A redundant communication system and method of a sub-module networking unit in an MMC and a modular multilevel converter

Abstract

The application relates to a redundant communication system and a communication method of a sub-module networking unit in an MMC (modular multilevel converter) and the modular multilevel converter, and belongs to the technical field of the modular multilevel converter. The networking unit comprises a plurality of mutually communicating sub-modules, all the sub-modules in the networking unit are divided into a plurality of sub-module groups, and the sub-modules in each sub-module group communicate with at least two other sub-modules in the group. The networking unit further comprises a splitter for receiving and transmitting communication information between a valve control and the sub-modules. A splitter is matched for each sub-module group, one side of the splitter is connected to at least two key sub-modules in the group, and the other side is connected to the output end of a valve control interface unit. When the key sub-module connected to the splitter fails, another key sub-module connected to the splitter receives and transmits the communication information, multiple redundancies between the valve control system and the networking unit are realized, the communication reliability is improved, and the networking system is prevented from being paralyzed due to damage of the key sub-modules in the networking topology.

Description

Technical Field

[0001] This invention relates to a redundant communication system and communication method for submodule networking units in MMC, and a modular multilevel converter, belonging to the technical field of modular multilevel converters. Background Technology

[0002] Flexible DC transmission technology has technological advantages in AC system interconnection, large-scale renewable energy grid connection, isolated power supply, and urban distribution network capacity expansion and upgrading, and is currently a leading technology in the power transmission and distribution field. Accelerating the construction of a clean, low-carbon, safe, and efficient energy system requires the support of flexible AC / DC transmission technology, as the grid needs to be more user-friendly and flexible for various distributed energy sources to access the grid.

[0003] Flexible DC transmission refers to high-voltage direct current (HVDC) transmission based on voltage source converters (VSCs), and is a new type of DC transmission method following AC transmission and conventional DC transmission. Structurally, it is similar to HVDC transmission. The main equipment of flexible DC transmission includes flexible DC converter valves, high-voltage DC circuit breakers, converter transformers, flexible DC transmission control and protection systems, and DC reactors / smoothing reactors. The converter station is the most important part of the flexible DC transmission system.

[0004] Modular multilevel converters (MMCs) are the core equipment for flexible DC transmission. The emergence of MMC technology has greatly promoted the development of flexible DC transmission technology. Currently, the MMCs in operational projects have reached the 1000 MVA / ±320 kV level, and MMC-HVDC projects of 3000 MVA / ±500 kV and 5000 MVA / ±800 kV are under construction. However, with the continuous improvement of MMC voltage and capacity levels and the continuous expansion of application fields, MMCs and their DC transmission technology are also facing various new challenges. As the number of levels continues to increase, the number of bridge arm power modules is also increasing. Taking the 840 MVA / ±500 kV converter station A as an example, its single bridge arm power modules reach 540, resulting in a large number of fiber optic connections in the power module interface chassis and converter valve system, leading to high engineering costs and implementation difficulties, and urgently requiring low-cost solutions.

[0005] Chinese invention patent application CN119135254A discloses a communication system and method between a flexible DC converter valve submodule and a valve control system. In this system, the valve base interface unit (VBI) and the submodule are connected via optical splitters. The two optical splitters are fully dualized, connecting to the VBI unit upwards and to the odd-numbered and even-numbered converter valve submodules downwards, respectively. When the valve control system (VCP) sends control commands to the VBI, the VBI and optical splitters communicate via two-way triggering to distribute the control commands to each submodule. The submodules then return status information to the two VBI units via high-level communication. As can be seen, although the patent document (CN119135254A) designs two splitters connected between the valve base interface and each sub-module, these two splitters connect multiple sub-modules regardless of whether they connect to odd-numbered or even-numbered sub-modules. Furthermore, the actual data communication speed between each sub-module is in the microsecond range. Connecting multiple sub-modules to one splitter actually increases the operational burden on the splitter. In addition, when each sub-module returns status information to the two sets of VBIs, point-to-point communication occurs between the sub-module and the valve controller. That is, these two splitters are "one-way communication" splitters. The valve controller needs to continuously receive status signals from several sub-modules, which can easily lead to data redundancy. Summary of the Invention

[0006] The purpose of this invention is to provide a redundant communication system and communication method for submodule networking units in MMC, as well as a modular multilevel converter, to solve the problem of communication link interruption between the valve control system and the bridge arm power module caused by the failure of a critical power module in the prior art.

[0007] To address the aforementioned issues, this invention proposes a redundant communication system for a submodule networking unit in an MMC. The networking unit comprises several mutually communicating submodules. All submodules within the networking unit are divided into several submodule groups. Each submodule group communicates with at least two other submodules within that group. The networking unit also includes a splitter for transmitting and receiving communication information between the valve control interface unit and the submodules. Each submodule group is matched with a splitter, with one side of the splitter connected to at least two key submodules within the group and the other side connected to the output of the valve control interface unit. When a critical submodule connected to the optical splitter fails, the communication information is transmitted and received through another critical submodule connected to the optical splitter.

[0008] In one possible implementation, one side of the optical splitter is connected to at least two key sub-modules within the group via at least two sets of transceiver fibers; the other side is connected to the output of the valve control interface unit via at least one set of transceiver fibers.

[0009] In one possible implementation, the transceiver fiber used to connect one side of the optical splitter to the key submodule is a short optical fiber; the transceiver fiber used to connect the other side of the optical splitter to the output of the valve control interface unit is a long optical fiber.

[0010] In one possible implementation, when the networking unit includes n sub-modules, the sub-modules are arranged in two rows in equal numbers, and the sub-modules of the same sequence in the two rows are paired up to form a U-shaped physical arrangement of the network, wherein adjacent modules communicate with each other. Submodule 1 and its adjacent submodule 2 are used as key submodules for connecting the first optical splitter; Submodule n / 3 and its adjacent submodules (n / 3+1) are used as key submodules for connecting the second beam splitter; Submodule 2n / 3 and its adjacent submodule (2n / 3+1) are used as key submodules for connecting the third beam splitter; Submodule n and its adjacent submodules (n-1) are used as key submodules for connecting the fourth beam splitter.

[0011] In one possible implementation, the key submodules in each submodule group are physically adjacent submodules.

[0012] In one possible implementation, when a splitter in the networking unit fails, other non-faulty splitters are used to send and receive communication information in the submodules of the submodule group corresponding to the faulty splitter.

[0013] To address the aforementioned technical problems, this invention proposes a communication method for a submodule networking unit in an MMC. The networking unit comprises several mutually communicating submodules. All submodules in the networking unit are divided into several submodule groups, and each submodule in a submodule group communicates with at least two other submodules within that group. The networking unit also includes a splitter for transmitting and receiving communication information between the valve control interface unit and the submodules. A splitter is matched to each submodule group, with one side of the splitter connected to at least two key submodules within the group, and the other side connected to the output of the valve control interface unit. The method includes: When a critical submodule in the networking unit fails, another critical submodule on the optical splitter connected to the failed critical submodule is selected to send and receive communication information. The failed critical submodule and the selected critical submodule are connected to the same optical splitter.

[0014] In one possible implementation, during downlink communication, each submodule is assigned its own execution instruction time; after all submodules receive the instruction information, all submodules are controlled to perform on / off operations according to their respective corresponding execution instruction times.

[0015] In one possible implementation, state information is communicated according to the time-division multiplexing principle during uplink communication.

[0016] In one possible implementation, when a splitter in the networking unit fails, other non-faulty splitters are used to send and receive communication information in the submodules of the submodule group corresponding to the faulty splitter.

[0017] To address the aforementioned technical problems, this invention proposes a modular multilevel converter, including a redundant communication system for submodule networking units in an MMC as described above.

[0018] The beneficial effects of this invention are as follows: the networking unit includes several sub-modules that communicate with each other, and all sub-modules in the networking unit are divided into several sub-module groups. Each sub-module group has at least two other sub-modules in the group that communicate with each other. The networking unit also includes a splitter for transmitting and receiving communication information between the valve control system and the sub-modules. A splitter is matched for each sub-module group, and one side of the splitter is connected to at least two key sub-modules in the group, and the other side is connected to the output of the valve control interface unit. When a key sub-module connected to the splitter fails, the communication information is transmitted and received through another key sub-module connected to the splitter, realizing multiple redundancy in communication between the valve control system and the networking unit, further improving communication reliability, and avoiding the problem of network system paralysis caused by damage to key sub-modules in the network topology. Attached Figure Description

[0019] Figure 1 This is a redundant communication topology diagram of a redundant communication system for a submodule networking unit in MMC proposed in this invention in a practical application scenario; Figure 2 This is a schematic diagram of the data frame format of the instruction information during downlink communication in a communication method for submodule networking units in MMC proposed in this invention; Figure 3 This is a schematic diagram of the data frame format for status information during uplink communication in a communication method for submodule networking units in MMC proposed in this invention; Figure 4 This is a flowchart of the downlink communication process of a communication method for submodule networking units in MMC proposed in this invention in a practical application scenario. Figure 5 This is an uplink communication flowchart of a communication method for submodule networking units in MMC proposed in this invention in a practical application scenario; Figure 6 This is a schematic diagram of the communication process of a submodule networking unit in MMC proposed in this invention in a practical application scenario. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0021] The inventive concept of this invention lies in the following: In a local network (i.e., a network unit) containing n power modules (sub-modules), some of these sub-modules are designated as critical sub-modules. Then, by adding a splitter, the critical sub-modules in the local network are connected to their physically adjacent sub-modules, forming redundant communication for the critical sub-modules. Compared to traditional single-critical-sub-module communication, this is converted to dual-redundant communication, increasing the redundancy between the valve control system and the power modules. This achieves multiple redundancies in communication between the valve control system and the network unit, further improving communication reliability and avoiding network system paralysis caused by damage to critical sub-modules in the network topology. Furthermore, after any critical sub-module fails, its adjacent sub-modules become new critical sub-modules, without affecting the data channel and ensuring system operational stability.

[0022] Specific implementation method 1 of redundant communication system: In a redundant communication system for a submodule networking unit in an MMC proposed in this invention, a main control unit, an interface unit, and a networking unit are included. The main control unit is used to generate control commands and process the status information uploaded by all submodules. The interface unit is used to connect the main control unit and the networking unit, and is the communication hub for the main control unit to send control commands and for submodules to upload status commands. The networking unit includes several submodules, and all submodules communicate with each other via optical fiber. In practical application scenarios, the submodules complete local networking through high-speed communication optical modules and optical fiber patch cords.

[0023] The networking unit comprises several interconnecting sub-modules. All sub-modules within the networking unit are divided into several sub-module groups. Each sub-module in a group must communicate with at least two other sub-modules within that group. It should be noted that the grouping methods include, but are not limited to: dividing sub-module groups according to equal physical spacing; dividing them according to a divisibility criterion of the total number of sub-modules (n) (if the divisibility is not exact, then equal division should be used as much as possible); or, from a communication perspective, ensuring that the synchronization of command responses from all power modules within a group is less than a certain value, while also ensuring unblocked uplink time-division multiplexing of power modules; or, from an interface unit perspective, dividing them according to the maximum number of connections per power module interface chassis divided by the number of groups, which equals the number of modules within each group. When dividing sub-module groups according to equal physical spacing, practical engineering experience will be considered. In cases of high communication redundancy requirements, the equal physical spacing during grouping will be reduced to increase the number of groups (i.e., increase the number of optical splitters). In cases of low communication redundancy requirements, the equal physical spacing during grouping will be increased to reduce the number of groups (i.e., reduce the number of optical splitters). When dividing according to the divisibility of the total number of modules n, the actual engineering practice needs will also be taken into account, especially when the network unit is a ring-shaped U-shaped network. Figure 1 The number and location of the splitters are shown. From a communication perspective, to ensure that the synchronization of command responses from all power modules within a group is less than a certain value, and to ensure unblocked uplink time-division multiplexing of power modules, and from an interface unit perspective, the division is based on the maximum number of connections per power module interface chassis divided by the number of groups, which equals the number of modules in each group. First, the typical value for communication synchronization between sub-modules is determined by combining synchronization with actual engineering requirements: ≤1µs. The number of modules in each group is selected based on the forwarding delay t of a single module, ensuring that the number of modules in each group * t ≤ 1µs. After selecting the number of modules in each group, the number of groups is determined using the formula (maximum number of connections per power module interface chassis divided by the number of groups equals the number of modules in each group). For example, based on the formula ≤1µs, the number of modules in each group * t ≤ 1µs, we get ≤10 modules in each group. If each interface chassis can connect a maximum of 50 sub-modules, then the number of groups is 50 / 10 = 5 groups. The network unit is divided into 5 groups, and one splitter is matched to each group. For example, if a networking unit contains 4 distributors and an interface chassis is configured with 4m sub-modules, and there are p interface chassis in the project, then the total number of sub-modules in the project is 4m*p.

[0024] The networking unit also includes a splitter for transmitting and receiving communication information between the valve control and the submodule. That is, during uplink communication, the submodule can transmit status information to the interface unit and the main control unit through the splitter; during downlink communication, the interface unit can transmit instruction information to the submodule through the splitter.

[0025] Each submodule group is matched with a splitter, and one side of the splitter is connected to at least two key submodules in the group, and the other side is connected to the output of the valve control interface unit; here, the total number of submodule groups in the networking unit equals the number of splitters; preferably, the key submodules in the group connected to one side of the splitter are spatially adjacent submodules, which is the key to forming valve control redundancy.

[0026] In addition, one side of the optical splitter is connected to at least two key sub-modules within the group through at least two sets of transceiver optical fibers; the other side is connected to the output end of the valve control interface unit through at least one set of transceiver optical fibers, wherein each set of transceiver optical fibers includes 1 transceiver optical fiber and 1 transmit optical fiber.

[0027] When a critical submodule connected to the optical splitter fails, the communication information is transmitted and received through another critical submodule connected to the same optical splitter. For example, preferably, the networking unit includes optical splitters 1-4, and each optical splitter connects to two critical submodules. When the first critical submodule of optical splitter 1 fails, other submodules in the submodule group corresponding to optical splitter 1 can rely on the second critical submodule to transmit and receive communication information. Of course, in actual application scenarios, since the submodules in the networking unit can communicate with each other, other submodules in the submodule group corresponding to optical splitter 1 can also rely on submodules in other groups to transmit and receive communication information.

[0028] When a splitter in the networking unit fails, other non-faulty splitters are used to transmit and receive communication information in the submodules of the submodule group corresponding to the faulty splitter. Continuing with the above example (preferably, the networking unit includes splitters 1-4, and each splitter connects to 2 key submodules), when splitter 1 fails, other submodules in the submodule group corresponding to splitter 1 can also rely on submodules in other groups to transmit and receive communication information. That is, as long as one splitter can transmit and receive communication information normally, the networking unit and the main control unit can communicate.

[0029] Specific implementation method 2 for redundant communication system: The redundant communication system for submodule networking units in MMC proposed in this invention will now be explained in conjunction with the accompanying drawings.

[0030] like Figure 1The diagram shows a redundant communication topology for a submodule networking unit in an MMC system proposed in this invention, applied in a practical scenario. The main control cabinet refers to the converter valve control and protection unit, used to send instruction information containing control commands for all submodules in the networking unit to the interface cabinets. Preferably, it includes main control unit A and main control unit B. The interface cabinet refers to the power module interface chassis, used to transmit the instruction information sent by the main control cabinet to the networking unit and to transmit the status information of each submodule uploaded by the networking unit to the main control cabinet. Preferably, it includes interface chassis 1 and interface chassis 2, and each interface chassis includes two core boards. Cross-communication transmission is used between the main control cabinet and the interface cabinets. The instructions sent by the interface chassis are sent from the same main control board, and then other interface units and splitters simply forward them without delay, ensuring consistency across the four downlink instruction messages.

[0031] In the networking unit, it is preferred to have a U-shaped physical arrangement (each sub-module is arranged in two rows with an equal number of sub-modules, and sub-modules of the same sequence in the two rows are opposite each other). Adjacent sub-modules communicate with each other. The networking unit is divided into 4 sub-module groups with equal spacing, and sub-module 1, sub-module n / 3, sub-module 2n / 3 and sub-module n are designated as key sub-modules. According to the connection relationship of the n sub-modules in the networking unit, the adjacent module of sub-module 1 is preferred to be sub-module 2 (that is, sub-module 1 and its adjacent sub-module 2 are designated as key sub-modules for connecting the first optical splitter). The adjacent module of submodule n / 3 is submodule (n / 3+1) (that is, submodule n / 3 and its adjacent submodule (n / 3+1) are used as the key submodules for connecting the second beam splitter), the adjacent module of submodule 2n / 3 is submodule (2n / 3+1) (that is, submodule n / 3 and its adjacent submodule (n / 3+1) are used as the key submodules for connecting the second beam splitter), and the adjacent module of submodule n is submodule (n-1) (that is, submodule n and its adjacent submodule (n-1) are used as the key submodules for connecting the fourth beam splitter).

[0032] A splitter is configured for each submodule group: Submodule group 1 includes splitter 1, with one side connected to submodule 1 and its adjacent submodule 2 via two sets of transceiver fibers (2 receive, 2 transmit). The other side (a) is connected to the output terminal (a) of the core board 1 in interface chassis 1 via one set of transceiver fibers (1 receive, 1 transmit). Similarly, submodule group 2 includes splitter 2, with one side connected to submodule n / 3 and its adjacent submodule (n / 3+1) via two sets of transceiver fibers (2 receive, 2 transmit). The other side (b) is connected to the output terminal (b) of the core board 2 in interface chassis 1 via one set of transceiver fibers (1 receive, 1 transmit). b; Submodule group 3 is equipped with a splitter 3. One side of the splitter 3 is connected to submodule 2n / 3 and its adjacent submodule (2n / 3+1) via two sets of transceiver fibers (2 receive, 2 transmit). The other side c is connected to the output end c of the core board 3 in the interface chassis 2 via one set of transceiver fibers (1 receive, 1 transmit). Submodule group 4 is equipped with a splitter 4. One side of the splitter 4 is connected to submodule n and its adjacent submodule (n-1) via two sets of transceiver fibers (2 receive, 2 transmit). The other side d is connected to the output end d of the core board 4 in the interface chassis 2 via one set of transceiver fibers (1 receive, 1 transmit). This achieves a system where a group of power modules are connected to 4 splitters via 8 short fibers (8 receive, 8 transmit), and the splitters are connected to the power module interface chassis via a long fiber (1 receive, 1 transmit).

[0033] When the valve control sends instruction information containing control commands for all power modules in the network unit to each submodule, that is, during downlink communication, in response to the main control cabinet sending instruction information to the interface chassis, the four core boards in the two interface chassis simultaneously transmit instruction information to their corresponding splitters. Since each submodule in the network unit can communicate with each other, as long as one submodule receives instruction information, other submodules can receive instruction information not only through the splitter but also through the submodule itself, with the first received instruction information being the determining factor. The instruction information is arranged and combined according to the pre-defined control command sequence (see...). Figure 2 Each submodule decodes the instruction information according to the specification to complete downlink communication.

[0034] In downlink communication, downlink communication can still be achieved even if a single optical splitter, a critical submodule, or a group of critical submodules and their adjacent submodules all fail. Specifically, when a single optical splitter fails, command information can be transmitted through other optical splitters so that each submodule can receive the command information; when a critical submodule fails, or a group of critical submodules and their adjacent submodules all fail, command information can be transmitted through other optical splitters, or through the adjacent submodules of the critical submodule. That is, if even one critical submodule connected to the lower end of the optical splitter is functioning normally, both uplink and downlink communication of the submodule can operate normally, thus expanding the communication link with valve control.

[0035] When a submodule uploads status information containing parameters such as voltage of all power modules in its group to the valve control unit, i.e., during uplink communication, each submodule sends status information to the interface chassis via a splitter. Each submodule can upload through any splitter, with the first transmission to the interface chassis taking precedence. The interface chassis then sends the status information to the main control cabinet. Since the status information contains the status information of all submodules, and this information is arranged according to a specific protocol (see...),... Figure 3 The interface chassis synchronously decodes the status information according to the protocol, thereby completing the control and monitoring of the sub-module and completing the uplink communication.

[0036] Similarly, in uplink communication, when one optical splitter fails, status information can be transmitted through other optical splitters so that the central control cabinet can receive the status information; the status of each submodule is also sent to the central control cabinet through status information. The communication between the valve control and the power module can achieve dual redundancy. Both power modules connected to the optical splitter can communicate with the valve control, and the communication link can still be maintained even if either fails.

[0037] Specific implementation method 3 for redundant communication system: Continuing with the specific implementation described above, each optical splitter is connected to two power modules and an interface chassis via transceiver optical fibers. Communication between the interface chassis and the optical splitter (position determined by redundancy) utilizes long optical fibers for both transmission and reception. Furthermore, the communication between the interface chassis and the optical splitter requires at least one long transceiver optical fiber to ensure that the valve control and power modules can perform normal control and monitoring functions. Each optical splitter is connected at its lower end to key power modules and adjacent power modules within the group via at least two sets of transceiver optical fibers, and at its upper end to the valve control via one set of transceiver optical fibers. Power modules within the same group are locally networked via high-speed communication optical modules and fiber optic patch cords.

[0038] Meanwhile, the total number of splitters, the actual number of power module groups, and the number of key sub-modules in this specific embodiment are the same, ensuring that each group of data is sent to the valve control interface unit through the splitter. When grouping, the grouping requirements can be determined according to the divisibility of the total number n, or according to the equal spacing during physical connection, or according to q / m=n (where q is the maximum number of connections in a single power module interface chassis, m is the number of groups, n is the number of modules in each group, and each group is connected to one splitter).

[0039] Communication method 1 of the submodule networking unit in MMC: On the other hand, this invention also proposes a communication method for a submodule networking unit in an MMC, wherein the networking unit includes several submodules that communicate with each other, and all submodules in the networking unit are divided into several submodule groups, and each submodule in the submodule group communicates with at least two other submodules in the group; the networking unit also includes a splitter for transmitting and receiving communication information between the valve control and the submodules; a splitter is matched for each submodule group, and one side of the splitter is connected to at least two key submodules in the group, and the other side is connected to the output end of the valve control interface unit. The method includes: During uplink communication, as each submodule uploads status information to the valve control, the optical splitter receives the status information through the key submodules it is connected to, and uses the information from the first available channel at the interface unit to complete the uplink of submodule status. During downlink communication, the command information issued by the valve control is sent to each optical splitter via the optical splitter, so that the command information can be transmitted to the two key submodules connected to it.

[0040] When a critical submodule in the networking unit fails, another critical submodule on the optical splitter connected to the failed critical submodule is selected to send and receive communication information. The failed critical submodule and the selected critical submodule are connected to the same optical splitter.

[0041] The above approach effectively increases the communication between the submodules and the interface chassis within each group from one submodule transmitting and receiving data to at least two power modules transmitting and receiving data. This can be achieved by adding one optical splitter and two sets of transceiver fibers to each group, doubling the redundancy of the submodules communicating with the valve control system. This ensures that the communication link remains normal even if one power module fails, resolving the previous problem of communication link interruption due to power module failure and improving the reliability of the communication link.

[0042] Communication method 2 for submodule networking units in MMC: Below, referring to the accompanying drawings in the instruction manual... Figure 4-6 The communication method of the submodule networking unit in MMC proposed in this invention will be explained.

[0043] like Figure 4 The diagram shows the downlink communication flowchart of a submodule networking unit in an MMC proposed in this invention, applied in a practical scenario. Preferably, the networking unit includes four optical splitters, each connected to an interface unit. When the interface unit transmits command information to the submodule, as long as one optical splitter successfully transmits (i.e., as long as one interface unit has normal downlink communication), all submodules in the networking unit can receive the command information. When all optical splitters fail to transmit command information, the data of the decoded command information in the submodule is not updated.

[0044] like Figure 5 The diagram shows the uplink communication flowchart of a submodule networking unit in an MMC proposed in this invention, applied in a practical scenario. Preferably, the networking unit includes four optical splitters, each connected to an interface unit. When a submodule transmits status information to an interface unit, as long as one optical splitter successfully transmits (i.e., as long as one interface unit has normal uplink communication), all submodules in the networking unit can send status information. When all optical splitters fail to transmit command information, the submodule status information is not updated.

[0045] like Figure 6 The diagram shown is a schematic of the communication process of a submodule networking unit in MMC proposed in this invention in a practical application scenario. Preferably, the networking unit includes 4 optical splitters, and each optical splitter is connected to an interface unit. Regardless of uplink or downlink communication, normal communication can be achieved unless the communication of all interface chassis fails.

[0046] On the other hand, the present invention also proposes a modular multilevel converter, including a redundant communication system of the sub-module networking unit in MMC as described above. For specific implementation of the modular multilevel converter, please refer to the specific implementation of the redundant communication system of the sub-module networking unit in MMC as described above, which will not be repeated here.

[0047] In summary, this invention, by adding a beam splitter, combines two power modules to achieve redundancy. Information from the first channel to be resolved is used first, while simultaneously communicating with the valve control interface unit. Without increasing the pressure on valve control resolution, this achieves sufficient redundancy in communication with the valve control interface unit, ensuring dual redundancy control and improving system redundancy.

Claims

1. A redundant communication system for submodule networking units in an MMC, characterized in that, The networking unit includes several interconnected sub-modules. All sub-modules in the networking unit are divided into several sub-module groups. Each sub-module group has at least two other sub-modules in the group that communicate with each other. The networking unit also includes a splitter for transmitting and receiving communication information between the valve control and the sub-modules. A splitter is matched to each sub-module group, and one side of the splitter is connected to at least two key sub-modules in the group, and the other side is connected to the output of the valve control interface unit. When a critical submodule connected to the optical splitter fails, the communication information is transmitted and received through another critical submodule connected to the optical splitter.

2. The redundant communication system for the submodule networking unit in MMC according to claim 1, characterized in that, One side of the optical splitter is connected to at least two key sub-modules within the group via at least two sets of transceiver optical fibers; the other side is connected to the output end of the valve control interface unit via at least one set of transceiver optical fibers.

3. The redundant communication system for the submodule networking unit in MMC according to claim 2, characterized in that, The transceiver fiber used to connect one side of the optical splitter to the key submodule is a short optical fiber; the transceiver fiber used to connect the other side of the optical splitter to the output end of the valve control interface unit is a long optical fiber.

4. The redundant communication system for the submodule networking unit in MMC according to claim 1, characterized in that, When the networking unit includes n sub-modules, the sub-modules are arranged in two rows in equal numbers, and the sub-modules with the same sequence in the two rows are paired up to form a U-shaped physical arrangement of the network, wherein adjacent sub-modules communicate with each other. Submodule 1 and its adjacent submodule 2 are used as key submodules for connecting the first optical splitter; Submodule n / 3 and its adjacent submodules (n / 3+1) are used as key submodules for connecting the second beam splitter; Submodule 2n / 3 and its adjacent submodule (2n / 3+1) are used as key submodules for connecting the third beam splitter; Submodule n and its adjacent submodules (n-1) are used as key submodules for connecting the fourth beam splitter.

5. The redundant communication system for the submodule networking unit in MMC according to claim 1, characterized in that, The key submodules in each submodule group are physically adjacent submodules.

6. The redundant communication system for the submodule networking unit in MMC according to claim 1, characterized in that, When a splitter in the networking unit fails, other non-faulty splitters are used to send and receive communication information in the sub-modules of the sub-module group corresponding to the faulty splitter.

7. A communication method for submodule networking units in an MMC, characterized in that, The networking unit includes several interconnecting sub-modules. All sub-modules in the networking unit are divided into several sub-module groups. Each sub-module group has at least two other sub-modules within that group that communicate with each other. The networking unit also includes an optical splitter for transmitting and receiving communication information between the valve control and the sub-modules. An optical splitter is matched to each sub-module group, with one side of the splitter connected to at least two key sub-modules within the group and the other side connected to the output of the valve control interface unit. The method includes: When a critical submodule in the networking unit fails, another critical submodule on the optical splitter connected to the failed critical submodule is selected to send and receive communication information. The failed critical submodule and the selected critical submodule are connected to the same optical splitter.

8. The communication method of the submodule networking unit in MMC according to claim 7, characterized in that, During downlink communication, each submodule is assigned its own execution instruction time. After all submodules receive the instruction information, all submodules are controlled to perform on / off operations according to their respective execution instruction times.

9. The communication method of the submodule networking unit in MMC according to claim 7, characterized in that, During uplink communication, status information is communicated according to the time-division multiplexing principle.

10. The communication method of the submodule networking unit in MMC according to claim 7, characterized in that, When a splitter in the networking unit fails, other non-faulty splitters are used to send and receive communication information in the sub-modules of the sub-module group corresponding to the faulty splitter.

11. A modular multilevel converter, characterized in that, A redundant communication system including the submodule networking unit in the MMC as described in any one of claims 1-6.

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