Fault control method and system of direct current power transmission system

Abstract

The invention discloses a fault control method and system for a direct-current power transmission system, and the method comprises the steps: transmitting an opening instruction to an energy consumption device when a receiving-end converter station detects that the alternating-current side of the receiving-end converter station has a fault, and transmitting a closing instruction to the energy consumption device when the receiving-end converter station detects that the fault is eliminated, the starting instruction is used for starting the energy consumption device and maintaining operation, the energy consumption device is used for consuming at least part of direct current during operation, the at least part of direct current is at least part of direct current received by the receiving end converter station, and the closing instruction is used for closing the energy consumption device; and when the sending-end converter station detects that the electrical parameter information of a sending-end converter valve arranged in the sending-end converter station meets a set fault condition, the power of the direct current transmitted to the receiving-end converter station is continuously reduced, and the power of the direct current transmitted to the receiving-end converter station is maintained until the electrical parameter information is detected to meet a set maintenance condition. Therefore, the safety and economical efficiency 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 direct current transmission, and in particular to a fault control method and system for a direct current transmission system. Background Art

[0002] At present, since the distance between the two ends of the UHV flexible DC transmission technology is generally more than 2000km, for the UHV flexible DC system with ultra-long transmission distance, when the AC system on the receiving side has a transient fault, it is easy to cause significant surplus power on the receiving side. In particular, when the communication between stations is lost, the sending-end converter station cannot promptly know the operating status of the receiving-end converter station, which may cause more serious power surplus problems, and may further trigger protection lockout or even shutdown of the UHV flexible DC transmission system, causing serious economic losses and safety hazards. Summary of the invention

[0003] In order to solve the above technical problems, the embodiments of the present application propose a fault control method and system for a direct current transmission system, which can improve the safety and economy of the ultra-high voltage flexible direct current transmission system.

[0004] The embodiment of the present application provides a fault control method for a direct current transmission system, wherein the direct current transmission system includes a receiving-end converter station, a sending-end converter station, and an energy consumption device, and the method includes:

[0005] When the receiving-end converter station detects that a fault occurs on its AC side, it sends an opening instruction to the energy consumption device, and when it detects that the fault is eliminated, it sends a closing instruction to the energy consumption device, wherein the opening instruction is used to open the energy consumption device and maintain operation, the energy consumption device is used to consume at least part of the DC power during operation, and the at least part of the DC power is at least part of the DC power received by the receiving-end converter station, and the closing instruction is used to close the energy consumption device;

[0006] When the sending-end converter station detects that the electrical parameter information of the sending-end converter valve provided therein meets the set fault condition, the power of the DC power delivered to the receiving-end converter station is continuously reduced until it is detected that the electrical parameter information meets the set maintenance condition, and then the power of the DC power delivered to the receiving-end converter station is maintained.

[0007] Optionally, the method further comprises:

[0008] After detecting that the electrical parameter information satisfies the set maintenance conditions, the sending-end converter station increases the power of the direct current supplied to the receiving-end converter station until it reaches the target power value when detecting that the electrical parameter information satisfies the set fault removal conditions.

[0009] Optionally, the electrical parameter information includes the terminal voltage of the sending-end converter valve;

[0010] The set fault condition includes: the terminal voltage exceeds a set threshold and the terminal voltage increases with time;

[0011] The set maintenance condition includes: the terminal voltage exceeds the set threshold value and the terminal voltage does not increase with time;

[0012] The set fault relief condition includes: the terminal voltage is lower than the set threshold.

[0013] Optionally, the continuously reducing the power of the direct current delivered to the receiving-end converter station includes:

[0014] The power of the direct current supplied to the receiving-end converter station is continuously reduced at a first rate, wherein the first rate is constant.

[0015] Optionally, increasing the power of the direct current delivered to the receiving-end converter station includes:

[0016] The power of the direct current supplied to the receiving-end converter station is increased at a second rate, wherein the second rate is constant.

[0017] Optionally, the target power value includes:

[0018] Preset rated power value;

[0019] or,

[0020] The power value of the direct current delivered to the receiving-end converter station at a moment before it is detected that the electrical parameter information meets the set fault condition.

[0021] Optionally, the receiving-end converter station includes N valve groups, each of the N valve groups is connected to the same AC system, wherein:

[0022] M valve groups are connected in series between the positive pole line and the neutral line of the receiving end converter station, N≥2, M<N;

[0023] (NM) valve groups are connected in series between the neutral line and the negative pole line of the receiving-end converter station, and the (NM) valve groups are each valve group among the N valve groups except the M valve groups;

[0024] The positive pole line and the negative pole line of the receiving-end converter station are electrically connected to the two ends of the sending-end converter station respectively.

[0025] Optionally, the energy consumption device includes:

[0026] A first DC energy consumption module, two ends of which are electrically connected to the positive pole line and the neutral line of the receiving-end converter station respectively; and

[0027] The second DC energy consumption module has two ends electrically connected to the neutral line and the negative pole line of the receiving-end converter station respectively.

[0028] Optionally, the N valve groups are:

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

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

[0031] A third valve group, a first end of which is electrically connected to the neutral line of the receiving-end converter station, and a second end of which is electrically connected to the AC system; and

[0032] The fourth valve group has a first end electrically connected to the third end of the third valve group, a second end electrically connected to the AC system, and a third end electrically connected to the negative pole line of the receiving-end converter station.

[0033] Optionally, each of the N valve groups adopts a full half-bridge hybrid module structure.

[0034] The embodiment of the present application also provides a fault control system for a DC power transmission system, wherein the DC power transmission system includes a receiving-end converter station, a sending-end converter station, and an energy consumption device;

[0035] The receiving-end converter station is configured to send an opening instruction to the energy consumption device when a fault is detected on its AC side, and to send a closing instruction to the energy consumption device when it is detected that the fault is eliminated, wherein the opening instruction is used to turn on the energy consumption device and maintain operation, the energy consumption device is used to consume at least part of the DC power during operation, and the at least part of the DC power is at least part of the DC power received by the receiving-end converter station, and the closing instruction is used to turn off the energy consumption device;

[0036] The sending-end converter station is configured to continuously reduce the power of the DC power delivered to the receiving-end converter station when it detects that the electrical parameter information of the sending-end converter valve provided therein meets the set fault condition, and maintain the power of the DC power delivered to the receiving-end converter station after it detects that the electrical parameter information meets the set maintenance condition.

[0037] Optionally, the sending-end converter station is also configured to increase the power of the direct current delivered to the receiving-end converter station until it reaches a target power value after detecting that the electrical parameter information satisfies a set maintenance condition and when detecting that the electrical parameter information satisfies a set fault removal condition.

[0038] Optionally, the electrical parameter information includes the terminal voltage of the sending-end converter valve;

[0039] The set fault condition includes: the terminal voltage exceeds a set threshold and the terminal voltage increases with time;

[0040] The set maintenance condition includes: the terminal voltage exceeds the set threshold value and the terminal voltage does not increase with time;

[0041] The set fault relief condition includes: the terminal voltage is lower than the set threshold.

[0042] Optionally, the continuously reducing the power of the direct current delivered to the receiving-end converter station includes:

[0043] The power of the direct current supplied to the receiving-end converter station is continuously reduced at a first rate, wherein the first rate is constant.

[0044] Optionally, increasing the power of the direct current delivered to the receiving-end converter station includes:

[0045] The power of the direct current supplied to the receiving-end converter station is increased at a second rate, wherein the second rate is constant.

[0046] Optionally, the target power value includes:

[0047] Preset rated power value;

[0048] or,

[0049] The power value of the direct current delivered to the receiving-end converter station at a moment before it is detected that the electrical parameter information meets the set fault condition.

[0050] Optionally, the receiving-end converter station includes N valve groups, each of the N valve groups is connected to the same AC system, wherein:

[0051] M valve groups are connected in series between the positive pole line and the neutral line of the receiving end converter station, N≥2, M<N;

[0052] (NM) valve groups are connected in series between the neutral line and the negative pole line of the receiving-end converter station, and the (NM) valve groups are each valve group among the N valve groups except the M valve groups;

[0053] The positive pole line and the negative pole line of the receiving-end converter station are electrically connected to the two ends of the sending-end converter station respectively.

[0054] Optionally, the energy consumption device includes:

[0055] A first DC energy consumption module, two ends of which are electrically connected to the positive pole line and the neutral line of the receiving-end converter station respectively; and

[0056] The second DC energy consumption module has two ends electrically connected to the neutral line and the negative pole line of the receiving-end converter station respectively.

[0057] Optionally, the N valve groups are:

[0058] a first valve group, a first end of which is electrically connected to the positive pole line of the receiving-end converter station, and a second end of which is electrically connected to the AC system;

[0059] a second valve group, wherein a first end is electrically connected to a third end of the first valve group, a second end is electrically connected to the AC system, and a third end is electrically connected to a neutral line of the receiving-end converter station;

[0060] A third valve group, a first end of which is electrically connected to the neutral line of the receiving-end converter station, and a second end of which is electrically connected to the AC system; and

[0061] The fourth valve group has a first end electrically connected to the third end of the third valve group, a second end electrically connected to the AC system, and a third end electrically connected to the negative pole line of the receiving-end converter station.

[0062] Optionally, each of the N valve groups adopts a full half-bridge hybrid module structure.

[0063] In summary, the embodiments of the present application have at least the following beneficial effects:

[0064] According to an embodiment of the present application, the DC power transmission system includes a receiving-end converter station, a sending-end converter station and an energy consumption device, and the method includes: when the receiving-end converter station detects that a fault occurs on its AC side, the receiving-end converter station sends an opening instruction to the energy consumption device, and when it is detected that the fault is eliminated, the closing instruction is sent to the energy consumption device, wherein the opening instruction is used to open the energy consumption device and maintain operation, and the energy consumption device is used to consume at least part of the DC power during operation, and the at least part of the DC power is at least part of the DC power received by the receiving-end converter station, and the closing instruction is used to close the energy consumption device; when the sending-end converter station detects that the electrical parameter information of the sending-end converter valve provided therein meets the set fault condition, the power of the DC power delivered to the receiving-end converter station is continuously reduced until it is detected that the electrical parameter information meets the set maintenance condition, and the power of the DC power delivered to the receiving-end converter station is maintained, thereby improving the safety and economy of the ultra-high voltage flexible DC power transmission system. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 is a flow chart of a fault control method for a DC power transmission system provided in an embodiment of the present application;

[0066] Figure 2 It is a structural schematic diagram of the ultra-high voltage flexible direct current transmission system provided in an embodiment of the present application;

[0067] Figure 3 is a schematic diagram of electrical parameter information on a DC pole line during a fault provided by an embodiment of the present application;

[0068] Figure 4 It is a schematic diagram of the maximum voltage of the receiving-end converter valve submodule during a fault provided in an embodiment of the present application. DETAILED DESCRIPTION

[0069] 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.

[0070] 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".

[0071] 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.

[0072] 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.

[0073] See also Figure 1 , shows a flow chart of a fault control method for a DC power transmission system provided by an embodiment of the present application, wherein the DC power transmission system comprises a receiving-end converter station, a sending-end converter station and an energy consumption device, wherein the sending-end converter station is used to transmit DC power to the receiving-end converter station, and the energy consumption device is electrically connected to the receiving-end converter station and is closed by default, and the method comprises steps S101-S102, which are specifically as follows:

[0074] S101, when the receiving-end converter station detects that a fault occurs on its AC side, the receiving-end converter station sends an opening instruction to the energy consumption device, and when it is detected that the fault is eliminated, the receiving-end converter station sends a closing instruction to the energy consumption device, wherein the opening instruction is used to open the energy consumption device and maintain operation, the energy consumption device is used to consume at least part of the DC power during operation, the at least part of the DC power is at least part of the DC power received by the receiving-end converter station, and the closing instruction is used to close the energy consumption device;

[0075] S102, when the sending-end converter station detects that the electrical parameter information of the sending-end converter valve provided therein meets the set fault condition, the power of the DC power delivered to the receiving-end converter station is continuously reduced until it is detected that the electrical parameter information meets the set maintenance condition, and then the power of the DC power delivered to the receiving-end converter station is maintained.

[0076] It can be understood that the sending-end converter station and the receiving-end converter station in this embodiment each need to detect different information to determine whether a fault has occurred, and each detects independently. Therefore, there is no need to rely on communication interaction between the sending-end converter station and the receiving-end converter station to inform each other whether a fault has occurred. This is more effective for addressing serious power surplus problems caused by loss of communication between stations.

[0077] Exemplarily, the DC transmission system in this embodiment can be a typical ±800kV / 8GW ultra-high voltage flexible DC transmission system, and 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 ultra-high voltage flexible DC transmission system adopts a true bipolar wiring scheme, each pole is cascaded by two valve groups, 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 AC side of the sending end converter station is a 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.

[0078] In an optional embodiment, the method further includes:

[0079] After detecting that the electrical parameter information satisfies the set maintenance conditions, the sending-end converter station increases the power of the direct current supplied to the receiving-end converter station until it reaches the target power value when detecting that the electrical parameter information satisfies the set fault removal conditions.

[0080] In an optional implementation, the electrical parameter information includes the terminal voltage of the sending-end converter valve;

[0081] The set fault condition includes: the terminal voltage exceeds a set threshold and the terminal voltage increases with time;

[0082] The set maintenance condition includes: the terminal voltage exceeds the set threshold value and the terminal voltage does not increase with time;

[0083] The set fault relief condition includes: the terminal voltage is lower than the set threshold.

[0084] Exemplarily, the set threshold in this embodiment may be 1.05 pu.

[0085] In an optional implementation manner, the continuously reducing the power of the direct current delivered to the receiving-end converter station includes:

[0086] The power of the direct current supplied to the receiving-end converter station is continuously reduced at a first rate, wherein the first rate is constant.

[0087] Exemplarily, the first rate in this embodiment may be 50 MW / ms.

[0088] In an optional implementation manner, increasing the power of the direct current delivered to the receiving-end converter station includes:

[0089] The power of the direct current supplied to the receiving-end converter station is increased at a second rate, wherein the second rate is constant.

[0090] Exemplarily, the second rate in this embodiment may be 50 MW / ms.

[0091] In summary of the above embodiments, when the sending-end converter station detects that the terminal voltage of the sending-end converter valve exceeds 1.05pu, the DC power transmitted to the receiving-end converter station is immediately reduced at a rate of 50MW / ms until the terminal voltage of the sending-end converter valve no longer increases (i.e., reaches a maximum value); when the terminal voltage of the sending-end converter valve starts to decrease from the maximum value, the DC power transmitted from the sending-end converter station to the receiving-end converter station remains unchanged; when the terminal voltage of the sending-end converter valve decreases to less than 1.05pu, the sending-end converter station immediately increases the DC power transmitted to the receiving-end converter station at a rate of 50MW / ms until the DC power reaches the rated value or the previous value, thereby achieving the receiving-end converter station and the sending-end converter station without relying on inter-station communication to exchange information.

[0092] In an optional implementation manner, the target power value includes:

[0093] Preset rated power value;

[0094] or,

[0095] The power value of the direct current delivered to the receiving-end converter station at a moment before it is detected that the electrical parameter information meets the set fault condition.

[0096] In an optional implementation, the receiving-end converter station includes N valve groups, each of the N valve groups is connected to the same AC system, wherein:

[0097] M valve groups are connected in series between the positive pole line and the neutral line of the receiving end converter station, N≥2, M<N;

[0098] (NM) valve groups are connected in series between the neutral line and the negative pole line of the receiving-end converter station, and the (NM) valve groups are each valve group among the N valve groups except the M valve groups;

[0099] The positive pole line and the negative pole line of the receiving-end converter station are electrically connected to the two ends of the sending-end converter station respectively.

[0100] In an alternative embodiment, see Figure 2 , the energy consumption device comprises:

[0101] The first DC energy consumption module 111 has two ends electrically connected to the positive pole line and the neutral line of the receiving-end converter station respectively; and

[0102] The second DC energy consumption module 112 has two ends electrically connected to the neutral line and the negative pole line of the receiving-end converter station respectively.

[0103] In some cases, a DC energy consumption device with a total capacity of 4GW can be configured on the DC side of the receiving converter station, where:

[0104] The first DC energy consumption module has a capacity of 2GW and is configured between the positive pole line and the neutral line;

[0105] The second DC energy consumption module has a capacity of 2GW and is configured between the negative pole line and the neutral line;

[0106] In this way, the capacity of the DC energy dissipation device is only 50% of the rated capacity of the DC power transmission system. The above-mentioned DC energy dissipation device can be constructed using a variety of technical routes such as centralized, distributed or hybrid.

[0107] In an optional implementation, the N valve groups are:

[0108] A first valve group 121, a first end of which is electrically connected to the positive pole line of the receiving-end converter station, and a second end of which is electrically connected to the AC system 131;

[0109] A second valve group 122, 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 131, and a third end of which is electrically connected to a neutral line of the receiving-end converter station;

[0110] A third valve group 123, a first end of which is electrically connected to the neutral line of the receiving-end converter station, and a second end of which is electrically connected to the AC system 131; and

[0111] The fourth valve group 124 has a first end electrically connected to the third end of the third valve group, a second end electrically connected to the AC system 131, and a third end electrically connected to the negative pole line of the receiving-end converter station.

[0112] In an optional implementation, each of the N valve groups adopts a full half-bridge hybrid module structure.

[0113] The embodiment of the present application also provides a fault control system for a DC power transmission system, wherein the DC power transmission system includes a receiving-end converter station, a sending-end converter station, and an energy consumption device;

[0114] The receiving-end converter station is configured to send an opening instruction to the energy consumption device when a fault is detected on its AC side, and to send a closing instruction to the energy consumption device when it is detected that the fault is eliminated, wherein the opening instruction is used to turn on the energy consumption device and maintain operation, the energy consumption device is used to consume at least part of the DC power during operation, and the at least part of the DC power is at least part of the DC power received by the receiving-end converter station, and the closing instruction is used to turn off the energy consumption device;

[0115] The sending-end converter station is configured to continuously reduce the power of the DC power delivered to the receiving-end converter station when it detects that the electrical parameter information of the sending-end converter valve provided therein meets the set fault condition, and maintain the power of the DC power delivered to the receiving-end converter station after it detects that the electrical parameter information meets the set maintenance condition.

[0116] In an optional embodiment, the sending-end converter station is further configured to increase the power of the direct current delivered to the receiving-end converter station until it reaches the target power value after detecting that the electrical parameter information satisfies the set maintenance conditions and when detecting that the electrical parameter information satisfies the set fault removal conditions.

[0117] In an optional implementation, the electrical parameter information includes the terminal voltage of the sending-end converter valve;

[0118] The set fault condition includes: the terminal voltage exceeds a set threshold and the terminal voltage increases with time;

[0119] The set maintenance condition includes: the terminal voltage exceeds the set threshold value and the terminal voltage does not increase with time;

[0120] The set fault relief condition includes: the terminal voltage is lower than the set threshold.

[0121] In an optional implementation manner, the continuously reducing the power of the direct current delivered to the receiving-end converter station includes:

[0122] The power of the direct current supplied to the receiving-end converter station is continuously reduced at a first rate, wherein the first rate is constant.

[0123] In an optional implementation manner, increasing the power of the direct current delivered to the receiving-end converter station includes:

[0124] The power of the direct current supplied to the receiving-end converter station is increased at a second rate, wherein the second rate is constant.

[0125] In an optional implementation manner, the target power value includes:

[0126] Preset rated power value;

[0127] or,

[0128] The power value of the direct current delivered to the receiving-end converter station at a moment before it is detected that the electrical parameter information meets the set fault condition.

[0129] In an optional implementation, the receiving-end converter station includes N valve groups, each of the N valve groups is connected to the same AC system, wherein:

[0130] M valve groups are connected in series between the positive pole line and the neutral line of the receiving end converter station, N≥2, M<N;

[0131] (NM) valve groups are connected in series between the neutral line and the negative pole line of the receiving-end converter station, and the (NM) valve groups are each valve group among the N valve groups except the M valve groups;

[0132] The positive pole line and the negative pole line of the receiving-end converter station are electrically connected to the two ends of the sending-end converter station respectively.

[0133] In an alternative embodiment, see Figure 2 , the energy consumption device comprises:

[0134] The first DC energy consumption module 111 has two ends electrically connected to the positive pole line and the neutral line of the receiving-end converter station respectively; and

[0135] The second DC energy consumption module 112 has two ends electrically connected to the neutral line and the negative pole line of the receiving-end converter station respectively.

[0136] In an alternative embodiment, see Figure 2 , the N valve groups are respectively:

[0137] A first valve group 121, a first end of which is electrically connected to the positive pole line of the receiving-end converter station, and a second end of which is electrically connected to the AC system 131;

[0138] A second valve group 122, 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 131, and a third end of which is electrically connected to a neutral line of the receiving-end converter station;

[0139] A third valve group 123, a first end of which is electrically connected to the neutral line of the receiving-end converter station, and a second end of which is electrically connected to the AC system 131; and

[0140] The fourth valve group 124 has a first end electrically connected to the third end of the third valve group, a second end electrically connected to the AC system 131, and a third end electrically connected to the negative pole line of the receiving-end converter station.

[0141] In an optional implementation, each of the N valve groups adopts a full half-bridge hybrid module structure.

[0142] A specific embodiment is given below.

[0143] Based on a typical ±800kV / 8GW ultra-high voltage flexible direct current 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 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 AC side of the sending-end converter station is in a networking mode, and 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 2GW is configured between the positive pole line and the neutral line, and another 2GW is configured between the negative pole line and the neutral line, such as Figure 2 shown.

[0144] Before the fault occurs, the UHV flexible DC transmission system operates at full capacity. Figure 3 The figure is 5.1s, in which U_P1, I_P1, and P_P1 are the voltage, current, and power on the positive polarity transmission line, respectively, and U_P2, I_P2, and P_P2 are the voltage, current, and power on the negative polarity transmission line, respectively. A three-phase metallic grounding fault occurs on the AC side of the receiving-end converter. About 10ms after the fault, the receiving-end converter station detects the fault and immediately puts the DC energy consumption device into operation. About 20ms after the fault, the terminal voltage of the sending-end converter valve (i.e., the voltage difference between U_P1 and U_P2) exceeds 1.05pu, and the sending-end converter station immediately reduces the DC current (i.e., I_P1 or I_P2, it should be understood that I_P1=I_P2 in the same circuit) and DC power (i.e., the difference between P_P1 and P_P2) transmitted to the receiving-end converter station at a rate of 50MW / ms. About 80ms after the fault, the terminal voltage of the sending-end converter valve reaches the maximum value and gradually decreases from the maximum value. The DC power transmitted from the sending-end converter station to the receiving-end converter station remains unchanged. About 100ms after the fault, the AC side fault of the receiving-end converter station is cleared. About 110ms after the fault, the receiving-end converter station detects that the AC side fault has been cleared and exits the DC energy consumption device. About 130ms after the fault, the terminal voltage of the sending-end converter valve drops to below 1.05pu. The sending-end converter station immediately increases the DC power transmitted to the receiving-end converter station at a rate of 50MW / ms until the DC power reaches 1pu. Figure 3 As shown, about 350ms after the fault, the voltage, current and power on the DC pole line basically return to the operating state before the fault. Figure 4The maximum voltage of the receiving station converter valve submodule during the fault ride-through period is a three-phase voltage and includes: Va1, Va3, Vb1, Vb3, Vc1, Vc3, which are respectively the maximum voltage of the submodule of the upper bridge arm of phase a, the maximum voltage of the submodule of the lower bridge arm of phase a, the maximum voltage of the submodule of the upper bridge arm of phase b, the maximum voltage of the submodule of the lower bridge arm of phase b, the maximum voltage of the submodule of the upper bridge arm of phase c, and the maximum voltage of the submodule of the lower bridge arm of phase c, all of which do not exceed 2.8kV, which 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 ultra-high voltage flexible direct current transmission system with inter-station communication loss provided by the present invention can realize system fault ride-through after a fault occurs on the AC side of the receiving terminal converter transformer.

[0145] In summary, the embodiments of the present application have at least the following beneficial effects:

[0146] According to an embodiment of the present application, the DC power transmission system includes a receiving-end converter station, a sending-end converter station and an energy consumption device, wherein the sending-end converter station is used to transmit DC power to the receiving-end converter station, and the energy consumption device is electrically connected to the receiving-end converter station and is closed by default. The method includes: when the receiving-end converter station detects that a fault occurs on its AC side, the receiving-end converter station sends an opening instruction to the energy consumption device, and when it is detected that the fault is eliminated, the receiving-end converter station sends a closing instruction to the energy consumption device, wherein the opening instruction is used to turn on the energy consumption device and maintain operation, and the energy consumption device is used to At least part of the DC power is consumed during operation, and the at least part of the DC power is at least part of the DC power received by the receiving-end converter station. The shutdown instruction is used to shut down the energy consumption device; when the sending-end converter station detects that the electrical parameter information of the sending-end converter valve provided therein meets the set fault condition, the power of the DC power delivered to the receiving-end converter station is continuously reduced until it is detected that the electrical parameter information meets the set maintenance condition, and the power of the DC power delivered to the receiving-end converter station is maintained, thereby improving the safety and economy of the ultra-high voltage flexible DC power transmission system.

[0147] 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.

[0148] 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. A fault control method for a direct current transmission system, characterized in that: The DC power transmission system comprises a receiving-end converter station, a sending-end converter station and an energy consumption device, and the method comprises: When the receiving-end converter station detects that a fault occurs on its AC side, it sends an opening instruction to the energy consumption device, and when it detects that the fault is eliminated, it sends a closing instruction to the energy consumption device, wherein the opening instruction is used to open the energy consumption device and maintain operation, the energy consumption device is used to consume at least part of the DC power during operation, and the at least part of the DC power is at least part of the DC power received by the receiving-end converter station, and the closing instruction is used to close the energy consumption device; When the sending-end converter station detects that the electrical parameter information of the sending-end converter valve provided therein meets the set fault condition, the power of the DC power delivered to the receiving-end converter station is continuously reduced until it is detected that the electrical parameter information meets the set maintenance condition, and then the power of the DC power delivered to the receiving-end converter station is maintained.

2. The method according to claim 1, characterized in that The method further comprises: After detecting that the electrical parameter information satisfies the set maintenance conditions, the sending-end converter station increases the power of the direct current supplied to the receiving-end converter station until it reaches the target power value when detecting that the electrical parameter information satisfies the set fault removal conditions.

3. The method according to claim 2, characterized in that The electrical parameter information includes the terminal voltage of the sending-end converter valve; The set fault condition includes: the terminal voltage exceeds a set threshold and the terminal voltage increases with time; The set maintenance condition includes: the terminal voltage exceeds the set threshold value and the terminal voltage does not increase with time; The set fault relief condition includes: the terminal voltage is lower than the set threshold.

4. The method according to claim 1, characterized in that The continuously reducing the power of the direct current transmitted to the receiving-end converter station comprises: The power of the direct current supplied to the receiving-end converter station is continuously reduced at a first rate, wherein the first rate is constant.

5. The method according to claim 2, characterized in that The step of increasing the power of the direct current supplied to the receiving-end converter station comprises: The power of the direct current supplied to the receiving-end converter station is increased at a second rate, wherein the second rate is constant.

6. The method according to claim 2, characterized in that The target power value includes: Preset rated power value; or, The power value of the direct current delivered to the receiving-end converter station at a moment before it is detected that the electrical parameter information meets the set fault condition.

7. The method according to any one of claims 1 to 6, characterized in that: The receiving-end converter station includes N valve groups, each of which is connected to the same AC system, wherein: M valve groups are connected in series between the positive pole line and the neutral line of the receiving end converter station, N≥2, M<N; (NM) valve groups are connected in series between the neutral line and the negative pole line of the receiving-end converter station, and the (NM) valve groups are each valve group among the N valve groups except the M valve groups; The positive pole line and the negative pole line of the receiving-end converter station are electrically connected to the two ends of the sending-end converter station respectively.

8. The method according to claim 7, characterized in that The energy consumption device comprises: A first DC energy consumption module, two ends of which are electrically connected to the positive pole line and the neutral line of the receiving-end converter station respectively; and The second DC energy consumption module has two ends electrically connected to the neutral line and the negative pole line of the receiving-end converter station respectively.

9. The method according to claim 7, characterized in that The N valve groups are: a first valve group, a first end of which is electrically connected to the positive pole line of the receiving-end converter station, and a second end of which is electrically connected to the AC system; a second valve group, wherein a first end is electrically connected to a third end of the first valve group, a second end is electrically connected to the AC system, and a third end is electrically connected to a neutral line of the receiving-end converter station; A third valve group, a first end of which is electrically connected to the neutral line of the receiving-end converter station, and a second end of which is electrically connected to the AC system; and The fourth valve group has a first end electrically connected to the third end of the third valve group, a second end electrically connected to the AC system, and a third end electrically connected to the negative pole line of the receiving-end converter station.

10. The method according to claim 7, characterized in that Each of the N valve groups adopts a full half-bridge hybrid module structure.

11. A fault control system for a direct current transmission system, characterized in that: The DC power transmission system includes a receiving-end converter station, a sending-end converter station and an energy consumption device; The receiving-end converter station is configured to send an opening instruction to the energy consumption device when a fault is detected on its AC side, and to send a closing instruction to the energy consumption device when it is detected that the fault is eliminated, wherein the opening instruction is used to turn on the energy consumption device and maintain operation, the energy consumption device is used to consume at least part of the DC power during operation, and the at least part of the DC power is at least part of the DC power received by the receiving-end converter station, and the closing instruction is used to turn off the energy consumption device; The sending-end converter station is configured to continuously reduce the power of the DC power delivered to the receiving-end converter station when it detects that the electrical parameter information of the sending-end converter valve provided therein meets the set fault condition, and maintain the power of the DC power delivered to the receiving-end converter station after it detects that the electrical parameter information meets the set maintenance condition.

12. The system according to claim 11, characterized in that The sending-end converter station is also configured to increase the power of the direct current delivered to the receiving-end converter station until it reaches the target power value after detecting that the electrical parameter information satisfies the set maintenance conditions and when detecting that the electrical parameter information satisfies the set fault removal conditions.

13. The system of claim 12, wherein: The electrical parameter information includes the terminal voltage of the sending-end converter valve; The set fault condition includes: the terminal voltage exceeds a set threshold and the terminal voltage increases with time; The set maintenance condition includes: the terminal voltage exceeds the set threshold value and the terminal voltage does not increase with time; The set fault relief condition includes: the terminal voltage is lower than the set threshold.

14. The system according to claim 11, characterized in that The continuously reducing the power of the direct current transmitted to the receiving-end converter station comprises: The power of the direct current supplied to the receiving-end converter station is continuously reduced at a first rate, wherein the first rate is constant.

15. The system of claim 12, wherein: The step of increasing the power of the direct current supplied to the receiving-end converter station comprises: The power of the direct current supplied to the receiving-end converter station is increased at a second rate, wherein the second rate is constant.

16. The system of claim 12, wherein: The target power value includes: Preset rated power value; or, The power value of the direct current delivered to the receiving-end converter station at a moment before it is detected that the electrical parameter information meets the set fault condition.

17. The system according to any one of claims 11 to 16, characterized in that: The receiving-end converter station includes N valve groups, each of which is connected to the same AC system, wherein: M valve groups are connected in series between the positive pole line and the neutral line of the receiving end converter station, N≥2, M<N; (NM) valve groups are connected in series between the neutral line and the negative pole line of the receiving-end converter station, and the (NM) valve groups are each valve group among the N valve groups except the M valve groups; The positive pole line and the negative pole line of the receiving-end converter station are electrically connected to the two ends of the sending-end converter station respectively.

18. The system of claim 17, wherein: The energy consumption device comprises: A first DC energy consumption module, two ends of which are electrically connected to the positive pole line and the neutral line of the receiving-end converter station respectively; and The second DC energy consumption module has two ends electrically connected to the neutral line and the negative pole line of the receiving-end converter station respectively.

19. The system of claim 17, wherein: The N valve groups are: a first valve group, a first end of which is electrically connected to the positive pole line of the receiving-end converter station, and a second end of which is electrically connected to the AC system; a second valve group, wherein a first end is electrically connected to a third end of the first valve group, a second end is electrically connected to the AC system, and a third end is electrically connected to a neutral line of the receiving-end converter station; A third valve group, a first end of which is electrically connected to the neutral line of the receiving-end converter station, and a second end of which is electrically connected to the AC system; and The fourth valve group has a first end electrically connected to the third end of the third valve group, a second end electrically connected to the AC system, and a third end electrically connected to the negative pole line of the receiving-end converter station.

20. The system of claim 17, wherein: Each of the N valve groups adopts a full half-bridge hybrid module structure.

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