JP6378570B2 - Power control device, power conditioner, power storage device, and power control method - Google Patents

Description

  The present invention relates to a power control device, a power conditioner, a power storage device, and a power control method.

  In recent years, a power system in which a photovoltaic power generation system and a power storage device are connected to a grid is becoming widespread. In such a power system, when the system fails, a self-sustained operation can be performed, and the power storage device can be charged using the self-sustained operation output of the solar power generation system.

  In this case, the power storage device draws constant charging power from the solar power generation system regardless of the power generation amount of the solar power generation system. However, there is a problem that the photovoltaic power generation system stops due to overload when the generated power of the photovoltaic power generation system is insufficient and the generated power of the photovoltaic power generation system falls below the charging power drawn by the power storage device. there were.

  As described above, when the solar power generation system becomes overloaded, the solar power generation system stops for its own protection. However, once the solar power generation system stops, it returns after a predetermined time has elapsed for safety. For this reason, the power generated by the solar power generation system before returning is wasted. In addition, when other load equipment is connected to the self-sustained operation output terminal that outputs during the self-sustained operation of the photovoltaic power generation system, power is not supplied to other load equipment until it returns. It was.

  In order to cope with the above problem, an invention has been proposed in which the voltage of the AC power output from the photovoltaic power generation system is detected and control is performed so as to reduce the charging power drawn by the power storage device when the voltage drops (patent) Reference 1).

JP 2014-075854 A

  However, the invention described in Patent Document 1 is controlled so as to reduce the charging power drawn by the power storage device after the output of the solar power generation system actually decreases, so that the solar power generation system protects against overload. There is a problem that the margin for the time until the stop is started is small.

  An object of the present invention made in view of this point is to stop the photovoltaic power generation system due to overload when a power generation device such as a solar power generation system or a fuel cell system charges the power storage device using the self-sustained operation output. An object of the present invention is to provide a power control device, a power conditioner, a power storage device, and a power control method capable of controlling the power storage device with a time margin so as to prevent it.

A power control apparatus according to an embodiment of the present invention is a power control apparatus that controls a power storage device that is charged by an output of a power conditioner that converts DC power into AC power, and the DC / DC included in the power conditioner An acquisition unit that acquires a value of an intermediate link voltage that is a voltage between a converter and a DC / AC converter (inverter), and charging power that the power storage device draws from the power conditioner according to the value of the intermediate link voltage A control unit that controls, when the value of the intermediate link voltage is equal to or less than a first threshold, the control unit controls the power storage device to reduce the charging power, and in a predetermined period, the control unit When the value of the intermediate link voltage is equal to or lower than a second threshold value that is higher than the first threshold value, the power storage is performed so as to reduce the charging power. And it is characterized in controlling the location.

Moreover, the power conditioner which concerns on embodiment of this invention is equipped with the electric power control apparatus which controls the electrical storage apparatus charged with the output of the power conditioner which converts direct-current power into alternating current power. The power control device includes: an acquisition unit that acquires a value of an intermediate link voltage that is a voltage between a DC / DC converter and a DC / AC converter included in the power conditioner; and, depending on the value of the intermediate link voltage, And a control unit that controls charging power drawn from the power conditioner , wherein the control unit reduces the charging power when the value of the intermediate link voltage is equal to or lower than a first threshold value. The power storage device is controlled so as to reduce the charging power when the value of the intermediate link voltage is equal to or lower than a second threshold value that is higher than the first threshold value during a predetermined period. It is characterized by controlling .

In addition, the power storage device according to the embodiment of the present invention includes a power control device that controls the power storage device that is charged by the output of a power conditioner that converts DC power into AC power. The power control device includes: an acquisition unit that acquires a value of an intermediate link voltage that is a voltage between a DC / DC converter and a DC / AC converter included in the power conditioner; and, depending on the value of the intermediate link voltage, And a control unit that controls charging power drawn from the power conditioner , wherein the control unit reduces the charging power when the value of the intermediate link voltage is equal to or lower than a first threshold value. The power storage device is controlled so as to reduce the charging power when the value of the intermediate link voltage is equal to or lower than a second threshold value that is higher than the first threshold value during a predetermined period. It is characterized by controlling .

In addition, a power control method according to an embodiment of the present invention is a power control method for controlling a power storage device that is charged by an output of a power conditioner that converts direct current power into alternating current power, the DC included in the power conditioner. Obtaining a value of an intermediate link voltage, which is a voltage between a DC / DC converter and a DC / AC converter, and controlling charging power that the power storage device draws from the power conditioner according to the value of the intermediate link voltage and a step viewed including the step of the control, when the value of the intermediate link voltage is below the first threshold value, and controlling the power storage device so as to reduce the charging power, in a predetermined time period When the value of the intermediate link voltage is equal to or lower than a second threshold value that is higher than the first threshold value, the charging power is reduced. It is characterized in that comprising the step of controlling the electrical storage device so that.

  According to the power control device, the power conditioner, the power storage device, and the power control method according to the present invention, when the power generation device charges the power storage device using the self-sustained operation output, the power generation device is prevented from being stopped. The power storage device can be controlled with a sufficient margin.

1 is a diagram illustrating a schematic configuration of a power control system according to a first embodiment of the present invention. It is a figure which shows an example in the case of carrying out phase control of the electrical storage apparatus according to the value of an intermediate link voltage. It is a flowchart which shows an example of operation | movement of the electric power control system which concerns on 1st Embodiment of this invention. It is a figure which shows schematic structure of the power control system which concerns on 2nd Embodiment of this invention. It is a figure which shows schematic structure of the power control system which concerns on 3rd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a diagram showing a schematic configuration of a power control system 10 according to the first embodiment of the present invention. The power control system 10 includes a power conditioner 100, a power storage device 200, a power control device 300, a solar battery 400, and a load device 500. In FIG. 1, a solid line connecting each functional block indicates a power line, and a broken line indicates a communication line. The connection indicated by the communication line may be a wired connection or a wireless connection.

  FIG. 1 is a diagram for explaining an operation in a state where the system is in a power failure or intentionally disconnected and is operating independently. Therefore, in FIG. 1, the connection between the power conditioner 100 and the system and the connection between the power storage device 200 and the system are omitted.

  The power conditioner 100 converts the DC power generated by the solar battery 400 into AC power, supplies the AC power to the power storage device 200, and charges the storage battery 202. The power conditioner 100 includes a DC / DC converter 101, a DC / AC converter 102, and a detection unit 103.

  The DC / DC converter 101 boosts or steps down the voltage of the DC power supplied from the solar battery 400 and supplies it to the DC / AC converter 102.

  The DC / AC converter 102 is also referred to as an inverter, converts DC power into AC power, and supplies it to the power storage device 200. At the time of a power failure, the DC / AC converter 102 outputs AC power from the self-sustained operation output terminal, and supplies AC power to the power storage device 200 and the load device 500.

  In FIG. 1, an example in which the load device 500 is one is shown. However, this is an example, and the load device 500 may not be connected to the autonomous operation output terminal of the power conditioner 100. A plurality of load devices 500 may be connected.

  The detection unit 103 detects an intermediate link voltage that is a voltage between the DC / DC converter 101 and the DC / AC converter 102. Here, the “intermediate link voltage” is an output voltage of the DC / DC converter 101 and an input voltage to the DC / AC converter 102. Therefore, the intermediate link voltage is a DC voltage. In addition, the detection unit 103 transmits the detected value of the intermediate link voltage to the power control apparatus 300.

  The power storage device 200 includes a storage battery power conditioner 201 and a storage battery 202.

  The storage battery power conditioner 201 is connected to the self-sustained operation output terminal of the power conditioner 100 and draws charging power from the output of the DC / AC converter 102. The storage battery power conditioner 201 converts AC power supplied from the DC / AC converter 102 into DC power and supplies the DC power to the storage battery 202. The storage battery power conditioner 201 can control the amount of charging power drawn from the power conditioner 100 in a plurality of stages under the control of the power control device 300.

  The storage battery 202 is charged with DC power supplied from the storage battery power conditioner 201.

  The power control device 300 is connected to the power conditioner 100 and the power storage device 200 by, for example, a wired or wireless LAN (Local Area Network). The power control device 300 can communicate with the power conditioner 100 and the power storage device 200 using a predetermined communication protocol. For example, ECHONET Lite (registered trademark) can be used as the communication protocol. The power control apparatus 300 can acquire information on various devices through communication using ECHONET Lite, and can also control various devices. Note that ECHONET Lite is merely an example, and other communication protocols may be used. Moreover, you may use the apparatus provided with the function of the power control apparatus 300, and the function of the power conditioner 100. FIG. In this case, communication between the power control device 300 and the power conditioner 100 becomes unnecessary. Alternatively, a device having the function of power control device 300 and the function of power storage device 200 may be used. In this case, communication between power control device 300 and power storage device 200 is not necessary.

  The power control apparatus 300 includes an acquisition unit 301 and a control unit 302.

  The acquisition unit 301 acquires the value of the intermediate link voltage of the power conditioner 100 from the detection unit 103.

  The control unit 302 sends a command to the power storage device 200 to control the charging power drawn from the power conditioner 100 using a wired or wireless LAN according to the value of the intermediate link voltage acquired by the acquisition unit 301. In the present embodiment, since direct control of charging power is executed by the power storage device 200, the power control device 300 will be described as a control mode in which only a command is sent. A control form in which a control program capable of directly controlling the charging control of 200 is incorporated, and a signal for directly controlling the charging power may be transmitted.

  For example, when the value of the intermediate link voltage is equal to or less than a predetermined threshold (“first threshold” in the claims), the control unit 302 reduces the charging power that the power storage device 200 draws from the power conditioner 100. Control. For example, if the autonomous link output terminal outputs AC 100 [V] with single-phase two-wire, the value of the intermediate link voltage is 240 to 250 [V] in an ideal range, the first threshold value is 239. [V] may be used. Whether the intermediate link voltage value or the minimum voltage value in the allowable voltage range is set with emphasis on output stability (minimum voltage value is increased) or whether resistance to overload is important (minimum voltage) The design philosophy (low value) varies depending on the inverter. Therefore, when the first threshold value is set, it does not necessarily have to be equal to or lower than the lowest voltage value in the allowable voltage range. Specifically, in the above example, 239 [V] is used, but 241 [V] may be used.

  For example, the control unit 302 stores the power when the value of the intermediate link voltage is equal to or lower than a predetermined threshold (“second threshold” in the claims) in a predetermined period (for example, several milliseconds to 1 second). A command for reducing the charging power drawn from the power conditioner 100 is sent to the device 200. A voltage value higher than the first threshold value is set as the second threshold value. In other words, the second threshold value is set to a voltage value higher than the voltage value at which the output of the power conditioner 100 stops due to overload. Specifically, if the first threshold is 239 [V], the second threshold may be 241 [V].

  In this embodiment, when it is confirmed that the intermediate link voltage has dropped below the second threshold in a predetermined period, it can be predicted that a rapid voltage drop has occurred. As such a voltage drop, for example, a decrease in generated power of the photovoltaic power generation system due to bad weather can be cited as a cause. If it is determined that such a rapid voltage drop has occurred, the charging power drawn from the control unit 302 to the power storage device 200 is reduced even if the intermediate link voltage is equal to or higher than the first threshold value. Send a command. Thereby, due to the rapid voltage drop, it is possible to send a command to reduce the charging power drawn from the power conditioner 100 to the power storage device 200 before it becomes the first threshold value or less. As a result, the occurrence of a stop due to an overload of the power conditioner 100 due to a rapid voltage drop can be reduced.

  In the present embodiment, when the second threshold value is set to a voltage value close to the first threshold value, the time during which the intermediate link voltage decreases from the second threshold value to the first threshold value is shortened. The predetermined period may be set short. With this method, a decrease in the intermediate link voltage can be detected relatively early, so that a command can be quickly sent to the power storage device 200.

  In addition, the control unit 302 may not only prevent the power conditioner 100 from being stopped due to an overload, but may also control the power storage device 200 so that the power storage device 200 can be rapidly charged when the generated power of the solar cell 400 is sufficient. For example, when the value of the intermediate link voltage is equal to or higher than a predetermined value (“third threshold” in the claims), the control unit 302 determines that the generated power of the solar cell 400 has a margin, and the power storage device 200 May be controlled to increase the charging power drawn from the power conditioner 100. For example, when the value of the intermediate link voltage is 240 to 250 [V], 250 [V] is set as the third threshold value, and if the voltage value is higher than that, the power control device 300 causes the power storage device 200 to On the other hand, a permission signal for increasing the drawn charging power from 7 [kW] to 10 [kW] is transmitted. Since the power storage device 200 can increase the electric power that can be used for charging, the time for completing the charging of the storage battery 202 can be shortened from the normal time by changing the normal charging mode to the quick charging mode.

  Thus, according to the present embodiment, the control unit 302 of the power control device 300 controls the charging power that the power storage device 200 draws from the power conditioner 100 according to the value of the intermediate link voltage. For example, the controller 302 determines that the value of the intermediate link voltage is equal to or lower than a predetermined threshold (first threshold), or the value of the intermediate link voltage is equal to or lower than a predetermined threshold (second threshold) in a predetermined period. In some cases, power storage device 200 is controlled to reduce the charging power. Thereby, the power control device 300 stores the power storage device 200 with a temporal margin so as to prevent the power conditioner 100 from being stopped due to overload when the power storage device 200 is charged with the generated power of the solar battery 400 during the self-sustaining operation. The device 200 can be controlled. In the present embodiment, the third threshold is set to be equal to or higher than the maximum value of the intermediate link voltage, but an increase in charging power drawn by the power storage device 200 may be a power value that does not lower the intermediate link voltage (less charging current is drawn). For example, a value within the voltage range of the intermediate link voltage may be used.

  Thus, in the present embodiment, the power storage device 200 is controlled according to the value of the intermediate link voltage, not the output voltage of the DC / AC converter 102. The DC / AC converter 102 can temporarily maintain the output voltage with the accumulated power even when the intermediate link voltage decreases. Therefore, by acquiring the value of the intermediate link voltage, a sign of the voltage drop due to overload is detected earlier than the actual drop in the voltage supplied to the power storage device 200 starts, and there is a time margin. Thus, the power storage device 200 can be controlled. Thereby, there is a high possibility that an instantaneous stop of the load device 500 due to a decrease in the output voltage of the DC / AC converter 102 can be prevented.

  In addition, the value of the intermediate link voltage, which is usually a DC voltage, is a voltage that is about twice the AC voltage output from the DC / AC converter 102. Therefore, the intermediate link voltage is easy to detect a voltage change as compared with the AC voltage output from the DC / AC converter 102, and can detect the change with about twice the resolution. Therefore, in the present embodiment, it is possible to perform control with higher accuracy than the method of controlling the power storage device 200 according to the value of the output voltage of the DC / AC converter 102. Thereby, in this embodiment, generation | occurrence | production of the stop by overload of power generators, such as a solar power generation system, can be reduced.

  In addition, when the control unit 302 controls the power storage device 200 to increase the charging power when the value of the intermediate link voltage is equal to or higher than a predetermined threshold (third threshold), the generated power of the solar battery 400 is increased. When there is a margin, the power storage device 200 can be charged rapidly.

(Stage control of power storage device)
Control unit 302 may set a plurality of threshold values, compare the plurality of threshold values with the value of the intermediate link voltage, and control power storage device 200 in stages according to the value of the intermediate link voltage. . FIG. 2 shows an example of a plurality of threshold values and control of the power storage device 200 according to the threshold values. The example shown in FIG. 2 is an example when the power conditioner 100 is designed so that the value of the intermediate link voltage is 230 to 250V.

  In the example illustrated in FIG. 2, when the value of the intermediate link voltage is 230 V or less, the control unit 302 prohibits the charging operation and controls the power storage device 200 not to draw the charging power from the power conditioner 100. To do.

  In addition, when the value of the intermediate link voltage is 230 to 235 V, control unit 302 performs control to reduce the charging power that power storage device 200 draws from power conditioner 100.

  In addition, when the value of the intermediate link voltage is 235 to 245 V, control unit 302 performs control so that power storage device 200 draws normal charging power from power conditioner 100.

  Further, when the value of the intermediate link voltage is 245 to 255 V, the control unit 302 controls the power storage device 200 to operate in the quick charge mode and increases the charging power that the power storage device 200 draws from the power conditioner 100. To do.

  As described above, the control unit 302 compares the value of the intermediate link voltage with a plurality of threshold values, and controls the charging power of the power storage device 200 in a stepwise manner in accordance with the value of the intermediate link voltage, whereby the power control device 300 can control the power storage device 200 more finely.

(Judged by combining solar cell output and intermediate link voltage)
Control unit 302 of power control device 300 may control power storage device 200 based on a combination of the output voltage of solar cell 400 and the intermediate link voltage.

  The detection unit 103 of the power conditioner 100 detects the output voltage of the solar battery 400 (that is, the input voltage of the DC / DC converter 101) and the intermediate link voltage, and transmits the detected voltage to the power control apparatus 300.

  The control unit 302 calculates an average value of the output voltage of the solar battery 400 in a predetermined period, and determines whether the average value of the output voltage is increasing or decreasing.

  Here, when the average link voltage of the solar battery 400 is increasing, the intermediate link voltage is decreasing, so that the power storage device 200 is charged even if the generated power is increasing. Since it indicates that the charging power cannot be obtained sufficiently, it can be determined that an overload condition can occur.

  Therefore, control unit 302 reduces the charging power that power storage device 200 draws from power conditioner 100 when the average value of the output voltage of solar battery 400 is increasing and the intermediate link voltage is decreasing. To control.

  As described above, the control unit 302 detects the overload state more quickly by determining whether the output voltage of the solar battery 400 and the intermediate link voltage are combined to determine whether or not the overload state is present. Thus, the power storage device 200 can be controlled.

(Control based on fluctuation of intermediate link voltage)
Control unit 302 may control the charging power that power storage device 200 draws from power conditioner 100 not only by comparing the value of the intermediate link voltage with the threshold value but also by comparing the value of the intermediate link voltage acquired last time. . An example of a flowchart for performing such control is shown in FIG.

  The power control system 10 shifts to a self-sustained operation when the system fails (step S101).

  The acquisition unit 301 of the power control device 300 acquires the intermediate link voltage N from the power conditioner 100 (step S102).

  The control unit 302 of the power control apparatus 300 determines whether or not the currently acquired intermediate link voltage N is greater than the previously acquired intermediate link voltage X (step S103).

  When it determines with Yes in step S103, the control part 302 increases the charging power of the electrical storage apparatus 200 (step S104).

  When it determines with No in step S103, the control part 302 determines whether the intermediate link voltage N acquired this time is smaller than the intermediate link voltage X acquired last time (step S105).

  When it determines with Yes in step S105, the control part 302 reduces the charging power of the electrical storage apparatus 200 (step S106).

  When it determines with No in step S105, ie, when the intermediate link voltage N acquired this time and the intermediate link voltage X acquired last time are equal, the control part 302 maintains the charging electric power of the electrical storage apparatus 200 as it is (step). S107).

  When step S104, step S106 or step S107 is executed, the control unit 302 replaces the intermediate link voltage N with the intermediate link voltage X (step S108), and returns to step S102.

  In this way, by increasing or decreasing the charging power according to the increase or decrease of the voltage with respect to the previous intermediate link voltage, the power storage device 200 is pulled in earlier with a smaller number of determinations than when compared with the first to third threshold values. It becomes possible to control charging power.

(Sending cancel signal for overload protection operation)
When the power storage device 200 controls the charging power drawn from the power conditioner 100, the control unit 302 of the power control device 300 also performs an overload protection operation until the power conditioner 100 completes control of the power storage device 200. An overload protection operation cancel signal (so-called standby signal) may be transmitted so as to suppress the start of the operation. At this time, in consideration of the case where the completion of control of the charging power is delayed due to an error of the power storage device 200 or the like, protection for limiting the valid time of the signal to about 1 to 10 seconds may be set.

[Second Embodiment]
FIG. 4 is a diagram showing a schematic configuration of the power control system 20 according to the second embodiment of the present invention. The power control system 20 includes a power conditioner 150, a power storage device 200, a solar battery 400, and a load device 500.

  In the power control system 20 according to the second embodiment, the power control device 300 is included in the power conditioner 150, and the power control according to the first embodiment is that the power conditioner 150 directly controls the power storage device 200. Different from system 20. About another point, since the power control system 20 which concerns on 2nd Embodiment is the same as that of the power control system 10 which concerns on 1st Embodiment, description is abbreviate | omitted.

[Third Embodiment]
FIG. 5 is a diagram showing a schematic configuration of a power control system 30 according to the third embodiment of the present invention. The power control system 30 includes a power conditioner 100, a power storage device 250, a solar battery 400, and a load device 500.

  In the power control system 30 according to the third embodiment, the power control device 300 is included in the power storage device 250, and the power storage device 250 directly acquires the intermediate link voltage from the power conditioner 100, and the acquired intermediate link voltage. It differs from the power control system 10 according to the first embodiment in that the charging power of the power storage device 250 is controlled according to the value. About another point, since the power control system 30 which concerns on 3rd Embodiment is the same as that of the power control system 10 which concerns on 1st Embodiment, description is abbreviate | omitted.

  Although the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications and corrections based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention. For example, the functions included in each component, each step, etc. can be rearranged so that there is no logical contradiction, and multiple components, steps, etc. can be combined or divided into one It is. Further, although the present invention has been described mainly with respect to the apparatus, the present invention can also be realized as a method, a program executed by a processor included in the apparatus, or a storage medium storing the program, and is within the scope of the present invention. It should be understood that these are also included.

  In the present embodiment, the case where the power storage device is charged with the power generated by the solar battery has been described as an example, but the power storage device may be charged with other energy. For example, the power storage device may be charged with power generated by wind power generation or a fuel cell.

10, 20, 30 Power control system 100 Power conditioner 101 DC / DC converter 102 DC / AC converter 103 Detection unit 150 Power conditioner 200 Power storage device 201 Storage battery power conditioner 202 Storage battery 250 Power storage device 300 Power control device 301 Acquisition unit 302 Control unit 400 Solar cell 500 Load device

Claims (9)

A power control device that controls a power storage device that is charged by an output of a power conditioner that converts DC power to AC power,
An acquisition unit that acquires a value of an intermediate link voltage that is a voltage between a DC / DC converter and a DC / AC converter included in the power conditioner;
A controller that controls charging power that the power storage device draws from the power conditioner according to a value of the intermediate link voltage ;
The controller is
When the value of the intermediate link voltage is equal to or lower than a first threshold, the power storage device is controlled to reduce the charging power;
The power storage device is controlled to reduce the charging power when the value of the intermediate link voltage is equal to or lower than a second threshold value that is higher than the first threshold value in a predetermined period. power control device for. The power control device according to claim 1 , wherein the control unit controls the power storage device to increase the charging power when the value of the intermediate link voltage is equal to or greater than a third threshold value. A power control device.   The power control device according to claim 1, wherein the control unit compares the value of the intermediate link voltage with a plurality of threshold values, and determines the charging power of the power storage device according to the value of the intermediate link voltage. Power control apparatus characterized by controlling automatically. The power control apparatus according to claim 1,
The acquisition unit further acquires an input voltage of the DC / DC converter,
The controller controls the power storage device to reduce the charging power when the average value of the input voltage of the DC / DC converter tends to increase and the value of the intermediate link voltage decreases. A power control apparatus characterized by controlling. The power control apparatus according to claim 1,
The controller is
The intermediate link voltage N that is the value of the acquired intermediate link voltage is compared with the intermediate link voltage X that is the value of the intermediate link voltage acquired last time,
If the intermediate link voltage N is greater than the intermediate link voltage X, the power storage device is controlled to increase the charging power,
When the intermediate link voltage N is smaller than the intermediate link voltage X, the power storage device is controlled to reduce the charging power,
When the intermediate link voltage N is equal to the intermediate link voltage X, the power storage device is controlled to maintain the charging power. A power control device according to any one of claims 1 to 5, wherein, when controlling the charging power of said power storage device, the power conditioner, suppressing the initiation of the overload protection operation An overload protection operation cancel signal for transmitting the power control device. A power conditioner provided with the electric power control apparatus as described in any one of Claim 1 to 6 . A power storage device comprising the power control device according to any one of claims 1 to 6 . A power control method for controlling a power storage device charged by an output of a power conditioner that converts DC power into AC power,
Obtaining a value of an intermediate link voltage that is a voltage between a DC / DC converter and a DC / AC converter included in the power conditioner;
Wherein in accordance with the value of the intermediate link voltage, it viewed including the steps of the power storage device to control the charging power draw from the power conditioner,
The controlling step includes
Controlling the power storage device to reduce the charging power when the value of the intermediate link voltage is equal to or lower than a first threshold;
And controlling the power storage device to reduce the charging power when the value of the intermediate link voltage is equal to or lower than a second threshold value that is higher than the first threshold value in a predetermined period. A power control method characterized by the above .

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