the invention are included in the detailed description and drawings.

1 is a block diagram of a ship according to an embodiment of the present invention.
2 and 3 are schematic views of a ship grid according to an embodiment of the present invention.
4 is a schematic view illustrating an ESS of a ship according to an embodiment of the present invention.
5 is a graph showing the production power and the supply power of a ship according to an embodiment of the present invention.
6 to 9 are views showing the charged amount of the ESS according to the embodiment of the present invention according to the lane departure information of the ship.
10 is a block diagram of an ESS control system in accordance with an embodiment of the present invention.
11 is a flowchart of an ESS control method according to an embodiment of the present invention.
12 is a view showing a container line according to an embodiment of the present invention.
13 is a view showing an LNG line according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

Unless defined otherwise, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by one of ordinary skill in the art to which this invention belongs. Also, commonly used predefined terms are not ideally or excessively interpreted unless explicitly defined otherwise.

Also, terms used herein are for the purpose of illustrating embodiments and are not intended to limit the invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. It should be understood that the terms comprising and / or comprising the terms used in the specification do not exclude the presence or addition of one or more other elements, steps and / or operations in addition to the stated elements, steps and / use. And "and / or" include each and any combination of one or more of the mentioned items.

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

FIG. 1 is a block diagram of a ship according to an embodiment of the present invention. FIGS. 2 and 3 are schematic views of a ship grid according to an embodiment of the present invention. ESS. ≪ / RTI >

1, a ship according to an embodiment of the present invention includes a receiver 110, a controller 120, an ESS (Energy Storage System) 130, and a PMS (Power Management System) 140, And does not exclude additional configurations.

The receiver 110 receives the ship's lane information and the ship's real-time location information. At this time, the lane departure information of the ship is received from the navigation system located outside the ship, and the real time position information of the ship can be received from the GPS located inside the ship or from the position measurement system of the ship located outside the ship. However, if it is possible to receive the lane information of the ship and the real-time location information of the ship, the configuration of the receiver 110 may include all configurations applicable to the ordinary artisan in the technical field of the present invention.

Here, the ship information of the ship includes information on the entry and departure of the ship, flight information, emission control area (ECA) information, and port information provided with the ship's AMP (Alternative Maritime Power) But may include, but is not limited to, all information related to the operation of the ship.

The controller 120 provides a charge signal or a discharge signal to the ESS 130, which will be described later, on the basis of the ship information and the real-time position information of the ship received by the receiver 110. Specifically, since the charge information and the position information of the ship are compared with each other in real time to control charging or discharging of the ESS 130, it is possible to increase the lifetime of the ESS 130 and improve the power efficiency, have.

The controller 120 compares the lane departure information of the ship with the real time location information to determine whether it is the first time point or the second time point, provides the charging signal to the ESS 130 at the first time point, The discharge signal may be provided to the ESS 130.

The operation of the controller 120 will be described later in detail.

The ESS 130 is charged with electric power generated by the generator 150, discharges the charged electric power, and supplies the electric power to the electric power facility 160. This will be described in detail with reference to FIG. 2 to FIG.

Referring to FIG. 2, which illustrates an AC grid, an ESS 130 may include a battery 132, a battery 132, and a converter 134 coupled to the generator 150.

At this time, the converter 134 converts the produced electric power produced by the generator 150 into direct current power and provides it to the battery 132, converts the charged electric power charged in the battery 132 into AC power, ).

In some embodiments of the present invention, the generator 150 includes a diesel generator 150 capable of generating greater than 200 KW of high-capacity power. At this time, a plurality of diesel generators 150 may be connected in parallel to generate electric power for driving the electric power facility 160, but it is not limited thereto and can be variously changed. Here, the power plant 160 may include all the on-board loads 166 used in the ship as well as the thrusters 164 for propelling or redirecting the ship.

Specifically, the AC power generated by the generator 150 is converted to DC power at the AC / DC converter 134 and stored in the battery 132, and the DC power stored in the battery 132 is supplied to the DC / AC converter 134. [ And may be provided to the power facility 160 that is converted to AC power and driven by AC power.

Referring to FIG. 3, which illustrates a DC grid, the ESS 130 may include only a battery 132.

Specifically, the AC power generated in the generator 150 is converted to DC power in an AC / DC converter connected to the generator 150 and provided to the DC grid, and the converted DC power is supplied to the battery 132, Lt; / RTI > Also, the DC power stored in the battery 132 is provided directly on the DC grid and is provided to the thruster 164 driven by AC power through a DC power-driven in-line load 166 or a DC / AC converter . However, if the in-vessel load 166 uses AC power, a separate DC / AC converter may be provided between the DC grid and the in-vessel load 166.

Referring to FIG. 4, the ESS 130 may include an AC / DC converter 134, a battery 132, and a DC / AC converter 136.

Specifically, the AC power generated in the generator 150 is converted to DC power in the AC / DC converter 134 and stored in the battery 132, and the DC power stored in the battery 132 is supplied to the DC / AC converter 136. [ And may be provided to a power facility 160 that is converted to AC power and driven by AC power.

The connection and disposition of the above-described generator 150, ESS 130 and power plant 160 is only one example of the present invention, and includes all connections and arrangements to which a person skilled in the art applies in the technical field of the present invention .

The PMS 140 may provide a first signal for increasing the operating rate of the generator 150 in the first time and a second signal for lowering the operating rate of the generator 150 in the second time. Accordingly, it is possible to increase the amount of power supplied to the ESS 130 at the first time and to reduce the amount of power supplied to the ESS 130 at the second time.

FIG. 5 is a graph showing a production power and a supply power of a ship according to an embodiment of the present invention, and FIGS. 6 to 9 are graphs showing a charge amount of an ESS according to an embodiment of the present invention, to be.

Hereinafter, the operation of the controller 120 will be described in detail with reference to Figs. 5 to 9. Fig.

Referring to FIG. 6, the power load and the battery charge amount can be known when the ship departs and enters the AMP existing port, which is the port where the AMP exists.

At this time, the ship departs from the state where the battery charge amount of the ESS 130 is 100%, and the AMP is anchored at the existing port after the sailing. Here, AMP means a ship's offshore power source, which supplies the necessary power to operate the in-ship load without operating the generator 150 when the ship is stationed at the port.

The controller 120 determines the departure time t ₁₀ as the second time point and provides a discharge signal to the ESS 130. At this time, the thruster 164 can be driven through the electric power generated by the generator 150 and the electric power discharged from the ESS 130. In general, since the ship consumes much power consumed by the thrusters 164 driven at the time of entry and departure compared with the general power consumed during navigation, the capacity of the generator 150 is designed accordingly. Accordingly, power required for driving the thrusters 164 can be supplied through the ESS 130, thereby reducing the required capacity of the generator 150.

In addition, the controller 120 is able to ship to the arriving from the time (t ₁₁₎ leaving the harbor for a predetermined time before the time (t ₁₂₎ to control the charging or discharging of ESS (130) improves the power efficiency. 5, when the amount of the generated power V _P produced by the generator 150 during the voyage is greater than the amount of supplied power V _L supplied to the power equipment 160 (a 1, a 2) is determined by the time provide a charging signal to the ESS (130), and provides a discharge signal to produce electric power (V _P) the amount of the supply power amount (V _L) less the case (b1) ESS (130) is determined by the second time point than can do. Therefore, since the generator 150 generates only the average power required for the operation of the ship, the power generation efficiency of the generator 150 can be improved.

The controller 120 is the first point in time if less than the thruster 164, the movable amount of power required for the amount of charge, ESS (130) at the time before entering the AMP present Port (t ₁₂₎ to operate the thruster 164 And provides a charge signal to the ESS 130. If the charged amount of the ESS 130 is greater than the amount of the movable power, the second time point is determined to provide a discharge signal to the ESS 130. At this time,, ESS (130) at the beginning (t ₁₃₎ of the eyepiece operation for the AMP present Port may keep the thruster operating power. Thereafter, at the time when the ship docks to the port, the ESS 130 can supply and charge electric power from the AMP.

Referring to FIG. 7, the power load and the battery charge amount can be known when the ship departs and enters the non-AMP port where the AMP does not exist.

At this time, the ship departs from the state in which the battery charge amount of the ESS 130 is 100%, and stays at the AMP non-existent port after the sailing.

The controller 120 determines the departure time t ₄₀ as the second time point and provides a discharge signal to the ESS 130. At this time, the thruster 164 can be driven through the electric power generated by the generator 150 and the electric power discharged from the ESS 130.

In addition, the controller 120 can improve the power efficiency by controlling the charging or discharging of the ESS 130 during a time point t ₄₂ before the ship departs from the port and starts to voyage t ₄₁ .

The controller 120 may determine the first time point (t ₄₂ ) before entering the AMP non-existent port and provide a charging signal to the ESS 130. At this time, the ESS 130 may be fully charged (e.g., 100%) at the beginning of the riding operation at the AMP non-existent port (t ₄₃ ). Thereby, the ESS 130 provides a necessary load to the thruster 164 in the AMP non-existent port, and a predetermined amount of charge remains. Thus, power can be supplied to the in-ship power facility 160 without driving the generator 150 within the AMP non-existent port.

Referring to FIG. 8, the power load and the battery charge amount can be known when the ship in voyage passes the ECA region. The ECA zone is defined in Annex VI of MARPOL and is intended to prevent, reduce and control emissions of nitrogen compounds (NOx), sulfur oxides (SOx) and / or particulate matter (PM) it means.

Controller 120 may determined the previous time point (t ₂₁₎ the ship is entering the ECA region in the first point, provides a charging signal to the ESS (130). At this time, the ESS 130 may be fully charged (for example, 100%) at the time t ₂₂ when the ship enters the ECA region. In addition, the controller 120 may determine the time (t ₂₂ -t ₂₃ ) at which the position of the ship included in the real-time position information is within the ECA region as the second time point and provide a discharge signal to the ESS 130 . Accordingly, power required for the in-ship power facility 160 can be secured in the ECA area without operating the generator 150 consuming the fuel containing sulfur compounds.

After that, the controller 120 determines the time (t ₂₃ -t ₂₄ ) at which the ship departs from the ECA zone as the first time point and provides a charge signal to the ESS 130 so that the ESS 130 obtains the basic power .

Referring to FIG. 9, when the area near the port from which the ship departs and ships is an ECA area, the power load and the battery charge amount required for the ship can be known. In this case, the port where the port is departing and entering port is provided with the AMP.

The controller 120 determines the departure time t ₃₀ as the second time point and provides the discharge signal to the ESS 130. At this time, the thruster 164 can be driven through the electric power generated by the generator 150 and the electric power discharged from the ESS 130.

However, since the neighborhood of the port departing ECA region, the controller 120 provides a discharge signal to the ESS (130) to the vessel is determined to leave the harbor outside the ECA region and the time (t ₃₂₎ in a second time .

In addition, between the vessel is the time that passes through the ECA region (t ₃₂₎ and entering the ECA region to arrival harbor vicinity (t ₃₃₎ the previous time, the controller 120 is based on the production of electric power and the supply power amount ESS (130 Can be controlled to improve power efficiency.

The controller 120 determines the previous time point (t ₃₃₎ to enter the ECA area existing in the vicinity of the harbor to arrival at the first point, it is possible to provide a charge signal to the ESS (130). At this time, ESS (130) is the vessel to be fully charged (e.g., 100%) at the time (t ₃₄₎ entering the ECA region.

In addition, the controller 120 determines the time point (t ₃₄ -t ₃₅₎ to the vessel enters the ECA region anchored in the harbor in a second point in time it is possible to provide a discharge signal to the ESS (130). Thus, the power required for the onboard power facility 160 can be supplied in the ECA region without operating the generator 150 consuming the fuel containing sulfur compounds.

Therefore, the ship according to the embodiment of the present invention can improve the power efficiency by comparing the operation information of the generator 150 and the charge / discharge of the ESS 130 by comparing the lane information and the real time location information.

10 is a block diagram of an ESS control system in accordance with an embodiment of the present invention.

Referring to FIG. 10, an ESS control system according to an embodiment of the present invention includes a navigation system 220, a measurement system 210, a receiver 230, a controller 240, an ESS 250, and a PMS 260 But does not exclude additional configurations.

Hereinafter, the detailed configuration not described in the ESS control system according to an embodiment of the present invention may be the same as the detailed configuration of the ship according to the embodiment of the present invention.

The measurement system 210 measures the real-time location information of the ship. At this time, the measurement system 210 includes a GPS which is located inside the ship and measures the position of the ship from the satellite, but includes various measurement means capable of measuring real-time position information of the ship.

The navigation system 220 is a system for storing navigation information of a ship, and may be located inside the ship or at a port. Here, the lane information may include vessel entry and departure information, flight information, Emission Control Areas (ECA) information, and port information provided with the AMP (Alternative Maritime Power).

The receiver 230 receives the real-time location information from the measurement system 210 and receives the navigation information from the navigation system 220 and provides it to the controller 240.

The controller 240 may provide a charge signal or a discharge signal to the ESS 250 based on the lane information and the real time location information. Specifically, the controller 240 compares the lane departure information with the real time location information to determine whether it is a first time point or a second time point, provides a charge signal to the ESS 250 at the first time point, It is possible to provide a discharge signal to the ESS 250. [ Thus, it is possible to increase the lifetime of the ESS 250 and improve the power efficiency, thereby saving the fuel consumed in the operation.

The PMS 260 provides a first signal for increasing the operating rate to the generator at the first time point and a second signal for lowering the operating rate at the second time point. Therefore, it is possible to increase the amount of power supplied to the ESS 250 at the first time and to reduce the amount of power supplied to the ESS 250 at the second time.

Therefore, the ESS control system according to an embodiment of the present invention can improve the power efficiency by comparing the operation information of the generator 250 and the charge / discharge of the ESS 250 by comparing the lane information and the real time location information.

11 is a flowchart of an ESS control method according to an embodiment of the present invention.

Referring to FIG. 11, an ESS control method according to an embodiment of the present invention includes a first receiving step (S310) for receiving ship information, a second receiving step (S320) for receiving real- (S330) of providing a charge signal or a discharge signal to the ESS based on the lane information and the real-time location information, and providing a first signal or a second signal to the generator (S340) .

The control step S330 may include a determining step of comparing the navigation information with the real-time position information to determine whether it is a first point in time or a second point in time, and a step of providing a charging signal to the ESS in the first point of time, And providing a discharge signal to the ESS. In this case, the step of providing the first signal or the second signal to the generator (S340) may include the steps of: providing a first signal for increasing the operating rate to the generator at the first time point; 2 < / RTI > signal.

The ESS control method according to an embodiment of the present invention may be implemented by a ship according to an embodiment of the present invention or an ESS control system according to an embodiment of the present invention.

Therefore, according to the ESS control method according to the embodiment of the present invention, the charging / discharging efficiency of the ESS can be optimally controlled by comparing the liner information of the ship with the real-time position information in real time to improve the power efficiency and prolong the life of the battery .

12 is a view showing a container line according to an embodiment of the present invention.

Referring to FIG. 12, a vessel and an ESS control system according to an embodiment of the present invention can be applied to the container line 1000. Specifically, a thruster 1006 located at the bow, an ESS 1004 located near the center of the hull, a generator 1002 and a propeller 1008 located at the stern are connected to a ship and an ESS control The configurations of the system can be applied. Alternatively, a configuration such as the ESS 1002 may be placed on a container located on a deck.

13 is a view showing an LNG line according to an embodiment of the present invention.

Referring to FIG. 13, a ship and an ESS control system according to an embodiment of the present invention can be applied to the LNG line 2000. Specifically, the thruster (2006) located at the bow, the ESS (2004) located near the center of the hull, the generator (2002) and the propeller (2008) The configurations of the system can be applied. The power generated by the generator 2002 and the power discharged from the ESS 2004 may be supplied to a load such as a temperature regulator for regulating the temperature of the LNG tank or a compressor for re-liquefying the BOG vaporized in the LNG tank .

Accordingly, the ship, the ESS control system, and the ESS control method according to an embodiment of the present invention can be applied to various ships such as the above-described container line 1000 and the LNG line 2000, Can be applied. 12 and 13 are merely examples in which the ship, the ESS control system, and the ESS control method according to the embodiment of the present invention can be applied to various ships, and the arrangement of the specific configuration of the ship and the ESS control system is various Design can be changed.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, You will understand. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

110: receiver
120: controller
130: ESS
140: PMS
210: Measurement system
220: Navigation system
230: controller
230: receiver
240: controller
250: ESS
260: PMS

Claims (16)

An ESS (Energy Storage System) that is charged with the production electric power of the generator and discharges the charged electric power to supply to the electric power facility;
A receiver for receiving ship's navigation information and real-time location information; And
And a controller for providing a charge signal or a discharge signal to the ESS based on the lane information and the real time location information. The method according to claim 1,
The ESS,
A battery, and a converter connected to the battery and the generator to convert the produced power into direct current power and convert the charged power into alternating current power. The method according to claim 1,
The navigation information includes:
A ship including at least one of input / output information of a ship, flight information of a ship, information of Emission Control Areas (ECA), and information of ship's AMP (Alternative Maritime Power). The method according to claim 1,
The controller comprising:
The ESS is compared with the real-time position information to determine whether it is a first point of time or a second point of time. In the case of the first point of time, a charge signal is provided to the ESS, and in the case of the second point of time, Ship. 5. The method of claim 4,
The controller comprising:
When the generated power amount of the generator during the voyage is greater than the supplied power amount supplied to the power equipment,
And determines that the second point in time when the amount of electricity produced by the generator is less than the amount of electric power supplied. 5. The method of claim 4,
The controller comprising:
And determines that the time point at which the position of the ship included in the real-time position information is within the emission control area (ECA) region is the second time point. 5. The method of claim 4,
The controller comprising:
A ship determined to be at the first point in time before entering the Emission Control Areas (ECA) zone. 8. The method of claim 7,
Wherein the ESS is fully charged when entering the emission control area. 5. The method of claim 4,
The controller comprising:
And determines the point of time before entering the AMP non-existent port as the first point in time. 10. The method of claim 9,
At the beginning of the bidding operation for the AMP non-existing port, the ESS is fully charged. 5. The method of claim 4,
The controller comprising:
When it is determined that the charged amount of the ESS is less than the thruster operating power amount at the time before entering the AMP presence port, the first point of time is determined to be the second point in time when the charged amount of the ESS is greater than the thruster operating power amount Ship. 12. The method of claim 11,
Wherein the ESS maintains the thruster operational power at the start of the riding operation for the AMP presence port. 5. The method of claim 4,
Further comprising a power management system (PMS) for providing a first signal for increasing the operating rate to the generator in the first time, and a second signal for lowering the utilization rate in the generator in the second time. A first receiving step of receiving the lane departure information of the ship;
A second receiving step of receiving real-time position information of the ship; And
And providing a charge signal or a discharge signal to the ESS based on the lane information and the real-time location information. 15. The method of claim 14,
Wherein the control step comprises:
Comparing the navigation information with the real-time location information to determine whether the navigation information is a first viewpoint or a second viewpoint;
Providing a charge signal to the ESS when the first time point is provided and providing a discharge signal to the ESS if the second time point is present. 16. The method of claim 15,
Providing a first signal for increasing the duty ratio to the generator at the first time point and providing a second signal for lowering the utilization rate to the generator at the second time point.

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