Distribution network EPON differential protection sampling synchronization method and device

Abstract

The invention discloses a distribution network EPON differential protection sampling synchronization method and device, and the method comprises the steps: 1, a first power distribution device transmits a first synchronization message, and broadcasts the first synchronization message to an EPON network; 2, after receiving the first synchronous message sent by the first power distribution device through the EPON network, the second to Nth power distribution devices record the packet receiving time of the first synchronous message based on the own crystal oscillator clocks of the devices, send a second synchronous message, and send the second synchronous message to the EPON network in a broadcast mode; and step 3, the second to Nth power distribution devices receive a second synchronization message pushed by other devices, and based on the packet receiving time in the second synchronization message, the second synchronization message is matched with the packet receiving time recorded by the second synchronization message, so that sampling synchronization is realized. According to the method, sampling synchronization can be achieved based on the characteristics of the EPON, the synchronization scheme is high in reliability, the method is suitable for various common EPON devices, the method is small in calculation amount and high in universality, and the reliability and adaptability of the differential protection function applied to the power distribution network are effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of relay protection of power systems, and more specifically, to a distribution network EPON differential protection sampling synchronization method and device. Background Art

[0002] DTU (Distribution Terminal Unit) and FTU (Feeder Terminal Unit) are important devices in the distribution network, used to collect and calculate the data of the primary quantity in the power grid. Due to the disadvantages of the traditional overcurrent protection principle of the distribution network, such as complex setting, large power outage range, long delay, and easy over-tripping, the current DTU and FTU devices add differential protection principles in the design to more accurately locate and quickly isolate the fault point.

[0003] The realization of differential protection principle requires adjacent devices in the distribution network to realize the two functions of transmitting sampling data to each other and synchronizing the sampling data at both ends. In the newly built distribution network, optical cables are generally laid. Considering the complex structure of the distribution network, the use of EPON technology to realize the networking between the terminals of the distribution network has become a solution for the application of differential protection function in the distribution network.

[0004] Compared with wireless communication solutions such as 5G, EPON network (Ethernet Passive Optical Network) has the advantages of high bandwidth, low latency, stable communication, and no need to pay for traffic and bandwidth usage. Compared with fiber-optic communication, EPON's star networking method is relatively fixed, which can be adapted to various distribution network structures and has strong versatility. However, the uplink of EPON network needs to operate based on time division multiplexing mode, and the end-to-end communication delay is not fixed. Therefore, the ping-pong synchronization method generally used in the fiber differential protection function, that is, the sampling synchronization of both sides is achieved based on link delay measurement. This method cannot be used in networks with unstable communication delay.

[0005] For networks with unstable link delays, the industry currently designs synchronization solutions based on unified clock signals. Clock signals are generally implemented using satellite timing (such as GPS timing), which requires additional configuration of timing source equipment or hardware with related functions, and the cost of use is high. If synchronization is based on analog signals on the distribution network line, such as synchronization based on the moment of failure or synchronization based on the comparison of voltage phases on both sides during normal operation, these electrical quantity synchronization solutions have certain limitations on application scenarios, and their reliability and versatility are relatively low. Summary of the invention

[0006] In order to solve the deficiencies in the prior art, the present invention provides a distribution network EPON differential protection sampling synchronization method, which can solve the technical problem of realizing distribution network EPON differential sampling synchronization by relying only on the EPON network itself.

[0007] The present invention adopts the following technical solution.

[0008] A distribution network EPON differential protection sampling synchronization method comprises the following steps:

[0009] Step 1: The first power distribution device sends a first synchronization message, and broadcasts the first synchronization message to the EPON network;

[0010] Step 2, after receiving the first synchronization message sent by the first distribution device through the EPON network, the second to Nth distribution devices record the packet receiving time of the first synchronization message based on the device's own crystal oscillator clock, and send a second synchronization message to the EPON network by broadcasting;

[0011] Step 3: The second to Nth power distribution devices receive the second synchronization message pushed by other devices, and based on the packet receiving time therein, match it with the packet receiving time recorded by themselves to achieve sampling synchronization.

[0012] Preferably, in step 1, the first synchronization message includes the address and serial number of the first power distribution device, and the destination address is a broadcast address.

[0013] Preferably, in step 2, the crystal oscillator clock of all power distribution devices themselves is a timer implemented based on the device's own hardware crystal oscillator.

[0014] Preferably, in step 2, the second synchronization message includes the address of the first power distribution device, the sequence number in the first synchronization message, the address of the device, the reception time when the device receives the first synchronization message sent by the first power distribution device, and the destination address is a broadcast address.

[0015] Preferably, in step 3, for the i-th and j-th power distribution devices, the sampling synchronization method is as follows:

[0016] (1) The jth distribution device receives the second synchronization message sent by the ith distribution device, and extracts the message receiving time Ti, where i, j∈[2, N];

[0017] (2) The jth power distribution device finds the receiving time Tj of the first synchronization message of this frame recorded by itself according to the address of the first power distribution device in the second synchronization message and the sequence number in the first synchronization message;

[0018] (3) When the third power distribution device receives the sampled data sent by the second power distribution device, it calculates the timestamp Taj corresponding to the crystal oscillator clock of the jth power distribution device based on the sampling timestamp Tai:

[0019] Taj=Tai-Ti-Tdi+Tj-Tdj

[0020] Wherein, Tdi is the communication delay from the i-th power distribution device to the OLT in the EPON network, and Tdj is the communication delay from the j-th power distribution device to the OLT in the EPON network;

[0021] (4) Based on the sampling data of multiple i-th distribution devices and the converted sampling timestamps, the sampling data of the i-th distribution device at the same time when the j-th distribution device itself samples is calculated by Lagrange parabola interpolation method.

[0022] Preferably, steps 1-3 are repeated to calculate the timestamp Taj corresponding to the crystal oscillator clock of the jth device based on the receiving times {Ti1, Tj1} and {Ti2, Tj2} of the i-th and j-th distribution devices obtained the last two times and the sampling timestamp Tai in the sampled data sent by the i-th distribution device:

[0023] Taj=(Tai-Ti2-Tdi)×(Tj2-Tj1) / (Ti2-Ti1)+(Tj2-Tdj)

[0024] Preferably, there are at least three power distribution devices in the EPON network.

[0025] Preferably, the first power distribution device is arranged at the uplink port of the EPON network to realize master-slave synchronization for all power distribution devices in the EPON network; or the first power distribution device is arranged in the EPON network to realize mutual synchronization for other power distribution devices to realize peer-to-peer synchronization.

[0026] Preferably, if the first power distribution device itself cannot be synchronized with other power distribution devices, each device in the EPON network takes turns to serve as the first power distribution device to achieve sampling synchronization among all power distribution devices in the EPON network.

[0027] The present invention also proposes a distribution network EPON differential protection sampling synchronization device, comprising: a sampling module, a sampling synchronization module, and a message transceiver module;

[0028] The sampling module is used to regularly collect the current and voltage data connected to the device;

[0029] The sampling synchronization module is used to perform timestamp conversion on the sampling data of other devices, as well as Lagrange interpolation resampling synchronization function;

[0030] The message transceiver module is used to send the sampled data, the first and second synchronization messages to other devices, and receive messages sent by other devices.

[0031] The beneficial effect of the present invention is that, compared with the prior art, the present invention provides a method for sampling synchronization of EPON differential protection in a distribution network, which can realize sampling synchronization based on the characteristics of the EPON network itself in a distribution network differential application scenario based on the EPON network, and the algorithm does not rely on external devices such as external timing sources, nor does it need to be based on the characteristics of the distribution network line. The synchronization scheme has high reliability and is applicable to various types of commonly used EPON network equipment, and does not require customized modification of the EPON network equipment. The method has a small amount of calculation and high universality, and effectively improves the reliability and adaptability of the differential protection function in the distribution network application. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of a method for sampling synchronization of EPON differential protection in a distribution network in the present invention;

[0033] Figure 2 It is a system structure diagram of a distribution network EPON differential protection sampling synchronization device in the present invention. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only part of the embodiments of the present invention, not all of them. Based on the spirit of the present invention, other embodiments obtained by ordinary technicians in this field without creative work are all within the scope of protection of the present invention.

[0035] like Figure 1 As shown, the present invention proposes a distribution network EPON differential protection sampling synchronization method, which is applicable to the case where there are at least three distribution devices in the EPON network. When there are only two distribution devices in the EPON network, the optical fiber direct connection method can be used to directly implement sampling synchronization based on the ping-pong method;

[0036] The sampling synchronization method proposed by the present invention comprises the following steps:

[0037] Step 1: The first power distribution device sends a first synchronization message and broadcasts it to the EPON network;

[0038] The first synchronization message includes the address and serial number of the first power distribution device, and the first synchronization message is broadcast to the EPON network.

[0039] Preferably, the first power distribution device can be placed on the uplink port of the EPON network to achieve master-slave synchronization for all power distribution devices in the EPON network, and can also exist in the EPON network to achieve mutual synchronization for other power distribution devices to achieve peer-to-peer synchronization.

[0040] Furthermore, the power distribution device sends and receives messages via the EPON network.

[0041] The equipment required for constructing the EPON network in the present invention includes ONU (Optical Network Unit), OLT (Optical Line Terminal) and splitter;

[0042] ONU is used to connect the power distribution interruption device to the EPON network. An ONU is configured in each power distribution interruption device, and messages are sent and received through the ONU;

[0043] OLT is the core of EPON network. An EPON network consists of an OLT and several ONUs. All ONUs are connected to OLT through optical fiber.

[0044] The EPON network uses a splitter to split a single optical fiber into multiple optical fibers, so that one OLT can connect multiple ONUs with optical fibers.

[0045] Step 2, after receiving the first synchronization message sent by the first distribution device, the second to Nth power distribution devices record the packet receiving time of the first synchronization message based on the device's own crystal oscillator clock, and send a second synchronization message to the EPON network by broadcasting;

[0046] The crystal oscillator clock of all power distribution devices is a timer based on the device's own hardware crystal oscillator;

[0047] The second synchronization message includes the address of the first power distribution device, the sequence number in the first synchronization message, the address of the local device, the packet receiving time of the first synchronization message, and the destination address is a broadcast address.

[0048] The second to Nth power distribution devices receive the first synchronization message respectively, and the second synchronization message sent by the i-th power distribution device includes the packet receiving time Ti of the first synchronization message, and i∈[2,N].

[0049] The first power distribution device, as the initiator, sends a first synchronization message. After receiving the first synchronization message, other power distribution devices send a frame of second synchronization message. A total of (N-1) second synchronization messages are broadcast and sent.

[0050] Step 3, the second to Nth power distribution devices receive the second synchronization message pushed by other devices, and based on the packet receiving time of the first synchronization message in the second synchronization message, match it with the packet receiving time recorded by itself to achieve sampling synchronization.

[0051] The second to Nth power distribution devices are capable of receiving second synchronization messages broadcasted by other devices except themselves, and performing sampling synchronization on each received second synchronization message;

[0052] For the i-th and j-th distribution devices, the sampling synchronization method is as follows:

[0053] (1) The jth distribution device receives the second synchronization message sent by the ith distribution device, and extracts the message receiving time Ti, where i, j∈[2, N];

[0054] (2) The jth power distribution device finds the receiving time Ti of the first synchronization message of this frame recorded by itself according to the address of the first power distribution device in the second synchronization message and the sequence number in the first synchronization message;

[0055] (3) When the third power distribution device receives the sampled data sent by the second power distribution device, it calculates the timestamp Taj corresponding to the crystal oscillator clock of the jth power distribution device based on the sampling timestamp Tai in the sampled data:

[0056] Taj=Tai-Ti-Tdi+Tj-Tdj

[0057] Wherein, Tdi is the communication delay from the i-th distribution device to the OLT, and Tdj is the communication delay from the j-th distribution device to the OLT. The communication delay is calculated by measuring the distance from the distribution device to the OLT, and can also be estimated by the optical fiber length at a ratio of 2km / 10us.

[0058] (4) Based on the sampling data of multiple i-th distribution devices and the converted sampling timestamps, the sampling data of the i-th distribution device at the same time when the j-th distribution device itself samples is calculated by Lagrange parabola interpolation method.

[0059] Specifically, taking the second and third power distribution devices as an example, the sampling synchronization method is as follows:

[0060] (1) The third power distribution device receives the second synchronization message sent by the second power distribution device, and extracts the packet receiving time T2 of the first synchronization message in the second synchronization message sent by the second power distribution device;

[0061] (2) The third power distribution device finds the receiving time T3 of the first synchronization message of this frame recorded by itself according to the address of the first power distribution device in the second synchronization message and the sequence number in the first synchronization message;

[0062] (3) When the third power distribution device receives the sampled data sent by the second power distribution device, it calculates the timestamp Ta3 corresponding to the crystal oscillator clock of the device based on the sampling timestamp Ta2 of the sampled data:

[0063] Ta3=Ta2-T2-Td2+T3-Td3

[0064] Wherein, Td2 is the communication delay from the second power distribution device to the OLT in the EPON network, and Td3 is the communication delay from the third power distribution device to the OLT. The communication delay is calculated by measuring the distance from the power distribution device to the OLT, and can also be estimated by the optical fiber length at a ratio of 2km / 10us;

[0065] (4) Based on the sampling data of multiple second power distribution devices and the timestamp Ta3 corresponding to the crystal oscillator clock of the device obtained after conversion, the sampling data of the second power distribution device at the same time when the third power distribution device itself samples each time is calculated by Lagrange parabola interpolation method.

[0066] Further preferably, in the synchronization method of the present invention, if the first power distribution device itself cannot be synchronized with other power distribution devices, each device in the network can take turns to be the first power distribution device, thereby achieving sampling synchronization between all power distribution devices in the EPON network;

[0067] Due to the complex topology of the distribution network, each distribution terminal needs to be networked with multiple other distribution terminal devices to realize the differential function. Therefore, each distribution terminal can simultaneously support the realization of all the functions of the above steps 1-3 with multiple other devices.

[0068] like Figure 2 As shown, the present invention also proposes a distribution network EPON differential protection sampling synchronization device, including: a sampling module, a sampling synchronization module, and a message transceiver module;

[0069] The sampling module is used to regularly collect the current and voltage data connected to the device;

[0070] The sampling synchronization module is used to perform timestamp conversion on the sampling data of other devices, as well as Lagrange interpolation resampling synchronization function;

[0071] The message transceiver module is used to send the sampled data, the first and second synchronization messages to other devices, and receive messages sent by other devices.

[0072] The beneficial effect of the present invention is that, compared with the prior art, the present invention can realize sampling synchronization based on the characteristics of the EPON network itself, the synchronization scheme has high reliability, does not need to rely on external equipment, and is applicable to various commonly used EPON network equipment. The method has small calculation amount and high universality, and effectively improves the reliability and adaptability of the differential protection function in the distribution network application.

[0073] The present disclosure may be a system, a method and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0074] Computer readable storage medium can be a tangible device that can keep and store instructions used by instruction execution device. Computer readable storage medium can be, for example, but not limited to, electrical storage device, magnetic storage device, optical storage device, electromagnetic storage device, semiconductor storage device or any suitable combination of the above. More specific examples (non-exhaustive list) of computer readable storage medium include: portable computer disk, hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disk read-only memory (CD-ROM), digital versatile disk (DVD), memory stick, floppy disk, mechanical encoding device, such as punch card or convex structure in groove with instructions stored thereon, and any suitable combination of the above. Computer readable storage medium used here is not interpreted as instantaneous signal itself, such as radio wave or other free propagating electromagnetic wave, electromagnetic wave propagated by waveguide or other transmission medium (for example, light pulse by optical fiber cable) or electrical signal transmitted by wire.

[0075] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network can include copper transmission cables, optical fiber transmissions, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers. The network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in the computer-readable storage medium in each computing / processing device.

[0076] The computer program instructions for performing the operation of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-related instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages-such as Smalltalk, C++, etc., and conventional procedural programming languages-such as "C" language or similar programming languages. Computer-readable program instructions may be executed completely on a user's computer, partially on a user's computer, as an independent software package, partially on a user's computer, partially on a remote computer, or completely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer via any type of network-including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., using an Internet service provider to connect via the Internet). In some embodiments, an electronic circuit, such as a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA) may be personalized by utilizing the state information of a computer-readable program instruction, and the electronic circuit may execute a computer-readable program instruction, thereby realizing various aspects of the present disclosure.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A distribution network EPON differential protection sampling synchronization method, characterized in that: The following steps are involved: Step 1: The first power distribution device sends a first synchronization message, and broadcasts the first synchronization message to the EPON network; Step 2, after receiving the first synchronization message sent by the first distribution device through the EPON network, the second to Nth distribution devices record the packet receiving time of the first synchronization message based on the device's own crystal oscillator clock, and send a second synchronization message to the EPON network by broadcasting; Step 3: The second to Nth power distribution devices receive the second synchronization message pushed by other devices, and based on the packet receiving time therein, match it with the packet receiving time recorded by themselves to achieve sampling synchronization.

2. The distribution network EPON differential protection sampling synchronization method according to claim 1, characterized in that: In step 1, the first synchronization message includes the address and serial number of the first power distribution device, and the destination address is a broadcast address.

3. The distribution network EPON differential protection sampling synchronization method according to claim 1, characterized in that: In step 2, the crystal oscillator clock of all power distribution devices is a timer implemented based on the device's own hardware crystal oscillator.

4. The distribution network EPON differential protection sampling synchronization method according to claim 1, characterized in that: In step 2, the second synchronization message includes the address of the first power distribution device, the sequence number in the first synchronization message, the address of the device, the reception time when the device receives the first synchronization message sent by the first power distribution device, and the destination address is a broadcast address.

5. The distribution network EPON differential protection sampling synchronization method according to claim 1, characterized in that: In step 3, for the i-th and j-th power distribution devices, the sampling synchronization method is as follows: (1) The jth distribution device receives the second synchronization message sent by the ith distribution device, and extracts the message receiving time Ti, where i, j∈[2, N]; (2) The jth power distribution device finds the receiving time Tj of the first synchronization message of this frame recorded by itself according to the address of the first power distribution device in the second synchronization message and the sequence number in the first synchronization message; (3) When the third power distribution device receives the sampled data sent by the second power distribution device, it calculates the timestamp Taj corresponding to the crystal oscillator clock of the jth power distribution device based on the sampling timestamp Tai: Taj=Tai-Ti-Tdi+Tj-Tdj Wherein, Tdi is the communication delay from the i-th power distribution device to the OLT in the EPON network, and Tdj is the communication delay from the j-th power distribution device to the OLT in the EPON network; (4) Based on the sampling data of multiple i-th distribution devices and the converted sampling timestamps, the sampling data of the i-th distribution device at the same time when the j-th distribution device itself samples is calculated by Lagrange parabola interpolation method.

6. The distribution network EPON differential protection sampling synchronization method according to claim 1, characterized in that: Repeat steps 1-3, based on the last two received times {Ti1, Tj1} and {Ti2, Tj2} of the i-th and j-th distribution devices, and based on the sampling timestamp Tai in the sampled data sent by the i-th distribution device, calculate the timestamp Taj corresponding to the crystal oscillator clock of the j-th device: Taj=(Tai-Ti2-Tdi)×(Tj2-Tj1) / (Ti2-Ti1)+(Tj2-Tdj) 7. The distribution network EPON differential protection sampling synchronization method according to claim 1, characterized in that: There are at least three power distribution devices in an EPON network.

8. The distribution network EPON differential protection sampling synchronization method according to claim 1, characterized in that: The first power distribution device is arranged at the uplink port of the EPON network to realize master-slave synchronization for all power distribution devices in the EPON network; or the first power distribution device is arranged in the EPON network to realize mutual synchronization for other power distribution devices and realize peer-to-peer synchronization.

9. The distribution network EPON differential protection sampling synchronization method according to claim 1, characterized in that: If the first power distribution device itself cannot achieve synchronization with other power distribution devices, each device in the EPON network takes turns to serve as the first power distribution device to achieve sampling synchronization among all power distribution devices in the EPON network.

10. A distribution network EPON differential protection sampling synchronization device using the distribution network EPON differential protection sampling synchronization method according to any one of claims 1 to 9, characterized in that: include: Sampling module, sampling synchronization module, message transceiver module; The sampling module is used to regularly collect the current and voltage data connected to the device; The sampling synchronization module is used to perform timestamp conversion on the sampling data of other devices, as well as Lagrange interpolation resampling synchronization function; The message transceiver module is used to send the sampled data, the first and second synchronization messages to other devices, and receive messages sent by other devices.

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