A time correction method and system based on Beidou-cco fusion

Abstract

This invention discloses a time synchronization method and system based on BeiDou-CCO fusion. The method includes the following steps: S1: The CCO starts the BeiDou receiving unit according to a preset cycle, first receiving satellite signals and calculating the UTC time; then generating the corresponding network time base NTB based on the UTC time; S2: The time synchronization message is broadcast to each STA slave node device in the area via a dual-mode communication unit; S3: Each STA slave node device calculates the comprehensive clock deviation Δt; S4: Each STA slave node device is controlled to perform hierarchical time synchronization according to the corresponding |Δt| magnitude. This invention uses a fusion architecture with master station network time synchronization as the core and BeiDou satellite time synchronization as a supplement. By integrating the BeiDou receiving module through the CCO, a distributed time synchronization network is constructed, and dynamic time synchronization and protocol optimization are performed to achieve higher precision clock synchronization.

Description

Technical Field

[0001] This invention relates to the technical field of synchronous collection of electricity consumption information in power systems, specifically to a time synchronization method and system based on BeiDou-CCO fusion. Background Technology

[0002] In the electricity marketing and metering system, the accuracy of electricity meter clocks is the core foundation for ensuring the implementation of time-of-use pricing, electricity market settlement, and data traceability.

[0003] Currently, smart meters commonly suffer from clock inconsistencies due to factors such as hardware clock chip drift and communication delays. Traditional time synchronization solutions mainly rely on concentrators to perform periodic time synchronization via HPLC (High-Speed ​​Power Line Carrier) networks, which has the following significant drawbacks: long synchronization cycles (weekly / daily), insufficient real-time performance, and difficulty in meeting the high-frequency time synchronization requirements brought about by the grid connection of new energy sources; low time synchronization accuracy (minute-level), failing to meet the second-level time reference requirements for refined electricity market settlement; reliance on master station network transmission, making them prone to time synchronization failures during communication congestion or interruptions; and lack of dynamic adaptation mechanisms, using a single time synchronization strategy for meters with severe clock inconsistencies can easily lead to data jumps.

[0004] While GPS timing technology has been successfully applied abroad, directly adopting foreign technology may pose national security risks and lack deep integration with power data acquisition systems. Although China's BeiDou-3 system has a 20-nanosecond timing capability, existing BeiDou modules often suffer from high power consumption (standby current > 50mA), high cost, and insufficient compatibility with HPLC protocols, which restricts large-scale deployment in the field of power data acquisition.

[0005] Therefore, there is an urgent need to build a new time synchronization system that integrates BeiDou high-precision time synchronization with the main station network time synchronization to solve the technical bottlenecks of traditional solutions. Summary of the Invention

[0006] To address the aforementioned issues, the purpose of this invention is to propose a time synchronization method and system based on BeiDou-CCO fusion. This system employs a fusion architecture with master station network time synchronization as the core and BeiDou satellite time synchronization as a supplement. By integrating BeiDou receiving modules through CCO, a distributed time synchronization network is constructed, enabling dynamic time synchronization and protocol optimization to achieve higher precision clock synchronization.

[0007] This was achieved through the following technical solutions: First, a time synchronization method based on BeiDou-CCO fusion is proposed, including the following steps: S1: The CCO starts the BeiDou receiving unit according to a preset cycle, first receiving satellite signals and calculating the UTC time; then generating the corresponding network time base NTB based on the UTC time. S2: The CCO synchronizes a synchronization message containing the Network Time Base (NTB) to each STA slave node device within the area via a broadcast method through a dual-mode communication unit; the dual-mode communication unit includes an HPLC channel and an HRF channel. S3: After each STA receives the synchronization message from the node device, it calculates the overall clock deviation Δt; where Δt is set with an adaptive threshold, a static threshold and a precise threshold, and the static threshold is the default threshold of the adaptive threshold; S4: Control each STA slave node device to perform hierarchical time synchronization according to the corresponding |Δt| value: if |Δt|≤adaptive threshold, directly correct the local clock deviation of the corresponding STA slave node device; if the adaptive threshold<|Δt|≤ΔT_total, use the improved Kalman filter algorithm to perform dynamic compensation time synchronization; if |Δt|>ΔT_total, start the step time synchronization mechanism and generate an out-of-tolerance event to report to the master station time server; ΔT_total is the preset daily correction step size upper limit.

[0008] Optionally, in step S1, the formula for generating the network time base NTB is: NTB_k = T_BD_k - T_prop_k - T_proc, where NTB_k is the network time base calculated by CCO for the kth time, k is a positive integer, T_BD_k is the UTC time for the kth time, T_prop_k is the median of the delay reported by the STA from the node device during the previous k-1 measurements, and T_proc is a fixed compensation value.

[0009] Optionally, in step S2, the dual-mode communication unit has a built-in channel quality assessment unit (CQE) for real-time detection of the signal-to-noise ratio (SNR) of the HPLC channel. When the SNR is lower than the preset value I, it automatically switches to the HRF channel. The time synchronization command is transmitted simultaneously in the HRF channel and the HPLC channel. The STA slave node device takes the average of the timestamps of the two signals and calculates the variance. When the variance exceeds the preset value II, the abnormal frames in the time synchronization message are discarded.

[0010] Optionally, in step S3, calculating the overall clock deviation Δt includes: using historical communication data to calculate the estimated value of the channel round-trip time T_rtt=(T_recv-T_BD_k)-T_proc, and then calculating the overall clock deviation according to the formula Δt=(T_local-NTB_k)+α×T_rtt, where α is the channel asymmetry compensation coefficient, T_local is the time when the STA reads the local clock from the node device, and T_recv is the time when the NTB message is received as recorded by the local clock.

[0011] Optionally, in step S4, an improved Kalman filter algorithm is used to perform dynamic compensation time synchronization, defining the state vector as [clock skew δ, clock drift rate ω]. TT represents transpose, the process noise matrix Q is dynamically adjusted based on the measurement residual, the observation matrix H=[1, -T_interval], the estimated value of the channel round-trip time delay T_rtt is used as the observation, and the output is a smooth clock compensation value, where T_interval is the interval between two time synchronizations.

[0012] Optionally, in the step-time synchronization mechanism of step S4, the single correction step size ΔT_step = ΔT_total × γ, where γ is the correction coefficient and can be taken as 0.1 to 0.2, and ΔT_total is the preset daily correction step size upper limit; the adaptive threshold is dynamically updated through a sliding window: the mean μ and variance σ² corresponding to the |Δt| of the most recent W time synchronizations are recorded, where σ is the standard deviation; when μ+2σ exceeds the static threshold by 0.5 seconds, the precise threshold is automatically increased to μ+2σ and the precise threshold is used to replace the static threshold.

[0013] Optionally, it also includes a three-level progressive integrity check: save a snapshot of the power energy data before time synchronization; calculate the power consumption difference ΔE within ΔT_total after time synchronization, and freeze the current period data if ΔE exceeds a preset threshold; and report the snapshot and deviation value to the master station for verification. When the master station determines that there is an anomaly, it issues a data recovery command, and the STA slave node device overwrites the abnormal data with the snapshot.

[0014] Secondly, a time synchronization system based on BeiDou-CCO fusion is proposed, which operates using the aforementioned time synchronization method. The time synchronization system includes a BeiDou-CCO fusion module, a master time server, and each STA slave node device. The BeiDou-CCO fusion module includes a BeiDou receiving unit and a dual-mode communication unit. The BeiDou receiving unit is used to receive the time signal from the BeiDou satellite or the network time from the master time server, generate the network time reference NTB, and broadcast time synchronization commands. The dual-mode communication unit includes an HPLC channel and an HRF channel. The master time server is used to provide a standard time reference UTC as a redundant time source for the time signal. The STA slave node devices are used to receive the time synchronization messages from the master time server, monitor the local clock deviation of the STA slave node devices, and perform clock calibration. The BeiDou-CCO fusion module and the STA slave node devices are connected through the dual-mode communication unit, and the communication link is dynamically selected according to the channel quality to achieve distributed clock synchronization.

[0015] Optionally, the Beidou-CCO fusion module adopts a four-layer PCB stack-up design. In order from top to bottom, the top layer is arranged with Beidou radio frequency circuit as Beidou receiving unit, the second layer is divided into an independent power supply area for signal and power isolation, the third layer is arranged with MCU and RTC crystal oscillator and used as control center, and the bottom layer is arranged with HPLC baseband and HRF transceiver module and used as dual-mode communication unit.

[0016] Optionally, the master time server and each STA slave node device use the national cryptographic SM4-CBC encrypted time synchronization command. When the time synchronization command instructs the broadcast of the corresponding time synchronization message, a one-time session key KS is derived based on the station symmetric master key KM to perform two-way identity authentication and SM3 HMAC signature verification.

[0017] The beneficial effects of this invention compared to the prior art are: 1) Through intelligent time synchronization algorithm and dual time source redundancy design, breakthrough optimization of time synchronization accuracy and response speed is achieved, meeting the needs of refined settlement in the power market and significantly improving system operating efficiency and data real-time performance.

[0018] 2) Deeply integrate the domestic BeiDou timing system with national cryptographic algorithms to eliminate the risk of external dependence; the seamless switching mechanism of dual time sources ensures the continuity of time synchronization under extreme conditions, greatly enhances the system's risk resistance, and ensures data security and reliability.

[0019] 3) It adopts low-power integration technology to reduce hardware costs and maintenance burden, is compatible with the protocol extension design of the existing power acquisition architecture, realizes low-cost upgrade and transformation, and supports advanced smart grid applications in the future. It has broad promotion value and technological foresight. Attached Figure Description

[0020] Figure 1 This is a diagram of a fusion time synchronization system architecture based on BeiDou-CCO. Figure 2 A flowchart for the dynamic time synchronization strategy; Figure 3 Logic diagram for STA clock skew hierarchical processing; Figure 4 This is a flowchart of a fusion time synchronization method based on BeiDou-CCO. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0022] like Figure 4 The diagram shows a flowchart of a fusion time synchronization method based on BeiDou-CCO. Through a fusion architecture with the main station network time synchronization as the core and BeiDou satellite time synchronization as a supplement, the CCO integrates the BeiDou receiving module to build a distributed time synchronization network, perform dynamic time synchronization and protocol optimization, and achieve higher precision clock synchronization.

[0023] The method specifically includes the following steps: S1: The CCO starts the BeiDou receiving unit at a preset cycle, first receiving satellite signals and calculating the UTC time; then generating the corresponding network time base NTB based on the UTC time. For example: the CCO starts the BeiDou receiving module every 30 minutes, continuously receiving satellite signals for 30 seconds, calculating the accurate UTC time, and then obtaining the network time base NTB. It then broadcasts this information to synchronize all STA (Station) slave node devices in the area. The default broadcast cycle is 1 hour, which can be set remotely by the master station.

[0024] NTB (Network Time Base) is a regional relative time base, generated by eliminating channel propagation delay using BeiDou UTC time as the source, thus providing a unified reference for all STA slave nodes within the region. The formula for generating the Network Time Base (NTB) is: NTB_k = T_BD_k - T_prop_k - T_proc; where NTB_k is the network time base calculated by the CCO in the k-th iteration, and k is a positive integer; T_BD_k is the precise UTC time obtained by the CCO from the BeiDou module in the k-th timing window; T_prop_k is the estimated propagation delay of the HPLC channel broadcast, which is also the median of the delay reported by the STA slave nodes during the previous k-1 measurements; and T_proc is a fixed compensation value for CCO processing delay (e.g., 2ms).

[0025] S2: The CCO synchronizes a synchronization message containing the Network Time Base (NTB) to each STA slave node device within the area via broadcast through a dual-mode communication unit. The dual-mode communication unit includes an HPLC channel and an HRF channel. Both channels use unified frame sequence number management; for example, both channels share a 16-bit frame sequence number space, thus preventing frame sequence number confusion and message replay attacks caused by channel switching.

[0026] The dual-mode communication unit has a built-in Channel Quality Evaluation (CQE) unit for real-time monitoring of the signal-to-noise ratio (SNR) of the HPLC channel. When the SNR falls below a preset value I (e.g., 15 dB), it automatically switches to the HRF channel for transmission through a higher-quality channel. Time synchronization commands are transmitted simultaneously on both the HRF and HPLC channels to instruct the synchronization message. Each STA slave node takes the average of the timestamps of the corresponding signals in both channels and calculates the variance. If the variance exceeds a preset value II (e.g., 50 ms), abnormal frames in the synchronization message are discarded, thus eliminating time synchronization errors caused by sudden changes in single-channel delay.

[0027] As shown in Table 1 below, the HPLC extended message frame format used when transmitting through the HPLC channel is illustrated. This extends the HPLC protocol, adds a dedicated field for BeiDou time synchronization, and achieves seamless integration with existing acquisition systems. Table 1:

[0028] A dynamic time source selection mechanism is also set up for the CCO. The CCO will compare the BeiDou time with the main station time in real time. When the deviation between the two is less than or equal to the set value (e.g., 1 second), the BeiDou time will be used first for broadcast time synchronization. When the deviation is greater than the set value, the main station time synchronization will be triggered to ensure the consistency of the time reference.

[0029] S3: After each STA receives the synchronization message from the node device, it calculates the overall clock deviation Δt; where Δt is set with an adaptive threshold, a static threshold and a precise threshold, and the static threshold is the default threshold of the adaptive threshold.

[0030] The calculation of the overall clock offset Δt includes: calculating the estimated channel round-trip time T_rtt = (T_recv - T_BD_k) - T_proc using historical communication data, and then calculating the overall clock offset using the formula Δt = (T_local - NTB_k) + α × T_rtt, where α is the channel asymmetry compensation coefficient (between 0 and 1, adaptively updated from historical statistics, with an initial value of 0.5), T_local is the time when the STA reads the local clock from the node device, and T_recv is the time when the NTB message is received, recorded by the local clock. Compared with fixed delay compensation, this method can be dynamically adjusted according to the communication conditions of the distribution area, eliminating the system error introduced by unidirectional propagation asymmetry.

[0031] S4: Control each STA slave node device to perform hierarchical time synchronization according to the corresponding |Δt| value.

[0032] like Figure 3 The diagram shown is a logic diagram for hierarchical processing of STA clock skew, combined with... Figure 3 As shown, during the hierarchical time synchronization process, if |Δt|≤adaptive threshold, the local clock deviation of the corresponding STA slave node device is directly corrected; if the adaptive threshold<|Δt|≤ΔT_total (the preset daily correction step size upper limit, for example, 5 minutes), an improved Kalman filter algorithm is used to perform dynamic compensation time synchronization to adapt to the time-varying delay characteristics of the power line channel; if |Δt|>ΔT_total, the step-time synchronization mechanism is activated and an out-of-tolerance event is generated and reported to the master time server.

[0033] like Figure 2 The diagram shown is a flowchart of a dynamic time synchronization strategy, combined with... Figure 4 and Figure 2 As shown, when using the improved Kalman filter algorithm to perform dynamic compensation time synchronization, the state vector is defined as [clock skew δ, clock drift rate ω]. T T denotes transpose; the adaptive process noise matrix Q is based on the measurement residual. Dynamic adjustment, z k Used to refer to the k-th T_rtt, when |rk When the deviation exceeds twice the standard deviation, the process noise variance in the deviation dimension of the automatic amplification process noise matrix Q is increased, causing the filter to respond quickly to sudden clock jumps (such as large deviations after a power outage and restart of an electricity meter); the observation matrix H=[1, -T_interval] corresponding to the propagation delay is used as the estimated value of the channel round-trip time delay T_rtt as the observation, and a smooth clock compensation value is output, where T_interval is the interval between two time synchronizations.

[0034] The core formula of the improved Kalman filter is as follows: 1) State prediction: The state transition matrix A = [[1, T_interval], [0, 1]], and the control input B·u k-1 Here, B is the frequency compensation control variable, and u is the control matrix. k-1 This is the frequency compensation command (0 if not applied), the superscript - indicates prior information. It is the prior estimate of the state at time k, predicted based on the estimate at time k-1; 2) Error covariance prediction: P k - =A·P k-1 ·A T +Q(r k ), the process noise matrix Q is dynamically updated according to the residual; 3) Kalman gain: K k =P k - ·H T ·(H·P k - ·H T +R) -1 Here, the superscript T indicates transpose, the superscript -1 indicates matrix inversion, and R is the noise covariance matrix determined based on the process noise matrix Q; 4) State update: ;5) Error covariance update: P k =(IK k ·H)·P k - I is the identity matrix. During dynamic compensation time synchronization, clock deviation and drift rate are used as state variables, and the process noise matrix Q is used to uniformly handle both sudden and gradual clock anomalies, outputting a smooth and stable compensation value to avoid time synchronization jumps. Actual verification data shows that it can eliminate more than 85% of channel delay jitter.

[0035] In the step-time synchronization mechanism, the single correction step size ΔT_step = ΔT_total × γ, where γ is the correction coefficient (which can be 0.1 to 0.2), and ΔT_total is the preset daily correction step size upper limit. The upper limit of the single correction step size can be limited to 5 minutes. The calibration is performed step by step using small steps, multiple cycles, and unidirectional approximation to prevent jumps in power data.

[0036] When dynamically updating the adaptive threshold via a sliding window, the mean μ and variance σ² of the |Δt| corresponding to the most recent W times (W is a positive integer, such as 10 times) of time synchronization are first recorded, where σ is the standard deviation. When μ+2σ exceeds the static threshold by 0.5 seconds, the precise threshold is automatically increased to μ+2σ and the precise threshold is used to replace the static threshold. This prevents frequent triggering of high-level time synchronization procedures due to channel jitter and reduces invalid time synchronization operations.

[0037] It should be noted that, considering the possibility of BeiDou signal loss, this solution also includes the following special scenario handling mechanisms: 1) When the CCO fails to receive BeiDou satellite signals for three consecutive times, it automatically switches to master station time synchronization mode, requesting standard time from the master station every two hours to maintain the time synchronization function. 2) Communication interruption recovery: After communication is restored, the STA immediately and proactively requests the latest time synchronization command from the CCO to avoid the accumulation of clock deviations. 3) Clock jump protection and multi-level progressive integrity verification.

[0038] The prerequisites for triggering the special scenario handling mechanism are as follows: the current meter reading has been frozen normally (including hourly and daily freeze); the time adjustment amount |Δt| > 0.1 seconds (verification will not be triggered if it is lower than this value); the communication link is normal and the STA can upload a verification report to the CCO.

[0039] In multi-level progressive integrity verification, the first level is data snapshotting. Before the time synchronization command is executed, the corresponding STA slave node device automatically saves a snapshot of key metering data such as current energy and demand (the snapshot is stored in the local Flash non-volatile area and does not occupy normal frozen space). The second level is jump detection. Within 5 minutes after the time synchronization is completed, the STA slave node device compares the snapshot data with the real-time data after the time synchronization and calculates the power consumption difference ΔE=|E_after-E_before|, where E_before refers to the power consumption data saved before the time synchronization, and E_ "after" refers to the real-time power consumption data after time synchronization. If ΔE exceeds the preset threshold (default 0.1kWh), data freeze lock is triggered, and the current freeze period data will no longer be updated to prevent abnormal data from being written. The third level is master station verification and recovery. The STA slave node device reports the snapshot data, deviation value Δt, ΔE and trigger time to the master station. The master station combines the historical power consumption model of the transformer area to determine whether it is a normal jump. If it is determined to be abnormal, a data recovery command is issued. The STA slave node device overwrites the current abnormal frozen data with the snapshot data and generates a data correction record for archiving.

[0040] It should also be noted that if the snapshot fails to be saved (e.g., Flash write error), the current time synchronization operation will be suspended, the error code will be recorded, and the system will wait for the next time synchronization window to retry. If the main station verification times out (no response for more than 24 hours), the STA will automatically unlock the data freeze and resume normal data collection, while retaining the error record. All error handling processes generate timestamped audit logs, which are reported to the main station through an encrypted channel.

[0041] Secondly, such as Figure 1 The diagram shown is an architecture diagram of a fusion time synchronization system based on BeiDou-CCO, which operates using the aforementioned time synchronization method, combined with... Figure 1 As shown, the time synchronization system includes a BeiDou-CCO fusion module, a master time server (referred to as the master station), and slave node devices for each STA. The BeiDou-CCO fusion module is installed at the concentrator end, and each STA slave node device is installed at the electricity meter end.

[0042] The BeiDou-CCO fusion module includes a BeiDou receiving unit and a dual-mode communication unit. The BeiDou receiving unit receives timing signals from BeiDou satellites or network time from the master time server, generates a network time base (NTB), and broadcasts time synchronization commands. The dual-mode communication unit includes an HPLC channel and an HRF channel. The master time server provides a standard time base (UTC) as a redundant time source for timing signals. The STA slave node devices have built-in high-precision RTC clocks (RTC stands for Real-Time Clock, with a daily drift of ≤0.5 seconds). The STA slave node devices receive synchronization messages from the master time server, monitor local clock deviations, and perform clock calibration. The BeiDou-CCO fusion module and the STA slave node devices are connected through the dual-mode communication unit, and the communication link is dynamically selected based on channel quality to achieve distributed clock synchronization.

[0043] The BeiDou-CCO fusion module adopts a four-layer PCB stack-up design. Following the top-to-bottom order, the top layer houses the BeiDou RF circuitry as the BeiDou receiver unit, including a BeiDou B1I / B2a dual-band LNA (Low Noise Amplifier) ​​and filtering circuitry. The antenna feed port is connected to the module body via a short-distance microstrip line to reduce RF loss. The second layer is divided into independent power supply areas for signal and power isolation. For example, the BeiDou RF power supply area is independently separated from the HPLC digital power supply area, with power isolation achieved through ferrite beads and filter capacitors. The peak operating current of the BeiDou module does not exceed 30mA, and the standby current is ≤10mA. The third layer houses the MCU (Microcontroller Unit) and RTC crystal oscillator, serving as the control center. It includes a low-power MCU (48MHz), RTC crystal oscillator, and serial communication interface. A low-power sleep mode is used to compress the total module standby current to ≤5mA during non-timing windows. The bottom layer houses the HPLC baseband and HRF transceiver modules, serving as the dual-mode communication unit. The top layer serves as the signal layer, the second layer as the power / ground layer, the third layer as the digital layer, and the ground layer as the HPLC / HRF layer. This multi-layer stacked design achieves electromagnetic isolation between the Beidou radio frequency unit and the power line communication unit.

[0044] After the master time server receives an out-of-range event from any STA slave device, both the master time server and the corresponding STA slave device will use the national cryptographic SM4-CBC encryption to encrypt the time synchronization command. The encrypted fields cover the target timestamp (8 bytes), deviation value (4 bytes), and operation type (1 byte). Simultaneously, a key management mechanism is employed. Each area CCO holds an independent area symmetric master key (KM), which is issued by the master station through a secure channel. Each time a time synchronization command is broadcast, a one-time session key KS is derived from the KM and encrypted, for example, using the ECB (Electronic Codebook) working mode of the national cryptographic SM4 block cipher algorithm, ensuring that the time synchronization key is not reused for each time. Furthermore, a two-way authentication process is set up: 1) The master station sends a challenge code Nonce (random 16 bytes) to the target meter; 2) The meter returns a response with an SM4 encrypted Nonce + meter ID; 3) The master station can only issue a time synchronization command after verifying the response. After receiving the command, the meter verifies the SM3 HMAC signature, and performs a clock write operation after successful verification. It should be noted that SM4-CBC refers to the CBC (Cipher Block Chaining) working mode of the national cryptographic SM4 block cipher algorithm (GB / T32907-2016); SM3 HMAC refers to HMAC (Hash-based Message Authentication Code) built based on the national cryptographic SM3 cryptographic hash algorithm (GB / T32905-2016).

[0045] Based on the above time synchronization method and system, practical verification was conducted: 10 residential transformer substations within the province, each with 64-128 households, using HPLC+HRF dual-mode communication and BeiDou-3 dual-frequency time synchronization; verification period: continuous and stable operation for 90 days; comparative test results are shown in Table 2 below: Table 2:

[0046] As shown in Table 2, the proposed scheme with BeiDou + CCO dual time sources has no single-point failure and provides continuous and reliable time synchronization. The improved Kalman filter can eliminate more than 85% of channel delay jitter, which is superior to the traditional single-dimensional filtering scheme. The step-time synchronization completely eliminates abnormal jumps in power data. The multi-level progressive integrity verification effectively ensures the data security of the time synchronization process. Overall, it meets the business requirements of second-level settlement and millisecond-level event recording, and the technical effects are reproducible and verifiable.

[0047] In summary, this invention integrates a BeiDou and power line communication module at the concentrator CCO terminal, converting expensive satellite time synchronization capabilities into a network time base (NTB) for the distribution area, which is then broadcast to all electricity meters to achieve high-precision time synchronization. It employs improved Kalman filtering and dynamic adaptive thresholding to effectively eliminate channel delay jitter and prevent invalid time synchronization caused by channel quality fluctuations, significantly improving the success rate and reliability of time synchronization. Furthermore, through step-time synchronization, multi-level clock transition verification, and national cryptographic encryption authentication, it completely eliminates data mutations during the time synchronization process and blocks external attacks. Thus, while meeting second-level settlement requirements, it significantly enhances the security and data integrity of the entire system, demonstrating significant advancements.

[0048] The above embodiments are merely illustrative of the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solutions based on the technical concept proposed in this invention shall fall within the scope of protection of this invention.

Claims

1. A time synchronization method based on BeiDou-CCO fusion, characterized in that, Includes the following steps: S1: The CCO starts the BeiDou receiving unit according to a preset cycle, first receiving satellite signals and calculating the UTC time; then generating the corresponding network time base NTB based on the UTC time. S2: The CCO synchronizes a synchronization message containing the Network Time Base (NTB) to each STA slave node device within the area via a broadcast method through a dual-mode communication unit; the dual-mode communication unit includes an HPLC channel and an HRF channel. S3: After each STA receives the synchronization message from the node device, it calculates the overall clock deviation Δt; where Δt is set with an adaptive threshold, a static threshold and a precise threshold, and the static threshold is the default threshold of the adaptive threshold; S4: Control each STA slave node device to perform hierarchical time synchronization according to the corresponding |Δt| value: if |Δt|≤adaptive threshold, directly correct the local clock deviation of the corresponding STA slave node device; if the adaptive threshold<|Δt|≤ΔT_total, use the improved Kalman filter algorithm to perform dynamic compensation time synchronization; if |Δt|>ΔT_total, start the step time synchronization mechanism and generate an out-of-tolerance event to report to the master station time server; ΔT_total is the preset daily correction step size upper limit.

2. The time synchronization method based on BeiDou-CCO fusion according to claim 1, characterized in that, In step S1, the formula for generating the network time base NTB is: NTB_k = T_BD_k - T_prop_k - T_proc, where NTB_k is the network time base calculated by CCO for the kth time, k is a positive integer, T_BD_k is the UTC time for the kth time, T_prop_k is the median of the delay reported by the STA from the node device during the previous k-1 measurements, and T_proc is a fixed compensation value.

3. The time synchronization method based on BeiDou-CCO fusion according to claim 1, characterized in that, In step S2, the dual-mode communication unit has a built-in channel quality assessment unit (CQE) for real-time detection of the signal-to-noise ratio (SNR) of the HPLC channel. When the SNR is lower than the preset value I, it automatically switches to the HRF channel. The time synchronization command is transmitted simultaneously in the HRF channel and the HPLC channel. The STA slave node device takes the average of the timestamps of the two signals and calculates the variance. When the variance exceeds the preset value II, the abnormal frames in the time synchronization message are discarded.

4. The time synchronization method based on BeiDou-CCO fusion according to claim 1, characterized in that, In step S3, calculating the overall clock deviation Δt includes: using historical communication data to calculate the estimated value of the channel round-trip time T_rtt=(T_recv-T_BD_k)-T_proc, and then calculating the overall clock deviation according to the formula Δt=(T_local-NTB_k)+α×T_rtt, where α is the channel asymmetry compensation coefficient, T_local is the time when the STA reads the local clock from the node device, and T_recv is the time when the NTB message is received as recorded by the local clock.

5. The time synchronization method based on BeiDou-CCO fusion according to claim 4, characterized in that, The dynamic compensation time correction is performed in step S4 by using the improved Kalman filter algorithm, and the state vector is defined as [clock bias δ, clock drift rate ω] T , T represents transposition, the process noise matrix Q is dynamically adjusted according to the measurement residual, the observation matrix H = [1, -T_interval], the estimated value T_rtt of the channel round-trip delay is used as the observation, the smoothed clock compensation value is output, and T_interval is the time interval between two corrections.

6. The time synchronization method based on BeiDou-CCO fusion according to claim 1, characterized in that, In the step-time synchronization mechanism of step S4, the single correction step size ΔT_step = ΔT_total × γ, where γ is 0.1 to 0.2; The adaptive threshold is dynamically updated through a sliding window: the mean μ and variance σ² corresponding to the most recent W time calibrations are recorded, where σ is the standard deviation; when μ+2σ exceeds the static threshold by 0.5 seconds, the precise threshold is automatically increased to μ+2σ and the static threshold is replaced by the precise threshold.

7. The time synchronization method based on BeiDou-CCO fusion according to claim 1, characterized in that, It also includes a three-level progressive integrity check: before time synchronization, a snapshot of the power energy data is saved; after time synchronization, the power consumption difference ΔE is calculated within ΔT_total. If ΔE exceeds the preset threshold, the current period data is frozen; and the snapshot and deviation value are reported to the master station for verification. When the master station determines that there is an anomaly, it issues a data recovery command, and the STA slave node device overwrites the abnormal data with the snapshot.

8. A time synchronization system based on BeiDou-CCO fusion, operating using the time synchronization method described in any one of claims 1 to 7, characterized in that, The time synchronization system includes a BeiDou-CCO fusion module, a master station time server, and slave node devices for each STA; The BeiDou-CCO fusion module includes a BeiDou receiving unit and a dual-mode communication unit. The BeiDou receiving unit is used to receive the timing signal from the BeiDou satellite or the network time from the master time server, generate the network time base NTB, and broadcast time synchronization commands. The dual-mode communication unit includes an HPLC channel and an HRF channel. The master time server is used to provide the standard time base UTC as a redundant time source for the time synchronization signal; The STA slave node device is used to receive the synchronization message from the master time server, monitor the local clock deviation of the STA slave node device, and perform clock calibration. The BeiDou-CCO fusion module is connected to the STA slave node device through a dual-mode communication unit, and dynamically selects the communication link according to the channel quality to achieve distributed clock synchronization.

9. A time synchronization system based on BeiDou-CCO fusion according to claim 8, characterized in that, The Beidou-CCO fusion module adopts a four-layer PCB stack-up design. In order from top to bottom, the top layer is arranged with Beidou radio frequency circuit as Beidou receiving unit, the second layer is divided into an independent power supply area for signal and power isolation, the third layer is arranged with MCU and RTC crystal oscillator and used as control center, and the bottom layer is arranged with HPLC baseband and HRF transceiver module and used as dual-mode communication unit.

10. A time synchronization system based on BeiDou-CCO fusion according to claim 8, characterized in that, The master time server and each STA slave node device use the national cryptographic SM4-CBC encrypted time synchronization command. When the time synchronization command instructs the broadcast of the corresponding time synchronization message, a one-time session key KS is derived based on the station symmetric master key KM to perform two-way identity authentication and SM3 HMAC signature verification.

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