Method for discriminating internal and external faults of flexible direct current power transmission system and related device

Abstract

The application discloses a method and related device for discriminating intra-zone and extra-zone faults of a flexible direct current power transmission system, and the method comprises the following steps: acquiring system topological data corresponding to the flexible direct current power transmission system; determining a ground model fault equivalent circuit corresponding to the flexible direct current power transmission system under a grounding fault condition according to the system topological data; the grounding fault condition comprises one of the following: a positive electrode grounding fault and a negative electrode grounding fault; determining a target fault discrimination condition according to the ground model fault equivalent circuit; acquiring actual operation data of the flexible direct current power transmission system under the grounding fault condition; determining a target discrimination result according to the target fault discrimination condition and the actual operation data; the target discrimination result comprises one of the following: an extra-zone fault and an intra-zone fault. By adopting the embodiment of the application, the reliability of fault identification can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power failure detection, and in particular to a method for discriminating intra-zone and extra-zone faults of a flexible DC power transmission system and related apparatus. BACKGROUND

[0002] Compared with a traditional HVDC power transmission system based on thyristors, the flexible DC power transmission system has the advantages of strong controllability, fast power regulation, flexible operation mode, and the like, and is suitable for scenarios such as weak systems, island power supply, and new energy grid connection.

[0003] In the fault protection of the flexible DC power transmission system, a single-end quantity protection method is used to identify a fault region by using fault traveling wave front information, but the single-end quantity protection method is susceptible to noise interference, and in the case of a high-resistance fault, the traveling wave front energy is weak and difficult to capture, and the reliability is insufficient. Therefore, how to improve the reliability of fault identification has become a problem to be solved. SUMMARY

[0004] Embodiments of the present application provide a method for discriminating intra-zone and extra-zone faults of a flexible DC power transmission system and related apparatus, which can improve the reliability of fault identification.

[0005] In a first aspect, embodiments of the present application provide a method for discriminating intra-zone and extra-zone faults of a flexible DC power transmission system, comprising:

[0006] obtaining system topology data corresponding to the flexible DC power transmission system;

[0007] determining, according to the system topology data, a ground model fault equivalent circuit corresponding to the flexible DC power transmission system in the case of a ground fault; the ground fault case includes one of the following: a positive ground fault, a negative ground fault;

[0008] determining a target fault discrimination condition according to the ground model fault equivalent circuit;

[0009] obtaining actual operation data of the flexible DC power transmission system in the case of the ground fault;

[0010] determining a target discrimination result according to the target fault discrimination condition and the actual operation data; the target discrimination result includes one of the following: an extra-zone fault, an intra-zone fault.

[0011] In a second aspect, embodiments of the present application provide a device for discriminating intra-zone and extra-zone faults of a flexible DC power transmission system, comprising: an obtaining unit, a determining unit, and a discriminating unit, wherein:

[0012] The obtaining unit is configured to obtain system topology data corresponding to the flexible DC power transmission system.

[0013] The determining unit is configured to determine, according to the system topology data, a ground model fault equivalent circuit corresponding to the flexible HVDC power transmission system in a ground fault condition; the ground fault condition includes one of a positive pole ground fault and a negative pole ground fault; and determine a target fault discrimination condition according to the ground model fault equivalent circuit.

[0014] The obtaining unit is further configured to obtain actual operation data of the flexible HVDC power transmission system in the ground fault condition.

[0015] The determining unit is configured to determine a target discrimination result according to the target fault discrimination condition and the actual operation data; and the target discrimination result includes one of an external fault and an internal fault.

[0016] In a third aspect, an electronic device is provided, which includes a processor, a memory, a communication interface, and one or more programs. The one or more programs are stored in the memory and configured to be executed by the processor. The programs include instructions for performing the steps in the first aspect of the embodiments.

[0017] In a fourth aspect, a computer readable storage medium is provided, which stores a computer program for electronic data exchange. The computer program causes a computer to perform some or all of the steps described in the first aspect of the embodiments.

[0018] In a fifth aspect, a computer program product is provided, which includes a non-transitory computer readable storage medium storing a computer program. The computer program is operable to cause a computer to perform some or all of the steps described in the first aspect of the embodiments. The computer program product can be a software installation package.

[0019] The embodiments of the present application have the following advantages:

[0020] It can be seen that the in-zone and out-zone fault discrimination method of the flexible DC power transmission system described in the application, by acquiring system topology data of the flexible DC power transmission system, for different grounding fault conditions such as positive pole grounding fault and negative pole grounding fault, constructs a corresponding ground model fault equivalent circuit, then determines the target fault discrimination condition according to the ground model fault equivalent circuit, then acquires actual operation data of the flexible DC power transmission system under the grounding fault condition, and combines it with the target fault discrimination condition for judgment, the actual operation data contains real-time electrical information of the system, by comparing and analyzing the actual operation data with the target fault discrimination condition, the fault can be more reliably identified; this combination of theoretical model (i.e. ground model fault equivalent circuit) and actual data can adapt to various conditions in the system operation process, reduce the interference of noise, transition resistance and other factors on fault identification, thereby improving the reliability of fault identification. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the application or the background art, the drawings needed to be used in the embodiments of the application or the background art will be described below.

[0022] Figure 1 is a structural schematic diagram of an electronic device provided by an embodiment of the application;

[0023] Figure 2 is an application scenario diagram of an electronic device provided by an embodiment of the application;

[0024] Figure 3 is a flowchart of an in-zone and out-zone fault discrimination method of a flexible DC power transmission system provided by an embodiment of the application;

[0025] Figure 4 is a circuit structure schematic diagram of a ground model fault equivalent circuit provided by an embodiment of the application;

[0026] Figure 5 is a simulation circuit diagram of a flexible DC power transmission system provided by an embodiment of the application;

[0027] Figure 6 is a simulation waveform diagram of a ground model current under a fault condition provided by an embodiment of the application;

[0028] Figure 7 is a simulation waveform diagram of a ground model current under another fault condition provided by an embodiment of the application;

[0029] Figure 8 is a functional unit composition block diagram of an in-zone and out-zone fault discrimination device of a flexible DC power transmission system provided by an embodiment of the application;

[0030] Figure 9Fig. 1 is a structural schematic diagram of an electronic device provided by an embodiment of the present application. DETAILED DESCRIPTION

[0031] In order to enable persons skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by persons skilled in the art without creative work fall within the scope of protection of the present application.

[0032] The terms "first", "second", and the like in the specification and claims of the present application and the above-described drawings are used to distinguish different objects, and are not used to describe a specific order. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but can optionally include steps or units not listed, or can optionally include other steps or units inherent to the process, method, product, or device.

[0033] It should be understood that the term "and / or" herein is only used to describe the association relationship of the associated objects, and can represent the existence of three relationships, for example, A and / or B can represent the existence of A alone, the existence of A and B, and the existence of B alone. In addition, the character " / " in this paper represents that the front and rear associated objects are a "or" relationship. The "multiple" appearing in the embodiments of the present application means two or more than two.

[0034] The "at least one" or similar expressions in the embodiments of the present application means any combination of the items, including any combination of single item or multiple items, means one or more, and multiple means two or more than two. For example, at least one of a, b or c can represent the following seven cases: a, b, c, a and b, a and c, b and c, a, b and c. Wherein, each of a, b and c can be an element or a set containing one or more elements.

[0035] The "connection" appearing in the embodiments of the present application means direct connection or indirect connection and various connection modes to realize communication between devices, which is not limited by the embodiments of the present application.

[0036] Reference to“an embodiment” herein means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase“in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily all referring to a common set of embodiments, of the application, differing embodiments can be described.

[0037] The electronic device described in the embodiments of the application can include a smart phone (such as an Android phone, an iOS phone, a Windows Phone phone, etc.), a tablet computer, a palm computer, a notebook computer, a video matrix, a monitoring platform, a mobile internet device (MID), or a wearable device, etc. The above are only examples and are not exhaustive, and include but are not limited to the above devices.

[0038] Of course, the electronic device described above can also be a server, for example, a cloud server.

[0039] The related content, concepts, meanings, technical problems, technical solutions, and beneficial effects involved in the embodiments of the application are described below.

[0040] First, some professional terms involved in the application are explained:

[0041] Flexible DC power transmission system: A power transmission system that uses voltage source converters to realize AC-DC power conversion, with strong controllability, flexible power regulation, and adaptability to new energy grid connection, etc. The core is to realize bidirectional energy flow through the switching control of power electronic devices.

[0042] Flexible DC power transmission system with pseudo-bipolar structure: A typical topology of flexible DC power transmission system, using“bipolar line + single pole grounding” design: containing two DC lines of positive and negative poles, usually one pole (such as positive) is directly grounded, and the other pole (such as negative) is suspended or weakly grounded. In normal operation, power is symmetrically transmitted by both poles, and in the event of a fault, a single-pole loop can be formed through the grounded pole to continue operation, balancing economy and reliability, and is a commonly used structure for medium and high voltage DC power transmission.

[0043] Ground fault: A fault in which the insulation between the DC line or device and the ground is broken, causing current to flow through the ground to form a loop, including positive ground fault (positive pole connected to ground) and negative ground fault (negative pole connected to ground), which is a common fault type in flexible DC systems, which can cause overcurrent, voltage fluctuations, etc. Positive (negative) ground fault is a specific fault type, which will inevitably cause ground mode fault components (ground mode fault is its characteristic performance).

[0044] Earth mode current: The component of system current extracted by modal decomposition, which reflects the current circulating through the earth. When a ground fault occurs, the fault current forms a loop through the earth, and the earth mode current is the core representation of this loop current. Its amplitude, phase, and other characteristics can be used for fault discrimination.

[0045] Earth mode fault: Not an independent fault type, but a fault accompanied by earth mode current (current component circulating through the earth). It is usually caused by a ground fault and is described from the perspective of current modalities. By analyzing the characteristics of earth mode current (such as average value, traveling wave characteristics), the fault location (in-zone / out-of-zone) and type can be identified, which is an important perspective for ground fault analysis.

[0046] Current traveling wave reflection coefficient: When a fault occurs, the current traveling wave is reflected at nodes with different impedance characteristics (such as the ends of the line and the converter interface). The ratio of the amplitude of the reflected wave to the incident wave is called the current traveling wave reflection coefficient. Its value is determined by the characteristic impedance on both sides of the node and can reflect the fault location and network structure, which is a key parameter for traveling wave protection.

[0047] Please refer to Figure 1 , Figure 1 is a structural schematic diagram of an electronic device provided by an embodiment of the present application. As can be seen, the electronic device can include a communication module, a control module, a fault discrimination module, and the like, without limitation. Among them:

[0048] The communication module is responsible for data interaction with various sensors, converters, control centers, and other devices in the flexible direct current power transmission system (hereinafter referred to as the system). On the one hand, it receives real-time collected voltage, current, and other electrical quantity data during system operation to provide original input for fault discrimination. On the other hand, it can send fault discrimination results and other information to other devices or systems for subsequent protection actions, monitoring and management operations, etc.

[0049] The control module, as the core control unit of the electronic device, coordinates the work of each module. It can perform preliminary processing and scheduling on the data received by the communication module, issue data processing instructions to the fault discrimination module, and generate corresponding control signals based on the results of the fault discrimination module, such as controlling the action of the protection device of the system, adjusting the operating parameters of the system, etc.

[0050] The fault discrimination module, based on the actual operating data transmitted by the communication module, combines the pre-set logic and algorithms (such as the in-zone and out-of-zone fault discrimination method for the flexible direct current power transmission system provided by the present application), analyzes and judges whether the flexible direct current power transmission system has a fault, and whether the fault is an in-zone fault or an out-of-zone fault, and outputs the target discrimination result, providing a key basis for fault handling of the system.

[0051] Please refer toFigure 2 , Figure 2 is an application scenario of an electronic device provided by an embodiment of the present application. As can be seen, the electronic device can be in bidirectional communication connection with the flexible DC power transmission system. When it is necessary to detect faults of the flexible DC power transmission system, the electronic device can execute the in-zone and out-zone fault discrimination method of the flexible DC power transmission system provided by an embodiment of the present application to evaluate the flexible DC power transmission system. The specific steps are as follows:

[0052] obtain system topology data corresponding to the flexible DC power transmission system;

[0053] determine, according to the system topology data, a ground model fault equivalent circuit corresponding to the flexible DC power transmission system in a ground fault condition; the ground fault condition includes one of the following: positive ground fault, negative ground fault;

[0054] determine a target fault discrimination condition according to the ground model fault equivalent circuit;

[0055] obtain actual operation data of the flexible DC power transmission system in the ground fault condition;

[0056] determine a target discrimination result according to the target fault discrimination condition and the actual operation data; the target discrimination result includes one of the following: out-zone fault, in-zone fault.

[0057] It needs to be explained that the electronic device can execute part or all steps of the in-zone and out-zone fault discrimination method of the flexible DC power transmission system provided by an embodiment of the present application.

[0058] Please refer to Figure 3 , Figure 3 is a flowchart of an in-zone and out-zone fault discrimination method of a flexible DC power transmission system provided by an embodiment of the present application. The method can be applied to an electronic device, and the method includes but is not limited to the following steps:

[0059] S301, obtain system topology data corresponding to the flexible DC power transmission system.

[0060] In an embodiment of the present application, the system topology data can include at least one of the following information: structure layout information, device configuration information, device connection relationship, operation parameter information, and the like, which are not limited herein.

[0061] In specific embodiments, the design drawings of the flexible DC power transmission system can be acquired first, including electrical main wiring diagram, converter station layout diagram, DC line route diagram, etc. In these drawings, the number and position of the converter stations in the system, the connection mode of the positive and negative pole lines, the setting position of the grounding device, and the installation position and connection relationship of the power equipment such as the smoothing reactor and the DC circuit breaker, etc. topological data can be determined. In this way, the system topological data can be obtained. Alternatively, the staff can also investigate the installation site of the flexible DC power transmission system to obtain the actual installation position of the power equipment in the system, the route and connection mode of the line, etc. topological data, and compare it with the design drawings to confirm the actual situation of the system topology. For the parts that differ between the design drawings and the actual situation, record and correct them to ensure that the topological data can accurately reflect the actual structure of the flexible DC power transmission system. In this way, the system topological data can be obtained.

[0062] S302, according to the system topological data, determine the corresponding ground mode fault equivalent circuit of the flexible DC power transmission system under the ground fault condition; the ground fault condition includes one of the following: positive ground fault, negative ground fault.

[0063] In the embodiments of the present application, the ground mode fault equivalent circuit is a circuit model that simplifies the complex three-phase or bipolar system to only reflect the characteristics of the ground mode current based on the modal decomposition theory when the flexible DC power transmission system occurs a ground fault, which is used to analyze and study the change rule of the system electrical quantity when the ground fault occurs.

[0064] In specific embodiments, the ground mode fault equivalent circuit of the flexible DC power transmission system under the ground fault condition can be determined according to the system topological data. Specifically, the system can be placed in a ground fault first, then the three-phase or bipolar current and voltage of the system during normal operation or fault can be decomposed into different modal components by using mathematical methods such as Clark transformation, and the ground mode component is separated out. Then, each device in the system can be equivalent to an equivalent element with specific impedance or power supply characteristics according to the system topological data, to obtain a plurality of equivalent elements. For example, the control effect of the converter on the ground mode current when the ground fault occurs can be converted into a controlled power source or a variable impedance in the equivalent circuit. Finally, the plurality of equivalent elements can be connected according to the actual connection relationship of each element in the system topological data. For example, if a DC line connects the rectifier station and the inverter station, the corresponding line equivalent element in the equivalent circuit is connected to the equivalent elements of the rectifier station and the inverter station. In this way, a complete ground mode fault equivalent circuit can be constructed.

[0065] S303, determine the target fault discrimination condition according to the ground mode fault equivalent circuit.

[0066] In the embodiments of the present application, the ground mode fault equivalent circuit can be analyzed to determine the target fault discrimination condition.

[0067] Optionally, the equivalent circuit for ground model faults includes a positive direction fault equivalent circuit and a negative direction fault equivalent circuit; step S303, determining the target fault discrimination condition based on the equivalent circuit for ground model faults may include the following steps:

[0068] S31. Determine the first current traveling wave reflection coefficient corresponding to the positive direction fault equivalent circuit;

[0069] S32. Determine the expression for the first fault ground mode current corresponding to the positive direction fault equivalent circuit based on the first current traveling wave reflection coefficient.

[0070] S33. Determine the expression for the second fault ground mode current corresponding to the reverse fault equivalent circuit;

[0071] S34. Determine the target fault discrimination condition based on the first fault ground mode current expression and the second fault ground mode current expression.

[0072] In this embodiment of the application, when the system grounding fault is a positive grounding fault, please refer to... Figure 4 , Figure 4 This is a schematic diagram of the circuit structure of an equivalent circuit for a ground mode fault provided in an embodiment of this application; it can be seen that... Figure 4 In this diagram, 'a' represents the equivalent circuit diagram for a positive direction fault. The structure of the equivalent circuit diagram for a positive direction fault is as follows:

[0073] The first terminal of the first resistor R1 is open-circuited (because there is no direct grounding point on the rectifier side, so for the ground mode component, the rectifier side is equivalent to an open circuit), and the second terminal of the first resistor R1 is connected to the first power supply. u The negative terminal of F1, the first power supply u The positive terminal of F1 is grounded. It should be explained that Fa represents the positive fault point, which is located between the first resistor R1 and the first power supply. u On the line between F1.

[0074] Among them, the first resistor R1 is the equivalent ground mode impedance (including line resistance and local equipment impedance) between the fault point and the measurement point. It integrates the resistance characteristics from the fault point to the relevant equipment on the inverter side (such as lines, local components of the converter, etc.), reflecting the loss and obstruction of the ground mode current in this path. Its resistance value is related to factors such as the actual line length and conductor parameters. The forward fault point Fa simulates the location of the ground mode fault occurring in the forward direction, representing the grounding fault point in the inverter side area of ​​the flexible DC transmission system. It is one of the sources of the ground mode fault current. The fault at this point causes a sudden change in voltage and current, thus generating the ground mode component. The first power supply uF1 is used to simulate the voltage mutation at the positive direction fault point Fa due to the ground fault, when the ground fault occurs, the potential difference between the positive direction fault point Fa and the ground changes, the first power supply u F1 is equivalent to the change of the potential difference, which provides the driving force for the generation of the ground model current, and the polarity and amplitude reflect the type (such as positive ground or negative ground) and severity of the fault.

[0075] In addition, Figure 4 The two dashed lines in the figure are used to define the area boundary of the rectification side (power supply side, responsible for converting alternating current to direct current) and the inversion side (load side, responsible for converting direct current to alternating current) in the system, and the entire system is divided into two functional sections according to the energy transmission direction through the dashed line, and the spatial range of fault analysis is clear, and the fault occurs in the inversion side direction, and the direct power supply effect of the rectification side on the fault is not considered. Figure 4 The waveform below the first arrow S1 represents the current traveling wave, and the arrow direction of the first arrow S1 represents the propagation direction of the current traveling wave (here, it points to the rectification side, indicating that the current traveling wave propagates from the fault point to the rectification side direction), and the curve shape of the waveform reflects the transient characteristics (such as attenuation, oscillation, etc.) of the current traveling wave.

[0076] Among them, Figure 4 b in the figure represents the reverse direction fault equivalent circuit diagram; the structure of the reverse direction fault equivalent circuit diagram is as follows:

[0077] The second power supply u F2 is connected to the positive ground of the rectifier resistor Z u The negative of F2 is connected to the first end of the rectifier resistor Z MMC The second end of the rectifier resistor Z MMC The first end of the second resistor R2 is connected to the second end of the ground model wave impedance Z C The second end of the ground model wave impedance Z C Is grounded. It needs to be explained that, Figure 4 Fb in b of the figure represents the reverse direction fault point, which is located on the line between the second power supply u F2 and the rectifier resistor Z MMC .

[0078] Among them, the second power supply u F2 is used to simulate the voltage mutation at the reverse direction fault point Fb due to the ground fault; the rectifier resistor Z MMC Represents the equivalent impedance of the rectification side modular multilevel converter (MMC); the second resistor R2 represents the ground model impedance between the fault point and the measurement point; the ground model wave impedance Z CThe wave impedance is a characteristic parameter of the ratio of the amplitude of the voltage traveling wave to the amplitude of the current traveling wave of the line, and reflects the propagation impedance of the ground mode traveling wave of the line (related to the inductance and capacitance distribution parameters of the line), and is used to describe the transmission law of the ground mode traveling wave on the DC line.

[0079] In addition, Figure 4 The waveform below the second arrow S2 in the formula (1) represents the current traveling wave, and the arrow direction of the second arrow S2 represents the propagation direction of the current traveling wave.

[0080] It needs to be explained that the positive direction fault means that the fault occurs in the “positive direction area” of the protection device of the system (usually the core area monitored by the protection device, for example, a specific section of the line connected to the local converter station, the load side, etc.); The reverse direction fault means that the fault occurs in the “reverse direction area” of the protection device (usually the area outside the monitoring range of the protection device, such as the opposite direction of the converter station, the non-responsible section, etc.).

[0081] In specific embodiments, the first current traveling wave reflection coefficient corresponding to the positive direction fault equivalent circuit can be determined first. Specifically, the positive direction fault equivalent circuit can be analyzed to determine the first current traveling wave reflection coefficient, for example, in the case of a positive direction fault including a positive pole grounding fault, the positive direction fault equivalent circuit corresponding to the positive pole grounding fault is as follows: Figure 4 In the case of the positive direction fault equivalent circuit represented by a in the formula (1), since the rectifier side is equivalent to an “open circuit”, the current traveling wave reflection coefficient is as follows:

[0082]

[0083] Among them, The current traveling wave reflection coefficient is calculated according to the above formula; then, the first fault ground mode current expression corresponding to the positive direction fault equivalent circuit can be determined according to the first current traveling wave reflection coefficient. Specifically, the current traveling wave reflection coefficient is -1, which means that the incident fault current traveling wave is fully reflected back, so the first fault ground mode current expression can be obtained as follows:

[0084]

[0085] Among them, The fault ground mode current is represented by The incident fault voltage traveling wave (i.e. the amplitude of the voltage traveling wave generated at the fault point) is represented by Thus, when the system is in a positive direction fault, the fault ground mode current is zero.

[0086] Then, the second fault ground mode current expression corresponding to the reverse direction fault equivalent circuit can be determined, for example, in the case of a reverse direction fault including a negative pole grounding fault, the reverse direction fault equivalent circuit corresponding to the negative pole grounding fault is as follows: Figure 5The equivalent circuit of the opposite direction fault represented by b is taken as an example, according to the traveling wave theory, before the next reflected wave head arrives, the power transmission line can be equivalent to a "ground resistance", and the resistance value is equal to the ground mode wave impedance The second fault ground mode current expression is specifically as follows:

[0087]

[0088] Finally, the target fault discrimination condition can be determined according to the first fault ground mode current expression and the second fault ground mode current expression. Specifically, according to the first fault ground mode current expression and the second fault ground mode current expression, it can be known that there is a significant difference in the size of the fault ground mode current when the fault is in the zone (corresponding to the positive direction fault) or outside the zone (corresponding to the opposite direction fault). Therefore, the target fault discrimination condition can be that when the fault ground mode currents on both sides (the rectifier side and the inverter side) are less than a preset current threshold, it is judged as a zone fault, or when the fault ground mode current on any one side is greater than the preset current threshold, it is judged as a zone-out fault.

[0089] It needs to be explained that according to the first fault ground mode current expression, it can be determined that in the case of ground fault including positive ground fault, when the positive direction fault, the fault ground mode current is zero. Then, according to the second fault ground mode current expression, it can be determined that in the case of ground fault including positive ground fault, when the opposite direction fault, the fault ground mode current is not zero. Therefore, the size of the fault ground mode current can be used to judge the fault direction when the single pole ground short circuit occurs, that is, the fault ground mode current is zero, and the positive direction fault is judged, or the fault ground mode current is not zero, and the opposite direction fault is judged.

[0090] In addition, in the case of ground fault including negative ground fault, when the positive direction fault, the fault ground mode current is zero, and when the opposite direction fault, the fault ground mode current expression is specifically as follows:

[0091]

[0092] In this way, by obtaining the first current traveling wave reflection coefficient, the first fault ground mode current expression is derived based on the reflection coefficient, which can accurately depict the size and variation of the ground mode current under the positive direction fault from the essential level of traveling wave propagation, and has more theoretical accuracy than the empirical judgment method.

[0093] S304, acquiring actual operation data of the flexible DC power transmission system under the ground fault condition.

[0094] In the embodiments of the present application, voltage sensors, current sensors, temperature sensors, pressure sensors and the like can be installed on key devices and lines of the flexible HVDC power transmission system; for example, the sensors are arranged at positions of sub-modules of the converter, towers of the DC line, converter transformers and the like to collect data of voltage, current, device temperature, insulation state and the like in real time; when the flexible HVDC power transmission system is in a grounding fault condition, the operation data of the system are detected through the sensors, so that actual operation data are obtained, or the flexible HVDC power transmission system can also be monitored by a Supervisory Control And Data Acquisition (SCADA) system to obtain the actual operation data.

[0095] In S305, a target discrimination result is determined according to the target fault discrimination condition and the actual operation data; the target discrimination result includes one of the following: an external fault and an internal fault.

[0096] In the embodiments of the present application, the actual operation data are discriminated according to the target fault discrimination condition, so that the target discrimination result is obtained.

[0097] Optionally, the flexible HVDC power transmission system includes an inverter side and a rectifier side; the actual operation data include a first ground mode current data set of the inverter side and a second ground mode current data set of the rectifier side; and S305 can include the following steps:

[0098] A1, a preset protection time window is obtained;

[0099] A2, current data in the first ground mode current data set within the preset protection time window are determined, so that N first current data are obtained; N is a positive integer;

[0100] A3, current data in the second ground mode current data set within the preset protection time window are determined, so that N second current data are obtained;

[0101] A4, the target discrimination result is determined according to the N first current data, the N second current data and the target fault discrimination condition.

[0102] In the embodiments of the present application, the preset protection time window can be preset or defaulted in advance.

[0103] In specific embodiments, a preset protection time window can be acquired first. Then, current data in the first ground mode current data set within the preset protection time window can be determined to obtain N first current data. Specifically, all data in the first ground mode current data set is traversed, and current data with a timestamp within the preset protection time window is extracted to obtain N first current data. Next, current data in the second ground mode current data set within the preset protection time window can be determined to obtain N second current data. Specifically, the method for obtaining N second current data can be the same as the method for obtaining N first current data, which will not be described here.

[0104] It should be explained that the collection devices (for example, current sensors) of the first ground mode current data set and the second ground mode current data set share the same time reference, and the sampling frequencies are completely consistent. Such synchronization ensures that the number of sampling points of the two data sets within the same time interval is the same, so the number of first current data and second current data within the preset protection time window is N.

[0105] Finally, a target discrimination result can be determined according to the N first current data, the N second current data, and a target fault discrimination condition.

[0106] In this way, by extracting N data from the first ground mode current data set and the second ground mode current data set, it is ensured that the two groups of data are analyzed under the same time length, the same sampling frequency, and the same sample size, avoiding comparison deviation caused by sample quantity difference, thereby improving the reliability of the discrimination result.

[0107] Optionally, the target fault discrimination condition includes an in-zone fault discrimination condition and an out-of-zone fault discrimination condition. Specifically, the in-zone fault discrimination condition can be that the fault ground mode currents on both sides are less than a preset current threshold. The out-of-zone fault discrimination condition can be that the fault ground mode current on any one side is greater than the preset current threshold. In some embodiments, step A4, determining the target discrimination result according to the N first current data, the N second current data, and the target fault discrimination condition, can include the following steps:

[0108] B1, determining the absolute value of the average value corresponding to the N first current data to obtain a first current absolute value;

[0109] B2, determining the absolute value of the average value corresponding to the N second current data to obtain a second current absolute value;

[0110] B3, obtaining a preset current threshold;

[0111] B4. When both the absolute value of the first current and the absolute value of the second current are less than the preset current threshold, it is determined that the actual operating data meets the fault discrimination condition within the area, and the target discrimination result is determined as the fault within the area.

[0112] B5. When the absolute value of the first current is greater than the preset current threshold, and / or the absolute value of the second current is greater than the preset current threshold, the actual operating data is determined to meet the external fault discrimination condition, and the target discrimination result is determined to be the external fault.

[0113] In this embodiment of the application, the absolute value of the average value corresponding to N first current data can be calculated, as follows:

[0114]

[0115] in, This represents the absolute value of the first current. Represents the first of N first current data. The values ​​of the first N current data points are then determined. Next, the absolute value of the average of these N second current data points is obtained, yielding the absolute value of the second current. Specifically, the calculation method for the absolute value of the second current is the same as that for the absolute value of the first current, and will not be repeated here. The absolute value of the second current can be denoted as... Then, the preset current threshold can be obtained.

[0116] Furthermore, the target fault discrimination condition can be expressed in the following form:

[0117]

[0118] in, This indicates a preset current threshold. According to the above target fault discrimination conditions, when both the absolute value of the first current and the absolute value of the second current are less than the preset current threshold, it can be determined that the actual operating data meets the fault discrimination conditions within the zone. At this time, the target discrimination result can be determined as a fault within the zone.

[0119] When the absolute value of the first current is greater than the preset current threshold, and / or the absolute value of the second current is greater than the preset current threshold, it can be determined that the actual operating data meets the conditions for identifying faults outside the zone. At this time, the target identification result can be determined as an external fault.

[0120] Thus, by introducing a preset current threshold, fault judgment inside and outside the zone is made based on the relationship between the preset current threshold and the absolute values ​​of the first and second currents, avoiding subjective judgment and making the decision-making logic standardized and reproducible.

[0121] Optionally, in some embodiments, please refer to Figure 5 ,Figure 5 is a simulation circuit diagram of a flexible direct current transmission system provided by an embodiment of the present application; it can be known that the structure of the system is as follows:

[0122] The first alternating current power supply AC1 is connected with the first end of the first converter transformer T1, the second end of the first converter transformer T1 is connected with the first end of the first modular multilevel converter M1; the second end of the first modular multilevel converter M1 is connected with the first end of the third resistor R3 and the first end of the first converter bridge arm inductor LMMC1; the third end of the first modular multilevel converter M1 is connected with the second end of the fourth resistor R4 and the first end of the third converter bridge arm inductor LMMC3; the second end of the third resistor R3 and the first end of the fourth resistor R4 are both grounded; the second end of the first converter bridge arm inductor LMMC1 is connected with the first end of the second converter bridge arm inductor LMMC2; the second end of the second converter bridge arm inductor LMMC2 is connected with the first end of the fifth resistor R5 and the third end of the second modular multilevel converter M2; the first end of the second modular multilevel converter M2 is connected with the first end of the second converter transformer T2; the second end of the second modular multilevel converter M2 is connected with the second end of the sixth resistor R6 and the second end of the fourth converter bridge arm inductor LMMC4; the first end of the fourth converter bridge arm inductor LMMC4 is connected with the second end of the third converter bridge arm inductor LMMC3; the second end of the fifth resistor R5 and the first end of the sixth resistor R6 are both grounded; the second end of the second converter transformer T2 is connected with the second alternating current power supply AC2.

[0123] Among them, AC1, AC2: AC1 represents the equivalent alternating current power supply on the left rectifier side, AC2 represents the equivalent alternating current power supply on the right inverter side, both of which represent the power grid or other alternating current power supply unit.

[0124] T1, T2: represents the converter transformer, which is used to realize the electrical isolation and voltage level conversion of the alternating current system and the converter, so that the converter is adapted to the voltage on the alternating current side.

[0125] M1, M2: represents the modular multilevel converter (MMC), which is the core converter equipment of the flexible direct current transmission; M1 is used to rectify the alternating current of AC1 into direct current, and M2 is used to invert the direct current into alternating current to supply AC2.

[0126] LMMC1, LMMC2, LMMC3, LMMC4: represents the converter bridge arm inductor, which is used to limit the current change rate of the bridge arm, suppress the fault current, and assist the stable operation and reactive power regulation of the converter.

[0127] R3, R4, R5, R6: represents the bridge arm equivalent resistor, which is used to simulate the resistance loss of the converter bridge arm, or to provide system damping to suppress oscillation.

[0128] Figure 5DC transmission line in the figure: represents a channel for transmitting DC power, connecting the rectifier side and the inverter side, and realizing long-distance power transmission.

[0129] Figure 5 F1, F2, F3 in the figure: represent fault simulation points, which are used to simulate faults at different positions (such as DC line section faults, faults near the converter, etc.) and analyze system fault responses.

[0130] Figure 5 in the figure u RP 、u IP 、u RN 、u IN : represents a voltage monitoring node, which collects voltage signals at positions such as the positive and negative poles of the DC, and provides data for fault detection, protection, and control.

[0131] Figure 5 in the figure i RP 、i IP 、i RN 、i IN : represents a current monitoring node, which collects current signals at positions such as the positive and negative poles of the DC, and is used for fault current analysis and protection criterion calculation.

[0132] Figure 5 The positive direction arrow in the figure is used to define the reference positive direction of electrical quantities such as current or power, which is the basis for analyzing the flow direction of electrical quantities (such as current, power, and current direction during faults) in the system. For example, in the current monitoring of the system, the arrow direction is the preset positive direction of the current. When the actual current and the arrow are in the same direction, the value is positive; when they are in opposite directions, the value is negative, which facilitates subsequent analysis and calculation of the current.

[0133] In some embodiments, the simulation circuit diagram of a flexible DC power transmission system shown in the figure can be constructed in a power system auxiliary design simulation software (Power System Computer Aided Design, PSCAD) or an electromagnetic transient simulation software (Electro-Magnetic Transients in DC Systems, EMTDC) in the DC system. Figure 6 The simulation circuit diagram of a flexible DC power transmission system shown in the figure, wherein the DC transmission line can adopt a frequency-dependent parameter model, the length is 650 km, and the inductance value of the current limiting reactor (i.e. the inductance of the above-mentioned four converter bridge arms) at both ends of the line can be set to 100 mH, which is used to limit the current rise rate and peak value during faults and avoid excessive fault current damage to equipment; the protection sampling frequency of the system can be set to 50 kHz, It can be set to 0.035kA.

[0134] Using PSCAD software, various types of fault simulations can be performed on the simulation circuit diagram of the flexible DC transmission system to verify the correctness of the fault identification method for the flexible DC transmission system inside and outside the zone provided in this application embodiment. The fault simulation points can be: F1 (100km, 300km, 500km away from the rectifier side), F2 (short circuit on the rectifier side), and F3 (short circuit on the inverter side); the fault resistance can be one of the following: 0Ω (indicating a metallic short circuit, the fault point is fully conductive) or 500Ω (indicating a high-resistance short circuit, the fault point has poor contact); the fault types include positive grounding fault and negative grounding fault. The simulation results of the software are shown in Table 1:

[0135]

[0136] According to the judgment results in Table 1, when there is a fault within the zone (F1 fault): regardless of the fault location (100km, 300km, 500km), transition resistance (0Ω or 500Ω), or polarity (positive or negative ground). A ioR and A ioI The values ​​are all very small, far below the protection threshold. Even under the worst operating conditions, the protection sensitivity remains high. Therefore, when a fault occurs within the protection zone, the protection operates reliably and accurately determines the fault polarity. Reliable protection operation means that when a fault occurs within the system, the protection device can accurately and stably trigger preset protection operations (such as quickly isolating the faulty section, issuing a fault alarm, etc.) based on the fault characteristics. There is no situation where the operation fails to occur (refusal to operate), effectively isolating the fault and ensuring system safety.

[0137] In the event of an external fault (F2, F3 fault): regardless of whether it is a short circuit on the rectifier side (F2) or a short circuit on the inverter side (F3), and regardless of the size of the transition resistance, A ioR or A ioI The values ​​are all significantly large, far exceeding the preset current threshold. (The difference is several tens of times), therefore the protection is reliable and does not operate, avoiding misjudgment. Here, "reliable protection and no operation" means that when an external fault occurs in the system, the protection device will stably maintain its operation without triggering the protection operation for the internal fault based on the characteristics of the external fault. There will be no situation where it should operate but does so incorrectly (false operation), avoiding unnecessary interference or damage to the normally operating system due to misjudgment.

[0138] Therefore, it can be said that the fault discrimination method for flexible DC transmission systems provided in this application can accurately distinguish between faults inside and outside the zone, and has strong adaptability to high-resistance faults and faults in different locations, with high sensitivity and high reliability.

[0139] Optionally, in some embodiments, fault simulation can be performed on the simulation circuit diagram of the flexible DC transmission system using PSCAD simulation software to obtain the simulation waveform of the ground mode current. For details, please refer to [link to relevant documentation]. Figure 6 , Figure 6 This is a simulation waveform diagram of the ground mode current under a fault condition provided in an embodiment of this application, wherein, Figure 7 The simulated waveform diagram shown is the simulated waveform diagram of the ground mode current under the condition of a unipolar metallic short circuit fault within the zone. The first curve L1 represents the waveform diagram of the ground mode current on the inverter side: after the fault occurs, the ground mode current fluctuates in a small range around 0, and the value is extremely small. The second curve L2 represents the waveform diagram of the ground mode current on the rectifier side: after the fault occurs, the ground mode current changes slightly around 0, without a significant increasing trend. It can be seen that during a fault within the zone, the ground mode currents on both the rectifier side and the inverter side are very small, far below the protection threshold. Therefore, it can be judged as a "fault within the zone", and the protection device of the system can be controlled to accurately and stably execute the corresponding protection action.

[0140] Optionally, in some embodiments, please refer to Figure 7 , Figure 7 This is a simulation waveform diagram of the ground mode current under another fault condition provided in an embodiment of this application, wherein, Figure 8 The simulated waveform diagram shown is the simulated waveform diagram of the ground mode current under the condition of an external unipolar metallic short circuit fault. The third curve L3 represents the waveform diagram of the inverter side ground mode current: after the fault occurs (about 1 second), the current rises sharply and eventually reaches a high value of about 2.5kA; the fourth curve L4 represents the waveform diagram of the rectifier side ground mode current: after the fault, it only fluctuates slightly and the value remains at a low level. It can be seen that when there is an external fault, the ground mode current on the fault side (inverter side) will increase significantly, while the current on the non-fault side (rectifier side) will change very little. Therefore, it can be judged as an "external fault" and the protection device of the system should be strictly controlled according to the preset protection logic and not trigger the protection action for faults within the zone.

[0141] Optionally, after determining the target discrimination result based on the target fault discrimination criteria and the actual operating data, the method further includes:

[0142] C1. Apply preset noise to the actual operating data to obtain reference operating data;

[0143] C2. Determine the reference judgment result based on the target fault judgment condition and the reference operating data;

[0144] C3, determining whether the reference discrimination result is consistent with the target discrimination result;

[0145] C4, if consistent, determining that the target discrimination result is reliable;

[0146] C5, if inconsistent, determining that the target discrimination result is unreliable; obtaining new operation data of the flexible DC power transmission system, and determining a new discrimination result according to the target fault discrimination condition and the new operation data.

[0147] In the embodiments of the present application, the preset noise can be preset or defaulted in advance.

[0148] In specific embodiments, a preset noise can be applied to the actual operation data to obtain reference operation data. Specifically, the preset noise can be a 20db (signal-to-noise ratio) noise. The preset noise is superimposed on the actual operation data to obtain noisy operation data, i.e., the reference operation data. Then, the reference discrimination result can be determined according to the target fault discrimination condition and the reference operation data. Specifically, the method of obtaining the reference discrimination result can be the same as the method of obtaining the target discrimination result, which will not be described here.

[0149] Then, the reference discrimination result and the target discrimination result can be compared to determine whether they are consistent. If the reference discrimination result and the target discrimination result are consistent, it is determined that the target discrimination result is reliable.

[0150] If not consistent, it is determined that the target discrimination result is unreliable. New operation data of the flexible DC power transmission system can be obtained, and then a new discrimination result can be determined according to the target fault discrimination condition and the new operation data.

[0151] In some embodiments, the actual operation data can be affected by sensor noise, electromagnetic interference, etc. The preset noise can simulate these disturbances. By generating reference operation data, the performance of the target fault discrimination condition in the "noisy environment" can be verified. If the two (reference discrimination result and target discrimination result) are consistent, it proves that even if there is interference, the target fault discrimination condition can still output correct results stably, and the reliability of the target discrimination result is verified. If not consistent, it means that the current discrimination result may be affected by noise and fail, and needs to be further confirmed. This comparison provides quantitative verification for the reliability of the result, avoiding blindly accepting the possible wrong discrimination.

[0152] Optionally, step B3, the obtaining of the preset current threshold value can include the following steps:

[0153] D1, obtaining a system rated current value corresponding to the flexible DC power transmission system;

[0154] D2, obtaining a target unbalanced current coefficient and a target setting coefficient;

[0155] D3, determining the preset current threshold according to the target unbalanced current coefficient, the target setting coefficient and the system rated current value.

[0156] In the embodiments of the present application, the system rated current value corresponding to the flexible DC power transmission system can be obtained. Specifically, the system design manual of the flexible DC power transmission system can be obtained, and the system rated current value can be obtained from the system design manual, or the system rated current value can be indirectly calculated from the system rated power and the rated voltage of the flexible DC power transmission system, for example, the system rated current value is obtained by dividing the system rated power by the rated voltage.

[0157] Then, the target unbalanced current coefficient and the target setting coefficient can be obtained, and then the preset current threshold can be determined according to the target unbalanced current coefficient, the target setting coefficient and the system rated current value, specifically as follows:

[0158]

[0159] wherein, the preset current threshold is represented by Ith; the target setting coefficient is represented by K; the system rated current value is represented by I.

[0160] In this way, the system rated current value is adjusted by the target unbalanced current coefficient (reflecting the current fluctuation in normal operation) and the target setting coefficient (adapted to the protection sensitivity and reliability), so that the final obtained preset current threshold not only fits the actual operation characteristics of the system, but also can accurately distinguish between faults and normal fluctuations, and improve the accuracy of the discrimination result.

[0161] Optionally, the step D2 of obtaining the target unbalanced current coefficient and the target setting coefficient can include the following steps:

[0162] E1, obtaining a preset unbalanced current coefficient and a preset setting coefficient;

[0163] E2, obtaining a target power source rated capacity and a target power source accuracy corresponding to the flexible DC power transmission system;

[0164] E3, determining a deviation degree between the target power source rated capacity and a preset rated capacity to obtain a target deviation degree;

[0165] E4, determining a first adjustment factor corresponding to the target deviation degree;

[0166] E5, determining a second adjustment factor corresponding to the target power source accuracy;

[0167] E6, adjust the preset unbalanced current coefficient according to the first adjustment factor and the second adjustment factor to obtain the target unbalanced current coefficient;

[0168] E7, determine a target fault protection requirement corresponding to the flexible DC power transmission system;

[0169] E8, determine a target optimization factor corresponding to the target fault protection requirement;

[0170] E9, adjust the preset setting coefficient according to the target optimization factor to obtain the target setting coefficient.

[0171] In the embodiments of the application, the preset unbalanced current coefficient and the preset setting coefficient can be preset or defaulted in advance.

[0172] In specific embodiments, the preset unbalanced current coefficient and the preset setting coefficient can be obtained first; then, the target power source rated capacity and the target power source accuracy corresponding to the flexible DC power transmission system can be obtained, specifically, the power source rated capacity and the power source accuracy can be queried from the system design manual, so that the target power source rated capacity and the target power source accuracy are obtained, or the target power source rated capacity and the target power source accuracy of the flexible DC power transmission system can also be queried through the SCADA system.

[0173] Then, the deviation between the target power source rated capacity and the preset rated capacity can be determined, specifically as follows:

[0174]

[0175] wherein, denotes the target deviation; denotes the target power source rated capacity; denotes the preset rated capacity; according to the above formula, the target deviation can be obtained; further, the first adjustment factor corresponding to the target deviation can be determined, specifically, a preset mapping relationship between the preset deviation and the adjustment factor can be stored in advance, and the first adjustment factor corresponding to the target deviation is determined based on the mapping relationship; then, the second adjustment factor corresponding to the target power source accuracy can be determined, and the same, a preset mapping relationship between the power source accuracy and the adjustment factor can also be stored in advance, and the second adjustment factor corresponding to the target power source accuracy is determined based on the mapping relationship, wherein the value range of the first adjustment factor and the second adjustment factor can be -0.15~0.15.

[0176] Then, the preset unbalanced current coefficient can be adjusted according to the first adjustment factor and the second adjustment factor, and the specific calculation formula is as follows:

[0177] The target unbalanced current coefficient = the preset unbalanced current coefficient × (1 + the first adjustment factor) × (1 + the second adjustment factor);

[0178] According to the above formula, the target unbalanced current coefficient can be obtained; then, the target fault protection requirement corresponding to the flexible DC power transmission system can be determined, specifically, the target application scenario corresponding to the flexible DC power transmission system can be obtained, for example, by checking the power source type (such as wind power, photovoltaic base) accessed by the system, the load property (such as urban center load, island power supply) or the networking range (such as regional power grid interconnection, submarine cable power transmission), the application scenario (such as new energy grid-connected scenario, island power supply scenario) is inferred according to these information, so that the target application scenario is obtained, for example, assuming that the power source accessed by the system is a large-scale offshore wind farm, due to the characteristics of offshore wind power, its requirements for stability, long-distance transmission capability and adaptability to complex sea conditions of power transmission technology are higher, and the flexible DC power transmission technology can effectively solve the problem of offshore wind power grid connection and realize reliable power delivery, at this time, according to this power source type, it can be inferred that the target application scenario of the flexible DC power transmission system is offshore wind power grid connection scenario, then, the target fault protection requirement can be determined according to the target application scenario, specifically, the mapping relationship between the preset application scenario and the fault protection requirement can be stored in advance, and the target fault protection requirement corresponding to the target application scenario is determined based on the mapping relationship, for example, assuming that the target application scenario is an island power supply scenario (for example, to supply power to residents and industrial loads on remote islands, without other standby power sources), its corresponding target fault protection requirement can be: after the fault occurs, the fault must be quickly isolated within a short time to prevent the spread of the fault and cause the island to be powered off; at the same time, it needs to have good fault tolerance (i.e. the failure of a single protection element does not affect the overall protection action), and can support system black start (recovery of power supply without external power supply) after the fault is cleared, to ensure the continuity and reliability of island power supply.

[0179] Then, the target optimization factor corresponding to the target fault protection requirement can be determined, for example, the mapping relationship between the preset fault protection requirement and the optimization factor can be stored in advance, and the target optimization factor corresponding to the target fault protection requirement is determined based on the mapping relationship, wherein the value range of the target optimization factor can be -0.3~0.3; finally, the preset setting coefficient can be adjusted according to the target optimization factor, and the specific calculation formula is as follows:

[0180] The target setting coefficient = the preset setting coefficient × (1 + the target optimization factor);

[0181] According to the above formula, the target setting coefficient can be obtained.

[0182] Therefore, by dynamically adjusting the unbalanced current coefficient combined with the actual characteristics of the power supply (deviation of rated capacity, power supply accuracy), and optimizing the setting coefficient combined with the specific fault protection requirements, the two key parameters are no longer fixed preset values, but accurately adapt to the actual operation state and protection requirements of the system, so that the current threshold determined based on them is more reliable, and the accuracy and scene adaptability of fault discrimination are improved.

[0183] In summary, the in-zone and out-zone fault discrimination method of the flexible DC power transmission system described in the present application, by obtaining the system topology data of the flexible DC power transmission system, for different grounding fault conditions such as positive pole grounding fault and negative pole grounding fault, the corresponding ground model fault equivalent circuit is constructed, then the target fault discrimination condition is determined according to the ground model fault equivalent circuit, then the actual operation data of the flexible DC power transmission system under the grounding fault condition is obtained, and it is combined with the target fault discrimination condition for judgment. The actual operation data contains real-time electrical information of the system. By comparing and analyzing the actual operation data and the target fault discrimination condition, the fault can be more reliably identified. This combination of theoretical model (i.e. ground model fault equivalent circuit) and actual data can adapt to various situations during system operation, reduce the interference of noise, transition resistance and other factors on fault identification, thereby improving the reliability of fault identification.

[0184] Please refer to Figure 8 , Figure 9 is a functional unit composition block diagram of a flexible DC power transmission system in-zone and out-zone fault discrimination device 800 provided by the embodiment of the present application. The flexible DC power transmission system in-zone and out-zone fault discrimination device 800 comprises: an acquisition unit 801, a determination unit 802, and a discrimination unit 803, wherein:

[0185] The acquisition unit 801 is configured to acquire system topology data corresponding to the flexible DC power transmission system.

[0186] The determination unit 802 is configured to determine, according to the system topology data, a ground model fault equivalent circuit corresponding to the flexible DC power transmission system under a grounding fault condition; the grounding fault condition includes one of the following: positive pole grounding fault, negative pole grounding fault; and determine a target fault discrimination condition according to the ground model fault equivalent circuit.

[0187] The acquisition unit 801 is further configured to acquire actual operation data of the flexible DC power transmission system under the grounding fault condition.

[0188] The discrimination unit 803 is configured to determine a target discrimination result according to the target fault discrimination condition and the actual operation data; the target discrimination result includes one of the following: out-zone fault, in-zone fault.

[0189] In specific implementation, the in-zone and out-zone fault discrimination device 800 of the flexible DC power transmission system described in the embodiments of the present application can also perform other embodiments described in the in-zone and out-zone fault discrimination method of the flexible DC power transmission system provided by the embodiments of the present application, which will not be described here.

[0190] Please refer to Figure 9 , ​ is another structural schematic diagram of an electronic device provided by the embodiments of the present application, which can include a processor, a memory, a communication interface and one or more programs, the processor, the memory and the communication interface can be connected with each other through a bus; the above one or more programs are stored in the above memory and configured to be executed by the above processor; in the embodiments of the present application, the above program includes instructions for executing the following steps:

[0191] obtaining system topology data corresponding to the flexible DC power transmission system;

[0192] determining a ground model fault equivalent circuit corresponding to the flexible DC power transmission system under a ground fault condition according to the system topology data; the ground fault condition includes one of the following: positive ground fault, negative ground fault;

[0193] determining a target fault discrimination condition according to the ground model fault equivalent circuit;

[0194] obtaining actual operation data of the flexible DC power transmission system under the ground fault condition;

[0195] determining a target discrimination result according to the target fault discrimination condition and the actual operation data; the target discrimination result includes one of the following: out-zone fault, in-zone fault.

[0196] It should be explained that the electronic device can also perform part or all of the steps of any of the above method embodiments.

[0197] The embodiments of the present application also provide a computer readable storage medium, wherein the computer readable storage medium stores a computer program for electronic data exchange, and the computer program causes a computer to perform part or all of the steps of any of the above method embodiments, and the above computer includes the electronic device.

[0198] The embodiments of the present application also provide a computer program product, which includes a non-transitory computer readable storage medium storing a computer program, and the computer program is operable to cause a computer to perform part or all of the steps of any of the above method embodiments. The computer program product can be a software installation package, and the above computer includes the electronic device.

[0199] It should be noted that, for the foregoing method embodiments, for the sake of simple description, they are all described as a combination of a series of actions, but those skilled in the art should know that the present application is not limited to the order of the actions described, because according to the present application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should know that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily essential to the present application.

[0200] In the above embodiments, the description of each embodiment has its own focus, and the parts not described in detail in a certain embodiment can be referred to the related description of other embodiments.

[0201] In several embodiments provided in the present application, it should be understood that the disclosed apparatus can be implemented by other means. For example, the apparatus embodiments described above are only illustrative, for example, the division of the above units is only a logical function division, and actual implementation can have another division manner, for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the displayed or discussed each other can be indirect coupling or communication connection through some interfaces, apparatuses or units, which can be electrical or other forms.

[0202] Those of ordinary skill in the art can understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing relevant hardware, and the program can be stored in a computer readable storage medium. When the program is executed, it can include the processes of the above method embodiments. The foregoing storage medium includes ROM, random access memory (RAM), magnetic disk or optical disk, and various program code storage media.

[0203] The steps of the method or algorithm described in the embodiments of the present application can be implemented in a hardware manner or by a processor executing software instructions. The software instructions can be composed of corresponding software modules, and the software modules can be stored in a RAM, a flash memory, a ROM, an electrically EPROM (EEPROM), a register, a hard disk, a mobile hard disk, a CD-ROM (CD-ROM), or any other form of storage medium well known in the art. An exemplary storage medium is coupled to the processor, so that the processor can read information from the storage medium and write information to the storage medium. Of course, the storage medium can also be an integral part of the processor. The processor and the storage medium can be located in an ASIC. In addition, the ASIC can be located in a terminal device or a management device. Of course, the processor and the storage medium can also exist as discrete components in the terminal device or the management device.

[0204] Those skilled in the art should be aware that, in one or more examples described above, the functions described in the embodiments of the present application can be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented by software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When loaded and executed on a computer, the computer program instructions produce the processes or functions described in the embodiments of the present application in whole or in part.

[0205] The computer described above can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions can be stored in a computer-readable storage medium or transferred from one computer-readable storage medium to another. For example, the computer instructions can be transferred from one website, computer, server, or data center to another through wired (such as coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (such as infrared, wireless, microwave, etc.) manner. The computer-readable storage medium can be any available medium accessible by a computer or a data storage device such as a server, data center, etc. integrated with one or more available media sets.

[0206] Among them, the available media can be magnetic media (such as floppy disk, hard disk, magnetic tape), optical media (such as digital video disc (DVD)), or semiconductor media (such as solid state disk (SSD)), etc.

[0207] The various modules / units included in the various devices and products described in the above embodiments can be software modules / units or hardware modules / units, or partially software modules / units and partially hardware modules / units. For example, for the various devices and products applied to or integrated in a chip, the various modules / units included therein can all be implemented in the form of hardware such as circuitry, or at least some of the modules / units can be implemented in the form of software running on a processor integrated in the chip, and the remaining (if any) modules / units can be implemented in the form of hardware; for the various devices and products applied to or integrated in a chip module, the various modules / units included therein can all be implemented in the form of hardware such as circuitry, and different modules / units can be located in the same component (e.g., a chip, a circuit module, etc.) or different components of the chip module, or at least some of the modules / units can be implemented in the form of software running on a processor integrated in the chip module, and the remaining (if any) modules / units can be implemented in the form of hardware; for the various devices and products applied to or integrated in a terminal device, the various modules / units included therein can all be implemented in the form of hardware such as circuitry, and different modules / units can be located in the same component (e.g., a chip, a circuit module, etc.) or different components of the terminal device, or at least some of the modules / units can be implemented in the form of software running on a processor integrated in the terminal device, and the remaining (if any) modules / units can be implemented in the form of hardware.

[0208] The above detailed description of the specific implementation of the present application has further explained the purpose, technical solutions, and beneficial effects of the embodiments of the present application. It should be understood that the above description is only a specific implementation of the embodiments of the present application and is not intended to limit the protection scope of the embodiments of the present application. Any modification, equivalent replacement, improvement, etc. made on the basis of the technical solutions of the embodiments of the present application shall be included in the protection scope of the embodiments of the present application.

Claims

1. A method of discriminating between internal and external faults in a flexible DC power transmission system, characterized by, The method comprises: obtaining system topology data corresponding to a flexible direct current power transmission system; determining, according to the system topology data, a ground mode fault equivalent circuit of the flexible direct current power transmission system in a ground fault condition; the ground fault condition includes one of the following: positive pole ground fault, negative pole ground fault; determining a target fault discrimination condition according to the ground mode fault equivalent circuit; the ground mode fault refers to a fault accompanied by a ground mode current; the ground mode current is a component reflecting current circulation through the ground loop, which is extracted from system current through modal decomposition; obtaining actual operation data of the flexible direct current power transmission system in the ground fault condition; determining a target discrimination result according to the target fault discrimination condition and the actual operation data; the target discrimination result includes one of the following: external fault, internal fault; wherein the ground mode fault equivalent circuit includes a positive direction fault equivalent circuit and a reverse direction fault equivalent circuit; the target fault discrimination condition is determined according to the ground mode fault equivalent circuit, comprising: determining a first current traveling wave reflection coefficient corresponding to the positive direction fault equivalent circuit; determining a first fault ground mode current expression corresponding to the positive direction fault equivalent circuit according to the first current traveling wave reflection coefficient; determining a second fault ground mode current expression corresponding to the reverse direction fault equivalent circuit; determining the target fault discrimination condition according to the first fault ground mode current expression and the second fault ground mode current expression; wherein the flexible direct current power transmission system includes an inverter side and a rectifier side; the actual operation data includes a first ground mode current data set of the inverter side and a second ground mode current data set of the rectifier side; the target discrimination result is determined according to the target fault discrimination condition and the actual operation data, comprising: obtaining a preset protection time window; determining current data in the first ground mode current data set within the preset protection time window to obtain N first current data; N is a positive integer; determining current data in the second ground mode current data set within the preset protection time window to obtain N second current data; determining the target discrimination result according to the N first current data, the N second current data and the target fault discrimination condition; wherein the target fault discrimination condition includes an internal fault discrimination condition and an external fault discrimination condition; the target discrimination result is determined according to the N first current data, the N second current data and the target fault discrimination condition, comprising: determining an absolute value of an average value corresponding to the N first current data to obtain a first current absolute value; determining an absolute value of an average value corresponding to the N second current data to obtain a second current absolute value; obtaining a preset current threshold value; when the first current absolute value and the second current absolute value are both less than the preset current threshold value, it is determined that the actual operation data satisfies the internal fault discrimination condition, and the target discrimination result is determined as the internal fault. determining that the actual operation data meets the out-of-area fault discrimination condition when the first current absolute value is greater than the preset current threshold value and / or the second current absolute value is greater than the preset current threshold value, and determining the target discrimination result as the out-of-area fault; wherein the obtaining of the preset current threshold value comprises: obtaining a system rated current value corresponding to the flexible DC power transmission system; obtaining a target unbalanced current coefficient and a target setting coefficient; determining the preset current threshold value according to the target unbalanced current coefficient, the target setting coefficient and the system rated current value; wherein the obtaining of the target unbalanced current coefficient and the target setting coefficient comprises: obtaining a preset unbalanced current coefficient and a preset setting coefficient; obtaining a target power source rated capacity and a target power source accuracy corresponding to the flexible DC power transmission system; determining a deviation degree between the target power source rated capacity and a preset rated capacity to obtain a target deviation degree; determining a first adjustment factor corresponding to the target deviation degree; determining a second adjustment factor corresponding to the target power source accuracy; adjusting the preset unbalanced current coefficient according to the first adjustment factor and the second adjustment factor to obtain the target unbalanced current coefficient; determining a target fault protection requirement corresponding to the flexible DC power transmission system; determining a target optimization factor corresponding to the target fault protection requirement; adjusting the preset setting coefficient according to the target optimization factor to obtain the target setting coefficient.

2. The method of claim 1, wherein, after the target discrimination result is determined according to the target fault discrimination condition and the actual operation data, the method further comprises: applying a preset noise to the actual operation data to obtain reference operation data; determining a reference discrimination result according to the target fault discrimination condition and the reference operation data; determining whether the reference discrimination result is consistent with the target discrimination result; if consistent, determining that the target discrimination result is reliable; if inconsistent, determining that the target discrimination result is unreliable; obtaining new operation data of the flexible DC power transmission system, and determining a new discrimination result according to the target fault discrimination condition and the new operation data.

3. A device for internal / external fault discrimination of a flexible DC power transmission system for carrying out the method according to claim 1 or 2, characterized in that The device comprises an obtaining unit, a determining unit and a discrimination unit, wherein: the obtaining unit is configured to obtain system topology data corresponding to the flexible DC power transmission system; the determining unit is configured to determine a ground mode fault equivalent circuit of the flexible DC power transmission system under a ground fault condition according to the system topology data; the ground fault condition comprises one of a positive ground fault and a negative ground fault; determine a target fault discrimination condition according to the ground mode fault equivalent circuit; the ground mode fault refers to a fault accompanied by a ground mode current; the ground mode current is a component reflecting the flow of current through the ground loop extracted from the system current through modal decomposition; the obtaining unit is further configured to obtain actual operation data of the flexible DC power transmission system under the ground fault condition; the discrimination unit is configured to determine a target discrimination result according to the target fault discrimination condition and the actual operation data; the target discrimination result comprises one of an out-of-area fault and an in-area fault.

4. An electronic device, comprising: ​ a processor, a memory, a communication interface, and one or more programs; the one or more programs are stored in the memory and configured to be executed by the processor, the programs comprising instructions for performing the steps in the method as claimed in claim 1 or 2.

5. A computer readable storage medium, characterized in that, a computer program for electronic data interchange, wherein the computer program causes a computer to perform the method as claimed in claim 1 or 2.

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