Energy consumption device suitable for extra-high voltage flexible direct current power transmission system and fault control method

Abstract

The invention discloses an energy consumption device suitable for an extra-high voltage flexible direct current power transmission system and a fault control method, and the device comprises a first direct current energy consumption module, two ends of which are electrically connected to a positive electrode line at a receiving end side and between a third end of a first valve group and a first end of a second valve group; the two ends of the second direct current energy consumption module are electrically connected to the neutral line on the receiving end side and between the third end of the first valve group and the first end of the second valve group respectively; the two ends of the third direct-current energy consumption module are electrically connected to the neutral line on the receiving end side and between the third end of the third valve group and the first end of the fourth valve group; and the two ends of the fourth direct current energy consumption module are electrically connected to the negative electrode wire on the receiving end side and the position between the third end of the third valve set and the first end of the fourth valve set correspondingly, the energy consumption efficiency of the direct current energy consumption device can be improved, the overall economical efficiency of the extra-high voltage flexible direct current power transmission technology is improved, and the system safety is improved.

Description

Technical Field

[0001] The present application relates to the technical field of flexible direct current transmission, and in particular to an energy consumption device and a fault control method applicable to an ultra-high voltage flexible direct current transmission system. Background Art

[0002] At present, due to the high requirements of wind power and photovoltaic power generation for regional natural environmental conditions, many large-scale wind power and photovoltaic bases are built in areas far away from densely populated areas. In this case, ultra-high voltage flexible direct current transmission technology is usually used as the main technical solution for large-scale long-distance transmission and consumption of new energy power to transmit power to densely populated areas. However, with the gradual increase in the power capacity transmitted by ultra-high voltage flexible direct current transmission projects, multi-feed large-capacity direct current is easy to be concentrated in the load center of densely populated areas. When large-capacity direct current is connected to the AC system on the receiving side through a single landing point, it will cause local current to increase and DC fault to stop operation, which will easily cause a huge impact on the AC power grid on the receiving side. In addition, since the distance between the two ends of the ultra-high voltage flexible direct current transmission technology is generally more than 2000km, when the AC system on the receiving side has a transient fault, it is easy to cause significant surplus power on the receiving side, which may trigger protection lockout or even shutdown of the ultra-high voltage flexible direct current transmission system, causing serious economic losses and safety hazards.

[0003] In the related art, a DC energy dissipation device is usually directly configured between the positive and negative poles of the receiving end to reduce the impact on the receiving end and consume surplus power. However, directly configuring the DC energy dissipation device between the positive and negative poles of the receiving end has low energy dissipation efficiency, resulting in high configuration costs of the DC energy dissipation device and potential safety hazards caused by insufficient energy dissipation efficiency. Summary of the invention

[0004] In order to solve the above technical problems, the embodiment of the present application proposes an energy consumption device and a fault control method suitable for an ultra-high voltage flexible direct current transmission system, which can improve the energy consumption efficiency of the direct current energy consumption device to enhance the overall economy of the ultra-high voltage flexible direct current transmission technology and improve the system safety.

[0005] In a first aspect, an embodiment of the present application provides an energy consumption device applicable to an ultra-high voltage flexible direct current power transmission system, wherein the ultra-high voltage flexible direct current power transmission system has a receiving end side, and the receiving end side includes:

[0006] a first valve group, a first end of which is electrically connected to the positive electrode line on the receiving end side, and a second end of which is electrically connected to the first AC system;

[0007] A second valve group, a first end of which is electrically connected to the third end of the first valve group, a second end of which is electrically connected to the second AC system, and a third end of which is electrically connected to the neutral line on the receiving end side;

[0008] A third valve group, a first end of which is electrically connected to the neutral line of the receiving end, and a second end of which is electrically connected to the second AC system; and

[0009] a fourth valve group, a first end of which is electrically connected to the third end of the third valve group, a second end of which is electrically connected to the first AC system, and a third end of which is electrically connected to the negative electrode line on the receiving end side;

[0010] Wherein, the energy consumption device comprises:

[0011] A first DC energy consumption module, two ends of which are respectively electrically connected to the positive electrode line on the receiving end side, and between the third end of the first valve group and the first end of the second valve group;

[0012] A second DC energy consumption module, two ends of which are respectively electrically connected to the neutral line on the receiving end side, and between the third end of the first valve group and the first end of the second valve group;

[0013] A third DC energy consumption module, both ends of which are electrically connected to the neutral line of the receiving end side, and between the third end of the third valve group and the first end of the fourth valve group; and

[0014] The fourth DC energy consumption module has two ends electrically connected to the negative pole line on the receiving end side, and between the third end of the third valve group and the first end of the fourth valve group.

[0015] Optionally, the total capacity of the energy consumption device is equal to the DC power transmission rated capacity of the receiving end multiplied by a set ratio, wherein the set ratio is less than 1, and the total capacity of the energy consumption device refers to the sum of the capacities of the first DC energy consumption module, the second DC energy consumption module, the third DC energy consumption module and the fourth DC energy consumption module.

[0016] Optionally, the first DC energy consumption module, the second DC energy consumption module, the third DC energy consumption module and the fourth DC energy consumption module have the same capacity;

[0017] The setting ratio is 0.5.

[0018] Optionally, at least one of the first valve group, the second valve group, the third valve group, and the fourth valve group is a full half-bridge hybrid module structure.

[0019] Optionally, the UHV flexible direct current power transmission system further has a sending end side, and two ends of the sending end side are electrically connected to the positive pole line and the negative pole line of the receiving end side respectively, wherein:

[0020] When the AC side of the sending-end converter station in the sending-end side is in a networking mode, the sending-end side is configured to adopt a control strategy based on fixed active power and fixed reactive power to control its own power;

[0021] When the AC side of the sending-end converter station in the sending-end side is in island mode, the AC side of the sending-end converter station is connected to an AC energy consumption device, wherein the AC energy consumption device is composed of multiple groups of AC energy consumption sub-devices configured in groups.

[0022] In a second aspect, an embodiment of the present application provides a fault control method, which is applicable to the energy consumption device described in the first aspect above, wherein the energy consumption device does not enter an energy consumption mode in a default state, and the method includes:

[0023] When a fault is detected in the first AC system, if the positive sequence component of the three-phase voltage of the first AC system is greater than or equal to a first threshold, the first DC energy consumption module and the fourth DC energy consumption module are controlled to enter an energy consumption mode, until it is detected that the fault is eliminated, and then the first DC energy consumption module and the fourth DC energy consumption module are controlled to exit the energy consumption mode;

[0024] When a fault is detected in the second AC system, if the positive sequence component of the three-phase voltage of the second AC system is greater than or equal to a second threshold, the second DC energy consumption module and the third DC energy consumption module are controlled to enter an energy consumption mode until it is detected that the fault is eliminated, and then the second DC energy consumption module and the third DC energy consumption module are controlled to exit the energy consumption mode.

[0025] Optionally, the UHV flexible direct current power transmission system further has a sending end side, two ends of the sending end side are respectively electrically connected to the positive pole line and the negative pole line of the receiving end side, and a sending end converter station communicatively connected to the energy consumption device is provided in the sending end side, and the method further includes:

[0026] When a fault is detected in the first AC system, if the positive sequence component of the three-phase voltage of the first AC system is less than the first threshold, the first DC energy consumption module and the fourth DC energy consumption module are controlled to enter an energy consumption mode, and according to the detected mode of the AC side of the sending-end converter station, a corresponding first sending-end control instruction is sent to the sending-end converter station, until it is detected that the fault is eliminated, the first DC energy consumption module and the fourth DC energy consumption module are controlled to exit the energy consumption mode, and a first cancellation instruction is sent to the sending-end converter station, wherein the first cancellation instruction is used to cancel the control of the first sending-end control instruction;

[0027] When a fault is detected in the second AC system, if the positive sequence component of the three-phase voltage of the second AC system is less than the second threshold value, the second DC energy consumption module and the third DC energy consumption module are controlled to enter the energy consumption mode, and according to the detected mode of the AC side of the sending-end converter station, the corresponding second sending-end control instruction is sent to the sending-end converter station, until it is detected that the fault is eliminated, the second DC energy consumption module and the third DC energy consumption module are controlled to exit the energy consumption mode, and a second cancellation instruction is sent to the sending-end converter station, wherein the second cancellation instruction is used to cancel the control of the second sending-end control instruction.

[0028] Optionally, the AC side of the sending-end converter station is connected to an AC energy consumption device, and the AC energy consumption device does not enter an energy consumption mode in a default state, and the mode of the AC side of the sending-end converter station includes a networking mode or an island mode;

[0029] When the AC side of the sending-end converter station is in the networking mode, the first sending-end control instruction is used to instruct the sending-end converter station to reduce the active power to a specified power value that matches the first sending-end control instruction, and the second sending-end control instruction is used to instruct the sending-end converter station to reduce the active power to a specified power value that matches the second sending-end control instruction;

[0030] When the mode of the AC side of the sending-end converter station is the island mode, the first sending-end control instruction is used to instruct the sending-end converter station to control the AC energy consumption device to enter an energy consumption mode matching the first sending-end control instruction, and the second sending-end control instruction is used to instruct the sending-end converter station to control the AC energy consumption device to enter an energy consumption mode matching the second sending-end control instruction.

[0031] Optionally, the specified power value P that matches the first sending end control instruction pu,1 It is expressed by the following formula:

[0032]

[0033] The specified power value P that matches the second sending end control instruction pu,2 It is expressed by the following formula:

[0034]

[0035] Among them, U ac,pu,1 is the per-unit value of the positive sequence component of the three-phase voltage of the first AC system after a fault occurs in the first AC system, U ac,pu,2 is the per-unit value of the decrease of the positive sequence component of the three-phase voltage of the second AC system after a fault occurs in the second AC system.

[0036] Optionally, the AC energy consumption device is composed of a plurality of groups of AC energy consumption sub-devices configured in groups;

[0037] in,

[0038] The energy consumption mode matched with the first sending-end control instruction is suitable for indicating a first number of AC energy consumption sub-devices that need to enter the energy consumption mode, wherein the first number is determined according to a ratio of a decrease in a positive sequence component of a three-phase voltage of the first AC system after a fault occurs in the first AC system;

[0039] The energy consumption mode matching the second sending-end control instruction is suitable for indicating the second number of AC energy consumption sub-devices that need to enter the energy consumption mode, and the second number is determined based on the proportion of the decrease in the positive sequence component of the three-phase voltage of the second AC system after a fault occurs in the second AC system.

[0040] In summary, the embodiments of the present application have at least the following beneficial effects:

[0041] By adopting the embodiment of the present application, on the premise that the receiving end side is configured to be connected to the AC system through valve group layering (that is, the first valve group and the fourth valve group are connected to one AC system, and the second valve group and the third valve group are connected to another AC system), the energy consumption device is also configured accordingly to adapt to the structure of the valve group layering, so that a small-capacity DC energy consumption module can be used to adapt to the changes in capacity requirements of different valve groups, so as to improve energy consumption efficiency and reduce the total capacity of energy consumption devices, thereby improving the overall economy of ultra-high voltage flexible DC transmission technology and improving system safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1A It is a structural schematic diagram of the ultra-high voltage flexible direct current power transmission system and its energy consumption device provided in the embodiment of the present application;

[0043] Figure 1B It is a structural schematic diagram of the ultra-high voltage flexible direct current power transmission system and its energy consumption device provided in the embodiment of the present application;

[0044] Figure 2 It is a flowchart of a fault control method provided in an embodiment of the present application;

[0045] Figure 3 It is a schematic diagram of parameter information of the ultra-high voltage flexible direct current transmission system when a fault occurs in the networking mode provided by an embodiment of the present application;

[0046] Figure 4 It is a schematic diagram of the voltage of the high-end converter valve submodule of the receiving station when a fault occurs in the networking mode provided by an embodiment of the present application;

[0047] Figure 5It is a schematic diagram of parameter information of a UHV flexible direct current transmission system when a fault occurs in an island mode provided by an embodiment of the present application;

[0048] Figure 6 It is a schematic diagram of the voltage of the high-end converter valve submodule of the receiving station when a fault occurs in the island mode provided by an embodiment of the present application. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0050] In the description of the present application, the terms "first", "second", "third", etc. are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, features defined as "first", "second", "third", etc. may explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, the meaning of "multiple" is two or more. In the description of the present application, the term "including" and its variations are open inclusions, i.e., "including but not limited to". The term "based on" means "at least partially based on". The term "according to" means "at least partially based on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one other embodiment"; the term "some embodiments" means "at least some embodiments".

[0051] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0052] In the description of this application, it should be noted that, unless otherwise defined, all technical and scientific terms used in this application have the same meaning as those commonly understood by those skilled in the art. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood by specific circumstances.

[0053] First, see Figure 1A and Figure 1B ,in, Figure 1A This is the case when the AC side of the sending-end converter station is in interconnected mode. Figure 1B For the case where the AC side of the sending-end converter station in the sending-end side is in an island mode, a schematic diagram of the structure of an energy dissipation device applicable to an ultra-high voltage flexible direct current power transmission system provided in an embodiment of the present application is shown, and the ultra-high voltage flexible direct current power transmission system has a receiving-end side, and the receiving-end side includes:

[0054] A first valve group 121, a first end of which is electrically connected to the positive electrode line on the receiving end side, and a second end of which is electrically connected to the first AC system 131;

[0055] A second valve group 122, a first end of which is electrically connected to the third end of the first valve group 121, a second end of which is electrically connected to the second AC system 132, and a third end of which is electrically connected to the neutral line on the receiving end side;

[0056] A third valve group 123, a first end of which is electrically connected to the neutral line of the receiving end, and a second end of which is electrically connected to the second AC system 132; and

[0057] The fourth valve group 124 has a first end electrically connected to the third end of the third valve group 123 , a second end electrically connected to the first AC system 131 , and a third end electrically connected to the negative electrode line on the receiving end side.

[0058] In one example, this embodiment can be targeted at a typical ±800kV / 8GW receiving-end layered ultra-high voltage flexible direct current transmission system, whose main circuit parameters are as follows: submodule rated operating voltage 2.0kV, submodule capacitance 24mF, bridge arm reactor 25mH, current limiting reactor 300mH. The DC transmission line is 2400km long, using 6 split conductors, and the line resistance is about 10Ω. The ultra-high voltage flexible direct current transmission system adopts a true bipolar wiring scheme, with two valve groups cascaded per pole, and the DC voltage of each valve group is 400kV. The valve group adopts a full half-bridge hybrid module, and the full bridge ratio is 60%. The communication delay between stations in the flexible direct current system is 30ms. The receiving station included in the receiving side is connected to the AC system through a layered manner of high-end and low-end valve groups, that is, the high-end valves of the positive and negative poles (i.e., the first valve group 121 and the fourth valve group 124) are connected to the first AC system 131, and the low-end valves of the positive and negative poles (i.e., the second valve group 122 and the third valve group 123) are connected to the second AC system 132. The electrical distance between the two AC systems is relatively far, so they can be approximated as two independent AC systems.

[0059] Wherein, the energy consumption device comprises:

[0060] The first DC energy consumption module 111 has two ends electrically connected to the positive electrode line on the receiving end side, and between the third end of the first valve group 121 and the first end of the second valve group 122;

[0061] The second DC energy consumption module 112 has two ends electrically connected to the neutral line of the receiving end side, and between the third end of the first valve group 121 and the first end of the second valve group 122;

[0062] The third DC energy consumption module 113 has two ends electrically connected to the neutral line of the receiving end side, and between the third end of the third valve group 123 and the first end of the fourth valve group 124; and

[0063] The fourth DC energy consumption module 114 has two ends electrically connected to the negative electrode line on the receiving end side, and between the third end of the third valve group 123 and the first end of the fourth valve group 124 .

[0064] In one example, the energy consumption device is configured on the DC side of the receiving-end converter station provided on the receiving-end side, with a total capacity of 4GW, of which:

[0065] The first DC energy consumption module 111 has a capacity of 1GW and is arranged between the positive pole line and the 400kV connecting busbar of the positive pole (the 400kV connecting busbar of the positive pole is arranged between the third end of the first valve group 121 and the first end of the second valve group 122), so that it can be connected in parallel with the high-end valve group of the positive pole.

[0066] The second DC energy consumption module 112 has a capacity of 1GW and is arranged between the 400kV connecting busbar of the positive pole and the neutral line, so that it can be connected in parallel with the low-end valve group of the positive pole.

[0067] The third DC energy consumption module 113 has a capacity of 1GW and is arranged between the 400kV connecting busbar of the negative pole (the 400kV connecting busbar of the negative pole is arranged between the third end of the third valve group 123 and the first end of the fourth valve group 124) and the neutral line, so that it can be connected in parallel with the low-end valve group of the negative pole.

[0068] The fourth DC energy consumption module 114 has a capacity of 1GW and is arranged between the negative pole line and the negative 400kV connecting busbar, so that it can be connected in parallel with the negative high-end valve group.

[0069] Therefore, the total capacity of the DC energy consumption devices can be made only 50% of the rated capacity of the DC transmission system.

[0070] In some cases, energy-consuming devices can adopt multiple technical routes such as centralized, distributed or hybrid.

[0071] In an optional implementation, the total capacity of the energy consumption device is equal to the DC power transmission rated capacity of the receiving end multiplied by a set ratio, wherein the set ratio is less than 1, and the total capacity of the energy consumption device refers to the sum of the capacities of the first DC energy consumption module 111, the second DC energy consumption module 112, the third DC energy consumption module 113 and the fourth DC energy consumption module 114.

[0072] In an optional implementation, the first DC energy consumption module 111, the second DC energy consumption module 112, the third DC energy consumption module 113 and the fourth DC energy consumption module 114 have the same capacity;

[0073] The setting ratio is 0.5.

[0074] In an optional implementation, at least one of the first valve group 121 , the second valve group 122 , the third valve group 123 , and the fourth valve group 124 is a full half-bridge hybrid module structure.

[0075] In an optional implementation, the UHV flexible DC power transmission system further has a sending end side, and two ends of the sending end side are electrically connected to the positive pole line and the negative pole line of the receiving end side, respectively, wherein:

[0076] When the AC side of the sending-end converter station in the sending-end side is in a networking mode, the sending-end side is configured to adopt a control strategy based on fixed active power and fixed reactive power to control its own power;

[0077] When the AC side of the sending-end converter station in the sending-end side is in island mode, the AC side of the sending-end converter station is connected to an AC energy consumption device, wherein the AC energy consumption device is composed of multiple groups of AC energy consumption sub-devices configured in groups.

[0078] In this embodiment, if the AC side of the sending-end converter station is in networking mode, the sending end needs to adopt a fixed active power and fixed reactive power control strategy; if the AC side of the sending-end converter station is in island mode, it is necessary to configure a 2GW AC energy consumption device on the AC side of the sending-end converter station. Among them, if the sending-end converter station is equipped with an AC energy consumption device, the AC energy consumption device is configured in groups, with each group of 250MW, and a total of 8 groups, totaling 2GW. The AC energy consumption device can adopt a variety of technical routes such as thyristor control.

[0079] Second, see Figure 2 , shows a flow chart of a fault control method provided by an embodiment of the present application, which is applicable to the energy consumption device described in the first aspect above, and the energy consumption device does not enter the energy consumption mode in the default state. The method includes steps S201-S202, which are as follows:

[0080] S201, when it is detected that the first AC system 131 has a fault, if the positive sequence component of the three-phase voltage of the first AC system 131 is greater than or equal to a first threshold, the first DC energy consumption module 111 and the fourth DC energy consumption module 114 are controlled to enter an energy consumption mode, until it is detected that the fault is eliminated, and then the first DC energy consumption module 111 and the fourth DC energy consumption module 114 are controlled to exit the energy consumption mode;

[0081] S202, when it is detected that the second AC system 132 has a fault, if the positive sequence component of the three-phase voltage of the second AC system 132 is greater than or equal to a second threshold, the second DC energy consumption module 112 and the third DC energy consumption module 113 are controlled to enter an energy consumption mode, until it is detected that the fault is eliminated, and then the second DC energy consumption module 112 and the third DC energy consumption module 113 are controlled to exit the energy consumption mode. Exemplarily, the first threshold and / or the second threshold is 0.5 pu.

[0082] In this embodiment, when a fault occurs in the AC system connected to the high-end valve group of the receiving-end converter station and the positive-sequence component of the three-phase voltage of the AC system drops to 0.5pu or above, the receiving-end converter station detects the fault and immediately puts into operation the DC energy consumption device connected in parallel with the high-end valve group (the positive pole is put into operation with one group of DC energy consumption devices connected in parallel with the positive high-end valve group, and the negative pole is put into operation with one group of DC energy consumption devices connected in parallel with the negative high-end valve group, with a total of 2GW DC energy consumption devices put into operation); when the receiving-end converter station detects that the AC system fault has been cleared, the DC energy consumption device is exited. When a fault occurs in the AC system connected to the low-end valve group of the receiving-end converter station and the positive-sequence component of the three-phase voltage of the AC system drops to 0.5pu or above, the receiving-end converter station immediately puts into operation the DC energy consumption device in parallel with the low-end valve group after detecting the fault (one group of DC energy consumption devices in parallel with the positive low-end valve group is put into operation at the positive pole, and one group of DC energy consumption devices in parallel with the negative low-end valve group is put into operation at the negative pole, with a total of 2GW DC energy consumption devices put into operation); when the receiving-end converter station detects that the AC system fault has been cleared, it exits the DC energy consumption device.

[0083] In an optional implementation, the UHV flexible DC power transmission system further has a sending end side, two ends of the sending end side are respectively electrically connected to the positive pole line and the negative pole line of the receiving end side, and the sending end side is provided with a sending end converter station communicatively connected to the energy consumption device, and the method further includes:

[0084] When a fault is detected in the first AC system 131, if the positive sequence component of the three-phase voltage of the first AC system 131 is less than the first threshold value, the first DC energy consumption module 111 and the fourth DC energy consumption module 114 are controlled to enter the energy consumption mode, and according to the detected mode of the AC side of the sending-end converter station, a corresponding first sending-end control instruction is sent to the sending-end converter station, until it is detected that the fault is eliminated, the first DC energy consumption module 111 and the fourth DC energy consumption module 114 are controlled to exit the energy consumption mode, and a first cancellation instruction is sent to the sending-end converter station, wherein the first cancellation instruction is used to cancel the control of the first sending-end control instruction;

[0085] When a fault is detected in the second AC system 132, if the positive sequence component of the three-phase voltage of the second AC system 132 is less than the second threshold value, the second DC energy consumption module 112 and the third DC energy consumption module 113 are controlled to enter the energy consumption mode, and according to the detected mode of the AC side of the sending-end converter station, the corresponding second sending-end control instruction is sent to the sending-end converter station until it is detected that the fault is eliminated, and then the second DC energy consumption module 112 and the third DC energy consumption module 113 are controlled to exit the energy consumption mode, and a second cancellation instruction is sent to the sending-end converter station, wherein the second cancellation instruction is used to cancel the control of the second sending-end control instruction.

[0086] In an optional implementation, the AC side of the sending-end converter station is connected to an AC energy consumption device, and the AC energy consumption device does not enter an energy consumption mode in a default state, and the mode of the AC side of the sending-end converter station includes a networking mode or an island mode;

[0087] When the AC side of the sending-end converter station is in the networking mode, the first sending-end control instruction is used to instruct the sending-end converter station to reduce the active power to a specified power value that matches the first sending-end control instruction, and the second sending-end control instruction is used to instruct the sending-end converter station to reduce the active power to a specified power value that matches the second sending-end control instruction; at this time, the first cancellation instruction is also used to restore the DC power of the sending-end converter station to the rated power value or to the DC power at the moment before the first sending-end control instruction is received, and the second cancellation instruction is also used to restore the DC power of the sending-end converter station to the rated power value or to the DC power at the moment before the second sending-end control instruction is received;

[0088] When the mode of the AC side of the sending-end converter station is the island mode, the first sending-end control instruction is used to instruct the sending-end converter station to control the AC energy consumption device to enter an energy consumption mode matching the first sending-end control instruction, and the second sending-end control instruction is used to instruct the sending-end converter station to control the AC energy consumption device to enter an energy consumption mode matching the second sending-end control instruction.

[0089] In an optional implementation, the specified power value P that matches the first sending end control instruction pu,1 It is expressed by the following formula:

[0090]

[0091] The specified power value P that matches the second sending end control instruction pu,2 It is expressed by the following formula:

[0092]

[0093] Among them, U ac,pu,1 is the per-unit value of the positive sequence component of the three-phase voltage of the first AC system 131 after a fault occurs in the first AC system 131, U ac,pu,2 is the per-unit value of the positive sequence component of the three-phase voltage of the second AC system 132 dropped after a fault occurs in the second AC system 132 .

[0094] In an optional implementation, the AC energy consumption device is composed of a plurality of groups of AC energy consumption sub-devices configured in groups;

[0095] in,

[0096] The energy consumption mode matched with the first sending-end control instruction is suitable for indicating a first number of AC energy consumption sub-devices that need to enter the energy consumption mode, wherein the first number is determined according to a ratio of a decrease in a positive sequence component of a three-phase voltage of the first AC system 131 after a fault occurs in the first AC system 131;

[0097] The energy consumption mode matching the second sending-end control instruction is suitable for indicating the second number of AC energy consumption sub-devices that need to enter the energy consumption mode, and the second number is determined based on the proportion of the decrease in the positive sequence component of the three-phase voltage of the second AC system 132 after a fault occurs in the second AC system 132.

[0098] In this embodiment, when the AC system connected to the high-end valve group of the receiving-end converter station fails and the positive sequence component of the three-phase voltage of the AC system drops below 0.5pu, it is divided into two cases: the AC side of the sending-end converter station is in the networking mode or the island mode:

[0099] 1) If the AC side of the sending-end converter station is in networking mode, when the receiving-end converter station detects a fault, it immediately puts the DC energy consumption device connected in parallel to the high-end valve group into operation, and at the same time notifies the sending-end converter station to reduce power through inter-station communication. The power command value is calculated according to the following formula. When the sending-end converter station receives the power reduction command through inter-station communication, it immediately reduces the active power to the specified value. When the receiving-end converter station detects that the AC system fault has been cleared, it exits the DC energy consumption device, and at the same time notifies the sending-end converter station through inter-station communication to restore the DC power to the rated value or the previous value. When the sending-end converter station receives the power command through inter-station communication, it restores the DC power to the rated value or the previous value.

[0100]

[0101] Among them, U ac,pu,1 is the per-unit value of the positive sequence component of the three-phase voltage of the first AC system 131 dropped after the first AC system 131 fails, and the specified power value P matched with the first sending-end control instruction pu,1 Expressed in per-unit value form.

[0102] 2) If the AC side of the sending-end converter station is in island mode, when the receiving-end converter station detects a fault, it immediately starts the DC energy consumption device connected in parallel to the high-end valve group, and at the same time notifies the sending-end converter station to start the AC energy consumption device through inter-station communication. The number of AC energy consumption devices put into operation is calculated according to the following formula. When the sending-end converter station receives the instruction to start the AC energy consumption device through inter-station communication, it immediately starts the specified number of AC energy consumption devices. When the receiving-end converter station detects that the AC system fault has been cleared, it exits the DC energy consumption device, and at the same time notifies the sending-end converter station to exit the AC energy consumption device through inter-station communication. When the sending-end converter station receives the instruction to exit the AC energy consumption device through inter-station communication, it exits all AC energy consumption devices.

[0103]

[0104] Among them, ROUNDUP[] means rounding up.

[0105] In this embodiment, when the AC system connected to the low-end valve group of the receiving-end converter station fails and the positive sequence component of the three-phase voltage of the AC system drops below 0.5pu, it is divided into two cases: the AC side of the sending-end converter station is in the networking mode or the island mode:

[0106] 1) If the AC side of the sending-end converter station is in networking mode, when the receiving-end converter station detects a fault, the DC energy consumption device connected in parallel to the low-end valve group is immediately put into operation, and the sending-end converter station is notified to reduce power through inter-station communication. The power command value is calculated according to the following formula. When the sending-end converter station receives the power reduction command through inter-station communication, it immediately reduces the active power to the specified value. When the receiving-end converter station detects that the AC system fault has been cleared, the DC energy consumption device is exited, and the sending-end converter station is notified through inter-station communication to restore the DC power to the rated value or the previous value. When the sending-end converter station receives the power command through inter-station communication, it restores the DC power to the rated value or the previous value.

[0107]

[0108] Among them, U ac,pu,2 is the per-unit value of the positive sequence component of the three-phase voltage of the second AC system 132 that decreases after the second AC system 132 fails, and the specified power value P that matches the second sending-end control instruction pu,2 Expressed in per-unit value form.

[0109] 2) If the AC side of the sending-end converter station is in island mode, when the receiving-end converter station detects a fault, it immediately starts the DC energy consumption device connected in parallel to the low-end valve group, and at the same time notifies the sending-end converter station to start the AC energy consumption device through inter-station communication. The number of AC energy consumption devices put into operation is calculated according to the following formula. When the sending-end converter station receives the instruction to start the AC energy consumption device through inter-station communication, it immediately starts the specified number of AC energy consumption devices. When the receiving-end converter station detects that the AC system fault has been cleared, it exits the DC energy consumption device, and at the same time notifies the sending-end converter station to exit the AC energy consumption device through inter-station communication. When the sending-end converter station receives the instruction to exit the AC energy consumption device through inter-station communication, it exits all AC energy consumption devices.

[0110]

[0111] Among them, ROUNDUP[] means rounding up.

[0112] Two specific embodiments are given below.

[0113] Example 1

[0114] Based on a typical ±800kV / 8GW receiving-end layered UHV flexible DC transmission system, its main circuit parameters are as follows: submodule rated working voltage 2.0kV, submodule capacitance 24mF, bridge arm reactor 25mH, current limiting reactor 300mH. The DC transmission line length is 2400km, using 6 split conductors, and the line resistance is about 10Ω. The UHV flexible DC transmission system adopts a true bipolar wiring scheme, with two valve groups cascaded per pole, and the DC voltage of each valve group is 400kV. The valve group adopts a full half-bridge hybrid module, and the full-bridge ratio is 60%. The communication delay between stations in the flexible DC system is 30ms. The receiving station is connected to the AC system through the high-end and low-end valve groups in a layered manner, that is, the high-end valves of the positive and negative poles are connected to one AC system, and the low-end valves of the positive and negative poles are connected to another AC system. The electrical distance between the two AC systems is relatively far, which can be approximated as two independent AC systems. The AC side of the sending-end converter station is in networking mode, the sending end adopts a fixed active power and fixed reactive power control strategy, and the receiving end adopts a fixed DC voltage and fixed reactive power control strategy. A 4GW DC energy consumption device is configured on the DC side of the receiving-end converter station, of which 1GW is configured between the positive pole line and the 400kV connecting busbar of the positive pole (that is, in parallel with the high-end valve group of the positive pole), 1GW is configured between the 400kV connecting busbar of the positive pole and the neutral line (that is, in parallel with the low-end valve group of the positive pole), 1GW is configured between the negative pole line and the 400kV connecting busbar of the negative pole (that is, in parallel with the high-end valve group of the negative pole), and 1GW is configured between the 400kV connecting busbar of the negative pole and the neutral line (that is, in parallel with the low-end valve group of the negative pole). Figure 1A shown.

[0115] Before the fault occurs, the UHV flexible DC transmission system operates at full capacity. Figure 3 5.1s), a two-phase metallic grounding fault occurred in the AC system connected to the high-end valve group of the receiving-end converter station, and the positive sequence component of the three-phase voltage dropped to 0.33pu. About 10ms after the fault, the receiving-end converter station detected the fault and immediately put into operation the DC energy consumption device connected in parallel to the high-end valve group, and notified the sending-end converter station to reduce power through inter-station communication, and the power command was 0.915pu. About 40ms after the fault, the sending-end converter station immediately reduced the active power to 0.915pu after receiving the power reduction command through inter-station communication. About 100ms after the fault, the fault of the AC system connected to the high-end valve group of the receiving-end converter station was cleared, and the positive sequence component of the three-phase voltage increased to 1pu. About 110ms after the fault, the receiving-end converter station detected that the fault on the AC side was cleared, and then exited the DC energy consumption device, and notified the sending-end converter station to restore the DC power to the previous value through inter-station communication. About 140ms after the fault, the sending-end converter station receives the power command through inter-station communication and restores the DC power to 1pu. Figure 3As shown in the figure, about 300ms after the fault, the voltage and power on the DC pole line basically return to the operating state before the fault. Figure 4 is the maximum voltage of the high-end converter valve submodule of the receiving station during the fault ride-through period, which does not exceed 2.8 kV and is lower than the overvoltage protection setting of the submodule. It can be seen that the energy consumption device configuration scheme and AC side fault ride-through method for the receiving-end layered ultra-high voltage flexible direct current transmission system provided by the present invention can realize system fault ride-through after a fault occurs on the AC side of the receiving station.

[0116] Example 2

[0117] Based on a typical ±800kV / 8GW receiving-end layered UHV flexible DC transmission system, its main circuit parameters are as follows: submodule rated working voltage 2.0kV, submodule capacitance 24mF, bridge arm reactor 25mH, current limiting reactor 300mH. The DC transmission line length is 2400km, using 6 split conductors, and the line resistance is about 10Ω. The UHV flexible DC transmission system adopts a true bipolar wiring scheme, with two valve groups cascaded per pole, and the DC voltage of each valve group is 400kV. The valve group adopts a full half-bridge hybrid module, and the full-bridge ratio is 60%. The communication delay between stations in the flexible DC system is 30ms. The receiving station is connected to the AC system through the high-end and low-end valve groups in a layered manner, that is, the high-end valves of the positive and negative poles are connected to one AC system, and the low-end valves of the positive and negative poles are connected to another AC system. The electrical distance between the two AC systems is relatively far, which can be approximated as two independent AC systems. The AC side of the sending-end converter station is in island mode, and the sending end adopts a fixed AC voltage amplitude and fixed AC frequency control strategy, while the receiving end adopts a fixed DC voltage and fixed reactive power control strategy. A 4GW DC energy consumption device is configured on the DC side of the receiving-end converter station, of which 1GW is configured between the positive pole line and the 400kV connecting busbar of the positive pole (that is, in parallel with the high-end valve group of the positive pole), 1GW is configured between the 400kV connecting busbar of the positive pole and the neutral line (that is, in parallel with the low-end valve group of the positive pole), 1GW is configured between the negative pole line and the 400kV connecting busbar of the negative pole (that is, in parallel with the high-end valve group of the negative pole), and 1GW is configured between the 400kV connecting busbar of the negative pole and the neutral line (that is, in parallel with the low-end valve group of the negative pole). A 2GW AC energy consumption device is configured on the AC side of the sending-end converter station, such as Figure 1B shown.

[0118] Before the fault occurs, the UHV flexible DC transmission system operates at full capacity. Figure 55.1s), a two-phase metallic grounding fault occurs in the AC system connected to the low-end valve group of the receiving-end converter station, and the positive sequence component of the three-phase voltage drops to 0.33pu. About 10ms after the fault, the receiving-end converter station detects the fault and immediately starts the DC energy consumption device connected in parallel to the low-end valve group, and notifies the sending-end converter station to start the AC energy consumption device through inter-station communication. The number of AC energy consumption devices put into operation is 3 groups. About 40ms after the fault, the sending-end converter station receives the instruction to start the AC energy consumption device through inter-station communication, and immediately starts the 3 groups of AC energy consumption devices. About 100ms after the fault, the fault of the AC system connected to the low-end valve group of the receiving-end converter station is cleared, and the positive sequence component of the three-phase voltage is increased to 1pu. About 110ms after the fault, the receiving-end converter station detects that the fault on the AC side is cleared, and then exits the DC energy consumption device, and notifies the sending-end converter station to exit the AC energy consumption device through inter-station communication. About 140ms after the fault, the sending-end converter station receives the instruction to exit the AC energy-consuming device through inter-station communication and then exits all the AC energy-consuming devices. Figure 5 As shown in the figure, about 300ms after the fault, the voltage and power on the DC pole line basically return to the operating state before the fault. Figure 6 is the maximum voltage of the low-end converter valve submodule of the receiving station during the fault ride-through period, which does not exceed 2.8kV and is lower than the overvoltage protection setting of the submodule. It can be seen that the energy consumption device configuration scheme and AC side fault ride-through method of the ultra-high voltage flexible direct current transmission system provided by the present invention can realize system fault ride-through after a fault occurs on the AC side of the receiving-end converter transformer.

[0119] In summary, the embodiments of the present application have at least the following beneficial effects:

[0120] By adopting the embodiment of the present application, on the premise that the receiving end side is configured to be connected to the AC system through valve group layering (that is, the first valve group and the fourth valve group are connected to one AC system, and the second valve group and the third valve group are connected to another AC system), the energy consumption device is also configured accordingly to adapt to the structure of the valve group layering, so that a small-capacity DC energy consumption module can be used to adapt to the changes in capacity requirements of different valve groups, so as to improve energy consumption efficiency and reduce the total capacity of energy consumption devices, thereby improving the overall economy of ultra-high voltage flexible DC transmission technology and improving system safety.

[0121] Through the description of the above implementation methods, those skilled in the art can clearly understand that the present application can be implemented by means of software plus the necessary hardware platform, and of course, it can also be implemented entirely by hardware. Based on such an understanding, all or part of the contribution of the technical solution of the present application to the background technology can be embodied in the form of a software product, and the computer software product can be stored in a storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment of the present application or some parts of the embodiments.

[0122] The above is a preferred embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications are also considered to be within the scope of protection of the present application.

Claims

1. An energy dissipation device suitable for an ultra-high voltage flexible direct current transmission system, characterized in that: The ultra-high voltage flexible direct current power transmission system has a receiving end side, and the receiving end side includes: a first valve group, a first end of which is electrically connected to the positive electrode line on the receiving end side, and a second end of which is electrically connected to the first AC system; A second valve group, a first end of which is electrically connected to the third end of the first valve group, a second end of which is electrically connected to the second AC system, and a third end of which is electrically connected to the neutral line on the receiving end side; A third valve group, a first end of which is electrically connected to the neutral line of the receiving end, and a second end of which is electrically connected to the second AC system; and a fourth valve group, a first end of which is electrically connected to the third end of the third valve group, a second end of which is electrically connected to the first AC system, and a third end of which is electrically connected to the negative electrode line on the receiving end side; Wherein, the energy consumption device comprises: A first DC energy consumption module, two ends of which are respectively electrically connected to the positive electrode line on the receiving end side, and between the third end of the first valve group and the first end of the second valve group; A second DC energy consumption module, two ends of which are respectively electrically connected to the neutral line on the receiving end side, and between the third end of the first valve group and the first end of the second valve group; A third DC energy consumption module, both ends of which are electrically connected to the neutral line of the receiving end side, and between the third end of the third valve group and the first end of the fourth valve group; and The fourth DC energy consumption module has two ends electrically connected to the negative pole line on the receiving end side, and between the third end of the third valve group and the first end of the fourth valve group.

2. The energy dissipation device according to claim 1, characterized in that: The total capacity of the energy consumption device is equal to the DC power transmission rated capacity of the receiving end multiplied by a set ratio, wherein the set ratio is less than 1, and the total capacity of the energy consumption device refers to the sum of the capacities of the first DC energy consumption module, the second DC energy consumption module, the third DC energy consumption module and the fourth DC energy consumption module.

3. The energy dissipation device according to claim 2, characterized in that: The first DC energy consumption module, the second DC energy consumption module, the third DC energy consumption module and the fourth DC energy consumption module have the same capacity; The setting ratio is 0.

5.

4. The energy dissipation device according to claim 1, characterized in that: At least one of the first valve group, the second valve group, the third valve group, and the fourth valve group is a full half-bridge hybrid module structure.

5. The energy consumption device according to claim 1, characterized in that: The UHV flexible DC power transmission system further comprises a sending end side, two ends of which are electrically connected to the positive pole line and the negative pole line of the receiving end side, respectively, wherein: When the AC side of the sending-end converter station in the sending-end side is in a networking mode, the sending-end side is configured to adopt a control strategy based on fixed active power and fixed reactive power to control its own power; When the AC side of the sending-end converter station in the sending-end side is in island mode, the AC side of the sending-end converter station is connected to an AC energy consumption device, wherein the AC energy consumption device is composed of multiple groups of AC energy consumption sub-devices configured in groups.

6. A fault control method, characterized in that: Applicable to the energy consumption device of claim 1, wherein the energy consumption device does not enter the energy consumption mode in a default state, and the method comprises: When a fault is detected in the first AC system, if the positive sequence component of the three-phase voltage of the first AC system is greater than or equal to a first threshold, the first DC energy consumption module and the fourth DC energy consumption module are controlled to enter an energy consumption mode, until it is detected that the fault is eliminated, and then the first DC energy consumption module and the fourth DC energy consumption module are controlled to exit the energy consumption mode; When a fault is detected in the second AC system, if the positive sequence component of the three-phase voltage of the second AC system is greater than or equal to a second threshold, the second DC energy consumption module and the third DC energy consumption module are controlled to enter an energy consumption mode until it is detected that the fault is eliminated, and then the second DC energy consumption module and the third DC energy consumption module are controlled to exit the energy consumption mode.

7. The method according to claim 6, characterized in that The UHV flexible direct current power transmission system further comprises a sending end side, two ends of the sending end side are respectively electrically connected to the positive pole line and the negative pole line of the receiving end side, and a sending end converter station is provided in the sending end side which is communicatively connected to the energy consumption device, and the method further comprises: When a fault is detected in the first AC system, if the positive sequence component of the three-phase voltage of the first AC system is less than the first threshold, the first DC energy consumption module and the fourth DC energy consumption module are controlled to enter an energy consumption mode, and according to the detected mode of the AC side of the sending-end converter station, a corresponding first sending-end control instruction is sent to the sending-end converter station, until it is detected that the fault is eliminated, the first DC energy consumption module and the fourth DC energy consumption module are controlled to exit the energy consumption mode, and a first cancellation instruction is sent to the sending-end converter station, wherein the first cancellation instruction is used to cancel the control of the first sending-end control instruction; When a fault is detected in the second AC system, if the positive sequence component of the three-phase voltage of the second AC system is less than the second threshold value, the second DC energy consumption module and the third DC energy consumption module are controlled to enter the energy consumption mode, and according to the detected mode of the AC side of the sending-end converter station, the corresponding second sending-end control instruction is sent to the sending-end converter station, until it is detected that the fault is eliminated, the second DC energy consumption module and the third DC energy consumption module are controlled to exit the energy consumption mode, and a second cancellation instruction is sent to the sending-end converter station, wherein the second cancellation instruction is used to cancel the control of the second sending-end control instruction.

8. The method according to claim 7, characterized in that The AC side of the sending-end converter station is connected to an AC energy consumption device, and the AC energy consumption device does not enter an energy consumption mode in a default state. The mode of the AC side of the sending-end converter station includes a networking mode or an island mode; When the AC side of the sending-end converter station is in the networking mode, the first sending-end control instruction is used to instruct the sending-end converter station to reduce the active power to a specified power value that matches the first sending-end control instruction, and the second sending-end control instruction is used to instruct the sending-end converter station to reduce the active power to a specified power value that matches the second sending-end control instruction; When the mode of the AC side of the sending-end converter station is the island mode, the first sending-end control instruction is used to instruct the sending-end converter station to control the AC energy consumption device to enter an energy consumption mode matching the first sending-end control instruction, and the second sending-end control instruction is used to instruct the sending-end converter station to control the AC energy consumption device to enter an energy consumption mode matching the second sending-end control instruction.

9. The method according to claim 8, characterized in that The specified power value P that matches the first sending end control instruction pu,1 It is expressed by the following formula: The specified power value P that matches the second sending end control instruction pu,2 It is expressed by the following formula: Among them, U ac,pu,1 is the per-unit value of the positive sequence component of the three-phase voltage of the first AC system after a fault occurs in the first AC system, U ac,pu,2 is the per-unit value of the decrease of the positive sequence component of the three-phase voltage of the second AC system after a fault occurs in the second AC system.

10. The method according to claim 8, characterized in that The AC energy consumption device is composed of multiple groups of AC energy consumption sub-devices configured in groups; in, The energy consumption mode matched with the first sending-end control instruction is suitable for indicating a first number of AC energy consumption sub-devices that need to enter the energy consumption mode, wherein the first number is determined according to a ratio of a decrease in a positive sequence component of a three-phase voltage of the first AC system after a fault occurs in the first AC system; The energy consumption mode matching the second sending-end control instruction is suitable for indicating the second number of AC energy consumption sub-devices that need to enter the energy consumption mode, and the second number is determined based on the proportion of the decrease in the positive sequence component of the three-phase voltage of the second AC system after a fault occurs in the second AC system.

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