Microgrid control system, control method, intelligent electronic device, and program

Abstract

To provide a microgrid control system, a control method of a microgrid, an intelligent electronic device, and a program, which can detect a fault current by a protection relay even when a switching operation is performed between an island mode and a grid connection mode.SOLUTION: A microgrid control system includes: a first intelligent electronic device 211 for detecting an open / closed state of a switch 210 coupling a microgrid 200 and a higher-ordered system 100; protection relays 234 and 242 for disconnecting consumers 233 and 241 from the microgrid, respectively, when detecting a fault current; and second intelligent electronic devices 235 and 243 each including a protection relay controller to apply, to the protection relay, a set value according to at least the open / closed state of the switch. The protection relays detect the fault current using the set value applied by the respective second intelligent electronic devices.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a microgrid control system, a control method, an intelligent electronic device, and a program.

Background Art

[0002] A microgrid, which is a small-scale power system that supplies power from distributed power sources to power loads, has attracted attention from the viewpoints of utilization of renewable energy and stable power supply. The operating states of a microgrid include a grid-connected mode in which it is connected to and operated by an upper-level power system, and an island mode in which it is disconnected from the upper-level power system and operated. Patent Document 1 discloses a synchronization method when interconnecting a microgrid with an adjacent power transmission system.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in a microgrid, since the fault current in the island mode is smaller than the fault current in the grid-connected mode, it is possible to detect the fault current in the island mode alone and the grid-connected mode alone, but there is a problem that it may become impossible due to the difference in the individual fault currents when switching operations.

[0005] The present disclosure has been made in view of such circumstances, and provides a microgrid control system, a control method, an intelligent electronic device, and a program capable of detecting a fault current in a protection relay even when switching operations between the island mode and the grid-connected mode are performed.

Means for Solving the Problems

[0006] The present disclosure is made to solve the above-described problems. One aspect of the present disclosure is a microgrid control system, including: a first intelligent electronic device configured to detect an open / closed state of a switch that couples a microgrid and a superior system; a protection relay configured to disconnect a consumer from the microgrid when detecting a fault current; and a second intelligent electronic device configured to set a setting value corresponding at least to the open / closed state in the protection relay, wherein the protection relay detects the fault current by using the setting value set by the second intelligent electronic device.

[0007] Another aspect of the present disclosure is the above-described microgrid control system, wherein the second intelligent electronic device includes a communication unit configured to receive, from the first intelligent electronic device, a notification indicating the open / closed state.

[0008] Another aspect of the present disclosure is the above-described microgrid control system, wherein the setting value set in the protection relay is a larger value when the open / closed state is a closed state than when the open / closed state is an open state.

[0009] Another aspect of the present disclosure is the above-described microgrid control system, wherein the setting value set in the protection relay is a value corresponding to the magnitude of a power supply source in the microgrid when the open / closed state is an open state.

[0010] Another aspect of the present disclosure is a method for controlling a microgrid, including: a step in which a first intelligent electronic device detects an open / closed state of a switch that couples the microgrid and a superior system; a step in which a second intelligent electronic device sets a setting value corresponding at least to the open / closed state in a protection relay in the microgrid; and a step in which when the protection relay detects a fault current by using the setting value set by the second intelligent electronic device, the protection relay disconnects a consumer from the microgrid.

[0011] Another aspect of the present disclosure is an intelligent electronic device for controlling a protection relay in a microgrid, comprising a protection relay control unit that sets a setting value corresponding to at least the open / closed state of a switch that connects the microgrid and a higher-level system, to the protection relay.

[0012] Another aspect of the present disclosure is a program for operating a computer of an intelligent electronic device that controls a protection relay in a microgrid, as a protection relay control unit that sets a setting value corresponding to at least the open / closed state of a switch that connects the microgrid and a higher-level system, to the protection relay.

Advantages of the Invention

[0013] According to the present disclosure, even when switching between the island mode and the grid connection mode, an accident current can be detected by the protection relay.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. FIG. 1 is a schematic block diagram showing the configuration of the power transmission and distribution system 10 according to the present embodiment. The power transmission and distribution system 10 includes an upper-level system 100 and a microgrid 200. The upper-level system 100 includes a power transmission system 110 and a large-scale power generation plant 120. The power transmission system 110 transmits the power supplied by the large-scale power generation plant 120 to the microgrid 200. The large-scale power generation plant 120 is a power supply source that supplies power to the upper-level system 100 by thermal power generation, hydraulic power generation, nuclear power generation, or other power generation. In FIG. 1, only one large-scale power generation plant 120 is shown as the power supply source included in the upper-level system 100, but the upper-level system 100 may include a plurality of power supply sources including small-scale ones.

[0016] The microgrid 200 includes a switch 210, an intelligent electronic device (IED) 211 (the first intelligent electronic device), a high-voltage system 220, a small-scale power plant 221, an IED 222, a low-voltage system 230, a storage battery 231, an IED 232, a consumer 233, a protection relay 234, an IED 235 (the second intelligent electronic device), a distribution line 240, a consumer 241, a protection relay 242, an IED 243 (the second intelligent electronic device), and a management device 250. The IEDs 211, 222, 232, 235, 243 and the management device 250 are communicably connected by a wired or wireless network (e.g., Ethernet (registered trademark)) not shown, and communicate using, for example, GOOSE (Generic Object Oriented Substation Events) defined in IEC (International Electrotechnical Commission) 61850. In this embodiment, at least the IED 211, the IED 235 or the IED 243, and the protection relay 234 or the protection relay 242 constitute a microgrid control system.

[0017] The switch 210 is installed at a location (e.g., a substation) that connects the upper-level system 100 and the microgrid 200. When in the closed state, it connects the upper-level system 100 and the microgrid 200, and when in the open state, it disconnects the upper-level system 100 and the microgrid 200. The IED 211 is installed near the switch 210 and is wired-connected to this switch 210. When the open / closed state of the switch 210 changes, the IED 211 notifies other IEDs including the IED 235 and IED 243 and the management device 250 of the changed open / closed state. When the switch 210 is in the closed state, the microgrid 200 is in the grid connection mode where it can receive and supply power from the upper-level system 100. Also, when the switch 210 is in the open state, the microgrid 200 is in the island mode where it does not receive power from the upper-level system 100. Therefore, the open / closed state of the switch 210 notified by the IED 211 also indicates whether the microgrid 200 is in the grid connection mode or the island mode.

[0018] The high-voltage system 220 is the power transmission system with the highest voltage within the microgrid 200 and is connected to the upper-level system 100 via the switch 210. The small-scale power plant 221 is a power supply source that supplies power to the microgrid 200 through thermal power generation, hydroelectric power generation, solar power generation, wind power generation, or other power generation methods. The small-scale power plant 221 is connected to the high-voltage system 220. The IED 222 is installed near the small-scale power plant 221 and is wired-connected to this small-scale power plant 221. The IED 222 notifies other IEDs including the IED 235 and IED 243 and the management device 250 of whether the small-scale power plant 221 is supplying power.

[0019] The low-voltage system 230 is a power transmission and distribution system with a voltage lower than that of the high-voltage system 220 and is connected to the high-voltage system 220 via substation equipment (not shown). The storage battery 231 stores power from the microgrid 200 and supplies power to the microgrid 200. The storage battery 231 may be a secondary battery such as a lithium-ion battery or may be a facility that stores power by storing hydrogen generated by electrolyzing water. The IED 232 is installed near the storage battery 231 and is wired-connected to this storage battery 231. The IED 232 notifies other IEDs including the IED 235 and the IED 243 and the management device 250 whether the storage battery 231 is supplying power.

[0020] The consumer 233 is a consumer connected to the microgrid 200. A consumer is a person who needs electrical supply and uses electricity after receiving the supply. The consumer 233 is a relatively large consumer that receives and supplies power at the voltage of the low-voltage system 230 from the microgrid 200. Therefore, the consumer 233 receives and supplies power at a higher voltage than the general consumer 241 described later. The protection relay 234 is installed between the low-voltage system 230 and the consumer 233. When the protection relay 234 detects a current exceeding the set pick-up value, it regards the fault current as detected and disconnects the consumer 233 from the microgrid 200. The IED 235 is installed near the protection relay 234 and is wired-connected to this protection relay 234. The IED 235 controls the protection relay 234 of the consumer 233. For example, the IED 235 sets the pick-up value for the protection relay 234 based on notifications from other IEDs and notifies the management device 250 of the set pick-up value.

[0021] The distribution line 240 is a distribution line from the low-voltage system 230 to the general consumer 241. The distribution line 240 may include a pole-mounted transformer for stepping down the voltage to the supply voltage to the consumer 241. The consumer 241 is a consumer connected to the microgrid 200. The protection relay 242 is installed between the distribution line 240 and the consumer 241. When the protection relay 242 detects a current exceeding the set pick-up value, it disconnects the consumer 241 from the microgrid 200. The IED 243 is installed near the protection relay 242 and is wired-connected to this protection relay 242. The IED 243 controls the protection relay 242 of the consumer 241. For example, based on notifications from other IEDs, the IED 243 sets the pick-up value for the protection relay 242 and notifies the management device 250 of the set pick-up value.

[0022] Upon receiving notifications from the IEDs 211, 222, 232, 235, 243, the management device 250 notifies the operator of the state of the microgrid 200, such as by displaying it on a screen. The states of the microgrid 200 notified to the operator include whether it is in the island mode or the grid-connected mode, the power supply status of each power supply source (the small-scale power generation plant 221 and the storage battery 231), and the pick-up values set for the protection relays 234, 242. Further, the management device 250 may be configured to be able to instruct the IEDs 235, 243, respectively, to set the pick-up values for the protection relays 234, 242 according to operator operations. Also, the management device 250 may be configured to be able to set the pick-up value determination table, which will be described later, for each of the IEDs 235, 243 according to operator operations.

[0023] Note that in FIG. 1, the microgrid 200 includes the high-voltage system 220 and the low-voltage system 230, but is not limited thereto. The microgrid 200 may include more than two systems or only one system. Also, the microgrid 200 includes the small-scale power generation plant 221 and the storage battery 231 as power supply sources, but is not limited thereto. The microgrid 200 may include more than two power supply sources or only one power supply source. In addition, the notifications from IEDs 211, 222, and 232 to other IEDs may be performed using any of the protocols of broadcast, multicast, and unicast, respectively.

[0024] Figure 2 is a schematic block diagram showing the configuration of IED 20 according to this embodiment. IEDs 235 and 243 have the same configuration as IED 20. IED 20 includes a communication unit 21, a protection relay control unit 22, a protection relay IF (Interface) unit 23, and a storage unit 24. The communication unit 21 communicates with other devices. For example, the communication unit 21 receives a notification indicating the open / closed state from IED 211 that detects the open / closed state of the switch 210. In addition, the communication unit 21 notifies the management device 250 of the setting value set in the protection relay to which the IED 20 is connected. The protection relay control unit 22 controls the protection relay to which the IED 20 is connected. The protection relay control unit 22 determines a setting value at least corresponding to the open / closed state indicated by the above notification with reference to the setting value determination table stored in the storage unit 24. The protection relay control unit 22 sets the determined setting value to the protection relay to which the IED 20 is connected via the protection relay IF unit 23. For example, when the switch 210 is in the open state, the protection relay control unit 22 sets a smaller setting value to the protection relay than when it is in the closed state. The storage unit 24 stores the setting value determination table described later. The protection relay IF unit 23 is a connection interface with the protection relay. Note that the protection relay control unit 22 of IED 235 controls the protection relay 234, and the protection relay control unit 22 of IED 243 controls the protection relay 242. The protection relay IF unit 23 of IED 235 is connected to the protection relay 234, and the protection relay IF unit 23 of IED 243 is connected to the protection relay 242.

[0025] Furthermore, when the switch 210 is in the open state, the protection relay control unit 22 may determine a setting value based on the supply power of the power supply source of the microgrid 200. For example, the protection relay control unit 22 may use a setting value determination table that stores the correspondence between the combination of the open / closed state of the switch 210 and the supply power of the power supply source of the microgrid 200 and the setting value to determine the setting to be set for the protection relay. When the switch 210 is in the open state, the setting value determined by the protection relay control unit 22 may be a smaller value as the supply power of the power supply source of the microgrid 200 is smaller.

[0026] For example, the communication unit 21 receives from the IED 222 a notification as to whether the small-scale power generation plant 221 is supplying power, and receives from the IED 232 a notification as to whether the storage battery 231 is supplying power. Based on these notifications, the protection relay control unit 22 may determine the supply power of the power supply source of the microgrid 200. For example, the storage unit 24 stores in advance the supply power of each power supply source of the microgrid 200, and the protection relay control unit 22 may add up the supply powers of the power supply sources notified as supplying power among them as the total supply power of the power supply sources of the microgrid 200.

[0027] Also, for example, the communication unit 21 receives from the IED 222 a notification of the magnitude of the power supplied by the small-scale power generation plant 221, and receives from the IED 232 a notification of the magnitude of the power supplied by the storage battery 231. If the storage battery 231 is in a state of storing power, the magnitude of the power supplied may be set as a negative value. Then, the protection relay control unit 22 may add up the magnitudes of the power indicated by these notifications as the magnitude of the supply power of the power supply source of the microgrid 200.

[0028] FIG. 3 is a schematic block diagram showing the configuration of the protection relay 30 according to the present embodiment. The protection relay 234 and the protection relay 242 have the same configuration as the protection relay 30. The protection relay 30 includes an IEDIF unit 31, a control unit 32, a storage unit 33, a current measurement unit 34, and a relay unit 35. The IEDIF unit 31 is a connection interface with IEDs such as IED235 and IED243. For example, the setting of the setting value to the protection relay 30 is performed via the IEDIF unit 31. The control unit 32 controls the operation of the protection relay 30. For example, the control unit 32 causes the storage unit 33 to store the set setting value. Further, when the current measured by the current measurement unit 34 exceeds the setting value, the control unit 32 regards that the fault current has been detected and turns off the relay unit 35. The current measurement unit 34 measures the current supplied to the customer. When the relay unit 35 is on, it supplies the power from the microgrid 200 to the customer, and when it is off, it disconnects the customer from the microgrid 200.

[0029] FIG. 4 is a schematic block diagram showing the configuration of the management device 250 according to the present embodiment. The management device 250 includes a communication unit 251, a control unit 252, a display unit 253, and a storage unit 254. The communication unit 251 communicates with the IEDs 211, 222, 232, 235, and 243. The control unit 252 receives notifications from the IEDs 211, 222, 232, 235, and 243 via the communication unit 251, and generates a display image representing the state of the microgrid 200 based on these notifications. Further, the control unit 252 causes the storage unit 254 to store the content notified from the IEDs 211, 222, 232, 235, and 243. By storing the notified content in the storage unit 254 in this way, the control unit 252 can grasp how the notified content has changed. The display unit 253 includes an image display means such as a liquid crystal display and an organic EL (Electro Luminescence) display, and displays the display image generated by the control unit 252 on the screen.

[0030] FIG. 5 is a table showing an example 1 of the content of the setting value determination table according to the present embodiment. Example 1 of the content is, for example, an example of the content of the setting value determination table stored in the storage unit 24 of the IED 243. In Example 1 of the content, the setting value "A1 [A]" is associated with the combination of the open / close state "closed state" of the switch 210 and the power "-" of the power supply source of the microgrid 200. Here, the power "-" indicates that it does not depend on the magnitude of the power of the power supply source of the microgrid 200. This is because when in the closed state, that is, in the grid connection mode, the fault current is large, so the influence ratio of the power supply source of the microgrid 200 on the fault current is small. Also, [A] indicates that the unit is amperes. Similarly, in Example 1 of the content, the setting value "A2 [A]" is associated with the combination of the open / close state "open state" of the switch 210 and the power "X1 [kW]" of the power supply source of the microgrid 200. Here, [kW] indicates that the unit is kilowatts.

[0031] Furthermore, in Example 1 of the content, the setting value "A3 [A]" is associated with the combination of the open / close state "open state" of the switch 210 and the power "X2 [kW]" of the power supply source of the microgrid 200, and the setting value "A4 [A]" is associated with the combination of the power "X3 [kW]" of the power supply source of the microgrid 200. Note that X1>X2>X3 and A1>A2>A3>A4. That is, the setting value in the open state (island mode) is smaller than the setting value in the closed state (grid connection mode). Also, when in the open state, the smaller the power of the power supply source, the smaller the setting value. By doing so, even if the magnitude of the fault current varies depending on the operating state of the power supply source, the protection relays 234 and 242 can detect the fault current.

[0032] Alternatively, X1 may be the sum of the power supplied by the small-scale power plant 221 and the power supplied by the storage battery 231. When the power supplied by the small-scale power plant 221 is greater than the power supplied by the storage battery 231, X2 may be the power supplied by the small-scale power plant 221, and X3 may be the power supplied by the storage battery 231. Conversely, when the power supplied by the small-scale power plant 221 is smaller than the power supplied by the storage battery 231, X2 may be the power supplied by the storage battery 231, and X3 may be the power supplied by the small-scale power plant 221.

[0033] Also, in FIG. 5, the magnitude of the power supply source associated with the setting value determination table is a specific numerical value for the setting value, but it may also be a range of numerical values. For example, the setting value determination table may associate the combination of the open / closed state "open state" and the power supply source "X1 [kW] or more" with the setting value "A2 [A]", and associate the combination of the open / closed state "open state" and the power supply source "X2 [kW] or more and less than X1 [kW]" with the setting value "A3 [A]", and associate the combination of the open / closed state "open state" and the power supply source "less than X2 [kW]" with the setting value "A4 [A]". The same applies to FIG. 6 described later.

[0034] Also, in FIG. 5, the magnitude of the power supply source associated with the setting value determination table is a specific numerical value for the setting value, but it may also be a combination of the power supply sources supplying power. For example, the setting value determination table may associate the combination of the open / closed state "open state" and the power supply source "small-scale power plant 221 and storage battery 231" with the setting value "A2 [A]", and associate the combination of the open / closed state "open state" and the power supply source "small-scale power plant 221" with the setting value "A3 [A]", and associate the combination of the open / closed state "open state" and the power supply source "storage battery 231" with the setting value "A4 [A]". The same applies to FIG. 6 described later.

[0035] FIG. 6 is a table showing an example 2 of the content of the setting value determination table according to the present embodiment. Example 2 of the content is, for example, an example of the content of the setting value determination table stored in IED235. That is, Example 2 of the content is an example of the content of the setting value determination table when the consumer 233 is receiving and supplying power at a voltage higher than that in the case of Example 1 of the content. In Example 2 of the content, the setting value "B1 [A]" is associated with the combination of the open / close state "closed state" of the switch 210 and the power "-" of the power supply source of the microgrid 200. Similarly, the setting value "B2 [A]" is associated with the combination of the open / close state "open state" of the switch 210 and the power "X1 [kW]" of the power supply source of the microgrid 200, and the setting value "B3 [A]" is associated with the combination of the open / close state "open state" of the switch 210 and the power "X2 [kW]" of the power supply source of the microgrid 200, and the setting value "B4 [A]" is associated with the combination of the open / close state "open state" of the switch 210 and the power "X3 [kW]" of the power supply source of the microgrid 200.

[0036] Note that also in Example 2 of the content, B1 > B2 > B3 > B4. That is, the setting value in the open state (island mode) is smaller than the setting value in the closed state (grid connection mode). Also, in the open state, the smaller the power of the power supply source, the smaller the setting value. Further, A1 < B1, A2 < B2, A3 < B3, A4 < B4. That is, when receiving and supplying power at a higher voltage, the setting value is larger. By doing so, even if the magnitude of the fault current differs depending on the consumer, the protection relays 234 and 242 can detect the fault current.

[0037] FIG. 7 is a flowchart for explaining the operation of the protection relay control unit 22 according to the present embodiment. Here, it will be described as the protection relay control unit 22 of the IED243 that controls the protection relay 242. In the case of the protection relay control unit 22 of the IED235 that controls the protection relay 234, replace the protection relay 242 in the following description with the protection relay 234.

[0038] First, the protection relay control unit 22 acquires the open / closed state of the switch 210 (step ST1). This open / closed state is the notification sent by the IED 211 and indicates the open / closed state received by the communication unit 21. Next, the protection relay control unit 22 determines whether the acquired open / closed state indicates a closed state (step ST2). When it is determined that the open / closed state indicates a closed state (step ST2 - Yes), the protection relay control unit 22 determines whether the open / closed state has changed (step ST3). For example, the protection relay control unit 22 may store the previously acquired open / closed state in the storage unit 24 and compare it with the currently acquired open / closed state to determine whether the open / closed state has changed.

[0039] When it is determined that the open / closed state has changed (step ST3 - Yes), the protection relay control unit 22 refers to the setting value determination table and sets the setting value for the closed state to the protection relay 242 via the protection relay IF unit 23 (step ST4), and the process of the protection relay control unit 22 returns to step ST1. In step ST3, when it is determined that the open / closed state has not changed (step ST3 - No), the process of the protection relay control unit 22 directly returns to step ST1.

[0040] Also, in step ST2, when it is determined that the open / closed state does not indicate a closed state (indicates an open state) (step ST2 - No), the protection relay control unit 22 acquires the magnitude of the power supply source of the microgrid 200 (step ST5). This magnitude of the power supply source is the notification sent by the IED 222 and the IED 232 and is the value calculated by the protection relay control unit 22 based on the notification received by the communication unit 21.

[0041] For example, when the notification sent by IED222 indicates that the small-scale power plant 221 is supplying power, and the notification sent by IED232 also indicates that the storage battery 231 is supplying power, the protection relay control unit 22 sets the sum of the power of the small-scale power plant 221 and the power of the storage battery 231 as the magnitude of the power supply source. Also, when the notification sent by IED222 indicates that the small-scale power plant 221 is supplying power, and the notification sent by IED232 indicates that the storage battery 231 is not supplying power, the protection relay control unit 22 sets the power of the small-scale power plant 221 as the magnitude of the power supply source. Note that when the notifications sent by IED222 and 232 respectively indicate the power supplied by the small-scale power plant 221 and the storage battery 231, the protection relay control unit 22 may set the sum of the power indicated by these notifications as the magnitude of the power supply source.

[0042] Next, the protection relay control unit 22 determines whether the open / closed state or the magnitude of the power supply source has changed (step ST6). Regarding the open / closed state, for example, the protection relay control unit 22 may store the previously acquired open / closed state in the storage unit 24 and compare it with the currently acquired open / closed state to determine whether the open / closed state has changed. Also, regarding the magnitude of the power supply source, for example, the protection relay control unit 22 may store the previously acquired magnitude of the power supply source in the storage unit 24 and compare it with the currently acquired magnitude of the power supply source to determine whether the magnitude of the power supply source has changed.

[0043] When it is determined that either the open / closed state or the magnitude of the power supply source has changed (step ST6 - Yes), the protection relay control unit 22 refers to the setting value determination table, sets the setting value corresponding to the magnitude of the power supply source to the protection relay 242 via the protection relay IF unit 23 (step ST7), and the process of the protection relay control unit 22 returns to step ST1. Also, in step ST6, when it is determined that neither the open / closed state nor the magnitude of the power supply source has changed (step ST6 - No), the process of the protection relay control unit 22 also returns to step ST1.

[0044] Figure 8 is a sequence diagram for explaining the operation of the microgrid 200 according to the present embodiment. When the sequence in Figure 8 starts, it is assumed that the switch 210 is in the closed state and the small power plant 221 and the storage battery 231 are not supplying power. When the small power plant 221 starts operating and supplying power, the IED 222 notifies that the small power plant 221 is supplying power (sequence S1). This notification is received by the IED 235 that controls the protection relay 234 and the IED 243 that controls the protection relay 242. Since the switch 210 is in the closed state and in the grid connection mode, the IED 235 and the IED 243 do not change the setting values for the protection relay 234 and the protection relay 242, respectively.

[0045] Next, due to some factor, when the switch 210 changes to the open state, the IED 211 notifies that the switch 210 is in the open state (sequence S2). This notification is received by the IED 232 of the storage battery 231, the IED 235 that controls the protection relay 234, and the IED 243 that controls the protection relay 242. Since the switch 210 has changed to the open state and the island mode has been entered, the IED 235 and the IED 243 set the setting values according to the power supply source of the microgrid 200 for the protection relay 234 and the protection relay 242, respectively. At this time, since only the small power plant 221 is supplying power, the IED 235 and the IED 243 set the setting values according to the power of the small power plant 221 for the protection relay 234 and the protection relay 242, respectively.

[0046] Also, upon receiving the notification of this sequence S2, IED232 controls the battery 231 to start supplying power. Further, IED232 notifies that the battery 231 is supplying power (sequence S3). This notification is received by IED235 that controls the protection relay 234 and IED243 that controls the protection relay 242. As a result, although it has not changed from the island mode, since the small power plant 221 and the battery 231 have started supplying power, IED235 and IED243 respectively set the setting values for the protection relay 234 and the protection relay 242 according to the total power of the small power plant 221 and the battery 231.

[0047] Next, when the switch 210 returns to the closed state, IED211 notifies that the switch 210 is in the closed state (sequence S4). This notification is received by IED232 of the battery 231, IED235 that controls the protection relay 234, and IED243 that controls the protection relay 242. Since the switch 210 has changed to the closed state and the grid connection mode has been entered, IED235 and IED243 respectively set the setting values for the protection relay 234 and the protection relay 242 according to the closed state.

[0048] Also, upon receiving the notification of this sequence S4, IED232 controls the battery 231 to stop supplying power. Further, IED232 notifies that the battery 231 has stopped supplying power (sequence S5). This notification is received by IED235 that controls the protection relay 234 and IED243 that controls the protection relay 242. As a result, although the magnitude of the power supply source changes, since the open / closed state remains closed, IED235 and IED243 do not change the setting values.

[0049] FIG. 9 is a schematic diagram showing an example of a display screen of the management device 250 according to the embodiment. The example of the display screen in FIG. 9 is an example of a display screen when the opening / closing state of the switch 210 changes from the closed state to the open state at 10:02 on October 21st. The management device 250 receives a notification from the IED 211 indicating that the switch 210 is in the open state, and displays "[Switch 210] Closed ⇒ Open (10 / 21 10:02)" near the icon of the IED 211. The date and time in the parentheses is the date and time when this notification was received or the date and time when the notification was issued.

[0050] In addition, the management device 250 displays information about the switch 210 whose opening / closing state has changed in this notification, the microgrid 200 connected to this switch 210, and the upper-level system 100. The management device 250 displays the area where the microgrid 200 is installed on a map. Also, the management device 250 receives a notification from the IED 235 indicating that the setting value has been set to B2, and displays "[Protection Relay 234] Setting Value: Decrease (B1 ⇒ B2) (10 / 21 10:02)" near the icon of the IED 235. Similarly, the management device 250 receives a notification from the IED 243 indicating that the setting value has been set to A2, and displays "[Protection Relay 242] Setting Value: Decrease (A1 ⇒ A2) (10 / 21 10:02)" near the icon of the IED 243.

[0051] Also, the management device 250 received a notification from the IED 222 at 11:23 on October 19th indicating that the small power plant 221 is supplying power, and displays "[Small Power Plant 221] Power Supply in Progress (10 / 19 11:23)" near the icon of the IED 222. Similarly, the management device 250 received a notification from the IED 232 at 10:02 on October 21st indicating that the storage battery 231 is supplying power, and displays "[Storage Battery 231] Power Supply in Progress (10 / 21 10:02)" near the icon of the IED 232. By displaying in this way, the operator can easily grasp the status of the microgrid 200 and each protection relay 234, 242.

[0052] In the above-described embodiment, the setting value determination table associates setting values with combinations of the open / closed state and the power supply source. However, the setting values may be associated with the open / closed state. For example, associating the setting values with the open / closed state is suitable when the power supply source of the microgrid 200 is only one, or when the change in the size of the power supply source is small or non-existent in the island mode.

[0053] The microgrid control system in the above-described embodiment includes an IED211 that detects the open / closed state of a switch that connects the microgrid 200 and the upper-level system 100, and an IED235 or IED243 that controls the protection relay 234 or protection relay 242 in the microgrid 200. The IED235 or IED243 includes a communication unit 21 that receives a notification indicating the open / closed state from the IED211, and a protection relay control unit 22 that sets a setting value corresponding at least to the open / closed state indicated by the notification in the protection relay 234 or protection relay 242. Thereby, the setting value corresponding to whether the microgrid is connected to the upper-level system is set in the protection relay 234 or protection relay 242. Therefore, even in the island mode, the protection relay 234 or protection relay 242 can detect the fault current. In addition, since the IED235 and 243 set the setting values autonomously, it is possible to easily add a similar IED to the microgrid control system.

[0054] Also, a program for realizing the functions of the IED20 in FIG. 2 may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be read into a computer system and executed to realize the IED20. Here, the "computer system" is assumed to include hardware such as an OS and peripheral devices.

[0055] In addition, the "computer-readable recording medium" refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, a DVD, etc., and a storage device such as a hard disk or an SSD built into a computer system. Further, the "computer-readable recording medium" also includes those that dynamically hold a program for a short time, such as a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line, and those that hold a program for a certain period of time, such as a volatile memory inside a computer system that serves as a server or a client in that case. Also, the above program may be for realizing a part of the functions described above, or may be capable of realizing the above functions in combination with a program already recorded in a computer system.

[0056] In addition, each functional block of the IED20 in FIG. 2 described above may be individually chipified, or may be partially or entirely integrated and chipified. Also, the method of integrating into an integrated circuit is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. Either hybrid or monolithic may be used. Part of the functions may be realized by hardware and part by software. Also, when technologies such as integration into an integrated circuit to replace LSI appear due to the progress of semiconductor technology, it is also possible to use an integrated circuit based on such technology.

[0057] As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and design changes and the like within the scope not departing from the gist of the present invention are also included.

Explanation of Reference Numerals

[0058] 10... Power transmission and distribution system 20... IED 21... Communication unit 22... Protection relay control unit 23... Protection relay IF unit 24... Storage unit 30... Protection relay 31... IEDIF unit 32…Control unit 33…Memory unit 34…Current measurement unit 35…Relay unit 100…Upper-level system 110…Power transmission system 200…Microgrid 210…Disconnector 211…IED 220…High-voltage system 221…Small-scale power plant 222…IED 230…Low-voltage system 231…Battery 232…IED 233…Customer 234…Protection relay 235…IED 240…Distribution line 241…Customer 242…Protection relay 243…IED 250…Management device 251…Communication unit 252…Control unit 253…Display unit 254…Memory unit

Claims

1. A first intelligent electronic device for detecting an open / closed state of a switch that connects a microgrid and a higher-level system, a protection relay that disconnects a customer from the microgrid when detecting an accident current, and a second intelligent electronic device including a protection relay control unit that sets a setting value corresponding to at least the open / closed state of the switch in the protection relay. It is provided with The second intelligent electronic device includes a storage unit that stores a correspondence relationship between the open / closed state, a combination of the open / closed state and the supply power of a power supply source in the microgrid, and the setting value set in the protection relay. The protection relay is a microgrid control system that detects the accident current using the setting value set by the second intelligent electronic device.

2. The microgrid control system according to claim 1, wherein the second intelligent electronic device includes a communication unit that receives a notification indicating the open / closed state from the first intelligent electronic device.

3. The microgrid control system according to claim 1 or claim 2, wherein the setting value set in the protection relay is a larger value when the open / closed state is a closed state than when the open / closed state is an open state.

4. The correspondence relationship stored in the storage unit is such that when the open / closed state is an open state, the smaller the power of the power supply source in the microgrid, the smaller the setting value. The microgrid control system according to claim 1, wherein the setting value set in the protection relay increases as the customer receives / supplies power at a higher voltage.

5. The microgrid control system according to claim 1, further comprising a management device that displays a change in the open / closed state of the switch, a change in the setting value set by the second intelligent electronic device in the protection relay, and a power supply state of a power supply source in the microgrid.

6. A method for controlling a microgrid, comprising: a step in which a first intelligent electronic device detects an open / closed state of a switch that connects the microgrid and a higher-level system. A second intelligent electronic device sets, for a protection relay in the microgrid, a correspondence relationship between the open / closed state and a combination of the supply power of a power supply source in the microgrid and a setting value, the correspondence relationship stored by the second intelligent electronic device, and the setting value corresponding at least to the open / closed state. When the protection relay detects an accident current using the setting value set by the second intelligent electronic device, the protection relay disconnects a customer from the microgrid. A control method comprising the above steps. **Claim 7** An intelligent electronic device for controlling a protection relay in a microgrid, a protection relay control unit that sets, for the protection relay, a setting value corresponding at least to an open / closed state of a switch that connects the microgrid and a higher-level system; a storage unit that stores a correspondence relationship between the open / closed state, a combination of the supply power of a power supply source in the microgrid, and the setting value set for the protection relay. An intelligent electronic device comprising the above components. **Claim 8** A program for operating a computer of an intelligent electronic device for controlling a protection relay in a microgrid as a protection relay control unit that sets, for the protection relay, a setting value corresponding at least to an open / closed state of a switch that connects the microgrid and a higher-level system and a storage unit that stores a correspondence relationship between the open / closed state, a combination of the supply power of a power supply source in the microgrid, and the setting value set for the protection relay. ​

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