A communication method of a fine cutting system terminal access layer and a fine cutting system

Abstract

The application discloses a kind of communication methods of fine cutting system terminal access layer and fine cutting system, the terminal access layer includes access device and several control terminals, the access device and several control terminals are connected in the mode of fiber ring network;The control terminal receives and retransmits the communication message sent by access device and other control terminals by accessing a pair of interfaces of the same ring network;The access device receives the communication message sent by control terminal by accessing a pair of interfaces of the same ring network, and does not retransmit the communication message sent by control terminal.The any control terminal in the application has two paths to communicate with the access device, improves the reliability of communication between control terminal and access device, the interruptible load collected by the control terminal can still be used as the resource of power grid emergency control, thereby improving the reliability of accurate load shedding system, can give full play to the advantage of interruptible load, effectively reduce the cost of traditional emergency control, and improve control precision.

Description

Technical Field

[0001] This invention relates to precision load shedding technology, and more particularly to a communication method and precision shedding system for the terminal access layer of a precision load shedding system. Background Technology

[0002] When multiple DC lines feed into the power grid fail consecutively or experience DC blocking due to faults, a significant active power deficit in the receiving-end grid will occur, leading to a sharp drop in grid frequency. To avoid the substantial risks posed by frequency drop to grid operation, an emergency frequency coordination and stabilization control system is typically installed near the DC landing point. Based on the magnitude of the DC power loss, this system maintains power balance in the receiving-end grid and suppresses frequency drop by urgently increasing the transmission power of adjacent DC lines and disconnecting pumping units and corresponding loads from the receiving-end grid. However, traditional stabilization systems typically disconnect loads from 110kV, 35kV, and 10kV outgoing lines of substations. Once the stabilization system activates, it can cause widespread power outages in the receiving-end grid, resulting in significant social impact.

[0003] The precision load shedding system focuses on short-term interruptible 10kV and 380V load branch circuits within an enterprise. It centralizes dispersed interruptible loads for millisecond-level precise control, minimizing the impact on public electricity consumption. It can be used to address frequency stability issues in large power grids and meet the objective requirement of large-scale load shedding during simultaneous DC faults. The precision load shedding system is generally divided into three layers: the control master station layer, the control substation layer, and the end-user access layer. In this three-layer architecture, the control master station receives load shedding control commands from the upper-level stability control system, performs load allocation, and issues control tasks. The control substations collect the local shedding load data, upload it to the control master station, and execute the load shedding control commands. The control terminals collect user shedding load data and upload it in real time, while simultaneously receiving commands from the control substations and quickly shedding interruptible loads. At the end-user access layer, dedicated fiber optic access is typically used, with access devices configured at the nearest substation to the end user. The access device connects to the control substation via an E1 interface through the SDH transmission system, and connects to multiple control terminals via a dedicated optical fiber in a star topology. However, this connection method lacks reliability. If the optical fiber channel between a control terminal and the access device is disconnected, communication between them will be interrupted, and the interruptible loads collected by that control terminal cannot be used as resources for emergency power grid control. Summary of the Invention

[0004] Purpose of the invention: The present invention aims to provide a communication method and a precision cutting system for the terminal access layer of a precision cutting system that can improve the communication reliability between the control terminal and the access device.

[0005] Technical Solution: The present invention discloses a communication method for the terminal access layer of a precision cutting system. The terminal access layer includes an access device and several control terminals, which are connected in a fiber optic ring network. The control terminals receive and forward communication messages from the access device and other control terminals through a pair of interfaces connected to the same ring network. The access device receives communication messages from the control terminals through a pair of interfaces connected to the same ring network, but does not forward communication messages from the control terminals. The steps include the access device sending communication messages to the control terminals, the control terminals receiving communication messages, the control terminals sending communication messages to the access device, and the access device receiving communication messages.

[0006] Preferably, the access device is connected to the control substation via an SDH transmission system and has at least two fiber optic ring network interfaces, with each pair of two fiber optic ring network interfaces forming a pair for accessing the same ring network; the control terminal has two fiber optic ring network interfaces for accessing the same ring network; the access device and several control terminals are connected in a daisy-chain ring network manner via fiber optic ring network interfaces.

[0007] Preferably, the communication message structure includes a destination address, a source address, an Ethernet type, a path identifier, a device ID, a sequence number, application layer data, and a CRC checksum. The Ethernet type represents the ring network communication protocol between the access device and the control terminal. The path identifier is used to identify the interface from which the communication message is sent. The device ID is a unique ID identifier for both the access device and the control terminal. The sequence number is incremented by 1 for each message sent by the message publisher, used to identify whether it is a duplicate message. Specifically, twin messages sent by the access device or the control terminal at the same time through different interfaces have the same sequence number.

[0008] Preferably, the process of the access device sending communication messages to the control terminal includes the following steps:

[0009] (a1) The data sent by the control substation is judged and processed to generate application layer data sent by the access device to the control terminal; the application layer data frames in the data sent by the control substation are divided into command frames and ordinary data frames, wherein the command frames include load shedding level commands and load recovery reminder commands;

[0010] (a1.1) Process the data received from the control substation to determine whether it belongs to a command frame. If it does, proceed to step (a1.2); otherwise, proceed to step (a1.4).

[0011] (a1.2) Determine whether it is a load shedding command or a load restoration command. If it is a load shedding command, determine whether the positive and negative code verification of the load shedding command passes and proceed to step (a1.3); if it is a load restoration command, determine whether the positive and negative code verification of the load restoration command passes and proceed to step (a1.3); otherwise, proceed to step (a1.4).

[0012] (a1.3) If the positive and negative code verification of the load shedding command passes, set the load shedding command code sent to the control terminal and then proceed to step (a1.4); otherwise, proceed directly to step (a1.4). If the positive and negative code verification of the load restoration command passes, set the load restoration command code sent to the control terminal and then proceed to step (a1.4); otherwise, proceed directly to step (a1.4).

[0013] (a1.4) Set the status information of the control substation stabilization device to be sent to the control terminal, and generate the application layer data to be sent to the control terminal by the access device;

[0014] (a2) Add destination address, source address and Ethernet type fields to the application layer data generated in the previous step, and set the device ID and serial number to form a data packet to be sent, and then proceed to the next step;

[0015] (a3) Set different path identifiers for the data packets to be sent according to the different interfaces, form a communication message, and then copy it into the sending buffer of a pair of interfaces of the access device to proceed to the next step;

[0016] (a4) Send the communication messages in the transmit buffer of a pair of interfaces of the access device to the ring network at the same time.

[0017] Preferably, the control terminal receiving communication messages includes the following steps:

[0018] (b1) The control terminal receives communication messages through a pair of interfaces connected to the same ring network. If no communication message is received, the current data reception ends; otherwise, proceed to the next step.

[0019] (b2) Determine whether the “Ethernet type” field of the communication message conforms to the ring network communication protocol. If it does not conform, discard the communication message; otherwise, proceed to the next step.

[0020] (b3) Determine if the “path identifier” field of the communication message matches. If it does not match, discard the communication message; otherwise, proceed to the next step.

[0021] (b4) Determine whether the "destination address" field of the communication message meets the receiving conditions, that is, whether the destination MAC address is the same as the MAC address of this control terminal. If it does not meet the conditions, forward the communication message; otherwise, proceed to the next step.

[0022] (b5) Determine whether the “Device ID” of the communication message is the ID of the access device. If not, discard the communication message; otherwise, proceed to the next step.

[0023] (b6) Check the FIFO buffer for messages with the same sequence number but different path identifiers from the access device. If there are any, consider the two messages to be twin messages sent by the access device at the same time through different interfaces. Discard the communication message according to the first-come-first-served principle; otherwise, proceed to the next step.

[0024] (b7) Save the communication message in the first-in-first-out FIFO buffer of the control terminal, and then proceed to the next step;

[0025] (b8) Parse and process the application layer data of the communication message, including:

[0026] (b8.1) Obtain the status information of the control substation's stabilization device and display it through the human-machine interface, then proceed to the next step;

[0027] (b8.2) Determine whether it is a load shedding command or a load restoration command. If it is a load shedding command, determine whether the trip output pressure plate of the control terminal is in the engaged state and proceed to step (b8.3); if it is a load restoration command, the load restoration output of the control terminal is activated, the corresponding load line is restored to power supply, and proceed to step (b8.4).

[0028] (b8.3) If the trip output pressure plate of the control terminal is in the engaged state, the control terminal trip output disconnects the corresponding load line and proceeds to step (b8.4); otherwise, proceed directly to step (b8.4).

[0029] (b8.4) The received data has been processed and is waiting to receive data from the access device again.

[0030] Preferably, the method for the control terminal to forward communication messages is as follows: the communication message is received from one interface of the control terminal and forwarded from another interface.

[0031] Preferably, the process of the control terminal sending communication messages to the access device includes the following steps:

[0032] (c1) Generate application layer data sent by the control terminal to the access device, and proceed to the next step;

[0033] (c2) Add the destination address, source address, and Ethernet type fields required for Ethernet packets to the application layer data generated in the previous step, and set the sequence number and device ID to form a data packet to be sent, and then proceed to the next step;

[0034] (c3) Set different path identifiers for the data packets to be sent according to the different interfaces to form communication messages, and then copy them to the sending buffers of a pair of interfaces of the control terminal to proceed to the next step;

[0035] (c4) Send the communication messages in the transmit buffer of a pair of interfaces of the control terminal to the ring network at the same time.

[0036] Preferably, the access device receiving communication messages includes the following steps:

[0037] (d1) The access device receives communication messages through a pair of interfaces connected to the same ring network. If no communication message is received, the current data reception ends; otherwise, proceed to the next step.

[0038] (d2) Determine whether the "Ethernet type" field of the communication message conforms to the ring network communication protocol. If it does not conform, discard the communication message; otherwise, proceed to the next step.

[0039] (d3) Determine if the "path identifier" field of the communication message matches. If it does not match, discard the communication message; otherwise, proceed to the next step.

[0040] (d4) Determine whether the "destination address" field of the communication message meets the receiving conditions, that is, whether the destination MAC address is the same as the MAC address of the access device itself. If it does not meet the conditions, discard the communication message; otherwise, proceed to the next step.

[0041] (d5) Determine whether the “Device ID” of the communication message is the ID of any control terminal under the access device. If not, discard the communication message; otherwise, proceed to the next step.

[0042] (d6) Check the FIFO buffer for messages with the same sequence number but different path identifiers from the same control terminal. If there are any, consider the two messages to be twin messages sent by the same control terminal at the same time through different interfaces. Discard the communication message according to the first-come-first-served principle; otherwise, proceed to the next step.

[0043] (d7) Store the communication message in the first-in-first-out FIFO buffer of the access device, and then proceed to the next step;

[0044] (d8) Parse and process the application layer data of the communication message, integrate the data sent by all control terminals, and then use time division multiplexing to send the data of all control terminals to the control substation.

[0045] Preferably, the control terminal receives data from the ring network every T0 time interval and sends a ring network data packet every 2T0 time interval; the access device receives data from the ring network every T0 time interval and sends a ring network data packet every 2T0 time interval.

[0046] The precision cutting system described in this invention includes the communication method of the aforementioned terminal access layer.

[0047] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: The terminal access layer of the precise load shedding system adopts a ring network connection, and each control terminal has two paths to communicate with the access device. If a fiber optic channel in the ring network is disconnected, the control terminal can still communicate with the access device through the other path, which improves the reliability of communication between the control terminal and the access device. The interruptible loads collected by the control terminal can still be used as resources for emergency control of the power grid, thereby improving the reliability of the precise load shedding system. It can give full play to the advantages of interruptible loads, effectively reduce the cost of traditional emergency control, improve control accuracy, and reduce the social impact of large-scale power outages caused by the operation of conventional stability control systems due to large power grid disturbances such as multiple DC continuous commutation failures or blocking. Attached Figure Description

[0048] Figure 1 This is a diagram illustrating the architecture and network structure of the access device of the present invention, which connects to multiple control terminals in a ring network manner.

[0049] Figure 2 This is a schematic diagram illustrating the workflow of the access device of the present invention sending communication messages to the control terminal;

[0050] Figure 3 This is a schematic diagram illustrating the workflow of the control terminal receiving communication messages according to the present invention.

[0051] Figure 4 This is a schematic diagram illustrating the workflow of the control terminal sending communication messages to the access device according to the present invention.

[0052] Figure 5 This is a schematic diagram illustrating the workflow of the access device of the present invention in receiving communication messages. Detailed Implementation

[0053] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0054] like Figure 1As shown, the terminal access layer of the precise load shedding system of the present invention includes an access device and several control terminals. The access device and the control terminals are connected in a fiber optic ring network. The access device is connected to the site's SDH via two pairs of E1 interfaces through a 2M coaxial cable, and is connected to the dual-set stability control device of the control substation through the SDH transmission system. It has at least two fiber optic ring network interfaces, and every two fiber optic ring network interfaces form a pair for accessing the same ring network, denoted as interface A and interface B respectively. Each control terminal has two fiber optic ring network interfaces for accessing the same ring network, denoted as interface A and interface B respectively. The access device and the control terminals are connected in a daisy-chain ring network manner through the fiber optic ring network interfaces. Specifically, interface A of the access device is connected to interface B of the first control terminal, interface A of the first control terminal is connected to interface B of the second control terminal, and so on, until interface A of the Nth control terminal is connected to interface B of the access device, forming a ring network. In this embodiment, N is 8, that is, 8 control terminals are connected to the same ring network and communicate with the access device in a fiber optic ring network manner.

[0055] The communication method of the terminal access layer of a precise load shedding system according to the present invention includes: a control terminal receiving and forwarding communication messages from an access device and other control terminals through a pair of interfaces connected to the same ring network; the access device receiving communication messages from the control terminal through a pair of interfaces connected to the same ring network, but not forwarding the communication messages from the control terminal; the steps include: the access device sending communication messages to the control terminal; the control terminal receiving communication messages; the control terminal sending communication messages to the access device; and the access device receiving communication messages.

[0056] The control terminal receives data from the ring network every T0 time interval and sends a ring network data packet every 2T0 time intervals; the access device receives data from the ring network every T0 time interval and sends a ring network data packet every 2T0 time intervals. The value of T0 is 0.833 milliseconds, which can meet the requirements of the precise load shedding system.

[0057] The ring network data packets are communication messages, and their structure includes destination address, source address, Ethernet type, path identifier, device ID, sequence number, application layer data, and CRC checksum. The communication messages between the access device and the control terminal are based on the Ethernet data link layer and physical layer, but do not go through the TCP / IP protocol. By setting the ring network communication protocol between the access device and the control terminal, the "Ethernet type" field in the Ethernet message is defined as a fixed value, such as 0x892F. The path identifier is used to identify whether the communication message was sent from interface A or interface B. The "path identifier" field in the data packet sent from interface A is set to a fixed value, such as 0x0a; the "path identifier" field in the data packet sent from interface B is set to another fixed value, such as 0x0b. The device ID is a unique ID identifier for the access device and the control terminal. The sequence number is incremented by 1 for each message sent by the message publisher, used to identify whether it is a duplicate message. Twin messages sent by the access device or control terminal at the same time through different interfaces have the same sequence number, with a value range of 0 to 65535.

[0058] The structure of the communication message is shown in the table below:

[0059] Table 1 Communication Message Structure

[0060]

[0061] The access device receives instructions from the control substation device and sends them to the control terminal. Simultaneously, it aggregates control terminal data and uploads it to the control substation. The control terminal collects user load shelving capacity and sends it up in real time, while also receiving instructions from the control substation device. The application layer data frames received by the access device from the control substation device are divided into command frames and normal data frames. Normal data frames are 24 bytes each, containing information from 8 control terminals, as shown in Table 2. The downlink data frames sent by the access device to the control terminal are also divided into command frames and normal data frames, as shown in Table 3, each 24 bytes. The uplink data sent by the control terminal to the access device consists only of normal data frames, framed in 24-byte increments, including load shelving capacity, actual shelving capacity, anomaly information, outgoing line pressure plate, and version number. Frame number 0 sends the shelving capacity, and frame number 1 sends the actual shelving capacity; these two are sent alternately, as shown in Table 4. The access device integrates the information from the eight control terminals and sends only normal data frames to the control substation device, as shown in Table 5.

[0062] Table 2 Application layer data received by the access device from the control substation device

[0063]

[0064]

[0065] Table 3 Application layer data sent from the access device to the control terminal

[0066]

[0067]

[0068] Table 4 Application layer data sent from the control terminal to the access device

[0069]

[0070]

[0071] Table 5 Application layer data sent from the access device to the control substation device

[0072]

[0073]

[0074] Where k represents the nth control terminal in a frame, and its value ranges from 1 to 8.

[0075] like Figure 2 As shown, the process of the access device sending communication messages to the control terminal specifically includes the following steps:

[0076] (a1) Receive data from the two sets of devices in the control substation simultaneously through two E1 interfaces, make judgments and process the data, and generate application layer data sent by the access device to the control terminal.

[0077] The application layer data frames sent by the control substation are divided into command frames and ordinary data frames. The command frames include load shedding level commands and load restoration reminder commands.

[0078] (a1.1) First, process the data received from the control substation to determine whether it belongs to a command frame. If it does, proceed to step (a1.2); otherwise, proceed to step (a1.4).

[0079] (a1.2) Determine whether it is a load shedding command or a load restoration command. If it is a load shedding command, determine whether the positive and negative code verification of the load shedding command passes and proceed to step (a1.3); if it is a load restoration command, determine whether the positive and negative code verification of the load restoration command passes and proceed to step (a1.3); otherwise, proceed to step (a1.4).

[0080] (a1.3) If the positive and negative code verification of the load shedding command passes, set the load shedding command code sent to the control terminal and then proceed to step (a1.4); otherwise, proceed directly to step (a1.4). If the positive and negative code verification of the load restoration command passes, set the load restoration command code sent to the control terminal and then proceed to step (a1.4); otherwise, proceed directly to step (a1.4).

[0081] (a1.4) Set the control substation device status information such as the pressure plate status, synchronization start flag, and test status to be sent to the control terminal, and generate application layer data sent by the access device to the control terminal;

[0082] (a2) Add the destination MAC address, source MAC address, and Ethernet type fields required for Ethernet packets to the application layer data sent from the access device to the control terminal generated in the previous step, and set the device ID and serial number to form a data packet to be sent, and then proceed to the next step; wherein, the destination MAC address is set to the MAC address of the control terminal; the source MAC address is set to the MAC address of the access device; the Ethernet type is set to the ring network packet type defined by the ring network communication protocol between the access device and the control terminal; the device ID is set to the ID number of the access device; the serial number is incremented by 1, and the value range is 0 to 65535.

[0083] (a3) Set different path identifiers for the data packets to be sent according to the different interfaces, form a communication message, and then copy it into the sending buffer of a pair of interfaces of the access device to proceed to the next step;

[0084] (a4) Send the communication messages in the transmit buffer of a pair of interfaces of the access device to the ring network at the same time.

[0085] like Figure 3 As shown, the control terminal receiving communication messages specifically includes the following steps:

[0086] (b1) The control terminal receives communication messages through a pair of interfaces connected to the same ring network. If no communication message is received, the current data reception ends; otherwise, proceed to the next step.

[0087] (b2) Determine whether the “Ethernet type” field of the communication message conforms to the ring network communication protocol. If it does not conform, discard the communication message; otherwise, proceed to the next step.

[0088] (b3) Determine whether the “path identifier” field of the communication message matches. If it does not match, discard the communication message; otherwise, proceed to the next step. The criterion for determining whether the “path identifier” field of the communication message matches is that interface A can only receive data packets sent by interface B, and interface B can only receive data packets sent by interface A.

[0089] (b4) Determine whether the "destination address" field of the communication message meets the receiving conditions, that is, whether the destination MAC address is the same as the MAC address of the control terminal itself. If it does not meet the conditions, forward the communication message; otherwise, proceed to the next step. The method of the control terminal forwarding the communication message is as follows: if the communication message is received from interface A of the control terminal, it is forwarded from interface B; if it is received from interface B of the control terminal, it is forwarded from interface A.

[0090] (b5) Determine whether the “Device ID” of the communication message is the ID of the access device. If not, discard the communication message; otherwise, proceed to the next step.

[0091] (b6) Check the FIFO buffer for messages with the same sequence number but different path identifiers from the access device. If there are any, consider the two messages to be twin messages sent by the access device at the same time through different interfaces. Discard the communication message according to the first-come-first-served principle; otherwise, proceed to the next step.

[0092] (b7) Save the communication message in the first-in-first-out FIFO buffer of the control terminal, and then proceed to the next step; wherein, the first-in-first-out FIFO buffer of the control terminal can save the latest data packet sent by the access device within the T1 time period, which is used to compare with the currently received data packet to determine whether the twin message sent by the access device at the same time through different interfaces has been processed.

[0093] (b8) Parse and process the application layer data of the communication message, specifically including:

[0094] (b8.1) Obtain information such as the pressure plate status, synchronization start mark, and test status of the dual-set stabilization control devices, namely set A and set B, from the control substation, and display it through the human-machine interface before proceeding to the next step;

[0095] (b8.2) Determine if it is a load shedding command. If yes, proceed to step (b8.4); otherwise, proceed to the next step.

[0096] (b8.3) Determine if it is a load restoration command. If yes, proceed to step (b8.6); otherwise, proceed to step (b8.7).

[0097] (b8.4) Determine whether the trip output pressure plate of the control terminal is in the engaged state. If it is, proceed to step (b8.5); otherwise, proceed to step (b8.7).

[0098] (b8.5) Control the terminal trip output, disconnect the corresponding load line, and then proceed to step (b8.7);

[0099] (b8.6) Control the load restoration output of the terminal, restore power supply to the corresponding load line, and then proceed to step (b8.7);

[0100] (b8.7) The received data packet has been processed and is waiting to receive data from the access device again.

[0101] like Figure 4 As shown, the control terminal sending communication messages to the access device specifically includes the following steps:

[0102] (c1) Generate application layer data to be sent from the control terminal to the access device; the application layer data includes information such as the load capacity and actual load capacity of each layer, and fills the application layer data to be sent to the access device with information such as the software version, anomaly, and pressure plate status of the control terminal in the form of frame transmission, and then proceeds to the next step.

[0103] (c2) Add the destination address, source address, and Ethernet type fields required for Ethernet packets to the application layer data to be sent to the access device, and set the sequence number and device ID to form the data packet to be sent, and then proceed to the next step; wherein, the destination MAC address is set to the MAC address of the access device; the source MAC address is set to the MAC address of the control terminal; the Ethernet type is set to the ring network message type defined by the ring network communication protocol between the access device and the control terminal; the device ID is set to the ID number of the control terminal; the sequence number is incremented by 1, and the value range is 0 to 65535;

[0104] (c3) Set different path identifiers for the data packets to be sent according to the different interfaces to form communication messages, and then copy them to the sending buffers of a pair of interfaces of the control terminal to proceed to the next step;

[0105] (c4) Send the communication messages in the transmit buffer of a pair of interfaces of the control terminal to the ring network at the same time.

[0106] like Figure 5 As shown, the access device receiving communication messages specifically includes the following steps:

[0107] (d1) The access device receives communication messages through a pair of interfaces connected to the same ring network. If no communication message is received, the current data reception ends; otherwise, proceed to the next step.

[0108] (d2) Determine whether the "Ethernet type" field of the communication message conforms to the ring network communication protocol. If it does not conform, discard the communication message; otherwise, proceed to the next step.

[0109] (d3) Determine whether the “path identifier” field of the communication message matches. If it does not match, discard the communication message; otherwise, proceed to the next step. The criterion for determining whether the “path identifier” field of the communication message matches is that interface A can only receive data packets sent by interface B, and interface B can only receive data packets sent by interface A.

[0110] (d4) Determine whether the "destination address" field of the communication message meets the receiving conditions, that is, whether the destination MAC address is the same as the MAC address of the access device itself. If it does not meet the conditions, discard the communication message; otherwise, proceed to the next step.

[0111] (d5) Determine whether the “Device ID” of the communication message is the ID of any control terminal under the access device. If not, discard the communication message; otherwise, proceed to the next step.

[0112] (d6) Check the FIFO buffer for messages with the same sequence number but different path identifiers from the same control terminal. If there are any, consider the two messages to be twin messages sent by the same control terminal at the same time through different interfaces. Discard the communication message according to the first-come-first-served principle; otherwise, proceed to the next step.

[0113] (d7) The communication message is stored in the first-in-first-out FIFO buffer of the access device, and then proceeds to the next step; wherein the first-in-first-out FIFO buffer of the access device can store the latest data packet of any control terminal within the T2 time period, which is used to compare with the currently received data packet to determine whether the twin message sent by the same control terminal at the same time through different interfaces has been processed.

[0114] (d8) Parse and process the application layer data of the communication message, specifically including:

[0115] (d8.1) Obtain information such as the control terminal's switchable load, actual switchable load, abnormal status, pressure plate status, and software version from the communication message, and then proceed to the next step;

[0116] (d8.2) Integrate the data sent from the 8 control terminals by “frame number”, and then proceed to the next step;

[0117] (d8.3) Using time-division multiplexing, all control terminal data are sent to the A and B sets of control substations through the E1 interface.

Claims

1. A communication method for the terminal access layer of a precision cutting system, characterized in that, The terminal access layer includes an access device and several control terminals, which are connected in the form of an optical fiber ring network. The control terminals receive and forward communication messages from the access device and other control terminals through a pair of interfaces connected to the same ring network. The access device receives communication messages from the control terminals through a pair of interfaces connected to the same ring network, but does not forward communication messages from the control terminals. The steps include the access device sending a communication message to the control terminal, the control terminal receiving the communication message, the control terminal sending a communication message to the access device, and the access device receiving the communication message. The access device sends communication messages to the control terminal through the following steps: (a1) The data sent from the control substation is judged and processed to generate application layer data sent from the access device to the control terminal; the application layer data frames in the data sent from the control substation include command frames and ordinary data frames, wherein the command frames include load shedding level commands and load recovery reminder commands; (a1.1) Process the data received from the control substation and determine whether it belongs to a command frame. If it does, proceed to step (a1.2); otherwise, proceed to step (a1.4). (a1.2) Determine whether it is a load shedding command or a load restoration command. If it is a load shedding command, determine whether the positive and negative code verification of the load shedding command passes and proceed to step (a1.3); if it is a load restoration command, determine whether the positive and negative code verification of the load restoration command passes and proceed to step (a1.3); otherwise, proceed to step (a1.4). (a1.3) If the positive and negative code verification of the load shedding command passes, set the load shedding command code sent to the control terminal and then proceed to step (a1.4); otherwise, proceed directly to step (a1.4). If the positive and negative code verification of the load restoration command passes, set the load restoration command code sent to the control terminal and then proceed to step (a1.4); otherwise, proceed directly to step (a1.4). (a1.4) Set the status information of the control substation stabilization device to be sent to the control terminal, and generate the application layer data to be sent to the control terminal by the access device; (a2) Add destination address, source address and Ethernet type fields to the application layer data generated in the previous step, and set the device ID and serial number to form a data packet to be sent, and then proceed to the next step; (a3) Set different path identifiers for the data packets to be sent according to the different interfaces to form communication messages, and then copy them into the sending buffers of a pair of interfaces of the access device to proceed to the next step; (a4) Send the communication messages in the transmit buffer of a pair of interfaces of the access device to the ring network at the same time.

2. The communication method of the terminal access layer of the precision cutting system according to claim 1, characterized in that, The access device is connected to the control substation via an SDH transmission system and has at least two fiber optic ring network interfaces, with each pair of two fiber optic ring network interfaces forming a pair for accessing the same ring network; the control terminal has two fiber optic ring network interfaces for accessing the same ring network; the access device and several control terminals are connected in a daisy-chain ring network manner via fiber optic ring network interfaces.

3. The communication method of the terminal access layer of the precision cutting system according to claim 1, characterized in that, The communication message structure includes destination address, source address, Ethernet type, path identifier, device ID, sequence number, application layer data, and CRC checksum. The Ethernet type represents the ring network communication protocol between the access device and the control terminal. The path identifier is used to identify the interface from which the communication message is sent. The device ID is a unique ID identifier for the access device and the control terminal. Each time the publisher of the communication message sends a message, the sequence number is incremented by 1. The sequence number is used to identify whether it is a duplicate message. Specifically, twin messages sent by the access device or the control terminal at the same time through different interfaces have the same sequence number.

4. The communication method of the terminal access layer of the precision cutting system according to claim 3, characterized in that, The control terminal receives communication messages by including the following steps: (b1) The control terminal receives communication messages through a pair of interfaces connected to the same ring network. If no communication message is received, the current data reception ends; otherwise, proceed to the next step. (b2) Determine whether the "Ethernet type" field of the communication message conforms to the ring network communication protocol. If it does not conform, discard the communication message; otherwise, proceed to the next step. (b3) Determine if the "path identifier" field of the communication message matches. If it does not match, discard the communication message; otherwise, proceed to the next step. (b4) Determine whether the "destination address" field of the communication message meets the receiving conditions, that is, whether the destination MAC address is the same as the MAC address of this control terminal. If it does not meet the conditions, forward the communication message; otherwise, proceed to the next step. (b5) Determine whether the "Device ID" of the communication message is the ID of the access device. If not, discard the communication message; otherwise, proceed to the next step. (b6) Check the FIFO buffer for messages with the same sequence number but different path identifiers from the access device. If there are any, consider the two messages to be twin messages sent by the access device at the same time through different interfaces. Discard the communication message according to the first-come-first-served principle; otherwise, proceed to the next step. (b7) Store the communication message in the first-in-first-out FIFO buffer of the control terminal, and then proceed to the next step; (b8) Parse and process the application layer data of the communication message; including: (b8.1) Obtain the status information of the control substation's stabilization device and display it through the human-machine interface, then proceed to the next step; (b8.2) Determine whether it is a load shedding command or a load restoration command. If it is a load shedding command, determine whether the trip output pressure plate of the control terminal is in the engaged state and proceed to step (b8.3). If it is a load restoration command, the load restoration output of the control terminal is activated, the corresponding load line is restored to power supply, and proceed to step (b8.4). (b8.3) If the trip output pressure plate of the control terminal is in the engaged state, the control terminal trip output disconnects the corresponding load line and proceeds to step (b8.4); otherwise, proceed directly to step (b8.4). (b8.4) The received data has been processed and is waiting to receive data from the access device again.

5. The communication method of the terminal access layer of the precision cutting system according to claim 4, characterized in that, The method for the control terminal to forward communication messages is as follows: the communication message is received from one interface of the control terminal and forwarded from another interface.

6. The communication method of the terminal access layer of the precision cutting system according to claim 3, characterized in that, The control terminal sends communication messages to the access device through the following steps: (c1) Generate application layer data that the control terminal sends to the access device, and proceed to the next step; (c2) Add the destination address, source address, and Ethernet type fields required for Ethernet packets to the application layer data generated in the previous step, and set the sequence number and device ID to form a data packet to be sent, and then proceed to the next step; (c3) Set different path identifiers for the data packets to be sent according to the different interfaces to form communication messages, and then copy them to the sending buffers of a pair of interfaces of the control terminal to proceed to the next step; (c4) Send the communication messages in the transmit buffer of a pair of interfaces of the control terminal to the ring network at the same time.

7. The communication method of the terminal access layer of the precision cutting system according to claim 3, characterized in that, The access device receives communication messages by including the following steps: (d1) The access device receives communication messages through a pair of interfaces connected to the same ring network. If no communication message is received, the current data reception ends; otherwise, proceed to the next step. (d2) Determine whether the "Ethernet type" field of the communication message conforms to the ring network communication protocol. If it does not conform, discard the communication message; otherwise, proceed to the next step. (d3) Determine if the "path identifier" field of the communication message matches. If it does not match, discard the communication message; otherwise, proceed to the next step. (d4) Determine whether the "destination address" field of the communication message meets the receiving conditions, that is, whether the destination MAC address is the same as the MAC address of the access device itself. If it does not meet the conditions, discard the communication message; otherwise, proceed to the next step. (d5) Determine whether the "Device ID" of the communication message is the ID of any control terminal under the access device. If not, discard the communication message; otherwise, proceed to the next step. (d6) Check the FIFO buffer for messages with the same sequence number but different path identifiers from the same control terminal. If there are any, consider the two messages to be twin messages sent by the same control terminal at the same time through different interfaces. Discard the communication message according to the first-come-first-served principle; otherwise, proceed to the next step. (d7) Store the communication message in the first-in-first-out FIFO buffer of the access device, and then proceed to the next step; (d8) Parse and process the application layer data of the communication message, integrate the data sent by all control terminals, and then use time division multiplexing to send the data of all control terminals to the control substation.

8. The communication method of the terminal access layer of the precision cutting system according to any one of claims 1-7, characterized in that, The control terminal receives communication messages from the ring network every T0 time interval and sends a communication message frame every 2T0 time interval; the access device receives communication messages from the ring network every T0 time interval and sends a communication message frame every 2T0 time interval.

9. A precision cutting system, characterized in that, The terminal access layer of the precision cutting system includes an access device and several control terminals. The access device and the several control terminals are connected in the form of an optical fiber ring network to implement the communication method of the terminal access layer according to any one of claims 1-8.

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