JP6969150B2 - Time synchronization device, time synchronization method and time synchronization program - Google Patents

Description

The present invention relates to a network time synchronization technique.

IEEE1588PTP (Precision Time Protocol) is a protocol for synchronizing the time information of each device belonging to the network based on the reference time information. According to the time synchronization by IEEE1588PTP, each device of the network can be synchronized by distributing the time from the reference clock of the network. The reference clock is generally a high-precision clock using an atomic clock or GPS, but a low-precision reference clock may be sufficient for applications such as a protective relay of electric power equipment.

In order to ensure redundancy, multiple reference clocks may be prepared and connected to the network. Normally, time synchronization is performed using the reference clock with the highest priority or accuracy, but if the reference clock fails or cannot communicate, a spare reference clock is selected and time synchronization is performed. There is no problem if the time of the spare reference clock is correct, but the time value of a low-precision reference clock that is not time-synchronized may be inaccurate depending on the selection of the reference clock.

Japanese Unexamined Patent Publication No. 2009-11165

Generally, the reference clock of IEEE1588PTP distributes the standard time by using an atomic clock, GPS, or a high-precision crystal device. The priority of the reference clock can be set, and if a plurality of reference clocks are connected, the reference clock having the highest priority or accuracy is selected. If the reference clock fails or communication becomes impossible, another reference clock is selected and time synchronization is executed.

The reference clock may refer to GPS or an external clock, but it does not operate in synchronization with other reference clocks.

In a large-scale system, the cost is high because a plurality of expensive reference clocks are installed to ensure redundancy, but there are many cases where there is no problem even if the accuracy is low depending on the purpose of the system. For example, a protective relay of an electric power facility needs to measure a voltage and a current at a power supply frequency of 50 Hz or 60 Hz at a synchronized timing by time distribution, and the measurement timing is sufficient with an accuracy of several microseconds, and a standard time. There is no need to adjust to, and there is no problem with your own time axis. High-precision synchronization is possible by using GPS, but it becomes difficult to deal with security problems caused by jamming and satellite failures.

Therefore, if a crystal oscillator is applied to the reference clock, time synchronization can be performed at low cost, but since the crystal oscillator has low accuracy and individual differences in performance, switching of the reference clock may be hindered.

In view of the above circumstances, it is an object of the present invention to make the reference clock of the network inexpensively redundant.

Therefore, one aspect of the present invention is a time synchronization device that synchronizes the time of the internal clock of one device belonging to the network with the reference clock of the network, and the internal clock of the one device when the reference clock is abnormal. The synchronization processing unit that synchronizes the time with the internal clock of the other device having the highest priority as an alternative to the reference clock among all the devices belonging to the network, and the internal clock of the one device have the highest priority. In the case of a high internal clock, the clock switching unit is provided so that the internal clock can be used as a substitute for the reference clock when the reference clock is abnormal.

One aspect of the time synchronization device further includes a storage unit for storing the time information of the reference clock, and the synchronization processing unit stores the time information when the internal clock of the one device replaces the reference clock. The elapsed speed of the internal clock is corrected based on the time information.

One aspect of the synchronization processing unit is the elapsed speed of the internal clock at the time of synchronization of the internal clock when the internal clock of the one device is a substitute for the reference clock and the reference clock is normal. The elapsed speed is corrected so that the adjustment amount of is gradually approaching zero over time.

Further, one aspect of the present invention is a time synchronization method executed by a time synchronization device that synchronizes the internal clock of one device belonging to the network with the reference clock of the network, and is described above when the reference clock is abnormal. The process of synchronizing the time of the internal clock of one device with the internal clock of another device having the highest priority as an alternative to the reference clock among all the devices belonging to the network, and the internal clock of the one device are described above. When the internal clock has the highest priority, the internal clock has a process of substituting the reference clock when the reference clock is abnormal.

As another aspect of the present invention, there is a time synchronization program that causes the computer to function as the time synchronization device.

According to the above invention, the reference clock of the network can be made inexpensively redundant.

The block block diagram which exemplified the time synchronization system in embodiment of this invention. The block block diagram illustrating the time synchronization apparatus in the said embodiment. Difference in time change between the reference clock and its alternative internal clock. Time change of the internal clock before correction when the internal clock replaces the reference clock. Time change of the internal clock after correction when the internal clock replaces the reference clock.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Outline and configuration of this embodiment]
The time synchronization system 1 of the present embodiment shown in FIG. 1 is an example of a time synchronization system based on the IEEE1588 PTP (hereinafter, PTP) of the network 2.

The network 2 has a local network 3 to which the management server 30 belongs, a local network 4 to which a plurality of devices 6 belong, and a wide area network 5 connecting the local networks 3 and 4.

Each device 6 includes a time synchronization device 10 which is one aspect of the present invention. The time synchronization device 10 synchronizes the internal clock 61 of the device 6 belonging to the network 2 with the reference clock 31 of the network 2.

A configuration example of the time synchronization device 10 of the present embodiment shown in FIG. 2 will be described.

The time synchronization device 10 is a synchronization processing unit 11 and a clock switching unit 12 in cooperation with computer hardware resources (central processing unit, volatile storage unit, non-volatile storage unit, communication unit, etc.) and software resources. And the storage unit 13 is mounted.

When the reference clock 31 is abnormal, the synchronization processing unit 11 uses the internal clock 61 of the one device 6 as a substitute for the reference clock 31 among all the devices 6 belonging to the network 2. Synchronize the time with the internal clock 61.

Further, the synchronization processing unit 11 advances the internal clock 61 at the time of synchronization of the internal clock 61 when the internal clock 61 of the one device 6 is a substitute for the reference clock 31 and the reference clock 31 is normal. The elapsed speed is corrected so that the amount of speed adjustment gradually approaches zero over time.

The adjustment amount is defined as follows, for example. When the time synchronization process based on PTP is executed at the first timing T2_A, the time difference Diff_A between the reference clock 31 and the internal clock 61 can be obtained. Next, when the time synchronization process is executed at the second timing T2_B, the time difference Diff_B between the reference clock 31 and the internal clock 61 can be further obtained. Then, if the difference between the two obtained time differences is divided by the elapsed time of the first time and the second time as in the calculation formula of (adjustment amount per unit time) = (Diff_B-Diff_A) / (T2_B-T2_A). The difference in the inclination of the time change between the reference clock 31 and the internal clock 61 can be obtained. The value of this difference is an adjustment amount per unit time for matching the inclinations of the internal clock 61 and the reference clock 31.

The clock switching unit 12 causes the internal clock 61 to replace the reference clock 31 when the reference clock 31 is abnormal when the internal clock 61 of the one device 6 is the internal clock 61 having the highest priority.

The storage unit 13 stores an adjustment amount of the elapsed speed of the internal clock 61 when the time is synchronized with the reference clock 31. When the internal clock 61 of the one device 6 substitutes for the reference clock 31, the synchronization processing unit 11 corrects the elapsed speed of the internal clock 61 based on the time information of the reference clock 31 extracted from the storage unit 13. do.

[Operation example of this embodiment]
An operation example of this embodiment will be described below.

(1) Selection as an alternative to the reference clock 31 and handing over the time In the time synchronization system 1, normally, the time of the internal clock 61 of each device 6 belonging to the network 2 is networked by the synchronization processing unit 11 of the time synchronization device 10. Synchronize with the reference clock 31 of 2.

Here, when the reference clock 31 becomes abnormal, the clock switching unit 12 of the time synchronization device 10 of each device 6 has the highest priority as a substitute for the reference clock 31 among all the devices 6 belonging to the network 2. The internal clock 61 of the device 6 is used as a substitute for the reference clock 31. Then, the synchronization processing unit 11 of each device 6 synchronizes the time of the internal clock 61 of the device 6 with the time of the alternative internal clock 61.

A reference clock without an external reference or a low-precision reference clock may not be able to maintain accurate time with respect to other reference clocks. As described above, in the time synchronization system 1 of the present embodiment, the internal clock 61 having the highest priority, for example, the highest accuracy as the reference clock, is selected as an alternative to the reference clock 31. Then, when the selected internal clock 61 replaces the reference clock 31 of the network 2, the time information of the previous reference clock 31 that was normal is inherited. Therefore, even if the reference clock 31 of the network 2 becomes abnormal, the time of the network 2 is maintained accurately.

(2) Correspondence to the difference in the elapsed speed between the internal clocks 61 belonging to the network 2 The elapsed speed of the time has an individual difference among the plurality of internal clocks 61. In particular, when a relatively low-precision crystal device is applied to the internal clock 61, the error in the elapsed speed of time becomes large among the plurality of internal clocks 61.

For example, if the accuracy of the crystal is 10 ppm, there may be an error of up to 10 μsec for an accurate 1 second. The error occurs due to environmental factors such as temperature and voltage and individual differences, and it is considered that the two reference clocks installed at separate locations due to redundancy have a speed difference of 10 μsec per second.

When the reference clock 31 is switched to the alternative internal clock 61, as shown in FIG. 3, there is a gap due to a timeout of several seconds between the time passage of the reference clock 31 and the internal clock 61. Although the times of the reference clock 31 and the internal clock 61 are substantially the same, the time error increases between the time-outs because the elapsed speeds of the times are different.

Therefore, the adjustment amount of the elapsed speed of the internal clock 61 when the time is synchronized with the reference clock 31 is stored in advance in the storage unit 13. Then, when the internal clock 61 of the device 6 replaces the reference clock 31, the synchronization processing unit 11 of the device 6 corrects the elapsed speed of the internal clock 61 based on the adjustment amount drawn from the storage unit 13. As a result, as shown in FIG. 5, the elapsed speed of the reference clock 31 is increased by applying the adjustment amount of the internal clock 61 when the time is synchronized with the previous reference clock 31 which was normal. Since it is taken over, the error of several seconds of the timeout is minimized.

(3) Adjustment of the internal clock 61 over time When the functions of (1) and (2) above are executed, the network 2 is switched between the relatively low-precision reference clock 31 and its alternative internal clock 61. Times are not discontinuous.

However, when the switching is repeatedly executed, the adjustment amount per unit time is inherited, so that the speed may gradually deviate from the accurate elapsed speed of the time.

Therefore, when the internal clock 61 of the device 6 replaces the reference clock 31, the synchronization processing unit 11 of the device 6 takes over the adjustment amount of the internal clock 61, and as shown in FIG. 4, this The elapsed speed of the internal clock 61 is corrected so that the adjustment amount gradually approaches zero over time. That is, when the adjustment amount becomes zero, the time is delivered in 1 second by the crystal device of the internal clock 61, so that the elapsed speed does not deviate from 1 second. Therefore, even when the reference clock 31 is replaced, it is possible to avoid a hindrance to the linkage of the device 6 belonging to the network 2.

As described above, according to the time synchronization system 1 of the present embodiment, the time synchronization is executed, so that the time value of the reference clock 31 continues even if the internal clock 61 of the device 6 substitutes for the reference clock 31.

In particular, even if a crystal device having an individual difference in the elapsed speed of time is applied to the internal clock 61 and the reference clock 31, and the internal clock 61 of the device 6 substitutes for the reference clock 31 of the network 2, the elapse of the reference clock 31 The speed is taken over.

Further, since the adjustment amount of the elapsed speed of the internal clock 61 is gradually adjusted until it becomes zero, the adjustment amount does not deviate even if the replacement of the reference clock 31 is repeated, and the linkage of the device 6 belonging to the network 2 is stable. Can be maintained.

Further, since a relatively inexpensive crystal device can be applied to the reference clock 31 and the internal clock 61, the redundancy of the reference clock of the network 2 can be realized at low cost.

Another aspect of the present invention can be realized by configuring a program that causes a computer to function as a part or all of the time synchronization device 10 and causing the computer to execute the program. Alternatively, it can be realized by configuring a program that causes a computer to execute a part or all of the process of the time synchronization method executed by the time synchronization device 10, and causing the computer to execute the program. Then, this program (time synchronization program) can be stored and provided in a well-known recording medium readable by the computer. Alternatively, the program can be provided via a network via the Internet, e-mail, or the like.

The present invention is not limited to the above embodiments, and can be implemented in various embodiments within the scope of the claims of the present invention.

1 ... Time synchronization system 2 ... Network, 31 ... Reference clock 6 ... Device, 61 ... Internal clock 10 ... Time synchronization device, 11 ... Synchronization processing unit, 12 ... Clock switching unit, 13 ... Storage unit

Claims (4)

A time synchronization device that synchronizes the internal clock of one device belonging to a network with the reference clock of the network.
If the internal clock of the one device is not the internal clock of the device having the highest priority as a substitute for the reference clock among all the devices belonging to the network, the inside of the one device when the reference clock is abnormal. a synchronization processing unit for internal clock time synchronization of the high priority device clock,
When the internal clock of the one device is the internal clock having the highest priority, a clock switching unit that substitutes the internal clock for the reference clock when the reference clock is abnormal, and a clock switching unit.
A storage unit for storing the adjustment amount per unit time of the time value of the internal clock represented by the difference between the slope of the time variation of the internal clock of the reference clock and time synchronization is the reference clock and the one device when allowed
Equipped with
The synchronization processing unit is a device having a high priority based on the adjustment amount drawn from the storage unit of the device having a high priority when the internal clock of the device having a high priority replaces the reference clock. A time synchronization device characterized by correcting the elapsed speed of the time value of the internal clock of. The synchronization processing unit determines the time value of the internal clock at the time of synchronization of the internal clock when the reference clock is normal when the internal clock of the high-priority device replaces the reference clock. time synchronization apparatus of claim 1, the adjustment amount per unit time and corrects the elapsed velocity time value of the internal clock so as to approach zero gradually over time. A time synchronization method executed by a time synchronization device that synchronizes the internal clock of one device belonging to a network with the reference clock of the network.
If the internal clock of the one device is not the internal clock of the device having the highest priority as a substitute for the reference clock among all the devices belonging to the network, the inside of the one device when the reference clock is abnormal. a process for internal clock and the time synchronization of the high priority device clock,
And process the internal clock to the internal clock and alternate the reference clock when the reference clock is abnormal when the is the highest priority internal clock of said one device,
The amount of adjustment of the time value of the internal clock, which is indicated by the difference in the inclination of the time change between the reference clock and the internal clock of the one device when the time is synchronized with the reference clock, is stored in the storage unit . The process and
Have a,
The time synchronization process has a high priority based on the adjustment amount drawn from the storage unit of the high priority device when the internal clock of the high priority device replaces the reference clock. A time synchronization method characterized by correcting the elapsed speed of the time value of the internal clock of the device. A time synchronization program that causes a computer to function as the time synchronization device according to claim 1 or 2.

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