WO2019132493A1

WO2019132493A1 - Charging device including power module

Info

Publication number: WO2019132493A1
Application number: PCT/KR2018/016624
Authority: WO
Inventors: 김성두
Original assignee: 김성두
Priority date: 2017-12-26
Filing date: 2018-12-26
Publication date: 2019-07-04
Also published as: KR101915075B1

Abstract

A charging device of the present invention comprises a power module, which includes a power unit for supplying charging power to be directly inputted to an electric vehicle and a control unit for controlling the power unit, wherein the control unit can identify the difference between a contractual power value, having been set to be supplied to the electric vehicle, and a protection power value for protecting the electric vehicle, and the power unit reduces the charging power to the amount of surplus power generated by the difference between the contract power value and the protection power value so as to be capable of supplying the same to the electric vehicle.

Description

Charging device with power module

The present invention relates to a charging apparatus for charging an electric vehicle moving by electric power.

A battery is installed in an electric vehicle (EV) or a hybrid vehicle, and a battery management system (BMS) is installed as a battery control system.

As a part of the development of green technology, much research has been conducted on the charging system of the electric car in order to improve the utility of the electric car as well as the research on the electric car. However, until now, it is only in the development stage, so the charging system that meets various consumer needs as well as the technical problems to be solved is not spreading.

The present invention provides a charging device capable of managing surplus electric power generated in a process of protecting an electric car during charging of an electric car.

The charging device of the present invention includes a power module that supplies a charging power directly input to an electric vehicle and a power module that includes a controller that controls the power module, And the power unit may supply the electric power to the electric vehicle by lowering the charging power by a surplus electric power generated due to a difference between the contract power value and the protection electric power value.

The charging device of the present invention can directly manage surplus electric power instead of delegating the surplus electric power generated in the process of protecting the electric car during charging of the electric car to the electric car.

Since surplus power is directly managed by the charging device, surplus power itself may not be provided to the electric vehicle. As a result, the burden on the electric vehicle that needs to deal with unnecessary surplus electric power is alleviated, and the electric vehicle can be prevented from being damaged by the surplus electric power.

The charging device of the present invention can lower the power value of the charging power so that no surplus power is generated at all. As a result, unnecessary power dissipation can be prevented.

Alternatively, according to the charging apparatus of the present invention, there is a margin for turning unnecessary generated surplus power to another node, so that the charging start time of another electric vehicle waiting for the next charging can be advanced by using surplus electric power.

The charging device of the present invention can compensate for the damage of the user due to the surplus electric power caused in the protection of the electric car.

The charging device of the present invention may include a power module and a separate kiosk. The number of kiosks for the power module can be freely expanded through a plurality of connection terminals provided in the power module.

In addition, unlike a kiosk exposed to the outside, a power module can be disposed in a room shielded from sunlight or the like or equipped with an air conditioning facility, so that a malfunction of the power module due to a rise in temperature or the like can be reduced.

The kiosk facing the electric car can perform only the function of supplying the electric power provided from the power module to the electric vehicle without performing the electric power function to convert electric power at all. Accordingly, since the kiosk is formed in a very simple configuration, there is an advantage that it is very easy to add / delete the kiosk to / from the power module.

According to the present invention, a kiosk that is simple and has various additional functions can be provided since no electric power is required for the kiosk. For example, according to the present invention, an all-in-one kiosk provided with a plurality of kinds of outlets can be provided.

Since the charging device of the present invention includes the ESS module in which the reserve power is stored, it is possible to normally charge the electric vehicle even when an abnormality occurs in the commercial power supply.

1 is a schematic view showing a charging apparatus of the present invention.

2 is a graph showing an operation mode of the power unit.

3 is a schematic view showing a receptacle portion of a kiosk;

4 is a schematic view showing a power portion.

1 is a schematic view showing a charging apparatus of the present invention.

The charging device shown in FIG. 1 may include a power module 110, a kiosk 130, and an ESS module 210.

The power module 110 can supply the charging power directly input to the electric vehicle 90. [ For example, the power module 110 may convert the AC power corresponding to the commercial power provided from the external power source of the power supplier into the charging power directly input to the electric vehicle 90. The electric vehicle 90 may include a hybrid vehicle that moves the vehicle using an electric vehicle, which is purely a motor only, and an engine and a motor.

The kiosk 130 may be separate from the power module 110. The kiosk 130 may be provided with a power line 180 connected to the power module 110 and a vehicle line 190 connected to the electric vehicle 90. [ The power line 180 and the vehicle line 190 may comprise cables provided with conductive leads surrounded by an insulator.

Since the kiosk 130 is disposed at a position facing the vehicle, the kiosk 130 can be installed outdoors in sunlight.

On the other hand, the power module 110, which is detachable from the kiosk 130, may be disposed in a room isolated from the outside. It is easy to install an air conditioning system that cools the power module 110 through a limited space in the room. As a result, since the efficiency reduction of the power module 110 due to the temperature rise is prevented, the power consumption of the power module 110 can also be reduced. In addition, a safety accident of the user due to access by the user can be prevented.

The power line 180 allows the kiosk 130 to be electrically connected to the power module 110. The kiosk 130 can be electrically connected to the electric vehicle 90 by the vehicle line 190. [ As a result, the power module 110 and the electric vehicle 90 can be electrically connected by the power line 180 and the vehicle line 190.

The kiosks 130 may be connected to one power module 110 in a plurality of ways.

The kiosk 130 may receive charging power from the power module 110 through the power line 180 and may deliver the charging power to the electric vehicle 90 through the vehicle line 190.

The power module 110 may be provided with a plurality of connection terminals 115 to which the power line 180 is detachably connected.

The number of kiosks 130 connected to the power module 110 through the plurality of connection terminals 115 can be increased.

The power module 110 may include a power unit 111 for supplying charging power directly input to the electric vehicle 90 and a control unit 113 for controlling the power unit 111. [

For example, the power unit 111 can convert the commercial AC power obtained through the commercial line 170 into the charging power required by the electric vehicle 90.

The control unit 113 can grasp the difference between the contract power value set to be supplied to the electric car 90 and the protection electric power value for protecting the electric vehicle 90. [

The power unit 111 can supply the electric power to the electric vehicle 90 with the charge power reduced by the surplus electric power k generated due to the difference between the contract power value and the protection electric power value.

The electric power unit 111 can charge the electric vehicle 90 in one of a plurality of charging modes.

When the electric vehicle 90 is parked at a position facing the kiosk 130 and the vehicle line 190 of the kiosk 130 is connected to the electric vehicle 90, You can choose. When the charging mode is selected by the user, the power unit 111 can operate in accordance with the selected charging mode.

For example, the power unit 111 may operate in one of a rapid mode, a medium speed mode, and a slow mode according to a user's selection.

The power unit 111 can basically supply the charging power according to the contracted power value of the operation mode selected by the user.

The contract power value of the medium speed mode is higher than the contract power value of the smooth mode and the contract power value of the rapid mode may be higher than the contract power value of the medium speed mode.

2 is a graph showing an operation mode of the power unit 111. As shown in FIG.

A contract power value matched to the charging mode can be set.

For example, the rapid mode may be a charging mode in which the electric vehicle 90 is charged at 50 kW. At this time, the contracted power value of the rapid mode may be 50 kW set in the rapid mode.

The medium speed mode may be a charging mode in which the electric vehicle 90 is charged at 30 kW. At this time, 30 kW set in the medium speed mode may be the contract power value in the medium speed mode.

The slow mode may be a charging mode in which the electric vehicle 90 is charged at 7 to 20 kW. At this time, 7 to 20 kW set in the slow mode may be the contract power value of the slow mode.

If the user desires the rapid mode, it is the same as if he wants to charge the electric car 90 with a contract power value of 50 kW. Accordingly, the power unit 111 can charge the battery of the electric vehicle 90 at 50 kW corresponding to the contracted power value of the rapid mode.

The electric car 90 being charged in the rapid mode is likely to be continuously charged with the contracted power value of 50 kW up to the charge amount set by the user, for example, 100% charge amount, but the reality is different.

The electric vehicle 90 may be provided with a battery management system (BMS) for protecting and managing the battery.

The BMS can lower the power input to the battery of the electric vehicle 90 to a predetermined protection power value when the charged amount of the battery satisfies the preset value, in order to prevent the temperature of the battery from increasing, deteriorating, and preventing explosion.

There are two methods for lowering the electric power input to the battery of the electric vehicle 90 to the protection electric power value.

First, the charging power of the contracted power value is input directly from the power module 110, and the BMS can lower the power value of the charging power to the protection power value. In this case, the surplus power k generated due to the difference between the contract power value and the protection power value may be wasted. Also, when the BMS malfunctions, the charging power of the contracted power value can be directly applied to the battery, and there is a risk of battery damage.

Next, the power module 110 can provide the charging power lowered to the protection power value in accordance with the state of the battery. According to the charging apparatus of the present invention, the charging power at the power module 110 itself is lowered to the protection power value, and the charging power of the protection power value can be provided to the electric car 90. [

The control unit 113 can communicate with the electric vehicle 90 to grasp the protection power value or to determine the protection point at which the protection power value is required.

A vehicle signal line connecting the electric vehicle 90 and the kiosk 130 and a power signal line connecting the kiosk 130 and the power module 110 may be provided.

At this time, the vehicle signal line may be installed in the vehicle line 190 or may be formed integrally with the vehicle line 190. The power signal line may be installed in the power line 180 or may be integrally formed in the power line 180. When the vehicle signal line and the power signal line are formed integrally with the vehicle line 190 and the power line 180, respectively, a power line communication network can be used.

The control unit 113 can communicate with the electric vehicle 90 through the vehicle signal line and the electric power signal line.

The control unit 113 can acquire the battery-related information of the electric vehicle 90 through the communication with the electric vehicle 90, specifically, the BMS. The control unit 113 can grasp the protection time and the protection power value of the electric vehicle 90 through analysis of the battery-related information.

The power unit 111 can adjust the charging power to one of the contracted power value and the protection power value according to the battery related information.

The power unit 111 can basically set the charging power to the contract power value. The power unit 111 can lower the charging power to the protection power value when the charged amount of the battery satisfies the set value.

For example, the power unit 111 can supply the charging electric power of the contract power value to the electric vehicle 90. [ When the protection time is recognized by the control unit 113, the power unit 111 can reduce the charging power to the protection power value in accordance with the protection time. At this time, the power unit 111 may lower the charging power of the contracted power value to the protection power value, for example, by adjusting the current value.

For example, in the case of rapid charging in the graph of FIG. 2 having the current value A in the vertical axis, the power unit 111 can supply 120 A of current to the electric vehicle 90 to satisfy the contracted power value.

When the charged amount of the battery which has been rapidly charged satisfies the set value of 73%, the control unit 113, which grasps the fact through communication with the electric vehicle 90, calculates the charging electric power To the electric vehicle (90).

According to the present embodiment, since the surplus power k corresponding to the difference between the contract power value and the protection power value is not provided to the electric car 90, the burden on the electric vehicle 90 that processes the surplus electric power k is reduced and the surplus electric power k The damage of the battery due to the supply of the battery can be prevented.

Since the surplus electric power k itself is not produced in the position of the electric power module 110, unnecessary commercial electric power is not used. Further, the surplus electric power k can be supplied to another electric car 90 waiting for charging as required.

For example, the power module 110 may be connected to a plurality of nodes using charge power. At this time, the node may include another kiosk 130 electrically connected to power module 110, other electrical consumer products, and the like.

The control unit 113 can grasp a specific node requiring a surplus power k among a plurality of nodes.

If there is a specific node that requires the residue power k, the power section 111 can generate a power greater than the protection power value. For example, the power unit 111 can generate the power satisfying the contracted power value as it is, even if the power unit 111 goes into the protection mode that provides the charging power of the protection contract value to the charging vehicle.

The power section 111 can supply part of the generated power to the electric car 90 as charging power and supply the remaining power to the specific node as the surplus power.

For example, the power unit 111, which is supplying 120A to the specific electric vehicle 90 according to the contract power value, can reduce 120A to 60A according to the demand of the specific electric vehicle 90. [ At this time, the remaining 60A related to the surplus power among 120A may not be produced. If there are other nodes requiring redundant power, the power unit 111 may supply at least some of the remaining 60A associated with the surplus power to another node.

On the other hand, the charging amount of the battery from the initial charging time of the electric vehicle 90 may be a state in which the set value is satisfied. In this case, since the charging start time and the battery protection time coincide with each other, the charging power of the protection power value can be supplied to the electric car 90 from the beginning of charging.

At this time, the user who requests the rapid mode is in a state of charging the battery at a low speed despite paying a high cost. In this case, the control unit 113 may generate a notification signal indicating that the vehicle is to be charged with the protection power value, and may transmit the notification signal to the kiosk 130. The user who has confirmed the notification signal through the kiosk 130 can change the charging mode to the middle-speed mode or the slow-speed mode.

As shown in FIG. 2, there is a problem that the difference between the charging time of the rapid mode and the charging time of the middle-speed mode is reduced due to the protection power value for battery protection.

For example, when the battery is charged from 40% to 95%, the charge time of the electric vehicle 90 is 30 minutes and 19 seconds in the rapid mode in which 120A is supplied. In the case of the medium speed mode in which 60A is supplied, This charge time is 33 minutes and 48 seconds. In this case, it is inevitable that the loss of the user who has selected the rapid mode at an expense of cost is increased.

When the charging power including the surplus power is continuously supplied to the electric vehicle 90 despite the elapse of the protection time, the commercial power consumed in the power module 110 corresponds to the contracted power value, There is no way to do it.

However, according to the present invention, the power module 110 does not consume the commercial power as much as the redundant power, or provides the redundant power to the other node, thereby generating a profit on the power module 110 side.

When the surplus power is generated, the control unit 113 can reduce the cost due to the surplus power among the charging charges paid by the user.

According to the present invention, since the power unit 111 is provided in the power module 110, the power unit 111 does not need to be provided in the kiosk 130. As a result, the space utilization as much as the power unit 111 is generated, so that the kiosk 130 can be lightened or the appearance design can be improved. In addition, various additional functions can be provided to the kiosk 130.

For example, the receptacle 150 may be provided on the kiosk 130 to receive the plug unit.

At one end of the vehicle line 190, a charging gun 191 connected to the charging end of the electric vehicle 90 may be formed. A plug portion to be detached from the receptacle 150 of the kiosk 130 may be provided at the other end of the vehicle line 190.

The vehicle line 190 may be replaceable with respect to the kiosk 130 by the plug portion. As a result, there is an advantage that the vehicle line 190 can be adaptively changed depending on the type of vehicle.

3 is a schematic view showing the receptacle 150 of the kiosk 130. Fig.

The receptacle 150 may be provided with a signal outlet, a commercial power outlet 151, an outlet 153 for a slow charging charger, and a DC power outlet 155.

The commercial power outlet 151 corresponds to the plug-in hybrid vehicle, and 220V commercial power can be output.

The outlet 153 for the slow charger is designed to correspond to the 7 kW slow charger and can output 7 kW alternating current. The 7 kW AC power is input to the electric vehicle 90 and can be converted to DC power in the electric vehicle 90.

The DC power outlet 155 outputs DC power, and the charging power of the contract power value set in accordance with the rapid mode, the medium speed mode, and the continuous mode can be output. The signal outlet is installed together with the DC power outlet 155 and can be electrically connected to the vehicle signal line.

The control unit 113 is electrically connected to the signal outlet, and can communicate with the electric vehicle 90 through the signal outlet.

The power section 111 can supply the commercial AC power to the commercial power outlet 151. [ The power section 111 can supply AC power for the slow charging device to the socket 153 for the slow charging device. The power section 111 may provide DC charging power to the DC power outlet 155.

The receptacle 150 may be provided with an indicator light 159 indicating the current state of the receptacle 150 through the color.

The indicator lamp 159 may be turned off in the absence of the electric vehicle 90 connected to the receptacle 150. [

The indicator 159 may be displayed in a different color depending on the type of the receptacle electrically connected to the electric vehicle 90. [ While the electric vehicle 90 is electrically connected to the DC power outlet 155, the indicator lamp 159 may be displayed in a different color depending on the charging mode.

The DC power outlet 155 may be covered by the normally-charged gun 191. On the other hand, the commercial power outlet 151 and the outlet 153 for the slow charging charger can be exposed to the outside. To prevent a safety accident, the receptacle 150 may be provided with a cover 157 for covering the commercial power outlet 151 and the socket 153 for the slow charging charger. The cover 157 may be hinged to be rotatable relative to the kiosk 130.

4 is a schematic diagram showing the power section 111. Fig.

An ESS (Energy Storage System) module is coupled to the power module 110 and may store the reserve power provided to the electric vehicle 90.

The reserve power may be converted to charging power by the power module 110 and then provided to the electric car 90 through the kiosk 130.

The power unit 111 may include a first conversion unit 117 that converts AC power input from the outside into primary DC power and a second conversion unit 118 that converts primary DC power into charging power .

As an example, the first conversion section 117 may include an AD / DC converter. The primary DC power output from the first converter 117 may have the magnitude of the first voltage.

The second conversion unit 118 may include a DC / DC converter. The first voltage of the primary DC power may be different from the second voltage required by the electric vehicle 90. [ The primary DC power can be converted into the charging power corresponding to the secondary DC power having the magnitude of the second voltage by the second converter 118. [

The ESS module 210 may store the primary DC power.

The ESS module 210 may provide the first DC power stored in advance to the second converter 118 under the control of the controller 113. [

For example, the control unit 113 can charge the battery (not shown) provided in the ESS module 210 using the AC commercial power at a time when the electricity bill is low. Then, the electric vehicle 90 can be charged with the spare electric power stored in the ESS module 210 in a time period in which electricity charges are high, that is, a so-called peak time. The control unit 113 may control the charging module or the ESS module 210 so that the electric vehicle 90 is charged with the standby power instead of the commercial power at the peak time. According to this, the burden on the electric power supplier can be reduced, and the burden of electric charges of the charging device provider can be alleviated.

Meanwhile, the ESS module 210 may store power other than the primary DC power.

For example, the charging device of the present invention may include an energy module 230 for producing renewable energy. New and renewable energy can include electric energy produced by solar, wind, hydro, and so on.

The energy module 230 includes a solar panel that generates new and renewable energy using solar light, a wind turbine that generates new and renewable energy using wind turbine, a hydro generator that generates new and renewable energy using hydro turbine, and the like . &Lt; / RTI >

The ESS module 210 may store renewable energy produced from the energy module as reserve power. The voltage value or the current value of the renewable energy stored in the ESS module 210 may be different from that required by the electric car 90. [ The ESS module 210 can provide the previously stored new and renewable energy to the second conversion unit 118 under the control of the control unit 113 so that the previously stored new and renewable energy can be normally supplied to the electric vehicle 90. [

The ESS module 210 can reduce the amount of power supplied to the second conversion unit 118 by the amount of power corresponding to the surplus power in order to reduce the surplus power when the surplus power is generated.

The control unit 113 may control the power unit 111 or the ESS module 210. [ The control unit 113 can selectively provide the AC electric power or the reserve electric power to the electric vehicle 90. [

A plurality of kiosks 130 assigned to each set number of electric cars 90 may be connected to the power module 110 to simultaneously charge the plurality of electric cars 90. [ When there are a plurality of kiosks 130 to provide charging power, there is a possibility that the available charging power is insufficient. In addition, it is necessary to establish a policy to supply the electric power of the ESS module 210 to the electric car 90. [

The control unit 113 may appropriately control the power module 110 and the ESS module 210 so that the power, the module, the plurality of kiosks 130, and the ESS module 210 are normally operated according to the business policy.

For example, the control unit 113 may control the power module 110 to be one of a first power mode, a second power mode, and a third power mode.

The first power mode may be a control mode that provides the AC power supplied from the power supplier only to the electric vehicle 90. [ The power unit 111 can convert the entire input commercial AC power into the charging power and provide it to the electric vehicle 90.

The second power mode may be a control mode that provides AC power to the electric vehicle 90 and the ESS module 210 together.

And the third power mode may be a control mode for interrupting the AC power input to the power module 110. [

The controller 113 may control the ESS module 210 to one of a first ESS mode and a second ESS mode.

The first ESS mode may be a control mode that provides reserve electric power to the electric car 90. [

The second ESS mode may be a control mode for interrupting the supply of the reserve electric power to the electric vehicle 90. [

The controller 113 may apply the first ESS mode only in the first power mode or the third power mode so that the power module 110 and the ESS module 210 operate normally.

For example, the control unit 113 may apply the third power mode and the first ESS mode when the total charge power required by the plurality of kiosks 130 is less than the preset allowable value. In this case, alternating-current power is not provided to the electric vehicle 90, and only spare electric power stored in the ESS module 210 can be provided to the electric vehicle 90. [

The controller 113 may apply the first power mode and the first ESS mode together when the total charge power required by the plurality of kiosks 130 is equal to or greater than the allowable value. If the total charging power is more than the allowable value, the total charging power can not be satisfied only by the AC power, or the total charging power can be satisfied only by the reserve power. At this time, if the first power mode and the first ESS mode are applied together, both the AC power and the reserve power can be used for charging the electric vehicle 90. Therefore, the total charging power exceeding the allowable value can be satisfied, and a plurality of electric cars 90 connected to the plurality of kiosks 130 can be charged at the same time.

Claims

A power module for supplying a charging power directly inputted to an electric vehicle, and a control module for controlling the power module,

The control unit recognizes a difference between a contract power value set to be supplied to the electric vehicle and a protection electric power value for protecting the electric vehicle,

Wherein the power unit lowers the charging power by a surplus power generated due to a difference between the contract power value and the protection power value and supplies the charging power to the electric vehicle.
The method according to claim 1,

Wherein the power unit operates in one of a rapid mode, a medium speed mode, and a slow mode according to a user's selection,

The power unit basically supplies the charging power according to the contracted power value of the operation mode selected by the user,

The contract power value of the medium speed mode is higher than the contract power value of the full speed mode,

Wherein the contract power value of the rapid mode is higher than the contract power value of the medium speed mode.
The method according to claim 1,

A plurality of nodes using the charging power are connected to the power module,

Wherein the control unit recognizes a specific node requiring the surplus power among the plurality of nodes,

If there is the specific node requiring the surplus power, the power section generates a power greater than the upper protection power value,

Wherein the power unit supplies, as the charging power, a part of the generated electric power to the electric vehicle, and supplies the remainder to the specific node as the surplus electric power.
The method according to claim 1,

Wherein the control unit communicates with the electric vehicle to acquire battery-related information of the electric vehicle,

Wherein the power unit adjusts the charging power to one of the contract power value and the protection power value according to the battery related information.
5. The method of claim 4,

The power unit basically sets the charging power to the contracted power value,

Wherein the power unit lowers the charging power by the protection power value when the charged amount of the battery satisfies a set value.
The method according to claim 1,

And a kiosk separated from the power module and having a power line connected to the power module and a vehicle line connected to the electric car,

Wherein the kiosk receives the charging power from the power module via the power line and delivers the charging power to the electric vehicle through the vehicle line.
The method according to claim 6,

Wherein the power module is provided with a plurality of connection terminals to which the power line is detachably connected,

Wherein the number of the kiosks connected to the power module through the plurality of connection terminals is expandable.
The method according to claim 6,

A vehicle signal line connecting the electric vehicle and the kiosk, and a power signal line connecting the kiosk and the power module,

Wherein the control unit communicates with the electric vehicle through the vehicle signal line and the electric power signal line,

The control unit recognizes the protection time of the electric vehicle and the protection electric power value through communication with the electric vehicle,

Wherein the power unit lowers the charge power to the protection power value in accordance with the protection time.
The method according to claim 6,

A charging gun connected to a charging end of the electric vehicle is formed at one end of the vehicle line, and a plug portion is provided at the other end of the vehicle line to be detached from the kiosk,

The kiosk is provided with a receptacle portion in which the plug portion is detached,

Wherein the vehicle line is replaceable with respect to the kiosk by the plug portion.
10. The method of claim 9,

The receptacle portion is provided with a signal receptacle, a commercial power receptacle, a socket for a slow charger, and a DC power receptacle,

Wherein the control unit is electrically connected to the signal outlet, communicates with the electric vehicle through the signal outlet,

Wherein the power section supplies commercial power to the commercial power outlet, supplies power for the slow charger to the outlet for the slow charger, and provides the charging power to the DC power outlet.
The method according to claim 1,

And an Energy Storage System (ESS) module connected to the power module and storing a backup power provided to the electric vehicle,

The standby power is converted into the charging power by the power module and provided to the electric vehicle,

Wherein the power unit includes a first conversion unit that converts AC power input from the outside into primary DC power and a second conversion unit that converts the primary DC power into the charging power,

The primary DC power is stored in the ESS module,

The ESS module provides the pre-stored first DC power to the second conversion unit under the control of the control unit,

Wherein the ESS module reduces an amount of power provided to the second conversion unit by an amount of power corresponding to the surplus power in order to reduce the surplus power when the surplus power is generated.