Islanding operation monitoring device, islanding operation monitoring system, and islanding operation monitoring method

Abstract

To obtain an individual operation monitoring device capable of monitoring an individual operation of a distribution system by using only a passive method without using an active method simultaneously.SOLUTION: An individual operation monitoring device is applied to a distribution system 100 including a breaker 3, a distribution line 2 connected to the breaker 3, a plurality of section switches 4 dividing the distribution line 2 into a plurality of sections, and one or a plurality of distributed power supplies 6 connected to at least one section of the plurality of sections. The individual operation monitoring device monitors voltage of the distribution line 2 on a substation side and a load side in each of the section switches 4, and determines whether or not the distributed power supplies 6 operate individually based on its monitoring result.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an islanding operation monitoring device, an islanding operation monitoring system, and an islanding operation monitoring method for monitoring an islanding operation in a power distribution system. [Background technology]

[0002] In a distribution system connected to a commercial power source, if a circuit breaker installed on a distribution line is opened, the distribution line will normally be in a no-voltage state. On the other hand, if a distributed power source such as a solar power generation system is connected to the distribution line, and the distributed power source continues to operate without being disconnected from the distribution system, the distribution line, which should be at no voltage, will be charged. In this way, when a distribution system is disconnected from the commercial power source and the distribution line is charged only by the power supplied from the distributed power source, the distributed power source is said to be operating independently.

[0003] Distributed power sources connected to a power distribution system are required to have a function for detecting islanding. This function is called the "islanding detection function." There are two types of islanding detection function: active and passive. Passive methods detect islanding by detecting sudden changes in voltage phase or frequency. However, passive methods have the problem that they cannot detect islanding and the distributed power source may continue to operate. This problem occurs when the power demand of the load and the power supply by the distributed power source are balanced within a certain section of the power distribution system. When the power demand of the load and the power supply by the distributed power source are balanced, there is no sudden change in voltage phase or frequency at a level that would allow islanding to be detected. To address this problem, active methods are used in combination as a backup.

[0004] The active method aims to inject reactive power into the distribution system to disrupt the balance between the load power demand and the power supply from distributed power sources, and to cause frequency fluctuations only during isolated operation. However, the injection of reactive power has the disadvantage of causing voltage fluctuations in the distribution system. For this reason, it is considered problematic that an increase in the number of distributed power sources can cause voltage flicker.

[0005] The following Patent Document 1 discloses an islanding detection device that suppresses the occurrence of voltage flicker. In this Patent Document 1, the amount of fluctuation in the inverter output voltage is converted to ΔV10, which is a 10 Hz fluctuation value in the flicker visibility curve, and when ΔV10 exceeds a threshold, the amount of reactive power fluctuation output by the power conditioner is limited, and the positive feedback gain is effectively reduced, thereby suppressing the occurrence of voltage flicker. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2014-3743 A Summary of the Invention [Problem to be solved by the invention]

[0007] The islanding detection device described in Patent Document 1 suppresses the occurrence of voltage flicker by reducing the gain of the positive feedback of the reactive power fluctuation amount, which causes a problem of slow detection of islanding. On the other hand, if the gain of the positive feedback of the reactive power output amount is increased in order to perform islanding detection at high speed, the speed of islanding detection increases, but voltage flicker cannot be sufficiently suppressed, and the problem of reduced power quality remains.

[0008] As described above, there is a trade-off between improving the islanding detection speed and suppressing voltage flicker. In any case, these issues are caused by the use of an active method in addition to the islanding detection. For this reason, it is desirable to monitor islanding in a power distribution system using only the passive method without using an active method in addition.

[0009] The present disclosure has been made in consideration of the above, and aims to obtain an islanding operation monitoring device that can monitor the islanding operation of a power distribution system using only a passive method, without also using an active method. [Means for solving the problem]

[0010] In order to solve the above-mentioned problems and achieve the object, an islanding operation monitoring device according to the present disclosure is applied to a power distribution system including a circuit breaker, a distribution line connected to the circuit breaker, a plurality of sectional switches dividing the distribution line into a plurality of sections, and one or a plurality of distributed power sources connected to at least one of the plurality of sections. Each of the islanding operation monitoring devices is connected to a corresponding one of the plurality of sectional switches, and each monitors the islanding operation of the distributed power source in the power distribution system. The islanding operation monitoring device includes a monitoring unit that monitors the voltage of the distribution line on the substation side and the load side of each sectional switch, and a determination unit that determines whether or not the distributed power source is in islanding operation based on the monitoring result of the monitoring unit. Effect of the Invention

[0011] According to the islanding operation monitoring device according to the present disclosure, it is possible to effectively monitor the islanding operation of a power distribution system by using only the passive method without also using the active method. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram showing a schematic diagram of a power distribution system including an isolated operation monitoring device according to a first embodiment; [Diagram 2] FIG. 1 is a block diagram showing a configuration example of a control device according to a first embodiment. [Diagram 3]FIG. 1 is a block diagram showing an example of a hardware configuration for implementing the functions of a control device according to a first embodiment; [Figure 4] A flowchart showing an operation flow of the control device according to the first embodiment for detecting an isolated operation. [Diagram 5] FIG. 1 is a diagram illustrating a power distribution system including an isolated operation monitoring system according to a second embodiment. [Figure 6] FIG. 11 is a block diagram showing a configuration example of a control device according to a second embodiment. [Figure 7] A flowchart showing an operation flow of the control device according to the second embodiment for detecting an isolated operation. [Figure 8] FIG. 11 is a diagram showing a schematic diagram of a power distribution system including an isolated operation monitoring system according to a third embodiment. [Figure 9] A flowchart showing an operation flow of detecting an isolated operation by the control device according to the third embodiment. [Figure 10] FIG. 13 is a diagram for explaining a control method for eliminating isolated operation by a control device according to a fourth embodiment. [Figure 11] A flowchart showing a first control flow for eliminating isolated operation by the control device according to the fourth embodiment. [Figure 12] A flowchart showing a second control flow for eliminating isolated operation by the control device according to the fourth embodiment. [Figure 13] A flowchart showing a control flow for eliminating isolated operation by the control device according to the fifth embodiment. [Figure 14] A flowchart showing a control flow for eliminating isolated operation by the central device according to the fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An islanding operation monitoring device, an islanding operation monitoring system, and an islanding operation monitoring method according to embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0014] Embodiment 1 1 is a diagram illustrating a power distribution system including an islanding operation monitoring device according to the first embodiment. The power distribution system 100 includes a bus 12 and a circuit breaker 3 connected to the bus 12. The bus 12 and the circuit breaker 3 are installed in a substation. The power distribution system 100 also includes a power distribution line 2 connected to the circuit breaker 3, and a plurality of section switches 4 provided on the power distribution line 2.

[0015] A relay 14 is connected to the circuit breaker 3. A zero-phase-sequence transformer 18 is provided between the bus bar 12 and the relay 14. In addition, a current detector 16 is provided on the distribution line 2 side as viewed from the circuit breaker 3. The zero-phase-sequence transformer 18 measures the zero-phase-sequence voltage in the bus bar 12. The current detector 16 measures the overcurrent and zero-phase-sequence current in the distribution line 2.

[0016] The circuit breaker 3 cuts off the power supplied to the distribution line 2 when an accident such as a short circuit or a ground fault occurs in the power distribution system 100. The circuit breaker 3 is controlled by a relay 14. The relay 14 controls the interruption and reclosing of the circuit breaker 3. After the circuit breaker 3 is interrupted in the event of an accident, the relay 14 recloses the circuit breaker 3 after a reclosing time has elapsed. The relay 14 is connected to a central unit 40 via a communication path 15. The central unit 40 is a server device having a computer, a storage device, and a communication device. The central unit 40 transmits a command signal to the relay 14 to control the open / close state of the circuit breaker 3.

[0017] The sectional switch 4 is a switch having contacts that are closed by excitation of an electromagnet and opened by demagnetization. The sectional switch 4 divides the distribution line 2 into a plurality of sections. A distributed power source (DG) 6 and a load (ZL) 8 are connected to the distribution line 2. The distributed power source 6 and the load 8 shown in FIG. 1 are examples. Each of the distributed power sources 6 and the loads 8 is connected to at least one of the plurality of sections divided by the sectional switch 4.

[0018] During normal power transmission, the sectioning switch 4 is in a closed state with its contacts closed. On the other hand, if an accident occurs in the distribution line 2 and the distribution line voltage drops, the sectioning switch 4 demagnetizes and opens its contacts. This causes the sectioning switch 4 to enter an open state with its contacts open.

[0019] Each section switch 4 is provided with a control device 20. Furthermore, control transformers 24a, 24b and current detectors 22a, 22b are provided on both sides of each section switch 4. The control transformers 24a, 24b are detectors for detecting the distribution line voltage, which is the voltage on both sides of the section switch 4. The current detectors 22a, 22b are detectors for detecting the power flow on both sides of the section switch 4. In the following description, of the two sides of the section switch 4, the side on which the circuit breaker 3 is located as viewed from the section switch 4 will be referred to as the "substation side" as appropriate, and the opposite side will be referred to as the "load side" as appropriate.

[0020] The islanding operation monitoring device according to the first embodiment is realized by a control device 20 that controls the operation of the sectioning switches 4. That is, the control devices 20 are each connected to a corresponding one of the multiple sectioning switches 4, and each operate as an islanding operation monitoring device that monitors the islanding operation of the distributed power sources 6 in the power distribution system 100.

[0021] 2 is a block diagram showing an example of the configuration of the control device according to embodiment 1. The control device 20 includes a monitoring unit 201, a determining unit 202, and a control unit 203.

[0022] The monitoring unit 201 monitors the power flows on the substation side and the load side in each sectioning switch 4, and the voltages of the distribution lines on the substation side and the load side. The determination unit 202 determines whether or not the distributed power source 6 is in islanding operation based on the monitoring result of the monitoring unit 201. The control unit 203 controls the open / closed state of the sectioning switch 4 based on the determination result of the determination unit 202. The open state is a state in which the contacts of the sectioning switch 4 are open. The closed state is a state in which the contacts of the sectioning switch 4 are closed.

[0023] Fig. 3 is a block diagram showing an example of a hardware configuration for realizing the functions of the control device of embodiment 1. When part or all of the functions of the control device 20 according to embodiment 1 are realized, as shown in Fig. 3, the configuration may include a processor 300 for performing calculations, a memory 302 for storing a program read by the processor 300, and an interface 304 for inputting and outputting signals.

[0024] The processor 300 may be a calculation means such as a calculation device, a microprocessor, a microcomputer, a CPU (Central Processing Unit), or a DSP (Digital Signal Processor). Examples of the memory 302 include non-volatile or volatile semiconductor memories such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable ROM), and EEPROM (Electrically EPROM), a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, and a DVD (Digital Versatile Disc).

[0025] The memory 302 stores a program for executing the functions of the control device 20 according to the first embodiment. The processor 300 exchanges necessary information via the interface 304, executes the program stored in the memory 302, and performs required calculation processing by having the processor 300 refer to the table stored in the memory 302. A control signal required for controlling the section switch 4 is generated inside the control device 20, and is provided to the section switch 4 via the interface 304 under the control of the processor 300. Through these processes, the control of each embodiment described below is performed. The calculation results by the processor 300 can be stored in the memory 302.

[0026] Next, the operation of the control device 20 will be described. FIG. 4 is a flowchart showing an operation flow of the control device of the first embodiment for detecting an isolated operation. As a premise of the operation, it is assumed that an accident has occurred in the power distribution system 100 (step S11). When an accident occurs in the power distribution system 100, the circuit breaker 3 is opened. The control device 20 has a function of measuring the zero-phase voltage and the zero-phase current. The zero-phase voltage can be obtained using the measurement values ​​of the control transformers 24a and 24b. The zero-phase current can be obtained using the measurement values ​​of the current detectors 22a and 22b. The control device 20 can detect the presence or absence of an accident in the power distribution system 100 based on the calculated values ​​of the zero-phase voltage and the zero-phase current.

[0027] The control device 20 monitors the voltages of the distribution lines 2 on both sides of the section switch 4 (step S12). The monitoring of the voltage of the distribution line 2 is performed based on the detection results of the control transformers 24a and 24b.

[0028] The control device 20 judges whether a specified time has elapsed since starting to monitor the voltage of the power distribution line 2 (step S13). If the specified time has not elapsed (step S13, No), the process returns to step S12 and continues monitoring the voltage. If the specified time has elapsed (step S13, Yes), the process proceeds to step S14.

[0029] In step S14, if a voltage is observed on at least one side (step S14, Yes), the control device 20 determines that islanding is occurring in the section where the voltage is observed (step S15). On the other hand, if no voltage is observed on either side of the distribution line 2 (step S14, No), the control device 20 determines that islanding is not occurring in either section on either side (step S16).

[0030] When at least one of the voltages on both sides of the sectioning switch 4, i.e., on the substation side and the load side, is observed, it means that the distribution line 2 on the side where the voltage is observed is being charged with power from the distributed power source 6. Therefore, by having each control device 20 monitor the voltage on both sides of the distribution line 2 according to the flow of Fig. 4, it is possible to detect the presence or absence of islanding in the entire section of the distribution line 2.

[0031] It should be noted that the control flow in Fig. 4 does not include operations by the central unit 40. That is, the control flow in Fig. 4 does not require the exchange of information with the central unit 40, and is completed by the individual operations of the control devices 20. Therefore, according to the isolated operation monitoring device of the first embodiment, it becomes possible to quickly detect the presence or absence of isolated operation after an accident occurs.

[0032] Furthermore, when the circuit breaker 3 is opened due to an accident, a reclosing operation is then performed under the control of the central device 40. Conventionally, there have been technologies that monitor islanding during reclosing, but the islanding operation monitoring device according to embodiment 1 detects islanding before reclosing control is performed. In other words, the islanding operation monitoring device according to embodiment 1 is distinct from technologies that detect islanding in conjunction with reclosing control.

[0033] As described above, the islanding operation monitoring device according to the first embodiment is applied to a power distribution system including a plurality of sectionalizing switches that divide a power distribution line into a plurality of sections, and one or a plurality of distributed power sources connected to at least one of the plurality of sections. Each of the islanding operation monitoring devices is connected to a corresponding one of the plurality of sectionalizing switches, and each monitors the islanding operation of the distributed power source in the power distribution system. The islanding operation monitoring device monitors the voltage of the power distribution line on the substation side and the load side at each of the sectionalizing switches, and determines whether or not the distributed power source is in islanding operation based on the monitoring result. This makes it possible to detect islanding operation in the power distribution system using only the passive method without also using an active method.

[0034] Moreover, the islanding operation monitoring method according to the first embodiment is applied to a power distribution system including a plurality of sectionalizing switches that divide a power distribution line into a plurality of sections, and one or a plurality of distributed power sources connected to at least one of the plurality of sections. The control devices that implement the islanding operation monitoring method are each connected to a corresponding one of the plurality of sectionalizing switches, and each monitors the islanding operation of the distributed power source in the power distribution system. The islanding operation monitoring method includes a first step of monitoring the voltages of the power distribution lines on the substation side and the load side at each switch, and a second step of determining whether or not the distributed power source is in islanding operation based on the monitoring result in the first step. These processing steps make it possible to detect islanding in the power distribution system using only the passive method without also using an active method.

[0035] Embodiment 2 Fig. 5 is a diagram showing a schematic diagram of a power distribution system including an islanding operation monitoring system according to embodiment 2. Components of a power distribution system 100 shown in Fig. 5 are the same as or equivalent to those shown in Fig. 1. Note that the same or equivalent components are denoted by the same reference numerals, and duplicated explanations will be omitted.

[0036] 5, the control device 20 is replaced with a control device 20A as compared with the configuration shown in Fig. 1. In Fig. 5, the multiple control devices 20A configure an isolated operation monitoring system 1A according to the second embodiment.

[0037] 5, a plurality of control devices 20A are connected to each other via a communication path 41. The communication path 41 can be constructed as a wired communication path using an optical fiber cable, a metal cable, or the like. The communication path 41 may also be constructed as a wireless communication path using power line carrier or wireless communication. The connection form of the communication path 41 is arbitrary, and may be any connection form including a star type, a ring type, a double ring type, a mesh type, a cascade type, or a bus type.

[0038] Fig. 6 is a block diagram showing a configuration example of a control device according to embodiment 2. Comparing the control device 20 shown in Fig. 2 with the control device 20A shown in Fig. 6, a communication unit 204 is further provided in Fig. 6. The communication units 204 in the multiple control devices 20A exchange information with each other to share information between the multiple control devices 20A.

[0039] Next, a description will be given of the operation of the islanding operation monitoring system 1A according to the embodiment 2. Fig. 7 is a flowchart showing an operation flow of the islanding operation detection by the control device according to the embodiment 2. As a premise for the operation, it is assumed that an accident has occurred in the power distribution system 100.

[0040] The operation differs from that of the first embodiment in that the control device 20A according to the second embodiment has a fault shutdown function. In the operation of the second embodiment, when an accident occurs, the control device 20A detects the accident (step S21). When an accident is detected, the section switch 4 on the substation side closest to the fault point operates before the circuit breaker 3 operates, and the contacts of the section switch 4 are opened. This operation is called "high-speed shutdown."

[0041] Like the control device 20 of the first embodiment, the control device 20A of the second embodiment has a function of measuring a zero-phase voltage and a zero-phase current. When a ground fault occurs in the power distribution system 100, the control device 20A can detect the ground fault by the zero-phase current and detect the direction of the ground fault by the zero-phase voltage. In addition, each control device 20A can recognize that it is located on the substation side closest to the fault point by sharing the determination result of the ground fault direction. Hereinafter, the section switch 4 located on the substation side closest to the fault point is called the "first section switch". In addition, the control device 20A that controls the operation of the first section switch is called the "control device of the first section switch".

[0042] The control device of the first section switch monitors the voltage on the load side in the first section switch (step S22). The monitoring of the voltage on the load side is performed based on the detection result of the control transformer 24b.

[0043] The control device of the first section switch judges whether or not a specified time has elapsed since starting to monitor the voltage on the load side (step S23). If the specified time has not elapsed (step S23, No), the process returns to step S22 and continues monitoring the voltage. If the specified time has elapsed (step S23, Yes), the process proceeds to step S24.

[0044] If the load side voltage is observed in the first section switch (step S24, Yes), the control device of the first section switch determines that islanding is occurring in the section on the load side (step S25). On the other hand, if the load side voltage is not observed (step S24, No), the control device of the first section switch determines that islanding is not occurring in the section on the load side (step S26).

[0045] The result of the determination by the controller of the first section switch as to whether or not an isolated operation is occurring is shared between the controllers 20A.

[0046] When a voltage is observed on the load side of the first sectioning switch while the first sectioning switch is open, it means that the distribution line 2 on the load side of the first sectioning switch is being charged with power from the distributed power source 6. Therefore, by having the control device of the first sectioning switch monitor the voltage on the load side of the first sectioning switch according to the flow of Fig. 7, it is possible to detect the presence or absence of islanding operation in the section on the load side of the first sectioning switch.

[0047] It should be noted that the control flow in Fig. 7 does not include operations by the central unit 40. That is, the control flow in Fig. 7 does not require the exchange of information with the central unit 40, and is completed by the operation of the control device of the first section switch. Therefore, according to the isolated operation monitoring system 1A of the second embodiment, it is possible to quickly detect the presence or absence of isolated operation after an accident occurs.

[0048] In addition, each of the control devices 20A constituting the isolated operation monitoring system 1A according to the second embodiment has a fault cutoff function, so that the location of the fault can be found early. As a result, compared to the first embodiment, the detection control of the isolated operation can be performed more quickly, so that the isolated operation can be detected early.

[0049] Furthermore, when the circuit breaker 3 and the section switch 4 are opened due to an accident, a reclosing operation is then performed under the control of the central device 40. Conventionally, there have been technologies that monitor islanding operation during reclosing, but the islanding operation monitoring system 1A according to embodiment 2 detects islanding operation before reclosing control is performed. In other words, the islanding operation monitoring system 1A according to embodiment 2 is distinct from technologies that detect islanding operation in conjunction with reclosing control.

[0050] As described above, the islanding operation monitoring system according to the second embodiment is applied to a power distribution system including a plurality of sectional switches that divide a power distribution line into a plurality of sections, and one or a plurality of distributed power sources connected to at least one of the plurality of sections. A plurality of control devices constituting the islanding operation monitoring system are each connected to a corresponding one of the plurality of sectional switches, and each monitors the islanding operation of the distributed power source in the power distribution system. When an accident occurs in the power distribution system, the control device that controls the operation of the first sectional switch, which is the sectional switch located on the substation side closest to the accident point, monitors the voltage on the load side of the first sectional switch, and determines whether or not the distributed power source in the section on the load side of the first sectional switch is in islanding operation based on the monitoring result. This makes it possible to detect islanding in the power distribution system using only the passive method without also using the active method.

[0051] Embodiment 3 Fig. 8 is a diagram showing a schematic diagram of a power distribution system including an islanding operation monitoring system according to embodiment 3. The components of the power distribution system 100 shown in Fig. 8 are the same as or equivalent to those shown in Fig. 5. Note that the same or equivalent components are denoted by the same reference numerals, and duplicated explanations will be omitted.

[0052] 8, in comparison with the configuration shown in Fig. 5, the multiple control devices 20A are connected to each other and between the central device 40 and the multiple control devices 20A by communication paths 42. In Fig. 8, the central device 40 and the multiple control devices 20A configure an isolated operation monitoring system 1B according to the third embodiment.

[0053] 8, the communication path 42 can be constructed as a wired communication path using an optical fiber cable, a metal cable, or the like. The communication path 42 may also be constructed as a wireless communication path using power line carrier or wireless communication. The connection form of the communication path 42 is arbitrary, and may be any connection form including a star type, a ring type, a double ring type, a mesh type, a cascade type, and a bus type.

[0054] Next, an operation of the islanding operation monitoring system 1B according to the third embodiment will be described. Fig. 9 is a flowchart showing an operation flow of the islanding operation detection by the control device of the third embodiment. As a premise of the operation, it is assumed that an accident has occurred in the power distribution system 100 (step S31). When an accident occurs in the power distribution system 100, the circuit breaker 3 is opened.

[0055] Each control device 20A receives operation information of the circuit breaker 3 from the central device 40 (step S32). This allows the control device 20A to obtain information that the circuit breaker 3 has been operated at an early stage.

[0056] In FIG. 9, the operations in steps S12 to S16 are the same as those in the first embodiment, and therefore a duplicated description will be omitted.

[0057] When at least one of the voltages on both sides of the sectioning switch 4, i.e., on the substation side and the load side, is observed, it means that the distribution line 2 on the side where the voltage is observed is being charged with power from the distributed power source 6. Therefore, by having each control device 20A monitor the voltages on both sides of the distribution line 2 according to the flow of Fig. 9, it is possible to detect the presence or absence of islanding in the entire section of the distribution line 2.

[0058] It should be noted that the control flow of steps S12 to S16 in Fig. 9 does not include operations by the central unit 40. That is, the control flow of steps S12 to S16 in Fig. 9 does not require the exchange of information with the central unit 40, and is completed by individual operations of the control device 20A. Therefore, according to the isolated operation monitoring system 1B of embodiment 3, it is possible to quickly detect the presence or absence of isolated operation after an accident occurs.

[0059] Moreover, according to the islanding operation monitoring system 1B according to the third embodiment, the operation information of the circuit breaker 3 is directly received from the central device 40, so that the occurrence of an accident can be grasped promptly. As a result, compared to the first embodiment, the detection control of the islanding operation can be performed promptly, so that the islanding operation can be detected early.

[0060] Furthermore, when the circuit breaker 3 and the section switch 4 are opened due to an accident, a reclosing operation is then performed under the control of the central device 40. Conventionally, there have been technologies that monitor islanding operation during reclosing, but the islanding operation monitoring system 1B according to embodiment 3 detects islanding operation before reclosing control is performed. In other words, the islanding operation monitoring system 1B according to embodiment 3 is distinct from technologies that detect islanding operation in conjunction with reclosing control.

[0061] As described above, the islanding monitoring system according to the third embodiment is applied to a power distribution system including a plurality of section switches that divide a power distribution line into a plurality of sections, and one or a plurality of distributed power sources connected to at least one of the plurality of sections. A plurality of control devices and a central device connected to the plurality of control devices via a communication path constitute the islanding monitoring system. Each of the plurality of control devices is connected to a corresponding one of the plurality of section switches, and each of the control devices monitors the islanding operation of the distributed power source in the power distribution system. Each of the control devices receives circuit breaker operation information from the central device, and monitors the voltage of the distribution line on the substation side and the load side of each section switch, and determines whether or not the distributed power source is in islanding operation based on the monitoring result. This makes it possible to detect islanding in the power distribution system using only the passive method without also using the active method.

[0062] Embodiment 4 In the first to third embodiments, a control method for detecting whether or not a distributed power source is in islanding operation has been described. In the fourth embodiment, a control method for eliminating islanding operation after detecting islanding operation will be described. Note that the control method according to the fourth embodiment, like the first embodiment, aims to eliminate islanding operation by individual operation of each control device 20.

[0063] Fig. 10 is a diagram for explaining a control method for eliminating an islanding operation by the control device of embodiment 4. In Fig. 10, in order to distinguish between the individual sectional switches 4, dispersed power sources 6, and loads 8, the sectional switches 4 are given the subscripts a, b, and c, and the dispersed power sources 6 and loads 8 are given the subscripts a and b.

[0064] The upper part of Fig. 10 shows that islanding continues in the section indicated by the dashed frame A1. As mentioned above, if the load power demand and the power supply from the distributed power source are balanced, the islanding detection function does not work well, and there is a risk that islanding continues. To resolve this balanced state, it is necessary to disrupt the balance between the power demand and the power supply. Therefore, when the tidal flow, which is the magnitude of the current flow, is equal to or greater than a threshold in the sectional switch 4, the sectional switch 4 is opened. In the example shown in the middle part of Fig. 10, the tidal flow in each of the sectional switches 4a, 4b, and 4c is equal to or greater than the threshold, and the sectional switches 4a, 4b, and 4c are controlled to the open state.

[0065] In reality, it is believed that islanding will be resolved by opening the sectional switch 4 where a power flow rate equal to or greater than the threshold is observed. On the other hand, it is also necessary to consider the possibility that islanding will not be resolved by chance. In the example shown in the middle part of Figure 10, it is shown that islanding continues in the section of sectional switches 4a and 4b indicated by dashed frame A2, even though sectional switches 4a, 4b, and 4c in the section where islanding continues have been opened.

[0066] In the section indicated by box A2, voltage is observed on the load side of the sectional switch 4a and on the substation side of the sectional switch 4b. Of these sectional switches 4a and 4b, the sectional switch 4b where the voltage on at least one of the substation side and the load side is observed is closed. The state at this point is shown in the lower part of Figure 10. Closing the sectional switch 4b changes the load connection state, so that the balanced state can be reliably broken. This makes it possible to reliably eliminate islanding operation.

[0067] The above-mentioned control flows are shown in Fig. 11 and Fig. 12. Fig. 11 is a flowchart showing a first control flow for eliminating islanding operation by the control device of embodiment 4. Fig. 12 is a flowchart showing a second control flow for eliminating islanding operation by the control device of embodiment 4.

[0068] First, a description will be given of the flowchart in Fig. 11. The flowchart in Fig. 11 is executed by each of the control devices 20.

[0069] The control flow in FIG. 11 starts with detecting an islanding operation (step S41). The processing in step S41 corresponds to the entire flow chart in FIG. 4, FIG. 7 or FIG. 9, and any of these processes is used. Next, the control device 20 monitors the power flow on both sides of the section switch 4 (step S42). The control device 20 compares the power flow amount, which is the magnitude of the power flow, with a threshold (step S43). If the power flow amount is equal to or greater than the threshold (step S44, Yes), the control device 20 opens the section switch 4 and controls it to the open state (step S45). On the other hand, if the power flow amount is less than the threshold (step S44, No), the control flow in FIG. 11 ends.

[0070] Next, a description will be given of the flowchart of Fig. 12. The processing of the flowchart of Fig. 12 is also performed by each control device 20. Note that the processing from steps S41 to S45 is the same as that of Fig. 11, and a description of the overlapping contents will be omitted.

[0071] After the process in step S45, that is, after the section switch 4 is opened, it is determined whether the specified time has elapsed (step S46). If the specified time has not elapsed (step S46, No), the process waits until the specified time has elapsed. If the specified time has elapsed (step S46, Yes), the process proceeds to step S47.

[0072] In step S47, if a voltage is observed on at least one of the substation side and the load side of the section switch 4 (step S47, Yes), the control device 20 closes the section switch 4 in which the voltage is observed (step S48). On the other hand, if the voltage is not observed (step S47, No), the control flow in FIG. 12 ends.

[0073] 11 and 12, the process of step S42 is performed by the monitoring unit 201. The determination processes of steps S44, S46, and S47 are performed by the determination unit 202. The processes of steps S45 and S48 are performed by the control unit 203.

[0074] 11 and 12, when the tidal flow amount is equal to the threshold value, the result is determined as "Yes", but the result may be determined as "No". In other words, when the tidal flow amount is equal to the threshold value, the result may be determined as either "Yes" or "No".

[0075] The control flows in Figures 11 and 12 do not include operations by the central unit 40. That is, the control flows in Figures 11 and 12 do not require the exchange of information with the central unit 40, and are completed by the individual operations of the control devices 20. For this reason, by using the control method according to the fourth embodiment, it is possible to quickly resolve an islanding operation after it is detected.

[0076] As described above, when the islanding operation of a distributed power source is detected while the sectional switch is in the closed state, the islanding operation monitoring device according to the fourth embodiment monitors the power flow on both sides of the sectional switch, and when it is determined that the power flow rate, which is the magnitude of the power flow, is equal to or greater than a threshold, controls the sectional switch that is controlled to the closed state to the open state. By opening the sectional switch where the power flow rate equal to or greater than the threshold is observed, the balance between the power demand and the power supply can be disrupted. This makes it possible to effectively utilize the passive islanding operation detection function provided in the islanding operation monitoring device, and to quickly resolve the islanding operation.

[0077] Furthermore, the islanding operation monitoring device according to the fourth embodiment may be configured to control a section switch that has been controlled to an open state to a closed state when a voltage on at least one side is observed after a specified time has elapsed in a section switch that has been controlled to an open state from a closed state. This control makes it possible to disrupt the balance between the amount of power demand and the amount of power supply even if the islanding operation is not resolved by chance. This makes it possible to reliably resolve the islanding operation.

[0078] Furthermore, the islanding operation monitoring method according to the fourth embodiment may include the following processing of the third and fourth steps when islanding of a distributed power source is detected by the second step in the islanding operation monitoring method according to the first embodiment. In the third step, the power flow on both sides of the sectional switch in the closed state is monitored. In the fourth step, when it is determined by the third step that the power flow rate, which is the magnitude of the power flow, is equal to or greater than a threshold, the sectional switch that has been controlled to the closed state is controlled to the open state. This control can disrupt the balance between the power demand and the power supply. This makes it possible to effectively utilize the passive islanding operation detection function provided in the islanding operation monitoring device, and to quickly resolve the islanding operation.

[0079] Moreover, the islanding operation monitoring method according to the fourth embodiment may further include a fifth step of controlling a sectional switch to a closed state when a voltage on at least one substation side is observed after a specified time has elapsed in the sectional switch that has been controlled from a closed state to an open state. This control makes it possible to disrupt the balance between the power demand and the power supply even if the islanding operation is not resolved by chance. This makes it possible to reliably resolve the islanding operation.

[0080] Embodiment 5. Next, a control method for eliminating the islanding operation after the islanding operation is detected will be described in the fifth embodiment. Note that the control method in the fifth embodiment is such that each control device 20 and the central device 40 cooperate with each other to eliminate the islanding operation.

[0081] Fig. 13 is a flowchart showing a control flow for eliminating an islanding operation by the control device according to embodiment 5. Fig. 14 is a flowchart showing a control flow for eliminating an islanding operation by the central device according to embodiment 5.

[0082] First, a description will be given of the flowchart in Fig. 13. The processing of the flowchart in Fig. 13 is carried out by each control device 20. Note that the processing from steps S41 to S46 is the same as in Fig. 12, and a description of the overlapping contents will be omitted.

[0083] After the process in step S46, i.e., after the section switch 4 is opened, if a specified time has elapsed, the process proceeds to step S51. In step S51, if a voltage is observed on at least one of the substation side and the load side of the section switch 4 (step S51, Yes), the control device 20 notifies the central device 40 of voltage observation information to that effect (step S52). On the other hand, if a voltage is not observed on either the substation side or the load side (step S51, No), the control flow in FIG. 13 ends.

[0084] Proceeding to the flowchart of FIG. 14, the central unit 40 receives voltage observation information from the control device 20 (step S61). The central unit 40 selects the sectional switch 4 to be closed based on the voltage observation information notified from the control device 20 (step S62). The central unit 40 transmits a closing command for the sectional switch 4 selected in step S62 to the corresponding control device 20 (step S63). The central unit 40 checks the charging state of the power distribution line 2 through communication with the control device 20 that transmitted the closing command (step S64). If the charging state of the power distribution line 2 continues (step S65, Yes), it is determined that the islanding operation has not been resolved, and the process from step S62 is repeated. On the other hand, if the charging state of the power distribution line 2 does not continue (step S65, No), the control flow of FIG. 14 is terminated.

[0085] In step S64 of FIG. 14, communication is performed with the control device 20 to check the charging state of the power distribution line 2. If there is no response from the control device 20 within a specified time, it may be determined that the isolated operation has been resolved.

[0086] In the islanding operation monitoring system according to the fifth embodiment, the central unit 40 selects the sectional switch 4 to be closed based on voltage observation information notified from one or more control devices 20. Generally, the calculation capacity of the central unit 40 is greater than that of the control devices 20. Therefore, compared to the fourth embodiment in which each control device 20 individually closes the sectional switch 4, it becomes possible to select a sectional switch 4 that is more suitable for eliminating the islanding operation.

[0087] As described above, in the islanding operation monitoring system according to the fifth embodiment, when islanding of a distributed power source is detected while the sectional switches are in the closed state, each control device monitors the power flow on both sides of the sectional switch, and when it is determined that the power flow rate, which is the magnitude of the power flow, is equal to or greater than a threshold, controls the corresponding sectional switch to the open state. By opening a sectional switch where a power flow rate equal to or greater than the threshold is observed, the balance between the power demand and the power supply can be disrupted. This makes it possible to effectively utilize the passive islanding operation detection function provided in the islanding operation monitoring device, and to quickly resolve the islanding operation.

[0088] In addition, in the islanding operation monitoring system according to the fifth embodiment, when at least one side voltage is observed after a specified time has elapsed in a sectional switch controlled from a closed state to an open state, the control unit notifies the central unit of the voltage observation information. The central unit selects a sectional switch to be closed based on the voltage observation information notified from the control unit. The central unit also transmits a closing command for the selected sectional switch to the corresponding control unit, and checks the charging state of the distribution line through communication with the control unit that transmitted the closing command. Furthermore, if the charging state of the distribution line continues, the central unit repeats the process of selecting the sectional switch to be closed. According to these controls, even if the islanding operation is not resolved by chance, it is possible to disrupt the balance between the power demand and the power supply. This makes it possible to reliably resolve the islanding operation.

[0089] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or the embodiments may be combined with each other. Also, parts of the configurations may be omitted or modified without departing from the spirit of the invention. [Explanation of symbols]

[0090] 1A, 1B isolated operation monitoring system, 2 distribution line, 3 circuit breaker, 4, 4a, 4b, 4c sectional switches, 6, 6a, 6b distributed power sources, 8, 8a, 8b loads, 12 busbar, 14 relay, 15, 41, 42 communication path, 16, 22a, 22b current detector, 18 zero-phase transformer, 20, 20A control device, 24a, 24b control transformer, 40 central device, 100 distribution system, 201 monitoring unit, 202 judgment unit, 203 control unit, 204 communication unit, 300 processor, 302 memory, 304 interface.

Claims

1. An islanding operation monitoring device applied to a power distribution system including a circuit breaker, a distribution line connected to the circuit breaker, a plurality of sectional switches dividing the distribution line into a plurality of sections, and one or a plurality of distributed power sources connected to at least one of the plurality of sections, each of which is connected to a corresponding one of the plurality of sectional switches, and each of which monitors the islanding operation of the distributed power sources in the power distribution system, a monitoring unit that monitors the voltages of the distribution lines on the substation side and the load side in each of the section switches; a determination unit that determines whether the distributed power source is in islanding operation based on a monitoring result of the monitoring unit; a control unit that controls the opening and closing state of the section switch based on a determination result of the determination unit; Equipped with When the section switch is in a closed state and an isolated operation of the distributed power source is detected, The monitoring unit monitors power flows on both sides of the section switch, When the determination unit determines that the power flow amount, which is the magnitude of the power flow, is equal to or greater than a threshold value, The control unit controls the section switch, which is controlled to the closed state, to an open state. An isolated operation monitoring device characterized by the above.

2. When the voltage on at least one side is observed in the monitoring result by the monitoring unit, The determination unit determines that an islanding operation is being performed in the section where the voltage is observed.

2. The isolated operation monitoring device according to claim 1 .

3. In the section switch controlled from the closed state to the open state, if a voltage on at least one side is observed after a specified time has elapsed, The control unit controls the section switch, which is controlled to the open state, to a closed state.

3. The isolated operation monitoring device according to claim 1 or 2.

4. An islanding operation monitoring system is applied to a power distribution system including a circuit breaker, a distribution line connected to the circuit breaker, a plurality of section switches dividing the distribution line into a plurality of sections, and one or a plurality of distributed power sources connected to at least one of the plurality of sections, the system comprising a plurality of control devices each connected to a corresponding one of the plurality of section switches and each monitoring islanding operation of the distributed power sources in the power distribution system, and a central device connected to the plurality of control devices by communication paths, each of the control devices receives operation information of the circuit breakers from the central device, monitors voltages of the distribution lines on the substation side and the load side at each of the section switches, and determines whether or not the distributed power source is in isolated operation based on the monitoring results; When the section switch is in a closed state and an isolated operation of the distributed power source is detected, Each of the control devices monitors the power flow on both sides of the section switch, and when it is determined that the power flow amount, which is the magnitude of the power flow, is equal to or greater than a threshold, controls the corresponding section switch to an open state. An isolated operation monitoring system characterized by:

5. In the section switch that has been controlled from a closed state to an open state, when a voltage on at least one side is observed after a specified time has elapsed, the control device notifies the central device of voltage observation information; The central device selects a sectional switch to be closed based on the voltage observation information notified from the control device.

5. The isolated operation monitoring system according to claim 4.

6. The central device transmits a closing command for the selected sectional switch to the corresponding control device, and checks the charging state of the distribution line through communication with the control device that transmitted the closing command. If the charging state of the distribution line continues, the central device repeats the process of selecting the sectional switch to be closed.

6. The isolated operation monitoring system according to claim 5 .

7. 1. An islanding operation monitoring method applied to a power distribution system including a circuit breaker, a distribution line connected to the circuit breaker, a plurality of sectional switches dividing the distribution line into a plurality of sections, and one or a plurality of distributed power sources connected to at least one of the plurality of sections, each of which is connected to a corresponding one of the plurality of sectional switches, and each of which monitors the islanding operation of the distributed power sources in the power distribution system, the method comprising: A first step of monitoring a voltage of the distribution line on a substation side and a load side at each of the section switches; a second step of determining whether or not the distributed power source is in islanded operation based on a monitoring result obtained in the first step; a third step of monitoring power flows on both sides of the section switch when the section switch is in a closed state and an islanding operation of the distributed power source is detected by the second step; a fourth step of controlling the section switch, which has been controlled to the closed state, to an open state when it is determined that the power flow amount, which is the magnitude of the power flow, is equal to or greater than a threshold value; An islanding operation monitoring method comprising:

8. The method further includes a fifth step of controlling the sectional switch controlled to the open state from the closed state by the fourth step to the closed state when a voltage on at least one side is observed after a specified time has elapsed. The method for monitoring an isolated operation according to claim 7.

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