Ammeter phase detection method and system based on RF communication network

Abstract

The invention provides an electric meter phase detection method and system based on an RF communication network, a master meter and slave meters each comprise an MCU module and an RF module, the master meter is in direct connection communication with the multiple slave meters through the RF modules, and phase identification is achieved by means of the voltage zero-cross detection function of an electric meter and the basic communication function of the communication modules; one master table sends data, and a plurality of slave tables detect data at the same time; the detection phase is actively triggered when needed; averaging the values detected for multiple times; each device only needs to carry out phase detection calculation according to own time, and does not need to carry out clock synchronization with other devices; when the RF module on the main meter sends data, conflict detection is not carried out, so that the time delay from zero-crossing signal generation to data sending is reduced, and the detection precision is improved; data processing and transmission delay are dynamically adjusted in the detection process, and the detection precision is improved.

Description

Technical Field

[0001] This invention relates to the field of smart meters, and more specifically to a detection method and system for identifying the phase installation status of each meter in a data acquisition system using RF communication. Background Technology

[0002] The installation phase of electricity meters is closely related to the safe operation, energy efficiency optimization, and operation and maintenance management of the power system, specifically in the following aspects: 1. Ensure three-phase load balance. In a three-phase power supply system, if the load distribution of each phase is uneven (for example, too many meters are connected to one phase), it will lead to excessive current in that phase, increasing line and transformer losses and reducing the overall power supply efficiency of the system. At the same time, three-phase imbalance may also cause transformer overheating or abnormal motor vibration, accelerate equipment insulation aging, and shorten equipment lifespan.

[0003] 2. Supports rapid fault location and recovery. When a short circuit or ground fault occurs in a phase, if the meter phase information is clear, the affected user range can be quickly determined, accelerating fault isolation and power restoration, and reducing power outage time.

[0004] 3. Improve power quality. Three-phase load imbalance may cause voltage fluctuations on the user side, affecting the normal operation of equipment sensitive to power quality (such as medical instruments and precision machine tools). In addition, if nonlinear loads (such as LED lights and frequency converters) are concentrated on the same phase, it may cause harmonic interference problems. Clear phase information helps to implement targeted management.

[0005] 4. Ensure metering accuracy and prevent electricity theft. Unauthorized cross-phase wiring or alteration of phase markings by users may lead to metering errors. Recording and verifying phase information provides evidence for investigating electricity theft and ensures fair and accurate metering.

[0006] 5. Supporting the development of smart grids. In smart meter applications, phase information can be used for advanced functions such as dynamic load control and optimized energy distribution, providing a data foundation for the intelligent upgrading of the power grid.

[0007] In conclusion, the installation phase of electricity meters is not only a fundamental technical parameter but also a crucial support for achieving refined power grid management. Clearly defined phase information helps improve system reliability, reduce operating costs, and promote the development of future smart electricity applications. For users, it relates to electricity quality and billing fairness; for power grid companies, it is a necessary condition for achieving efficient operation and maintenance and compliant management.

[0008] However, in electricity consumption information acquisition systems using radio frequency (RF) communication, the RF communication module is physically isolated from the power lines. Therefore, it cannot directly calculate the phase by detecting the zero-crossing signal of the power line, as in PLC power line carrier communication. Thus, how to identify the phase status of each meter in an RF communication-based electricity consumption information acquisition system is a problem that urgently needs to be solved. Summary of the Invention

[0009] The purpose of this invention is to address the problem of identifying the phase status of each meter in a data acquisition system when the communication module between meters lacks the hardware for phase detection. This invention proposes a meter phase detection method and system based on an RF communication network. Based on the two fundamental functions of the meter—zero-crossing signal detection by the meter's MCU module and communication by the communication module—this invention achieves meter phase detection without increasing costs.

[0010] The technical solution of this invention is: In a first aspect, the present invention provides a method for detecting the phase of an electricity meter based on an RF communication network. Both the master meter and the slave meter include an MCU module and an RF module. The master meter communicates directly with multiple slave meters through the RF module. The method for detecting the phase of an electricity meter includes the following steps: S1. The master table sends a phase detection notification to the slave table through the RF module. After receiving the notification, the slave table starts the MCU module to detect the zero-crossing signal of the grid voltage and notifies its RF module every time a zero-crossing signal is detected. S2. After the master table sends the detection command, it starts its own MCU module to detect the zero-crossing signal of the power grid voltage and notifies the RF module. The RF module broadcasts a data frame to all slave tables every time it receives a zero-crossing signal. S3. Each time the RF module receives a broadcast data frame from the master table, it records the reception time T1. After receiving the data frame, it detects the first zero-crossing signal sent by the MCU module of the slave table and records the time T2. Repeat this process multiple times to calculate the average value of the first phase difference. S4. The master table obtains the average value of the first phase difference calculated by the RF module of each slave table, and determines the phase of each slave table based on the power grid frequency and the phase of the master table.

[0011] Furthermore, S1 includes: S11. The master table sends phase detection notifications to all slave tables that need to perform phase detection in sequence through the RF module, triggering the slave tables to perform phase detection. S12. Upon receiving the phase detection notification, the slave table starts the MCU module to detect the grid voltage zero-crossing signal, and sends the phase detection notification and each detected grid voltage zero-crossing signal to the slave table RF module in sequence.

[0012] Furthermore, S2 includes: After the master MCU module completes the transmission of all phase detection notification frames, it sends the phase detection notification to the master RF module. At the same time, the master MCU module starts to detect the zero-crossing signal of the grid voltage. Each time the grid voltage zero-crossing is detected, the master RF module broadcasts and sends phase detection data frames to all slave RF modules that need to perform phase detection.

[0013] Furthermore, the master table RF module continuously broadcasts phase detection data frames within a preset time period to ensure that the slave table receives a sufficient amount of data; it does not perform collision detection to reduce the delay between zero-crossing signal notification and data transmission.

[0014] Furthermore, in S3, the time T1 and time T2 recorded by the RF module of the slave table are based on the slave table's local clock.

[0015] Furthermore, the repeated calculation of the master-slave table phase difference in S3 specifically includes: The RF module calculates the first phase difference Tphase based on the local clock. Tphase = T2 - T1 + delay, Among them, delay is the transmission delay from the time the master table starts its own MCU module to detect the zero-crossing signal of the power grid voltage to the time T1 when the slave table receives the data frame; Within a preset time period, the RF module continuously detects the grid voltage zero-crossing signal sent by the MCU module, obtains the first phase difference Tphase multiple times, and calculates the average value of the first phase difference Tphase_ave.

[0016] Furthermore, the transmission delay in S3 is dynamically adjusted using the following steps to improve phase detection accuracy; The initial value of the transmission delay is set to N (v / 10), where N is the number of bytes to be transmitted and v is the modulation rate; After each calculation of the first phase difference Tphase, the transmission delay correction value Tcorrection is calculated; T_correction = min[(T_phase % (1 / f)) - 0, (T_phase % (1 / f)) - (1 / 3f), (T_phase % (1 / f)) - (2 / 3f)]; The transmission delay is dynamically updated based on T-correction, where delay' = delay - T-correction; The RF module uses the updated transmission delay' to calculate the subsequent first phase difference Tphase, improving phase detection accuracy.

[0017] Furthermore, S4 includes: S41. The master table obtains the average value of the first phase difference Tphase_ave of each slave table through the RF module; S42. The master meter calculates the phase difference T between the master and slave meters based on the first average phase difference Tphase_ave and the grid frequency f. T = Tphase_ave % (1 / f) S43. Determine the phase of the slave meter according to the phase of the master meter and the phase difference T between the master and slave meters.

[0018] Further, in S43, determining the phase of the slave meter according to the phase of the master meter and the phase difference T between the master and slave meters is specifically as follows: If -1 / 6f < T ≤ 1 / 6f, it is determined that the slave meter is in the same phase as the master meter; If 1 / 6f < T ≤ 1 / 2f, it is determined that the phase of the slave meter lags behind the phase of the master meter by 120 degrees; If 1 / 2f < T ≤ 5 / 6f, it is determined that the phase of the slave meter lags behind the phase of the master meter by 240 degrees; The master meter determines that the phase where the slave meter is located is phase A, phase B or phase C according to the judgment result.

[0019] In a second aspect, the present invention provides an electric meter phase detection system based on an RF communication network, including a master meter and multiple slave meters; both the master meter and the slave meters include an MCU module and an RF communication module, and the master meter is directly connected and communicates with each slave meter through the RF communication module; wherein, The MCU module of the master meter is configured to: send a phase detection notification to all slave meters that need to perform phase detection, start detecting the grid voltage zero-crossing signal, and notify the RF communication module of the master meter when the zero-crossing signal is detected; obtain the first average phase difference calculated by each slave meter, and determine the phase where each slave meter is located according to the grid frequency and the phase of the master meter itself; The RF communication module of the master meter is configured to: receive the phase detection notification and the zero-crossing signal notification sent by the MCU module of the master meter, and broadcast a data frame to all slave meters every time the zero-crossing signal notification is received; The MCU module of the slave meter is configured to: start detecting the grid voltage zero-crossing signal after receiving the phase detection notification, and notify its RF communication module every time the zero-crossing signal is detected; The RF communication module of the slave meter is configured to: receive the phase detection notification sent by the MCU module of the slave meter and the broadcast data frame sent by the RF communication module of the master meter; record the reception time T1 every time the broadcast data frame of the master meter is received, and detect the first zero-crossing signal sent by the MCU module of the slave meter after receiving the data frame, record the time T2, calculate the first average phase difference according to the repeatedly recorded T1 and T2, and send the result to the master meter.

[0020] Advantages of the present invention: This invention discloses a power grid phase detection method based on RF module communication. It addresses the problem that the phase detection accuracy in a master-slave table network is affected by transmission delay and power grid frequency fluctuations. The method achieves high-precision phase detection by dynamically updating data transmission delay and using multi-sampling equalization technology.

[0021] This invention triggers the slave table to detect the zero-crossing signal of the power grid voltage by broadcasting a specific data frame from the master table. The slave table records the reception time and the zero-crossing time based on its local clock, calculates the first phase difference, and averages the results through 30 seconds of multi-sample sampling to reduce random errors. The master table determines the phase of the slave table based on the average of the first phase difference and the power grid frequency. Simultaneously, a formula for calculating the transmission delay is introduced, and the delay is dynamically adjusted based on the phase difference remainder to reduce the impact of transmission delay on detection accuracy.

[0022] Furthermore, no conflict detection is performed when the main table sends data, further reducing latency fluctuations and ensuring sufficient sample size. This invention significantly improves the accuracy and stability of phase detection by fusing latency optimization and multi-sample averaging, making it suitable for phase synchronization requirements in complex power grid environments.

[0023] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0024] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of the invention.

[0025] Figure 1 A schematic diagram of an application scenario according to an embodiment of the present invention is shown.

[0026] Figure 2 A schematic diagram of a meter phase detection method according to an embodiment of the present invention is shown.

[0027] Figure 3 One of the schematic diagrams of phase detection results according to an embodiment of the present invention is shown.

[0028] Figure 4 A second schematic diagram of phase detection results according to an embodiment of the present invention is shown.

[0029] Figure 5 The third schematic diagram shows the phase detection result according to an embodiment of the present invention. Detailed Implementation

[0030] Preferred embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0031] Example 1

[0032] like Figure 1 Electricity meter M1 is connected as the master meter to phase A of the power grid, while electricity meters M2, M3, and M4 are connected as slave meters to phases A, B, and C of the power grid, respectively. Each slave meter M2, M3, and M4 can communicate directly with the master meter M1 via an RF module.

[0033] Figure 2 A schematic diagram of a meter phase detection method according to an embodiment of the present invention is shown.

[0034] This invention provides a method for detecting the phase of an electricity meter based on an RF communication network. Both the master meter and slave meters include an MCU module and an RF module. The master meter communicates directly with multiple slave meters via the RF module. Figure 2 As shown, when phase detection is required, the following steps are performed: S1. The master table sends a phase detection notification to the slave table through the RF module. After receiving the notification, the slave table starts the MCU module to detect the zero-crossing signal of the grid voltage and notifies its RF module every time a zero-crossing signal is detected. Specifically, when phase detection is required, the master and slave tables communicate via an RF module. The master table notifies the slave table to perform phase detection. When the slave table receives the phase check command, it also notifies its RF module to perform phase detection. At this time, the slave table's MCU begins to detect the zero-crossing signal of the grid voltage, notifying its RF communication module each time it crosses zero. This process lasts for 30 seconds.

[0035] S2. After the master table sends the detection command, it starts its own MCU module to detect the zero-crossing signal of the power grid voltage and notifies the RF module. The RF module broadcasts a data frame to all slave tables every time it receives a zero-crossing signal. Specifically, after the master table notifies the slave table, the master table also notifies its own RF communication module to perform phase detection and start detecting the zero-crossing signal of the grid voltage. It notifies the RF communication module every time the voltage crosses zero, and this behavior lasts for 30 seconds.

[0036] After receiving a phase detection command, the RF communication module on the master table broadcasts a specific data frame to all slave tables that need phase detection each time it receives a zero-crossing signal notification from the MCU on the master table. When broadcasting the phase detection data frame, the master table RF module does not perform collision detection to reduce the delay between the zero-crossing signal notification and data transmission, ensuring that the slave tables receive a sufficient amount of data.

[0037] S3. Each time the slave RF module receives the master table broadcast data frame, record the reception time T1, and after receiving the data frame, detect the first zero-crossing signal sent by the slave MCU module and record the time T2; repeat multiple times to calculate the average value of the first phase difference. Specifically, when the RF module on the slave table receives a specific data frame, record the received time T1. After receiving the specific data frame, start detecting the zero-crossing signal notification of the slave table, and record the time T2 of the first zero-crossing signal notification from the slave MCU after receiving the data frame. The times T1 and T2 recorded by the slave table only need to be based on its own clock situation, and can also be just a time count, without requiring clock synchronization with the master table or other devices.

[0038] Then the slave RF module calculates the first phase difference Tphase according to the local clock. Tphase = T2 - T1 + delay, where delay is the transmission delay from the time when the master table starts to detect the zero-crossing signal of the grid voltage by its own MCU module to the time T1 when the slave table receives the data frame. As Figure 3 shown, the RF module of the slave table will detect Tphase multiple times within a detection time of 30s. When the number of detections reaches 30 times or the detection time arrives, stop further detection, and then add all the detected values to calculate the average value of the first phase difference Tphase_ave.

[0039] S4. The master table obtains the average value of the first phase difference calculated by each slave RF module, and determines the phase of each slave table according to the grid frequency and the master table phase.

[0040] Specifically, the master table obtains the average value of the first phase difference Tphase_ave of each slave table through the RF module; calculates the master-slave table phase difference T according to the average value of the first phase difference Tphase_ave and the grid frequency f; T = Tphase_ave % (1 / f); If -1 / 6f < T ≤ 1 / 6f, it is determined that the slave table is in the same phase as the master table; If 1 / 6f < T ≤ 1 / 2f, it is determined that the slave table lags behind the master table phase by 120 degrees; If 1 / 2f < T ≤ 5 / 6f, it is determined that the slave table lags behind the master table phase by 240 degrees; The master table determines that the phase of the slave table is phase A, phase B or phase C according to the judgment result.

[0041] Assume the master table is in phase A. If T≈0, the slave table is in phase A; if T≈1 / 3f, the slave table is in phase B; if T≈2 / 3f, the slave table is in phase C; As Figure 3 When both the master table and the slave table are in phase A, the calculated phase difference satisfies -1 / 6f < T ≤ 1 / 6f (when ignoring the time deviations in various processes and calculations, ideally, T = N*(1 / f), where N is an integer, and the remainder of T divided by 1 / f is 0). Similarly for T, as Figure 4 , when the master table is in phase A (blue line) and the slave table is in phase B (green line), the calculated phase difference at this time is T = 1 / 3f. As Figure 5 , when the master table is in phase A (blue line) and the slave table is in phase C (red line), the calculated phase difference at this time is T = 2 / 3f.

[0042] In one example, the value of the transmission delay delay is dynamically adjusted according to the actual situation. The initial value of delay is calculated as N (v / 10) based on the modulation rate and the number of transmitted bytes, where N is the number of transmitted bytes in units of Byte, and v is the modulation rate in units of bit / s.

[0043] After each calculation of the first phase difference Tphase, calculate the transmission delay correction value T correction; T correction = min[(Tphase % (1 / f)) - 0, (Tphase % (1 / f)) - (1 / 3f), (Tphase %(1 / f)) - (2 / 3f)]; Based on T correction, dynamically update the transmission delay, delay' = delay - T correction; The slave table RF module uses the updated transmission delay delay' to calculate the subsequent first phase difference Tphase, improving the phase detection accuracy.

[0044] In the present invention, by sending data from one master table and multiple slave tables detecting simultaneously, the efficiency of phase recognition is improved and the garbage data in the network is reduced. When phase detection is required, the master table notifies the slave tables, causing both the master and slave tables to enter the phase detection module and detect the phase, avoiding frequent phase detection and reducing the network busyness. The module on the slave table processes the zero-crossing signal notification after receiving the data. This avoids the ineffective processing when each zero-crossing signal is processed and there is a zero-crossing signal but the corresponding data has not been received, thus affecting the processing efficiency.

[0045] The device for performing phase detection only needs to perform calculations based on its own time and does not need to be time-synchronized with other devices, thus greatly reducing the implementation difficulty.

[0046] The slave table improves the accuracy of the detection result by averaging the values obtained from multiple detections; the dynamic adjustment of the data processing transmission time delay can also improve the accuracy of the detection result.

[0047] When sending data from the main table, no conflict detection is performed to reduce unnecessary time consumption during the data transmission and reception process, thereby improving detection accuracy. Data transmission time is 30 seconds to avoid situations where the number of detected samples is insufficient due to data transmission failures.

[0048] Example 2

[0049] This invention provides a meter phase detection system based on an RF communication network, comprising a master meter and multiple slave meters; both the master meter and the slave meters include an MCU module and an RF communication module, and the master meter and each slave meter communicate directly via the RF communication module; wherein, The MCU module of the master table is configured to: send a phase detection notification to all slave tables that need to perform phase detection, start detecting the zero-crossing signal of the grid voltage, and notify the RF communication module of the master table when the zero-crossing signal is detected; obtain the average value of the first phase difference calculated by each slave table, and determine the phase of each slave table according to the grid frequency and the phase of the master table itself; The RF communication module of the master table is configured to receive phase detection notifications and zero-crossing signal notifications sent by the master table MCU module, and broadcast data frames to all slave tables each time a zero-crossing signal notification is received. The MCU module of the slave table is configured to: upon receiving a phase detection notification, initiate the detection of the grid voltage zero-crossing signal, and notify its RF communication module each time a zero-crossing signal is detected; The RF communication module of the slave table is configured to: receive phase detection notifications sent by the slave table MCU module and broadcast data frames sent by the master table RF communication module; record the reception time T1 each time a broadcast data frame from the master table is received, and detect the first zero-crossing signal sent by the slave table MCU module after receiving the data frame, record the time T2, calculate the average value of the first phase difference based on the multiple recorded T1 and T2, and send the result to the master table.

[0050] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for detecting the phase of an electricity meter based on an RF communication network, characterized in that... Both the master meter and the slave meter include an MCU module and an RF module. The master meter communicates directly with multiple slave meters through the RF module. The meter phase detection method includes the following steps. S1. The master table sends a phase detection notification to the slave table through the RF module. After receiving the notification, the slave table starts the MCU module to detect the zero-crossing signal of the grid voltage and notifies its RF module every time a zero-crossing signal is detected. S2. After the master table sends the detection command, it starts its own MCU module to detect the zero-crossing signal of the power grid voltage and notifies the RF module. The RF module broadcasts a data frame to all slave tables every time it receives a zero-crossing signal. S3. Each time the RF module receives a broadcast data frame from the master table, it records the reception time T1. After receiving the data frame, it detects the first zero-crossing signal sent by the MCU module of the slave table and records the time T2. Repeat this process multiple times to calculate the average value of the first phase difference. S4. The master table obtains the average value of the first phase difference calculated by the RF module of each slave table, and determines the phase of each slave table based on the power grid frequency and the phase of the master table.

2. The meter phase detection method based on RF communication network as described in claim 1, characterized in that... S1 includes: S11. The master table sends phase detection notifications to all slave tables that need to perform phase detection in sequence through the RF module, triggering the slave tables to perform phase detection. S12. Upon receiving the phase detection notification, the slave table starts the MCU module to detect the grid voltage zero-crossing signal, and sends the phase detection notification and each detected grid voltage zero-crossing signal to the slave table RF module in sequence.

3. The meter phase detection method based on RF communication network as described in claim 1, characterized in that S2 include: After the master MCU module completes the transmission of all phase detection notification frames, it sends the phase detection notification to the master RF module. At the same time, the master MCU module starts to detect the zero-crossing signal of the grid voltage. Each time the grid voltage zero-crossing is detected, the master RF module broadcasts and sends phase detection data frames to all slave RF modules that need to perform phase detection.

4. The meter phase detection method based on RF communication network as described in claim 3, characterized in that... The main table RF module continuously broadcasts phase detection data frames within a preset time period to ensure that the slave table receives a sufficient amount of data; it does not perform conflict detection to reduce the delay between zero-crossing signal notification and data transmission.

5. The meter phase detection method based on RF communication network as described in claim 1, characterized in that... In S3, the time T1 and time T2 recorded by the RF module are based on the local clock of the slave table.

6. The meter phase detection method based on RF communication network as described in claim 1, characterized in that... In S3, repeatedly calculating the phase difference between the master and slave tables specifically includes: The RF module calculates the first phase difference Tphase based on the local clock. Tphase = T2 - T1 + delay, Among them, delay is the transmission delay from the time the master table starts its own MCU module to detect the zero-crossing signal of the power grid voltage to the time T1 when the slave table receives the data frame; Within a preset time period, the RF module continuously detects the grid voltage zero-crossing signal sent by the MCU module, obtains the first phase difference Tphase multiple times, and calculates the average value of the first phase difference Tphase_ave.

7. The meter phase detection method based on an RF communication network as described in claim 6, characterized in that... In S3, the transmission delay is dynamically adjusted using the following steps to improve phase detection accuracy; The initial value of the transmission delay is set to N (v / 10), where N is the number of bytes to be transmitted and v is the modulation rate; After each calculation of the first phase difference Tphase, the transmission delay correction value Tcorrection is calculated; T_correction = min[(T_phase % (1 / f)) - 0, (T_phase % (1 / f)) - (1 / 3f), (T_phase % (1 / f)) - (2 / 3f)]; The transmission delay is dynamically updated based on T-correction, where delay' = delay - T-correction; The RF module uses the updated transmission delay' to calculate the subsequent first phase difference Tphase, improving phase detection accuracy.

8. The meter phase detection method based on RF communication network as described in claim 1, characterized in that S4 include: S41. The master table obtains the average value of the first phase difference Tphase_ave of each slave table through the RF module; S42. The master table calculates the master-slave table phase difference T based on the average value of the first phase difference Tphase_ave and the power grid frequency f. T = Tphase_ave % (1 / f) S43. Determine the phase of the slave table based on the phase of the master table and the phase difference T between the master and slave tables.

9. The meter phase detection method based on an RF communication network as described in claim 8, characterized in that... In S43, the phase of the slave table is determined based on the phase of the master table and the phase difference T between the master and slave tables as follows: If -1 / 6f < T ≤ 1 / 6f, then the slave table and the master table are in phase. If 1 / 6f < T ≤ 1 / 2f, then the slave table lags the master table by 120 degrees in phase. If 1 / 2f < T ≤ 5 / 6f, then the slave table lags the master table by 240 degrees in phase. The main table determines whether the phase of the slave table is phase A, phase B, or phase C based on the judgment result.

10. A meter phase detection system based on an RF communication network, characterized in that, It includes a master table and multiple slave tables; both the master table and the slave tables include an MCU module and an RF communication module, and the master table and each slave table communicate directly through the RF communication module; wherein, The MCU module of the master table is configured to: send a phase detection notification to all slave tables that need to perform phase detection, start detecting the zero-crossing signal of the grid voltage, and notify the RF communication module of the master table when the zero-crossing signal is detected; obtain the average value of the first phase difference calculated by each slave table, and determine the phase of each slave table according to the grid frequency and the phase of the master table itself; The RF communication module of the master table is configured to receive phase detection notifications and zero-crossing signal notifications sent by the master table MCU module, and broadcast data frames to all slave tables each time a zero-crossing signal notification is received. The MCU module of the slave table is configured to: upon receiving a phase detection notification, initiate the detection of the grid voltage zero-crossing signal, and notify its RF communication module each time a zero-crossing signal is detected; The RF communication module of the slave table is configured to: receive phase detection notifications sent by the slave table MCU module and broadcast data frames sent by the master table RF communication module; record the reception time T1 each time a broadcast data frame from the master table is received, and detect the first zero-crossing signal sent by the slave table MCU module after receiving the data frame, record the time T2, calculate the average value of the first phase difference based on the multiple recorded T1 and T2, and send the result to the master table.

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