Microgrid system and control method for microgrid system

Abstract

To provide a micro-grid system which identifies an accident section while the micro-grid system configured with an inverter power source as a main body performs an autonomous operation, and a control method for the micro-grid system.SOLUTION: A micro-grid system 1 comprises: a power distribution system 2 to which a plurality of inverter power sources 4a-4n is connected; a plurality of switches 3a-3m dividing the power distribution system into a plurality of sections; an inverter power source including a stop control unit for stopping output of power of the plurality of inverter power sources; and an opening / closing control device including a first control unit for performing opening control on the plurality of switches, a second control unit for performing closing control on the plurality of switches, on which the opening control is performed, in a previously designated order in a case where a representative inverter power source previously designated from among the plurality of inverter power sources resumes the output of power after the opening control is performed on the plurality of switches, and a first determination unit by which, in a case where a system voltage is below a threshold, a section corresponding to the switch on which the closing control is performed by the second control unit is determined as an accident section.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE An embodiment of the present invention relates to a microgrid system and a method for controlling a microgrid system. [Background technology]

[0002] In recent years, the introduction of microgrid systems has been promoted for the purpose of supplying power during disasters and large-scale power outages and for the efficient operation of distributed power sources. A microgrid system is a small-scale power system consisting of distributed power sources such as rotating machine generators and inverter power sources.

[0003] When a grid fault such as a ground fault or short circuit occurs in an autonomously operating microgrid system, it is desirable to detect the fault, identify and isolate the faulted section, and then continue to supply power to healthy sections other than the faulted section.

[0004] Conventionally, when a system fault occurs in a general power distribution system, a technology is known to identify and isolate the faulty section by using a sequential fault section detection method that uses sectional switches installed in the power distribution system (see Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] "Electricity Industry Encyclopedia" compiled by the Electricity Industry Lecture Editorial Committee, Energy Forum, 2008 Summary of the Invention [Problem to be solved by the invention]

[0006] However, since an isolated microgrid system is not connected to a higher-level system or a feeder breaker, the fault section cannot be identified using the forward fault section detection method.

[0007] In view of the above, the problem to be solved by each embodiment is to provide a new method that enables identification of a fault section when a microgrid system mainly composed of inverter power sources is operating autonomously. [Means for solving the problem]

[0008] A microgrid system according to an embodiment includes a power distribution system to which a plurality of inverter power sources are connected, a plurality of switches provided between the plurality of inverter power sources and dividing the power distribution system into a plurality of sections, a stop control unit configured to stop output of power from the plurality of inverter power sources when a system voltage falls below a threshold, a first control unit configured to open the plurality of switches when the system voltage falls below a threshold, a second control unit configured to close the plurality of switches that have been open-controlled in a pre-specified order when a pre-specified representative inverter power source among the plurality of inverter power sources resumes output of power after the plurality of switches have been open-controlled, and a first determination unit configured to determine that a section corresponding to a switch that has been closed by the second control unit is a fault section when the system voltage falls below a threshold. a second determination unit that determines whether or not there is a section to which power can be possibly supplied based on a position of the fault section in the power distribution system; a designation unit that designates a new representative inverter power source when there is a section to which power can possibly be supplied; and a first change unit that changes a timing for controlling the closing of the plurality of switches in accordance with the newly designated representative inverter power source. Equipped with When a newly designated representative inverter power source among the plurality of inverter power sources resumes output of power after the plurality of switches are controlled to be open, the second control unit controls the plurality of switches that have been controlled to be open to close at a timing when the switch is changed, and the designation unit designates the representative inverter power source based on a position of the fault section in the power distribution system and a predetermined priority order. do. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram showing an example of an overall configuration of a microgrid system according to the first embodiment. [Diagram 2] FIG. 2 is a block diagram showing an example of the configuration of each device in the microgrid system according to the first embodiment. [Diagram 3] FIG. 3 is a block diagram showing an example of the functional configuration of the control unit of the opening and closing controlgear according to the first embodiment. [Figure 4] FIG. 4 is a block diagram showing an example of a functional configuration of a control unit of the power conversion device according to the first embodiment. As shown in FIG. [Diagram 5] FIG. 5 is a block diagram illustrating an example of a functional configuration of a control unit of the EMS according to the first embodiment. [Figure 6]FIG. 6 is a flowchart showing an example of processing of the switching controlgear according to the first embodiment. [Figure 7] FIG. 7 is a block diagram showing an example of an overall configuration of a microgrid system according to the third embodiment. [Figure 8] FIG. 8 is a block diagram showing an example of the configuration of each device in the microgrid system according to the third embodiment. [Figure 9] FIG. 9 is a block diagram showing an example of the functional configuration of a control unit of the opening and closing controlgear according to the third embodiment. [Figure 10] FIG. 10 is a block diagram illustrating an example of a functional configuration of a control unit of the EMS according to the third embodiment. [Figure 11] FIG. 11 is a flowchart illustrating an example of a process of the EMS according to the third embodiment. [Figure 12] FIG. 12 is a flowchart illustrating an example of a process of the EMS according to the fourth embodiment. [Figure 13] FIG. 13 is a block diagram showing an example of an overall configuration of a microgrid system according to the fifth embodiment. [Figure 14] FIG. 14 is a block diagram showing an example of the functional configuration of a control unit of the opening and closing controlgear according to the fifth embodiment. [Figure 15] FIG. 15 is a block diagram illustrating an example of the functional configuration of the control unit of the EMS according to the fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of a microgrid system according to the present invention will be described with reference to the drawings.

[0011] (First embodiment) <Overall configuration of the microgrid system according to the first embodiment> A microgrid system 1 according to the first embodiment will be described. Fig. 1 is a block diagram showing an example of an overall configuration of the microgrid system 1 according to the first embodiment. As shown in Fig. 1, the microgrid system 1 includes a power distribution system 2, switches 3a-3m, switching controllers 30a-30m, inverter power supplies 4a-4n, step-up transformers 5a-5n, and an EMS (energy management system) 6.

[0012] The power distribution system 2 is a system for supplying electric power. A plurality of inverter power sources 4 are connected to the power distribution system 2. In the first embodiment, the power distribution system 2 is divided into 14 sections, 2a to 2n, by switches 3a to 3m. Note that the number of sections is an example and is not limited to 14. A load (not shown) is connected to the power distribution system 2. The load is a device or equipment that consumes electric power.

[0013] The switches 3a to 3m divide the power distribution system 2 into a plurality of sections. The switches 3a to 3m are devices that open and close electric circuits. Hereinafter, when there is no need to distinguish between 3a to 3n, they will simply be referred to as switches 3. The switching control devices 30a to 30m are devices that perform control such as opening and closing the switches 3a to 3m. Hereinafter, when there is no need to distinguish between 30a to 30m, they will simply be referred to as switching control devices 30. Details of the switching control devices 30 will be described later.

[0014] The inverter power supplies 4a to 4n are power supplies that control the input or load output by turning on and off a DC voltage at a high frequency. Hereinafter, when there is no need to distinguish between 4a to 4n, they will be simply referred to as inverter power supplies 4. The inverter power supplies 4 supply power to the load via the power distribution system 2.

[0015] In the first embodiment, the inverter power supply 4a is designated in advance as a representative inverter power supply. The representative inverter power supply is the inverter power supply among the inverter power supplies 4a to 4n that resumes power output the earliest when a system accident occurs in the power distribution system 2 and the output of the inverter power supplies 4a to 4n stops. The second calculation unit 243 (see FIG. 4) of the representative inverter power supply performs control to establish the voltage and frequency by itself.

[0016] Moreover, in the first embodiment, the representative inverter power supply is any one of the inverter power supplies 4 connected to an end of the microgrid (hereinafter also simply referred to as the microgrid) that the microgrid system 1 constitutes.

[0017] Therefore, in the example of Fig. 1, inverter power supply 4n may be designated as the representative inverter power supply. Also, in the example of Fig. 1, it may be configured so that it is possible to switch between inverter power supply 4a and inverter power supply 4n to be designated as the representative inverter power supply.

[0018] Furthermore, each inverter power supply 4 and the EMS 6 are connected by a communication line 7b. The second calculation unit 25 of the inverter power supply 4 receives the output power target value TV transmitted from the control unit 61 (see FIG. 2) of the EMS 6 via the communication line 7b. The inverter power supply 4 will be described in detail later.

[0019] The step-up transformers 5a to 5n step up the AC voltages output from the inverter power supplies 4a to 4n to high voltages. Hereinafter, when there is no need to distinguish between 5a to 5n, they will simply be referred to as step-up transformer 5. The AC end of the inverter power supply 4 is connected to the power distribution system 2 via the step-up transformer 5.

[0020] The EMS 6 manages the power usage status. The EMS 6 sets a power output target value and transmits it to the control unit 24 of the power conversion device 20. The EMS 6 will be described in detail later.

[0021] <Configuration of each device in the microgrid system according to the first embodiment> Next, a description will be given of the configuration of each device of the microgrid system 1 according to the first embodiment. Fig. 2 is a block diagram showing an example of the configuration of each device of the microgrid system according to the first embodiment.

[0022] First, there will be described the configuration of switching controller 30. Switching controller 30 includes control unit 31 as shown in FIG.

[0023] The control unit 31 has a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The ROM stores various programs and data executed by the CPU. The RAM temporarily stores data and programs when the CPU executes a program. The control unit 31 comprehensively controls the opening and closing control device 30 by expanding the program read from the ROM by the CPU into the RAM and executing it.

[0024] Here, we will explain the functional configuration of control section 31 of opening and closing controller 30. Figure 3 is a diagram showing an example of the functional configuration of control section 31 of opening and closing controller 30. Control section 31 comprises first control section 311, second control section 312, first determination section 313 and third control section 314 as functional configurations.

[0025] More specifically, the opening and closing control device 30 has the above-mentioned functional configuration as a software configuration through cooperation between the CPU of the control unit 31 and a program stored in the ROM or the like of the control unit 31. Note that some or all of the above-mentioned functional configuration may be realized by a hardware configuration such as the CPU of the control unit 31 or a dedicated circuit.

[0026] Switching controller 30 measures the voltage across the corresponding switch (for example, switch 3a in the case of switching controller 30a) using a voltage sensor or the like. Also, it refers to one of the voltages across the two ends. (Note that which voltage value to refer to is preset.)

[0027] The first control unit 311 controls the opening of the switch 3. Specifically, when a state in which the referenced voltage value is less than a predetermined threshold continues for a predetermined time or longer, the first control unit 311 transmits a control signal CS to the corresponding switch 3 to control the switch 3 to open.

[0028] When the voltage value being referred to recovers after the corresponding switch 3 is controlled to be open, the second control unit 312 closes the open switch 3. Specifically, when the state in which the voltage value being referred to is equal to or higher than the threshold continues for a predetermined period of time, the second control unit 312 transmits a control signal CS to the corresponding switch 3 to control the switch 3 to be closed.

[0029] Here, which voltage between both ends of the corresponding switch that the switching controlgear 30 refers to is determined in advance according to the closing control sequence of the switches 3. For example, in the first embodiment, when closing control is performed in the order of switch 3a, switch 3b, switch 3c, ..., switch 3m, it is determined in advance that the voltage value at the left end of the corresponding switch 3 is referenced for all switching controlgear 30. As a result, the switches 3 are closed in order starting from the one closest to the representative inverter power supply.

[0030] The first determination unit 313 determines whether the corresponding section is a fault section. Specifically, when the referenced voltage value becomes less than the threshold within a certain time after the corresponding switch 3 is controlled to close, the first determination unit 313 determines that the corresponding section (a section newly connected by controlling the corresponding switch 3 to close) is a fault section.

[0031] For example, when the switches 3a, 3b, . . . , 3n are controlled to be closed in this order, the section corresponding to switch 3a (switching control device 30a) is section 2b. Also, when the switches 3n, 3m, . . . , 3a are controlled to be closed in this order, the section corresponding to switch 3a is section 2a. In this way, the corresponding sections change depending on the order in which the switches 3 are controlled to be closed.

[0032] The third control unit 314 locks the corresponding switch 3. Specifically, when the corresponding section is determined to be the fault section by the first determination unit 313, the third control unit 314 transmits a control signal CS to the corresponding switch 3 (for example, switch 3a when section 2b is determined to be the fault section) to lock the switch 3. The locked switch 3 will not be controlled to close until the lock is released. As a result, power is no longer supplied to the fault section, and the fault section can be isolated.

[0033] Next, returning to Fig. 2, the configuration of the inverter power supply 4 will be described. As shown in Fig. 2, the inverter power supply 4 includes a power supply 10 and a power conversion device 20. The power supply 10 generates DC power and supplies it to the power conversion device 20. For example, the power supply 10 is configured by a renewable energy power supply such as a solar power generation facility or a wind power generation facility.

[0034] Also, for example, the power source 10 may be configured with a storage battery. In this case, the power source 10 is charged by converting AC power of the power distribution system 2 into DC power by the power conversion device 20. In this case, the power source 10 outputs the DC power and supplies it to the power conversion device 20.

[0035] The power conversion device 20 converts DC power output from the power source 10 into AC power and supplies it to the power distribution system 2. The power conversion device 20 is connected to the step-up transformer 5 and the power source 10. The power conversion device 20 includes a power conversion unit 21, a voltage and current measurement unit 22, a gate pulse generation unit 23, and a control unit 24.

[0036] The power conversion unit 21 converts the DC power output from the power source 10 into AC power based on the gate signal generated by the gate pulse generation unit 23 .

[0037] The voltage and current measurement unit 22 measures a voltage measurement value VV and a current measurement value CV. Specifically, the voltage and current measurement unit 22 measures the voltage measurement value VV and the current measurement value CV of the power output from the power conversion unit 21.

[0038] The gate pulse generating unit 23 generates a gate signal GS according to the output power target value TV transmitted from the EMS 6 .

[0039] The control unit 24 has a CPU, a ROM, and a RAM. The ROM stores various programs and various data executed by the CPU. The RAM temporarily stores data and programs when the CPU executes a program. The control unit 24 comprehensively controls the power conversion device 20 by expanding the program read from the ROM by the CPU into the RAM and executing it.

[0040] Here, a description will be given of the functional configuration of the control unit 24 of the power conversion device 20. Fig. 4 is a diagram showing an example of the functional configuration of the control unit 24 of the power conversion device 20. The control unit 24 includes a communication unit 241, a first calculation unit 242, and a second calculation unit 243 as functional components.

[0041] More specifically, the power conversion device 20 has the above-mentioned functional configuration as a software configuration through cooperation between the CPU of the control unit 24 and a program stored in the ROM or the like of the control unit 24. Note that a part or all of the above-mentioned functional configuration may be realized by a hardware configuration such as the CPU of the control unit 24 or a dedicated circuit.

[0042] The communication unit 241 controls communication with the EMS 6. Specifically, the communication unit 241 receives the output power target value TV transmitted from the EMS 6 via the communication line 7b.

[0043] The first calculation unit 242 generates a protection signal for protecting the inverter power supply 4 and transmits it to the gate pulse generation unit 23. Specifically, the first calculation unit 242 receives the voltage measurement value VV and the current measurement value CV measured by the voltage and current measurement unit 22, and generates a protection signal and transmits it to the gate pulse generation unit 23 when the voltage measurement value VV exceeds a predetermined upper limit value or falls below a predetermined lower limit value, or when the current measurement value CV exceeds a predetermined upper limit value.

[0044] As a result, a gate signal GS for blocking the gate is transmitted from the gate pulse generating unit 23 to the power converting unit 21. Then, the power converting unit 21 stops outputting electric power. Therefore, since the first calculation unit 242 controls the stop of the output of the inverter power supply 4, the first calculation unit 242 can be said to be an example of a stop control unit.

[0045] The second calculation unit 243 generates a reference value for adjusting the power output by the power conversion unit 21, and transmits it to the gate pulse generation unit 23. Specifically, the second calculation unit 243 generates a reference value based on the output power target value TV received by the communication unit 241, and the voltage measurement value VV and the current measurement value CV received from the voltage and current measurement unit 22, and transmits it to the gate pulse generation unit 23.

[0046] As a result, the gate pulse generating unit 23 transmits a gate signal GS based on the reference value to the power converting unit 21. Then, the power converting unit 21 converts DC power into AC power based on the gate signal GS, and outputs the AC power to the power distribution system 2.

[0047] The release unit 244 performs control to release the gate block of the power conversion unit 21. When the output of the inverter power supply 4 is stopped as a result of a protection signal being sent from the first calculation unit 242 to the gate pulse generation unit 23, the release unit 244 of the representative inverter power supply generates a release signal and sends it to the gate pulse generation unit 23 after a predetermined time has elapsed since the output was stopped.

[0048] The release units 244 of the inverter power supplies 4 (inverter power supplies 4b to 4n in the first embodiment) other than the representative inverter power supply generate and transmit release signals to the gate pulse generation unit 23 when the voltage values ​​have recovered to normal.

[0049] As a result, the gate pulse generating unit 23 generates a gate signal GS for canceling the gate block, and transmits it to the power converting unit 21. Then, the power converting unit 21 cancels the gate block based on the gate signal GS. As the gate block is canceled, the output of power by the inverter power supply 4 is resumed under the control of the second calculation unit 243.

[0050] Next, referring back to Fig. 2, a description will be given of the configuration of the EMS 6. As shown in Fig. 2, the EMS 6 includes a control unit 61.

[0051] The control unit 61 has a CPU, a ROM, and a RAM. The ROM stores various programs and data executed by the CPU. The RAM temporarily stores data and programs when the CPU executes a program. The control unit 61 comprehensively controls the EMS 6 by expanding the programs read from the ROM by the CPU into the RAM and executing them.

[0052] Here, a description will be given of the functional configuration of the control unit 61 of the EMS 6. Fig. 5 is a diagram showing an example of the functional configuration of the control unit 61 of the EMS 6. The control unit 61 includes a setting unit 611 and a communication unit 612 as functional components.

[0053] More specifically, the EMS 6 has the above-mentioned functional configuration as a software configuration through cooperation between the CPU of the control unit 61 and a program stored in the ROM or the like of the control unit 61. Note that a part or all of the above-mentioned functional configuration may be realized by a hardware configuration such as the CPU of the control unit 61 or a dedicated circuit.

[0054] The setting unit 611 sets the output power target value TV. The setting unit 611 accumulates, for example, data on power consumption in the microgrid, and sets the output power target value TV based on the accumulated data.

[0055] The communication unit 612 controls communication with the inverter power supply 4. Specifically, the communication unit 612 transmits the output power target value TV set by the setting unit 611 to the inverter power supply 4 via the communication line 7b.

[0056] <Processing of the Microgrid System According to the First Embodiment> Next, a description will be given of the processing of the microgrid system according to the first embodiment. Fig. 6 is a flowchart showing an example of the processing of the switching controller 30 of the microgrid system 1 according to the first embodiment.

[0057] It is assumed that a system fault occurs in the microgrid, and a protection signal is generated by the first calculation unit 242 of the control unit 24 of the power conversion device 20. As a result, the gates of the power conversion units 21 of the power conversion devices 20 of the inverter power sources 4 are blocked. Then, as a result of the gates being blocked, the power conversion units 21 of all the inverter power sources 4 stop outputting power.

[0058] First, the first control section 311 of the control section 31 of the switching controller 30 checks whether the state in which the referenced voltage value is less than the threshold continues for more than a predetermined time (step S1). If the state in which the referenced voltage value is less than the threshold has not continued for more than the predetermined time (step S1: No), the process returns to step S1.

[0059] On the other hand, if the state in which the referenced voltage value is less than the threshold continues for more than the predetermined time (step S1: Yes), the first control unit 311 transmits a control signal CS to the corresponding switch 3 to open the switch 3 (step S2). Note that the same process is performed in all switching control devices 30, so that all switches 3 in the microgrid are controlled to be open.

[0060] Then, a predetermined time elapses after the output of power from the power conversion unit 21 is stopped, and a release signal is generated by the release unit 244 of the control unit 24 of the power conversion device 20 of the inverter power supply 4a, which is the representative inverter power supply. This releases the gate block of the power conversion unit 21 of the power conversion device 20 of the inverter power supply 4a. Then, the power conversion unit 21 resumes output of power.

[0061] Second control section 312 of each switching controlgear checks whether the voltage value being referred to continues to be equal to or higher than the threshold value for a predetermined period of time (step S3).

[0062] If the state where the referenced voltage value is equal to or higher than the threshold value has not continued for more than the predetermined time (step S3: No), the process returns to step S3. On the other hand, if the referenced voltage value has continued for more than the predetermined time (step S3: Yes), the second control unit 312 transmits a control signal CS to the corresponding switch 3 to close the switch 3 (step S4).

[0063] The voltage referenced by second control section 312 differs for each switching controlgear 30, and in this example, each switching controlgear refers to the voltage on the left side of the corresponding switch. For this reason, switches 3 are controlled to close in order of closest distance to inverter power supply 4a.

[0064] The first determination unit 313 determines whether or not the section corresponding to the switching controlgear 30 that includes the first determination unit 313 as a functional configuration is a fault section (step S5). Specifically, after the first determination unit 313 controls the corresponding switch 3 to be closed, the first determination unit 313 determines whether or not the corresponding section is a fault section based on whether or not the referenced voltage value becomes less than the threshold value within a certain period of time.

[0065] The first determination unit 313 determines that the corresponding section is not a fault section if the referenced voltage value does not become less than the threshold within a certain time after the corresponding switch 3 is closed, and determines that the corresponding section is a fault section if the referenced voltage value becomes less than the threshold within the certain time.

[0066] If the corresponding section is not a fault section (step S5: No), the voltage value of the newly connected section recovers, and the voltage value of that section continues to be above the threshold for a predetermined time period, causing the next switching control device 30 to close the corresponding switch 3. On the other hand, if the corresponding section is a fault section (step S5: Yes), the third control unit 314 transmits a control signal CS to the corresponding switch 3, locks the switch 3, and proceeds to the processing of step S1 (step S6).

[0067] For example, if a system fault occurs in section 2m, processing will be carried out in the order of switching controller 30b, switching controller 30a, switching controller 30c, switching controller 30d, switching controller 30e...switching controller 30l.

[0068] In this case, in the switching control devices 30 up to the switching control device 30k, the system voltage does not drop even if the corresponding switch 3 is controlled to be closed. In the switching control device 30l, the system voltage drops when the corresponding switch 3 is controlled to be closed. The switching control device 30l determines that section 2m is the fault section and locks switch 3l. This separates section 2m, which includes section 2m, the fault section, and section 2n.

[0069] In this way, by isolating the section including the faulted section 2m, the microgrid system 1 can continue to supply power to the healthy sections 2a to 2l.

[0070] <Effects of the microgrid system according to the first embodiment> Next, the effects of the microgrid system 1 according to the first embodiment will be described. The microgrid system 1 according to the first embodiment stops all inverter power sources 4 when a grid accident occurs, performs open control when the voltage value referenced by all switches 3 falls below a threshold, and after a predetermined time has elapsed, after the output of power from a pre-specified representative inverter power source is resumed, closes the open-controlled switches 3 sequentially in a pre-specified order, and when the voltage value falls below the threshold due to the connection of a new section, determines the section corresponding to the closed-controlled switch 3 as the fault section.

[0071] When a system fault occurs, it can be detected by stopping the output of all inverter power supplies 4. In addition, after a predetermined time has elapsed since the fault was detected, the power output from the representative inverter power supply is resumed and the switches 3 are sequentially closed, thereby making it possible to identify the faulty section.

[0072] Therefore, according to the microgrid system 1 according to the first embodiment, it is possible to identify a fault section in a microgrid that is made up of a plurality of inverter power sources.

[0073] Furthermore, the microgrid system 1 according to the first embodiment locks the switch 3 corresponding to the fault section. This prevents the switch 3 corresponding to the fault section from being controlled to close, making it possible to isolate the section including the identified fault section. By isolating the section including the fault section, it is possible to continue power supply to sections not including the fault section.

[0074] The above-described first embodiment can be modified as appropriate by changing a part of the configuration or function of each device of the microgrid system 1. Therefore, the following describes a modified example of the above-described first embodiment as another embodiment. The following mainly describes the differences from the above-described first embodiment, and a detailed description of the commonalities with the contents already described will be omitted. The modified examples described below may be implemented individually or in appropriate combination.

[0075] <First Modification of Microgrid System According to First Embodiment> In the above-described first embodiment, a configuration has been described in which one inverter power supply 4 is provided in each section. However, there may be sections in which no inverter power supply 4 is provided. For example, the microgrid system 1 may be configured such that the inverter power supply 4a is provided in the section 2a, no inverter power supply 4 is provided in the section 2b, the inverter power supply 4b is provided in the section 2c, and no inverter power supply 4 is provided in the section 2d.

[0076] According to this modification, it is possible to divide the microgrid into sections whose number is greater than the number of inverter power sources 4.

[0077] <Modification 2 of the microgrid system according to the first embodiment> In the above-described first embodiment, a configuration has been described in which one switching controller 30 controls the opening and closing of one switch 3. However, one switching controller 30 may control the opening and closing of multiple switches 3. According to this modification, one switching controller 30 can comprehensively control the opening and closing of multiple switches 3.

[0078] Second embodiment A microgrid system 1 according to a second embodiment will be described. In the second embodiment, a configuration will be described in which inverter power sources 4 (for example, inverter power sources 4b to 4m in FIG. 1) other than the inverter power sources 4 located at both ends of the microgrid can also be designated as representative inverter power sources. In the description of the second embodiment, parts showing the same operations as those in the above-mentioned first embodiment are given the same reference numerals in the drawings, etc., and detailed descriptions thereof will be omitted.

[0079] <Configuration of Microgrid System According to Second Embodiment> The configuration of the microgrid system 1 according to the second embodiment is similar to that of the first embodiment. However, for example, in the microgrid system 1 according to the second embodiment, an inverter power supply 4c located at a location other than an end of the microgrid is designated in advance as a representative inverter power supply.

[0080] In this case, switching controllers 30a, 30b refer to the voltage value on the right side of the corresponding switch 3, and the other switching controllers refer to the voltage on the left side of the corresponding switch 3. Also, the time from when the voltage value on the left side of switch 3c recovers until switching controller 30c controls switch 3c to close is set longer than the other switching controllers.

[0081] As a result, in the example of Figure 1, when the inverter power supply 4c is designated as the representative inverter power supply, the switching control device 30 sequentially closes the switches 3b, 3a, 3c, 3d, 3e,..., 3m in that order.

[0082] For example, if a system fault occurs in section 2m, processing will be carried out in the order of switching controller 30b, switching controller 30a, switching controller 30c, switching controller 30d, switching controller 30e...switching controller 30l.

[0083] In this case, in the switching control devices 30 up to the switching control device 30k, the system voltage does not drop even if the corresponding switch 3 is controlled to be closed. In the switching control device 30l, the system voltage drops when the corresponding switch 3 is controlled to be closed. The switching control device 30l determines that section 2m is the fault section and locks switch 3l. This separates section 2m, which includes section 2m, the fault section, and section 2n.

[0084] <Effects of the microgrid system according to the second embodiment> The microgrid system 1 according to the second embodiment has the same effects as those of the first embodiment. Furthermore, even if the representative inverter power supply is connected to a section other than the sections at both ends of the microgrid, the fault section can be identified.

[0085] Third embodiment A microgrid system 1 according to a third embodiment will be described. In the third embodiment, a configuration in which an EMS 6 and a switch 3 are connected by a communication line 7 will be described. In the description of the third embodiment, parts showing the same operations as those in the first and second embodiments described above are denoted by the same reference numerals in the drawings etc., and detailed description thereof will be omitted.

[0086] <Overall configuration of the microgrid system according to the third embodiment> A microgrid system 1 according to the third embodiment will be described. Fig. 7 is a block diagram showing an example of an overall configuration of the microgrid system 1 according to the third embodiment. The microgrid system 1 according to the third embodiment differs from the first embodiment in that a switching controller 30 and an EMS 6 are connected by a communication line 7.

[0087] <Configuration of each device in the microgrid system according to the third embodiment> Next, a description will be given of the configuration of each device of the microgrid system 1 according to the third embodiment. Fig. 8 is a block diagram showing an example of the configuration of each device of the microgrid system 1 according to the third embodiment.

[0088] First, opening and closing controller 30 according to the third embodiment will be described. Fig. 9 is a diagram showing an example of the functional configuration of control unit 31 of opening and closing controller 30 according to the third embodiment. Control unit 31 differs from the first embodiment in that it is provided with a communication unit 315.

[0089] The communication unit 315 controls communication with the EMS 6. Specifically, when the first determination unit 313 determines that the corresponding section is a fault section, the communication unit 315 transmits an accident detection signal AD to the EMS 6 via the communication line 7. The accident detection signal AD includes information about the section determined to be the fault section.

[0090] Furthermore, the communication unit 315 receives a setting request signal SD from the EMS 6 via the communication line 7. Then, when the communication unit 315 receives the setting request signal SD, it transmits a setting information signal SI to the EMS 6 via the communication line 7. The setting information signal SI includes information related to the setting of the switch 3, such as the setting of the time from when the voltage value recovers until the switching controlgear 30 performs closing control of the corresponding switch 3, and which side of the voltage value of the corresponding switch 3 to refer to.

[0091] The communication unit 315 also receives a setting change signal CC from the EMS 6 via the communication line 7. The setting change signal CC includes information instructing a change in the setting of the switch 3, such as the setting of the time from when the voltage value recovers until the switching controlgear 30 performs closing control of the corresponding switch 3, and which side of the voltage value of the corresponding switch 3 to refer to. When the communication unit 315 receives the setting change signal CC, the setting of the corresponding switch 3 is changed as necessary according to the contents of the setting change signal CC.

[0092] Next, an inverter power supply 4 according to the third embodiment will be described. In the third embodiment, too, one of the inverter power supplies 4 included in the microgrid system 1 is designated in advance as the representative inverter power supply. However, this embodiment differs from the first embodiment in that when a representative inverter power supply command RC is transmitted from the EMS 6, the inverter power supply 4 that has received the representative inverter power supply command RC is newly designated as the representative inverter power supply.

[0093] The representative inverter power command RC is received by the communication unit 241 of the control unit 24 of the power conversion device 20.

[0094] Next, an EMS 6 according to a third embodiment will be described. The EMS 6 differs from the first embodiment in that, when a grid accident occurs, the EMS 6 performs a process of designating a new representative inverter power supply. Furthermore, the EMS 6 also differs from the first embodiment in that, when a process of designating a new representative inverter power supply is performed, the EMS 6 performs a process of changing the closing control sequence of the switches 3. Hereinafter, the functional configuration of the control unit 61 of the EMS 6 according to the third embodiment will be described in detail.

[0095] 9 is a block diagram showing an example of a functional configuration of a control unit 61 of an EMS 6 according to the third embodiment. The control unit 61 includes a setting unit 611, a communication unit 612, a second determination unit 613, a designation unit 614, and a change unit 615 as functional components.

[0096] The setting unit 611 is similar to that in the first embodiment, and therefore a detailed description thereof will be omitted. The communication unit 612 receives an accident detection signal AD from the switching controller 30 via the communication line 7. Then, when the communication unit 612 receives the accident detection signal AD, it transmits a setting request signal SD to all the switching controllers 30 via the communication line 7. Thereafter, it receives a setting information signal SI from the switching controllers 30 via the communication line 7.

[0097] Furthermore, communication unit 612 transmits a setting change signal CC generated by change unit 615, which will be described later, to switching controller 30 via communication line 7.

[0098] Second determination unit 613 receives information from each switching controller 30 and determines whether or not there is a section to which power can potentially be supplied.

[0099] Specifically, first, when an accident detection signal AD is received by communication unit 612, second determination unit 613 cooperates with communication unit 612 to transmit a setting request signal SD to all switching controllers 30. Thereafter, second determination unit 613 cooperates with communication unit 612 to receive setting information signals SI transmitted from each switching controller 30 in response to the setting request signal SD. Based on the setting information signals SI, second determination unit 613 determines whether there is a section for which determination as to whether it is a fault section has not been made.

[0100] Here, the setting information signal SI includes information on the setting of the time from when the voltage value recovers until the switching controlgear 30 performs closing control of the corresponding switch 3, and the setting of which side of the voltage value of the corresponding switch 3 to refer to. Therefore, the second determination unit 613 receives this information from each switching controlgear 30 and analyzes it together with the position of the representative inverter power supply, thereby being able to ascertain the closing control sequence of the switches 3.

[0101] The position of the representative inverter power supply can be acquired, for example, from the transmission history of the representative inverter power supply command RC.

[0102] In addition, since the second judgment unit 613 can grasp the position of the accident section from the accident detection signal AD, by analyzing the information on the position of the accident section together with the information on the closing control sequence of the switch 3, it can determine whether or not each switching control device 30 has determined whether the corresponding section is an accident section.

[0103] Then, when there is a section that has not been determined as being a fault section, the second determination unit 613 determines that there is a section that may be able to supply power. On the other hand, when there is no section that has not been determined as being a fault section, the second determination unit 613 determines that there is no section that may be able to supply power.

[0104] When there is a section where there is a possibility that power can be supplied, the designation unit 614 designates a new representative inverter power supply. Specifically, when the second determination unit 613 determines that there is a section where there is a possibility that power can be supplied, the designation unit 614 designates a new representative inverter power supply by sending a representative inverter power supply command RC to the inverter power supply 4.

[0105] The inverter power supply 4 to which the representative inverter power command RC is to be sent is determined based on the location of the fault section in the microgrid. For example, the designation unit 614 transmits the representative inverter power command RC to the inverter power supply 4 with the highest priority among the inverter power supplies 4 connected to a section that has not been determined to be a fault section.

[0106] The priority order is determined in advance. For example, if inverter power supply 4a is designated in advance as the representative inverter power supply, the priority order is determined as inverter power supply 4b, inverter power supply 4c, inverter power supply 4d, ..., inverter power supply 4n. Here, the process of designation unit 614 will be described taking as an example a case where a system fault occurs in section 2d in this state.

[0107] In this case, for sections 2a to 2d, each switching control device 30 has determined whether or not the section is a fault section, but for sections 2e to 2n, each switching control device 30 has not determined whether or not the section is a fault section.

[0108] Therefore, the designation unit 614 designates the inverter power supply 4 having the highest priority (for example, the inverter power supply 4e) among the inverter power supplies 4e to 4n as a new representative inverter power supply.

[0109] As a result, if there is no fault section among sections 2e to 2n, switches 3e to 3m are controlled to be closed. The microgrid system 1 is able to isolate only section 2d, which is the fault section, and continue to output power to the other sections.

[0110] The designation unit 614 may transmit the representative inverter power supply command RC to two or more inverter power supplies 4. For example, when the inverter power supply 4c is designated as the representative inverter power supply and a system fault occurs in the section 2c, the designation unit 614 may transmit the representative inverter power supply command RC to each of the inverter power supplies 4a and 4d.

[0111] This is because, at the time when section 2c is determined to be a fault section, it has not been determined whether sections 2a to 2b and sections 2d to 2n are fault sections or not.

[0112] The change unit 615 changes the closing control sequence of the switches 3 in accordance with the newly designated representative inverter power supply. The change unit 615 is an example of a first change unit. Specifically, the change unit 615 changes, as necessary, the setting of the time from when the voltage value recovers until each switching controlgear 30 performs closing control of the corresponding switch 3, and the setting of which side of the voltage value of the corresponding switch 3 each switching controlgear 30 refers to in accordance with the newly designated representative inverter power supply.

[0113] Specifically, the change unit 615 generates a setting change signal CC corresponding to each switch 3 in accordance with the newly designated representative inverter power supply. The communication unit 612 transmits the multiple setting change signals CC generated by the change unit 615 to the corresponding switching controllers 30. This changes the closing control sequence of the switches 3.

[0114] For example, consider a case where switching controller 30c determines that section 2d is a fault section, and then designates inverter power supply 4e as a new inverter power supply by designation unit 614. In this case, change unit 615 changes the closing control sequence of switches 3 so that they are sequentially closed in the order of switch 3e...switch 3m. Note that the closing control sequence of switches 3 is determined in advance according to the position of the newly designated representative inverter power supply.

[0115] In the above example, the settings of switch 3a to switch 3d are not changed by change section 615. Also, switch 3c is locked by third control section 314 of switching controller 30c, so switch 3c is not controlled to be closed. Because switch 3c is not controlled to be closed, the voltage in section 2d is not restored. Therefore, switch 3d is not controlled to be closed either.

[0116] As a result, the switch 3c and the switch 3d are no longer controlled to be closed, so that only the section 2d, which is the fault section, can be isolated from the power distribution system 2.

[0117] <Processing of the microgrid system according to the third embodiment> Next, a description will be given of the processing of the microgrid system according to the third embodiment. Fig. 10 is a flowchart showing an example of the processing of the EMS 6 of the microgrid system 1 according to the third embodiment.

[0118] It is assumed that a system fault occurs in the microgrid, and the first control unit 311 of the control unit 31 of the switching controller 30 determines that a specific section is the fault section. As a result, an fault detection signal AD is transmitted to the EMS 6, and the communication unit 612 of the EMS 6 receives the fault detection signal AD.

[0119] First, second determination unit 613 receives information from each switching controller 30 (step S31). Specifically, in cooperation with communication unit 612, when second determination unit 613 receives accident detection signal AD, it transmits setting request signal SD to each switching controller 30. Then, in cooperation with communication unit 612, second determination unit 613 receives setting information signal SI which is a response to the setting request signal SD.

[0120] Next, the second determination unit 613 checks whether there is a section to which power can be supplied based on the presence or absence of a section that has not been determined to be a fault section (step S32). If there is no section to which power can be supplied (step S32: No), this process ends.

[0121] On the other hand, if there is a section where power can be supplied (step S32: Yes), the designation unit 614 transmits a representative inverter command to the inverter power source 4 (step S33). Specifically, the designation unit 614 transmits the representative inverter command to the inverter power source 4 that is determined based on the predetermined priority order of the inverter power sources 4 and the location of the faulted section.

[0122] Next, the change unit 615 generates a setting change signal CC for the switch 3 (step S34). Specifically, based on the position of the newly designated representative inverter power supply, the change unit 615 generates a setting change signal CC for changing the setting of the time from when the voltage value recovers until each switching controlgear 30 performs closing control of the corresponding switch 3, and the setting of which side of the voltage value of the corresponding switch each switching controlgear 30 refers to.

[0123] Then, change section 615 cooperates with communication section 612 to transmit the generated setting change signals CC to the corresponding switching controllers 30, and ends this process (step S35).

[0124] For example, if a system fault occurs only in section 2d, when switch 3c is controlled to be closed, switch 3c is locked by the third control unit of switching controller 30c. Next, second determination unit 613 of EMS 6 determines that there is a section to which power can be supplied.

[0125] Next, a representative inverter power supply command RC is transmitted to the inverter power supply 4e, and the inverter power supply 4e is newly designated as the representative inverter power supply. Then, the change unit 615 changes the closing control sequence so that the switches 3e, 3f, . . . , 3m are closed in this order.

[0126] Thereafter, for sections 2a to 2c, the process is repeated with inverter power supply 4a as the representative inverter power supply. Meanwhile, for sections 2e to 2n, the process is independently performed with inverter power supply 4e as the representative inverter power supply. As a result, only section 2d, which is the fault section, is isolated.

[0127] In this way, by isolating only the faulty section 2d, the microgrid system 1 can continue to supply power to the healthy sections 2a to 2c and 2e to 2n.

[0128] <Effects of the microgrid system according to the third embodiment> A microgrid system 1 according to the third embodiment will be described. When a section is determined to be a fault section, the microgrid system 1 according to the third embodiment designates a new representative inverter power supply based on the position of the section, and changes the closing control sequence of the switches 3 according to the newly designated representative inverter power supply.

[0129] By additionally specifying a new representative inverter power supply, it is possible to determine whether or not a section is a fault section, even if it has not been determined whether or not it is a fault section at the time when a specific section is determined to be a fault section. Therefore, according to the microgrid system 1 according to the third embodiment, it is possible to isolate only the section determined to be a fault section, and continue power supply to healthy sections.

[0130] (Fourth embodiment) A microgrid system 1 according to a fourth embodiment will be described. In the fourth embodiment, a mode will be described in which a representative inverter power supply is automatically and additionally designated without receiving a representative inverter power supply command RC from the EMS 6. In the description of the fourth embodiment, parts showing the same operations as those in the above-described first to third embodiments are given the same reference numerals in the drawings etc., and detailed description thereof will be omitted.

[0131] <Configuration of Microgrid System According to Fourth Embodiment> The microgrid system 1 according to the fourth embodiment is substantially similar to the microgrid system 1 according to the third embodiment, but differs from the third embodiment in that the EMS 6 does not include a designation unit 614 as a functional configuration. In the fourth embodiment, the representative inverter power supply is automatically designated. The inverter power supply 4 according to the fourth embodiment will be described below.

[0132] The inverter power supply 4 of the fourth embodiment is configured to become a representative inverter power supply when the voltage in the section to which it is connected continues to be below the threshold for a predetermined time. The predetermined time is set differently for each inverter power supply 4. For example, the predetermined time for the inverter power supply 4a is set to the shortest, and the predetermined time for the inverter power supply 4n is set to the longest.

[0133] For example, consider the case where a system fault occurs in section 2d. In this case, first, the first calculation unit 242 of each inverter power supply 4 generates a protection signal, which stops the output of power from all inverter power supplies 4. As a result, the voltage value referenced by each switching controlgear becomes less than the threshold value, and all switching controlgears control the corresponding switches 3 to open.

[0134] Thereafter, if the voltage value in section 2a continues to be below the threshold value for a period exceeding a predetermined time set for inverter power supply 4a, inverter power supply 4a becomes the representative inverter power supply and resumes output of power.

[0135] When the inverter power supply 4a resumes outputting power, the voltage value in section 2a becomes equal to or higher than the threshold value. If this state continues for a predetermined time period until the switch 3a is controlled to close, the switching controller 30a controls the switch 3a to close. This causes the voltage in section 2b to recover, and the voltage value in section 2b becomes equal to or higher than the threshold value.

[0136] Therefore, if the specified time for inverter power supply 4b is set to a time longer than the specified time set for inverter power supply 4a plus the time required for the voltage value in section 2b to reach or exceed the threshold value after power output is resumed, inverter power supply 4b will not become the representative inverter power supply.

[0137] The voltage in section 2b recovers and the voltage value in section 2b becomes equal to or higher than the threshold value, so switching controller 30b closes switch 3b. Similarly, since section 2c is not a fault section, switching controller 30c closes switch 3c.

[0138] Because section 2d is a fault section, the first calculation section 242 of each inverter power supply 4 generates a protection signal, which stops the output of power from all inverter power supplies 4. As a result, the voltage value referenced by switching controller 30c becomes less than the threshold value, and the first determination section of switching controller 30c determines that section 2d is a fault section. Next, the third control section locks switch 3c.

[0139] The second determination unit 613 of the EMS 6 receives information from each switching controlgear 30, and because there are sections for which it has not been determined whether they are fault sections, it determines that there are sections to which power can be supplied. The change unit 615 changes the closing control sequence according to the location of the fault section. Specifically, the change unit 615 changes, as necessary, the setting of the predetermined time until closing control of each switch 3 is performed, and the setting of which voltage between both ends of each switch each switching controlgear refers to.

[0140] Even if the inverter power supply 4a becomes the representative inverter power supply and resumes output of power, the switch 3c is not locked and controlled to be closed, so the voltage in section 2d does not recover. Therefore, the voltage in section 2d continues to be below the threshold for a predetermined period of time, and the inverter power supply 4d becomes the representative inverter power supply.

[0141] However, because section 2d is the fault section, the voltage in section 2d never exceeds the threshold. Therefore, switch 3d is not controlled to close, and the voltage in section 2e does not recover. Therefore, the voltage in section 2e continues to be below the threshold for more than a predetermined time, and inverter power supply 4e becomes the representative inverter power supply.

[0142] Because section 2e is not a fault section, the voltage in section 2e is restored, and switching controller 30e controls switch 3e to close. Similar processing is then performed for sections 2f to 2n, isolating section 2d, which is a fault section, and power supply can be continued to sections other than section 2d.

[0143] <Processing of the microgrid system according to the fourth embodiment> Next, a description will be given of the processing of the microgrid system 1 according to the fourth embodiment. Fig. 11 is a flowchart showing an example of the processing of the EMS 6 of the microgrid system 1 according to the fourth embodiment.

[0144] In the fourth embodiment, after the fault section is identified, if there is a section to which power can be supplied, a new representative inverter power supply is automatically designated without transmitting the representative inverter command RC.

[0145] For example, if a system fault occurs only in section 2d, when switch 3c is controlled to be closed, switch 3c is locked by the third control unit of switching controller 30c. Next, second determination unit 613 of EMS 6 determines that there is a section to which power can be supplied.

[0146] Then, the change unit 615 changes the closing control sequence according to the position of the section 2d that is the fault section so that the switch 3e, switch 3f, ..., switch 3m are closed in that order. Also, by locking the switch 3c, the section 2d is no longer connected to the representative inverter power supply.

[0147] As a result, the voltage value in section 2d continues to be below the threshold value for a period of time that has elapsed since the time set for inverter power supply 4d. Therefore, inverter power supply 4d becomes the new representative inverter power supply. However, because section 2d is a fault section, a protection signal is generated by first calculation unit 242 of inverter power supply 4d, and the output of inverter power supply 4d is stopped.

[0148] Therefore, the state in which the voltage value in section 2d is equal to or higher than the threshold value will not continue beyond the predetermined time until switch 3e is controlled to be closed. Therefore, switch 3d will not be controlled to be closed. As a result, the state in which the voltage value in section 2e is less than the threshold value will continue beyond the set time set for inverter power supply 4e. Therefore, inverter power supply 4e becomes the new representative inverter power supply.

[0149] Thereafter, for sections 2a to 2c, the process is repeated with inverter power supply 4a as the representative inverter power supply. Meanwhile, for sections 2e to 2n, the process is performed with inverter power supply 4e as the representative inverter power supply. As a result, only section 2d, which is the fault section, is isolated.

[0150] <Effects of the microgrid system according to the fourth embodiment> A microgrid system 1 according to the fourth embodiment will be described. The effects of the microgrid system 1 according to the fourth embodiment are substantially the same as those of the third embodiment, but unlike the third embodiment, the EMS 6 does not need to transmit a representative inverter command. Therefore, according to the microgrid system 1 according to the fourth embodiment, the processing load on the EMS 6 can be reduced.

[0151] Fifth embodiment A microgrid system 1 according to a fifth embodiment will be described. In the fifth embodiment, a configuration in which a power distribution system 2 can be connected to a higher-level system will be described. In the description of the fifth embodiment, parts showing the same operations as those in the first to fourth embodiments described above will be denoted by the same reference numerals in the drawings, etc., and detailed descriptions thereof will be omitted.

[0152] <Overall configuration of the microgrid system according to the fifth embodiment> A microgrid system 1 according to the fifth embodiment will be described. Fig. 12 is a block diagram showing an example of an overall configuration of the microgrid system 1 according to the fifth embodiment. The microgrid system 1 according to the fifth embodiment differs from the third embodiment in that it includes an upper system 8 and a feeder breaker 9.

[0153] The upper system 8 is a power supply source that supplies power to the distribution system 2. The upper system 8 is, for example, an AC power source serving as a commercial system including a power plant, a substation, and the like. The feeder breaker 9 disconnects or connects the wiring between the upper system 8 and the distribution system 2. In the example of FIG. 12, the feeder breaker 9 continuously disconnects the connection between the upper system 8 and the distribution system 2, forming a microgrid similar to that of the third embodiment.

[0154] Furthermore, when a power outage is detected in the upper system 8, the upper system 8 transmits a power outage detection signal to the EMS 6. Furthermore, when the power outage in the upper system 8 is resolved, the upper system 8 transmits a power outage resolution signal to the EMS 6.

[0155] The feeder breaker 9 performs its own opening control when it detects a fault current (a current showing a current value exceeding a predetermined threshold). The upper system 8 and the feeder breaker 9 are connected to the EMS 6 via a communication line 7b. The feeder breaker 9 also performs its own closing control in accordance with a control signal transmitted from the EMS 6.

[0156] Furthermore, when the feeder breaker 9 performs its own opening control, it transmits an opening signal to the EMS 6. Furthermore, when the feeder breaker 9 performs its own closing control, it transmits a closing signal to the EMS 6.

[0157] <Configuration of each device in the microgrid system according to the fifth embodiment> Next, a configuration of each device in the microgrid system 1 according to the fifth embodiment will be described. First, the switching controller 30 will be described.

[0158] In the microgrid system 1 according to the fifth embodiment, the switching controlgear 30 performs different processing depending on whether the microgrid system 1 is operating autonomously (hereinafter also referred to as an autonomous operation mode) or not (hereinafter also referred to as a non-island operation mode). When the microgrid system 1 is operating autonomously, the same processing as in the third embodiment is executed, and therefore a detailed description will be omitted. Note that the microgrid system 1 operates autonomously when a power outage occurs in the upper system 8.

[0159] Next, the functional configuration of control unit 31 of opening and closing controller 30 will be described. Figure 13 is a block diagram showing an example of the functional configuration of control unit 31 of opening and closing controller 30 according to the fifth embodiment. Control unit 31 of opening and closing controller 30 according to the fifth embodiment comprises a switching unit 316 in addition to the functional configuration of control unit 31 of opening and closing controller 30 according to the third embodiment.

[0160] The communication unit 315 receives an open signal and a close signal for the feeder breaker transmitted from the EMS 6 via the communication line 7a.

[0161] The switching unit 316 switches between a non-island operation mode and an isolated operation mode. Specifically, when the communication unit 315 receives an open signal of a feeder breaker transmitted from the EMS 6 during the non-island operation mode, the switching unit 316 switches from the non-island operation mode to the isolated operation mode.

[0162] Furthermore, when the communication unit 315 receives a feeder breaker close signal transmitted from the EMS 6 during the isolated operation mode, the switching unit 316 switches from the isolated operation mode to the non-isolated operation mode.

[0163] Next, a description will be given of the functional configuration of the control unit 24 of the power conversion device 20. The communication unit 241 receives an open signal and a close signal of the feeder breaker transmitted from the EMS 6 via the communication line 7b.

[0164] The first calculation unit 242 and the second calculation unit 243 perform the same processing as in the third embodiment. However, in the non-independent mode, the fault section is detected using the power supplied from the higher-level system 8 to the power distribution system 2, so that it is not necessary to specify a representative inverter power supply from among the multiple inverter power supplies 4.

[0165] Next, a functional configuration of the control unit 61 of the EMS 6 will be described. Fig. 15 is a block diagram showing an example of the functional configuration of the control unit 61 of the EMS 6 according to the fifth embodiment. The control unit 61 of the EMS 6 according to the fifth embodiment includes a connection unit 616 and a switching unit 617 in addition to the functional configuration of the control unit 61 of the EMS 6 according to the third embodiment.

[0166] The communication unit 612 receives a power failure detection signal and a power failure release signal from the upper system 8 via the communication line 7c. In addition, the communication unit 612 receives an open signal and a close signal from the feeder breaker 9 via the communication line 7c.

[0167] The second judgment unit 613, the designation unit 614, and the change unit 615 are substantially similar to those in the third embodiment, but since the designation unit 614 does not need to designate a representative inverter power supply in the non-independent operation mode, it does not execute the process of sending a representative inverter command RC to a specific inverter power supply 4.

[0168] Furthermore, when switching from the independent operation mode to the non-independent operation mode, the change unit 615 changes the setting of the switch 3 to a setting corresponding to the non-independent operation mode. The change unit 615 in this case is an example of a second change unit.

[0169] The connection unit 616 causes the feeder breaker 9 to execute a closing control. Specifically, when the connection unit 616 receives a power outage release signal from the upper system 8 during the independent operation mode, it generates a control signal that causes the feeder breaker 9 to execute a closing control. The control signal generated by the connection unit 616 is transmitted by the communication unit 612 to the feeder breaker 9 via the communication line 7b.

[0170] As a result, the feeder breaker 9 opens itself upon detection of a fault current, and then closes itself when the power outage in the upper system is released.

[0171] The switching unit 617 switches between a non-independent operation mode and an independent operation mode. Specifically, when the communication unit 612 receives an open signal transmitted from the feeder breaker 9 in the non-independent operation mode, the switching unit 617 switches from the non-independent operation mode to the independent operation mode. Also, when the communication unit 612 receives a close signal transmitted from the feeder breaker 9 in the independent operation mode, the switching unit 617 switches from the independent operation mode to the non-independent operation mode.

[0172] <Effects of the microgrid system according to the fifth embodiment> The effects of the microgrid system 1 according to the fifth embodiment will be described. The microgrid system 1 according to the fifth embodiment has the same effects as the third embodiment. In addition, by changing the conditions under which each switch 3 is controlled to be closed to the same settings as those in the third embodiment, when the upper system 8 and the power distribution system 2 are connected, the switch 3 used for detecting a fault section by the forward fault section detection method can also be used for detecting a fault section when the microgrid system 1 is operating autonomously using the inverter power supply 4.

[0173] As a result, even when the microgrid system 1 is operating autonomously using the inverter power supply 4, the fault section can be detected without adding a new switch 3.

[0174] <First Modification of Microgrid System According to Fifth Embodiment> In the above-described fifth embodiment, a configuration has been described in which the microgrid system 1 of the third embodiment further includes the upper system 8 and the feeder circuit breaker 9. However, the microgrid system 1 may be configured such that the microgrid system 1 of the fourth embodiment further includes the upper system 8 and the feeder circuit breaker 9.

[0175] In this case, in the case of the non-island operation mode, it is not necessary to designate a representative inverter power supply, and therefore a process is performed in which a representative inverter power supply is automatically designated only in the case of the island operation mode. According to the microgrid system 1 of this modification, it is possible to obtain the same effects as those of the fourth embodiment.

[0176] <Modification 2 of the microgrid system according to the fifth embodiment> In the above-described fifth embodiment, a configuration has been described in which the microgrid system 1 of the third embodiment further includes the upper system 8 and the feeder circuit breaker 9. However, the microgrid system 1 may be configured such that the microgrid system 1 of the first or second embodiment further includes the upper system 8 and the feeder circuit breaker 9.

[0177] According to the microgrid system 1 of this modification, it is possible to obtain the same effects as those of the first or second embodiment.

[0178] In addition, the programs executed by each device in the above embodiments are provided by being pre-installed in a storage medium (ROM or storage unit) included in each device, but this is not limited, and the programs may be provided by being recorded in an installable or executable format on a computer-readable storage medium such as a CD-ROM, a flexible disk (FD), a CD-R, or a DVD (Digital Versatile Disc). Furthermore, the storage medium is not limited to a medium independent of the computer or the embedded system, but also includes a storage medium in which a program transmitted via a LAN, the Internet, or the like is downloaded and stored or temporarily stored.

[0179] In addition, the programs executed by each device in the above embodiments may be stored on a computer connected to a network such as the Internet and provided by downloading them via the network, or may be provided or distributed via a network such as the Internet.

[0180] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0181] 1. Microgrid System 2 Power distribution system 3a~3m switch 30a~30m Switching control device 31 Control Unit 311 First Control Section 312 Second Control Section 313 1st Judgment Department 314 Third Control Section 315 Communications Department 316 Switching section 10 Power supply 20 Power conversion device 21 Power conversion section 22 Voltage and current measurement section 23 Gate pulse generator 24 Control Unit 241 Communications Department 242 1st calculation section 243 2nd calculation section 244 Release section 4a~4n inverter power supply 5a~5n step-up transformer 6. EMS 61 Control section 611 Setting Department 612 Communications Department 613 Second Judgment Department 614 Specified part 615 Changes 616 Connection 617 Switching section 7, 7a, 7b communication line 8 Upper system 9 Feeder circuit breaker

Claims

1. A power distribution system to which a plurality of inverter power sources are connected; A plurality of switches are provided between the plurality of inverter power sources and divide the power distribution system into a plurality of sections; a stop control unit that stops output of power from the plurality of inverter power sources when a system voltage falls below a threshold; A first control unit that controls the plurality of switches to open when the system voltage falls below a threshold value; a second control unit that closes the plurality of switches that have been opened in a predetermined order when a representative inverter power source that is designated in advance among the plurality of inverter power sources resumes output of power after the plurality of switches have been opened; a first determination unit that determines, when the system voltage falls below a threshold value, that a section corresponding to a switch that is controlled to be closed by the second control unit is a fault section; a second determination unit that determines whether or not there is a section that may be able to supply power based on a position of the fault section in the power distribution system; a designation unit that designates a new representative inverter power supply when there is a section that may be able to supply power; a first change unit that changes the timing of controlling the plurality of switches to be closed in response to a newly designated representative inverter power source; Equipped with the second control unit, when a newly designated representative inverter power source among the plurality of inverter power sources resumes output of power after the plurality of switches are controlled to be open, controls the plurality of switches that have been controlled to be open to close at a timing when the representative inverter power source resumes output of power; the designation unit designates the representative inverter power supply based on a position of the fault section in the power distribution system and a predetermined priority order. Microgrid system.

2. A power distribution system to which a plurality of inverter power sources are connected; A plurality of switches are provided between the plurality of inverter power sources and divide the power distribution system into a plurality of sections; a stop control unit that stops output of power from the plurality of inverter power sources when a system voltage falls below a threshold; A first control unit that controls the plurality of switches to open when the system voltage falls below a threshold value; a second control unit that closes the plurality of switches that have been opened in a predetermined order when a representative inverter power source that is designated in advance among the plurality of inverter power sources resumes output of power after the plurality of switches have been opened; a first determination unit that determines, when the system voltage falls below a threshold value, that a section corresponding to a switch that is controlled to be closed by the second control unit is a fault section; The upper output system, A feeder circuit breaker; a breaker that, when an accident occurs in the higher-level output system, controls the feeder breaker to open and breaks a connection with the higher-level output system; a connection unit that controls the feeder breaker to close and connects the power source to the higher-level output system after the fault in the higher-level output system is resolved; a second change unit that changes, as necessary, an order of controlling the plurality of switches to be closed depending on whether the upper system is connected or disconnected; A microgrid system comprising:

3. A third control unit is further provided for locking a switch corresponding to the section determined to be the fault section, The second control unit does not control the locked switch to be closed. The microgrid system according to claim 1 or 2.

4. The representative inverter power source is connected to one of both ends of a microgrid. A microgrid system according to any one of claims 1 to 3.

5. a second determination unit that determines whether or not there is a section that may be able to supply power based on a position of the fault section in the power distribution system; a designation unit that designates a new representative inverter power supply when there is a section that may be able to supply power; A first change unit changes the timing of controlling the plurality of switches to be closed in accordance with a newly designated representative inverter power source, When a newly designated representative inverter power source among the plurality of inverter power sources resumes output of power after the plurality of switches are controlled to be opened, the second control unit controls the plurality of switches that have been controlled to be opened to be closed at a timing changed from the designated representative inverter power source. A microgrid system according to any one of claims 2 to 4.

6. the designation unit designates the representative inverter power supply based on a position of the fault section in the power distribution system and a predetermined priority order. The microgrid system of claim 5 .

7. the designation unit newly designates an inverter power source other than the representative inverter power source as the representative inverter power source when a state in which a voltage in a section to which the designation unit is connected continues to be below a threshold value for a period of time that is set for each of the inverter power sources. The microgrid system of claim 5 .

8. The upper output system, A feeder circuit breaker; a breaker that, when an accident occurs in the higher-level output system, controls the feeder breaker to open and breaks a connection with the higher-level output system; a connection unit that controls the feeder breaker to close and connects the power source to the higher-level output system after the fault in the higher-level output system is resolved; A second change unit changes the order of closing the plurality of switches as necessary depending on whether the upper system is connected or disconnected. The microgrid system according to claim 3 or 4.

9. A control method for a microgrid system including a power distribution system to which a plurality of inverter power sources are connected, and a plurality of switches provided between the plurality of inverter power sources and dividing the power distribution system into a plurality of sections, comprising: a stop control step of stopping the output of power from the plurality of inverter power sources when a system voltage falls below a threshold value; a first control step of opening the plurality of switches when a system voltage falls below a threshold; a second control step of controlling the plurality of switches that have been opened in a predetermined order to close the plurality of switches when a predetermined designated representative inverter power source among the plurality of inverter power sources resumes output of power after the plurality of switches have been opened; a first determination step of determining, when the system voltage falls below a threshold value, that a section corresponding to the switch that is controlled to be closed in the second control step is a fault section; a second determination step of determining whether or not there is a section that may be able to supply power based on a position of the fault section in the power distribution system; a designation step of designating a new representative inverter power supply when there is a section in which power can be supplied; a first change step of changing the timing for controlling the plurality of switches to be closed in accordance with a newly designated representative inverter power source; Including, In the second control step, when a newly designated representative inverter power source among the plurality of inverter power sources resumes output of power after the plurality of switches are controlled to be open, the plurality of switches that have been controlled to be open are controlled to be closed at a timing changed from the start of the control. the designation step designates the representative inverter power supply based on a position of the fault section in the power distribution system and a predetermined priority order. A method for controlling a microgrid system.

10. A control method for a microgrid system including a power distribution system to which a plurality of inverter power sources are connected, a plurality of switches provided between the plurality of inverter power sources and dividing the power distribution system into a plurality of sections, an upper output system, and a feeder breaker, a stop control step of stopping the output of power from the plurality of inverter power sources when a system voltage falls below a threshold value; a first control step of opening the plurality of switches when a system voltage falls below a threshold; a second control step of controlling the plurality of switches that have been opened in a predetermined order to close the plurality of switches when a predetermined designated representative inverter power source among the plurality of inverter power sources resumes output of power after the plurality of switches have been opened; a first determination step of determining, when the system voltage falls below a threshold value, that a section corresponding to the switch that is controlled to be closed in the second control step is a fault section; a disconnecting step of disconnecting the power supply from the higher-level output system by controlling the feeder breaker to open when an accident occurs in the higher-level output system; a connecting step of controlling the feeder breaker to close and connect the power supply to the higher output system after the fault in the higher output system is eliminated; a second change step of changing, as necessary, the order of controlling the plurality of switches to be closed depending on whether the upper system is connected or disconnected; A method for controlling a microgrid system comprising:

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