Fault clearing device and ultra-long-distance multi-end output direct current side fault clearing method

Abstract

The invention relates to a fault clearing device and an ultra-long-distance multi-terminal transmission direct current side fault clearing method, device and equipment, which are applied to a multi-terminal flexible direct current system, the multi-terminal flexible direct current system comprises a plurality of transmission modules, and each transmission module comprises two converter stations and a grounding electrode line. The two converter stations are respectively connected with a grounding electrode line and then connected with a grounding electrode, the fault clearing device comprises a grounding unit connected to the grounding electrode line, the grounding unit comprises a transformer, a lightning arrester and a resistor, and the lightning arrester and the resistor are connected in series and then connected with the secondary side of the transformer; the lightning arrester is used for controlling the input and removal of the resistor; the resistor is used for consuming energy. The fault clearing device is connected to a sending-out module of the multi-terminal flexible direct-current system in a high-resistance grounding mode, after the multi-terminal flexible direct-current system has a direct-current fault, due to the existence of grounding high resistance, fault current is reduced, energy generated after the fault is consumed rapidly through the resistance, and therefore the purpose of clearing the fault current is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of direct current fault clearing, and in particular to a fault clearing device and a method, device and equipment for clearing direct current side faults transmitted over ultra-long distances and multiple terminals. Background Art

[0002] At present, flexible DC has become a preferred topology for large-scale ultra-long-distance transmission of new energy. Ultra-long-distance transmission often uses overhead lines, mainly because overhead lines are relatively cheap. The use of overhead lines makes it difficult to avoid the occurrence of faults such as wildfires and lightning strikes, which leads to frequent faults on DC lines. In order to ensure the safe and stable operation of AC and DC systems, it is necessary to ensure that the DC transmission system has good overhead line clearing capabilities.

[0003] Existing flexible DC mostly adopts a full-half-bridge hybrid structure to solve the DC fault clearing problem. However, in the process of the full-bridge module outputting reverse voltage, the fault current will continuously charge the capacitor of the full-bridge module, thereby causing the capacitor voltage of the full-bridge module to increase. When it increases to a certain level, it will cause the converter to trip. Summary of the invention

[0004] The embodiments of the present application provide a fault clearing device and a method, device and equipment for clearing faults on the DC side of ultra-long-distance multi-terminal transmission, which are used to solve the technical problem that the existing flexible DC uses a full half-bridge hybrid structure to clear DC faults, but this method has the problem of converter tripping and causing unstable operation of flexible DC transmission.

[0005] In order to achieve the above objectives, the embodiments of the present application provide the following technical solutions:

[0006] On the one hand, a fault clearing device is provided, which is applied to a multi-terminal flexible DC system, wherein the multi-terminal flexible DC system includes multiple sending modules, each of the sending modules includes two converter stations and a grounding electrode line, the two converter stations are respectively connected to the grounding electrode line and then connected to the grounding electrode, the fault clearing device includes a grounding unit connected to the grounding electrode line, the grounding unit includes a transformer, a lightning arrester and a resistor, the primary side of the transformer is respectively connected to the grounding electrode and the grounding electrode line, the lightning arrester is connected in series with the resistor and then connected to the secondary side of the transformer; the lightning arrester is used to control the input and output of the resistor; the resistor is used to consume energy.

[0007] On the other hand, a method for clearing a DC fault with ultra-long-distance multi-terminal transmission is provided, which is applied to the above-mentioned fault clearing device. The method for clearing a DC fault includes the following steps:

[0008] Obtain the electrical quantity parameters of the multi-terminal flexible DC system and the operating status of each transmission module;

[0009] Determining operating parameters of the grounding unit according to the electrical quantity parameters, wherein the operating parameters include the rated voltage of the arrester and the maximum operating power and resistance value of the resistor;

[0010] Controlling, according to the operating state, whether the grounding unit corresponding to the delivery module operates according to the operating parameters;

[0011] If the operating state is a stable operating state, the corresponding grounding unit is controlled not to work; if the operating state is a transient operating state, the grounding unit is controlled to work according to the operating parameters to consume energy.

[0012] Preferably, controlling the grounding unit to operate according to the operating parameters to consume energy includes: controlling the arrester of the grounding unit to start according to the rated voltage, and controlling the resistor to operate according to the maximum operating power and the resistance value to consume energy.

[0013] Preferably, determining the operating parameters of the grounding unit according to the electrical quantity parameters includes:

[0014] The rated voltage of the arrester is obtained by calculation based on the safety factor, transformation ratio, self-inductance of the primary winding of the transformer and the rate of rise of the fault current of the electrical quantity parameters;

[0015] The resistance value of the resistor is obtained by calculation according to the maximum DC current, the rated DC voltage, the total length, the inductance per unit length and the capacitance per unit length to ground of the DC transmission line of the electrical quantity parameters;

[0016] The maximum operating power of the resistor is obtained by calculating the fault current reduction multiple, the grounding electrode line length, the grounding electrode unit length inductance, the mutual inductance and the fault current drop time of the electrical quantity parameters.

[0017] Preferably, the fault current reduction factor is 4-5; and / or the safety factor is 0.8-0.9; and / or the transformation ratio is 0.01-0.05.

[0018] On the other hand, a DC side fault clearing device with ultra-long distance multi-terminal transmission is provided, which is applied to the above-mentioned fault clearing device, and the DC side fault clearing device includes a data acquisition module, a parameter determination module, a judgment module and an execution module;

[0019] The data acquisition module is used to obtain the electrical quantity parameters of the multi-terminal flexible DC system and the operating status of each sending module;

[0020] The parameter determination module is used to determine the operating parameters of the grounding unit according to the electrical quantity parameters, and the operating parameters include the rated voltage of the lightning arrester and the maximum operating power and resistance value of the resistor;

[0021] The judging module is used to control, according to the operating state, whether the grounding unit corresponding to the sending module operates according to the operating parameters;

[0022] The execution module is used to control the corresponding grounding unit to not work according to the operating state being a stable operating state; or to control the grounding unit to work according to the operating parameters to consume energy according to the operating state being a transient operating state.

[0023] Preferably, the execution module is further used to control the arrester of the grounding unit to start according to the rated voltage and the resistor to work according to the maximum operating power and the resistance value to consume energy according to the operating state being a transient operating state.

[0024] Preferably, the parameter determination module includes a first calculation submodule, a second calculation submodule and a third calculation submodule;

[0025] The first calculation submodule is used to calculate and obtain the rated voltage of the arrester according to the safety factor, transformation ratio, transformer primary winding self-inductance and fault current rise rate of the electrical quantity parameters;

[0026] The second calculation submodule is used to calculate the resistance value of the resistor according to the maximum DC current, the rated DC voltage, the total length, the inductance per unit length and the capacitance per unit length to ground of the DC transmission line of the electrical quantity parameters;

[0027] The third calculation submodule is used to calculate the maximum operating power of the resistor according to the fault current reduction multiple, grounding electrode line length, grounding electrode unit length inductance, mutual inductance and fault current falling time of the electrical quantity parameters.

[0028] Preferably, the fault current reduction factor is 4-5; and / or the safety factor is 0.8-0.9; and / or the transformation ratio is 0.01-0.05.

[0029] In another aspect, a terminal device is provided, comprising a processor and a memory;

[0030] The memory is used to store program codes and transmit the program codes to the processor;

[0031] The processor is used to execute the above-mentioned method for clearing DC side faults transmitted over ultra-long distances and multiple terminals according to the instructions in the program code.

[0032] The fault clearing device and the DC side fault clearing method, device and equipment for ultra-long-distance multi-terminal transmission are applied to a multi-terminal flexible DC system. The multi-terminal flexible DC system includes multiple transmission modules, each of which includes two converter stations and a grounding electrode line. The two converter stations are respectively connected to the grounding electrode line and then connected to the grounding electrode. The fault clearing device includes a grounding unit connected to the grounding electrode line. The grounding unit includes a transformer, a lightning arrester and a resistor. The primary side of the transformer is respectively connected to the grounding electrode and the grounding electrode line. The lightning arrester is connected in series with the resistor and then connected to the secondary side of the transformer. The lightning arrester is used to control the input and removal of the resistor; the resistor is used to consume energy.

[0033] The method includes obtaining electrical quantity parameters of a multi-terminal flexible DC system and the operating status of each sending module; determining the operating parameters of a grounding unit according to the electrical quantity parameters, the operating parameters including the rated voltage of a lightning arrester and the maximum operating power and resistance value of a resistor; controlling the grounding unit corresponding to the sending module to work according to the operating parameters according to the operating status; if the operating status is a stable operating status, controlling the corresponding grounding unit not to work; if the operating status is a transient operating status, controlling the grounding unit to work according to the operating parameters to consume energy.

[0034] It can be seen from the above technical scheme that the present application has the following advantages: the fault clearing device is connected to the sending module of the multi-terminal flexible DC system in a high-resistance grounding manner. After a DC fault occurs in the multi-terminal flexible DC system, the fault current is reduced due to the existence of the grounding high resistance, and the energy after the fault is quickly consumed through the resistance, thereby achieving the purpose of clearing the fault current. This solves the problem that the existing flexible DC uses a full half-bridge hybrid structure to clear DC faults, but this method has the technical problem of unstable operation of flexible DC transmission caused by converter tripping.

[0035] This ultra-long-distance multi-terminal DC side fault clearing method reduces the fault current due to the presence of the grounding unit after a DC fault occurs in the multi-terminal flexible DC system, and quickly consumes the energy after the fault, thereby achieving the purpose of clearing the fault current. This solves the technical problem that the existing flexible DC uses a full-half-bridge hybrid structure to clear DC faults, but this method has the problem of converter tripping, resulting in unstable operation of flexible DC transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0037] Figure 1A topological diagram of the connection between the multi-terminal flexible DC system and the fault clearing device according to an embodiment of the present application;

[0038] Figure 2 A circuit diagram of a fault clearing device according to an embodiment of the present application;

[0039] Figure 3 This is a flowchart of the steps of the method for clearing DC side faults transmitted over ultra-long distances and multiple terminals according to an embodiment of the present application;

[0040] Figure 4 It is a schematic diagram of the framework of the DC side fault clearing device for ultra-long distance multi-terminal transmission described in the embodiment of the present application;

[0041] Figure 5 A schematic diagram of a terminal device according to an embodiment of the present application;

[0042] Figure 6 It is a topological diagram of the existing multi-terminal flexible DC system;

[0043] Figure 7 The topology diagram of the existing converters is mostly a full half-bridge hybrid structure;

[0044] Figure 8 It is a topological diagram of an existing half-bridge modular multi-level converter;

[0045] Fig. 9 It is a schematic diagram of an equivalent circuit before the IGBT tube in the existing converter valve is locked;

[0046] Fig.10 It is a schematic diagram of an equivalent circuit after the IGBT tube in the existing converter valve is locked;

[0047] Fig.11 It is the equivalent circuit diagram of the existing full-bridge MMC in the locked state. DETAILED DESCRIPTION

[0048] In order to make the purpose, features, and advantages of the invention of this application more obvious and easy to understand, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the embodiments described below are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0049] In the description of the embodiments of the present application, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0050] In the embodiments of the present application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0051] In the embodiments of the present application, Figure 6 As shown in FIG. 1 , the converters in the multi-terminal flexible DC system are mostly full-half-bridge hybrid structures, and the hybrid modular multilevel converter MMC also follows the topological structure of the MMC, such as Figure 7 As shown in the figure, the power module of each bridge arm is composed of a part of half-bridge power modules and a part of full-bridge power modules. The DC fault clearing capability and step-down operation capability of the hybrid modular multilevel converter MMC are related to the proportion of full-bridge power modules. The higher the proportion of full-bridge power modules, the better the DC fault clearing capability and the stronger the step-down operation capability.

[0052] like Figure 8 In the topological structure of the half-bridge modular multilevel converter MMC shown in the figure, when the DC line fails, the transient current development of the half-bridge MMC converter valve is divided into two stages, namely before the IGBT tube is locked and after the IGBT is locked. Before the IGBT tube is locked, the equivalent circuit of the converter valve is as follows: Fig. 9 As shown in the figure, at this stage, the power module discharges to the short-circuit fault point through the turned-on IGBT tube. The discharge current rise rate is very high, so that the bridge arm current of the converter valve can exceed the maximum repeatable shutdown current of the IGBT tube within a few milliseconds or even hundreds of microseconds. Therefore, it is generally necessary to lock the converter valve as soon as possible to ensure that the IGBT tube can be reliably shut down to avoid damage to the converter valve. The equivalent circuit of the converter valve after the IGBT tube is locked is as follows Fig.10As shown in the figure, at this stage, the AC system, the anti-parallel diode of the power module, and the DC short-circuit fault point form a path, as shown in the dotted line path in the figure; at this stage, the anti-parallel diode not only needs to withstand a large short-circuit current stress, the peak value generally reaches more than ten kiloamperes, but also must have sufficient melting thermal energy value I2t capacity. Therefore, the diode needs to be specially designed, and existing projects generally use auxiliary thyristors for shunting or increase the current carrying capacity of the diode.

[0053] Since the AC system of the flexible DC can still feed short-circuit current to the fault point through the anti-parallel diode after the half-bridge MMC is locked, the AC circuit breaker must be tripped to isolate the electrical connection between the AC power supply and the fault point to clear the DC fault and restore the insulation of the fault point. During the restart phase of the DC system of the flexible DC after the fault is cleared, it is necessary to go through the stages of closing and charging the AC circuit breaker, exiting the starting resistor, and unlocking the converter valve, which takes a long time, generally several minutes or even dozens of minutes. Figure 7 As shown, the biggest advantage of the full-bridge MMC power module over the half-bridge power module is that it is more flexible in operation and can output negative voltage levels. The full-bridge MMC has a wider DC voltage regulation range and can achieve continuous and smooth rise and fall of the DC voltage between the negative rated value and the positive rated value. This feature meets the requirements of 70%, 80% or even lower step-down operation of long-distance DC transmission and rapid step-down restart after DC faults.

[0054] In the locked state, the equivalent circuit of the full-bridge MMC is as follows: Fig.11 Taking phases A and C as an example, at this time, regardless of the forward bridge arm current or the reverse bridge arm direction, the voltage applied to the anode and cathode of diodes D1~D4 is: , where U ac_peak is the peak value of the AC line voltage, U c It is the sum of the capacitor voltages of all power modules in each bridge arm of the full-bridge MMC. In the design phase of the main circuit parameters of the converter station, U ac_peak Less than 0.866U c , so diodes D2 and D3 will be cut off due to the reverse voltage. It is precisely because of this characteristic that the full-bridge MMC has the ability to self-clear DC faults.

[0055] The full-bridge MMC uses its own blocking characteristics to provide a back electromotive force with the opposite polarity to the AC power supply voltage in the blocking state, promoting the rapid attenuation of the DC fault current. The entire process does not require the AC circuit breaker to be tripped, and there is no mechanical switch operation, so the fault clearing speed is relatively fast. During the restart phase of the flexible DC system, the converter is unlocked again and the DC voltage is gradually established. This process also does not require mechanical switch operation, so a fast restart can be achieved.

[0056] The embodiments of the present application provide a fault clearing device and a method, device and equipment for clearing faults on the DC side of ultra-long-distance multi-terminal transmission, which solves the technical problem that the existing flexible DC uses a full half-bridge hybrid structure to clear DC faults, but this method has the problem of converter tripping and causing unstable operation of flexible DC transmission.

[0057] Embodiment 1:

[0058] Figure 1 This is a topological diagram of the connection between the multi-terminal flexible DC system and the fault clearing device according to an embodiment of the present application. Figure 2 Schematic diagram of a circuit of a fault clearing device according to an embodiment of the present application.

[0059] like Figure 1 and Figure 2 As shown, an embodiment of the present application provides a fault clearing device, which is applied to a multi-terminal flexible DC system. The multi-terminal flexible DC system includes multiple sending modules 2, each sending module 2 includes two converter stations 21 and a grounding electrode line 22, and the two converter stations 21 are respectively connected to the grounding electrode line 22 and then connected to the grounding electrode 23. The fault clearing device includes a grounding unit 24 connected to the grounding electrode line 22, and the grounding unit 24 includes a transformer 241, a lightning arrester 242 and a resistor 243. The primary side of the transformer 241 is respectively connected to the grounding electrode 23 and the grounding electrode line 22, and the lightning arrester 242 is connected in series with the resistor 243 and then connected to the secondary side of the transformer 241; the lightning arrester 242 is used to control the input and removal of the resistor 243; the resistor 243 is used to consume energy.

[0060] It should be noted that the grounding unit 24 is installed between the grounding electrode line 22 and the grounding electrode 23 of the multi-terminal flexible DC system. The grounding unit 24 uses an AC transformer 241. When a stable DC current is connected to the multi-terminal flexible DC system, the secondary side of the transformer 241 will not induce voltage and current, thereby not causing the action of the lightning arrester 242. However, during the transient operation of the multi-terminal flexible DC system, the transient process can be induced to the secondary side through the magnetic field of the transformer 241, and the secondary side of the transformer 241 generates a higher voltage, causing the lightning arrester 242 to act, thereby putting the resistor 243 into operation to damp the fault current.

[0061] In the embodiment of the present application, the grounding unit 24 uses the primary side of the transformer 241 to be connected between the grounding electrode 23 and the grounding electrode line 22, and the secondary side of the transformer 241 is connected in series with a lightning arrester 242 and a resistor 243. Since a large DC current flows into the primary side of the transformer 241, it is very easy to cause saturation of the ferromagnetic material, so the transformer 241 adopts a hollow structure, that is, only the magnetic field coupling between the air is used. In addition, the turns ratio of the primary side winding and the secondary side winding of the transformer 241 is N: 1, N = 0.01 ~ 0.05, thereby effectively increasing the secondary side AC voltage of the transformer 241 and reducing the secondary side AC current of the transformer 241.

[0062] In the embodiment of the present application, the lightning arrester 242 is used to control the switching on and off of the resistor 243 to prevent the resistor 242 from affecting the multi-terminal flexible DC system when it is switched on in a stable state.

[0063] In the embodiment of the present application, the resistor 243 is used to consume transient energy.

[0064] The present application provides a fault clearing device, which is applied to a multi-terminal flexible DC system. The multi-terminal flexible DC system includes multiple sending modules, each sending module includes two converter stations and a grounding electrode line, the two converter stations are respectively connected to the grounding electrode line and then connected to the grounding electrode, the fault clearing device includes a grounding unit connected to the grounding electrode line, the grounding unit includes a transformer, a lightning arrester and a resistor, the primary side of the transformer is respectively connected to the grounding electrode and the grounding electrode line, the lightning arrester is connected in series with the resistor and then connected to the secondary side of the transformer; the lightning arrester is used to control the input and removal of the resistor; the resistor is used to consume energy. The fault clearing device is connected to the sending module of the multi-terminal flexible DC system in a high-resistance grounding manner. After a DC fault occurs in the multi-terminal flexible DC system, due to the existence of the high grounding resistance, the fault current is reduced, and the energy after the fault is quickly consumed by the resistor, thereby achieving the purpose of clearing the fault current, solving the problem that the existing flexible DC uses a full half-bridge hybrid structure to clear DC faults, but this method has the technical problem of unstable operation of flexible DC transmission caused by converter tripping.

[0065] Embodiment 2:

[0066] Figure 3 This is a flowchart of the steps of the method for clearing DC side faults for ultra-long-distance multi-terminal transmission described in an embodiment of the present application.

[0067] like Figure 3 As shown, the embodiment of the present application provides a method for clearing a DC side fault with ultra-long-distance multi-terminal transmission, which is applied to the above-mentioned fault clearing device. The DC side fault clearing method includes the following steps:

[0068] S1. Obtain the electrical quantity parameters of the multi-terminal flexible DC system and the operating status of each transmission module.

[0069] It should be noted that the content of the fault clearing device has been described in Example 1, and the content of the fault clearing device will not be described again in this embodiment. In step S1, the electrical quantity parameters of the multi-terminal flexible DC system and the operating status of each sending module are obtained to provide data for subsequent steps. In this embodiment, the electrical quantity parameters include the fault current reduction multiple, the length of the grounding electrode line, the inductance per unit length of the grounding electrode, the mutual inductance value, the fault current drop time, the safety factor, the transformation ratio, the transformer primary winding self-inductance, the fault current rise rate, the maximum DC current, the rated DC voltage, and the total length of the DC transmission line, the inductance per unit length, and the capacitance per unit length to the ground.

[0070] S2. Determine the operating parameters of the grounding unit according to the electrical quantity parameters, the operating parameters including the rated voltage of the lightning arrester and the maximum operating power and resistance value of the resistor.

[0071] It should be noted that in step S2, the operating parameters of the grounding unit connected to the multi-terminal flexible DC system in a high-resistance grounding manner are first determined according to the electrical quantity parameters obtained in step S1 to provide data for subsequent steps.

[0072] S3. Control the grounding unit corresponding to the sending module according to the operating status to determine whether it works according to the operating parameters.

[0073] It should be noted that in step S3, it is determined whether the grounding unit connected to the corresponding sending module is working according to the operating status of the sending module obtained in step S1.

[0074] S4. If the operation state is a stable operation state, the corresponding grounding unit is controlled not to work; if the operation state is a transient operation state, the grounding unit is controlled to work according to the operation parameters to consume energy.

[0075] It should be noted that in step S4, the operation is performed according to the result of the judgment in step S3 to ensure the stability of the operation of the multi-terminal flexible DC system. In this embodiment, controlling the grounding unit to work according to the operating parameters to consume energy includes: controlling the arrester of the grounding unit to start at the rated voltage, and the resistor to work at the maximum operating power and resistance value to consume energy.

[0076] The present application provides a method for clearing faults on the DC side of ultra-long-distance multi-terminal transmission, which is applied to the above-mentioned fault clearing device. The DC side fault clearing method includes the following steps: obtaining the electrical quantity parameters of the multi-terminal flexible DC system and the operating status of each transmission module; determining the operating parameters of the grounding unit according to the electrical quantity parameters, the operating parameters including the rated voltage of the arrester and the maximum operating power and resistance value of the resistor; controlling whether the grounding unit corresponding to the transmission module works according to the operating status; if the operating status is a stable operating status, controlling the corresponding grounding unit not to work; if the operating status is a transient operating status, controlling the grounding unit to work according to the operating parameters to consume energy. After a DC fault occurs in the multi-terminal flexible DC system, the DC side fault clearing method of ultra-long-distance multi-terminal transmission reduces the fault current due to the presence of the grounding unit, and quickly consumes the energy after the fault, thereby achieving the purpose of clearing the fault current, solving the technical problem that the existing flexible DC uses a full half-bridge hybrid structure to clear DC faults, but this method has the problem of unstable operation of flexible DC transmission due to converter tripping.

[0077] In one embodiment of the present application, determining the operating parameters of the grounding unit according to the electrical quantity parameters includes:

[0078] The rated voltage of the arrester is obtained by calculating the safety factor of the electrical quantity parameters, the transformation ratio, the self-inductance of the transformer primary winding and the fault current rise rate;

[0079] The resistance value of the resistor is obtained by calculating the maximum DC current, rated DC voltage, total length, inductance per unit length and capacitance per unit length to ground of the DC transmission line.

[0080] The maximum operating power of the resistor is calculated based on the fault current reduction multiple of the electrical quantity parameters, the grounding electrode line length, the grounding electrode inductance per unit length, the mutual inductance value and the fault current drop time.

[0081] It should be noted that the fault current reduction factor can be 4 to 5, the safety factor can be 0.8 to 0.9, and the transformation ratio can be 0.01 to 0.05.

[0082] In the embodiment of the present application, the rated voltage of the arrester is calculated by using the voltage formula according to the safety factor of the electrical quantity parameters, the transformation ratio, the self-inductance of the primary winding of the transformer, and the fault current rise rate; the resistance value of the resistor is calculated by using the resistance formula according to the maximum DC current, the rated DC voltage, and the total length of the DC transmission line, the inductance per unit length, and the capacitance per unit length to the ground of the electrical quantity parameters; the maximum operating power of the resistor is calculated by using the power formula according to the fault current reduction multiple, the grounding electrode line length, the grounding electrode inductance per unit length, the mutual inductance, and the fault current drop time of the electrical quantity parameters. The voltage formula is:

[0083]

[0084] The resistance formula is:

[0085]

[0086] The power formula is:

[0087]

[0088] Where N is the transformer ratio, L is m is the transformer primary winding self-inductance, di / dt is the maximum fault current rise rate of the multi-terminal flexible DC transmission system during a fault, L is the total length of the DC transmission line, L1 is the inductance per unit length of the DC transmission line, C is the capacitance per unit length of the DC transmission line to ground, I dc is the maximum DC current of the multi-terminal flexible DC transmission system, U dc is the rated DC voltage of the multi-terminal flexible DC transmission system, K is the fault current reduction factor, usually 4-5, which can be determined according to the actual system conditions; L g is the length of the grounding electrode line, L gl is the inductance per unit length of the grounding electrode, M is the mutual inductance of the grounding unit; T is the fault current drop time, and the recommended value of T is about 100ms.

[0089] Embodiment three:

[0090] Figure 4 This is a schematic diagram of the framework of the DC side fault clearing device for ultra-long distance multi-terminal transmission described in an embodiment of the present application.

[0091] like Figure 4 As shown, the embodiment of the present application provides a DC side fault clearing device with ultra-long distance multi-terminal transmission, which is applied to the above-mentioned fault clearing device. The DC side fault clearing device includes a data acquisition module 10, a parameter determination module 20, a judgment module 30 and an execution module 40;

[0092] The data acquisition module 10 is used to obtain the electrical quantity parameters of the multi-terminal flexible DC system and the operating status of each sending module;

[0093] A parameter determination module 20, for determining the operating parameters of the grounding unit according to the electrical quantity parameters, the operating parameters including the rated voltage of the arrester and the maximum operating power and resistance value of the resistor;

[0094] A judgment module 30, used to control whether the grounding unit corresponding to the sending module works according to the operating state;

[0095] The execution module 40 is used to control the corresponding grounding unit to not work according to the stable operation state; or to control the grounding unit to work according to the operation parameters to consume energy according to the transient operation state.

[0096] In the embodiment of the present application, the execution module 40 is also used to control the lightning arrester of the grounding unit to start at the rated voltage and the resistor to work at the maximum operating power and resistance value to consume energy according to the operating state being a transient operating state.

[0097] In the embodiment of the present application, the parameter determination module 20 includes a first calculation submodule, a second calculation submodule and a third calculation submodule;

[0098] The first calculation submodule is used to calculate the rated voltage of the arrester according to the safety factor of the electrical quantity parameters, the transformation ratio, the self-inductance of the primary winding of the transformer and the fault current rise rate;

[0099] The second calculation submodule is used to calculate the resistance value of the resistor according to the maximum DC current, the rated DC voltage, the total length, the inductance per unit length, and the capacitance per unit length to ground of the DC transmission line of the electrical quantity parameters;

[0100] The third calculation submodule is used to calculate the maximum operating power of the resistor according to the fault current reduction multiple of the electrical quantity parameters, the grounding electrode line length, the grounding electrode unit length inductance, the mutual inductance value and the fault current falling time.

[0101] In an embodiment of the present application, the fault current reduction factor is 4 to 5; and / or the safety factor is 0.8 to 0.9; and / or the transformation ratio is 0.01 to 0.05.

[0102] It should be noted that the content of the module in the device of Example 3 corresponds to the step content of the method in Example 2. The content of the ultra-long-distance multi-terminal DC side fault clearing method has been described in Example 2, and the module content of the ultra-long-distance multi-terminal DC side fault clearing device will not be described in detail in this embodiment.

[0103] Embodiment 4:

[0104] Figure 5 A schematic diagram of a terminal device described in an embodiment of the present application.

[0105] like Figure 5 As shown, an embodiment of the present application provides a terminal device, including a processor and a memory;

[0106] A memory, used for storing program codes and transmitting the program codes to a processor;

[0107] The processor is used to execute the above-mentioned ultra-long-distance multi-terminal DC side fault clearing method according to the instructions in the program code.

[0108] It should be noted that the processor is used to execute the steps in the above-mentioned method for clearing DC faults sent by multiple terminals over a long distance according to the instructions in the program code. Alternatively, the processor implements the functions of each module / unit in the above-mentioned system / device embodiments when executing the computer program.

[0109] Exemplarily, the computer program may be divided into one or more modules / units, one or more modules / units are stored in a memory and executed by a processor to complete the present application. One or more modules / units may be a series of computer program instruction segments capable of completing a specific function, and the instruction segments are used to describe the execution process of the computer program in a terminal device.

[0110] The terminal device may be a computing device such as a desktop computer, a notebook, a PDA, or a cloud server. The terminal device may include, but is not limited to, a processor and a memory. Those skilled in the art will appreciate that this does not constitute a limitation on the terminal device, and may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the terminal device may also include input and output devices, network access devices, buses, etc.

[0111] The processor may be a central processing unit (CPU), other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (dSIC), field-programmable gate arrays (FPGAs) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0112] The memory may be an internal storage unit of the terminal device, such as a hard disk or memory of the terminal device. The memory may also be an external storage device of the terminal device, such as a plug-in hard disk, a smart memory card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the terminal device. Furthermore, the memory may include both an internal storage unit of the terminal device and an external storage device. The memory is used to store computer programs and other programs and data required by the terminal device. The memory may also be used to temporarily store data that has been output or is to be output.

[0113] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0114] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0115] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0116] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0117] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM), random access memory (RAM), disk or optical disk, etc., various media that can store program codes.

[0118] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A fault clearing device, applied to a multi-terminal flexible DC system, wherein the multi-terminal flexible DC system comprises a plurality of sending modules, each of which comprises two converter stations and a grounding electrode line, wherein the two converter stations are respectively connected to the grounding electrode line and then to the grounding electrode, wherein: The fault clearing device comprises a grounding unit connected to the grounding electrode line, the grounding unit comprises a transformer, a lightning arrester and a resistor, the primary side of the transformer is respectively connected to the grounding electrode and the grounding electrode line, the lightning arrester is connected in series with the resistor and then connected to the secondary side of the transformer; the lightning arrester is used to control the input and removal of the resistor; The resistor is used to dissipate energy.

2. A method for clearing DC faults at ultra-long distances and multiple terminals, applied to the fault clearing device as claimed in claim 1, characterized in that: The DC side fault clearing method comprises the following steps: Obtain the electrical quantity parameters of the multi-terminal flexible DC system and the operating status of each transmission module; Determining operating parameters of the grounding unit according to the electrical quantity parameters, wherein the operating parameters include the rated voltage of the arrester and the maximum operating power and resistance value of the resistor; Controlling, according to the operating state, whether the grounding unit corresponding to the delivery module operates according to the operating parameters; If the operating state is a stable operating state, the corresponding grounding unit is controlled not to work; if the operating state is a transient operating state, the grounding unit is controlled to work according to the operating parameters to consume energy.

3. The method for clearing DC faults in ultra-long-distance multi-terminal transmission according to claim 2 is characterized in that: Controlling the grounding unit to operate according to the operating parameters to consume energy includes: controlling the arrester of the grounding unit to start according to the rated voltage, and controlling the resistor to operate according to the maximum operating power and the resistance value to consume energy.

4. The method for clearing DC faults in ultra-long-distance multi-terminal transmission according to claim 2 is characterized in that: Determining the operating parameters of the grounding unit according to the electrical quantity parameters includes: The rated voltage of the arrester is obtained by calculation based on the safety factor, transformation ratio, self-inductance of the primary winding of the transformer and the fault current rise rate of the electrical quantity parameters; The resistance value of the resistor is obtained by calculation according to the maximum DC current, the rated DC voltage, the total length, the inductance per unit length and the capacitance per unit length to ground of the DC transmission line of the electrical quantity parameters; The maximum operating power of the resistor is obtained by calculating the fault current reduction multiple, the grounding electrode line length, the grounding electrode unit length inductance, the mutual inductance and the fault current drop time of the electrical quantity parameters.

5. The method for clearing DC faults in ultra-long-distance multi-terminal transmission according to claim 4 is characterized in that: The fault current reduction factor is 4-5; and / or the safety factor is 0.8-0.9; and / or the transformation ratio is 0.01-0.

05.

6. A DC side fault clearing device with ultra-long distance multi-terminal transmission, applied to the fault clearing device as claimed in claim 1, characterized in that: The DC side fault clearing device includes a data acquisition module, a parameter determination module, a judgment module and an execution module; The data acquisition module is used to obtain the electrical quantity parameters of the multi-terminal flexible DC system and the operating status of each sending module; The parameter determination module is used to determine the operating parameters of the grounding unit according to the electrical quantity parameters, and the operating parameters include the rated voltage of the lightning arrester and the maximum operating power and resistance value of the resistor; The judging module is used to control, according to the operating state, whether the grounding unit corresponding to the sending module operates according to the operating parameters; The execution module is used to control the corresponding grounding unit to not work according to the operating state being a stable operating state; or to control the grounding unit to work according to the operating parameters to consume energy according to the operating state being a transient operating state.

7. The DC side fault clearing device for ultra-long distance multi-terminal transmission according to claim 6 is characterized in that: The execution module is further used for controlling the arrester of the grounding unit to start at the rated voltage and the resistor to work at the maximum operating power and the resistance value to consume energy according to the operating state being a transient operating state.

8. The DC side fault clearing device for ultra-long distance multi-terminal transmission according to claim 6 is characterized in that: The parameter determination module includes a first calculation submodule, a second calculation submodule and a third calculation submodule; The first calculation submodule is used to calculate and obtain the rated voltage of the arrester according to the safety factor, transformation ratio, transformer primary winding self-inductance and fault current rise rate of the electrical quantity parameters; The second calculation submodule is used to calculate the resistance value of the resistor according to the maximum DC current, the rated DC voltage, the total length, the inductance per unit length and the capacitance per unit length to ground of the DC transmission line of the electrical quantity parameters; The third calculation submodule is used to calculate the maximum operating power of the resistor according to the fault current reduction multiple, grounding electrode line length, grounding electrode unit length inductance, mutual inductance and fault current falling time of the electrical quantity parameters.

9. The DC side fault clearing device for ultra-long distance multi-terminal transmission according to claim 8 is characterized in that: The fault current reduction factor is 4-5; and / or the safety factor is 0.8-0.9; and / or the transformation ratio is 0.01-0.

05.

10. A terminal device, characterized in that: including a processor and a memory; The memory is used to store program codes and transmit the program codes to the processor; The processor is used to execute the method for clearing DC side faults transmitted over ultra-long distances and multiple terminals according to the instructions in the program code as described in any one of claims 2 to 5.

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