Fault control method suitable for extra-high voltage flexible direct current power transmission system, extra-high voltage flexible direct current power transmission system, medium and equipment

Abstract

The application discloses a fault control method suitable for an extra-high voltage flexible direct current power transmission system, the extra-high voltage flexible direct current power transmission system, a medium and equipment, and the method comprises the following steps: when it is detected that electrical parameter information of an alternating current side of a receiving end converter station meets a first fault condition, a receiving end energy consumption device is controlled to be started and maintained in operation; when it is detected that the electrical parameter information meets a second fault condition, the receiving end energy consumption device is controlled to be started and maintained in operation, and according to a mode in which an alternating current side of a sending end converter station is located, a corresponding control instruction is sent to the sending end converter station, so that the sending end converter station enters a corresponding fault processing mode; wherein a fault severity indicated by the second fault condition is higher than a fault severity indicated by the first fault condition, so that the safety and the economy of the extra-high voltage flexible direct current power transmission system can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flexible HVDC transmission, in particular to a fault control method suitable for a flexible HVDC transmission system, a flexible HVDC transmission system, a medium and equipment. BACKGROUND

[0002] At present, the distance between the two ends of the flexible HVDC transmission system is generally more than 2000 km. For the flexible HVDC system with an ultra-long transmission distance, when a transient fault occurs in the AC system at the receiving end, the power sending capacity of the receiving converter station is limited. Due to the long communication delay between stations, the power delivered by the sending converter station remains basically unchanged within a period of time (more than 30 ms) after the fault. As a result, the receiving converter station will have a significant surplus power within the period of time, which will cause the operating voltage of the sub-module of the receiving converter station to continuously rise until the protection is blocked or even the HVDC system is shut down, thereby seriously affecting the safety of the system and causing economic losses. SUMMARY

[0003] To solve the above technical problems, the embodiments of the present application provide a fault control method suitable for a flexible HVDC transmission system, a flexible HVDC transmission system, a medium and equipment, which can improve the safety and economy of the flexible HVDC transmission system.

[0004] The embodiments of the present application provide a fault control method suitable for a flexible HVDC transmission system, the flexible HVDC transmission system having a receiving converter station, a sending converter station and a receiving energy consumption device, the receiving energy consumption device being adapted to consume at least part of the DC power when operating, the at least part of the DC power referring to at least part of the DC power delivered to the receiving converter station, the method being executed by the receiving converter station and comprising:

[0005] When it is detected that the electrical parameter information of the AC side of the receiving converter station meets a first fault condition, the receiving energy consumption device is controlled to be turned on and maintained in operation;

[0006] When it is detected that the electrical parameter information meets a second fault condition, the receiving energy consumption device is controlled to be turned on and maintained in operation, and according to the mode in which the AC side of the sending converter station is located, a corresponding control instruction is sent to the sending converter station, so that the sending converter station enters a corresponding fault handling mode;

[0007] Wherein, the fault severity indicated by the second fault condition is higher than the fault severity indicated by the first fault condition.

[0008] Optionally, the electrical parameter information includes three-phase voltage of the AC side of the receiving converter station.

[0009] the first fault condition comprises that the positive sequence component of the three-phase voltage is in a first set interval;

[0010] the second fault condition comprises that the positive sequence component of the three-phase voltage is in a second set interval;

[0011] wherein, the lower boundary of the first set interval and the upper boundary of the second set interval are equal, both being a set voltage threshold, the first set interval including the set voltage threshold and the second set interval not including the set voltage threshold.

[0012] Optionally, the mode of the AC side comprises a networking mode;

[0013] when the mode of the AC side is the networking mode, the fault handling mode is adapted to instruct to reduce the DC power delivered by the sending converter station to the receiving converter station to a target DC output power value.

[0014] Optionally, the target DC output power value P pu is determined by the following formula:

[0015] P pu = U ac,pu + 0.5

[0016] wherein, U ac,pu is the per-unit value of the drop of the positive sequence component of the three-phase voltage.

[0017] Optionally, the mode of the AC side comprises an island mode, and the sending converter station is previously connected to at least one sending energy-consuming device which is in a default closed state;

[0018] when the mode of the AC side is the island mode, the fault handling mode is adapted to instruct the sending converter station to control at least part of the at least one sending energy-consuming device to be turned on and maintained in operation, so that the sending energy-consuming device which is turned on and in operation continuously consumes AC power from the sending converter station.

[0019] Optionally, the total capacity of the sending energy-consuming device which is turned on and in operation is calculated according to the per-unit value of the drop of the positive sequence component of the three-phase voltage.

[0020] Optionally, the method further comprises:

[0021] after the first fault condition is met, when it is detected that the electrical parameter information meets a first fault removal condition, controlling the receiving energy-consuming device to be turned off;

[0022] After the second fault condition is met, when it is detected that the electrical parameter information meets a second fault removal condition, the control unit controls the load device to be turned on and maintained in operation, and sends a corresponding control instruction to the sending converter station according to a mode of an AC side of the sending converter station, so that the sending converter station enters a corresponding fault handling mode.

[0023] In a second aspect, the embodiments of the present application provide a UHV flexible DC power transmission system, which has a receiving converter station, a sending converter station and a load device, the load device is adapted to consume at least part of DC power in operation, the at least part of DC power refers to at least part of DC power transmitted to the receiving converter station, and the receiving converter station is configured to:

[0024] When it is detected that electrical parameter information of an AC side of the receiving converter station meets a first fault condition, the control unit controls the load device to be turned on and maintained in operation.

[0025] When it is detected that the electrical parameter information meets a second fault condition, the control unit controls the load device to be turned on and maintained in operation, and sends a corresponding control instruction to the sending converter station according to a mode of an AC side of the sending converter station, so that the sending converter station enters a corresponding fault handling mode.

[0026] The second fault condition indicates a fault severity higher than that indicated by the first fault condition.

[0027] Optionally, the receiving converter station comprises:

[0028] a first valve group, a first end of which is electrically connected to a positive pole line of the receiving converter station, and a second end of which is electrically connected to an AC system;

[0029] a second valve group, a first end of which is electrically connected to a third end of the first valve group, a second end of which is electrically connected to the AC system, and a third end of which is electrically connected to a neutral line of the receiving converter station;

[0030] a third valve group, a first end of which is electrically connected to the neutral line of the receiving converter station, and a second end of which is electrically connected to the AC system; and

[0031] a fourth valve group, a first end of which is electrically connected to a third end of the third valve group, a second end of which is electrically connected to the AC system, and a third end of which is electrically connected to a negative pole line of the receiving converter station.

[0032] The two ends of the sending converter station are respectively electrically connected to the positive pole line and the negative pole line of the receiving converter station.

[0033] Optionally, the load device comprises:

[0034] The first DC power consumption module is electrically connected at both ends to the positive pole and the neutral pole of the receiving-end converter station, respectively; and,

[0035] The second DC power consumption module is electrically connected at both ends to the neutral line and the negative line of the receiving-end converter station, respectively.

[0036] Optionally, at least one of the first valve group, the second valve group, the third valve group, and the fourth valve group adopts a full-half-bridge hybrid module structure.

[0037] Optionally, the electrical parameter information includes the three-phase voltage on the AC side of the receiving-end converter station;

[0038] The first fault condition includes the positive sequence component of the three-phase voltage being in a first predetermined range;

[0039] The second fault condition includes the positive sequence component of the three-phase voltage being in a second preset range;

[0040] Wherein, the lower boundary of the first setting interval and the upper boundary of the second setting interval are equal, both being the setting voltage threshold, the first setting interval includes the setting voltage threshold and the second setting interval does not include the setting voltage threshold.

[0041] Optionally, the mode of the communication side includes network mode;

[0042] When the AC side is in the network mode, the fault handling mode is adapted to instruct the DC power transmission power of the DC power supplied from the sending-end converter station to the receiving-end converter station to the target DC output power value.

[0043] Optionally, the target DC output power value P pu Determined by the following formula:

[0044] P pu =U ac,pu +0.5

[0045] Among them, U ac,pu This is the per-unit value of the drop in the positive sequence component of the three-phase voltage.

[0046] Optionally, the mode of the AC side includes island mode, and the sending-end converter station is pre-connected to at least one sending-end energy-consuming device that is turned off by default.

[0047] When the AC side is in the islanded mode, the fault handling mode is adapted to instruct the sending-end converter station to control at least some of the at least one sending-end energy-consuming device to be turned on and kept running, so that the turned-on and running sending-end energy-consuming device continuously consumes AC power from the sending-end converter station.

[0048] Optionally, the total capacity of the opened and running sending-end energy consumption device is calculated according to the positive sequence component of the three-phase voltage.

[0049] Optionally, the receiving-end converter station is further configured to:

[0050] After the first fault condition is met, when it is detected that the electrical parameter information meets a first fault removal condition, the receiving-end energy consumption device is controlled to be closed;

[0051] After the second fault condition is met, when it is detected that the electrical parameter information meets a second fault removal condition, the receiving-end energy consumption device is controlled to be closed, and a fault removal instruction is sent to the sending-end converter station, wherein the fault removal instruction is adapted to instruct the sending-end converter station to exit the fault handling mode.

[0052] In a third aspect, an embodiment of the present application provides a computer readable storage medium having stored thereon a computer program, which, when executed by a processor, implements the steps of the method of any of the preceding aspects.

[0053] In a fourth aspect, an embodiment of the present application provides a computer device, comprising a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor implements the steps of the method of any of the preceding aspects when executing the computer program.

[0054] To sum up, the embodiments of the present application have at least the following beneficial effects:

[0055] By using the embodiments of the present application, the UHV flexible DC power transmission system has a receiving-end converter station, a sending-end converter station and a receiving-end energy consumption device, the sending-end converter station is configured to transmit DC power to the receiving-end converter station, the receiving-end energy consumption device is closed by default and is pre-connected to the receiving-end converter station, the receiving-end energy consumption device is adapted to consume at least part of the DC power when running, the at least part of the DC power refers to at least part of the DC power transmitted to the receiving-end converter station, and the method is executed by the receiving-end converter station and comprises: when it is detected that electrical parameter information of an AC side of the receiving-end converter station meets a first fault condition, the receiving-end energy consumption device is controlled to be opened and maintained to run; when it is detected that the electrical parameter information meets a second fault condition, the receiving-end energy consumption device is controlled to be opened and maintained to run, and according to a mode in which the AC side of the receiving-end converter station is located, a corresponding control instruction is sent to the sending-end converter station, so that the sending-end converter station enters a corresponding fault handling mode; wherein the second fault condition indicates a fault severity higher than that indicated by the first fault condition, thereby improving the safety and economy of the UHV flexible DC power transmission system. BRIEF DESCRIPTION OF DRAWINGS

[0056] Figure 1 FIG. 1 is a flow diagram of a fault control method for an UHV flexible HVDC power transmission system according to an embodiment of the present application;

[0057] Figure 2A FIG. 2 is a structural diagram of an UHV flexible HVDC power transmission system according to an embodiment of the present application;

[0058] Figure 2B FIG. 3 is a structural diagram of an UHV flexible HVDC power transmission system according to an embodiment of the present application;

[0059] Figure 3 FIG. 4 is a diagram of electrical parameter information on a DC pole line during a fault in a networking mode according to an embodiment of the present application;

[0060] Figure 4 FIG. 5 is a diagram of a maximum voltage of a receiving-end converter valve sub-module during a fault in a networking mode according to an embodiment of the present application;

[0061] Figure 5 FIG. 6 is a diagram of electrical parameter information on a DC pole line during a fault in an island mode according to an embodiment of the present application;

[0062] Figure 6 FIG. 7 is a diagram of a maximum voltage of a receiving-end converter valve sub-module during a fault in an island mode according to an embodiment of the present application;

[0063] Figure 7 FIG. 8 is a structural diagram of a computer device according to an embodiment of the present application. DETAILED DESCRIPTION

[0064] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0065] In the description of the present application, the terms "first", "second", "third" and the like are used only for descriptive purposes and are not to be construed as indicating or implying relative importance or a specific number of the technical features indicated. Therefore, the features defined with "first", "second", "third" and the like can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more. In the description of the present application, the term "comprising" and its variants are open-ended, i.e. "including but not limited to". The term "based on" is "at least partially based on". The term "according to" is "at least partially according to". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments".

[0066] In the description of the present application, it should be noted that, unless otherwise specified and limited, the terms "mounting", "connection", "connection" should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integral connection; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through intermediate medium, or the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0067] In the description of the present application, it should be noted that, unless otherwise defined, all technical and scientific terms used in the present application have the same meaning as understood by those skilled in the art. The terms used in the specification of the present application are only for the purpose of describing the specific embodiments, and are not intended to limit the present application. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0068] Referring to Figure 1 , a flowchart of a fault control method suitable for an ultra-high voltage flexible DC power transmission system is shown, the ultra-high voltage flexible DC power transmission system has a receiving end converter station, a sending end converter station and a receiving end energy consumption device, the sending end converter station is configured to transmit DC power to the receiving end converter station, the receiving end energy consumption device is closed by default and is pre-connected to the receiving end converter station, the receiving end energy consumption device is adapted to consume at least part of the DC power during operation, the at least part of the DC power refers to at least part of the DC power transmitted to the receiving end converter station, the method is executed by the receiving end converter station, and the method comprises steps S101-S102, specifically as follows:

[0069] S101, when the electrical parameter information of the AC side of the receiving end converter station meets the first fault condition, the receiving end energy consumption device is controlled to be opened and maintained in operation;

[0070] S102, when it is detected that the electrical parameter information satisfies a second fault condition, controlling the receiving end energy consumption device to start and maintain operation, and according to a mode in which the AC side of the sending end converter station is located, sending a corresponding control instruction to the sending end converter station, so that the sending end converter station enters a corresponding fault handling mode;

[0071] Wherein, the second fault condition indicates a fault severity higher than that indicated by the first fault condition.

[0072] In some embodiments, the UHV flexible DC power transmission system can be a typical ±800kV / 8GW UHV flexible DC power transmission system, and the main circuit parameters thereof are as follows: sub-module rated operating voltage 2.0kV, sub-module capacitance 24mF, bridge arm reactor 25mH, current limiting reactor 300mH. The DC power transmission line is 2400km long, and 6 split conductors are used, and the line resistance is about 10Ω. The UHV flexible DC power transmission system adopts a true bipolar connection scheme, each pole is cascaded by two valve groups, and the DC voltage of each valve group is 400kV. The valve group adopts full half-bridge hybrid modules, and the full-bridge ratio is 60%. The communication delay between the flexible DC power transmission system stations is 30ms.

[0073] In an alternative embodiment, the electrical parameter information includes three-phase voltage of the AC side of the receiving end converter station;

[0074] The first fault condition includes that the positive sequence component of the three-phase voltage is in a first set interval;

[0075] The second fault condition includes that the positive sequence component of the three-phase voltage is in a second set interval;

[0076] Wherein, the lower boundary of the first set interval and the upper boundary of the second set interval are equal, both being a set voltage threshold, the first set interval includes the set voltage threshold and the second set interval does not include the set voltage threshold.

[0077] In some cases, the set voltage threshold in the present embodiment can be 0.5pu, so when the positive sequence component of the three-phase voltage drops to 0.5pu, the first fault condition is satisfied.

[0078] In an alternative embodiment, the mode in which the AC side is located includes a networking mode;

[0079] When the mode in which the AC side is located is the networking mode, the fault handling mode is adapted to instruct the sending end converter station to reduce the DC power transmission power to a target DC output power value.

[0080] In an alternative embodiment, the target DC output power value P pu is determined by the following equation:

[0081] P pu = U ac,pu + 0.5

[0082] wherein U ac,pu is the per-unit value of the drop of the positive sequence component of the three-phase voltage.

[0083] In an alternative embodiment, the mode of the AC side comprises an island mode, and the sending-end converter station is previously connected to at least one sending-end energy consumption device which is in a default closed state;

[0084] When the mode of the AC side is the island mode, the fault handling mode is adapted to instruct the sending-end converter station to control at least partial opening of the at least one sending-end energy consumption device and maintain operation, so that the opened and operated sending-end energy consumption device continuously consumes AC power from the sending-end converter station.

[0085] In some embodiments, the at least one sending-end energy consumption device can be an AC energy consumption device configured in groups, each group being 500 MW, and a total of 8 groups, i.e. 4 GW. The sending-end energy consumption device can use a variety of technical routes such as thyristor control.

[0086] In an alternative embodiment, the total capacity of the opened and operated sending-end energy consumption device is calculated according to the per-unit value of the drop of the positive sequence component of the three-phase voltage.

[0087] In some specific examples, the total capacity of the opened and operated sending-end energy consumption device in the embodiment can be determined by the number of the opened and operated sending-end energy consumption devices, assuming that the capacity of each sending-end energy consumption device is equal. Thus, the number N of the opened and operated sending-end energy consumption devices can be determined by the following equation:

[0088]

[0089] wherein U ac,pu is the per-unit value of the drop of the positive sequence component of the three-phase voltage, and ROUNDUP[] represents rounding up.

[0090] In an alternative embodiment, the method further comprises:

[0091] controlling the receiving-end energy consumption device to be closed when it is detected that the electrical parameter information satisfies a first fault removal condition after the first fault condition is satisfied;

[0092] After the second fault condition is met, when the electrical parameter information is detected to meet the second fault clearance condition, the receiving-end energy consumption device is controlled to shut down, and a fault clearance command is sent to the sending-end converter station, wherein the fault clearance command is adapted to instruct the sending-end converter station to exit the fault handling mode.

[0093] Secondly, see Figure 2A and Figure 2B This application provides an ultra-high voltage flexible direct current (UHVDC) transmission system, which includes a receiving-end converter station, a sending-end converter station, and a receiving-end energy dissipation device. The receiving-end energy dissipation device is adapted to consume at least a portion of the DC power during operation. The at least a portion of the DC power refers to at least a portion of the DC power transmitted to the receiving-end converter station. The receiving-end converter station is configured as follows:

[0094] When the electrical parameter information of the AC side of the receiving-end converter station is detected to meet the first fault condition, the receiving-end energy consumption device is controlled to start and maintain operation.

[0095] When the electrical parameter information is detected to meet the second fault condition, the receiving end energy consumption device is controlled to start and maintain operation, and according to the AC side mode of the sending end converter station, a corresponding control command is sent to the sending end converter station so that the sending end converter station enters the corresponding fault handling mode.

[0096] The severity of the fault indicated by the second fault condition is higher than the severity of the fault indicated by the first fault condition.

[0097] In one optional implementation, the receiving-end converter station includes:

[0098] The first valve group 121 has its first end electrically connected to the positive pole of the receiving-end converter station, and its second end electrically connected to the AC system 131.

[0099] The second valve group 122 has its first end electrically connected to the third end of the first valve group 121, its second end electrically connected to the AC system 131, and its third end electrically connected to the neutral line of the receiving-end converter station.

[0100] The third valve group 123 has its first end electrically connected to the neutral line of the receiving-end converter station, and its second end electrically connected to the AC system 131; and,

[0101] The fourth valve group 124 has its first end electrically connected to the third end of the third valve group 123, its second end electrically connected to the AC system 131, and its third end electrically connected to the negative pole of the receiving-end converter station.

[0102] The two ends of the sending-end converter station are electrically connected to the positive and negative poles of the receiving-end converter station, respectively.

[0103] In an alternative embodiment, the energy consumption device at the receiving end comprises:

[0104] a first DC energy consumption module 111, both ends of which are electrically connected to the positive pole line and the neutral line of the receiving end converter station, respectively; and

[0105] a second DC energy consumption module 112, both ends of which are electrically connected to the neutral line and the negative pole line of the receiving end converter station.

[0106] In some embodiments, a 4GW DC energy consumption device can be configured on the DC side of the receiving end converter station, wherein:

[0107] the first DC energy consumption module has a capacity of 2GW and is configured between the positive pole line and the neutral line;

[0108] the second DC energy consumption module has a capacity of 2GW and is configured between the negative pole line and the neutral line;

[0109] In this way, the capacity of the DC energy consumption device is only 50% of the rated capacity of the DC power transmission system. The above-mentioned DC energy consumption device can be constructed using various technical routes such as centralized, distributed or hybrid.

[0110] In an alternative embodiment, at least one of the first valve group, the second valve group, the third valve group and the fourth valve group adopts a full-half bridge hybrid module structure.

[0111] In an alternative embodiment, the electrical parameter information includes a three-phase voltage on the AC side of the receiving end converter station.

[0112] The first fault condition includes a positive sequence component of the three-phase voltage being in a first set interval.

[0113] The second fault condition includes a positive sequence component of the three-phase voltage being in a second set interval.

[0114] Wherein, the lower boundary of the first set interval and the upper boundary of the second set interval are equal, both being a set voltage threshold, the first set interval includes the set voltage threshold and the second set interval does not include the set voltage threshold.

[0115] In an alternative embodiment, the mode in which the AC side is located includes a networking mode.

[0116] When the mode in which the AC side is located is the networking mode, the fault handling mode is adapted to instruct the DC power transmission power from the sending end converter station to the receiving end converter station to be reduced to a target DC output power value.

[0117] In an alternative embodiment, the target DC output power value Ppu is determined by the following equation:

[0118] P pu = U ac,pu + 0.5

[0119] wherein U ac,pu is the per-unit value of the drop of the positive sequence component of the three-phase voltage.

[0120] In an alternative embodiment, the mode of the AC side comprises an island mode, and the sending converter station is pre-connected to at least one sending energy-consuming device which is initially closed;

[0121] When the mode of the AC side is the island mode, the fault handling mode is adapted to instruct the sending converter station to control at least partial opening of the at least one sending energy-consuming device and maintain operation, so that the opened and operated sending energy-consuming device continuously consumes AC power from the sending converter station.

[0122] In an alternative embodiment, the total capacity of the opened and operated sending energy-consuming device is calculated according to the per-unit value of the drop of the positive sequence component of the three-phase voltage.

[0123] In an alternative embodiment, the receiving converter station is further configured to:

[0124] after the first fault condition is met, when it is detected that the electrical parameter information satisfies a first fault removal condition, control the receiving energy-consuming device to be closed;

[0125] after the second fault condition is met, when it is detected that the electrical parameter information satisfies a second fault removal condition, control the receiving energy-consuming device to be closed, and send a fault removal instruction to the sending converter station, wherein the fault removal instruction is adapted to instruct the sending converter station to exit the fault handling mode.

[0126] Two specific embodiments are provided below.

[0127] Embodiment 1

[0128] Based on a typical ±800kV / 8GW UHV flexible DC transmission system, its main circuit parameters are as follows: submodule rated operating voltage 2.0kV, submodule capacitor 24mF, bridge arm reactor 25mH, and current-limiting reactor 300mH. The DC transmission line is 2400km long, using 6-split conductors, with a line resistance of approximately 10Ω. The UHV flexible DC transmission system adopts a true bipolar connection scheme, with each pole consisting of two cascaded valve groups, each valve group having a DC voltage of 400kV. The valve groups use a hybrid full-bridge and half-bridge module, with a full-bridge ratio of 60%. The inter-station communication delay of the flexible DC system is 30ms. The AC side of the sending-end converter station is in grid-connected mode, with the sending end employing a constant active power and constant reactive power control strategy, and the receiving end employing a constant DC voltage and constant reactive power control strategy. A 4GW DC power dissipation unit is configured on the DC side of the receiving-end converter station, with 2GW configured between the positive pole and the neutral line, and the other 2GW configured between the negative pole and the neutral line. Figure 2A As shown.

[0129] Before the fault occurred, the UHV flexible DC transmission system was operating at full capacity. At a certain moment (e.g.) Figure 3 As shown in the diagram (5.1s), a two-phase metallic ground fault occurs on the AC side of the receiving-end converter transformer, causing the positive-sequence component of the three-phase voltage to drop to 0.33 pu. Approximately 10ms after the fault, the receiving-end converter station detects the fault and immediately activates the DC power dissipation device. Simultaneously, it notifies the sending-end converter station via inter-station communication to reduce power, with a power command of 0.83 pu. Approximately 40ms after the fault, the sending-end converter station receives the power reduction command via inter-station communication and immediately reduces the active power to 0.83 pu. Approximately 100ms after the fault, the AC side fault of the receiving-end converter transformer is cleared, and the positive-sequence component of the three-phase voltage rises to 1 pu. Approximately 110ms after the fault, the receiving-end converter station detects the AC side fault has been cleared, deactivates the DC power dissipation device, and simultaneously notifies the sending-end converter station via inter-station communication to restore the DC power to its previous value. Approximately 140ms after the fault, the sending-end converter station receives the power command via inter-station communication and restores the DC power to 1 pu. Figure 3 As shown, approximately 350ms after the fault, the voltage, current, and power on the DC line basically returned to their pre-fault operating state. Figure 4 The maximum voltage of the receiving-end station converter valve submodule during fault ride-through is no more than 2.7kV, which is lower than the overvoltage protection setting of the submodule. Therefore, the method provided in this embodiment can achieve system fault ride-through after a fault occurs on the AC side of the receiving-end converter transformer.

[0130] Example 2

[0131] Based on a typical ±800kV / 8GW UHV flexible DC transmission system, its main circuit parameters are as follows: submodule rated operating voltage 2.0kV, submodule capacitor 24mF, bridge arm reactor 25mH, and current-limiting reactor 300mH. The DC transmission line is 2400km long, using 6-split conductors, with a line resistance of approximately 10Ω. The UHV flexible DC transmission system adopts a true bipolar connection scheme, with each pole consisting of two cascaded valve groups, each valve group having a DC voltage of 400kV. The valve groups use a hybrid full-bridge and half-bridge module, with a full-bridge ratio of 60%. The inter-station communication delay of the flexible DC system is 30ms. The AC side of the sending-end converter station is in islanded mode, with the sending end employing a constant AC voltage amplitude and constant AC frequency control strategy, and the receiving end employing a constant DC voltage and constant reactive power control strategy. A 4GW DC power dissipation unit is configured on the DC side of the receiving-end converter station, with 2GW configured between the positive pole and the neutral line, and the other 2GW configured between the negative pole and the neutral line. A 4GW AC power dissipation unit is configured on the AC side of the sending-end converter station. Figure 2B As shown.

[0132] Before the fault occurred, the UHV flexible DC transmission system was operating at full capacity. At a certain moment (e.g.) Figure 5 As shown in the diagram (5.1s), a two-phase metallic ground fault occurs on the AC side of the receiving-end converter transformer, causing the positive-sequence component of the three-phase voltage to drop to 0.33 pu. Approximately 10ms after the fault, the receiving-end converter station detects the fault and immediately activates the DC energy dissipation device. Simultaneously, it notifies the sending-end converter station via inter-station communication to activate the AC energy dissipation device, activating three sets of devices. Approximately 40ms after the fault, the sending-end converter station receives the command to activate the AC energy dissipation device via inter-station communication and immediately activates all three sets. Approximately 100ms after the fault, the AC side fault of the receiving-end converter transformer is cleared, and the positive-sequence component of the three-phase voltage rises to 1 pu. Approximately 110ms after the fault, the receiving-end converter station detects the AC side fault has been cleared and deactivates the DC energy dissipation device, simultaneously notifying the sending-end converter station via inter-station communication to deactivate the AC energy dissipation device. Approximately 140ms after the fault, the sending-end converter station receives the command to deactivate the AC energy dissipation device via inter-station communication and deactivates all AC energy dissipation devices. Figure 5 As shown, approximately 350ms after the fault, the voltage, current, and power on the DC line basically returned to their pre-fault operating state. Figure 6 The maximum voltage of the receiving-end station converter valve submodule during fault ride-through is no more than 2.7kV, which is lower than the overvoltage protection setting of the submodule. Therefore, the method provided in this embodiment can achieve system fault ride-through after a fault occurs on the AC side of the receiving-end converter transformer.

[0133] Thirdly, embodiments of this application provide a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the method described in any of the above-mentioned embodiments.

[0134] In a fourth aspect, an embodiment of the present application provides a computer device, comprising a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor implements the steps of the method according to any one of the preceding aspects when executing the computer program.

[0135] Referring to Figure 7 The computer device of the embodiment comprises a processor 701, a memory 702, and a computer program stored in the memory 702 and executable on the processor 701, for example, a fault control program. The processor 701 implements the steps in each of the fault control method embodiments described above when executing the computer program.

[0136] For example, the computer program can be divided into one or more modules / units, which are stored in the memory 702 and executed by the processor 701 to complete the present application. The one or more modules / units can be a series of computer program instruction segments capable of completing a specific function, which are used to describe the execution process of the computer program in the computer device.

[0137] The computer device can be a desktop computer, a notebook computer, a palm computer, a cloud server, and the like. The computer device can include, but is not limited to, the processor 701 and the memory 702. Those skilled in the art can understand that the schematic diagram is only an example of the computer device, and does not limit the computer device, which can include more or fewer components than the diagram, or combine certain components, or different components, for example, the computer device can also include an input / output device, a network access device, a bus, and the like.

[0138] The processor 701 can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, or the like. The general-purpose processor can be a microprocessor or the processor 701 can also be any conventional processor, and the like. The processor 701 is the control center of the computer device, which connects all parts of the computer device through various interfaces and lines.

[0139] The memory 702 can be used to store the computer programs and / or modules, and the processor 701 realizes various functions of the computer device by running or executing the computer programs and / or modules stored in the memory 702, and calling the data stored in the memory 702. The memory 702 can mainly include a program storage area and a data storage area, wherein the program storage area can store operating systems, at least one application program required by a function (such as a sound playing function, an image playing function, etc.), and the like; and the data storage area can store data created according to the use of the mobile phone (such as audio data, a phone book, etc.), and the like. In addition, the memory 702 can include a high-speed random access memory, and can also include a nonvolatile memory, for example, a hard disk, a memory, a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, at least one disk storage device, a flash memory device, or other volatile solid-state memory devices.

[0140] The modules / units integrated in the computer device, if realized in the form of software function units and sold or used as independent products, can be stored in a computer readable storage medium. Based on this understanding, all or part of the processes in the above-mentioned embodiment methods can also be completed by a computer program instructing related hardware, and the computer program can be stored in a computer readable storage medium. When the processor 701 executes the computer program, the steps of the above-mentioned various method embodiments can be realized. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or some intermediate forms, etc. The computer readable medium can include any entity or device capable of carrying the computer program code, recording media, a U disk, a mobile hard disk, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc.

[0141] In summary, the embodiments of the present application have at least the following beneficial effects:

[0142] The UHV flexible DC power transmission system has a receiving end converter station, a sending end converter station and a receiving end energy consumption device, the sending end converter station is configured to transmit DC power to the receiving end converter station, the receiving end energy consumption device is closed by default and is pre-connected to the receiving end converter station, the receiving end energy consumption device is adapted to consume at least part of the DC power when in operation, the at least part of the DC power refers to at least part of the DC power transmitted to the receiving end converter station, the method is performed by the receiving end converter station and comprises: when it is detected that the electrical parameter information of the AC side of the receiving end converter station meets a first fault condition, controlling the receiving end energy consumption device to be turned on and maintained in operation; when it is detected that the electrical parameter information meets a second fault condition, controlling the receiving end energy consumption device to be turned on and maintained in operation, and according to the mode in which the AC side of the sending end converter station is located, sending a corresponding control instruction to the sending end converter station, so that the sending end converter station enters a corresponding fault processing mode; wherein the second fault condition indicates a fault severity higher than that indicated by the first fault condition, thereby improving the safety and economy of the UHV flexible DC power transmission system.

[0143] Through the above description of the embodiments, those skilled in the art can clearly understand that the present application can be implemented by means of software and necessary hardware platforms, and of course, it can also be implemented entirely by hardware. Based on such understanding, all or part of the technical solutions of the present application that contribute to the background art can be embodied in the form of a software product. The computer software product can be stored in a storage medium, such as a ROM / RAM, a magnetic disk, an optical disk, etc., and includes a number of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0144] The above is the preferred embodiment of the present application, it should be pointed out that, for those skilled in the art, without departing from the principles of the present application, can make a number of improvements and refinements, these improvements and refinements are also considered as the protection scope of the present application.

Claims

1. A fault control method applicable to ultra-high voltage flexible direct current transmission systems, characterized in that, The ultra-high voltage flexible direct current transmission system includes a receiving-end converter station, a sending-end converter station, and a receiving-end energy dissipation device. The receiving-end energy dissipation device is adapted to consume at least a portion of the direct current during operation. The at least a portion of the direct current refers to at least a portion of the direct current transmitted to the receiving-end converter station. The method is performed by the receiving-end converter station and includes: When the electrical parameter information of the AC side of the receiving-end converter station is detected to meet the first fault condition, the receiving-end energy consumption device is controlled to start and maintain operation. When the electrical parameter information is detected to meet the second fault condition, the receiving end energy consumption device is controlled to start and maintain operation, and according to the AC side mode of the sending end converter station, a corresponding control command is sent to the sending end converter station so that the sending end converter station enters the corresponding fault handling mode. The severity of the fault indicated by the second fault condition is higher than the severity of the fault indicated by the first fault condition.

2. The method as described in claim 1, characterized in that, The electrical parameter information includes the three-phase voltage on the AC side of the receiving-end converter station; The first fault condition includes the positive sequence component of the three-phase voltage being in a first predetermined range; The second fault condition includes the positive sequence component of the three-phase voltage being in a second preset range; Wherein, the lower boundary of the first setting interval and the upper boundary of the second setting interval are equal, both being the setting voltage threshold, the first setting interval includes the setting voltage threshold and the second setting interval does not include the setting voltage threshold.

3. The method as described in claim 2, characterized in that, The mode of the communication side includes network mode; When the AC side is in the network mode, the fault handling mode is adapted to instruct the DC power transmission power of the DC power supplied from the sending-end converter station to the receiving-end converter station to the target DC output power value.

4. The method as described in claim 3, characterized in that, The target DC output power value P pu Determined by the following formula: P pu =U ac,pu +0.5 Among them, U ac,pu This is the per-unit value of the drop in the positive sequence component of the three-phase voltage.

5. The method as described in claim 2, characterized in that, The AC side is in an islanded mode, and the sending-end converter station is pre-connected to at least one sending-end energy-consuming device that is turned off by default. When the AC side is in the islanded mode, the fault handling mode is adapted to instruct the sending-end converter station to control at least some of the at least one sending-end energy-consuming device to be turned on and kept running, so that the turned-on and running sending-end energy-consuming device continuously consumes AC power from the sending-end converter station.

6. The method as described in claim 5, characterized in that, The total capacity of the power-consuming device at the sending end that is turned on and in operation is calculated based on the per-unit value of the drop in the positive sequence component of the three-phase voltage.

7. The method according to any one of claims 1-6, characterized in that, The method further includes: After the first fault condition is met, when the electrical parameter information is detected to meet the first fault clearance condition, the receiving end energy consumption device is controlled to shut down. After the second fault condition is met, when the electrical parameter information is detected to meet the second fault clearance condition, the receiving-end energy consumption device is controlled to shut down, and a fault clearance command is sent to the sending-end converter station, wherein the fault clearance command is adapted to instruct the sending-end converter station to exit the fault handling mode.

8. An ultra-high voltage flexible direct current transmission system, characterized in that, The ultra-high voltage flexible direct current transmission system includes a receiving-end converter station, a sending-end converter station, and a receiving-end energy dissipation device. The receiving-end energy dissipation device is adapted to consume at least a portion of the direct current during operation. The at least a portion of the direct current refers to at least a portion of the direct current transmitted to the receiving-end converter station. The receiving-end converter station is configured as follows: When the electrical parameter information of the AC side of the receiving-end converter station is detected to meet the first fault condition, the receiving-end energy consumption device is controlled to start and maintain operation. When the electrical parameter information is detected to meet the second fault condition, the receiving end energy consumption device is controlled to start and maintain operation, and according to the AC side mode of the sending end converter station, a corresponding control command is sent to the sending end converter station so that the sending end converter station enters the corresponding fault handling mode. The severity of the fault indicated by the second fault condition is higher than the severity of the fault indicated by the first fault condition.

9. The system as described in claim 8, characterized in that, The receiving-end converter station includes: The first valve group has its first end electrically connected to the positive pole of the receiving-end converter station, and its second end electrically connected to the AC system. The second valve group has its first end electrically connected to the third end of the first valve group, its second end electrically connected to the AC system, and its third end electrically connected to the neutral line of the receiving-end converter station. The third valve group has its first end electrically connected to the neutral line of the receiving-end converter station and its second end electrically connected to the AC system; and... The fourth valve group has its first end electrically connected to the third end of the third valve group, its second end electrically connected to the AC system, and its third end electrically connected to the negative pole of the receiving-end converter station. The two ends of the sending-end converter station are electrically connected to the positive and negative poles of the receiving-end converter station, respectively.

10. The system as described in claim 9, characterized in that, The receiving-end energy dissipation device includes: The first DC power consumption module is electrically connected at both ends to the positive pole and the neutral pole of the receiving-end converter station, respectively; and, The second DC power consumption module is electrically connected at both ends to the neutral line and the negative line of the receiving-end converter station, respectively.

11. The system as described in claim 9, characterized in that, At least one of the first valve group, the second valve group, the third valve group, and the fourth valve group adopts a full-half-bridge hybrid module structure.

12. The system as described in claim 8, characterized in that, The electrical parameter information includes the three-phase voltage on the AC side of the receiving-end converter station; The first fault condition includes the positive sequence component of the three-phase voltage being in a first predetermined range; The second fault condition includes the positive sequence component of the three-phase voltage being in a second preset range; Wherein, the lower boundary of the first setting interval and the upper boundary of the second setting interval are equal, both being the setting voltage threshold, the first setting interval includes the setting voltage threshold and the second setting interval does not include the setting voltage threshold.

13. The system as described in claim 12, characterized in that, The mode of the communication side includes network mode; When the AC side is in the network mode, the fault handling mode is adapted to instruct the DC power transmission power of the DC power supplied from the sending-end converter station to the receiving-end converter station to the target DC output power value.

14. The system as described in claim 13, characterized in that, The target DC output power value P pu Determined by the following formula: P pu =U ac,pu +0.5 Among them, U ac,pu This is the per-unit value of the drop in the positive sequence component of the three-phase voltage.

15. The system as described in claim 12, characterized in that, The AC side is in an islanded mode, and the sending-end converter station is pre-connected to at least one sending-end energy-consuming device that is turned off by default. When the AC side is in the islanded mode, the fault handling mode is adapted to instruct the sending-end converter station to control at least some of the at least one sending-end energy-consuming device to be turned on and kept running, so that the turned-on and running sending-end energy-consuming device continuously consumes AC power from the sending-end converter station.

16. The system as described in claim 15, characterized in that, The total capacity of the power-consuming device at the sending end that is turned on and in operation is calculated based on the per-unit value of the drop in the positive sequence component of the three-phase voltage.

17. The system according to any one of claims 8-16, characterized in that, The receiving-end converter station is also configured to: After the first fault condition is met, when the electrical parameter information is detected to meet the first fault clearance condition, the receiving end energy consumption device is controlled to shut down. After the second fault condition is met, when the electrical parameter information is detected to meet the second fault clearance condition, the receiving-end energy consumption device is controlled to shut down, and a fault clearance command is sent to the sending-end converter station, wherein the fault clearance command is adapted to instruct the sending-end converter station to exit the fault handling mode.

18. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the method described in any one of claims 1-7.

19. A computer device, characterized in that, The method includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor, when executing the computer program, implements the method of any one of claims 1-7.

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