Method and device for identifying and processing converter station status of multi-terminal DC transmission system

Abstract

The present invention discloses a method and device for identifying and processing the status of converter stations in a multi-terminal DC transmission system. The method defines the status of each converter station in the DC transmission system as three states: valid / invalid, connected / off-grid, and running / non-running, wherein the valid / invalid state is an enabling setting, the connected / off-grid state is the actual switch knife state of the busbar area, and the running / non-running is the unlocking state of the converter. By setting the enabling setting of each station and actually operating the switch knife, the control and protection system of the present invention can automatically adapt to all working conditions of the entire multi-terminal DC transmission system from the construction period to the full commissioning and operation, simplifying the operation and maintenance work, and ensuring the safe and stable operation of the multi-terminal DC transmission system.

Description

Technical Field

[0001] The present invention relates to a method and a device for identifying and processing the state of a converter station, and in particular to a method and a device for identifying and processing the state of a converter station in a multi-terminal direct current transmission system. Background Art

[0002] DC transmission technology has been widely used in the fields of cross-regional power transmission, interconnection of major power grids, access to distributed energy, island power supply, and power supply to large cities due to its huge advantages such as low line loss, long transmission distance, large transmission capacity, no need for synchronous operation, and rapid power adjustment. When multiple power supply areas are required to supply power to multiple load centers, multi-terminal DC transmission is more economical and flexible than two-terminal point-to-point DC transmission.

[0003] Since the commissioning of the first multi-terminal DC project in China, the Guangdong Nan'ao three-terminal flexible DC project in 2013, the Zhejiang Zhoushan five-terminal flexible DC project, the Zhangbei DC power grid project, the Lugaozhao three-terminal conventional DC project, and the Wudongde three-terminal hybrid DC project have also been put into operation. At the beginning of the system debugging stage of the multi-terminal DC project, due to the asynchronous progress of the construction of each station and the debugging of the subsystem, the system debugging work is generally carried out between the two converter stations that have been completed the fastest, and even the two ends are put into operation first, and then the system joint debugging and commissioning of other converter stations that have been completed successively are carried out. In the stage of not fully commissioning, the signals sent by these converter stations that are not yet ready may affect the normal operation of the converter stations. Therefore, the signals sent by these stations are generally shielded by physical communication interruption methods such as unplugging the optical fiber of the inter-station channel or disconnecting the power supply of the inter-station communication device. At the same time, the program of the running station needs to download a special version to specially shield or process some status signals of these stations (such as: the switch knife status of the busbar area, etc.), which makes program control extremely inconvenient. In addition, even if the multi-terminal DC transmission system has been fully put into operation, if some converter stations, especially those containing busbar areas, need maintenance, in order to ensure that the normal operation of other converter stations is not affected, it is also necessary to avoid mutual influence through communication interruption and other means, making the maintenance work complicated and inflexible.

[0004] The patent "Method and device for judging the operating status of converter stations in a multi-terminal flexible DC transmission system" (CN201810876421.9) discloses a method for judging the on-grid and off-grid operating status of converter stations in a multi-terminal flexible DC transmission system. The method can distinguish between the on-grid operation and off-grid maintenance states of converter stations. However, the separation breakpoints of each station are set at the pole connection of the converter station. In this way, the DC lines of non-operating stations may be in a no-load operation state. In addition, the isolation problem during the construction period of the converter station has not been solved. Moreover, the practice of maintaining the status unchanged after the communication is interrupted also limits the operation mode during maintenance (such as: after the busbar area is overhauled, the number of other converter stations in operation needs to be changed). Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a method and device for identifying and processing the status of a converter station in a multi-terminal DC transmission system, which can accurately distinguish between various states such as the converter station construction period, commissioning operation, safety maintenance, etc., and effectively process the inter-station communication signals in each state.

[0006] Technical solution: The method for identifying and processing the status of a converter station of the present invention, each converter station is connected to the busbar area through a DC line, and the status of the converter station is classified into:

[0007] (a) Valid / invalid state: The converter station is configured with the enabling setting of each station. Enable means valid state, and disable means invalid state.

[0008] (b) On-grid / off-grid status: When the DC line from the busbar area to the converter station is connected, it is in the on-grid status; when it is not connected, it is in the off-grid status;

[0009] (c) Operation / non-operation status: the converter station is unlocked for operation status, and the converter station is not unlocked for non-operation status;

[0010] When the converter station is in an effective state, all signals from the converter station are received; when the converter station is in an invalid state, no signal from the converter station is received;

[0011] When the converter station is in an effective and connected state, it is considered that the station has been or is about to be connected to the DC transmission system for operation, and the multi-station continuous jump signal from the station is processed;

[0012] When the converter station is off-grid, it is considered that the station is completely isolated from the DC transmission system, and the multi-station continuous trip signal from the station is not processed;

[0013] When the converter station is in an effective, connected and operating state, it is considered that the station has been connected to the DC transmission system for operation, and multi-station power coordination instructions are sent to the station and the power coordination instructions from the station are processed.

[0014] Furthermore, when the converter station including the busbar area is in an invalid state, the on-grid / off-grid state of each converter station can be manually set and modified at the operator's workstation.

[0015] Furthermore, in the event of an abnormality in inter-station communication between a converter station and a converter station containing a busbar busbar area, the line connection status from the busbar busbar area to each converter station detected immediately before the abnormality in inter-converter station communication is locked as the initial status of the on-grid / off-grid status of each converter station, and the on-grid / off-grid status of each converter station can be manually set and modified at the operator's workstation.

[0016] Furthermore, when the converter station is in an online state, the multi-station hopping signal of the station is sent to other converter stations; when the converter station is in an offline state, the station does not send the multi-station hopping signal.

[0017] Furthermore, when the converter station is in the connected state, the operation of the DC transmission system needs to consider the equipment status signal of the station.

[0018] The device for identifying and processing the status of a converter station of the present invention comprises: a valid / invalid status identification unit, an on-grid / off-grid status identification unit, an operating / non-operating status identification unit and a multi-status processing unit;

[0019] The function implemented by the effective / ineffective state distinguishing unit is: the enabling setting value of each station is configured through the converter station, if the output is enabled, it is effective; if the output is not enabled, it is invalid;

[0020] The function of the on-grid / off-grid state identification unit is: when the DC line from the busbar area to the converter station is connected, the output is an on-grid state; when the DC line from the busbar area to the converter station is not connected, the output is an off-grid state;

[0021] The function of the operation / non-operation state distinguishing unit is: when the converter station is unlocked, the output is the operation state, and when the converter station is not unlocked, the output is the non-operation state;

[0022] The multi-state processing unit adjusts the original inter-station communication signals of each station in combination with the results of the valid / invalid state distinguishing unit, the networked / off-grid state distinguishing unit, and the running / non-running state distinguishing unit to generate a processed signal for actual use, and realizes the following functions: when the converter station is in a valid state, all signals from the converter station are received; when the converter station is in an invalid state, no signal from the converter station is received; when the converter station is in a valid and networked state, it is deemed that the station has been or is about to be connected to the DC transmission system for operation, and the multi-station continuous tripping signal from the station is processed; when the converter station is in an off-grid state, it is deemed that the station is completely isolated from the DC transmission system, and the multi-station continuous tripping signal from the station is not processed; when the converter station is in a valid, networked and running state, it is deemed that the station has been connected to the DC transmission system for operation, and a multi-station power coordination instruction is sent to the station and the power coordination instruction from the station is processed.

[0023] Compared with the prior art, the present invention has the following significant effects: 1. The present invention defines the status of the converter station of the multi-terminal DC transmission system as three states: valid / invalid, connected / off-grid, and running / non-running. By identifying the three states, the actual working mode of each converter station is distinguished and corresponding processing measures are taken. Other states of the converter station can also be effectively distinguished by these three states. Therefore, the special operating conditions of the multi-terminal DC transmission system no longer need to be manually adapted through artificial disconnection of the station communication device and downloading of special version programs; 2. After adopting the present invention, the operating personnel only need to set the enabling setting of each station and actually operate the switch knife switch, and the control and protection system can automatically adapt to all working conditions of the multi-terminal DC transmission system from the construction period to the commissioning operation, which simplifies the operation and maintenance work and ensures the safe and stable operation of the multi-terminal DC transmission system. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of a three-terminal direct current transmission system of the present invention;

[0025] Figure 2 (a) is a signal flow chart of a converter station state identification and processing device including a busbar bus station of the present invention, and (b) is a signal flow chart of a converter station state identification and processing device without a busbar bus station of the present invention. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0027] Each converter station in the multi-terminal DC power transmission system of the present invention is connected to the busbar area via a DC line. Figure 1 The figure shows a three-terminal DC transmission system. The DC sides of the three converter stations are connected to the busbars BUS1 and BUS2 of the second converter station through two positive and negative DC lines. Isolation devices ZL11, ZL21 and ZL31 are arranged between the busbar BUS1 and the DC lines of the three converter stations. Isolation devices ZL12, ZL22 and ZL32 are arranged between the busbar BUS2 and the DC lines of the three converter stations.

[0028] The definition of converter station status consists of three parts:

[0029] (a) Valid / invalid state: The converter station is configured with the enabling setting of each station. Enable means valid state, and disable means invalid state.

[0030] Among the converter stations to be put into operation, those still under construction will be set to an invalid state; and those that have been put into operation or are undergoing networking testing will be set to a valid state, which can distinguish the validity of the signal source.

[0031] (b) On-grid / off-grid status: When the DC line from the busbar area to the converter station is connected, it is in the on-grid status; when it is not connected, it is in the off-grid status.

[0032] like Figure 1 As shown, since the converter station can operate with a single pole, the networking state is also divided into positive / negative networking state. When the isolation device ZL11 is closed, the first converter station is in the positive networking state; when the isolation device ZL12 is closed, the first converter station is in the negative networking state; when the isolation device ZL21 is closed, the second converter station is in the positive networking state; when the isolation device ZL22 is closed, the second converter station is in the negative networking state; when the isolation device ZL31 is closed, the third converter station is in the positive networking state; when the isolation device ZL32 is closed, the third converter station is in the negative networking state. The networking state is entered only when a certain station or a certain pole needs to be networked and operated, and it should remain off-grid at other times.

[0033] (c) Operation / non-operation status: The converter station is unlocked for operation status, and unlocked for non-operation status. Since the converter station can operate with a single pole, the operation status is also divided into positive / negative operation status.

[0034] When the converter station is in an effective state, all signals from the converter station are received; when the converter station is in an invalid state, no signal from the converter station is received.

[0035] The signals sent from converter stations under construction are shielded and will not cause malfunction of the DC transmission system.

[0036] When the converter station is in an effective and connected state, it is deemed that the station has been or is about to be connected to the DC transmission system for operation, and the multi-station continuous tripping signals transmitted by the station are processed; when the converter station is in an off-grid state, it is deemed that the station is completely isolated from the DC transmission system, and the multi-station continuous tripping signals transmitted by the station are not processed.

[0037] If a converter station in the networking test or commissioning period is already in the networking state, it means that the station has been partially or completely connected to the DC transmission system. Therefore, if the converter station requires the entire DC transmission system to trip, other converter stations in the DC transmission system should respond effectively. When a converter station needs to be repaired, it is operated to the off-grid state, and the DC transmission system will not respond to the multi-station trip signal sent by the station.

[0038] When the converter station is in an effective, connected and operating state, it is considered that the station has been connected to the DC transmission system for operation, and multi-station power coordination instructions are sent to the station and the power coordination instructions from the station are processed.

[0039] For a converter station in the networking test or commissioning period, if it is already connected to the network and in operation, it means that the station has been connected to the DC transmission system and unlocked for operation. Therefore, the converter station needs to coordinate power with other converter stations in the DC transmission system.

[0040] When the converter station including the busbar area is in an invalid state, the on-grid / off-grid state of each converter station can be manually set and modified at the operator's workstation.

[0041] like Figure 1 As shown, the second converter station is a converter station including a busbar area. If the second converter station is still under construction, the location information of the isolation devices ZL11, ZL12, ZL21, ZL22, ZL31 and ZL32 can be manually set for the first converter station and the third converter station to match the actual electrical connection.

[0042] In case of abnormal inter-station communication between any converter station and the converter station containing the busbar busbar area, the line connection status from the busbar busbar area to each converter station detected at the last moment before the abnormal inter-station communication occurs is locked as the initial state of the on-grid / off-grid status of each converter station. The on-grid / off-grid status of each converter station can be manually set and modified at the operator's workstation.

[0043] If the inter-station communication of the second converter station changes from normal to abnormal, the position information of the isolation devices ZL11, ZL12, ZL21, ZL22, ZL31 and ZL32 in the first converter station and the third converter station will maintain the state before the communication abnormality. If the state changes, it can be manually set to match the actual electrical connection.

[0044] When the converter station is in the networked state, the multi-station hopping signal of the station is sent to other converter stations; when the converter station is in the off-grid state, the station does not send the multi-station hopping signal.

[0045] If a converter station in the networking test or commissioning period is already in the networking state, it means that the station has been partially or fully connected to the DC transmission system, so the converter station is allowed to send a continuous trip signal to the entire DC transmission system. When the converter station needs to be repaired, it is operated to the off-grid state, and the station is no longer allowed to send a continuous trip signal to the entire DC transmission system.

[0046] When the converter station is in the connected state, the operation of the DC transmission system needs to consider the equipment status signal of the station.

[0047] The converter station status identification and processing device of the present invention comprises: an effective / ineffective status identification unit, an on-grid / off-grid status identification unit, an operating / non-operating status identification unit and a multi-status processing unit. The functions implemented by each status identification unit are as follows:

[0048] Valid / invalid state identification unit: The converter station is equipped with the enabling setting value of each station. Enable means valid state; disable means invalid state.

[0049] On-grid / off-grid status identification unit: When the DC line from the busbar area to the converter station is connected, it is on-grid; when it is not connected, it is off-grid;

[0050] Operation / non-operation status identification unit: when the converter station is unlocked, it is in operation status; when the converter station is not unlocked, it is in non-operation status;

[0051] The above-mentioned state identification units are respectively used to automatically identify the three states of each station.

[0052] Multi-state processing unit: When the converter station is in the effective state, it receives all signals from the converter station; when the converter station is in the invalid state, it does not receive all signals from the converter station; when the converter station is in the networked state, it is regarded as the station has been or is about to be connected to the DC transmission system for operation, and processes the multi-station continuous tripping signals from the station; when the converter station is in the off-grid state, it is regarded as the station is completely isolated from the DC transmission system, and does not process the multi-station continuous tripping signals from the station; when the converter station is in the networked and operating state, it is regarded as the station has been connected to the DC transmission system for operation, sends multi-station power coordination instructions to the station and processes the power coordination instructions from the station. The multi-state processing unit is used to automatically process the communication signals of each station.

[0053] Figure 2 (a) in it is a signal flow chart of the state identification and processing device of the converter station containing the busbar station of the present invention, which describes the signal inflow and outflow relationship of the above three state identification units and the multi-state processing unit. The multi-state processing unit adjusts the original signal of the station-to-station communication of each converter station in combination with the three state identification results to generate a processed signal for actual use. Among them, for the valid / invalid state identification unit, it is only necessary to judge according to the enable constant; for the running / non-running state identification unit, the running / non-running state identification result is generated according to the unlocking state of the converter station in the processed signal; for the connected / off-grid state identification unit, according to the DC line connection state from the busbar area to each converter station in the processed signal containing the busbar station, the connected / off-grid state identification result of each station is generated; because the connected / off-grid state of each station is determined by the switch knife switch of the busbar area, the connected / off-grid state identification unit is only configured in the processing of the inter-station communication signal of the busbar station.

[0054] The functions realized by the multi-state processing unit are as follows: when the converter station containing the busbar area is in an invalid state, the on-grid / off-grid state of each converter station can be manually set and modified at the operator's workstation. When the converter station is in an on-grid state, the multi-station continuous trip signal of the station is sent to other converter stations, and the operation of the DC transmission system needs to consider the equipment status signal of the station; when the converter station is in an off-grid state, the station does not send a multi-station continuous trip signal.

[0055] The function of the on-grid / off-grid status identification unit is as follows: when the inter-station communication between the converter station and the converter station containing the busbar area is abnormal, the line connection status from the busbar area to each converter station detected just before the inter-station communication abnormality is locked as the initial state of the on-grid / off-grid status of each converter station. The on-grid / off-grid status of each converter station can be manually set and modified at the operator's workstation.

[0056] Figure 2 (b) is a signal flow chart of the converter station state identification and processing device of the present invention without a busbar bus station. The multi-state processing unit adjusts the original inter-station communication signal of each station in combination with the three state identification results to generate a processed signal for actual use. Among them, for the valid / invalid state identification unit, it only needs to be judged according to the enable constant value; and the running / non-running state identification unit will further process other signals according to some signals in the processed signal, that is, there is an iterative process; the networked / off-grid state of each converter station and the original inter-station communication signal are directly used as the signal input of the multi-state processing unit.

[0057] The present invention defines the status of the converter station of the multi-terminal DC transmission system into three parts: valid / invalid, connected / off-grid, and operating / non-operating status. By identifying the status of these three parts, the actual working mode of each converter station can be distinguished and corresponding processing measures can be taken. When the converter station is still in the construction period, it is set to an invalid state, and all signals sent by it are not received; when the converter station is put into operation, it is set to an effective connected operating state, and the converter stations in this state respond to power coordination instructions and multi-station continuous jump signals from each other; when the converter station needs maintenance, it is set to an off-grid non-operating state, and other stations no longer receive the multi-station continuous jump signals sent by it. In addition to the above three states, other states of the converter station can also be effectively distinguished by these three states. Therefore, the special operating conditions of the multi-terminal DC transmission system no longer need to be manually adapted by artificially disconnecting the station communication device and downloading a special version of the program. After adopting the present invention, the operating personnel only need to adjust the enabling setting of each station and actually operate the switch knife switch. The control and protection system can automatically adapt to all working conditions of the multi-terminal DC transmission system from the construction period to the commissioning operation, which simplifies the operation and maintenance work and ensures the safe and stable operation of the multi-terminal DC transmission system.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention and are not intended to limit the present invention. A person skilled in the art should understand that the person skilled in the art may modify or replace the specific implementation of the present invention with equivalents, but these modifications or changes are within the scope of protection of the patent application to be approved.

Claims

1. A method for identifying and processing the status of a converter station in a multi-terminal direct current transmission system, wherein each converter station in the multi-terminal direct current transmission system is connected to a busbar area through a direct current line, characterized in that: Converter station status is classified as follows: (a) Valid / invalid state: The converter station is configured with the enabling setting of each station. Enable means valid state, and disable means invalid state. (b) On-grid / off-grid status: When the DC line from the busbar area to the converter station is connected, it is in the on-grid status; when it is not connected, it is in the off-grid status; (c) Operation / non-operation status: the converter station is unlocked for operation status, and the converter station is not unlocked for non-operation status; When the converter station is in an effective state, all signals from the converter station are received; when the converter station is in an invalid state, no signal from the converter station is received; When the converter station is in an effective and connected state, it is considered that the station has been or is about to be connected to the DC transmission system for operation, and the multi-station continuous jump signal from the station is processed; When the converter station is off-grid, it is considered that the station is completely isolated from the DC transmission system, and the multi-station continuous trip signal from the station is not processed; When the converter station is in an effective, connected and operating state, it is considered that the station has been connected to the DC transmission system for operation, and multi-station power coordination instructions are sent to the station and the power coordination instructions from the station are processed.

2. The method for identifying and processing the state of a converter station in a multi-terminal direct current transmission system according to claim 1, characterized in that: When the converter station including the busbar area is in an invalid state, the on-grid / off-grid state of each converter station can be manually set and modified at the operator's workstation.

3. The method for identifying and processing the state of a converter station in a multi-terminal direct current transmission system according to claim 1, characterized in that: In case of abnormal communication between a converter station and a converter station including a busbar busbar area, the line connection status from the busbar busbar area to each converter station detected just before the abnormal communication between the converter stations is locked as the initial status of the on-grid / off-grid status of each converter station. The on-grid / off-grid status of each converter station can be manually set and modified at the operator's workstation.

4. The method for identifying and processing the state of a converter station in a multi-terminal direct current transmission system according to claim 1, characterized in that: When the converter station is in the networked state, the multi-station hopping signal of the station is sent to other converter stations; when the converter station is in the off-grid state, the station does not send the multi-station hopping signal.

5. The method for identifying and processing the state of a converter station in a multi-terminal direct current transmission system according to claim 1, characterized in that: When the converter station is in the connected state, the operation of the DC transmission system needs to consider the equipment status signal of the station.

6. A device for identifying and processing the status of a converter station in a multi-terminal DC transmission system, characterized in that: include: A valid / invalid state identification unit, an online / offline state identification unit, an operating / non-operating state identification unit, and a multi-state processing unit; The function implemented by the effective / ineffective state distinguishing unit is: the enabling setting value of each station is configured through the converter station, if the output is enabled, it is in effective state; if the output is not enabled, it is ineffective state; The function of the on-grid / off-grid state identification unit is: when the DC line from the busbar area to the converter station is connected, the output is an on-grid state; when the DC line from the busbar area to the converter station is not connected, the output is an off-grid state; The function of the operation / non-operation state distinguishing unit is: when the converter station is unlocked, the output is the operation state, and when the converter station is not unlocked, the output is the non-operation state; The multi-state processing unit adjusts the original inter-station communication signals of each station in combination with the results of the valid / invalid state distinguishing unit, the networked / off-grid state distinguishing unit, and the running / non-running state distinguishing unit to generate a processed signal for actual use, and realizes the following functions: when the converter station is in a valid state, all signals from the converter station are received; when the converter station is in an invalid state, no signal from the converter station is received; when the converter station is in a valid and networked state, it is deemed that the station has been or is about to be connected to the DC transmission system for operation, and the multi-station continuous tripping signal from the station is processed; when the converter station is in an off-grid state, it is deemed that the station is completely isolated from the DC transmission system, and the multi-station continuous tripping signal from the station is not processed; when the converter station is in a valid, networked and running state, it is deemed that the station has been connected to the DC transmission system for operation, and a multi-station power coordination instruction is sent to the station and the power coordination instruction from the station is processed.

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