Method for multiplexing station protection and control communication channels of multi-terminal direct current transmission system

Abstract

The application discloses a method for multiplexing of station-to-station protection and control communication channels of a multi-terminal DC power transmission system, wherein the multi-terminal DC power transmission system comprises n converter stations S1, S2,..., Sn, each of which has a control unit and a protection unit, the protection units of different converter stations realize transmission of protection signals through station-to-station protection communication channels, the control units of different converter stations realize transmission of control signals through station-to-station control communication channels, the station-to-station protection communication channels and the station-to-station control communication channels are mutually multiplexed and redundant; when a protection communication channel fails, protection signals are transmitted through a control communication channel; when a control communication channel fails, control signals are transmitted through a protection communication channel. The application further improves the reliability of station-to-station communication of the multi-terminal DC power transmission system; no modification is made to the hardware architecture of the DC control and protection system, and no additional investment is needed.

Description

Technical Field

[0001] This invention relates to a method for multiplexing inter-station protection and control communication channels, and more particularly to a method for multiplexing inter-station protection and control communication channels in a multi-terminal DC transmission system. Background Technology

[0002] In the conventional design of inter-station communication for control and protection in existing multi-terminal DC transmission systems, although the inter-station protection communication channel and the inter-station control communication channel are physically connected, they are actually independent in use. When the busbar protection of the hub station of the multi-terminal DC transmission system operates, in addition to locking the converter valve and tripping the AC circuit breaker of the station through its own control device, the operation signal also needs to be sent to other stations connected to the busbar to lock the converter valves of those other stations. In the existing technology, the inter-station protection communication channel only transmits the busbar protection operation signal through the inter-station protection communication channel. If all inter-station protection communication channels associated with the hub station fail or are out of service, the protection operation signal of the hub station cannot be sent to other stations. Similarly, the inter-station control communication channel only transmits the control signal. If all inter-station control communication channels associated with the signal-issuing station fail or are out of service, the signal cannot be sent to other stations. Therefore, the reliability of the correct transmission of protection and control communication between stations in multi-terminal DC transmission systems is low. Summary of the Invention

[0003] Purpose of the invention: The purpose of this invention is to provide a method for multiplexing inter-station protection and control communication channels in a multi-terminal DC transmission system to achieve cross-circuit transmission of signals and high transmission reliability.

[0004] Technical Solution: The multi-terminal DC transmission system described in this invention includes n converter stations S1, S2, ..., Sn, which are connected by a busbar. Each converter station has a control unit and a protection unit. The protection units of different converter stations transmit protection signals through inter-station protection communication channels, and the control units of different converter stations transmit control signals through inter-station control communication channels. The inter-station protection communication channels and inter-station control communication channels are reused and redundant. When a protection communication channel fails, the protection signal is transmitted through the control communication channel; when a control communication channel fails, the control signal is transmitted through the protection communication channel.

[0005] There are two path options for inter-station protection communication between converter stations Si and Sj, where 1≤i <j≤n:

[0006] Path (1) is the direct inter-station protection communication channel between converter station Si and converter station Sj, or the inter-station protection communication channel between converter station Si and converter station Sj via a third station; Path (2) is the protection action signal of converter station Si first transmitted to the control unit of this station, and then transmitted to converter station Sj via the direct control communication channel Si-Sj between converter station Si and converter station Sj or the inter-station control communication channel via a third station; Path (1) and Path (2) are ORed.

[0007] When a busbar protection action occurs at a certain hub converter station Sj, in addition to locking the converter valve of the station and tripping the AC circuit breaker of the station through the station's control device, the protection action signal also needs to be sent to other converter stations Si connected to the busbar, and communication path (1) or path (2) is selected to realize the transmission of the protection action signal between stations.

[0008] There are two path options for inter-station control communication between converter stations Si and Sj, where 1≤i <j≤n:

[0009] Path (a) is the direct inter-station control communication channel between converter station Si and converter station Sj, or the inter-station control communication channel between converter station Si and converter station Sj via a third station; Path (b) is the control signal of converter station Si first transmitted to its own protection unit, and then transmitted to converter station Sj via the direct protection communication channel Si-Sj between converter station Si and converter station Sj, or the inter-station protection communication channel via a third station; Path (a) and Path (b) are ORed.

[0010] Compared with the prior art, the present invention has the following significant advantages: 1. Based on the conventional protection communication channel between stations of a multi-terminal DC transmission system, the inter-station control communication channel of the multi-terminal DC transmission system is incorporated into the backup of the conventional protection communication channel. When all conventional protection communication channels between stations fail or are out of service, it ensures that protection signals and control signals are still transmitted correctly and quickly between stations; 2. Without making any changes to the hardware architecture of the DC control and protection system, it achieves improved communication reliability without requiring additional investment, thus having excellent economic efficiency. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the control and protection unit and its inter-station communication channel of the multi-terminal DC transmission system involved in this invention.

[0012] Figure 2 This is a schematic diagram of the communication connection between the protection and control units in the converter station of the multi-terminal DC transmission system of the present invention;

[0013] Figure 3 This is a schematic diagram of the protection signal transmission in the event of a communication channel outage or failure according to the present invention;

[0014] Figure 4 This is a schematic diagram of the control signal transmission under the condition of control communication channel shutdown or failure according to the present invention. Detailed Implementation

[0015] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0016] In the current conventional design of inter-station communication for control and protection in multi-terminal DC transmission systems, the protection communication channel and the control communication channel between stations each form an independent communication closed loop. However, in the configuration of the control and protection unit in a DC converter station, the protection unit and the control unit are connected via optical fiber.

[0017] Taking a three-terminal DC transmission system as an example, its implementation process is as follows:

[0018] like Figure 1 The diagram shows the schematic of the control and protection unit and its inter-station communication channel of the multi-terminal DC transmission system involved in this invention. The multi-terminal DC transmission system includes three converter stations S1, S2, and S3. Converter station S2 is connected to converter stations S1 and S3 via a busbar and is referred to as the hub converter station. Each converter station S1, S2, and S3 has its own control and protection units. The protection units of different stations transmit protection signals through inter-station protection communication channels, and the control units of different stations transmit control signals through inter-station control communication channels.

[0019] In this invention, the inter-station protection communication channel and the inter-station control communication channel can be reused and are redundant with each other. That is, when the protection communication channel fails, the protection signal can be transmitted through the control communication channel, and when the control communication channel fails, the control signal can be transmitted through the protection communication channel.

[0020] like Figure 2 As shown, the DC protection unit adopts a triple configuration, and all three protection devices communicate with the two-out-of-three device and the control host via fiber optic cables, respectively, transmitting verified digital signals to ensure reliability and safety. Although the inter-station protection communication channel and the inter-station control communication channel are physically connected, they are independent in actual use.

[0021] (I) Inter-station protection signal transmission process of a three-terminal DC transmission system

[0022] In a multi-terminal DC system, when the busbar protection of a hub converter station is activated, the protection activation signal needs to be sent to other converter stations connected to the busbar in this hub station.

[0023] like Figure 3As shown, when the busbar protection of converter station S2 operates, in addition to locking the converter valve and tripping the AC circuit breaker of the station through its own control device, the operation signal also needs to be sent to converter station S1, which is connected to the busbar. At this time, both the direct protection communication channel S2-S1 between converter station S2 and converter station S1, and the detour protection communication channel S2-S3-S1 via converter station S3, are faulty or out of service for other reasons. The protection operation signal can first be transmitted to the control unit of the station, and then transmitted to converter station S1 through the direct control communication channel S2-S1 between converter station S2 and converter station S1, or through the detour control communication channel S2-S3-S1 via converter station S3.

[0024] When the busbar protection of converter station S2 operates, in addition to locking the converter valve and tripping the AC circuit breaker of the station through its own control device, the operation signal also needs to be sent to converter station S3, which is connected to the busbar. At this time, if the direct protection communication channel S2-S3 between converter station S3 and converter station S2, and the detour protection communication channel S2-S1-S3 via converter station S1, both fail or are out of service for other reasons, the protection signal can first be transmitted to the control unit of the station, and then transmitted to converter station S3 through the direct control communication channel S2-S3 between converter station S2 and converter station S3, or through the detour control communication channel S2-S1-S3 via converter station S1.

[0025] (II) Inter-station control signal transmission process of a three-terminal DC transmission system

[0026] like Figure 4 As shown, if the inter-station control communication channel between the control units of converter station S1 and converter station S2 fails or is shut down for other reasons, including the direct inter-station control communication channel S1-S2 between converter station S1 and converter station S2, and the inter-station control communication channel S1-S3-S2 between converter station S1 and converter station S2 via converter station S3, then the inter-station control signals of the control units of converter station S1 and converter station S2 can be transmitted through the communication channel between the control unit and the protection unit of this station, as well as the inter-station protection communication channel between the protection units of converter station S1 and converter station S2.

[0027] If the inter-station control communication channel between the control units of converter stations S1 and S3 fails or is taken out of service for other reasons, including the direct connection control communication channel S1-S3 between converter stations S1 and S3 and the control communication channel S1-S2-S3 that bypasses through converter station S2 between converter stations S1 and S3 failing or being taken out of service for other reasons, the inter-station control signals between the control units of converter stations S1 and S3 can be transmitted through the communication channel between the control unit and the protection unit of each station, as well as the inter-station protection communication channel between the protection units of converter stations S1 and S3.

[0028] If the inter-station control communication channel between the control units of S3 fails or is taken out of service for other reasons, including the direct connection control communication channel S2-S3 between S2 and S3 and the control communication channel S2-S1-S3 that bypasses through S1 between S2 and S3 failing or being taken out of service for other reasons, the inter-station control signals between the control units of S2 and S3 can be transmitted through the communication channel between the control unit and the protection unit of each station, as well as the inter-station protection communication channel between the protection units of S2 and S3.

[0029] (3) Process of multiplexing inter-station protection and control communication channels in a multi-terminal DC power transmission system

[0030] The method of the present invention is also applicable to the case of having n converter stations S1, S2... Sn, etc. If the inter-station protection communication channel between converter stations Si and Sj is interrupted, where 1 ≤ i < j ≤ n, the protection signal can be transmitted using the inter-station control communication channel between converter stations Si and Sj; the transmission of the inter-station protection signal is carried out by referring to the transmission process of the inter-station protection signal in a three-terminal DC power transmission system.

[0031] The method of the present invention is also applicable to the case of having n converter stations S1, S2... Sn, etc. If the inter-station control communication channel between converter stations Si and Sj is interrupted, where 1 ≤ i < j ≤ n, the control signal can be transmitted using the inter-station protection communication channel between converter stations Si and Sj; the transmission of the inter-station control signal is carried out by referring to the transmission process of the inter-station control signal in a three-terminal DC power transmission system.

[0032] The above embodiments are only used to illustrate the technical solution of the present invention and are not intended to limit it. All forms of modification or change made by referring to the above embodiments are within the protection scope of the present invention.

Claims

1. A method for multiplexing inter-station protection and control communication channels in a multi-terminal DC transmission system, wherein the multi-terminal DC transmission system includes n converter stations S1, S2, ..., Sn, each converter station having a control unit and a protection unit, the protection units of different converter stations transmitting protection signals through inter-station protection communication channels, and the control units of different converter stations transmitting control signals through inter-station control communication channels, characterized in that: The inter-station protection communication channel and the inter-station control communication channel are reused and redundant; when the protection communication channel fails, the protection signal is transmitted through the control communication channel; when the control communication channel fails, the control signal is transmitted through the protection communication channel. There are two path options for inter-station protection communication between converter stations Si and Sj, where 1≤i <j≤n: Path (1), the direct inter-station protection communication channel between converter station Si and converter station Sj, or the inter-station protection communication channel between converter station Si and converter station Sj via a third station. Path (2): The protection action signal of converter station Si is first transmitted to the control unit of this station, and then transmitted to converter station Sj through the direct control communication channel Si-Sj from converter station Si to converter station Sj or the inter-station control communication channel of the third station. The OR logic is used for path (1) and path (2); When a busbar protection action occurs at a certain hub converter station Sj, in addition to blocking the converter valve of the station and tripping the AC circuit breaker of the station through the station's control unit, the protection action signal also needs to be sent to other converter stations Si connected to the busbar, and communication path (1) or path (2) is selected to realize the transmission of the inter-station protection action signal.

2. The method for multiplexing inter-station protection and control communication channels in a multi-terminal DC transmission system according to claim 1, characterized in that: There are two path options for inter-station control communication between converter stations Si and Sj, where 1≤i <j≤n: Path (a), the direct inter-station control communication channel between converter station Si and converter station Sj, or the inter-station control communication channel between converter station Si and converter station Sj via a third station. In path (b), the control signal of converter station Si is first transmitted to the protection unit of this station, and then transmitted to converter station Sj through the direct protection communication channel Si-Sj from converter station Si to converter station Sj or the inter-station protection communication channel of the third station. The OR logic is used for path(a) and path(b).

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