JP6349461B2 - Digital protection control device and power system protection method - Google Patents

Description

  The present invention relates to a digital protection control device and a power system protection method used for protecting a power system, for example, used for a redundant communication path.

  Conventionally, a plurality of digital protection control devices (hereinafter also abbreviated as “devices”) are connected via a network, and data obtained by digitally converting the current values measured from the power system by each device is communicated with other devices via a communication path. There are communication systems capable of transmitting and receiving. In this communication system, in order to protect the power system, each device detects a system fault in a protection section provided in the power system from a difference current obtained from data transmitted / received to / from other devices, and performs current elimination A method of protection was used.

  In the current differential protection method, for example, transmission methods such as PDH (Plesiochronous Digital Hierarchy) and SDH (Synchronous Digital Hierarchy) are often used. PDH and SDH are dedicated synchronous communication networks with a communication speed of 54 kbps or 1.5 Mbps, and are systems for performing cyclic communication of data at a predetermined cycle.

  Cyclic communication is characterized in that data is transmitted in a predetermined order within a certain time, so that data continuity and simultaneity are maintained. However, the communication network used in PDH and SDH consists of dedicated special equipment, and the production amount of equipment necessary for the construction of the communication network is extremely small compared to general-purpose products. There was concern about the increase.

  Therefore, it has been studied to use a communication network (hereinafter also referred to as “general-purpose network” or “communication path”) using Ethernet (registered trademark) as a medium for the communication system. In general-purpose networks, high-speed and large-capacity and cost reduction are progressing, and it is expected that a technical and cost gap with a dedicated communication network will widen. For this reason, a technique for performing communication using a general-purpose network has been proposed even in an apparatus that is mission-critical for stable operation of a power system. For example, Patent Document 1 discloses a technique for ensuring the simultaneity of relay operation between analog data sent from another station and analog data captured by the own station in a general-purpose network that is not redundant. Yes.

  However, since such a device needs to continue the protection function even if a single abnormality occurs in the communication path, it is necessary to improve the reliability of communication performed using a general-purpose network. As a redundant communication technique for improving the reliability of communication using a general-purpose network, there are HSR (High-availability Seamless Redundancy) and PRP (Parallel Redundancy Protocol).

Here, HSR and PRP will be described with reference to FIGS.
FIG. 1 is a configuration diagram illustrating an example of an HSR network topology.
The HSR is a network topology in which all the digital protection control devices 100 (in the drawing, described as devices A to D) are connected in a ring shape, and is configured as a communication path N10. In the description of FIG. 1, the digital protection control device 100 connected to the communication path N10 is abbreviated as device A to device D.

  When transmitting a frame from the device B to the device D, a clockwise frame F11 and a counterclockwise frame F12 having the same contents are transmitted from the two ports 101 and 102 mounted on the device B to each loop. Since the received clockwise frame F11 is not addressed to itself, the device A transfers the clockwise frame F11 to the adjacent device D. In addition, since the received counterclockwise frame F12 is not addressed to the own apparatus, the apparatus C transfers the counterclockwise frame F12 to the adjacent apparatus D.

  When the network is healthy, the device D that is the destination of the frame receives the clockwise frame F11 and the counterclockwise frame F12 having the same contents in duplicate. If a communication error occurs between the devices A and D, the device D cannot receive the clockwise frame F11 from the device A, but can receive the counterclockwise frame F12 from the device C. Reliability is improved at the time of a single abnormality.

  In addition, HSR has a specification in which a first-arrival frame is used and a later-arrival frame is discarded among frames received by a receiving apparatus (for example, apparatus D) clockwise and counterclockwise. According to this specification, since the receiving apparatus processes only the first-arrived frame, there is a feature that the frame processing performed by the receiving apparatus is halved as compared with the full duplex communication system. In addition, in the HSR, the clockwise frame and the counterclockwise frame do not go around the ring and reach the receiving device that is the destination in a half cycle, and thus the network traffic is also halved.

  In order for the receiving apparatus to determine whether the frame arrives first or later, it is necessary to associate which of the frames received from the clockwise direction and the counterclockwise direction is the same. For this reason, the receiving apparatus treats a frame whose transmission source MAC (Media Access Control) address and the sequence number included in the frame match as the same frame, and uses it for the determination of the first arrival or the second arrival.

FIG. 2 is a configuration diagram illustrating an example of a PRP network topology.
PRP is a network topology in which each device is connected by two communication systems of physically separated A-system network and B-system network (hereinafter also abbreviated as “A-system” and “B-system”). It is configured as a path N20. In the description of FIG. 2, the digital protection control device 100 connected to the communication path N20 is abbreviated as device A to device D. Between the devices A to C and the device D, an L2 switch 110 constituting the A system and an L2 switch 111 constituting the B system are provided. The L2 switch 110 transfers a frame to the A system, and the L2 switch 111 transfers the frame to the B system. For example, when transmitting a frame from the device B to the device D, the device B transmits an A-system frame F21 from the port 101 toward the A-system, and transmits a B-system frame F22 from the port 102 toward the B-system. The A system frame F21 and the B system frame F22 have the same contents. When the network is healthy, the A-system frame F21 is transferred to the apparatus D by the L2 switch 110, and the B-system frame F22 is transferred to the apparatus D by the L2 switch 111. Then, the device D that is the destination of each frame receives the A-system frame F21 and the B-system frame F22 in duplicate. If a communication abnormality occurs in the A system, the device D cannot receive the A system frame F21, but can receive the B system frame F22. Therefore, the reliability is improved when the communication path has a single abnormality.

  In addition, PRP is a specification that uses first-arrival frames in A-system and B-system, and discards later-arrival frames in the same way as HSR. Since the receiving device processes only the first-arrival frame, compared with a full-duplex communication system. The frame processing of the receiving device is halved. For the first-arrival or late-arrival determination, similar to the HSR, frames whose transmission source MAC address matches the sequence number included in the frame are treated as the same frame.

Japanese Patent No. 5592849

  It is possible to improve the reliability of communication using a general-purpose network by constructing a current differential system protection system on the redundant communication path as described above. However, in the protection operation by the current differential method, it is essential that the current data of all the devices sampled at the same time are prepared and the continuity of the data is maintained. However, unlike conventional cyclic communication, communication using a general-purpose network does not guarantee data simultaneity and continuity. For this reason, if a large amount of data is transmitted to the general-purpose network, the receiving device may not be able to receive all the data within a certain time due to a communication delay caused by frame retention in the L2 switch. It could take some time to detect and remove the accident.

  The technique disclosed in Patent Document 1 does not consider the variation in the transmission delay time, and is difficult to apply to a general-purpose network in which the variation in the transmission delay time is assumed.

The digital protection control device according to the present invention includes a memory, a redundant communication control unit, a communication delay time calculation unit, and a protection processing unit.
In the memory, communication frames including data used for power system protection are buffered.
The redundant communication control unit transmits a communication frame to another digital protection control device connected via a plurality of redundant communication channels, and communication transmitted from the other digital protection control device to the communication channel. Of the frames, the first communication frame is buffered in the memory, and the last communication frame is discarded.
The communication delay time calculation unit calculates the communication delay time of the communication path, and notifies the protection processing unit of the number of delay samples for which data continuity and simultaneity are guaranteed.
The protection processing unit performs an operation for protection of the power system using the communication frame when the communication frame is received within the number of delay samples by the redundant communication control unit, and sets the circuit breaker connected to the power system. Control and protect the power system.

According to the present invention, it is possible to guarantee continuity and simultaneity of data by buffering a communication frame received by a redundant communication control unit in a memory regardless of a transmission delay time of a network, Since the protection processing unit controls the circuit breaker connected to the power system when a system fault occurs, the power system can be reliably protected.
Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

It is a block diagram which shows an example of the network topology of HSR. It is a block diagram which shows an example of the network topology of PRP. It is a block diagram which shows the example of an internal structure of the digital protection control apparatus which concerns on the 1st Example of this invention. It is a block diagram which shows an example of the network topology of HSR which concerns on the 1st Example of this invention. FIG. 4A shows an example in which no abnormality has occurred in the communication path, and FIG. 4B shows an example in which an abnormality has occurred between apparatuses AB. 6 is a time chart of a frame when an abnormality occurs in the communication path according to the first exemplary embodiment of the present invention and a frame reception delay occurs. It is explanatory drawing which shows the example of the frame buffered by the electric current data frame buffer of the apparatus B which concerns on the 1st Example of this invention. 6A is a sample counter “0”, FIG. 6B is a sample counter “1”, FIG. 6C is a sample counter “2”, FIG. 6D is a sample counter “3”, and FIG. 6E is a buffered frame in the sample counter “4”. An example of It is a time chart of a frame when abnormality of the communication channel concerning the 1st example of an embodiment of the present invention is recovered. It is explanatory drawing which shows the example of the frame buffered by the electric current data frame buffer of the apparatus B which concerns on the 1st Example of this invention. 8A shows an example of buffered frames in the sample counter “2”, FIG. 8B shows a sample counter “3”, and FIG. 8C shows a buffered frame in the sample counter “4”. It is explanatory drawing which shows the example of communication delay time with the apparatuses B, C, and D which the apparatus A which concerns on the 1st Example of this invention calculated. It is a block diagram which shows the example of an internal structure of the digital protection control apparatus which concerns on the 2nd Example of this invention. It is a flowchart which shows the example of the execution procedure of PTP in the network which is not made redundant based on the 2nd Example of this invention. FIG. 12 is a sequence diagram showing an example of message notification performed between the master station and the slave station by the PTP End To End-Delay Measurement method in the process of FIG. 11. It is a flowchart which shows an example of the execution procedure of the time synchronization which the digital protection control apparatus connected to the network of PRP based on the 2nd Example of this invention performs. It is a flowchart which shows an example of the calculation process of the path | route delay based on the 2nd Example of this invention. FIG. 15 is a sequence diagram illustrating an example of message notification performed between a slave station and an adjacent end by the PTP Peer To Peer-Delay Measurement method in the process of FIG. 14. It is a flowchart which shows an example of the calculation process of the time difference which concerns on the 2nd Example of this invention. FIG. 17 is a sequence diagram showing an example of message notification performed between the master station and the slave station by the PTP Peer To Peer-Delay Measurement method in the process of FIG.

[1. First Embodiment]
The digital protection control apparatus according to the first embodiment of the present invention will be described below. In the present specification and drawings, components having substantially the same function or configuration are denoted by the same reference numerals, and redundant description is omitted.

<Internal configuration example of digital protection control device>
FIG. 3 is a block diagram showing an example of the internal configuration of the digital protection control device 10. In the following description, the digital protection control device 10 shown in FIG. 3 is also referred to as “own device”, and the other digital protection control device 10 connected to the own device via a communication path as shown in FIG. Also called.

  The digital protection control device 10 includes a main control unit 1, a main storage memory 2, an I / O control unit 3, an input converter 4, an analog input unit 5, a redundant communication control unit 6, a display unit 7, an operation unit 8, A ROM 9 is provided, and each unit is connected to each other by a system bus B1. Then, the digital protection control device 10 transmits a current data frame (an example of a communication frame) to another device connected via a plurality of redundant communication channels, and the current data transmitted to the communication channel by the other device. Receive a frame.

  The main control unit 1 is constituted by, for example, a CPU (Central Processing Unit), and controls the operation of each unit in the digital protection control device 10. The main control unit 1 includes a communication delay time calculation unit 11 and a protection processing unit 12.

The communication delay time calculation unit 11 calculates the communication delay time of the communication path in advance, calculates the number of delay samples for which data continuity and simultaneity are guaranteed, and transmits this delay sample number to the protection processing unit 12.
When the redundant communication control unit 6 receives the current data frame within the number of delay samples, the protection processing unit 12 performs an operation for protecting the power system using the current data frame and detects a system fault. The circuit breaker 20 connected to the power system is controlled to protect the power system. At this time, the protection processing unit 12 receives the current data frame from the current data frame buffer 22 at a timing delayed from the value of the sample counter 21 by the maximum value of the communication delay time calculated by the communication delay time calculation unit for each communication system. read out.

  And the protection process part 12 performs the current differential relay calculation for protecting an electric power grid | system using the current data taken in by the other apparatus contained in the read current data frame. For example, the protection processing unit 12 calculates that the current data of the own device and the current data of the other device are compared, and if the comparison result is within a predetermined threshold, no abnormality has occurred in the power system, and the comparison result is the threshold value. If it exceeds, it is determined that an abnormality has occurred in the power system. Then, the protection processing unit 12 outputs to the I / O control unit 3 a shut-off command or an open command to be given to the circuit breaker 20 based on the calculation result. In the following description, the current data frame is abbreviated as “frame”, and the current differential relay calculation is also abbreviated as “relay calculation”.

  As the main memory 2, a RAM (Random Access Memory) in which various data is written and read is used. The main memory 2 includes a sample counter 21 and a current data frame buffer 22. In the current data frame buffer 22, a frame including data used for relay calculation of the protection processing unit 12 is buffered. The main memory 2 manages the local time (an example of time) used by the main control unit 1. For example, the local time is a value that starts counting from “0” when the power supply of the digital protection control device 10 is turned on, but may be GMT (Greenwich Mean Time).

  The sample counter 21 stores values from “0” to “11” counted by the main control unit 1. The value of the sample counter 21 is used when the redundant communication control unit 6 transmits a frame to another device under the control of the main control unit 1, and when the frame received from the other device is written in the current data frame buffer 22. Also used for. The value of the sample counter 21 is also used when the protection processing unit 12 reads a frame from the current data frame buffer 22.

  The current data frame buffer 22 (an example of a communication frame buffer) buffers and stores the first-arrived frame for each value of the sample counter attached to the frame and for each other digital protection control device that has transmitted the frame. . The current data frame buffer 22 stores, as an index, the value of the sample counter 21 given by another device at the time of frame transmission and the device ID of the other device that is the frame transmission source. Regardless of the transmission delay time of the network, the current data frame buffer 22 buffers the frame received by the redundant communication control unit 6 to guarantee the continuity and simultaneity of the current data read from the frame. it can.

The I / O control unit 3 performs control for interrupting the circuit breaker 20 when receiving a circuit break command from the protection processing unit 12 to the circuit breaker 20. Further, when receiving an opening command from the protection processing unit 12 to the circuit breaker 20, the I / O control unit 3 performs control to open the circuit breaker 20 that has been interrupted.
The input converter 4 is an analog value (analog data) at a level at which the analog input unit 5 can handle the current of the power system input from a CT (Current Transformer) or VT (Voltage Transformer) connected to the power system. Convert to

  The analog input unit 5 performs A / D conversion on the analog value input from the input converter 4, and outputs digitized sampling data (digital data) to the system bus B1. The sampling data is given to the sampling data by the control unit 1 and used as current data.

  The redundant communication control unit 6 is configured by, for example, an FPGA (Field Programmable Gate Array) and is used as a communication path interface. And the redundant communication control part 6 transmits the flame | frame which carried the current data converted by the analog input part 5 of an own apparatus to the redundant communication path. Further, the redundant communication control unit 6 performs control for buffering the first-arrived frame in the current data frame buffer 22 among the frames transmitted to the communication path by other devices and discarding the later-arrived frame.

  The redundant communication control unit 6 includes a first transmission buffer 61A, a first transmission unit 62A, a second transmission buffer 61B, and a second transmission unit 62B as a transmission system. The redundant communication control unit 6 includes a first receiving unit 65A, a second receiving unit 65B, a first-come-first-served arrival determination circuit 66, a first receiving buffer 67A, and a second receiving buffer 67B as a receiving system. The redundant communication control unit 6 includes a first communication unit 63 and a second communication unit 64 as interfaces for transmission and reception.

  The first transmission buffer 61A buffers frames transmitted to the first communication system. The second transmission buffer 61B buffers frames transmitted to the second communication system. The first transmission buffer 61A and the second transmission buffer 61B are provided to adjust the transmission timing of the frame.

  The first transmission unit 62A transmits the frame buffered in the first transmission buffer 61A to the first communication unit 63. The second transmission unit 62B transmits the frame buffered in the second transmission buffer 61B to the second communication unit 64.

  The first communication unit 63 transmits a frame to the first communication system, and receives a frame transmitted from the first communication system by another device. The second communication unit 64 transmits a frame to the second communication system and receives a frame transmitted from the second communication system by another device. If the communication path is configured with HSR, the first communication unit 63 transmits the frame clockwise and the second communication unit 64 is used as a port that receives the frame clockwise. Further, the second communication unit 64 transmits a frame counterclockwise, and the first communication unit 63 is also used as a port that receives the frame counterclockwise. On the other hand, in the case of a communication path configured by PRP, the first communication unit 63 is used as a port for transmitting and receiving frames in the A system, and the second communication unit 64 is used as a port for transmitting and receiving frames in the B system.

  65 A of 1st receiving parts deliver the frame which the 1st communication part 63 received to the first arrival first arrival determination circuit 66. The second receiving unit 65B transfers the frame received by the second communication unit 64 to the first-come-first-served arrival determination circuit 66.

The first arrival first arrival determination circuit 66 determines first arrival or second arrival between the frame received from the first reception unit 65A and the frame received from the second reception unit 65B.
The first reception buffer 67A buffers frames received by the first reception unit 65A. The second reception buffer 67B buffers frames received by the second reception unit 65B. The first reception buffer 67A and the second reception buffer 67B are provided to adjust the frame reception speed.

The display unit 7 uses, for example, a liquid crystal display, and displays a result of processing performed by the digital protection control device 10 to the user.
For example, a switch is used for the operation unit 8, and a user can perform a predetermined operation input and instruction.
A ROM (Read Only Memory) 9 stores a program code of software for realizing each function according to the present embodiment. The main control unit 1 can read a program code from the ROM 9 and execute a predetermined process.

  Next, an operation example of the digital protection control device 10 will be described in the order of an example in which the own device transmits a frame to another device and an example in which the own device receives a frame from the other device.

First, an example in which the own device transmits a frame to another device will be described.
The main control unit 1 receives the current data converted by the analog input unit 5 every 30 electrical angles via the system bus B1, and receives the current data and the value of the sample counter 21 calculated from the local time of its own device. Create a frame with. This frame is used not only for HSR but also for PRP. The method of calculating the value of the sample counter 21 performed by the main control unit 1 is arbitrary. For example, in order to create the value of the sample counter 21 of “0” to “11” in order to divide one cycle of the AC waveform into 12, the local time of the digital protection control device 10 is divided by the sampling cycle time, Further, a remainder obtained by dividing the value by “12” may be used.

  The main control unit 1 writes the created frame in the first transmission buffer 61A and the second transmission buffer 61B in the redundant communication control unit 6. The frame written in the first transmission buffer 61A is transmitted from the first communication unit 63 to the other device via the communication path via the first transmission unit 62A. On the other hand, the frame written in the second transmission buffer 61B is transmitted from the second communication unit 64 to the other device via the communication channel via the second transmission unit 62B. This frame may be broadcast to all the devices by broadcast or multicast, or may be transmitted to individual devices by unicast.

Next, an example in which the own device receives a frame from another device will be described.
When the first communication unit 63 in the redundant communication control unit 6 receives the frame transmitted from the communication path by another device, the frame is passed to the first-arrival / arrival determination circuit 66 via the first reception unit 65A. Further, when the second communication unit 64 receives a frame transmitted by another device from the communication path, the frame is passed to the first-arrival / first-arrival determination circuit 66 via the second reception unit 65B.

  The first-arrival / first-arrival determination circuit 66 performs first reception of a frame determined to be the first-arrival frame received from the first receiver 65A and the second receiver 65B (this frame is referred to as a “first-arrival frame”). Write to the buffer 67A or the second reception buffer 67B. On the other hand, the first-come-first-served arrival determination circuit 66 discards the frame determined to be the first-come-first-served.

  Thereafter, the main control unit 1 reads the first-arrival frame from the first reception buffer 67A or the second reception buffer 67B in the redundant communication control unit 6. Then, the main control unit 1 assigns the value of the sample counter 21 and the transmission source device ID as indexes, and buffers them in the current data frame buffer 22. The transmission source device ID is not limited as long as it is the only device that can identify the device, such as the MAC address of the transmission source device or a device number uniquely assigned to the transmission source device.

<Problems of HSR>
Next, the problem of HSR in which the communication delay time of frames differs greatly between clockwise and counterclockwise will be described with reference to FIGS.
FIG. 4 is a configuration diagram illustrating an example of an HSR network topology. FIG. 4A shows an example in which no abnormality has occurred in the communication path, and FIG. 4B shows an example in which a single abnormality has occurred between the devices AB.

  As shown in FIG. 1 described above, all the digital protection control devices 10 (referred to as devices A to D in the figure) are ring-shaped in the communication path N1 configured by the HSR shown in FIG. It is connected. In the following description, the digital protection control device 10 connected to the communication path N1 is abbreviated as device A to device D.

  As shown in FIG. 4A, in the communication path N1, the communication delay time between the devices A and B and between the devices BC is 0.5 ms, but between the devices A and D is 2.0 ms, and between the devices C and D. Is different in communication delay time such as 1.0 ms. When the communication path is healthy, the counterclockwise frame F1 with a communication delay time of 0.5 ms always arrives first at the apparatus B and is buffered. Thereafter, when the clockwise frame F2 having a communication delay time of 3.5 ms arrives at the apparatus B later, the clockwise frame F2 is discarded by the apparatus B.

  As shown in FIG. 4B, when an abnormality occurs in the communication path between apparatuses A and B, the frame that apparatus B receives from apparatus A is only the clockwise frame F2. At this time, the communication delay time is 3.5 ms.

<Frame when an error occurs in the communication path>
Next, a frame time chart will be described.
FIG. 5 is a time chart of a frame when an abnormality occurs in the communication path and a frame reception delay occurs.
FIG. 6 shows an example of a frame buffered in the current data frame buffer 22 of the device B. 6A is a sample counter “0”, FIG. 6B is a sample counter “1”, FIG. 6C is a sample counter “2”, FIG. 6D is a sample counter “3”, and FIG. 6E is a buffered frame in the sample counter “4”. An example of
5 and 6, the value of the sample counter 21 is described as “sample counter”.

  The time chart shown in FIG. 5 represents how each device transmits a frame for each sample counter of “0” to “11” in which the analog input unit 5 samples the current value every 30 degrees of electrical angle. ing. The period of each sample counter is, for example, about 1.67 ms (= 1/50/12) when the power supply frequency of the power system is 50 Hz. In this example, frames transmitted from the devices A, C, and D to the device B are shown. An arrow 31 indicated by a solid line in the drawing is a frame addressed to apparatus B transmitted from apparatuses A, C, and D when the sample counter is “0”. An arrow 32 indicated by a broken line is a frame addressed to the device B transmitted from the devices A, C, and D when the sample counter is “1”. An arrow 33 indicated by an alternate long and short dash line is a frame addressed to apparatus B transmitted from apparatuses A, C, and D when the sample counter is “2”. The shaded portion in the figure indicates that an abnormality has occurred in the transmission path between the apparatuses A and B, and frame transmission / reception has become impossible. A double arrow 34 represents a period during which the device B cannot receive the device A frame.

  In FIG. 6, buffer areas for buffering frames received by the device B from the devices A, C and D in the current data frame buffer 22 are provided corresponding to the sample counters “0” to “11”. Is shown. In the drawing, it is shown that the frame received by the device B is buffered in the filled buffer area, and the frame is not buffered in the unfilled buffer area. Note that the current data frame buffer 22 also buffers frames created by the device B itself and transmitted to the other devices A, C, and D.

  For example, the frames transmitted by the devices A, C, and D when the sample counter is “0” shown in FIG. 5 are received by the device B during the sample counter “0”. As shown in FIG. 6A, in the current data frame buffer 22 of the device B, frames transmitted from the devices A, B, and C are buffered by the sample counter “0”. For this reason, in the relay calculation performed by the device B when the sample counter is “1”, the current data loaded on the frame transmitted from each device to the device B using the sample counter “0” is used. That is, the number of delay samples at this time is “1”.

  Similarly, when the sample counter is “1” shown in FIG. 5, the frames transmitted by the devices A, C, and D are received by the device B during the sample counter “1”. As shown in FIG. 6B, in the current data frame buffer 22 of the device B, frames transmitted from the devices A, B, and C are buffered by the sample counter “1”. For this reason, the current data transmitted from each device to the device B using the sample counter “1” is used for the relay calculation performed by the device B when the sample counter is “2”. Thus, in the sample counters “0” and “1”, in the state where the frames are buffered in all the buffer areas of the devices A to D, the continuity of the frames can be guaranteed.

Here, consider a case where an abnormality occurs in the communication path between apparatuses A and B in the middle of the sample counter “1”.
When a single abnormality occurs in the communication path, apparatus B cannot receive the counterclockwise frame F1 from apparatus A. When the sample counter is “2”, the device B cannot receive the frame from the device A, and therefore cannot buffer the frame in the buffer area of the device B. Device A transmits a clockwise frame F2 when the sample counter is “2”.
After that, as shown in FIGS. 6C and 6D, the frame is not buffered in the buffer area of the device B even after the sample counter has increased to “2” and “3”.

  The device B cannot receive the frame transmitted from the device A with the sample counter “2” unless it reaches the sample counter “4”. When the device B receives the clockwise frame F2 having a large communication delay time transmitted from the device A at the sample counter “4” at the timing when the device reaches the sample counter “4”, the device B enters the buffer area of the device B as shown in FIG. 6E. Frames can be buffered. When a single abnormality occurs in the communication path in this way, the reception interval from when device B receives the frame of sample counter “1” to the reception of the frame of sample counter “2” becomes long. That is, if the delay sample is set to “1”, when the sample counter is “3”, the frame of the sample counter “2” of the device A has not been received, so that it is impossible to maintain the frame synchronism.

  This reception interval depends on the time difference between the communication delays in the clockwise and counterclockwise directions of the frame. When this reception interval becomes longer than the period of current differential calculation, a period in which frames transmitted from all apparatuses (apparatuses A, C, and D) cannot be aligned occurs in apparatus B, and during that period, the power system The protection function is locked. If a grid fault occurs while the protective function is locked, the power grid may be damaged.

<Frame when communication path error is recovered>
Next, a frame time chart when the communication path abnormality is recovered will be described.
FIG. 7 is a time chart of the frame when the communication path abnormality is recovered.
FIG. 8 shows an example of a frame buffered in the current data frame buffer 22 of the device B. 8A shows an example of buffered frames in the sample counter “2”, FIG. 8B shows a sample counter “3”, and FIG. 8C shows a buffered frame in the sample counter “4”.
7 and 8, the value of the sample counter 21 is described as “sample counter”.

  In the time chart shown in FIG. 7, an arrow 41 indicated by a solid line in the drawing is a frame addressed to the device B transmitted from the devices A, C, and D when the sample counter is “2”. An arrow 42 indicated by a broken line is a frame addressed to the device B transmitted from the devices A, C, and D when the sample counter is “3”. An arrow 43 indicated by an alternate long and short dash line is a frame addressed to apparatus B transmitted from apparatuses A, C, and D when the sample counter is “4”. A double arrow 44 represents a period in which discontinuity occurs in the frame received by the device B.

  As shown in FIG. 7, the communication abnormality occurring between the apparatuses B and A during the sample counters “0” and “1” continues. However, after the reception interval between apparatus B and apparatus A temporarily increases as shown in FIG. 5, apparatus B receives clockwise frame F2 from apparatus A even if the communication path continues to be abnormal. Is received, the protection function is unlocked. Note that the devices A, C, and D transmit frames to the device B even when the sample counters are “0” and “1”, but the description is omitted in both FIG. 7 and FIG.

  As shown in FIG. 7, it is assumed that the communication path abnormality between the apparatuses A and B is recovered between the sample counters “2” and “3”. At this time, in the device B, before receiving the clockwise frame F2 having a large communication delay time transmitted from the device A by the sample counter “2”, the communication delay time transmitted from the device A by the sample counter “3” is determined. A small counterclockwise frame F1 is received. Then, as shown in FIG. 8B, the frame transmitted by the devices C and D when the sample counter is “3” is received by the device B, and when the sample counter is “4” as shown in FIG. 8C, the devices A, C, and D The transmitted frame is received by apparatus B. In FIG. 8C, the order in which the frames are received by the device B is indicated as (1) to (3) in the buffer area. Here, since the frames transmitted from the devices A and C are simultaneously received by the device B, both are set to (1). After the communication path abnormality is recovered, when the sample counter is “4”, since the device B receives frames in the order of “3”, “2”, “4”, there is a discontinuity in the frame received by the device B. Occur.

  However, it is necessary to guarantee the simultaneity and continuity of frames that occur when a redundant communication path is abnormal and to enable seamless operation. In order for the digital protection control device 10 to perform a current differential relay operation, the device itself must receive and arrange frames transmitted from all other devices using the same sample counter. Therefore, the main control unit 1 reads the frame from the current data frame buffer 22 at a timing delayed from the value of the sample counter 21 in consideration of the communication delay time, and performs a relay calculation.

  However, if the delay of the counter used in the relay calculation is the shortest value when the communication path is sound, even if the arrival of the frame is slightly delayed, it is transmitted from all devices within the allowable communication delay time. As a result, the continuity of received frames cannot be guaranteed. For this reason, if the counter used in the relay calculation is delayed by the number of samples corresponding to the maximum delay time, an error has occurred in the communication path, and even when the error has been recovered, all devices have transmitted the error. Frames can be aligned.

  Moreover, since the maximum delay time constraint has a large margin, it deviates from the actual delay time. If the timing at which the receiving apparatus receives the frame is late, the start of the relay calculation using the current data read from this frame is also delayed. As a result, it takes a long time from the occurrence of a system fault until the protection processing unit 12 outputs a circuit breaker 20 opening command, which is not preferable from the viewpoint of protection of the power system.

  For this reason, in the digital protection control apparatus 10 according to the first embodiment, the communication delay time when a single abnormality occurs in the communication path is calculated in advance according to the network topology applied to the communication path. Keep it. Then, the digital protection control device 10 delays the counter by the number of samples corresponding to the calculated communication delay time. Thereby, it becomes possible to guarantee the continuity of the frames used by the main control unit 1 for the relay calculation, and the relay calculation is not delayed unnecessarily.

An example of a method for calculating the communication delay time in the HSR will be described below.
As shown in FIG. 4, it is assumed that the network N1 is configured by four devices A to D. Here, a description will be given focusing on the apparatus A.

  The device A transmits a delay time measurement frame used for measuring the communication delay time of the communication path to all devices at a constant period. It is assumed that the local time of the device A is placed in the delay time measurement frame as information indicating transmission timing. The local times of the devices A to D are assumed to be in a state where synchronization is established.

  In normal HSR, device A transmits frames of the same data on both the clockwise and counterclockwise routes, so that device A normally receives only the first-arrived frame via the route with a fast delay time. However, in the present embodiment, the redundant communication control unit 6 of the device A transmits the frames sequentially one by one in the clockwise direction and the counterclockwise direction, so that not only the first frame that passes through the path with the fast delay time. Also, a late arrival frame is received via a route with a slow delay time. Thereby, the communication delay time calculation unit 11 of the device A calculates the communication delay time for each communication system based on the time until the frame transmitted by the redundant communication control unit 6 is received. That is, apparatus A can obtain the clockwise delay time and the counterclockwise delay time individually.

Here, communication delay times of apparatuses B, C, and D with respect to apparatus A will be described.
FIG. 9 is an explanatory diagram illustrating an example of the communication delay time with the devices B, C, and D calculated by the device A.

  When the device A receives the delay time measurement frames from all the devices B, C, and D connected to the network, the device A calculates the communication delay times of the clockwise route and the counterclockwise route, and performs maximum communication. Find the delay time. The sum of the communication delay times of the clockwise route and the counterclockwise route is the maximum delay time of the entire communication channel.

  For example, the communication delay time until the frame transmitted by the device B reaches the device A is 0.5 ms for the clockwise route starting from the device B, and 3.5 ms for the counterclockwise route. is there. For this reason, the maximum communication delay time is 4.0 ms (= 0.5 ms + 3.5 ms). The communication delay time until the frames transmitted by the devices C and D reach the device A is also obtained in the same manner.

  Then, the communication delay time calculation unit 11 divides the obtained maximum delay time by the time per sample, so that even if a single abnormality occurs in the communication path, delay samples that guarantee continuity and simultaneity of frames are guaranteed. Calculate the number. In the example shown in FIG. 4, the maximum delay time of the entire communication channel is 4.0 ms, and when this value is divided by the time per sample (1.67 ms) in a 50 Hz system, for example, it becomes about 2.4 samples. . For this reason, the value of the sample counter 21 delayed by 3 samples obtained by rounding up the solution (2.4 samples) may be used for the relay calculation. In the 60 Hz system, dividing the maximum delay time (4.0 ms) by the time per sample (1.388 ms) yields about 2.8 samples. Also in this case, the value of the sample counter 21 delayed by 3 samples obtained by rounding up the solution (2.8 samples) may be used for the relay calculation.

  That is, in the relay calculation with the sample counter “3”, the current data extracted from the frame transmitted when each device is the sample counter “0” is used. Similarly, in the relay calculation of the sample counter “4”, the current data extracted from the frame transmitted when each device is the sample counter “1” is used. By using the value of the sample counter 21 delayed in this way for the relay calculation, even if a single abnormality occurs in any part of the communication path and recovers, the continuity of the frame is maintained and further used for the relay calculation. It is possible to maintain the continuity of current data.

  If the synchronization of the local time is established among all the devices, even if the devices B to D that have received the delay time measurement frame from the device A, the difference from the local time of the own device is calculated. By taking this, the communication delay time with the device A can be obtained. Although the focus is on the transmission of the device A here, all the devices can transmit the delay time measurement frame as described above.

  According to the digital protection control apparatus 10 according to the first embodiment described above, in order to continue protection of the power system when a single abnormality occurs in the redundant communication path constituted by the HSR. The continuity and simultaneity of necessary frames (data) can be guaranteed.

  Further, the digital protection control device 10 can guarantee the continuity and simultaneity of frames (data) even after the abnormality that has occurred in the communication path is recovered. For this reason, there is no loss of frames (data) between the occurrence of an abnormality in the communication path and the recovery, and seamless operation can be performed.

In the first embodiment, delay time measurement by HSR has been described. However, PRP is not a loop network topology. For this reason, in HSR, the maximum delay time of the entire communication path is calculated as the sum of the clockwise and counterclockwise communication delay times. In PRP, the largest communication delay time among the A system and B system communication delay times is maximized. The communication delay time may be used.
In the first embodiment, the current differential relay calculation has been described. However, the relay calculation method is not limited.

  In addition, if there is a possibility that the communication delay time of the entire communication path will change dynamically, each device may periodically measure the communication delay time of the network and recalculate the sample counter used in the relay calculation. Good. If there is a possibility that the delay of the entire communication path may change dynamically, the sample counter calculated here may be given a margin.

  In the first embodiment, an example in which a dedicated frame is transmitted and received for delay time measurement has been described. However, the frame may be shared with other frames, or the delay time may be obtained by another method. If you can, that's fine.

[2-1. Second Embodiment (Time Synchronization with PRP)]
Next, a digital protection control apparatus according to the second embodiment of the present invention will be described. Since the local time of the digital protection control apparatus according to the second embodiment is not necessarily synchronized with the local time of the other apparatus, it is necessary to synchronize the local time of the own apparatus and the other apparatus.

<Internal configuration example of digital protection control device>
FIG. 10 is a block diagram showing an example of the internal configuration of the digital protection control apparatus 10A. Of the functional blocks of the digital protection control device 10A, functional blocks having the same reference numerals as those of the digital protection control device 10 according to the first embodiment have substantially the same functions.

  The main control unit 1A includes a reception port determination unit 13 and a time synchronization calculation unit 14 in addition to the communication delay time calculation unit 11 and the protection processing unit 12 described above.

  The reception port determination unit 13 is used as an example of a communication system determination unit that determines whether the communication system to which the first-arrived frame received by the redundant communication control unit 6 is transmitted is the A system or the B system. The reception port determination unit 13 determines which of the first communication unit 63 and the second communication unit 64 used as a port has received the frame, so that the first received frame is either the A system or the B system. It is possible to grasp whether the communication path has passed. Then, the reception port determination unit 13 outputs the reception port determination result to the time synchronization calculation unit 14.

  The time synchronization calculation unit 14 uses a frame transmitted and received between the redundant communication control unit 6 and another device with respect to the communication system determined by the reception port determination unit 13 to store the main storage memory with the other device. 2 to synchronize the local time managed. For example, the time synchronization calculation unit 14 calculates the path delay value of the communication path of the A system or the B system based on the information of the port (the first communication unit 63 or the second communication unit 64) that has received the frame. An operation is performed to synchronize the local time managed by the device with the local time managed by another device. Detailed processing will be described later for the local time synchronization calculation performed by the time synchronization calculation unit 14.

  In the protection calculation by the current differential protection method, current data sampled at the same time by all devices connected through redundant communication paths is used. For this reason, it is necessary to synchronize the sample timing of the analog input unit 5 included in all devices connected to the network with high accuracy. Examples of a time synchronization method using a network include NTP (Network Time Protocol), SNTP (Simple Network Time Protocol), PTP (Precision Time Protocol), and the like. There are various methods for synchronizing the sample timing on the network. Here, an example using PTP defined by IEEE (Institute of Electrical and Electronics Engineers) 1588-2008, which is one of the methods, will be described.

  The PTP includes a master station that serves as a reference for local time and a slave station that adjusts the local time to the master station. The PTP calculates the difference between the communication delay and the local time by exchanging time information between the master station and the slave station and between the slave station and the slave station, and corrects the local time of the slave station by the difference of the local time. This is a method of synchronizing the local time of the slave station. PTP includes an end-to-end-delay measurement method and a peer-to-peer-delay measurement method. Here, the PTP End To End-Delay Measurement method will be described.

<PTP execution procedure>
FIG. 11 is a flowchart illustrating an example of a PTP execution procedure in a communication path that is not redundant.
FIG. 12 is a sequence diagram showing an example of message notification performed between the master station and the slave station by the PTP End To End-Delay Measurement method in the process of FIG. In FIG. 12, step numbers corresponding to the processes in which the master station and the slave station notify each other of messages in FIG. 11 are given. The master station may be the device B and the slave station in the HSR (see FIG. 1) or PRP (see FIG. 2), and the slave station may be the device D, but the relationship between the master station and the slave station is not uniquely determined. The time used in the following description represents a value obtained from the local time managed by the master station and the slave station. It is assumed that the message is included in a frame transmitted and received between the master station and the slave station.

  First, the master station transmits a Sync message to the slave station (S1). At this time, the main station stores the transmission time t1 of the Sync message (S2). When the slave station receives the Sync message, the slave station stores the reception time t2 of the Sync message (S3).

  The master station notifies the slave station of the transmission time t1 by one of the following methods (S4). The first method is a method (1 step method) in which information of transmission time t1 is included in the Sync message. The second method is a method (2-step method) in which information of transmission time t1 is included in the Follow_up message following the Sync message.

  Subsequently, the slave station transmits a Delay_Req message to the master station (S5). At this time, the slave station stores the transmission time t3 of the Delay_Req message (S6). When receiving the Delay_Req message, the master station stores the reception time t4 of the Delay_Req message (S7).

  Then, the master station puts information on the reception time t4 in the Delay_Resp message and notifies the slave station of the reception time t4 (S8). The slave station that has received the Delay_Resp message calculates the communication delay and time difference between the master station and the slave station from t1, t2, t3, and t4 (S9). In calculating the communication delay, there is a premise that the communication delay between the master station and the slave station is equal in the round trip path. Accordingly, the calculation of the one-way communication delay td is expressed by the following equation (1), and the time difference tdiff between the master station and the slave station is expressed by the following equation (2). With tdiff, the master station and the slave station can synchronize the time.

td = {(t4 − t3) + (t2 − t1)} / 2 Equation (1)
tdiff = {(t4−t3) − (t2−t1)} / 2 Equation (2)

  In an ordinary star network topology, the communication path is not made redundant and the path between the master station and the slave station is unique. Therefore, the time synchronization between the master station and the slave station can be established without any problem by uniquely calculating the communication delay by the method shown in FIGS. However, when the above method is applied to a redundant communication path such as PRP, there are a plurality of paths between the master station and the slave station, and it is considered that the communication delay time is different between the A system and the B system of the network. For example, there is a possibility that the communication path system that received the Sync message first will be different from the communication path system that received the Delay_Req message first, and the communication delay is not unique. If the communication system for transmitting and receiving a pair of Sync and Delay_Req is not the same, the master station and the slave station cannot perform time synchronization correctly.

  As a solution to this problem, IEC (International Electrotechnical Commission) 62439-3 describes handling when applying PTP to HSR and PRP. In IEC62439-3, PRP uses the first arrival frame and discards the later arrival frame. However, for frames transmitted by PTP, the arrival arrival frame must not be discarded. It is specified that each device takes a synchronization procedure. For this reason, the first frame that has been a feature of HSR and PRP is used for frames transmitted by PTP in the past, and the principle of discarding the last frame is not applied, and communication delay is measured for each of multiple paths. Was. Also, the first-come-first-arrival determination of a frame is generally implemented by hardware from the viewpoint of processing speed. However, determining by hardware whether the received frame is a frame transmitted by PTP not only increases the complexity of the hardware but also increases the manufacturing cost. Further, the slave station needs to handle the PTP message from the two communication channels, and the software complexity increases.

  Therefore, when the digital protection control device 10A performs time synchronization using PTP in a redundant communication path such as HSR and PRP, the digital protection control device 10A can select any frame used for time synchronization without installing special hardware. It is possible to determine whether or not it is received at the port. In the following, a method is proposed in which the digital protection control device 10A correctly synchronizes the local time with another device without destroying the basic of using the first-arrived frame and discarding the later-arrived frame. In the present embodiment, the End To End-Delay Measurement method is applied to a network configured with PRP.

<Execution procedure of time synchronization in PRP>
Next, a description will be given of a method in which the digital protection control device 10A connected to the communication path made redundant by PRP performs time synchronization using the PTP End To End-Delay Measurement method.

  In PRP, the redundant communication control unit 6 of the digital protection control device 10 </ b> A transmits and receives frames to and from other devices through the communication system determined by the reception port determination unit 13. The time synchronization calculation unit 14 calculates the communication delay and time difference of the communication system based on the transmission time and reception time of the frame transmitted / received between the redundant communication control unit 6 and another device, and synchronizes the time. Detailed processing will be described below.

  FIG. 13 is a flowchart illustrating an example of a time synchronization execution procedure performed by the digital protection control apparatus 10A connected to the PRP network. In this execution procedure, the same procedure as the message notification performed between the master station and the slave station by the PTP End To End-Delay Measurement method shown in FIG. 12 is used. Therefore, the description of the sequence diagram corresponding to FIG. Omitted.

  First, the master station transmits a Sync message to the slave station through the A system and the B system (S11), and stores the transmission time t1 of the Sync message (S12). Here, the A system is an example of a first communication system, and the B system is an example of a second communication system.

  When the slave station receives a Sync message that arrives first from the A system or the B system, the slave station inputs the reception time t2 of the Sync message and the reception port determined by the reception port determination unit 13 to the time synchronization calculation unit 14. The time synchronization calculation unit 14 stores a value FlgSyncRX indicating the communication system that has received the Sync message (S13). The slave station discards the Sync message transmitted from a communication system different from the communication system that received the Sync message as a late arrival.

  The master station notifies the slave station of the transmission time t1 by one of the following methods (S14). The first method is a method (1 step method) in which information of transmission time t1 is included in the Sync message. The second method is a method (2-step method) in which information of transmission time t1 is included in the Follow_up message following the Sync message.

  In the case of the 2-step method, the Follow_up message is transmitted from the master station to the slave station. The Follow_up message is intended to notify the slave station of the Sync message transmission time t1, and is intended to measure the path delay time. is not. For this reason, the slave station may receive the Follow_up message in either the A system or the B system.

  When transmitting the Delay_Req message to the master station, the slave station determines whether or not the Sync message has been received from the master station in the A system (S15). At this time, the slave station refers to FlgSyncRX, and if a Sync message is received by the A system, transmits a Delay_Req message only to the A system (S15A). On the other hand, if the slave station has received the Sync message in the B system, the slave station transmits a Delay_Req message only to the B system (S15B). Then, the slave station stores the transmission time t3 of the Delay_Req message (S16).

  When receiving the Delay_Req message from the slave station, the master station stores the reception time t4 of the Delay_Req message (S17). Then, the master station puts information on the reception time t4 in the Delay_Resp message and notifies the slave station of the reception time t4 (S18). The Delay_Resp message is notified for the purpose of notifying the slave station of the reception time of the Delay_Req message, and is not intended for measuring the path delay time. For this reason, the master station may transmit the Delay_Resp message to the A system and the B system, or may transmit the Delay_Resp message only to the system that has received the Delay_Req message from the slave station.

  The slave station that has received the Delay_Resp message calculates the communication delay between the master station and the slave station from t1, t2, t3, and t4 using the above equation (1), and calculates the time difference tdiff using the above equation (2). Calculate (S19). Then, the slave station synchronizes the time of the master station and the time of the slave station based on the calculated time difference tdiff.

  Thus, in the digital protection control device 10A in PRP, the redundant communication control unit 6 transmits a message to another device through the communication system that received the frame. This message includes the reception time of a message received from another device and the transmission time of a message transmitted to the other device. Therefore, the digital protection control device 10A can calculate the communication delay td with the other device in the communication system that transmits and receives the message and the time difference tdiff, and synchronize the local time with the other device. In this way, the digital protection control apparatus 10A can correctly synchronize the local time without destroying the basic process of using the first-arrival frame and discarding the second-arrival frame.

[2-2. Second embodiment (time synchronization in HSR)]
Next, a description will be given of a method in which the adjacent digital protection control apparatus 10A performs time synchronization using the PTP Peer To Peer-Delay Measurement method in the communication path made redundant by the HSR.

  In the HSR, the redundant communication control unit 6 of the digital protection control device 10A transmits a frame to the communication system determined by the reception port determination unit 13 and receives a frame from this communication system to other adjacent devices. . The time synchronization calculation unit 14 calculates the path delay value of the communication system of the frame transmitted by the redundant communication control unit 6, and calculates the communication delay and time difference of the communication system calculated based on the transmission time and reception time of the frame. To synchronize the time. Here, the time synchronization calculation unit 14 calculates a path delay value for each communication system in advance based on the time when the redundant communication control unit 6 transmits and receives a frame for calculating the communication delay time, and the redundant communication control unit 6 A path delay value corresponding to a communication system of a frame to be transmitted / received is selected.

The time synchronization in the HSR is performed by combining a path delay calculation process described with reference to FIGS. 14 and 15 below and a time difference calculation process described with reference to FIGS. 16 and 17.
For example, assume that apparatus A shown in FIG. 4A is a master station, and apparatuses B, C, and D are slave stations. The device B transmits / receives a frame (message) to / from the adjacent devices A and C, and obtains a path delay between the devices A and C adjacent to the device B. Similarly, the device C transmits / receives a frame (message) to / from the adjacent devices B and D, and obtains a path delay between the devices B and D adjacent to the device C. Here, paying attention to the device C, the device C receives a Sync message counterclockwise from the device A, for example, in order to obtain the communication delay time between the devices AC. When this Sync message passes through the device B that is not the destination of the Sync message, the device B is loaded with a path delay between the devices AB. Therefore, the device C receives the Sync message from the device A, thereby acquiring a path delay between the devices A and C in the communication system to which the Sync message is transmitted. The time difference between the devices A and C can be obtained. Detailed processing will be described below.

<Example of calculating path delay in HSR>
First, a procedure for calculating a path delay in the HSR will be described.
FIG. 14 is a flowchart illustrating an example of calculating the path delay.
FIG. 15 is a sequence diagram showing an example of message notification performed between the slave station and its adjacent devices by the PTP Peer To Peer-Delay Measurement method in the process of FIG. In FIG. 15, step numbers corresponding to the processes in which the slave station and its neighboring devices notify each other of messages in FIG. 14 are given. Here, the adjacent devices (denoted as “neighboring ends” in the drawings) shown in FIGS. 14 and 15 may be either the master station or the slave station.

  First, all digital protection control devices 10A (slave stations) connected to communication paths made redundant by HSR transmit PDelay_Req messages to the clockwise route in order to measure the route delay with other adjacent devices. (S21). At this time, the slave station stores the transmission time t1 of the PDelay_Req message (S22).

  An adjacent device that is adjacent to the slave station that has transmitted the PDelay_Req message and that has received the PDelay_Req message stores the reception time t2 of the PDelay_Req message (S23). Subsequently, the adjacent device notifies the slave station of the PDelay_Resp message in which the information of the reception time t2 is added to the PDelay_Resp message (S24), and stores the transmission time t3 of the PDelay_Resp message (S25).

  Further, immediately after transmitting the PDelay_Resp message, the adjacent device notifies the slave station of a PDelay_Resp_FollowUp message carrying information on the transmission time t3 (S26). The slave station that has received the PDelay_Resp message stores the reception time t4 (S27).

  Here, there is a premise that the communication delay is equal in the round trip when calculating the path delay. Therefore, the slave station that has received PDelay_Resp_FollowUp from the adjacent device calculates a clockwise path delay λA with the adjacent device from t1, t2, t3, and t4 by the following equation (3) (S28).

  λA = {(t4 − t3) + (t2 − t1)} / 2 Equation (3)

  Further, the slave station performs the same processing (S21 to S28) as described above for the counterclockwise route, and obtains the counterclockwise route delay λB. In this way, the slave station can determine the path delays λA and λB from the two devices adjacent to the slave station.

<Example of calculating time difference in HSR>
Next, an example of calculating the time difference in the HSR will be described.
FIG. 16 is a flowchart illustrating an example of a time difference calculation process.
FIG. 17 is a sequence diagram illustrating an example of message notification performed between the master station and the slave station by the PTP Peer To Peer-Delay Measurement method in the process of FIG. In FIG. 17, step numbers corresponding to the processes in which the master station and the slave station notify each other of messages in FIG. 16 are given.

  The master station transmits a Sync message to the slave station (S31). At this time, the main station stores the transmission time t5 of the Sync message (S32). For example, the Sync message transmitted counterclockwise by the master station (apparatus A) shown in FIG. 4A to the slave station (apparatus C) is provided when apparatus B that is not the destination of the Sync message transfers the Sync message to apparatus C. B puts the path delay between devices AB. For this reason, the slave station (device C) obtains the communication delay between the devices A and C in the counterclockwise route as the route delay λB. On the other hand, in the Sync message received by the slave station (device C) in the clockwise direction, when the device D on the clockwise route transfers the Sync message to the device C, the device D causes a path delay between the devices AD. Can be placed. For this reason, the slave station (device C) obtains the communication delay between the devices AC in the clockwise route as the route delay λA.

  When the slave station receives the Sync message, the reception time t6 of the Sync message and the information of the reception port determined by the reception port determination unit 13 are input to the time synchronization calculation unit 14. Then, the slave time synchronization calculator 14 stores FlgSyncRX indicating the determination result of the reception port (S33).

  The master station notifies the slave station of the transmission time t5 by one of the following methods (S34). The first method is a method (1 step method) in which information of transmission time t5 is included in the Sync message. The second method is a method (2-step method) in which the information of transmission time t5 is placed in the Follow_up message following the Sync message.

  The slave station determines whether or not the Sync message has been received clockwise from the master station (S35). At this time, the slave station refers to FlgSyncRX to determine the master station that has received the Sync message. Then, the slave station calculates the time difference between the master station and the slave station from the times t5 and t6 and the path delays λA and λB. The time difference tdiff between the slave station and the master station is expressed by the following equation (4).

  tdiff = t6-(t5 + λX) (4)

  ΛX in equation (4) is selected by FlgSyncRX as follows: That is, when FlgSyncRX indicates clockwise, the path delay λA is used for λX (S35A). When FlgSyncRX indicates counterclockwise, the path delay λB is used for λX (S35B). Then, the slave station synchronizes the time of the master station and the time of the slave station based on the calculated time difference tdiff.

  In this way, in the digital protection control device 10A in the HSR, by calculating the path delays λA and λB between the adjacent devices and further calculating the time difference tdiff, it is possible to perform the synchronous calculation of the local time with other devices. .

  The digital protection control device 10A correctly synchronizes the local time without destroying the basic processing of using the first-arrived frame and discarding the later-arrived frame even in a network configured by HSR or PRP. It becomes possible.

  Further, the digital protection control device 10A can execute time synchronization in the redundant communication path by software by selecting a communication system. In other words, the digital protection control device 10A performs time synchronization control by software (main control unit 1) without changing the first-arrival / first-arrival determination processing of HSR or PRP frames performed by hardware (redundant communication control unit 6). Can be done.

  The digital protection control device 10A according to the second embodiment may be used as a communication control device for performing communication control other than protection of the power system.

  Further, in each of the above-described embodiments, the current data frame on which current data is loaded is described as the communication frame. However, the communication frame may be a voltage data frame carrying voltage data of the power system.

The present invention is not limited to the above-described embodiments, and various other application examples and modifications can of course be taken without departing from the gist of the present invention described in the claims.
For example, the above-described embodiments are detailed and specific descriptions of the configuration of the apparatus and the system in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described. Absent. In addition, a part of the configuration of an embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of an embodiment. Is also possible. Moreover, it is also possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.
Further, the control lines and information lines indicate what is considered necessary for the explanation, and not all the control lines and information lines on the product are necessarily shown. Actually, it may be considered that almost all the components are connected to each other.

  DESCRIPTION OF SYMBOLS 1 ... Main control part, 2 ... Main memory, 6 ... Redundant communication control part, 10 ... Digital protection control apparatus, 11 ... Communication delay time calculation part, 12 ... Protection processing part, 13 ... Reception port determination part, 14 ... Time synchronization calculation unit, 21 ... Sample counter, 22 ... Current data frame buffer

Claims (9)

A memory in which communication frames including data used for power system protection are buffered;
The communication frame is transmitted to another digital protection control apparatus connected via a plurality of redundant communication paths, and the communication frame transmitted to the communication path by the other digital protection control apparatus is transmitted. Among them, a redundant communication control unit that buffers the first-arrived communication frame in the memory and discards the later-arrived communication frame;
A communication delay time calculating unit for calculating a communication delay time of the communication path and calculating a delay sample number that guarantees continuity and simultaneity of the data;
When the communication frame is received by the redundant communication control unit within the number of delay samples, the communication frame is used to perform an operation for protection of the power system, and a circuit breaker connected to the power system is provided. And a protection processing unit that controls and protects the power system. The memory is
A sample counter that stores a value that is referenced by an analog input unit that samples and converts the analog value input from the power system into digital data;
The communication frame buffer that buffers the communication frame that arrives first for each sample counter attached to the communication frame and for each of the other digital protection control devices that transmitted the communication frame. Digital protection controller. The communication path is configured with a ring network topology,
The protection processing unit is connected to the communication frame buffer from the communication frame buffer at a timing delayed by the maximum value of the communication delay time calculated by the communication delay time calculation unit for each communication system of the communication path from the value of the sample counter. The digital protection control device according to claim 2, wherein the frame is read out. The redundant communication control unit sequentially transmits the communication frame for calculating the communication delay time for each one direction of the two communication systems,
The digital protection control according to claim 3, wherein the communication delay time calculation unit calculates the communication delay time for each communication system based on a time until the communication frame transmitted by the redundant communication control unit is received. apparatus. Furthermore, a communication system determination unit that determines a communication system of the communication path through which the communication frame that arrives first is transmitted;
For the communication system determined by the communication system determination unit, the redundant communication control unit communicates with the other digital protection control device by the communication frame transmitted / received to / from the other digital protection control device. The digital protection control device according to claim 2, further comprising: a time synchronization calculation unit that synchronizes the time managed by the memory. The communication path is composed of a network topology composed of two communication systems,
The redundant communication control unit transmits and receives the communication frame with another digital protection control device through the communication system determined by the communication system determination unit,
The time synchronization calculation unit is configured to calculate a communication delay of the communication system and the time calculated based on a transmission time and a reception time of the communication frame transmitted / received by the redundant communication control unit to / from the other digital protection control device. The digital protection control device according to claim 5, wherein the time is synchronized by a difference between the two. The communication path is configured with a ring network topology,
The redundant communication control unit transmits the communication frame to the communication system determined by the communication system determination unit and receives the communication frame from the communication system to the other digital protection control device adjacent thereto. And
The time synchronization calculation unit calculates a communication delay time of the communication system of the communication frame transmitted and received by the redundant communication control unit as a path delay value, and calculates based on a transmission time and a reception time of the communication frame The digital protection control device according to claim 5, wherein the time is synchronized by a difference between a path delay value of the communication system and the time. The time synchronization calculation unit pre-calculates the path delay value for each communication system based on the time when the redundant communication control unit transmits and receives the communication frame for calculating the communication delay time, and the redundant communication control The digital protection control device according to claim 7, wherein a path delay value corresponding to the communication system of the communication frame transmitted and received by a unit is selected. Transmitting a communication frame including data used for protection of the power system to another digital protection control device connected via a plurality of redundant communication paths;
Of the communication frames transmitted to the communication path by the other digital protection control device, buffering the communication frame that arrives first in a memory and discarding the communication frame that arrives later;
Calculating a communication delay time of the communication path, calculating a delay sample number that guarantees continuity and simultaneity of the data; and
When the communication frame is received within the number of delay samples, the communication frame is used to perform an operation for protection of the power system, and a circuit breaker connected to the power system is controlled to control the power system. And a method of protecting the power system.

Images