A method and device for phase synchronization of power distribution terminal sampling

Abstract

A method and device for sampling phase synchronization of distribution terminals, which periodically calculates the phase angle and cycle length of local sampling data, and the devices on both sides periodically transmit phase angle and cycle length data to each other. The ping-pong method or historical phase synchronization data is used to find the phase angle data on this side that is close to the opposite side. The phase angle and cycle length data on both sides are then used to calculate accurate synchronization parameters. Finally, the synchronization parameters are used to synchronize the sampling data on both sides. A method for achieving sampling phase synchronization of distribution terminals in a 5G network without relying on an external timing source is implemented. The reliability of the distribution network is improved, and the communication traffic overhead of this method is extremely small, and there is no need to configure an external timing source device separately, saving construction and use costs.

Description

Technical Field

[0001] The present invention belongs to the field of distribution network relay protection, and more specifically, to a distribution terminal sampling phase synchronization method and device. Background Art

[0002] The Distribution Terminal Unit (DTU) is a critical device in the distribution network, used to collect and calculate primary data. Due to the drawbacks of traditional DTU overcurrent protection, such as complex setting, wide outage coverage, long delays, and prone to over-tripping, current DTU designs incorporate differential protection to more accurately locate and quickly isolate fault points.

[0003] The implementation of differential protection requires adjacent DTUs in the distribution network to exchange sampled data and synchronize the data at both ends. Dedicated fiber optic channels for differential protection are generally not configured in distribution networks. To avoid the need for extensive fiber optic communication networks along the distribution network, DTUs are currently designed to utilize 5G wireless networks for data transmission.

[0004] 5G wireless networks exhibit significant and variable communication delays. Currently, implementing DTU differential protection on 5G networks typically relies on clock signals from an external timing source and a synchronization scheme based on a unified clock signal. Therefore, if the external timing source's signal is abnormal, the DTU device must block its differential protection function to prevent malfunction.

[0005] Therefore, there is an urgent need for a sampling synchronization method for distribution network DTU differential protection that is available on 5G networks and does not rely on an external timing source. Summary of the Invention

[0006] In order to address the deficiencies in the prior art, the present invention provides a method and device for achieving sampling phase synchronization of power distribution terminals in a 5G network without relying on an external timing source.

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

[0008] A method for phase synchronization of sampling of a power distribution terminal comprises the following steps:

[0009] Step 1: regularly calculate the phase angle and cycle length of the sampling data of the local power distribution terminal device and obtain the timestamp;

[0010] Step 2: The power distribution terminal devices on both sides of the line periodically transmit phase angle and frequency length data to each other;

[0011] Step 3: Determine the primary phase angle data of the power distribution terminal device on the local side that is closest to the power distribution terminal device on the opposite side;

[0012] Step 4: Use the phase angle and cycle length data on both sides to calculate the precise synchronization parameters;

[0013] Step 5: Use the synchronization parameters to synchronize the sampling data of the power distribution terminal devices on both sides.

[0014] Preferably, step 1 specifically includes phase angle data calculated based on the sampled data, duration data of one cycle, and a timestamp indicating the current data moment. The base frequency of my country's power grid is 50 Hz, with a period of 20 ms. To ensure that the phase angle data on both sides does not exceed one cycle, when calculating the phase angle of the local sampled data, the phase angle is calculated every 5 ms, four times per cycle, taking into account the possible 50 Hz frequency offset during actual grid operation.

[0015] The cycle length data must ensure that the analog value of the current or voltage has a certain amplitude to ensure that the captured cycle is complete. Otherwise, due to factors such as small signal waveform distortion, the actual measurement may under- or over-measure the duration of a cycle, resulting in large errors. Because the grid frequency does not change significantly in a short period of time, each time the phase angle is calculated, the duration of the most recent cycle is recorded as the current cycle length data. The duration is measured using the internal crystal oscillator clock. To reduce measurement errors, the duration data of several consecutive recent cycles can also be averaged.

[0016] The timestamp needs to be added according to the crystal oscillator clock in the device. When selecting the timestamp, the devices on both sides need to uniformly select the sampling time of a certain point in the sampling data used to calculate the phase angle, and select the time of the last sampling point within a cycle length.

[0017] Due to wireless network environments such as 5G, the average communication delay may range from tens to hundreds of milliseconds. Therefore, the phase angle and cycle length of the local sampled data must be calculated regularly. The amount of data that exceeds the communication delay must be retained according to the actual communication delay on site so that available data can be found later.

[0018] Preferably, in step 2, the power distribution terminal devices on both sides regularly calculate and record the phase angle and cycle length data of the sampled data, and send the phase angle and cycle length data of the latest sample on the local side to the power distribution terminal device on the opposite side at the same set time interval. The time interval is 500ms.

[0019] Preferably, in step 3, since the devices on both sides operate independently, the actual times for calculating the phase angle on both sides are different. Therefore, in this step, only the phase angle data of this side and the opposite side are required, and the time for obtaining the phase angle does not exceed one cycle (the deviation is less than plus or minus half a cycle).

[0020] Coarse synchronization measures the average link delay by sending a probe message to the other side and receiving its reply. Using the probe message's send timestamp (T1), receive timestamp (T2), send timestamp (T3), and receive timestamp (T4), the network's communication delay (T) is estimated, assuming the time it takes for the probe message to be sent to the other side equals the time it takes for the other side to reply to the probe message. Based on the communication delay (T) obtained through coarse synchronization, the time when the other side generated the data after receiving the phase angle and cycle length data from the other side is inferred.

[0021] When using a 5G wireless network, after achieving phase synchronization using coarse synchronization, you can switch to using historical phase synchronization parameters to calculate the conversion of the opposite-side timestamp to the local timestamp. You can also consider stopping coarse synchronization messages to save network traffic.

[0022] Preferably, step 4 comprises the following steps:

[0023] Step 4.1: Use the phase angle values on both sides of the same channel for comparison. Based on the phase angle of the opposite side and the phase angle of this side, calculate the phase angle deviation: A d =A 对侧 -A 本侧 ;

[0024] Step 4.2, based on the duration of one cycle T on the opposite side 对侧 , and the angle A of the entire cycle c =2*π or 360° (the unit of the phase angle must match), and the adjustment amount of the opposite side sampling timestamp is obtained proportionally: D t =(A d / A c )*T 对侧 ;

[0025] Step 4.3, according to the timestamp of the opposite phase angle, obtain the timestamp of the opposite phase angle corresponding to the current phase angle: t2 = t 对侧 -D t ;

[0026] Step 4.4, calculate the ratio of the crystal oscillator time axis on both sides based on the duration of one cycle on this side and the opposite side: M = T 本侧 / T 对侧 ;

[0027] Step 4.5, record t1 = t 本侧 t1 and t2 are the local and opposite side timestamps at the same moment, and M is recorded as the time axis ratio parameter on both sides, which is used as the synchronization parameter obtained by phase synchronization calculation.

[0028] Preferably, in step 5, the synchronization parameters obtained in step 4 are used to convert the timestamp of the opposite sampling moment into the timestamp on the local crystal oscillator time axis, and the difference resampling method is used to achieve synchronization of the sampling data on both sides. The timestamp conversion method is: according to the timestamp t of a certain sampling moment on the opposite side, the timestamp of the corresponding moment on the local side is converted: t 转 =t1+(t-t2)*M.

[0029] A distribution terminal sampling phase synchronization device operates a distribution terminal sampling phase synchronization method, which includes: a phase angle and cycle length calculation module, a message timing sending module, an opposite side message receiving module, a synchronization parameter calculation module, and a sampling synchronization module;

[0030] The phase angle and cycle length calculation module is used to regularly calculate the phase angle and cycle length data based on the current sampling data, and record the timestamp of the current data at the sampling moment of the latest sampling data used in the calculation;

[0031] The message timing sending module is used to regularly frame and send the latest primary phase angle and cycle length data to the opposite device;

[0032] The opposite side message receiving module is used to receive the phase angle and cycle length data sent regularly by the opposite side;

[0033] The synchronization parameter calculation module is used to calculate the opposite-side timestamp conversion parameters that can be used for sampling synchronization using the local and opposite-side phase angle and cycle length data;

[0034] The sampling synchronization module is used to convert the timestamps in the sampling data sent by the opposite side into local timestamps, and use the difference resampling method to achieve synchronization of the sampling data on both sides.

[0035] The beneficial effect of the present invention is that, compared with the prior art, it provides a sampling phase synchronization method for distribution terminals, which solves the problem of a sampling synchronization method that can be used in a 5G network environment without relying on an external timing source, thereby improving the reliability of the distribution network. In addition, the communication traffic overhead of this method is extremely small, and there is no need to configure an external timing source device separately, thus saving construction and use costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a flow chart of a method for sampling phase synchronization of a power distribution terminal;

[0037] Figure 2 This is the simplest system structure diagram of a sampling phase synchronization device for a power distribution terminal;

[0038] Figure 3 It is a set of measured phase deviation data line graphs based on phase synchronization of the sampling data on both sides;

[0039] Figure 4 This is a set of measured comparison diagrams of the sampling data waveforms and phase angle calculations of a channel on both sides based on phase synchronization. DETAILED DESCRIPTION

[0040] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying 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 making creative efforts are all within the scope of protection of the present invention.

[0041] Embodiment 1 of the present invention provides a method for sampling phase synchronization of a power distribution terminal, which specifically includes the following steps:

[0042] Step 1: Periodically calculate the phase angle and cycle length of the sampling data of the local power distribution terminal device and obtain the timestamp.

[0043] Step 1 specifically includes the phase angle data calculated from the sampled data, the duration of a cycle, and the timestamp representing the current data moment. my country's power grid base frequency is 50 Hz, with a period of 20 ms. To ensure that the phase angle data on both sides does not exceed one cycle, the phase angle of the local sampled data must be calculated at least twice per cycle. Considering the potential for a 50 Hz frequency offset during actual grid operation, the calculation is preferably performed every 5 ms, for a total of four calculations per cycle.

[0044] The cycle length data must ensure that the analog value of the current or voltage has a certain amplitude to ensure that the captured cycle is complete. Otherwise, due to factors such as small signal waveform distortion, the actual measurement may under- or over-measure the duration of a cycle, resulting in large errors. Because the grid frequency does not change significantly in a short period of time, each time the phase angle is calculated, the duration of the most recent cycle is recorded as the current cycle length data. The duration is measured using the internal crystal oscillator clock. To reduce measurement errors, the duration data of several consecutive recent cycles can also be averaged.

[0045] The timestamp needs to be added according to the crystal oscillator clock in the device. When selecting the timestamp, the devices on both sides need to uniformly select the sampling time of a certain point in the sampling data used to calculate the phase angle. Generally, the time of the last sampling point within a cycle length is selected.

[0046] Due to wireless network environments such as 5G, the average communication delay may range from tens to hundreds of milliseconds. Therefore, the phase angle and cycle length of the local sampled data must be calculated regularly. The amount of data that exceeds the communication delay must be retained according to the actual communication delay on site so that available data can be found later.

[0047] Step 2: The devices on both sides of the line periodically transmit phase angle and frequency length data to each other.

[0048] The opposite device uses the same method as in step 1 to periodically calculate and record phase angle and cycle length data, and slowly sends the most recent data to the local device, with an optional 500ms interval. The local device also periodically sends the most recent data to the opposite device at the same frequency.

[0049] Step 3: Determine the primary phase angle data of the power distribution terminal device on this side that is closest to the power distribution terminal device on the opposite side.

[0050] After receiving the phase angle and cycle length data sent by the opposite side, the timestamp of the opposite side in the data is converted into the timestamp of this side using coarse synchronization or historical phase synchronization data. Based on the converted timestamp, the set of data closest to this time is found in the amplitude and phase angle data sequence of this side calculated in step 1 for more accurate phase synchronization calculation.

[0051] Since the devices on both sides operate independently, the actual times for calculating the phase angle on both sides are different. Therefore, in this step, only the phase angle data of this side and the opposite side are required, and the time for obtaining the phase angle does not exceed one cycle (the deviation is less than plus or minus half a cycle).

[0052] Coarse synchronization sends a probe message to the other side, and measures the average delay of the link by replying from the other side. Using the probe message's sending timestamp T1, receiving timestamp T2, sending timestamp T3, and receiving timestamp T4, assuming that the communication time sent to the other side is equal to the communication time the other side replies to this side, the communication delay T of the current network is estimated. Based on the communication delay T obtained by ping-pong, after receiving the phase angle and cycle length data from the other side, the approximate time when the other side generated this data is estimated. Coarse synchronization can measure the delay of the communication link on both sides. It is generally used for links with fixed delays and fixed paths. By measuring and deducting the communication delay, the time synchronization and sampling synchronization of the two sides are achieved. The 5G network does not meet the prerequisites of fixed delays and fixed paths, which will cause the results of the coarse synchronization calculation to have certain errors, but it can still meet the requirement of not more than one cycle.

[0053] When using a 5G wireless network, after achieving phase synchronization using coarse synchronization, you can switch to using historical phase synchronization parameters to calculate the conversion of the opposite-side timestamp to the local timestamp. You can also consider stopping coarse synchronization messages to save network traffic.

[0054] Step 4: Use the phase angle and cycle length data on both sides to calculate the precise synchronization parameters.

[0055] Step 4.1: Use the phase angle values on both sides of the same channel for comparison. Based on the phase angle of the opposite side and the phase angle of this side, calculate the phase angle deviation: A d =A 对侧 -A 本侧 ;

[0056] Step 4.2, based on the duration of one cycle T on the opposite side 对侧 , and the angle A of the entire cycle c =2*π or 360° (the unit of the phase angle must match), and the adjustment amount of the opposite side sampling timestamp is obtained proportionally: D t =(A d / A c )*T 对侧 ;

[0057] Step 4.3, according to the timestamp of the opposite phase angle, obtain the timestamp of the opposite phase angle corresponding to the current phase angle: t2 = t 对侧 -D t ;

[0058] Step 4.4, calculate the ratio of the crystal oscillator time axis on both sides based on the duration of one cycle on this side and the opposite side: M = T 本侧 / T 对侧 ;

[0059] Step 4.5, record t1 = t 本侧 t1 and t2 are the local and opposite side timestamps at the same moment, and M is recorded as the time axis ratio parameter on both sides, which is used as the synchronization parameter obtained by phase synchronization calculation.

[0060] To improve reliability, you can also use the duration of multiple cycles on both the local and remote sides when calculating M, obtaining more accurate synchronization parameter results. To improve reliability, you can choose to use multiple sampling channels, calculate the synchronization parameters separately, and then take the average value to obtain more accurate synchronization parameter results.

[0061] Step 5: Use the synchronization parameters to synchronize the sampling data of the power distribution terminal devices on both sides.

[0062] Using the synchronization parameters obtained in step 4, convert the timestamp of the opposite sampling moment into the timestamp on the local crystal oscillator time axis, and use the difference resampling method to synchronize the sampling data on both sides. The timestamp conversion method is: according to the timestamp t of a certain sampling moment on the opposite side, convert the timestamp of the corresponding moment on the local side: t 转 =t1+(t-t2)*M.

[0063] Embodiment 2 of the present invention provides a distribution terminal sampling phase synchronization device, which runs a distribution terminal sampling phase synchronization method as described in embodiment 1, and includes: a phase angle and cycle length calculation module, a message timing sending module, a opposite side message receiving module, a synchronization parameter calculation module, and a sampling synchronization module;

[0064] The phase angle and cycle length calculation module is used to regularly calculate the phase angle and cycle length data according to the current sampling data, and record the timestamp of the current data at the sampling moment of the latest sampling data used in the calculation.

[0065] The message timing sending module is used to regularly frame and send the latest primary phase angle and cycle length data to the opposite device;

[0066] The opposite side message receiving module is used to receive the phase angle and cycle length data sent regularly by the opposite side;

[0067] The synchronization parameter calculation module is used to calculate the opposite-side timestamp conversion parameters that can be used for sampling synchronization using the local and opposite-side phase angle and cycle length data;

[0068] The sampling synchronization module is used to convert the timestamps in the sampling data sent by the opposite side into local timestamps, and use the difference resampling method to achieve synchronization of the sampling data on both sides.

[0069] 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 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 by the scope of protection of the claims of the present invention.

Claims

1. A method for sampling phase synchronization of a power distribution terminal, characterized in that: The following steps are involved: Step 1: regularly calculate the phase angle and cycle length of the sampling data of the local power distribution terminal device and obtain the timestamp; Step 2: The power distribution terminal devices on both sides of the line periodically transmit phase angle and frequency length data to each other; Step 3: Determine the primary phase angle data of the power distribution terminal device on the local side that is closest to the power distribution terminal device on the opposite side; Step 4, using the phase angle and cycle length data on both sides to calculate the precise synchronization parameters, step 4 includes the following steps: Step 4.1: Use the phase angle values on both sides of the same channel for comparison. Based on the phase angle of the opposite side and the phase angle of this side, calculate the phase angle deviation: A d =A 对侧 -A 本侧 ; Step 4.2, based on the duration of one cycle T on the opposite side 对侧 , and the angle A of the entire cycle c =2*π or 360°, and the adjustment amount of the opposite side sampling timestamp is obtained proportionally: D t =(A d / A c )*T 对侧 ; Step 4.3, according to the timestamp of the opposite phase angle, obtain the timestamp of the opposite phase angle corresponding to the current phase angle: t2 = t 对侧 -D t ; Step 4.4, calculate the ratio of the crystal oscillator time axis on both sides based on the duration of one cycle on this side and the opposite side: M = T 本侧 / T 对侧 ; Step 4.5, record t1 = t 本侧 and t2 are the local and contralateral timestamps at the same moment, and M is recorded as the time axis ratio parameter on both sides, which is used as the synchronization parameter obtained by phase synchronization calculation; Step 5: Use the synchronization parameters to synchronize the sampling data of the power distribution terminal devices on both sides.

2. A distribution terminal sampling phase synchronization method according to claim 1, characterized in that: In step 1, when calculating the phase angle of the sampled data, the calculation is performed every 5 ms, and 4 times in one cycle.

3. A distribution terminal sampling phase synchronization method according to claim 1, characterized in that: In step 1, the cycle length data must ensure that the analog value of the current current or voltage has a certain amplitude to ensure that the captured cycle is complete; each time the phase angle is calculated, the duration of the most recent cycle currently measured is recorded as the cycle length data at the current moment. The duration is measured using the internal crystal oscillator clock, or the duration data of several consecutive cycles are averaged.

4. A distribution terminal sampling phase synchronization method according to claim 1, characterized in that: In step 1, a timestamp is added according to the crystal oscillator clock in the power distribution terminal device, and the power distribution terminal devices on both sides uniformly select a sampling time of a certain point in the sampled data used for calculating the phase angle as the time for selecting the timestamp.

5. A distribution terminal sampling phase synchronization method according to claim 4, characterized in that: The power distribution terminal devices on both sides uniformly select the moment of the last sampling point within a cycle length as the time of selecting the timestamp.

6. A distribution terminal sampling phase synchronization method according to claim 1, characterized in that: In step 2, the power distribution terminal devices on both sides regularly calculate and record the phase angle and cycle length data of the sampled data, and send the phase angle and cycle length data of the latest sample on this side to the power distribution terminal device on the opposite side at the same set time interval.

7. A distribution terminal sampling phase synchronization method according to claim 6, characterized in that: The time interval is 500ms.

8. A distribution terminal sampling phase synchronization method according to claim 1, characterized in that: In step 3, the phase angle data of the local side and the opposite side are obtained at a time not exceeding one cycle.

9. A method for sampling phase synchronization of a power distribution terminal according to claim 8, characterized in that: In step 3, the coarse synchronization method is used to determine the closest phase angle data between the local side and the opposite side: The average link delay is measured by sending a probe message to the other side and receiving its reply. The local side's send timestamp T1, the remote side's receive timestamp T2, the remote side's send timestamp T3, and the local side's receive timestamp T4 are used. Assuming that the communication time sent to the remote side is equal to the communication time it takes for the remote side to reply to the local side, the current network communication delay T is estimated. Based on the communication delay T obtained from coarse synchronization, after receiving the phase angle and cycle length data from the remote side, the time when the remote side generated this data is inferred.

10. A distribution terminal sampling phase synchronization method according to claim 8, characterized in that: In step 3, the historical phase synchronization data may also be used to determine the closest phase angle data between the local side and the opposite side.

11. A distribution terminal sampling phase synchronization method according to claim 1, characterized in that: In step 5, the synchronization parameters obtained in step 4 are used to convert the timestamp of the opposite sampling moment into the timestamp on the local crystal oscillator time axis, and the difference resampling method is used to synchronize the sampling data on both sides. The timestamp conversion method is: according to the timestamp t of a certain sampling moment on the opposite side, the timestamp of the corresponding moment on the local side is converted: t 转 =t1+(t-t2)*M.

12. A distribution terminal sampling phase synchronization device, which runs a distribution terminal sampling phase synchronization method according to any one of claims 1 to 11, comprising a phase angle and cycle length calculation module, a message timing sending module, a opposite-side message receiving module, a synchronization parameter calculation module, and a sampling synchronization module, characterized in that: The phase angle and cycle length calculation module is used to regularly calculate the phase angle and cycle length data based on the current sampling data, and record the timestamp of the current data at the sampling moment of the latest sampling data used in the calculation; The message timing sending module is used to regularly frame and send the latest primary phase angle and cycle length data to the opposite device; The opposite side message receiving module is used to receive the phase angle and cycle length data sent regularly by the opposite side; The synchronization parameter calculation module is used to calculate the opposite-side timestamp conversion parameters that can be used for sampling synchronization using the local and opposite-side phase angle and cycle length data; The sampling synchronization module is used to convert the timestamps in the sampling data sent by the opposite side into local timestamps, and use the difference resampling method to achieve synchronization of the sampling data on both sides.

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