Power conversion device, control device, server and system

Abstract

The power conversion device of the present invention reduces the possibility of false detection in the independent operation detection process. The power conversion device converts the power generated by the distributed power source into power corresponding to the power system, and includes: a communication unit that periodically receives reception information indicating whether a fault has occurred in the power system through communication; a decoupling unit that decouples the distributed power source from the power system when the communication unit receives reception information indicating that a fault has occurred; and a control unit that starts independent operation determination processing when the communication unit does not receive reception information within a predetermined first period, and the independent operation determination processing determines whether the distributed power source is in an independent operation state by detecting changes in AC characteristics in the power system.

Description

Technical Field

[0001] The invention relates to a power conversion device, a control device, a server and a system.

[0002] Distributed power sources such as solar power generation devices are connected to the power system via a power conversion device called PCS (Power Conditioning System). The power conversion device converts the output power from the distributed power source into power corresponding to the power system. When a fault occurs in the power system, the power conversion device prevents the distributed power source from going into a standalone operation state. The standalone operation state refers to a state in which the distributed power source continues to generate electricity while being disconnected from the system power source such as a substation.

[0003] There are two types of independent operation detection processing (independent operation determination processing) for detecting whether a distributed power source is in an independent operation state: a passive mode and an active mode. In the passive mode, the change in AC characteristics generated when the distributed power source is disconnected from the state connected to the power system and transferred to the independent operation state is detected to determine whether the distributed power source is in an independent operation state. In the active mode, the change in AC characteristics when reactive power is input to the power system is detected to determine whether the distributed power source is in an independent operation state (for example, refer to patent documents 1 and 2). The distributed power source determined to be in an independent operation state is decoupled from the power system (disconnected from parallel). In the past, the independent operation detection processing was performed by a device on the distributed power source side, that is, each distributed power source itself or a power conversion device attached to the distributed power source. In addition, there is a known technology called a transmission interruption method for decoupling a distributed power source from the system, although it is not directly related to independent operation detection (for example, refer to patent documents 3, 4, and 5).

[0004] Prior art literature

[0005] Patent Literature

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2017-051063

[0007] [Patent Document 2] Japanese Patent Application Publication No. 2018-152953

[0008] [Patent Document 3] Japanese Patent Publication No. 2005-198446

[0009] [Patent Document 4] Japanese Patent Application Laid-Open No. 8-19183

[0010] [Patent Document 5] Japanese Patent Application Publication No. 2008-118733 Summary of the invention

[0011] Technical problem to be solved by the invention

[0012] When performing independent operation detection on the distributed power supply side, the device on the distributed power supply side needs to independently detect the independent operation state, so there is a possibility of false detection. Therefore, it is desired to reduce the possibility of false detection and further improve the reliability of independent operation detection.

[0013] Technical solutions adopted to solve technical problems

[0014] In a first aspect of the present invention, a power conversion device is provided. The power conversion device can convert power generated by a distributed power source into power corresponding to an electric power system. The power conversion device can include a communication unit, a decoupling unit, and a control unit. The communication unit can periodically receive reception information indicating whether a fault has occurred in the electric power system through communication. The decoupling unit can decouple the distributed power source from the electric power system when the communication unit receives reception information indicating that a fault has occurred. The control unit can start a separate operation determination process when the communication unit does not receive any reception information within a predetermined first period. The separate operation determination process determines whether the distributed power source is in a separate operation state by detecting changes in the AC characteristics in the electric power system.

[0015] The independent operation determination process can determine whether the distributed power source is in the independent operation state by detecting a change in AC characteristics in the power system when reactive power is input into the power system.

[0016] The parallel-off unit may also parallel-off the distributed power source from the electric power system when it is determined in the independent operation determination process that the distributed power source is in the independent operation state.

[0017] When the communication unit receives an instruction to start the independent operation determination process, the control unit may start the independent operation determination process.

[0018] The communication unit may be connected to the server via a communication circuit so as to be communicable. The communication unit may receive reception information from the server.

[0019] When there is no failure in the electric power system, the received information may include a transmission request for transmitting the data of the power output value of the distributed power source to the server, or a notification of completion of receiving the data of the power output value.

[0020] When the communication unit does not receive the reception information from the server within the predetermined second period, the communication unit may receive the reception information from at least one other device different from the server.

[0021] The other device may be an aggregator device that is communicatively connected to the server and the power conversion device and manages the demand and supply of power. The power conversion device may include an instruction sending unit. When the communication unit does not receive the reception information from the server within the predetermined second period, the instruction sending unit may send an instruction to obtain and send the reception information from the server to the aggregator device.

[0022] The other devices may be multiple fault detection units arranged at multiple predetermined locations in the power system. Each fault detection unit may be connected to the power conversion device via a communication circuit so as to be able to communicate with each other. The power conversion device may include an instruction sending unit. When the communication unit does not receive any reception information from the server within the predetermined second period, the instruction sending unit may send an instruction to send the reception information to the multiple fault detection units.

[0023] The communication unit may be connected to a plurality of fault detection units provided at a plurality of predetermined positions in the power system via a communication circuit so as to be communicable therewith. The communication unit may receive reception information from each of the plurality of fault detection units.

[0024] The second mode of the present invention provides a control device. The control device can control a power conversion device. The power conversion device can convert the power generated by the distributed power source into power corresponding to the power system. The control device may include a communication unit, a decoupling unit, and a control unit. The communication unit may periodically receive reception information indicating whether a fault has occurred in the power system through communication. The decoupling unit may decouple the distributed power source from the power system when the communication unit receives reception information indicating that a fault has occurred. When the communication unit does not receive any reception information within a predetermined first period, the control unit may start a separate operation determination process, which determines whether the distributed power source is in a separate operation state by detecting changes in the AC characteristics in the power system.

[0025] The third mode of the present invention provides a server. The server can communicate with multiple power conversion devices that convert power generated by each distributed power source into power corresponding to the power system. The server may include an acquisition unit and an information sending unit. The acquisition unit may acquire information about whether a fault has occurred in the power system from multiple fault detection units through a communication circuit. Multiple fault detection units may be set at multiple predetermined positions in the power system. In the case where no fault has occurred in the power system, the information sending unit may periodically send a transmission information indicating that no fault has occurred. In the case where the information sending unit determines that a fault has occurred in the power system based on the acquired information, in order to decouple one or more distributed power sources associated with the fault occurrence location in the power system from the power system, the transmission information indicating that a fault has occurred may be sent to the power conversion device corresponding to the one or more distributed power sources.

[0026] The information on the presence or absence of a fault in the electric power system from each fault detection unit may include location information of a fault occurrence site.

[0027] The server may further include a start instruction sending unit. When the acquisition unit cannot obtain information about whether a fault has occurred from one or more fault detection units among the multiple fault detection units within a predetermined period, the start instruction sending unit may send a start instruction for starting the independent operation determination process to one or more power conversion devices associated with the installation positions of the one or more fault detection units in the power system. The independent operation determination process may determine whether the distributed power source is in an independent operation state by detecting changes in the AC characteristics in the power system.

[0028] The server may further include a parameter value sending unit. The parameter value sending unit may send parameter values ​​for adjusting reactive power output characteristics to the plurality of power conversion devices. The reactive power output characteristics may be used for determining whether the distributed power source performs independent operation.

[0029] The server may further include a calculation unit. The calculation unit may calculate a parameter value for adjusting reactive power output characteristics based on a current value of a predetermined node in the power system and a position of the node and each power conversion device.

[0030] When no failure occurs in the electric power system, the transmission information may include a transmission request for transmitting the data of the power output value of the distributed power source to the server, or a notification of completion of receiving the data of the power output value.

[0031] In the case where no fault occurs in the power system, the transmitted information may contain information with values ​​increasing in sequence.

[0032] A fourth aspect of the present invention provides a system. The system may include a power conversion device and a server. Transmission information from the server may be received as reception information at a communication unit of the power conversion device.

[0033] In addition, the above summary of the invention does not list all the essential features of the present invention. In addition, sub-combinations of these feature groups may also constitute inventions. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a diagram showing an example of a power generation system 1 according to an embodiment of the present invention.

[0035] Figure 2 1 is a diagram showing an example of the structure of the power conversion device 200 of the present invention.

[0036] Figure 3 : is a diagram showing an example of reactive power output characteristics in the independent operation determination process.

[0037] Figure 4 is an example of the content of communication between the power conversion device 200 and the management server 300 .

[0038] Figure 5 is a flowchart showing one example of the processing of the power conversion device 200 .

[0039] Figure 6 : is a flowchart showing an example of the independent operation determination process.

[0040] Figure 7 2 is a diagram showing another example of the structure of the power conversion device 200 .

[0041] Figure 8 It is shown in Figure 7 The flowchart of one example of the process when the power conversion device 200 does not receive a signal from the management server 300 is shown.

[0042] Fig. 9 2 is a diagram showing another example of the structure of the power conversion device 200 .

[0043] Fig.10 2 is a diagram showing an example in which the power conversion device 240 and the control device 210 are configured separately.

[0044] Fig.11 2 is a diagram showing another example of the structure of the power conversion device 200 .

[0045] Fig.12 is a flowchart showing another example of the independent execution determination process.

[0046] Fig.13 is a diagram showing an example of the management server 300 .

[0047] Fig.14 is a flowchart showing one example of the processing of the management server 300 .

[0048] Fig.15 It is a diagram showing a modified example of the management server 300 .

[0049] Fig.16 : is a flowchart showing an example of the parameter value adjustment process performed by the management server 300 . DETAILED DESCRIPTION

[0050] The present invention will be described below by way of embodiments of the invention, but the following embodiments do not limit the invention involved in the claims. In addition, the combination of features described in the embodiments is not necessarily required to be a technical means for solving the technical problem of the present invention.

[0051] Figure 1 It is a diagram showing an example of a power generation system 1 according to an embodiment of the present invention. Figure 1 The structure of the power generation system 1 is schematically shown. The power generation system 1 is a system provided in the power system 2. The power generation system 1 includes distributed power sources 10-1, 10-2, and 10-3; loads 12-1 and 12-2; fault detection units 14-1 and 14-2; a system power source 20; and a control system 100. The control system 100 may include a plurality of power conversion devices 200-1, 200-2, and 200-3 (sometimes collectively referred to as power conversion devices 200); and a management server 300. The number of each component is not limited to Figure 1 The power conversion device 200 may also be a device called a PCS (power conditioning system) or an inverter.

[0052] The system power supply 20 connected to the power system 2 may be a device that supplies power provided by a power supplier that manages the power system 2. As an example, the system power supply 20 may be a power station, a substation, or a transformer. In this example, the system power supply 20 is a substation. The power system 2 may be a distribution system under the control of the system power supply 20. The loads 12-1 and 12-2 are devices that receive power and consume power. The distributed power sources 10-1, 10-2, and 10-3 may be power sources such as solar power generation devices using solar panels, wind power generation devices, and fuel cell power generation devices.

[0053] Fault detection units 14-1 and 14-2 (sometimes collectively referred to as fault detection unit 14) can be provided at a plurality of predetermined locations within the power system 2. Fault detection unit 14-1 can include sensor unit 15-1 and switch 16-1. Similarly, fault detection unit 14-2 can include sensor unit 15-2 and switch 16-2. Sensor unit 15-1 and sensor unit 15-2 can include various sensors such as current sensors for detecting currents such as ground fault current and short circuit current. Sensor units 15-1 and 15-2 can detect the occurrence of a fault such as a ground fault in the power system 2 and the location of the fault occurrence site based on the characteristic values ​​of the measured current, etc.

[0054] The switches 16-1 and 16-2 may be electromagnetic contactors. Electromagnetic contactors are devices that use the force of an electromagnet to switch contacts, and are also called contactors. The switches 16-1 and 16-2 are not limited to electromagnetic contactors, but may also be circuit breakers such as relays. When the sensor units 15-1 and 15-2 detect the occurrence of a fault such as a ground fault in the power system 2 and the location of the occurrence, they may send a control signal to the switches 16-1 and 16-2 corresponding to the location of the occurrence of the fault. If the switches 16-1 and 16-2 receive the control signal, they become disconnected and cut off the power supply from the system power supply 20.

[0055] The management server 300 periodically obtains the presence or absence of fault information from the fault detection units 14-1 and 14-2. The period in which the management server 300 obtains the presence or absence of fault information is, for example, less than 2 seconds, more preferably less than 1 second, and further preferably less than 0.2 seconds. The management server 300 can be managed by a system operator such as a power company. However, this is not limited to this case, and the management server 300 can also be managed by managers of the power conversion devices 200-1, 200-2, and 200-3.

[0056] The fault information may be information related to characteristic values ​​such as current measured by the sensor unit 15-1 and the sensor unit 15-2. In one example, the sensor unit 15-1 and the sensor unit 15-2 may send the fault information not only to the switch 16-1 and the switch 16-2, but also to the management server 300. The fault information may include whether a fault has occurred and the location of the fault. On the other hand, the management server 300 may obtain information indicating the switch state of the switches 16-1 and 16-2 as the fault information. In the switches 16-1 and 16-2, the open state indicates that a fault has occurred, and the closed state indicates that no fault has occurred.

[0057] The management server 300 periodically sends information indicating whether a fault has occurred in the power system 2 as transmission information to the power conversion devices 200-1, 200-2, and 200-3 based on the fault information obtained from the fault detection units 14-1 and 14-2. The management server 300 sends the transmission information to the power conversion devices 200-1, 200-2, and 200-3 via the communication circuit 4. The communication circuit 4 may be a wired or wireless communication circuit. The management server 300 may receive the fault information from the fault detection units 14-1 and 14-2 via the communication circuits 6-1 and 6-2.

[0058] The power conversion device 200-1 converts the power generated by the distributed power source 10-1 into power corresponding to the power grid 2. The power conversion devices 200-2 and 200-3 similarly convert the power generated by the distributed power sources 10-2 and 10-3, respectively.

[0059] The power conversion devices 200-1, 200-2, and 200-3 each receive, as received information, the transmission information transmitted from the management server 300. Specifically, the power conversion devices 200-1, 200-2, and 200-3 each receive information indicating whether a failure has occurred in the power system 2.

[0060] Power conversion devices 200-1, 200-2 and 200-3 each have a separate operation determination function for determining whether distributed power sources 10-1, 10-2 and 10-3 are in separate operation. However, when receiving information indicating that no failure has occurred, power conversion devices 200-1, 200-2 and 200-3 do not proceed to separate operation determination processing.

[0061] Therefore, the frequency of executing the independent operation determination process can be reduced. As a result, the frequency of the independent operation determination process independently executed by the power conversion devices 200-1, 200-2 and 200-3 can be reduced. Since the paralleling can be performed based on the received information indicating whether a fault has occurred from the upper management server 300, the possibility of false detection can be reduced, and the reliability can be further improved.

[0062] When the independent operation determination process is in the active mode, reactive power is input to the power system 2. The reactive power input to the power system causes the voltage of the circuit to change repeatedly, so that the lighting in the home, etc. flickers. In this regard, since the frequency of executing the independent operation determination process can be reduced, the flicker can be prevented as much as possible.

[0063] Figure 22 is a diagram showing an example of the structure of the power conversion device 200 of the present invention. The power conversion device 200 may include a control device 210 and a power conversion unit 220. The control device 210 may include a communication unit 212, a parallel-off control unit 214, a control unit 216, a parallel-off unit 218, and a separate operation determination unit 230. In addition, the parallel-off control unit 214, the control unit 216, and the separate operation determination unit 230 may be implemented by software executed by a CPU, or may be implemented by hardware such as a logic circuit.

[0064] The power conversion unit 220 converts the power from the distributed power source 10 into AC power corresponding to the power system 2. The power conversion unit 220 includes an inverter 222 and an inverter control unit 224. In this example, the power conversion unit 220 is connected to the positive terminal P and the negative terminal N of the distributed power source 10. In this example, the direct current is converted into three-phase alternating current. The converted three-phase alternating current is supplied to the power system 2 including the power lines L1, L2, and L3. However, unlike this example, the power conversion unit 220 can also convert the power from the distributed power source 10 into multi-phase alternating current or single-phase alternating current other than three-phase alternating current.

[0065] Inverter 222 converts DC or AC from distributed power source 10 into AC matching the power grid and outputs it. Inverter control unit 224 controls the voltage, frequency and phase of the AC outputted by inverter 222 to match the power on the power grid side.

[0066] The communication unit 212 periodically receives reception information indicating whether a fault has occurred in the power system 2 through communication. In this example, the communication unit 212 is connected to the management server 300 so as to be able to communicate through the communication loop 4. The communication unit 212 can receive the reception signal at a period of less than 2 seconds, and more preferably, the reception signal is received at a period of less than 1 second. It is further preferred that the communication unit 212 receives the reception signal at a period of less than 0.2 seconds.

[0067] The communication unit 212 periodically receives a reception signal from the management server 300. When the communication unit 212 receives reception information indicating that a fault has occurred, the disconnection unit 218 disconnects the distributed power source 10 from the power system 2. As an example, the disconnection unit 218 is an electromagnetic contactor. When the communication unit 212 receives reception information indicating that a fault has occurred, the disconnection control unit 214 controls so that the contact of the disconnection unit 218 is set to an open state. As a result, the power system 2 is disconnected from the distributed power source 10.

[0068] When the communication unit 212 does not receive any reception information within the predetermined first period, the control unit 216 starts the independent operation determination process. In this case, the control unit 216 sends a control signal for starting the independent operation determination process to the independent operation determination unit 230. The independent operation determination process is a process for determining whether the distributed power source 10 is in the independent operation state by detecting a change in the AC characteristics in the power system 2.

[0069] When the communication unit 212 receives the start instruction of the independent operation determination process from the management server 300 , the control unit 216 also starts the independent operation determination process. In this case, the control unit 216 sends a control signal to the independent operation determination unit 230 to start the independent operation determination process.

[0070] The independent operation determination unit 230 performs independent operation determination processing. The independent operation determination unit 230 may include a voltage detection unit 232, a frequency deviation calculation unit 234, and a reactive power input unit 236. The voltage detection unit 232 detects the voltage on the output side of the power conversion device 200 in the power system 2. In this example, in the three-phase AC power lines L1, L2, and L3, the voltage V12 between L1 and L2, the voltage V23 between L2 and L3, and the voltage V31 between L3 and L1 are detected. The frequency deviation calculation unit 234 calculates the frequency based on the voltage detected by the voltage detection unit 232. In addition, the frequency deviation calculation unit 234 calculates the frequency deviation by finding the difference between the representative value (average value, etc.) of the frequency in one period and the representative value (average value, etc.) of the frequency in other periods before one period. In addition, the frequency deviation calculation unit 234 may calculate the parameters associated with the frequency deviation instead of calculating the frequency deviation itself. The frequency deviation calculation unit 234 may calculate the reciprocal of the frequency deviation, that is, the deviation of the period.

[0071] The reactive power input unit 236 promotes frequency fluctuation by inputting reactive power corresponding to the frequency deviation into the power system 2. In other words, in this example, the independent operation determination process can be an active method for determining whether the distributed power source is in the independent operation state by detecting the change of the AC characteristics when the reactive power is input into the power system 2. The independent operation determination unit 230 determines that the distributed power source 10 is in the independent operation state when the value of the frequency deviation when the reactive power is input into the power system 2 is greater than a predetermined value. In the case where it is determined by the independent operation determination process that the power conversion device is in the independent operation state, the decoupling unit 218 also decouples the distributed power source 10 from the power system 2.

[0072] Figure 32 is a graph showing an example of reactive power output characteristics in the independent operation determination process. The horizontal axis is the frequency deviation calculated by the frequency deviation calculation unit 234, and the vertical axis is the reactive power input by the reactive power input unit 236. The reactive power input unit 236 refers to Figure 3 The reactive power output characteristics shown in the figure can be used to calculate the reactive power value corresponding to the frequency deviation. In this example, when the absolute value of the frequency deviation is less than a, the slope of the ratio of the change in reactive power to the change in frequency deviation is smaller than the slope of the ratio of the change in reactive power to the change in frequency deviation when the absolute value of the frequency deviation is greater than a and less than b. In the range where the frequency deviation is greater than +b, the reactive power is fixed to the maximum value (max). In the range where the absolute value of the frequency deviation is less than -b, the reactive power is fixed to the minimum value (min).

[0073] exist Figure 3 In the figure, as reactive power output characteristics, the first example represented by a solid line and the second example represented by a dotted line are shown. In the region where the absolute value of the frequency deviation is greater than a and less than b, the slope of the first example representing the ratio of the change in reactive power to the change in frequency deviation is greater than that of the second example. The slope representing the ratio of the change in reactive power to the change in frequency deviation is an example of a parameter value for adjusting the reactive power output characteristics. In this example, the parameter value for adjusting the reactive power output characteristics can be adjusted. However, the parameter value for adjusting the reactive power output characteristics can also be fixed.

[0074] Figure 4 This is an example of the content of communication between the power conversion device 200 and the management server 300. The power conversion device 200 receives the transmission information transmitted from the management server 300 as a reception signal. The reception signal is a signal indicating whether a failure has occurred.

[0075] When a fault occurs in the power system 2, the communication unit 212 receives a reception signal indicating that a fault has occurred. When the communication unit 212 receives the reception signal indicating that a fault has occurred, the parallel-off unit 218 parallel-offs the distributed power source 10 from the power system 2. Therefore, the reception signal indicating that a fault has occurred is equivalent to the parallel-off instruction signal.

[0076] When no fault occurs in the power system 2, the communication unit 212 periodically receives a reception signal indicating that no fault occurs. The reception signal indicating that no fault occurs may be any signal as long as it is a signal received periodically. Therefore, the reception signal used for other functions can be used as the reception signal indicating that no fault occurs.

[0077] The received information may include a transmission request to transmit the power output value data of the distributed power source 10 to the management server 300 or a notification of completion of receiving the power output value data. In addition, the communication unit 212 may transmit the power output value data to the management server 300 upon receiving the transmission request.

[0078] In the case where no fault occurs in the power system, the received information may include information with values ​​increasing in sequence. In one example, the increasing information may be a timestamp indicating the date and time when the management server 300 sends the information. In addition, the received information may include parameter values ​​for adjusting reactive power output characteristics. In one example, Figure 3 The value of the slope indicating the ratio of the amount of change in reactive power to the amount of change in frequency deviation as described in can be received by the communication unit 212 as reception information.

[0079] The communication unit 212 receives the start instruction of the independent operation determination process. When the management server 300 cannot obtain the fault information from the fault detection units 14-1 and 14-2 due to a communication failure in the communication circuits 6-1 and 6-2, the management server 300 cannot determine whether a fault has occurred in the power system 2. In this case, the independent operation determination process is executed in the power conversion device 200 that has received the start instruction.

[0080] Figure 5 1 is a flowchart showing an example of the processing of the power conversion device 200. When the communication unit 212 does not receive a reception signal within the predetermined first period (No in step S101, Yes in step S102), the individual operation determination processing is started (step S103).

[0081] When the communication unit 212 receives a reception signal indicating that no fault has occurred (Yes in step S101, Yes in step S104), the control unit 216 does not start the independent operation determination process. For example, when the reception signal indicating that no fault has occurred is a request to send data of the power output value of the distributed power source 10, the communication unit 212 performs a normal process such as sending the data of the power output value to the management server 300 (step S105). The communication unit 212 periodically receives a reception signal indicating that no fault has occurred (Yes in step S101).

[0082] When the communication unit 212 receives an instruction to start the independent operation determination process (step S106 is yes), the independent operation determination process is started (step S103). On the other hand, when the communication unit 212 receives a reception signal indicating that a fault has occurred (step S106 is no, step S107 is yes), the decoupling unit 218 decouples the distributed power source 10 from the power system 2 (step S108).

[0083] Only when the communication unit 212 does not receive a reception signal within the first period (step S102 is yes) or the communication unit 212 receives a start instruction of the independent operation determination process from the management server 300 (step S106 is yes), the independent operation determination unit 230 performs the independent operation determination process (step S103). In the independent operation determination process, when it is determined that the distributed power source 10 is in the independent operation state (step S109 is yes), the distributed power source 10 is disconnected from the power system 2. When it is determined that the distributed power source 10 is not in the independent operation state (step S109 is no), the process returns to step S101.

[0084] Figure 6 Yes means Figure 5 Flowchart of an example of the independent operation determination process in step S103. The independent operation determination process can adopt the standard active independent operation detection method specified in the Japan Electrical Manufacturers' Association standard JEM1498. The voltage detection unit 232 detects the voltage on the output side of the power conversion device 200 in the power system 2 (step S201).

[0085] The frequency deviation calculation unit 234 calculates the frequency of the AC signal based on the voltage detected by the voltage detection unit 232 (step S202). The frequency deviation calculation unit 234 calculates the frequency deviation by finding the difference between the representative value (average value, etc.) of the frequency in one period and the representative value (average value, etc.) of the frequency in other periods before one period (step S203). The reactive power input unit 236 inputs the reactive power corresponding to the frequency deviation to the power system 2 (step S204).

[0086] In the state where reactive power corresponding to the frequency deviation is input to the power system 2, the frequency deviation is calculated by the same method as steps S201 to S203. The independent operation determination unit 230 determines whether the absolute value of the frequency deviation in the state where the reactive power is input to the power system 2 is greater than a predetermined value (step S205). In the case where the absolute value of the frequency deviation in the state where the reactive power is input to the power system 2 is greater than the predetermined value (step S205 is yes), the independent operation determination unit 230 determines that the distributed power source 10 is in the independent operation state (step S206).

[0087] According to the power conversion device 200 in the present embodiment described above, the separate operation determination unit 230 performs the separate operation determination process only when the communication unit 212 does not receive any reception signal within the first period (step S102 is yes) or when the communication unit 212 receives a start instruction for the separate operation determination process from the management server 300 (step S106 is yes), instead of always performing the separate operation determination process periodically.

[0088] Furthermore, when the fault detection units 14-1 and 14-2 detect that a fault has occurred in the power system 2, the power conversion device 200 receives information indicating that a fault has occurred through the management server 300. Therefore, the power conversion device 200 can disconnect the distributed power source 10 from the power system 2 without performing a separate operation determination process in the device itself.

[0089] Therefore, the frequency with which the power conversion device 200 must independently perform the independent operation determination process can be reduced. As long as the reception information from the upper server such as the management server 300 can be received, it can be determined whether to disconnect the distributed power source 10 from the power system 2 based on the reception information. Therefore, the reliability can be further improved.

[0090] Furthermore, even when the independent operation determination process is active, it is possible to suppress reactive power input to the power system 2 during the independent operation determination process. As a result, voltage fluctuations due to reactive power can be prevented, and voltage flicker can be suppressed.

[0091] As a reception signal indicating that no fault has occurred, various signals used to implement other functions can be used in combination. Specifically, a signal containing at least one of a request to send data of a power output value, a notification of completion of receiving data of a power output value, a timestamp (incremental information), and an adjustment parameter of reactive power output characteristics can be used as a reception signal indicating that no fault has occurred.

[0092] Figure 7 2 is a diagram showing another example of the structure of the power conversion device 200 . Figures 2 to 6 The power conversion device 200 in FIG. 1 is described as a case where the communication unit 212 periodically receives the reception signal from the management server 300. However, the present invention is not limited to this case.

[0093] When the communication unit 212 does not receive the reception information from the management server 300 within the predetermined second period, the communication unit 212 may receive the reception information from at least one other device different from the management server 300 .

[0094] Figure 7 In FIG. 1 , as examples of other devices, an aggregator device 400 and a plurality of fault detection units 14-1 and 14-2 are shown. The aggregator device 400 is communicatively connected to the management server 300 and the power conversion device 200. The aggregator device 400 is a device that manages demand and supply of electric power.

[0095] The power conversion device 200 includes an instruction transmission unit 242. When the communication unit 212 does not receive reception information from the management server 300 within the predetermined second period, the instruction transmission unit 242 transmits to the aggregator device 400 an instruction to obtain and transmit reception information from the management server 300.

[0096] The plurality of fault detection units 14 - 1 and 14 - 2 themselves may be connected to the power conversion device 200 via a communication circuit so as to be communicable with each other. The plurality of fault detection units 14 - 1 and 14 - 2 are provided at a plurality of predetermined positions in the power system 2 .

[0097] When the communication unit 212 does not receive the reception information from the management server 300 within the predetermined second period, the instruction transmission unit 242 transmits the instruction to transmit the reception information to the plurality of fault detection units 14-1 and 14-2. The fault detection units 14-1 and 14-2 may receive the presence or absence of fault information as the reception information. The presence or absence of fault information may include information related to characteristic values ​​such as current measured by the sensor unit 15-1 and the sensor unit 15-2. The presence or absence of fault information may also include information indicating the switch state of the switches 16-1 and 16-2.

[0098] Figure 8 It is shown in Figure 7 Flow chart of an example of processing when no signal is received from the management server 300 in the power conversion device 200 shown in FIG. 1. When the second period has passed without the communication unit 212 receiving a signal from the management server 300 (step S301 is yes), the instruction transmission unit 242 transmits an instruction to transmit and receive information to other devices (step S302). When a signal is received from other devices (step S303 is yes), the same process as described above can be performed. Figure 5 The same processing from step S104 to step S107 as shown in FIG. 1 is performed. If no signal is received from other devices during the first period (step S303 is No, step S304 is Yes), the same processing as in step S104 to step S107 can be performed. Figure 5 The same processing is performed as in step S103 and step S109 shown.

[0099] according to Figure 7 and Figure 8The power conversion device 200 shown in the figure, when receiving information from the management server 300 is not received due to the state of the communication circuit, it will also receive the receiving information from other devices. Therefore, even if receiving information is not received from the management server 300, as long as the communication unit 212 can receive the receiving information indicating that there is no fault in the power system 2 from other devices, the control unit 216 will not start the separate operation determination process performed by the separate operation determination unit 230. As a result, the frequency with which the power conversion device 200 must independently perform the separate operation determination process can be reduced. As long as receiving information can be received from any device, it can be determined whether to disconnect the distributed power source 10 from the power system 2 based on the receiving information. Therefore, reliability can be further improved. In addition, it is possible to suppress the input of reactive power into the power system 2 in the separate operation determination process. As a result, voltage fluctuations caused by reactive power can be prevented, and voltage flicker can be suppressed.

[0100] Furthermore, when the reception information can be received from the management server 300, it is not necessary to receive the reception information from the plurality of failure detection units 14-1 and 14-2, so that the communication volume can be reduced.

[0101] Fig. 9 2 is a diagram showing another example of the structure of the power conversion device 200 . Fig. 9 In the power conversion device 200 shown, the communication unit 212 is connected to multiple fault detection units 14-1 and 14-2 arranged at multiple predetermined positions in the power system 2 through a communication loop so as to be able to communicate. The communication unit 212 receives the received information from the multiple fault detection units 14-1 and 14-2 respectively. The communication unit 212 can receive the information on whether there is a fault as the received information. The information on whether there is a fault can include information related to characteristic values ​​such as current measured by the sensor unit 15-1 and the sensor unit 15-2. The information on whether there is a fault can also include information indicating the switching state of the switches 16-1 and 16-2. The open state indicates that a fault has occurred, and the closed state indicates that no fault has occurred.

[0102] In this example, the multiple fault detection units 14-1 and 14-2 have a communication function. The multiple fault detection units 14-1 and 14-2 can pre-save the destination information of the power conversion device 200 of the communication destination. The destination information can be updated periodically. The fault detection units 14-1 and 14-2 use IoT technology to directly send the transmission information to the destination of the power conversion device 200. The communication unit 212 receives each transmission information from the fault detection units 14-1 and 14-2 as reception information. Except that the communication unit 212 receives the reception information from the multiple fault detection units 14-1 and 14-2 instead of the communication unit 212 receiving the reception information from the management server 300, the structure of the power conversion device 200 in this example is the same as that of the management server 300. Figures 2 to 8 The structures shown are the same, so repeated descriptions are omitted.

[0103] According to this example, even in the case where the management server 300 is not provided, the frequency of executing the independent operation determination process can be reduced. As long as the received information can be received from the plurality of fault detection units 14-1 and 14-2, it can be determined whether to disconnect the distributed power source 10 from the power system 2 based on the received information. Therefore, the reliability can be further improved. In addition, the voltage of the circuit can be prevented from repeatedly changing due to the reactive power input to the power system during the independent operation determination process. Therefore, the occurrence of flickering of lighting in a home, etc., which sometimes becomes brighter and sometimes becomes darker, can be prevented as much as possible.

[0104] Figure 2 , Figure 7 ,as well as Fig. 9 2 shows a case where the control device 210 and the power conversion unit 220 constitute one power conversion device 200. However, the control device 210 may be a control device provided separately from the power conversion device.

[0105] Fig.10 2 is a diagram showing an example in which the power conversion device 240 is configured separately from the control device 210. The power conversion device 240 has Figure 2 , Figure 7 ,as well as Fig. 9 The control device 210 is a control device 210 that controls a power conversion device 240 that converts the power generated by the distributed power source 10 into power corresponding to the power system. The control device 210 includes a communication unit 212, a decoupling unit 218, and a control unit 216.

[0106] The communication unit 212 periodically receives, through communication, received information indicating whether a fault has occurred in the power system 2. When the communication unit 212 receives the received information indicating that a fault has occurred, the disconnecting unit 218 disconnects the distributed power source 10 from the power system 2. When the communication unit 212 does not receive the received information within a predetermined first period, the control unit 216 determines whether the distributed power source 10 is in a separate operation state by detecting a change in the AC characteristics when reactive power is input to the power system 2.

[0107] Thus, by connecting the control device 210 to the outside of the conventional power conversion device 240, the frequency of executing the independent operation determination process can also be reduced. As long as the reception information from the upper server such as the management server 300 can be received, it can be determined whether to disconnect the distributed power source 10 from the power system 2 based on the received information. Therefore, the reliability can be further improved. As a result, it is possible to prevent the voltage of the circuit from repeatedly changing due to the reactive power input to the power system during the independent operation determination process.

[0108] exist Figures 1 to 10 In the above description, the case where the independent operation determination process is an active method accompanied by inputting reactive power is mainly described. However, the present invention is not limited to this case.

[0109] Fig.11 2 is a diagram showing another example of the structure of the power conversion device 200. Fig.11 In the power conversion device 200 shown in FIG. 1 , the independent operation determination unit 230 does not include the reactive power input unit 236 . Fig.11 The independent operation determination process shown is a passive method without inputting reactive power. Fig.11 The independent operation determination unit 230 detects the change in AC characteristics when the distributed power source 10 is disconnected from the power system 2 and transferred to the independent operation state, and determines whether the distributed power source 10 is in the independent operation state. Figures 1 to 10 The structure described in is the same as that described in , so the detailed description is omitted.

[0110] Fig.12 Yes means Figure 5 This is a flowchart of another example of the individual execution determination process in step S103. Fig.12 Shown as Fig.11 This is an example of the content of the independent operation determination process in the passive mode without inputting reactive power as shown.

[0111] The voltage detection unit 232 detects the voltage on the output side of the power conversion device 200 in the power system 2 (step S251). The frequency deviation calculation unit 234 calculates the frequency of the AC signal based on the voltage detected by the voltage detection unit 232 (step S252). The frequency deviation calculation unit 234 calculates the frequency deviation by finding the difference between the representative value (average value, etc.) of the frequency in one period and the representative value (average value, etc.) of the frequency in other periods before one period (step S253). The single operation determination unit 230 determines whether the difference between the representative value of the frequency in one period and the representative value of the frequency in other periods, that is, the frequency deviation, is greater than a predetermined value (step S254). When the absolute value of the frequency deviation is greater than the predetermined value (step S254 is yes), the single operation determination unit 230 determines that the distributed power source 10 is in a single operation state (step S255)

[0112] Thus, when executing the independent operation determination process in the passive mode, the frequency at which the power conversion device 200 must independently execute the independent operation determination process can also be reduced. As long as the received information can be received, it can be determined whether to disconnect the distributed power source 10 from the power system 2 based on the received information. Therefore, the reliability can be further improved.

[0113] Fig.13 3 is a diagram showing an example of a management server 300. The management server 300 can communicate with a plurality of power conversion devices 200-1, 200-2, and 200-3 that convert power generated by each distributed power source 10-1, 10-2, and 10-3 into power corresponding to the power system. The management server 300 may include an acquisition unit 302, a storage unit 303, and a communication unit 310. The communication unit 310 may include an information transmission unit 312 and a start instruction transmission unit 313. The communication unit 310 is used to communicate with the outside.

[0114] The acquisition unit 302 acquires information about whether a fault has occurred in the power system 2 from multiple fault detection units 14-1 and 14-2 provided at multiple predetermined locations of the power system 2 through the communication circuits 6-1 and 6-2. When no fault has occurred in the power system 2, the information transmission unit 312 periodically transmits transmission information indicating that no fault has occurred through the communication circuits 4-1, 4-2, and 4-3. The period may be less than 2 seconds, more preferably less than 1 second, and even more preferably less than 0.2 seconds.

[0115] When it is determined based on information obtained from multiple fault detection units 14-1 and 14-2 that a fault has occurred in the power system 2, in order to decouple one or more distributed power sources 10-1 and 10-2 among the distributed power sources 10-1, 10-2 and 10-3 that are associated with the fault location in the power system 2 from the power system 2, the information sending unit 312 sends transmission information indicating that a fault has occurred to the one or more power conversion devices 200-1 and 200-2.

[0116] The information on whether a fault has occurred in the power system 2 from each fault detection unit 14-1 and 14-2 may include location information of the fault occurrence location. The storage unit 303 stores layout information indicating the connection relationship of each node in the power system 2. The acquisition unit 302 refers to the acquired location information of the fault occurrence location and the layout information in the storage unit 303. Thus, the acquisition unit 302 can identify one or more distributed power sources 10-1 and 10-2 associated with the fault occurrence location in the power system 2 among the distributed power sources 10-1, 10-2 and 10-3.

[0117] exist Fig.13 In the example, the case where the fault detection unit 14-1 detects a fault among the multiple fault detection units 14-1 and 14-2 is illustrated. In the fault detection unit 14-1, the sensor unit 15-1 detects that a fault such as a ground fault has occurred. The sensor unit 15-1 sends a control signal to the switch 16-1, so that the switch 16-1 is turned off, and the power system 2 is disconnected between the load 12-1 and the system power supply (substation) 20.

[0118] When viewed from the system power supply (substation) 20, the distributed power supplies 10-1 and 10-2 connected downstream of the fault occurrence location are distributed power supplies related to the fault occurrence location. On the other hand, when viewed from the system power supply (substation) 20, the distributed power supply 10-3 connected upstream of the fault occurrence location is not related to the fault occurrence location. Here, downstream refers to the end side when viewed from the system power supply 20, and upstream refers to the side close to the system power supply 20.

[0119] In order to disconnect the distributed power sources 10-1 and 10-2 associated with the fault occurrence position in the power system 2 from the power system 2, the information transmission unit 312 transmits the transmission information indicating that the fault has occurred to the power conversion devices 200-1 and 200-2 corresponding to the distributed power sources 10-1 and 10-2. On the other hand, the information transmission unit 312 does not disconnect the distributed power source 10-3 that is not related to the fault occurrence position in the power system 2 from the power system 2. The information transmission unit 312 periodically transmits the transmission information indicating that the fault has not occurred to the power conversion device 200-3 corresponding to the distributed power source 10-3. In this example, among the plurality of power conversion devices 200-1, 200-2, and 200-3, the information transmission unit 312 transmits the transmission information indicating that the fault has occurred to some of the power conversion devices 200-1 and 200-2, and transmits the transmission information indicating that the fault has not occurred to the other power conversion devices 200-3.

[0120] When the acquisition unit 302 is unable to obtain information about whether a fault has occurred from one or more fault detection units 14-1 and 14-2 among the multiple fault detection units 14-1 and 14-2 within a predetermined period, the start instruction sending unit 313 sends a start instruction for starting the independent operation determination process to one or more power conversion devices associated with the installation locations of the one or more fault detection units 14-1 and 14-2 in the power system 2.

[0121] For example, when, among the multiple fault detection units 14-1 and 14-2, information on the presence or absence of a fault cannot be obtained from the fault detection unit 14-1 but information on the presence or absence of a fault can be obtained from the fault detection unit 14-2, a start instruction for starting the independent operation determination process is sent to the power conversion devices 200-1 and 200-2 associated with the installation position of the fault detection unit 14-1 in the power system 2. On the other hand, a start instruction for starting the independent operation determination process is not sent to the power conversion device 200-3.

[0122] Fig.14 4-1, 4-2, and 4-3. The period may be less than 2 seconds, more preferably less than 1 second, and more preferably less than 0.2 seconds.

[0123] When a fault occurs (Yes in step S402), the acquisition unit 302 identifies one or more distributed power sources 10-1 and 10-2 associated with the fault occurrence location in the power system 2 (step S404). In order to disconnect the distributed power sources 10-1 and 10-2 associated with the fault occurrence location in the power system 2 from the power system 2, the information transmission unit 312 transmits transmission information (disconnection instruction) indicating that a fault has occurred to the power conversion devices 200-1 and 200-2 corresponding to the distributed power sources 10-1 and 10-2 (step S405).

[0124] In addition, when the acquisition unit 302 cannot obtain information about the presence or absence of a fault from one or more fault detection units among the multiple fault detection units 14-1 and 14-2 within the predetermined third period (step S406 is yes), the acquisition unit 302 determines one or more power conversion devices 200-1 and 200-2 associated with the installation position of the one or more fault detection units 14-1 and 14-2 that cannot obtain information in the power system 2 (step S407). The start instruction sending unit 313 sends a start instruction of the independent operation determination process to the determined one or more power conversion devices 200-1 and 200-2 (step S408).

[0125] A transmission signal used for other functions can be used as a transmission signal indicating that no failure has occurred.

[0126] Fig.15 3 is a diagram showing a modified example of the management server 300. The management server 300 may include a communication unit 310, a calculation unit 320, and an increment information generation unit 322. In addition to the information transmission unit 312 and the start instruction transmission unit 313, the communication unit 310 may further include a parameter value transmission unit 314 and a power output communication unit 315. In addition to the above structure, the structure of the management server 300 of this modified example is the same as that of Fig.13 The management servers 300 shown are identical.

[0127] Fig.16 300 is a flowchart showing an example of parameter value adjustment processing performed by the management server 300. The calculation unit 320 collects the current values ​​of a predetermined plurality of nodes in the power system 2 (step S501). The calculation unit 320 can obtain the current value of each node from the value of the current sensor. The calculation unit 320 can refer to the layout information stored in the storage unit 303 to obtain the positional relationship between the node and each power conversion device 200 (step S502).

[0128] The calculation unit 320 calculates the current value of the node and the position of the node and each power conversion device 200 for adjusting the Figure 3The parameter value of the reactive power output characteristic shown is calculated (step S503). The parameter value of adjusting the reactive power output characteristic can be Figure 3 The slope representing the ratio of the change in reactive power to the change in frequency deviation in the region above the absolute value a and below b of the frequency deviation shown can be the maximum value max, which is the reactive power value when the frequency deviation is +b, or the minimum value min, which is the reactive power value when the frequency deviation is -b.

[0129] Specifically, the wiring impedance to the power conversion device 200 can be calculated based on the current value and position relationship of the node. The larger the wiring impedance, the Figure 3 The smaller the slope of the reactive power output characteristic, which shows the ratio of the change in reactive power to the change in frequency deviation, the larger the wiring impedance. Figure 3 The absolute value of the maximum value max and the absolute value of the minimum value min in the reactive power output characteristics shown are smaller.

[0130] Thus, when performing a separate operation determination process, voltage flicker can be suppressed. The above-mentioned parameter value can change over time. The parameter value sending unit 314 sends the parameter value to the plurality of power conversion devices 200-1, 200-2 and 200-3, and the parameter value adjusts the reactive power output characteristics used by the power conversion device 200 to perform a separate operation determination process. The signal for sending the parameter value can be used as a transmission signal indicating that no fault has occurred.

[0131] Fig.15 In the embodiment, the power output communication unit 315 transmits a transmission request to transmit the data of the power output value of the distributed power source 10 to the management server 300 to the plurality of power conversion devices 200-1, 200-2, and 200-3. The power output communication unit 315 receives the data of the power output value of the distributed power source 10-1 from the plurality of power conversion devices 200-1, 200-2, and 200-3. The power output communication unit 315 may transmit a reception completion notification of the data of the power output value to the plurality of power conversion devices 200-1, 200-2, and 200-3. When no failure occurs in the power system 2, the transmission request to transmit the data of the power output value of the distributed power source 10- to the management server 300 or the reception completion notification of the data of the power output value may be used as a transmission signal indicating that no failure occurs.

[0132] The transmission information may include information whose value increases in sequence. The increasing information may be generated by the increasing information generating unit 322. The increasing information may include a timestamp. The timestamp is used to prove that the electronic data exists at a specific time and has not been tampered with afterwards. A timestamp may be added to a request for sending data of a power output value, a notification of completion of receiving data of a power output value, or information of adjustment parameters of reactive power output characteristics as the transmission information.

[0133] Thus, a signal containing at least one of a power output value data transmission request, a power output value data reception completion notification, a timestamp (incremental information), and an adjustment parameter of reactive power output characteristics can be used as a reception signal indicating that no failure has occurred.

[0134] The present invention has been described above using the embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments. It is clear to those skilled in the art that various changes or improvements can be made to the above embodiments. Such changes or improvements are also included in the technical scope of the present invention and can be understood from the description of the claims.

[0135] Please note that the execution order of the actions, processes, steps, and stages of the devices, systems, programs, and methods shown in the claims, specifications, and drawings can be implemented in any order unless "before", "previously", etc. are specifically stated, and the output of the previous processing is not used in the subsequent processing. In the action flow in the claims, specifications, and drawings, "first", "then", etc. are used for convenience of explanation, but it does not mean that it must be implemented in this order.

[0136] Description of symbols

[0137] 1 Power Generation System

[0138] 2 Power System

[0139] 4 communication loop

[0140] 6 communication loop

[0141] 10 Distributed power supply

[0142] 12 Load

[0143] 14 Fault detection unit

[0144] 15 Sensor unit

[0145] 16 Switch

[0146] 20 System Power

[0147] 100 Control Systems

[0148] 200 Power conversion device

[0149] 210 Control device

[0150] 212 Ministry of Communications

[0151] 214 Decoupling control unit

[0152] 216 Control Department

[0153] 218 Disassembly Department

[0154] 220 Power conversion unit

[0155] 222 Inverter

[0156] 224 Inverter control unit

[0157] 230 Independent operation judgment unit

[0158] 232 Voltage detection unit

[0159] 234 Frequency deviation calculation unit

[0160] 236 Reactive power input unit

[0161] 240 Power conversion device

[0162] 242 Instruction sending unit

[0163] 300 Management Server

[0164] 302 Acquisition Department

[0165] 303 Storage

[0166] 310 Ministry of Communications

[0167] 312 Information sending department

[0168] 313 Start instruction sending unit

[0169] 314 Parameter value sending unit

[0170] 315 Power Output Communication Department

[0171] 320 Computing Department

[0172] 322 Incremental information generation unit

[0173] 400 Aggregator Device.

Claims

1. A power conversion device that converts power generated by a distributed power source into power corresponding to a power system, characterized in that: include: a communication unit that periodically receives, by communication, reception information indicating whether a fault has occurred in the power system; a disconnecting unit configured to disconnect the distributed power source from the power system when the communication unit receives reception information indicating that a failure has occurred; as well as A control unit that starts a separate operation determination process when the communication unit does not receive the reception information indicating whether a fault has occurred in the power system within a predetermined first period. The separate operation determination process determines whether the distributed power source is in a separate operation state by detecting a change in an AC characteristic in the power system.

2. The power conversion device according to claim 1, characterized in that: The independent operation determination process determines whether the distributed power source is in the independent operation state by detecting a change in AC characteristics in the power system when reactive power is input to the power system.

3. The power conversion device according to claim 1 or 2, characterized in that: The parallel-off section also parallel-offs the distributed power source from the power system when it is determined by the independent operation determination process that the distributed power source is in the independent operation state.

4. The power conversion device according to claim 1 or 2, characterized in that: When the communication unit receives the instruction to start the independent operation determination process, the control unit also starts the independent operation determination process.

5. The power conversion device according to claim 1 or 2, characterized in that: The communication unit is connected to the server via a communication circuit so as to be communicable. The communication unit receives the reception information from the server.

6. The power conversion device according to claim 5, characterized in that: When no failure occurs in the electric power system, the received information includes a transmission request for transmitting data of power output values ​​of the distributed power sources to the server or a notification of completion of receiving data of power output values.

7. The power conversion device according to claim 5, characterized in that: When the communication unit does not receive the reception information from the server within a predetermined second period, the communication unit receives the reception information from at least one other device different from the server.

8. The power conversion device according to claim 7, characterized in that: The other device is an aggregator device that is communicatively connected to the server and the power conversion device and manages demand and supply of electric power, The power conversion device further includes an instruction sending unit that sends an instruction to the aggregator device to obtain and send the reception information from the server when the communication unit does not receive the reception information from the server within the predetermined second period.

9. The power conversion device according to claim 7, characterized in that: The other devices are a plurality of fault detection units provided at a plurality of predetermined positions in the power system, each of the fault detection units being connected to the power conversion device via a communication circuit so as to be communicable with each other. The power conversion device further includes an instruction transmission unit that transmits an instruction to transmit the reception information to the plurality of failure detection units when the communication unit does not receive the reception information from the server within the predetermined second period.

10. The power conversion device according to claim 1 or 2, characterized in that: The communication unit is connected to a plurality of fault detection units provided at a plurality of predetermined positions in the power system via a communication circuit so as to be communicable. The communication unit receives the reception information from each of the plurality of failure detection units.

11. A control device for controlling a power conversion device for converting power generated by a distributed power source into power corresponding to a power system, characterized in that: include: a communication unit that periodically receives, by communication, reception information indicating whether a fault has occurred in the power system; a disconnecting unit configured to disconnect the distributed power source from the power system when the communication unit receives reception information indicating that a failure has occurred; as well as A control unit that starts a separate operation determination process when the communication unit does not receive the reception information indicating whether a fault has occurred in the power system within a predetermined first period. The separate operation determination process determines whether the distributed power source is in a separate operation state by detecting a change in an AC characteristic in the power system.

12. A server capable of communicating with a plurality of power conversion devices that convert power generated by respective distributed power sources into power corresponding to a power system, characterized in that: include: an acquisition unit that acquires information on whether a fault has occurred in the power system from a plurality of fault detection units provided at a plurality of predetermined positions in the power system through a communication circuit; an information transmitting unit that, when no fault has occurred in the power system, periodically transmits information indicating that no fault has occurred, and, when it is determined based on the acquired information that a fault has occurred in the power system, transmits information indicating that a fault has occurred to a power conversion device corresponding to the one or more distributed power sources associated with a location where the fault has occurred in the power system in order to disconnect the one or more distributed power sources from the power system; as well as A start indication sending unit sends a start indication of starting a separate operation determination process to one or more power conversion devices associated with the installation positions of the one or more fault detection units in the power system when the acquisition unit is unable to acquire the information on whether a fault has occurred from one or more fault detection units among the multiple fault detection units within a predetermined period. The separate operation determination process determines whether the distributed power source is in a separate operation state by detecting changes in AC characteristics in the power system.

13. The server according to claim 12, characterized in that The information on the presence or absence of a fault in the electric power system from each fault detection unit includes location information of a fault occurrence site.

14. The server according to claim 12, wherein: The system further includes a parameter value transmitting unit that transmits a parameter value to the plurality of power conversion devices, the parameter value adjusting reactive power output characteristics used by the distributed power sources in executing the individual operation determination process.

15. The server according to claim 14, characterized in that The system further includes a calculation unit that calculates a parameter value for adjusting reactive power output characteristics based on a current value at a predetermined node in the power system and positions of the node and each power conversion device.

16. The server according to any one of claims 12 to 15, characterized in that: When no failure occurs in the electric power system, the transmission information includes a transmission request for transmitting the data of the power output value of the distributed power source to the server or a notification of completion of receiving the data of the power output value.

17. The server according to any one of claims 12 to 15, characterized in that: When no fault occurs in the power system, the transmitted information includes information with values ​​increasing in sequence.

18. A system, characterized in that: include: The power conversion device according to any one of claims 1 to 9; as well as The server according to any one of claims 12 to 17, The transmission information from the server is received as the reception information at the communication unit of the power conversion device.

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