Direct current transmission converter valve active turn-off method and device based on overcurrent detection

Abstract

The invention relates to the technical field of converter valves, in particular to a direct current transmission converter valve active turn-off method and device based on overcurrent detection. Aiming at the conditions that the current cannot be reduced to zero through commutation under an extreme fault and the fault current is relatively large due to a relatively deep fault degree, active turn-off is carried out in the turn-off range of the converter valve, and the fault current is prevented from developing to an unsolved degree.

Description

Technical Field

[0001] The present invention relates to the technical field of converter valves, and in particular to a method and device for actively shutting down a DC power transmission converter valve based on overcurrent detection. Background Art

[0002] High Voltage based Direct Current (HVDC) technology based on thyristor-based line commutated converter (LCC) has become the transmission form with the largest number of actual projects put into operation due to its advantages such as large transmission capacity, no AC grid synchronization problems, and small transmission corridor area. However, LCC-HVDC cannot independently control active and reactive power, does not have black start capability, and there is a risk of commutation failure on the inverter side, which seriously limits the application of LCC-HVDC in the fields of grid-connected transmission of new energy such as wind power and photovoltaic power generation, as well as island power supply.

[0003] Although LCC has the advantages of large transmission capacity and low construction cost, and my country has built dozens of high-voltage direct current transmission projects, LCC uses thyristors as power semiconductor switching devices, and requires an external AC power supply to provide commutation voltage to ensure the normal operation of the converter. The converter has no independence and there is a risk of commutation failure. Once the AC system fails and the voltage drops, commutation failure will occur, causing transmission power fluctuations and even the converter valve to lock and stop DC power transmission. In severe cases, it will cause commutation failures in multiple DC transmission lines of the multi-feed DC system at the same time, seriously threatening the safety of the receiving power grid.

[0004] In order to solve the problem of commutation failure, Tsinghua University proposed a new HCC converter topology based on reverse resistance IGCT. The basic principle of this topology is to replace the thyristor in the traditional LCC converter valve with a high-power reverse resistance IGCT device, and use the high withstand voltage and high current capacity of the reverse resistance IGCT to complete the work of the original thyristor under normal operation, and use the almost negligible reverse recovery period of the reverse resistance IGCT to achieve resistance to commutation failure under minor faults, and use the high current shutdown capability of the reverse resistance IGCT to achieve forced commutation under severe faults. Since the new HCC converter valve based on reverse resistance IGCT has more functions, the original LCC control logic can no longer match the needs of the HCC converter valve, so it is necessary to propose a new control logic for the HCC converter valve.

[0005] In summary, a control method is urgently needed to solve the problem of continuous commutation failure. Summary of the invention

[0006] In response to the above problems, the present invention provides a method and device for actively shutting down a DC transmission converter valve based on overcurrent detection, and proposes an overcurrent shutdown strategy for situations where the current cannot be reduced to zero through phase change under extreme faults and the fault current is large due to the severity of the fault.

[0007] In a first aspect, the present invention provides a method for actively shutting down a DC transmission converter valve based on overcurrent detection, the method comprising:

[0008] The bridge arm current of the converter valve is monitored in real time. When the bridge arm current exceeds the threshold value K, the valve base electronic device VBE of the converter valve sends an active shutdown signal to shut down the converter valve.

[0009] Furthermore, the real-time monitoring of the bridge arm current of the converter valve includes: real-time monitoring of the bridge arm current by means of a bridge arm current sensor disposed in the converter valve.

[0010] Furthermore, the shutdown also includes the following conditions:

[0011] Determine whether the current exceeds the maximum shutoff current of the converter valve device. If it exceeds, the shutdown is not performed.

[0012] Furthermore, the shutdown also includes the following conditions:

[0013] When the energy of the converter valve arrester does not meet the next shutdown requirement, the shutdown will not be performed.

[0014] Furthermore, the shutdown also includes the following conditions:

[0015] When the next bridge arm of the converter valve does not meet the conduction conditions, the shutdown is not performed.

[0016] Furthermore, the threshold K is set according to historical data of the bridge arm current in the converter valve.

[0017] Furthermore, the method also includes: when the bridge arm current exceeds the threshold value K, an alarm message is sent simultaneously, and real-time data of the converter valve is recorded.

[0018] In a second aspect, the present invention provides an active shut-down device for a DC power transmission converter valve based on overcurrent detection, comprising: a monitoring unit and a shut-down unit;

[0019] A monitoring unit, used for real-time monitoring of the bridge arm current of the converter valve;

[0020] The shut-off unit is used to shut down the converter valve by sending an active shut-off signal from VBE when the bridge arm current exceeds the threshold K.

[0021] In a third aspect, the present invention provides an electronic device, comprising a processor, a communication interface, a memory and a communication bus, wherein the processor, the communication interface and the memory communicate with each other via the communication bus;

[0022] Memory, used to store computer programs;

[0023] The processor is used to implement the above-mentioned method for actively shutting down a DC transmission converter valve based on overcurrent detection when executing a program stored in the memory.

[0024] In a fourth aspect, the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the above-mentioned method for actively shutting down a DC transmission converter valve based on overcurrent detection.

[0025] The present invention has at least the following beneficial effects:

[0026] In view of the fact that the current cannot be reduced to zero by phase change under extreme fault conditions and the fault current is large due to the severity of the fault, the present invention actively shuts down the converter valve within the shutoff range to prevent the fault current from developing to an unsolvable level.

[0027] Other features and advantages of the present invention will be described in the following description, and partly become obvious from the description, or be understood by implementing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 This is a flow chart of a shutdown method according to an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of the structure of a shut-off device according to an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of the traditional LCC principle;

[0032] Figure 4 It is a schematic diagram of the overcurrent shutdown principle of the present invention. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] In the prior art, in a traditional LCC converter valve, when an extreme three-phase ground short circuit fault or other fault occurs on the AC side, the fault current often develops rapidly. When entering the commutation window period, the current does not decrease but continues to rise. If the fault is allowed to develop at this time, it may cause continuous commutation failure.

[0035] To this end, the present invention proposes a method and device for actively shutting down a DC transmission converter valve based on overcurrent detection, including a method for actively shutting down a DC transmission converter valve based on overcurrent detection, a device for actively shutting down a DC transmission converter valve based on overcurrent detection, an electronic device and a computer-readable storage medium.

[0036] In view of the fact that the current cannot be reduced to zero by phase change under extreme fault conditions and the fault current is large due to the severity of the fault, the present invention actively shuts down the converter valve within the shutoff range to prevent the fault current from developing to an unsolvable level.

[0037] First, as Figure 1 As shown, the present invention provides a method for actively shutting down a DC transmission converter valve based on overcurrent detection, the method comprising:

[0038] The bridge arm current of the converter valve is monitored in real time. When the bridge arm current exceeds the threshold value K, the valve base electronic device VBE of the converter valve sends an active shutdown signal to shut down the converter valve.

[0039] In specific implementation, the bridge arm current sensor is used to monitor the bridge arm current in real time. When the bridge arm current exceeds a certain threshold, it is considered that a fault has occurred, which will lead to commutation failure. At this time, the VBE sends an active shutdown signal to shut down the converter valve to prevent the fault current from continuing to rise.

[0040] The signal is generated according to the current. The current is measured by the bridge arm current sensor and transmitted to VBE. Then VBE generates a shutdown command after judgment and sends it to the driver of the active switching device. After the driver recognizes the shutdown command, it controls the device to shut down.

[0041] In this embodiment, real-time monitoring of the bridge arm current of the converter valve includes: real-time monitoring of the bridge arm current by means of a bridge arm current sensor disposed in the converter valve.

[0042] In specific implementation, a bridge arm current sensor or other sensors capable of monitoring the bridge arm current are used to monitor the bridge arm current in real time. The sensor can be arranged inside the converter valve or outside the converter valve and connected via a wire.

[0043] In this embodiment, the shutdown also includes the following conditions:

[0044] Determine whether the current exceeds the maximum shutoff current of the converter valve device. If so, do not shut down.

[0045] In a specific implementation, if the current exceeds the maximum switchable current of the bridge arm of the converter valve or the active switch device, the shutdown is not performed.

[0046] In this embodiment, the shutdown also includes the following conditions:

[0047] When the energy of the converter valve arrester does not meet the next shutdown requirement, the shutdown will not be performed.

[0048] In this embodiment, the shutdown also includes the following conditions:

[0049] When the next bridge arm of the converter valve does not meet the conduction conditions, the shutdown is not performed.

[0050] In this embodiment, the threshold K is set according to the historical data of the bridge arm current in the converter valve.

[0051] In this embodiment, the method further includes: when the bridge arm current exceeds the threshold value K, an alarm message is sent simultaneously, and real-time data of the converter valve is recorded.

[0052] During specific implementation, the real-time data of the converter valve is recorded for subsequent tracking and analysis to understand the cause and mechanism and make improvements.

[0053] Second, as Figure 2 As shown, the present invention provides an active shut-down device for a DC power transmission converter valve based on overcurrent detection, comprising: a monitoring unit and a shut-down unit;

[0054] A monitoring unit, used for real-time monitoring of the bridge arm current of the converter valve;

[0055] The shut-off unit is used to shut down the converter valve by sending an active shut-off signal from VBE when the bridge arm current exceeds the threshold K.

[0056] In specific implementation, the implementation processes of the DC transmission converter valve active shutdown device based on overcurrent detection and the DC transmission converter valve active shutdown method based on overcurrent detection of the present invention correspond one to one, and will not be repeated here.

[0057] In a third aspect, the present invention provides an electronic device, comprising a processor, a communication interface, a memory and a communication bus, wherein the processor, the communication interface and the memory communicate with each other via the communication bus;

[0058] Memory, used to store computer programs;

[0059] The processor is used to implement the above-mentioned method for actively shutting down a DC transmission converter valve based on overcurrent detection when executing a program stored in the memory.

[0060] In a fourth aspect, the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the above-mentioned method for actively shutting down a DC transmission converter valve based on overcurrent detection.

[0061] The computer-readable storage medium may be included in the device / apparatus described in the above embodiment; or it may exist independently without being assembled into the device / apparatus. The above computer-readable storage medium carries one or more programs, and when the above one or more programs are executed, the method according to the embodiment of the present disclosure is implemented.

[0062] According to an embodiment of the present disclosure, a computer-readable storage medium may be a non-volatile computer-readable storage medium, for example, may include but is not limited to: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof. In the present disclosure, a computer-readable storage medium may be any tangible medium containing or storing a program that may be used by or in conjunction with an instruction execution system, apparatus, or device.

[0063] The computer-readable storage medium may also be a readable storage medium such as a single-chip microcomputer or an MCU, which has the same principle as a computer.

[0064] In order to enable those skilled in the art to better understand the present invention, the principle of the present invention is described as follows in conjunction with the accompanying drawings:

[0065] In order to solve the problem of commutation failure, Tsinghua University proposed a new HCC converter topology based on reverse-resistance IGCT. The basic principle of this topology is to replace the thyristor in the traditional LCC converter valve with a high-power reverse-resistance IGCT device, and use the high withstand voltage and high current capacity of the reverse-resistance IGCT to complete the work of the original thyristor under normal operation, and use the almost negligible reverse recovery period of the reverse-resistance IGCT to achieve resistance to commutation failure under minor faults, and use the high current shutdown capability of the reverse-resistance IGCT to achieve forced commutation under severe faults. Since the new HCC converter valve based on reverse-resistance IGCT has more functions, the original LCC control logic can no longer match the requirements of the HCC converter valve, so it is necessary to propose a new control logic for the HCC converter valve. The present invention proposes an overcurrent shutdown strategy for the situation where the current cannot be reduced to zero through commutation under extreme faults, and the fault current is large due to the deep fault.

[0066] In a traditional LCC converter valve, when an extreme three-phase ground short circuit fault or other fault occurs on the AC side, the fault current often develops rapidly. When entering the commutation window period, the current does not decrease, but continues to rise. If the fault is allowed to develop at this time, it may cause continuous commutation failure. Therefore, the present invention proposes an HCC active shutdown strategy based on overcurrent detection. The principle is to use a bridge arm current sensor to monitor the bridge arm current in real time. When the bridge arm current exceeds a certain threshold, it is considered that a fault has occurred, which will lead to commutation failure. At this time, the VBE sends an active shutdown signal to shut down the converter valve to prevent the fault current from continuing to rise.

[0067] The control strategy proposed in this invention is aimed at the condition where the DC current continues to rise under extreme fault conditions of the AC system. When such a fault occurs, the current starts to rise, such as Figure 3 As shown in Figure 1, if it is not controlled, the current will rise to a level that cannot be turned off, causing multiple consecutive commutation failures. Figure 4The present invention provides a solution strategy, namely, an overcurrent detection active shutdown strategy. In this strategy, in order to achieve active shutdown, it is necessary to replace the device from a semi-controlled device thyristor with an active switching device, such as IGCT, IGBT, GTO, IEGT, IETO, MOSFET, etc. After the valve-controlled VBE begins to enter the shutdown interval, it starts to detect the current. When the current exceeds the preset value, a shutdown command is issued to the active switching device, and then the device executes the active shutdown command to force the current to commutate to the next conducting bridge arm. It should be noted that the shutdown strategy is affected by the enable signal. The enable signal includes the following points: 1. Determine whether the current exceeds the maximum shutdown current of the device. If it exceeds, the shutdown is not executed; 2. When the arrester energy does not meet the next shutdown, the shutdown is not executed; 3. When the next bridge arm does not meet the conduction conditions, the shutdown is not executed. The signal of this strategy is generated according to the current. The current is measured by the bridge arm current sensor and transmitted to VBE. Then VBE generates a shutdown command after judgment and sends it to the driver of the active switching device. After the driver recognizes the shutdown command, it controls the device to shut down.

[0068] In view of the fact that the current cannot be reduced to zero by phase change under extreme fault conditions and the fault current is large due to the severity of the fault, the present invention actively shuts down the converter valve within the shutoff range to prevent the fault current from developing to an unsolvable level.

[0069] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for actively shutting down a DC power transmission converter valve based on overcurrent detection, characterized in that: The method comprises: The bridge arm current of the converter valve is monitored in real time. When the bridge arm current exceeds the threshold value K, the valve base electronic device VBE of the converter valve sends an active shutdown signal to shut down the converter valve.

2. The method for actively shutting down a DC power transmission converter valve based on overcurrent detection according to claim 1, characterized in that: Real-time monitoring of the bridge arm current of the converter valve includes: real-time monitoring of the bridge arm current by a bridge arm current sensor arranged in the converter valve.

3. The method for actively shutting down a DC power transmission converter valve based on overcurrent detection according to claim 1, characterized in that: Shut down These include the following conditions: Determine whether the current exceeds the maximum shutoff current of the converter valve device. If so, do not shut down.

4. The method for actively shutting down a DC power transmission converter valve based on overcurrent detection according to claim 1, characterized in that: Shut down These include the following conditions: When the energy of the converter valve arrester does not meet the next shutdown requirement, the shutdown will not be performed.

5. The method for actively shutting down a DC power transmission converter valve based on overcurrent detection according to claim 1, characterized in that: Shut down These include the following conditions: When the next bridge arm of the converter valve does not meet the conduction conditions, the shutdown is not performed.

6. The method for actively shutting down a DC power transmission converter valve based on overcurrent detection according to claim 1, characterized in that: The threshold K is set according to the historical data of the bridge arm current in the converter valve.

7. The method for actively shutting down a DC power transmission converter valve based on overcurrent detection according to any one of claims 1 to 6, characterized in that: The method also includes: when the bridge arm current exceeds the threshold value K, an alarm message is sent simultaneously, and real-time data of the converter valve is recorded.

8. An active shutdown device for a DC power transmission converter valve based on overcurrent detection, characterized in that: include: Monitoring unit and shutdown unit; A monitoring unit, used for real-time monitoring of the bridge arm current of the converter valve; The shut-off unit is used to shut down the converter valve by sending an active shut-off signal from VBE when the bridge arm current exceeds the threshold K.

9. An electronic device, characterized in that: It includes a processor, a communication interface, a memory and a communication bus, wherein the processor, the communication interface and the memory communicate with each other through the communication bus; Memory, used to store computer programs; The processor is used to implement the method for actively shutting down a DC transmission converter valve based on overcurrent detection as described in any one of claims 1 to 7 when executing a program stored in the memory.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method for actively shutting down a DC transmission converter valve based on overcurrent detection according to any one of claims 1 to 7 is implemented.

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