High-proportion distributed photovoltaic power distribution network time synchronization method based on rapid flooding

Abstract

The invention discloses a high-proportion distributed photovoltaic power distribution network time synchronization method based on rapid flooding. The method comprises the following steps: 1) determining a global time reference root node in a high-proportion distributed photovoltaic power distribution network scene; 2) dividing the power distribution network containing the high-proportion distributed photovoltaic into a plurality of areas, and determining a main node of each area; 3) detecting whether a time synchronization abnormal area exists, if so, entering step 4), and otherwise, finishing time synchronization; and 4) performing time synchronization recovery by using a flooding algorithm, and returning to the step 3). According to the method, the time synchronization recovery efficiency and reliability of the high-proportion distributed photovoltaic power distribution network can be improved, the operation and maintenance cost can be effectively reduced, and the defense capability of the system to network attacks and faults is improved.

Description

Technical Field

[0001] The invention relates to the field of time synchronization of distribution networks, and in particular to a time synchronization method for a high-proportion distributed photovoltaic distribution network based on rapid flooding. Background Art

[0002] In modern power systems, time synchronization technology plays a key role in ensuring efficient and stable operation of the system. This technology is widely used in data acquisition, fault analysis, system control and other aspects. Through precise time synchronization, the operation of various devices can be coordinated to ensure the consistency and real-time nature of information. However, with the increase in system risks caused by cyber attacks, the existing distribution network time synchronization methods face severe challenges. Especially when a high proportion of distributed photovoltaics are connected to the distribution network, time synchronization attacks will seriously interfere with the distributed photovoltaics' tracking of upper-level dispatching instructions and precise control of cluster output, destroying the photovoltaic system's ability to coordinate the distribution network, and thus affecting the operation of the entire power grid.

[0003] Although traditional time synchronization methods such as GPS and PTP can meet most requirements in terms of accuracy, these methods face significant challenges in distribution network application scenarios as system risks caused by cyber attacks increase. For example, GPS equipment is expensive, and signals are easily blocked in indoor or underground facilities; PTP usually relies on fixed hardware equipment and topology, and configuration and maintenance are relatively complex. With the large-scale distributed photovoltaic access to the distribution network, in the event of a cyber attack or system failure, the existing time synchronization methods are difficult to simultaneously meet the requirements of fast convergence and high synchronization accuracy, and cannot effectively achieve rapid recovery of the system.

[0004] As the intelligent level of distribution networks and the penetration rate of distributed photovoltaics continue to increase, the cyber attack threats and system failure risks they face are gradually increasing. Traditional time synchronization technology faces the following challenges when recovering from system anomalies:

[0005] 1. Information propagation delay and error accumulation: In large-scale distribution networks, information propagation needs to pass through multiple nodes. The processing and forwarding of each node will cause delay and error accumulation, thus affecting the synchronization accuracy of the overall network.

[0006] 2. Slow global synchronization convergence speed: Under the premise of meeting the accuracy requirements, the existing synchronization mechanisms mostly converge slowly, making it difficult for the distribution network to quickly restore normal system control and scheduling, which is not conducive to the safe and stable operation of the distribution network system.

[0007] 3. Network dependency: Existing synchronization methods are highly dependent on the structure and stability of the network. When the network topology changes, the synchronization mechanism needs to be reconfigured, which is more complicated in a dynamically changing distribution network system. Summary of the Invention

[0008] The object of the present invention is to provide a high - proportion distributed photovoltaic distribution network time synchronization method based on fast flooding, including the following steps:

[0009] 1) Determine the global time reference root node in the high - proportion distributed photovoltaic distribution network scenario;

[0010] 2) Divide the distribution network with high - proportion distributed photovoltaics into multiple regions, and determine the master node of each region;

[0011] 3) Detect whether there is a time synchronization abnormal region. If so, go to step 4); otherwise, complete time synchronization;

[0012] 4) Use the flooding algorithm to perform time synchronization recovery, and return to step 3).

[0013] Furthermore, the global time reference root node is the main substation or the dispatching center node.

[0014] Furthermore, the main substation or the dispatching center node is time - synchronized through GPS.

[0015] Furthermore, in step 2), the distribution network is divided into multiple regions according to the different functions of the node devices.

[0016] Furthermore, the master node of each region is the node closest to the global time reference root node within the region.

[0017] Furthermore, in step 4), the steps of using the flooding algorithm to perform time synchronization recovery include:

[0018] 4.1) Synchronize the master node of the time synchronization abnormal region with the global time reference root node through the original time synchronization protocol;

[0019] 4.2) The master node of the time synchronization abnormal region initiates flooding and broadcasts periodically according to a preset time, and sequentially transmits the reference time information to other nodes within the time synchronization abnormal region;

[0020] 4.3) Each node adjusts its local clock and frequency parameters after receiving the message.

[0021] Furthermore, in step 4.2), the master node of the time synchronization abnormal region serves as the starting reference node R for flooding, only broadcasts the time information packet, and does not process the received time information packet;

[0022] The time information packet broadcast by the master node includes the hardware clock H R , the logical clock L R , the logical clock rate multiplier and the node identifier ID R ;

[0023] Among them, the node identification ID R is used to identify multiple broadcast messages.

[0024] Furthermore, in step 4.3), the steps for each node to adjust the local clock and frequency parameters after receiving the message are as follows: by multiplying the logical clock rate multiplier and the clock offset estimate to calibrate the local logical clock L i (t), to obtain the calibrated logical time, so as to realize the synchronization of the logical time and the master node time;

[0025] The calibrated logical clock L i (t + τ) is as follows:

[0026]

[0027] In the formula, H i (t + τ), H i (t) are hardware clocks.

[0028] Furthermore, the logical clock rate multiplier is as follows:

[0029]

[0030] In the formula, is the statistical average of the change amount of the time deviation between node v j and the reference node between two synchronizations, and

[0031] is the time interval between two synchronizations; The clock offset estimate

[0032]

[0033] In the formula, is the statistical average of the fixed transmission delay, L i [n] and L j [n] are the logical times of node i and node j after the nth message transmits time information.

[0034] Furthermore, in step 3), the time synchronization abnormal area refers to the area where the time difference between at least one node and the global time reference root node is greater than the preset value.

[0035] The technical effect of the present invention is beyond doubt. The beneficial effects of the present invention are as follows:

[0036] 1) Significant reduction in error accumulation and propagation delay: Through the improved flooding time synchronization algorithm, the present invention broadcasts and updates time information within a local area, and performs compensation calculations based on maximum likelihood estimation, reducing the impact of propagation delay and error accumulation caused by long-distance and multi-node transmissions. Each node can promptly correct its own clock and frequency according to the latest received time data, thereby significantly improving the synchronization accuracy of the entire network.

[0037] 2) Enhancement of synchronization convergence speed: The flooding technique adopted in this method ensures that time information can spread rapidly in the network, greatly improving the synchronization convergence speed. Compared with traditional time synchronization methods, the present invention reduces the time for waiting for feedback from all nodes during the synchronization process, enabling the entire distribution network and distributed photovoltaic system to complete time synchronization in a shorter time, and significantly enhancing the speed of the system's return to normal operation after a fault.

[0038] 3) Independence from a fixed topology structure: The time synchronization method of the present invention does not depend on a fixed network physical structure and can achieve precise and efficient time synchronization even when the network topology changes, which enables it to adapt to the dynamically changing topology of the distribution network.

[0039] 4) Simplification of the operation process: Compared with traditional PTP or GPS synchronization devices, the present invention simplifies the configuration and maintenance requirements of synchronization devices. Through the time synchronization algorithm and error compensation calculation mechanism defined in the method, users can avoid complex manual settings, thereby reducing the operation complexity and technical threshold.

[0040] The present invention can not only improve the time synchronization recovery efficiency and reliability of a high-proportion distributed photovoltaic distribution network, but also effectively reduce the operation and maintenance costs and enhance the system's defense capabilities against network attacks and faults. These characteristics and advantages enable the present invention to be applied to the actual scenarios of new power systems, ensuring the safe, reliable, and economic operation of the distribution network. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a schematic flowchart of the implementation steps of the present invention

[0042] Figure 2 is a schematic structural diagram of the present invention applied to a high-proportion distributed photovoltaic distribution network scenario;

[0043] Figure 3 is a schematic diagram of the principle of the time synchronization algorithm of the present invention;

[0044] Figure 4 is an effect diagram of the time synchronization algorithm of the present invention for the distributed photovoltaic to execute the power output scheduling instruction of the distribution network. DETAILED DESCRIPTION OF THE INVENTION

[0045] The present invention will be further described below in conjunction with embodiments, but it should not be understood that the above-mentioned subject scope of the present invention is limited to the following embodiments. Without departing from the above-mentioned technical idea of the present invention, various substitutions and changes should be included within the protection scope of the present invention according to the common general knowledge and customary means in the art.

[0046] Embodiment 1:

[0047] Refer to Figures 1 to 4 , a high-proportion distributed photovoltaic distribution network time synchronization method based on fast flooding, including the following steps:

[0048] 1) Determine the global time reference root node in the high-proportion distributed photovoltaic distribution network scenario;

[0049] 2) Divide the distribution network with high-proportion distributed photovoltaic into multiple regions, and determine the master node of each region;

[0050] 3) Detect whether there is a time synchronization abnormal region. If so, go to step 4), otherwise, complete the time synchronization;

[0051] 4) Use the flooding algorithm to perform time synchronization recovery, and return to step 3).

[0052] The global time reference root node is the main substation or the dispatching center node.

[0053] The main substation or the dispatching center node is synchronized by GPS time service.

[0054] In step 2), the distribution network is divided into multiple regions according to the different functions of the node devices.

[0055] The master node of each region is the node closest to the global time reference root node within the region.

[0056] In step 4), the steps of using the flooding algorithm to perform time synchronization recovery include:

[0057] 4.1) Synchronize the master node of the time synchronization abnormal region with the global time reference root node through the original time synchronization protocol;

[0058] 4.2) The master node of the time synchronization abnormal region initiates flooding and broadcasts periodically according to a preset time, and sequentially transmits the reference time information to other nodes within the time synchronization abnormal region;

[0059] 4.3) Each node adjusts the local clock and frequency parameters after receiving the message.

[0060] In step 4.2), the master node of the time synchronization abnormal region serves as the starting reference node R of the flooding, only broadcasts the time information packet, and does not process the received time information packet;

[0061] The time information packet broadcast by the master node includes the hardware clock H R , the logical clock L R , the logical clock rate multiplier and the node identifier ID R ;

[0062] Among them, the node identifier ID R is used to identify multiple broadcast messages.

[0063] In step 4.3), the steps for each node to adjust the local clock and frequency parameters after receiving the message are as follows: through the logical clock rate multiplier and the clock offset estimation calibrate the local logical clock L i (t) to obtain the calibrated logical time, thereby realizing the synchronization of the logical time with the master node time;

[0064] The calibrated logical clock L i (t + τ) is as follows:

[0065]

[0066] In the formula, H i (t + τ), H i (t) are the hardware clocks.

[0067] The logical clock rate multiplier is as follows:

[0068]

[0069] In the formula, is the statistical average of the change amount of the time deviation between node v j and the reference node between two synchronizations, and

[0070] is the time interval between two synchronizations; The clock offset estimation

[0071]

[0072] In the formula, is the statistical average of the fixed transmission delay, L i [n] and L j [n] are the logical times of node i and node j after the nth message transmits the time information.

[0073] In step 3), the time synchronization abnormal area refers to the area where the time difference between at least one node and the global time reference root node is greater than the preset value.

[0074] Embodiment 2:

[0075] A high - proportion distributed photovoltaic distribution network time synchronization method based on fast flooding, comprising the following steps:

[0076] 1) Determine the global time reference root node in the high - proportion distributed photovoltaic distribution network scenario;

[0077] 2) Divide the distribution network with high - proportion distributed photovoltaic into multiple regions, and determine the master node of each region;

[0078] 3) Detect whether there is a time synchronization abnormal region. If so, go to step 4); otherwise, complete time synchronization;

[0079] 4) Use the flooding algorithm to perform time synchronization recovery, and return to step 3).

[0080] Example 3:

[0081] A high - proportion distributed photovoltaic distribution network time synchronization method based on fast flooding, the technical content is the same as that of Example 2. Further, the global time reference root node is the main substation or the dispatching center node.

[0082] Example 4:

[0083] A high - proportion distributed photovoltaic distribution network time synchronization method based on fast flooding, the technical content is the same as any one of Examples 2 - 3. Further, the main substation or the dispatching center node is synchronized by GPS time service.

[0084] Example 5:

[0085] A high - proportion distributed photovoltaic distribution network time synchronization method based on fast flooding, the technical content is the same as any one of Examples 2 - 4. Further, in step 2), the distribution network is divided into multiple regions according to the different functions of the node devices.

[0086] Example 6:

[0087] A high - proportion distributed photovoltaic distribution network time synchronization method based on fast flooding, the technical content is the same as any one of Examples 2 - 5. Further, the master node of each region is the node closest to the global time reference root node in the region.

[0088] Example 7:

[0089] A high - proportion distributed photovoltaic distribution network time synchronization method based on fast flooding, the technical content is the same as any one of Examples 2 - 6. Further, in step 4), the steps of using the flooding algorithm to perform time synchronization recovery include:

[0090] 4.1) Synchronize the master node of the time synchronization abnormal region with the global time reference root node through the original time synchronization protocol;

[0091] 4.2) The master node in the time synchronization abnormal area initiates flooding and broadcasts periodically according to a preset time, and sequentially transmits the reference time information to other nodes in the time synchronization abnormal area;

[0092] 4.3) After receiving the message, each node adjusts its local clock and frequency parameters.

[0093] Embodiment 8:

[0094] A time synchronization method for a high-proportion distributed photovoltaic distribution network based on fast flooding, the technical content is the same as any one of Embodiments 2-7. Further, in step 4.2), the master node in the time synchronization abnormal area serves as the starting reference node R for flooding, and only broadcasts time information packets without processing the received time information packets;

[0095] The time information packet broadcast by the master node includes the hardware clock H R , the logical clock L R , the logical clock rate multiplier and the node identifier ID R ;

[0096] Among them, the node identifier ID R is used to identify multiple broadcast messages.

[0097] Embodiment 9:

[0098] A time synchronization method for a high-proportion distributed photovoltaic distribution network based on fast flooding, the technical content is the same as any one of Embodiments 2-8. Further, in step 4.3), the steps for each node to adjust its local clock and frequency parameters after receiving the message are: calibrate the local logical clock L and the clock offset estimation (t), to obtain the calibrated logical time, so as to realize the synchronization of the logical time with the master node time; i (t), to obtain the calibrated logical time, so as to realize the synchronization of the logical time with the master node time;

[0099] The calibrated logical clock L i (t + τ) is as follows:

[0100]

[0101] In the formula, H i (t + τ), H i (t) are hardware clocks.

[0102] Embodiment 10:

[0103] A time synchronization method for a high-proportion distributed photovoltaic distribution network based on fast flooding, the technical content is the same as any one of Embodiments 2-9. Further, the logical clock rate multiplier As shown below:

[0104]

[0105] Wherein, is the statistical average of the change in the time deviation between node v j and the reference node during two synchronizations, and is the time interval between two synchronizations;

[0106] Clock offset estimation is as shown below:

[0107]

[0108] Wherein, is the statistical average of the fixed transmission delay, and L i [n] and L j [n] are the logical times of node i and node j after the nth message transmits time information.

[0109] Example 11:

[0110] A high-proportion distributed photovoltaic distribution network time synchronization method based on fast flooding, the technical content is the same as any one of Examples 2-10. Further, in step 3), the time synchronization abnormal area refers to an area where the time difference between at least one node and the global time reference root node is greater than a preset value.

[0111] Example 12:

[0112] A high-proportion distributed photovoltaic distribution network time synchronization method based on fast flooding, the steps include:

[0113] Step 101, determine the root node of the global time reference. In the high-proportion distributed photovoltaic distribution network scenario, a key node such as a main substation or a dispatching center can be selected as the root node, and it is accurately time-synchronized through GPS or the like, and then used as the global time reference.

[0114] Step 102, divide the distribution network with a high proportion of distributed photovoltaics into multiple areas. According to the different functions of each node device such as power generation, control, power consumption, etc., the distribution network is divided into multiple areas, and the area closest to the root node is used as the main node of the area respectively.

[0115] Step 103, detect and locate the synchronization abnormal area. The system detects whether there is a time synchronization abnormality in each area node of the distribution network. If there is an abnormality, its location area is located to facilitate starting the flooding recovery algorithm.

[0116] Step 104: Start the flooding algorithm for synchronization recovery. The master node in the abnormal area initiates flooding and performs periodic broadcasts at preset time intervals to sequentially transmit the reference time information to the nodes within the area. Each node adjusts local clock and frequency and other parameters after receiving the message.

[0117] Step 105: Iterative adjustment and system synchronization status verification. Iteratively adjust the algorithm parameters, and verify the system status after multiple rounds of time synchronization. If the preset accuracy requirement is met, the system synchronization is completed; otherwise, continue iterative adjustment.

[0118] As Figure 2 and Figure 3 shown, they are respectively the structural diagram of the high-proportion distributed photovoltaic distribution network scenario corresponding to the present invention and the schematic diagram of the synchronization recovery algorithm. The process of realizing time synchronization recovery in the distribution network scenario is as follows:

[0119] 1. In the high-proportion distributed photovoltaic distribution network scenario corresponding to the present invention, only the master node in the synchronization abnormal area synchronizes with the global root node through the original time synchronization protocol. The master node serves as the starting reference node R for flooding, and only broadcasts time information packets without processing the received time information packets. The reference node R broadcasts regularly, distributes the reference time information packets to neighbors. Once the broadcast task is triggered, the reference node will quickly broadcast N data packets within a very short time interval (N is the total number of nodes other than the reference node in this area). The basic information of the broadcast message includes: hardware clock H R , logical clock L R , logical clock rate multiplier and node identifier ID R .

[0120] 2. For non-reference node v i in the area, it synchronizes to the reference node by calibrating the local logical clock Li(t) through the logical clock rate multiplier and clock offset estimation . v j is a neighbor node of vi and is closer to the reference node.

[0121] 3. The identifier ID is used to identify multiple broadcast messages for rapid dissemination. The reference node identifier ID R is initialized to 1 and incremented by 1 after a broadcast task is completed. The messages of the current broadcast task are embedded in the same ID R .

[0122] 4. Once v i processes the received time information packet, a compensation task will be triggered. The parameters and are used to compensate the local logical clock. After a very short random delay, node vi The forwarding time information will be sent and the clock parameters will be shared. The basic time information of the broadcast message is also converted to v i corresponding hardware clock H i and logical clock L i and the logical clock rate multiplier and node identifier ID i .

[0123] 5. The time compensation during synchronization includes clock offset and frequency offset, where the relative clock offset is calculated based on the maximum likelihood estimation:

[0124]

[0125] In the formula, is the statistical average value of the fixed transmission delay, and L i [n] and L j [n] are the logical times of node i and node j after the nth message transfers the time information.

[0126] When calculating the relative frequency offset compensation, the logical clock rate multiplier of the non-reference node is initialized to 1 and shared with neighbors as part of the time synchronization information packet. To make the logical clock of the non-reference node v i run at the same frequency as the reference node, the maximum likelihood estimation is used, and the result of multiplying by is used to update the logical clock rate multiplier of v i where is calculated by the following formula:

[0127]

[0128] In the formula, is the statistical average value of the change in the time deviation between node v j and the reference node between two synchronizations, and is the time interval between two synchronizations.

[0129] After calculating and and compensating the local logical clock, the logical time is updated to:

[0130]

[0131] 6. After several rounds of synchronization, the algorithm tends to converge. After iteratively adjusting the parameters until the accuracy requirement is met, all nodes in this area reach synchronization with the master node R, thus unifying to the global reference time and achieving the synchronization recovery of the system.

[0132] As Figure 4 shown, after a time synchronization attack on a distribution network with a high proportion of distributed photovoltaics, the distributed photovoltaic clusters cannot effectively track the output instructions issued by the dispatching center, which will lead to power surplus or shortage and affect the balance between the power generation and load of the system. However, the present invention can quickly restore the time synchronization of each node of the system and meet the specified accuracy requirements, so as to effectively track the output instructions and ensure the stable operation of the system.

Claims

1. A time synchronization method for a high-proportion distributed photovoltaic distribution network based on rapid flooding, characterized in that: The following steps are involved: 1) Determine the global time reference root node in the scenario of high-proportion distributed photovoltaic distribution network; 2) Divide the distribution network with a high proportion of distributed photovoltaics into multiple areas and determine the master node of each area; 3) Check whether there is a time synchronization abnormal area, if so, proceed to step 4), otherwise, complete time synchronization; 4) Use the flooding algorithm to restore time synchronization and return to step 3).

2. According to claim 1, a time synchronization method for a high-proportion distributed photovoltaic distribution network based on rapid flooding is characterized in that: The global time reference root node is a main substation or a dispatch center node.

3. A time synchronization method for a high-proportion distributed photovoltaic distribution network based on rapid flooding according to claim 2, characterized in that: The main substation or dispatch center node uses GPS timing.

4. According to claim 1, a time synchronization method for a high-proportion distributed photovoltaic distribution network based on rapid flooding is characterized in that: In step 2), the distribution network is divided into multiple areas according to the different functions of the node devices.

5. The time synchronization method for a high-proportion distributed photovoltaic distribution network based on rapid flooding according to claim 1 is characterized in that: The master node of each region is the node in the region that is closest to the global time reference root node.

6. A time synchronization method for a high-proportion distributed photovoltaic distribution network based on rapid flooding according to claim 1, characterized in that: In step 4), the steps of using the flooding algorithm to restore time synchronization include: 4.1) Synchronize the master node in the time synchronization abnormal area with the global time reference root node through the original time synchronization protocol; 4.2) The master node in the time synchronization abnormality area initiates flooding and broadcasts periodically according to the preset time, and transmits the reference time information to other nodes in the time synchronization abnormality area in turn; 4.3) Each node adjusts the local clock and frequency parameters after receiving the message.

7. A time synchronization method for a high-proportion distributed photovoltaic distribution network based on rapid flooding according to claim 6, characterized in that: In step 4.2), the master node in the time synchronization abnormal area serves as the starting reference node R of flooding, only broadcasts the time information packet, and does not process the received time information packet; The time information packet broadcast by the master node includes the hardware clock H R , logical clock L R , logical clock rate multiplier and node ID R ; Among them, the node ID R Used to identify multiple broadcast messages.

8. A time synchronization method for a high-proportion distributed photovoltaic distribution network based on rapid flooding according to claim 6, characterized in that: In step 4.3), each node adjusts the local clock and frequency parameters after receiving the message by: and clock offset estimation Calibrate the local logical clock L i (t), obtain the calibrated logical time, so as to achieve synchronization between the logical time and the master node time; Calibrated logical clock L i (t+τ) is shown below: In the formula, H i (t+τ), H i (t) is the hardware clock.

9. A time synchronization method for a high-proportion distributed photovoltaic distribution network based on rapid flooding according to claim 8, characterized in that: Logical clock rate multiplier As shown below: In the formula, is node v j The statistical average of the time deviation change between two synchronizations with the reference node, is the time interval between two synchronizations; Clock skew estimation As shown below: In the formula, is the statistical average of the fixed transmission delay, L i [n] and L j [n] is the logical time of nodes i and j after the nth message transmits the time information.

10. The time synchronization method for a high-proportion distributed photovoltaic distribution network based on rapid flooding according to claim 1, characterized in that: In step 3), the time synchronization abnormal area refers to an area where the time difference between at least one node and the global time reference root node is greater than a preset value.

Images