JP4543836B2 - Time synchronization method for data processing system - Google Patents

Description

  The present invention relates to a time synchronization method for synchronizing time between units in a master / slave data processing system in which a master server and a number of slave units are network-connected.

  In recent years, with the spread of networks such as Ethernet (registered trademark), digital relays have been networked using information transmission between a plurality of measurement control units distributed in various places and a central monitoring control unit. Yes. Since long distance transmission is possible with Ethernet, a wide range of digital relays can be networked.

  When a plurality of digital relays (units) are installed in a power system such as a power distribution system, voltage / current at that location is measured, and an event occurring in the power system is analyzed from these measurement information, one in the network Or it is common to provide a plurality of servers and collect and analyze data from a plurality of units.

  If the data collected from the units is time-series and correlated, it is necessary to synchronize the time information between the units. To enable this, as shown in FIG. In a system in which the slaves 2A to 2X are connected by Ethernet and perform data communication by the master / slave method, a time synchronization method is proposed in which time information of the master clock device 1A held by the master is transmitted to each slave ( For example, see Patent Document 1).

  In addition, a method of switching the synchronization time to an arbitrary time by the master / slave method has been proposed (for example, see Patent Document 2).

Another time synchronization method uses a GPS (Global Positioning System) (see, for example, Patent Document 3). In this patent document 3, as shown in FIG. 7, the time information received by the GPS receiver 3 and synthesized by the time distributor 4 is distributed to the terminal devices 5A to 5N through the optical transmission system. In this method, time synchronization is obtained between the terminal devices, and one device is in charge of receiving time information and generating a time synchronization signal.
JP 2000-224766 A JP 2001-305256 A JP 2001-221874 A

  As described above, in a digital relay system or the like, when time series data measured by a plurality of units is collected in a server and analysis including the correlation of the data is performed, the time between the units needs to be synchronized. There is.

  In this time synchronization, GPS is used in Patent Document 3, but GPS may not be able to capture radio waves from a satellite necessary for time synchronization due to the installation in a bad environment or the influence of bad weather. Will lose the time synchronization function.

  When the time synchronization function by GPS is lost, it is conceivable to switch to a method of distributing the master clock information possessed by the master to each slave as in Patent Document 1. However, in this method, since the master mainly performs data processing for time synchronization (data calculation and communication for obtaining the synchronization time), the load on the master is increased for individual time synchronization processing for a large number of slaves. End up.

  An object of the present invention is to provide a time synchronization method of a data processing system that solves the above problems.

  In the present invention, in order to solve the above-mentioned problem, the server and each unit acquire time information from GPS to enable time synchronization, and when only the unit becomes unable to perform time synchronization by GPS, the server Time synchronization is obtained by network communication with the server based on the time information obtained from the GPS, and if the server cannot obtain the time information from the GPS, the time information of the internal clock of the server is broadcast to all units simultaneously. Thus, time synchronization is obtained, and the following method is characterized.

(1) A time synchronization method for synchronizing the time between units in a master / slave type data processing system in which a master server and a number of slave units are network-connected,
The server and each unit normally receive time information from GPS individually, set this time information in each internal clock to obtain time synchronization between the server and the unit,
When the time information cannot be obtained from the GPS, each unit transmits a “time transmission request” to the server at a fixed cycle via the network, and stores the time (t11) of the internal clock at that time. Aside,
The server transmits the time (t21) at which the “time transmission request” is received from the unit and the current time (t22) of the server itself to the unit via the network,
The unit obtains the time (t12) when the times (t21) and (t22) are received from the server, calculates the theoretical central times (t13) and (t23) of the unit and the server, and calculates the time ( The difference (t13-t23) between t13) and (t23) is calculated as a time lag, and the unit's own internal clock is corrected with this time lag .
The server receives the “time transmission request” from the unit, acquires the current time of the server itself when the time information acquisition from the GPS is impossible, and broadcasts the current time to all the units simultaneously. Send
Each unit sets its own internal clock at the current time received by the broadcast from the server .

(2) A time synchronization method for synchronizing the time between units in a master / slave type data processing system in which a master server and a number of slave units are network-connected,
The server and each unit normally receive time information from GPS individually, set this time information in each internal clock to obtain time synchronization between the server and the unit,
When the time information cannot be obtained from the GPS, each unit transmits a “time transmission request” to the server at a fixed cycle via the network, and stores the time (t11) of the internal clock at that time. Aside,
When the server receives a “time transmission request” from the unit, the server transmits the current time (t23) of the server itself to the unit via the network,
The unit calculates a time difference (d1) from the transmitted time (t11) and the time (t12) when the current time is received from the server to the theoretical central time (t13), and the current time (t23) of the server ) To add the time difference (d1) to correct the unit's own internal clock ,
The server receives the “time transmission request” from the unit, acquires the current time of the server itself when the time information cannot be acquired from the GPS, and broadcasts the current time to all the units simultaneously. Send
Each unit sets its own internal clock at the current time received from the server by the simultaneous broadcast .

  As described above, according to the present invention, the server and each unit acquire time information from GPS to enable time synchronization, and when only the unit becomes unable to perform time synchronization by GPS, the server Based on the obtained time information, time synchronization is obtained by network communication with the server, and when the server cannot obtain the time information from GPS, the time information of the internal clock of the server is broadcast to all units simultaneously. Since time synchronization is obtained, when time synchronization by GPS becomes impossible due to some influence, time synchronization can be obtained by network communication between the unit and the server. Moreover, the time synchronization processing in the server only needs to transmit the current time of the server itself to the unit in response to the reception of the time transmission request from the unit, and most of the time synchronization processing is performed on the unit side. , The burden on the server can be reduced.

(Embodiment 1)
As a system configuration for realizing the present embodiment, in the master-slave system of FIG. 6, a GPS receiver is provided in each of the server as the master 1 and the units as the slaves 2 </ b> A to 2 </ b> X. Normally, time information from GPS is received individually, and time synchronization between units is made possible based on this time information. In this state, the master can acquire time information from GPS. When the time information acquisition from GPS becomes impossible, the time synchronization function is secured by Ethernet communication between the server and the unit.

  FIG. 1 shows a flowchart of time synchronization by cooperative processing between a server and each slave, and FIG. 2 shows a time relationship for time synchronization between the server and each unit. The time synchronization method will be described in detail below with reference to these.

  When each unit determines that time synchronization using GPS is possible (S1), it sets the time received from GPS as an internal clock and ensures time synchronization between units (S2).

  When the time synchronization using GPS becomes impossible, each unit transmits a “time transmission request” to the server at regular intervals via the Ethernet, and stores the time (t11) of the internal clock at that time. (S3).

  After saving the time (t21) when the “time transmission request” is received, the server acquires the current time of the server itself, stores the time when returning to the unit as (t22), and stores the time (t21) and ( t22) is transmitted to the unit (S4).

  In the unit, the time (t12) when the current time is received from the server is acquired and stored (S5), and then the theoretical center time (t13) and ( t23) is calculated (S6, S7).

  In the unit, the difference between the times (t13) and (t23) is calculated as the theoretical center time difference (t13-t23) between the unit and server (S8), and the internal clock of the unit itself is corrected by this time difference. Thus, time synchronization is obtained (S9).

  Therefore, when the unit becomes unable to synchronize time with GPS, the unit can obtain time synchronization with GPS through Ethernet communication with a server capable of acquiring time information with GPS. In addition, the time synchronization processing in the server transmits the time t21 when the time transmission request from the unit is received and the current time t22 of the server itself to the unit, and most of the time synchronization processing is performed on the unit side. , The burden on the server can be reduced.

(Embodiment 2)
In the present embodiment, as in the first embodiment, the server and each unit normally receive time information from the GPS at normal times, and the time synchronization between the units is made possible based on this time information. The master can acquire the time information from the GPS, but when the unit becomes unable to acquire the time information from the GPS, the time synchronization function is secured by Ethernet communication between the server and the unit.

  FIG. 3 is a flowchart of time synchronization by cooperative processing between the server and each slave, and FIG. 4 shows the time relationship for time synchronization between the server and each unit. The time synchronization method will be described in detail below with reference to these.

  As in the first embodiment, when each unit determines that time synchronization using GPS is possible (S11), the time received from GPS is set as an internal clock to ensure time synchronization between units ( S12) When time synchronization using GPS becomes impossible, a “time transmission request” is transmitted to the server via the Ethernet at a constant cycle, and the time (t11) of the internal clock at that time is stored (S12). S13).

  When the server receives a “time transmission request” from the unit, the server returns the current time (t23) of the server itself to the unit (S14).

  The unit acquires and stores the time (t12) when the current time is received from the server (S15). Next, a time difference (d1) to the theoretical center time (t13) is calculated according to the arithmetic expression shown in FIG. 4 (S16). Finally, on the assumption that the theoretical center time (t13) and the current time of the server are the same, the unit adds the time difference (d1) to the received current time (t23) of the server. Is reset to obtain time synchronization (S17).

  Therefore, also in this embodiment, when a unit becomes unable to synchronize time by GPS, the unit can obtain time synchronization by GPS by Ethernet communication with a server capable of acquiring time information by GPS. Further, the time synchronization processing in the server only needs to transmit the current time t22 of the server itself to the unit when the time transmission request from the unit is received, and the load on the server can be reduced.

(Embodiment 3)
In the present embodiment, as in the first and second embodiments, the server and each unit individually receive time information from the GPS, and time synchronization between the units is enabled based on this time information. This embodiment is different from the first and second embodiments in that the time synchronization function is secured by Ethernet communication between the server and the unit when the master and the unit cannot acquire time information from the GPS.

  FIG. 5 shows a flowchart of time synchronization by the cooperative processing of the server and each slave. As in the first or second embodiment, when the unit becomes unable to acquire time information from the GPS, transmits a time transmission request to the server, and the server receives the time transmission request, the server itself receives the time information from the GPS. It is checked whether or not acquisition is possible (S21). In this check, if the server can acquire time information from GPS, the server transmits the time information acquired from GPS to the unit. The unit to which this information is transmitted sets time information from GPS as an internal clock, and obtains time synchronization based on the GPS time information (S22).

  On the other hand, when both the unit and the server become unable to synchronize with the GPS (S21), the server transmits its current time (t23) to all the units in a simultaneous broadcast of Ethernet (S23). Each unit that has received this time (t23) resets its current time to the time (t23) (S24), and obtains time synchronization based on the server time between the units.

  Accordingly, in the present embodiment, as in the first and second embodiments, when the unit becomes unable to acquire time information by GPS, time synchronization can be obtained by Ethernet communication with the server. In addition to this, in the present embodiment, the time synchronization function by the clock of the server can be secured even when the unit and the server both cannot acquire the time information from the GPS. In this case as well, the server process only needs to check whether or not GPS synchronization is possible, and to send its current time to all units in a simultaneous broadcast, and the burden can be reduced.

The time synchronization flowchart which shows Embodiment 1 of this invention. The time relationship of Embodiment 1. FIG. The flowchart of the time synchronization which shows Embodiment 2 of this invention. The time relationship of Embodiment 2. The flowchart of the time synchronization which shows Embodiment 3 of this invention. The system block diagram of a master / slave system. The system block diagram of a GPS system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Master 1A Internal clock 2A, 2X Slave 3 GPS receiver 4 Time distribution device 5A, 5B, 5N Terminal device

Claims (2)

A time synchronization method for synchronizing the time between units in a master / slave data processing system in which a master server and a number of slave units are network-connected,
The server and each unit normally receive time information from GPS individually, set this time information in each internal clock to obtain time synchronization between the server and the unit,
When the time information cannot be obtained from the GPS, each unit transmits a “time transmission request” to the server at a fixed cycle via the network, and stores the time (t11) of the internal clock at that time. Aside,
The server transmits the time (t21) at which the “time transmission request” is received from the unit and the current time (t22) of the server itself to the unit via the network,
The unit obtains the time (t12) when the times (t21) and (t22) are received from the server, calculates the theoretical central times (t13) and (t23) of the unit and the server, and calculates the time ( The difference (t13-t23) between t13) and (t23) is calculated as a time lag, and the unit's own internal clock is corrected with this time lag .
The server receives the “time transmission request” from the unit, acquires the current time of the server itself when the time information acquisition from the GPS is impossible, and broadcasts the current time to all the units simultaneously. Send
A time synchronization method for a data processing system, wherein each unit sets its own internal clock at the current time received from the server by the simultaneous broadcast . A time synchronization method for synchronizing the time between units in a master / slave data processing system in which a master server and a number of slave units are network-connected,
The server and each unit normally receive time information from GPS individually, set this time information in each internal clock to obtain time synchronization between the server and the unit,
When the time information cannot be obtained from the GPS, each unit transmits a “time transmission request” to the server at a fixed cycle via the network, and stores the time (t11) of the internal clock at that time. Aside,
When the server receives a “time transmission request” from the unit, the server transmits the current time (t23) of the server itself to the unit via the network,
The unit calculates a time difference (d1) from the transmitted time (t11) and the time (t12) when the current time is received from the server to the theoretical central time (t13), and the current time (t23) of the server ) To add the time difference (d1) to correct the unit's own internal clock ,
The server receives the “time transmission request” from the unit, acquires the current time of the server itself when the time information cannot be acquired from the GPS, and broadcasts the current time to all the units simultaneously. Send
A time synchronization method for a data processing system, wherein each unit sets its own internal clock at the current time received from the server by the simultaneous broadcast .

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