Time and frequency synchronization method and system of power line carrier

Abstract

The invention discloses a power line carrier time and frequency synchronization method and system, and the method comprises the steps: obtaining the frequency deviation of a time-using device and a time-frequency terminal based on the phase difference between preamble symbols in a plurality of frame data when the frequency deviation of the time-using device and the time-frequency terminal exists, frequency correction of the time-consuming equipment is carried out based on the frequency deviation, and frequency synchronization is realized; when the time-frequency terminal feeds back a modulated carrier signal to the power line at the PPS rising edge, the time-using equipment performs frame detection and frame synchronization, obtains the PPS rising edge time by adding the delay compensation time to the frame synchronization success time, and compensates the frequency deviation to the pulse per second timer at the same time, so that the time-using equipment obtains accurate PPS. According to the method, high-precision time synchronization service can be provided, synchronous operation among all parts of the power grid can be realized, and the reliability of the power grid is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of data transmission, and more particularly to a time and frequency synchronization method and system for a power line carrier. Background Art

[0002] The time synchronization system is the foundation of the power system. The use of smart grid in comprehensive automation equipment, automatic protection equipment and other self-control and remote control equipment is increasing. At present, the power grid has put forward higher and higher requirements on the performance of the whole network time synchronization accuracy, safety, stability, reliability and so on in the fields of power generation, transmission and distribution. In the applications of power grid power angle measurement system, wide area relay protection system, wide area power grid synchronization status monitoring system, it is necessary to develop large-scale high-precision measurement technology. High reliability, high precision and highly unified power grid time are the key and foundation for its implementation.

[0003] Therefore, a time and frequency synchronization method for power line carrier is needed. Summary of the invention

[0004] The present invention provides a method and system for synchronizing the time and frequency of a power line carrier, so as to solve the problem of how to synchronize the time and frequency of the power line carrier.

[0005] In order to solve the above problem, according to one aspect of the present invention, a time and frequency synchronization method for a power line carrier is provided, the method comprising:

[0006] When there is a frequency deviation between the timing device and the time-frequency terminal, the frequency deviation between the timing device and the time-frequency terminal is obtained based on the phase difference between the leading symbols in the plurality of frame data, so as to correct the frequency of the timing device based on the frequency deviation to achieve frequency synchronization;

[0007] When the frequency terminal feeds the modulated carrier signal back to the power line at the rising edge of PPS, the timing device performs frame detection and frame synchronization, and obtains the PPS rising edge time by adding the delay compensation time to the frame synchronization success time. At the same time, the frequency deviation is compensated to the second pulse timer, so that the timing device can obtain accurate PPS.

[0008] Preferably, the delay compensation time includes: video signal transmission delay, communication encoding and decoding delay and device processing delay.

[0009] Preferably, the method further comprises:

[0010] Based on the transmission speed of the cable signal in the cable and the length of the cable, a time-frequency signal transmission delay compensation value is determined, and delay compensation is performed based on the time-frequency signal transmission delay compensation value.

[0011] Preferably, the method further comprises:

[0012] A communication decoding delay compensation value is determined based on the communication rate and the information length, and delay compensation is performed based on the communication decoding delay compensation value.

[0013] Preferably, the method further comprises:

[0014] Based on the time-using equipment, the time for the time-frequency terminal on the station side to transmit the time-frequency value to the time-using equipment is compared multiple times to obtain the equipment processing delay compensation value, and delay compensation is performed based on the equipment processing delay compensation value.

[0015] According to another aspect of the present invention, there is provided a time and frequency synchronization system for a power line carrier, the system comprising:

[0016] A frequency correction unit is used to obtain the frequency deviation of the timing device and the time-frequency terminal based on the phase difference between the leading symbols in the plurality of frame data when there is a frequency deviation between the timing device and the time-frequency terminal, so as to correct the frequency of the timing device based on the frequency deviation to achieve frequency synchronization;

[0017] The time synchronization unit is used when the frequency terminal feeds back the modulated carrier signal to the power line at the rising edge of PPS. The timing device performs frame detection and frame synchronization, and adds the delay compensation time to the moment of successful frame synchronization to obtain the rising edge moment of PPS. At the same time, the frequency deviation is compensated to the second pulse timer, so that the timing device can obtain accurate PPS.

[0018] Preferably, the delay compensation time includes: video signal transmission delay, communication encoding and decoding delay and device processing delay.

[0019] Preferably, the time synchronization unit is further used for:

[0020] Based on the transmission speed of the cable signal in the cable and the length of the cable, a time-frequency signal transmission delay compensation value is determined, and delay compensation is performed based on the time-frequency signal transmission delay compensation value.

[0021] Preferably, the time synchronization unit is further used for:

[0022] A communication decoding delay compensation value is determined based on the communication rate and the information length, and delay compensation is performed based on the communication decoding delay compensation value.

[0023] Preferably, the time synchronization unit is further used for:

[0024] Based on the time-using equipment, the time for the time-frequency terminal on the station side to transmit the time-frequency value to the time-using equipment is compared multiple times to obtain the equipment processing delay compensation value, and delay compensation is performed based on the equipment processing delay compensation value.

[0025] The present invention provides a method and system for synchronizing the time and frequency of a power line carrier, comprising: when there is a deviation between the frequencies of a time-using device and a time-frequency terminal, the frequency deviation of the time-using device and the time-frequency terminal is obtained based on the phase difference between the leading symbols in a plurality of frame data, so as to correct the frequency of the time-using device based on the frequency deviation and realize frequency synchronization; when the time-frequency terminal feeds back the modulated carrier signal to the power line at the rising edge of the PPS, the time-using device performs frame detection and frame synchronization, and obtains the rising edge moment of the PPS by adding the delay compensation time to the frame synchronization success moment, and at the same time, the frequency deviation is compensated to the second pulse timer, so that the time-using device obtains an accurate PPS. The method of the present invention can provide a high-precision time synchronization service, which is helpful to realize the synchronous operation between various components of the power grid and improve the reliability of the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] A more complete understanding of exemplary embodiments of the present invention may be obtained by referring to the following drawings:

[0027] Figure 1 is a flow chart of a method 100 for synchronizing time and frequency of a power line carrier according to an embodiment of the present invention;

[0028] Figure 2 A schematic diagram of frequency correction according to an embodiment of the present invention;

[0029] Figure 3 is a flow chart of frequency correction according to an embodiment of the present invention;

[0030] Figure 4 FIG. 4 is a schematic structural diagram of a time and frequency synchronization system 400 for a power line carrier according to an embodiment of the present invention. DETAILED DESCRIPTION

[0031] Now, exemplary embodiments of the present invention are described with reference to the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to disclose the present invention in detail and completely and to fully convey the scope of the present invention to those skilled in the art. The terms used in the exemplary embodiments shown in the accompanying drawings are not intended to limit the present invention. In the accompanying drawings, the same units / elements are marked with the same reference numerals.

[0032] Unless otherwise specified, the terms (including technical terms) used herein have the commonly understood meanings to those skilled in the art. In addition, it is understood that the terms defined in commonly used dictionaries should be understood to have the same meanings as those in the context of the relevant fields, and should not be understood as idealized or overly formal meanings.

[0033] The purpose of the present invention is to solve the problem of high-precision, low-cost time and frequency transmission and synchronization of cluster timing equipment, taking into account both practicality and large-scale application requirements. The specific problems to be solved include: based on the high-precision frequency and carrier technology of the time-frequency terminal, high-precision frequency correction of the timing equipment is performed to achieve high-precision frequency synchronization; and timing time compensation is performed to achieve high-precision time synchronization for carrier signal transmission delay, communication encoding and decoding delay, equipment processing delay, etc.

[0034] Figure 1 FIG. 1 is a flow chart of a method 100 for synchronizing a power line carrier with respect to a time and frequency according to an embodiment of the present invention. Figure 1 As shown, the time and frequency synchronization method of the power line carrier provided by the embodiment of the present invention can provide high-precision time synchronization services, help to achieve synchronous operation between various components of the power grid, and improve the reliability of the power grid. The time and frequency synchronization method 100 of the power line carrier provided by the embodiment of the present invention starts from step 101. In step 101, when there is a deviation between the frequencies of the timing device and the time-frequency terminal, the frequency deviation of the timing device and the time-frequency terminal is obtained based on the phase difference between the leading symbols in multiple frame data, so as to correct the frequency of the timing device based on the frequency deviation to achieve frequency synchronization.

[0035] The purpose of frequency synchronization is to correct the frequency of the timing device to the frequency of the time-frequency terminal with an accuracy of ±1ppm. The time-frequency terminal will use its own clock source when modulating the carrier signal and the timing device will use it when demodulating the carrier signal. When there is a frequency deviation between the two devices, the leading symbol of the timing device will undergo phase rotation during signal demodulation. A complete frame includes the leading, frame control and payload information.

[0036] Therefore, in the present invention, the timing device calculates the phase of a leading symbol through correlation operation, and the frequency difference between the timing device and the time-frequency terminal can be calculated by using the phase difference between multiple leading symbols, thereby completing the frequency correction of the timing device. Through simulation and laboratory testing, the frequency deviation estimation accuracy can reach 1ppm, that is, the frequency of the timing device is corrected to within 1ppm of the frequency deviation of the time-frequency terminal through one frame of information, achieving the goal of the timing device's self-timekeeping capability of not less than 0.1s / day.

[0037] The principle of frequency correction of the present invention is as follows Figure 2 The overall process of frequency offset correction is as follows: Figure 3 As shown, including:

[0038] (1) The timing device sends time information. The frame message contains the timestamp information t1, which is 32 bits and driven by the 25MHz local clock source divided by 4, 6.25MHz, and the timer period is 687 seconds.

[0039] (2) The receiving end receives the time information. It generates a frame synchronization signal and latches the local NTB information t2. The local NTB information is 32 bits, driven by a 25MHz local clock source divided by 4 to 6.25MHz, and has a timing period of 687 seconds. After the receiving end demodulates the information, it extracts the timestamp information.

[0040] (3) If the information is received for the first time, no frequency deviation correction is performed.

[0041] (4) If the frequency offset correction is not performed when the information is received for the first time, the current frame reception timestamp information and local NTB information are recorded as t1 and t2, and the previous frame reception timestamp information and local NTB information are recorded as t3 and t4. The frequency offset calculation formula is as follows: the timing device performs time synchronization in a period of 60 seconds, and the receiving end performs frequency offset correction every 60 seconds. The unit of the frequency offset correction result is ppm. After correction, the accuracy of the receiving end clock source is close to the accuracy of the timing device clock source ±1ppm, which meets the requirement of ±5ppm for the second pulse signal.

[0042] In step 102, when the frequency terminal feeds back the modulated carrier signal to the power line at the rising edge of PPS, the timing device performs frame detection and frame synchronization, and obtains the rising edge time of PPS by adding the delay compensation time to the frame synchronization success moment, and at the same time compensates the frequency deviation to the second pulse timer, so that the timing device can obtain accurate PPS.

[0043] Preferably, the delay compensation time includes: video signal transmission delay, communication encoding and decoding delay and device processing delay.

[0044] Preferably, the method further comprises:

[0045] Based on the transmission speed of the cable signal in the cable and the length of the cable, a time-frequency signal transmission delay compensation value is determined, and delay compensation is performed based on the time-frequency signal transmission delay compensation value.

[0046] Preferably, the method further comprises:

[0047] A communication decoding delay compensation value is determined based on the communication rate and the information length, and delay compensation is performed based on the communication decoding delay compensation value.

[0048] Preferably, the method further comprises:

[0049] Based on the time-using equipment, the time for the time-frequency terminal on the station side to transmit the time-frequency value to the time-using equipment is compared multiple times to obtain the equipment processing delay compensation value, and delay compensation is performed based on the equipment processing delay compensation value.

[0050] In the present invention, the high-precision time synchronization technology includes two parts: time synchronization and delay compensation.

[0051] Among them, delay compensation mainly completes the compensation for three types of delays, including: video signal transmission delay, communication encoding and decoding delay and equipment processing delay.

[0052] For the time-frequency signal transmission delay, it refers to the time required for the electrical signal to be transmitted in the cable. The longer the cable length, the longer the time delay. If the transmission speed of the electrical signal in the cable is recorded as c / 2, c is the transmission speed of light in a vacuum, it can be calculated that the time delay of the electrical signal transmission in a 1000m cable is about 17μs, and a 1000m cable can meet the power supply needs of most on-site stations. Therefore, in the present invention, based on the transmission speed of the cable signal in the cable and the length of the cable, the time-frequency signal transmission delay compensation value is determined, and the obtained time-frequency signal transmission delay compensation value is set to a fixed value for delay compensation.

[0053] The communication encoding and decoding delay is mainly determined by the communication rate and the information length. Under the premise of determining the communication rate and the information length, the communication system delay can be obtained by calculation. Therefore, in the present invention, the communication decoding delay compensation value is determined based on the communication rate and the information length, and the delay compensation is performed based on the communication decoding delay compensation value.

[0054] The device processing delay refers to the time required for the device to collect signals and transmit the physical layer demodulation time to the application layer. In the one-way communication (broadcast) carrier technology solution, the time for each transmission of the time-frequency value from the station side time-frequency terminal to the time-using device is fixed and known. The time-using device can calculate the device processing delay by comparing the time-frequency values ​​received multiple times. Therefore, in the present invention, based on the time-using device, the time for the station side time-frequency terminal to transmit the time-frequency value to the time-using device is compared multiple times to obtain the device processing delay compensation value, and delay compensation is performed based on the device processing delay compensation value.

[0055] In the present invention, time synchronization means that the time-frequency terminal feeds back the modulated carrier signal to the power line at the rising edge of PPS, and the timing equipment performs frame detection and frame synchronization, and obtains the rising edge time of PPS by adding the delay compensation time to the frame synchronization success time, and at the same time compensates the frequency deviation to the second pulse timer, and obtains the accurate PPS by the timing equipment. The PPS accuracy is 20μs as measured in the laboratory.

[0056] The method of the present invention is applicable to a variety of scenarios. In the synchronous operation of the power grid: the power grid needs to maintain time synchronization between various components (power plants, substations, transmission lines, etc.) to ensure the stable operation and safety of the power grid. Satellite common view timing technology can provide high-precision time synchronization services, which helps to achieve synchronous operation between various components of the power grid and improve the reliability of the power grid.

[0057] Figure 4FIG. 4 is a schematic diagram of a time and frequency synchronization system 400 for a power line carrier according to an embodiment of the present invention. Figure 4 As shown, a time and frequency synchronization system 400 of a power line carrier provided by an embodiment of the present invention includes: a frequency correction unit 401 and a time synchronization unit 402 .

[0058] Preferably, the frequency correction unit 401 is used to obtain the frequency deviation of the timing device and the time-frequency terminal based on the phase difference between the leading symbols in multiple frame data when there is a frequency deviation between the timing device and the time-frequency terminal, so as to perform frequency correction of the timing device based on the frequency deviation to achieve frequency synchronization.

[0059] Preferably, the time synchronization unit 402 is used for the timing device to perform frame detection and frame synchronization when the frequency terminal feeds back the modulated carrier signal to the power line at the rising edge of PPS, and to obtain the rising edge moment of PPS by adding the delay compensation time to the moment of successful frame synchronization, and at the same time to compensate the frequency deviation to the second pulse timer, so that the timing device can obtain accurate PPS.

[0060] Preferably, the delay compensation time includes: video signal transmission delay, communication encoding and decoding delay and device processing delay.

[0061] Preferably, the time synchronization unit 402 is further used for:

[0062] Based on the transmission speed of the cable signal in the cable and the length of the cable, a time-frequency signal transmission delay compensation value is determined, and delay compensation is performed based on the time-frequency signal transmission delay compensation value.

[0063] Preferably, the time synchronization unit 402 is further used for:

[0064] A communication decoding delay compensation value is determined based on the communication rate and the information length, and delay compensation is performed based on the communication decoding delay compensation value.

[0065] Preferably, the time synchronization unit 402 is further used for:

[0066] Based on the time-using equipment, the time for the time-frequency terminal on the station side to transmit the time-frequency value to the time-using equipment is compared multiple times to obtain the equipment processing delay compensation value, and delay compensation is performed based on the equipment processing delay compensation value.

[0067] The time and frequency synchronization system 400 of a power line carrier according to an embodiment of the present invention corresponds to the time and frequency synchronization method 100 of a power line carrier according to another embodiment of the present invention, and will not be described in detail herein.

[0068] The invention has been described above with reference to a few embodiments. However, it is readily apparent to a person skilled in the art that other embodiments than the ones disclosed above are equally within the scope of the invention, as defined by the appended patent claims.

[0069] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise therein. All references to "a / said / the [means, components, etc.]" are to be openly interpreted as at least one instance of said means, components, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not necessarily have to be performed in the exact order disclosed, unless explicitly stated otherwise.

[0070] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0071] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0072] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0073] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0074] 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. Any modification or equivalent replacement that does 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 method for synchronizing time and frequency of a power line carrier, characterized in that: The method comprises: When there is a frequency deviation between the timing device and the time-frequency terminal, the frequency deviation between the timing device and the time-frequency terminal is obtained based on the phase difference between the leading symbols in the plurality of frame data, so as to correct the frequency of the timing device based on the frequency deviation to achieve frequency synchronization; When the frequency terminal feeds the modulated carrier signal back to the power line at the rising edge of PPS, the timing device performs frame detection and frame synchronization, and obtains the PPS rising edge time by adding the delay compensation time to the frame synchronization success time. At the same time, the frequency deviation is compensated to the second pulse timer, so that the timing device can obtain accurate PPS.

2. The method according to claim 1, characterized in that The delay compensation time includes: video signal transmission delay, communication encoding and decoding delay and equipment processing delay.

3. The method according to claim 2, characterized in that The method further comprises: Based on the transmission speed of the cable signal in the cable and the length of the cable, a time-frequency signal transmission delay compensation value is determined, and delay compensation is performed based on the time-frequency signal transmission delay compensation value.

4. The method according to claim 2, characterized in that: The method further comprises: A communication decoding delay compensation value is determined based on the communication rate and the information length, and delay compensation is performed based on the communication decoding delay compensation value.

5. The method according to claim 2, characterized in that: The method further comprises: Based on the time-using equipment, the time for the time-frequency terminal on the station side to transmit the time-frequency value to the time-using equipment is compared multiple times to obtain the equipment processing delay compensation value, and delay compensation is performed based on the equipment processing delay compensation value.

6. A time and frequency synchronization system for a power line carrier, characterized in that: The system comprises: A frequency correction unit is used to obtain the frequency deviation of the timing device and the time-frequency terminal based on the phase difference between the leading symbols in the plurality of frame data when there is a frequency deviation between the timing device and the time-frequency terminal, so as to correct the frequency of the timing device based on the frequency deviation to achieve frequency synchronization; The time synchronization unit is used when the frequency terminal feeds back the modulated carrier signal to the power line at the rising edge of PPS. The timing device performs frame detection and frame synchronization, and adds the delay compensation time to the moment of successful frame synchronization to obtain the rising edge moment of PPS. At the same time, the frequency deviation is compensated to the second pulse timer, so that the timing device can obtain accurate PPS.

7. The system according to claim 6, characterized in that The delay compensation time includes: video signal transmission delay, communication encoding and decoding delay and equipment processing delay.

8. The system according to claim 7, characterized in that The time synchronization unit is further used for: Based on the transmission speed of the cable signal in the cable and the length of the cable, a time-frequency signal transmission delay compensation value is determined, and delay compensation is performed based on the time-frequency signal transmission delay compensation value.

9. The system according to claim 7, characterized in that The time synchronization unit is further used for: A communication decoding delay compensation value is determined based on the communication rate and the information length, and delay compensation is performed based on the communication decoding delay compensation value.

10. The system according to claim 7, characterized in that The time synchronization unit is further used for: Based on the time-using equipment, the time for the time-frequency terminal on the station side to transmit the time-frequency value to the time-using equipment is compared multiple times to obtain the equipment processing delay compensation value, and delay compensation is performed based on the equipment processing delay compensation value.

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