Fault isolation method, device and equipment for suppressing over-current of bridge arm of direct-current power transmission system

Abstract

The invention discloses a fault isolation method, device and equipment for inhibiting over-current of a bridge arm of a direct current transmission system, and the method comprises the steps: according to the control signal direction of each converter in each converter station, when a certain converter is judged to meet a rapid current-limiting control signal enabling state within a period of time from the fault occurrence in a polar region to the protection action, the current-limiting control signal enabling state is switched to the current-limiting control signal enabling state; setting a minimum direct current voltage value capable of being output by the converter as a current direct current voltage bias value; obtaining a difference value between the measured value of the neutral current and the current limiting reference value of the converter, and updating the direct-current voltage bias value to be the difference value; and after protection action, all the current converters of the fault direct current pole are locked, the switch trips off, and fault isolation is completed. According to the DC electric quantity characteristics of each converter station, the DC pole fault is discriminated, the fault current within a period of time from the occurrence of the fault in the pole area to the protection action is limited, and the magnitude of the fault current and the discharge capacity of the sub-module capacitor are reduced, so that the drop degree of the sub-module voltage is reduced, and the impact of the fault on the system is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of DC power transmission, and particularly relates to a fault isolation method, device and equipment for suppressing arm overcurrent in a DC power transmission system. Background Art

[0002] In a DC power transmission system, generally when a fault occurs on the non-line side of a pole region, in order to enable the protection to quickly respond to the fault electrical characteristic quantity and issue a converter locking and tripping instruction, usually no measures are taken before the protection action, and the fault current is allowed to develop freely. However, in a converter station using a modular multilevel converter valve (MMC) (i.e., a flexible DC converter station), when encountering such a fault, the sub-module capacitor will experience excessive discharge. Moreover, during the period from the converter valve locking to the AC switch tripping, the AC voltage will still charge the converter valve. For a small-capacity converter valve, when a fault occurs in the pole region, the discharge amount of the sub-module capacitor is limited, so the fault current is small, and the voltage drop of the sub-module capacitor value is not obvious. In this way, after the converter valve is locked, the charging current from the AC side is also correspondingly small, and it is difficult to have an arm overcurrent situation. In contrast, the voltage drop of the sub-module capacitor of a large-capacity converter valve during a fault is greater. Once the converter valve is locked, the charging current from the AC side to the sub-module will also increase correspondingly, which is likely to cause an arm overcurrent problem, leading to the fault bypass of the sub-module, not only increasing the risk of equipment damage but also prolonging the recovery time of the entire DC system.

[0003] In order to prevent the occurrence of arm overcurrent in a flexible DC converter station after a fault lockout, it is necessary to study the control strategy before the protection action lockout, and this case is thus generated. Summary of the Invention

[0004] The purpose of the present invention is to provide a fault isolation method, device and equipment for suppressing arm overcurrent in a DC power transmission system, aiming to solve the problem of arm overcurrent in a flexible DC converter station after a fault lockout in the prior art.

[0005] To achieve the above purpose, the solution of the present invention is:

[0006] A fault isolation method for suppressing arm overcurrent in a DC power transmission system includes:

[0007] Obtain the control signal directions of each converter in each converter station;

[0008] According to the control signal directions of each converter, within a period of time from the occurrence of a fault in the pole region to the protection action, when it is determined that a certain converter satisfies the enabled state of the fast current limiting control signal, set the minimum DC voltage value that the converter can output as the current DC voltage offset value;

[0009] Obtain the difference between the measured value of the neutral line current and the converter current limiting reference value, and update the DC voltage bias value to the difference;

[0010] After the protection action, block all converters of the faulty DC pole, trip the switch, and complete the fault isolation.

[0011] Among them, obtaining the control signal directions of each converter in each converter station includes,

[0012] Obtain the measured value direction and change rate direction of the pole bus current of this station;

[0013] Obtain the measured value direction and change rate direction of the neutral line current of this station;

[0014] Obtain the change rate direction of the voltages at both ends of the DC side of each converter of this station.

[0015] Among them, judging that a certain converter meets the fast current limiting control signal enabling state according to the control signal directions of the converters includes,

[0016] Each converter of this station judges that the converter meets the fast current limiting control signal enabling state in response to the measured value direction and change rate direction of the pole bus current being the same, the measured value direction and change rate direction of the neutral line current being the same, and the change rate direction of the voltages at both ends of the DC side of the converter being negative.

[0017] Among them,

[0018] When the measured value direction of the pole bus current or the neutral line current is the same as the defined positive current direction, it is positive, otherwise it is negative;

[0019] Define the positive direction of the DC side current of the sending converter station as flowing out of the converter, and the positive direction of the DC side current of the receiving converter station as flowing into the converter;

[0020] When the pole bus current, the neutral line current, and the voltages at both ends of the DC side of the converter increase, the change rate direction is positive; when they decrease, the change rate direction is negative.

[0021] In a second aspect, the present invention provides a fault isolation device for suppressing arm overcurrent in a DC power transmission system, including,

[0022] An acquisition unit configured to obtain the control signal directions of each converter in each converter station;

[0023] An enabling discrimination unit configured to judge whether each converter meets the fast current limiting control signal enabling state according to the control signal directions of the converters; and,

[0024] The current limiting control unit is configured to set the minimum DC voltage value that the converter can output as the current DC voltage offset value within a period of time from the occurrence of a fault in the pole region to the protection action, and update the DC voltage offset value based on the difference between the measured value of the neutral line current and the current limiting reference value of the converter.

[0025] Among them, the acquisition unit obtains the control signal directions of each converter in each converter station, including

[0026] obtaining the direction of the measured value and the change rate direction of the pole bus current of this station;

[0027] obtaining the direction of the measured value and the change rate direction of the neutral line current of this station;

[0028] obtaining the change rate direction of the voltages at both ends of the DC side of each converter of this station.

[0029] Among them, the enabling discrimination unit determines that a certain converter satisfies the enabling state of the fast current limiting control signal according to the control signal directions of the converters, including

[0030] Each converter of this station determines that the converter satisfies the enabling state of the fast current limiting control signal in response to the same direction of the measured value and the change rate direction of the pole bus current, the same direction of the measured value and the change rate direction of the neutral line current, and the negative change rate direction of the voltages at both ends of the DC side of the converter.

[0031] Among them, the enabling discrimination unit further includes

[0032] When the direction of the measured value of the pole bus current or the neutral line current is the same as the defined positive direction of the current, it is positive, otherwise it is negative;

[0033] It is defined that the DC side current flowing out of the converter in the sending converter station is the positive direction, and the DC side current flowing into the converter in the receiving converter station is the positive direction;

[0034] When the pole bus current, the neutral line current, and the voltage values at both ends of the DC side of the converter increase, the change rate direction is positive; when they decrease, the change rate direction is negative.

[0035] In a third aspect, the present invention provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor; when the processor executes the computer program, the fault isolation method for suppressing arm overcurrent in the DC power transmission system as described above is implemented.

[0036] In a fourth aspect, the present invention provides a computer-readable storage medium, and the computer-readable storage medium stores a computer program; when the computer program is executed by a processor, the fault isolation method for suppressing arm overcurrent in the DC power transmission system as described above is implemented.

[0037] After adopting the above solution, the present invention first obtains the DC electrical quantities of each converter station, determines whether each converter of the converter station meets the discrimination conditions for DC pole faults according to the direction characteristics of the electrical quantities, enables the current limiting control logic when the discrimination conditions are met, limits the fault current during a period from the occurrence of a fault in the pole area to before the protection action, and after the DC pole protection action, blocks all converters of the faulty DC pole, and the switch trips to complete fault isolation.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0039] (1) By obtaining the DC electrical quantities of each converter station and determining whether each converter of the converter station meets the discrimination conditions for DC pole faults according to the characteristics of the electrical quantities, the present invention enables the current limiting control logic when the discrimination conditions are met, limits the fault current during a period from the occurrence of a fault in the pole area to before the protection action, reduces the magnitude of the fault current and the discharge amount of the sub-module capacitor during the period from the occurrence of the fault to the protection action, thereby reducing the degree of voltage drop of the sub-module, alleviating the impact of the fault on the system, and improving the reliability and stability of the system;

[0040] After the DC pole protection action, all converters of the faulty DC pole are blocked, and the switch trips to complete fault isolation. During the period from the blocking of the converter valve to the complete tripping of the switch, the AC side still charges the converter valve. Due to the above-mentioned current limiting strategy after the fault, the voltage value of the sub-module capacitor drops less, the charging current of the AC side to the sub-module continues to be small, and there is no problem of overcurrent in the bridge arm, thereby reducing the risk of damage to the sub-module.

[0041] (2) After the DC pole protection action, the present invention blocks all converters of the faulty DC pole, and the switch trips to complete fault isolation; during the period from the blocking of the converter valve to the complete tripping of the switch, the AC side still charges the converter valve. Due to the above-mentioned current limiting strategy after the fault, the voltage value of the sub-module capacitor drops less, the charging current of the AC side to the sub-module continues to be small, and there is no problem of overcurrent in the bridge arm, thereby reducing the risk of damage to the sub-module;

[0042] (3) The protection action time of the present invention is in milliseconds, while the control response period is in microseconds. It can ensure the correctness of the protection action while suppressing the fault current, and the implementation difficulty is low. Therefore, it has high engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is a topological schematic diagram of the present invention with both sending and receiving ends and a single station containing one or more MMC type converters operating in series;

[0044] Figure 2 is an overall flow schematic diagram of the fault isolation method for suppressing overcurrent in the bridge arm of the DC power transmission system of the present invention;

[0045] Figure 3 It is a schematic diagram of the module of the fault isolation device for suppressing arm overcurrent in the DC transmission system provided by the embodiment of the present invention. Specific embodiments

[0046] The technical solutions and beneficial effects of the present invention will be described in detail below in conjunction with the accompanying drawings.

[0047] The present invention provides a fault isolation method for suppressing arm overcurrent in a DC transmission system. The DC transmission system includes at least one DC pole, and the DC pole includes a sending-end power grid, an MMC-type sending-end converter station DC pole, a DC line, an MMC-type receiving-end converter station DC pole, and a receiving-end power grid connected in series. The MMC-type converter station DC pole includes at least one MMC-type converter; the fault isolation method for suppressing arm overcurrent includes,

[0048] Obtain the control signal directions of each converter in each converter station;

[0049] According to the control signal directions of each converter, within a period of time from the occurrence of a fault in the pole area to the protection action, when it is judged that a certain converter meets the enabling state of the fast current limiting control signal, set the minimum DC voltage value that the converter can output as the current DC voltage offset value; wherein, the DC voltage offset value is the expected value of the DC voltage output by the converter;

[0050] Obtain the difference between the measured value of the neutral line current and the current limiting reference value of the converter, and update the DC voltage offset value to the difference;

[0051] After the protection action, block all converters of the faulty DC pole, open the switch, and the fault isolation is completed.

[0052] Among them, obtaining the control signal directions of each converter in each converter station includes,

[0053] Obtain the measured value direction and the change rate direction of the pole bus current of this station;

[0054] Obtain the measured value direction and the change rate direction of the neutral line current of this station;

[0055] Obtain the change rate direction of the voltage across both ends of the DC side of each converter of this station.

[0056] Among them, according to the control signal directions of each converter, judging that a certain converter meets the enabling state of the fast current limiting control signal includes,

[0057] Each converter of this station judges that the converter meets the enabling state of the fast current limiting control signal in response to the measured value direction and the change rate direction of the pole bus current being consistent, the measured value direction and the change rate direction of the neutral line current being consistent, and the change rate direction of the voltage across both ends of the DC side of the converter being negative.

[0058] Among them,

[0059] When the direction of the measured value of the pole bus current or the neutral line current is the same as the defined positive direction of the current, it is positive; otherwise, it is negative.

[0060] It is defined that the positive direction of the DC side current of the sending-end converter station flows out of the converter, and the positive direction of the DC side current of the receiving-end converter station flows into the converter.

[0061] When the pole bus current, the neutral line current, and the voltage values at both ends of the DC side of the converter increase, the direction of the rate of change is positive; when they decrease, the direction of the rate of change is negative.

[0062] Please refer to Figure 1 , the embodiment of the present invention provides a DC power transmission system, specifically a flexible DC power transmission system. The flexible DC power transmission system includes a DC pole. The DC pole includes a sending-end power grid, an MMC-type sending-end converter station DC pole, a DC line, an MMC-type receiving-end converter station DC pole, and a receiving-end power grid connected in series. The MMC-type converter station DC pole includes N MMC-type converters, where N≥1 and N is a positive integer. The MMC-type sending-end converter station is a DC power control station, and the receiving-end converter station is a DC voltage control station. The alternating current of the sending-end power grid is rectified by the sending-end converter station and then becomes direct current. This direct current is transmitted to the DC pole of the receiving-end converter station of the flexible DC power transmission system through the DC line between the DC pole of the sending-end converter station of the flexible DC power transmission system and the DC pole of the receiving-end converter station of the flexible DC power transmission system. The DC pole of the receiving-end converter station converts the received direct current into alternating current and finally transmits it to the receiving-end power grid.

[0063] Correspondingly, please refer to Figure 2 , Figure 2 schematically shows the overall process of a fault isolation method for suppressing arm overcurrent in a DC power transmission system provided by an embodiment of the present invention, including the following steps:

[0064] 201. Each station's converter continuously judges the enabling state of the fast current limiting control signal of the DC power transmission system;

[0065] 202. If the converter meets the enabling state of the fast current limiting control signal, step the DC voltage offset value of the converter to the lower limit value;

[0066] 203. Obtain the measured value of the neutral line current and the current limiting reference value of the converter;

[0067] 204. Subtract the measured value of the neutral line current from the current limiting reference value of the converter and input the result into the current limiting controller of the converter for closed-loop control. The output of the current limiting controller is used as the new DC voltage offset value;

[0068] 205. After the protection action, block all converters of the faulty DC pole, open the switch, and complete the fault isolation.

[0069] In some embodiments, the fault isolation method for suppressing arm overcurrent in the DC power transmission system provided by the embodiments of the present invention specifically includes:

[0070] When a fault occurs in the pole region and before the DC pole protection acts to trip and block, obtain the measured value IDL of the pole bus current of the sending converter station _S1 , the rate of change of the pole bus current ΔIDL _S1 , the measured value IDNC of the neutral line current _S1 , the rate of change of the neutral line current ΔIDNC _S1 , the measured values Udvn of the voltages at both ends of the DC side of each converter _S1 , the rate of change of the voltage at both ends of the DC side ΔUdvn _S1 , where 1 ≤ n ≤ N and n is a positive integer; obtain the measured value IDL of the pole bus current of the receiving converter station _S2 , the rate of change of the pole bus current ΔIDL _S2 , the measured value IDNC of the neutral line current _S2 , the rate of change of the neutral line current ΔIDNC _S2 , the measured values Udvn of the voltages at both ends of the DC side of each converter _S2 , the rate of change of the voltage at both ends of the DC side ΔUdvn _S2 ; define the positive direction as the current flowing out of the converter on the DC side of the sending converter station, and the positive direction as the current flowing into the converter on the DC side of the receiving converter station;

[0071] Judge in real time whether the enabling state of the fast current limiting control signal of the DC power transmission system is satisfied; the discrimination conditions satisfied by each converter of the sending converter station are that the measured value IDL of the pole bus current of the sending converter station _S1 and the rate of change of the pole bus current ΔIDL _S1 are in the same direction and both are negative directions, that is, IDL _S1 < 0, ΔIDL _S1 < 0; the measured value IDNC of the neutral line current _S1 and the rate of change of the neutral line current ΔIDNC _S1 are in the same direction and both are positive directions, that is, IDNC _S1 > 0, ΔIDNC _S1 > 0; the rate of change of the voltage at both ends of the DC side of the converter ΔUdvn _S1 is a negative direction, that is, ΔUdvn _S1 < 0; the discrimination conditions satisfied by each converter of the receiving converter station are that the measured value IDL of the pole bus current of the sending converter station _S2 and the rate of change of the pole bus current ΔIDL _S2 are in the same direction and both are positive directions, that is, IDL _S2 > 0, ΔIDL _S2 > 0; the measured value IDNC of the neutral line current_S2 and the neutral line current change rate ΔIDNC _S2 are in the same direction and both are in the negative direction, that is, IDNC _S2 < 0, ΔIDNC _S2 < 0; the voltage change rate ΔUdvn at both ends of the DC side of the converter _S2 is in the negative direction, that is, ΔUdvn _S2 < 0;

[0072] When the converters of each station respond to the electrical quantities on the DC side to meet the discrimination conditions, the current limiting control signal is enabled, otherwise it is not enabled; when the current limiting control signal is enabled, the DC voltage offset value of the converter is stepped to the lower limit value; the measured value of the neutral line current and the current limiting reference value of the converter are obtained; the difference between the measured value of the neutral line current and the current limiting reference value of the converter is input to the current limiting controller of the converter for closed-loop control, and the output of the current limiting controller is used as the new DC voltage offset value; after the DC pole protection operates, all the converters of the faulty DC pole are blocked, the switch trips, and the fault isolation is completed.

[0073] In some embodiments, the current limiting reference value of the converter is greater than the pole bus differential protection setting value; the content of the pole bus differential protection is: calculating the differential current between the valve group pole line current IDCP and the pole line current IDL; when the differential current is greater than a certain multiple of the maximum value of the valve group pole line current IDCP and the pole line current IDL, the I-section protection operates; when the differential current is greater than a certain multiple of the maximum value of the valve group pole line current IDCP and the pole line current IDL and the pole line voltage UDL is less than the setting value, the II-section protection operates.

[0074] The present invention also provides a fault isolation device for suppressing arm overcurrent in a DC power transmission system. The DC power transmission system includes at least one DC pole, and the DC pole includes a sending-end power grid, an MMC-type sending-end converter station DC pole, a DC line, an MMC-type receiving-end converter station DC pole, and a receiving-end power grid connected in series. The MMC-type converter station DC pole includes at least one MMC-type converter; the fault isolation device for suppressing arm overcurrent includes,

[0075] An acquisition unit configured to obtain the control signal directions of the converters in each converter station;

[0076] An enabling discrimination unit configured to determine whether each converter meets the enabling state of the fast current limiting control signal according to the control signal directions of the converters; and,

[0077] A current limiting control unit configured to set the minimum DC voltage value that the converter can output as the current DC voltage offset value within a period of time from the occurrence of a fault in the pole area to the operation of the protection, and update the DC voltage offset value based on the difference between the measured value of the neutral line current and the current limiting reference value of the converter.

[0078] Among them, the acquisition unit obtains the control signal directions of each converter in each converter station, including

[0079] obtaining the measured value direction and the change rate direction of the pole bus current of this station;

[0080] obtaining the measured value direction and the change rate direction of the neutral line current of this station;

[0081] obtaining the change rate direction of the voltages at both ends of the DC side of each converter of this station.

[0082] Among them, the enabling discrimination unit determines that a certain converter meets the enabling state of the fast current limiting control signal according to the control signal directions of the converters, including

[0083] Each converter of this station determines that the converter meets the enabling state of the fast current limiting control signal in response to the same direction of the measured value direction and the change rate direction of the pole bus current, the same direction of the measured value direction and the change rate direction of the neutral line current, and the negative change rate direction of the voltages at both ends of the DC side of the converter.

[0084] Among them, the enabling discrimination unit further includes

[0085] When the measured value direction of the pole bus current or the neutral line current is consistent with the defined positive direction of the current, it is positive; otherwise, it is negative;

[0086] Define the positive direction of the DC side current of the sending converter station flowing out of the converter, and the positive direction of the DC side current of the receiving converter station flowing into the converter;

[0087] When the pole bus current, the neutral line current, and the voltage values at both ends of the DC side of the converter increase, the change rate direction is positive; when they decrease, the change rate direction is negative.

[0088] Correspondingly, please refer to Figure 3 , the module schematic diagram of the fault isolation device for suppressing arm overcurrent in the DC power transmission system provided by the embodiment of the present invention, which is used to execute the fault isolation method for suppressing arm overcurrent in the DC power transmission system provided by the embodiment of the present invention. The fault isolation device for suppressing arm overcurrent includes:

[0089] The first module 10, the first module 10 is configured as an acquisition unit, and is used to obtain the measured value and the change rate of the pole bus current of this station; the measured value IDL of the pole bus current of the sending converter station _S1 , the change rate ΔIDL of the pole bus current _S1 , the measured value IDNC of the neutral line current _S1 , the change rate ΔIDNC of the neutral line current _S1 , the measured value U of the voltages at both ends of the DC side of each converter dvn_S1 , the change rate ΔU of the voltages at both ends of the DC side dvn_S1, where 1 ≤ n ≤ N and n is a positive integer; obtain the measured value IDL of the pole bus current of the receiving-end converter station _S2 , the rate of change of the pole bus current ΔIDL _S2 , the measured value IDNC of the neutral line current _S2 , the rate of change of the neutral line current ΔIDNC _S2 , the measured value U of the voltage at both ends of the DC side of each converter dvn_S2 , the rate of change of the voltage at both ends of the DC side ΔU dvn_S2 ;

[0090] The second module 20 is configured to enable the discrimination unit to determine in real time whether the enabling state of the fast current limiting control signal of the DC transmission system is satisfied; the discrimination conditions satisfied by each converter of the sending-end converter station are that the measured value IDL of the pole bus current of the sending-end converter station _S1 and the rate of change of the pole bus current ΔIDL _S1 are in the same direction and both are in the negative direction, that is, IDL _S1 <0, ΔIDL _S1 <0; the measured value IDNC of the neutral line current _S1 and the rate of change of the neutral line current ΔIDNC _S1 are in the same direction and both are in the positive direction, that is, IDNC _S1 >0, ΔIDNC _S1 >0; the rate of change of the voltage ΔU at both ends of the DC side of the converter dvn_S1 is in the negative direction, that is, ΔU dvn_S1 <0; the discrimination conditions satisfied by each converter of the receiving-end converter station are that the measured value IDL of the pole bus current of the sending-end converter station _S2 and the rate of change of the pole bus current ΔIDL _S2 are in the same direction and both are in the positive direction, that is, IDL _S2 >0, ΔIDL _S2 >0; the measured value IDNC of the neutral line current _S2 and the rate of change of the neutral line current ΔIDNC _S2 are in the same direction and both are in the negative direction, that is, IDNC _S2 <0, ΔIDNC _S2 <0; the rate of change of the voltage ΔU at both ends of the DC side of the converter dvn_S2 is in the negative direction, that is, ΔU dvn_S2 <0;

[0091] The third module 30, the second module 30 is configured as a current limiting control unit, which is used to limit the fault current during a period of time from when a fault occurs in the pole region to before the protection action, and step the DC voltage offset value of the converter to the lower limit value; obtain the measured value of the neutral line current and the current limiting reference value of the converter; subtract the measured value of the neutral line current from the current limiting reference value of the converter and input it into the current limiting controller of the converter for closed-loop control, and the output of the current limiting controller is used as the new DC voltage offset value.

[0092] An embodiment of the present invention also provides another computer device, including a processor and a memory configured to store a computer program that can run on the processor; wherein, when the processor is configured to run the computer program, it executes the fault isolation method for suppressing arm overcurrent in the DC power transmission system provided by the embodiment of the present invention.

[0093] In practical applications, the above-mentioned processor includes a Field-Programmable Gate Array (FPGA), and the processor can be a Central Processing Unit (CPU) or a Digital Signal Processor (DSP, Digital Signal Processing). It can be understood that for different devices, the electronic devices used to implement the functions of the above-mentioned processor can also be others, and the embodiments of the present invention do not make specific limitations.

[0094] The above-mentioned memory can be a volatile memory, such as a Random-Access Memory (RAM); or a non-volatile memory, such as a Read-Only Memory (ROM), a flash memory, a Hard Disk Drive (HDD), or a Solid-State Drive (SSD); or a combination of the above types of memories, and provides instructions and data to the processor.

[0095] Correspondingly, an embodiment of the present invention also provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is run by a processor, it executes the fault isolation method for suppressing arm overcurrent in the DC power transmission system provided by the embodiment of the present invention.

[0096] In several embodiments provided by the present invention, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are merely illustrative. For example, the division of the units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined, or can be integrated into another system, or some features can be ignored, or not executed. In addition, the couplings between the various components shown or discussed, or direct couplings, or communication connections can be through some interfaces. The indirect couplings or communication connections of devices or units can be electrical, mechanical, or other forms.

[0097] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code. The solutions in the embodiments of the present invention can be implemented using various computer languages. For example, object-oriented programming languages such as Java and interpreted scripting languages such as JavaScript.

[0098] The present invention is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to the embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, and the combination of flows and / or blocks in the flowchart and / or block diagram, can be realized by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for realizing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0099] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device, and the instruction device realizes the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0100] These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus, such that a series of operation steps are performed on the computer or other programmable apparatus to produce a computer-implemented process, so that the instructions executed on the computer or other programmable apparatus provide steps for implementing the functions specified in one process Figure 1 one process or more processes and / or blocks Figure 1 or steps for implementing the functions specified in a block or more blocks.

[0101] Although the preferred embodiments of the present invention have been described, additional changes and modifications can be made by those skilled in the art once they learn of the basic creative concept. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0102] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A fault isolation method for suppressing overcurrent in a bridge arm of a direct current transmission system, characterized in that: The fault isolation method for suppressing bridge arm overcurrent includes: Obtaining the control signal direction of each converter in each converter station; According to the control signal direction of each converter, during a period from when a fault occurs in the polar area to before the protection action, when it is determined that a converter meets the fast current limiting control signal enabling state, the minimum DC voltage value that the converter can output is set to the current DC voltage bias value; Obtaining a difference between the measured value of the neutral line current and the converter current limiting reference value according to the measured value of the neutral line current and updating the DC voltage bias value to the difference; After the protection is activated, all converters of the faulty DC pole are locked, the switch is tripped, and the fault isolation is completed.

2. The method according to claim 1, characterized in that: Obtain the control signal direction of each converter in each converter station, including: Obtain the measured value direction and change rate direction of the busbar current at this station; Obtain the measured value direction and change rate direction of the neutral line current of this station; Obtain the direction of the rate of change of the voltage at both ends of the DC side of each converter in this station.

3. The method according to claim 2, characterized in that: According to the directions of the control signals of the converters, judging whether a converter satisfies the enabling state of the fast current limiting control signal includes: The converters in this station respond to the fact that the measured values ​​and change rates of the pole bus current are consistent in direction, the measured values ​​and change rates of the neutral current are consistent in direction, and the change rate of the voltage at both ends of the DC side of the converter is negative, and it is judged that the converter meets the fast current limiting control signal enable state.

4. The method according to claim 2, characterized in that: When the direction of the measured value of the pole bus current or neutral current is consistent with the defined positive direction of the current, it is positive, otherwise it is negative; The positive direction is defined as the current flowing out of the converter at the DC side of the sending-end converter station, and the positive direction is defined as the current flowing into the converter at the DC side of the receiving-end converter station; When the pole bus current, neutral line current and voltage across the DC side of the converter increase, the direction of the rate of change is positive; when they decrease, the direction of the rate of change is negative.

5. A fault isolation device for suppressing overcurrent in a bridge arm of a direct current transmission system, characterized in that: The fault isolation device for suppressing overcurrent of the bridge arm comprises: A collection unit configured to obtain the direction of the control signal of each converter in each converter station; an enabling determination unit, configured to determine whether each converter satisfies the enabling state of the fast current limiting control signal according to the direction of the control signal of each converter; and The current limiting control unit is configured to set the minimum DC voltage value that the converter can output as the current DC voltage bias value during the period from the occurrence of a fault in the polar area to the protection action, and to update the DC voltage bias value based on the difference between the measured value of the neutral line current and the converter current limiting reference value.

6. The device according to claim 5, characterized in that: The acquisition unit obtains the control signal direction of each converter in each converter station, including: Obtain the measured value direction and change rate direction of the busbar current at this station; Obtain the measured value direction and change rate direction of the neutral line current of this station; Obtain the direction of the rate of change of the voltage at both ends of the DC side of each converter in this station.

7. The device according to claim 6, characterized in that: The enabling determination unit determines, according to the directions of the control signals of the converters, whether a converter satisfies the enabling state of the fast current limiting control signal, including: The converters in this station respond to the fact that the measured values ​​and change rates of the pole bus current are consistent in direction, the measured values ​​and change rates of the neutral current are consistent in direction, and the change rate of the voltage at both ends of the DC side of the converter is negative, and it is judged that the converter meets the fast current limiting control signal enable state.

8. The device according to claim 6, characterized in that: The enabling determination unit also includes: When the direction of the measured value of the pole bus current or neutral current is consistent with the defined positive direction of the current, it is positive, otherwise it is negative; The positive direction is defined as the current flowing out of the converter at the DC side of the sending-end converter station, and the positive direction is defined as the current flowing into the converter at the DC side of the receiving-end converter station; When the pole bus current, neutral line current and voltage across the DC side of the converter increase, the direction of the rate of change is positive; when they decrease, the direction of the rate of change is negative.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor; characterized in that: When the processor executes the computer program, the fault isolation method for suppressing bridge arm overcurrent in a direct current transmission system according to any one of claims 1 to 4 is implemented.

10. A computer-readable storage medium storing a computer program; characterized in that: When the computer program is executed by a processor, the fault isolation method for suppressing overcurrent in a bridge arm of a direct current transmission system as claimed in any one of claims 1 to 4 is implemented.

Images