Direct current power distribution network fault pole selection method, system, device and medium

Abstract

The application discloses a direct-current power distribution network fault pole selection method, system, device and medium, comprising: collecting positive and negative pole coupling electrical quantities of each line in the fault pole selection power distribution network in real time, and decoupling the positive and negative pole coupling electrical quantities into zero mode and one mode; judging whether the direct-current power distribution network system has a fault according to the voltage of the one mode; when the fault occurs, writing boundary condition equations of fault points of each fault type, and calculating one mode fault component voltage, one mode current, zero mode voltage and zero mode current at the fault points corresponding to the fault type based on the boundary condition equations; constructing a comparison formula of the zero mode voltage and the line mode fault component voltage according to the one mode fault component voltage, the one mode current, the zero mode voltage and the zero mode current corresponding to each fault type; constructing a fault pole selection criterion based on the comparison formula, and determining a fault pole selection result according to the fault pole selection criterion. The application solves the problems that the existing technology has poor adaptability and cannot identify bipolar faults.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of direct current power distribution network, and particularly relates to a direct current power distribution network fault pole selection method, system, device and medium. BACKGROUND

[0002] With the development of power electronic technology and direct current devices, the power supply and load of the power system have changed greatly, and the proportion of distributed power supply in power supply has gradually increased. Direct current power distribution network has the advantages of good power supply reliability, high power quality, flexible control, easy access to distributed power supply, and low line loss, and has gradually become a research focus at home and abroad. However, the direct current power distribution network is a low-damping and weak-inertia system, and its fault develops fast and has a wide influence range. Therefore, accurate identification of the fault of the flexible direct current power distribution network is a current research focus.

[0003] Single-pole grounding short circuit is the most frequent fault type in direct current power distribution network, and although the probability of bipolar short circuit is not high, it is usually permanent fault, which cannot be ignored. For the research on fault pole selection of direct current power distribution network, document [1] Song Guobing, Hou Junjie, Guo Bing. Based on active detection type, longitudinal protection of flexible direct current power grid [J]. Power grid technology, 2020, 44 (10): 4001-4010. After injecting a signal, the spireman correlation coefficient obtained at the positive and negative pole protection installation is tested to determine the fault pole, but it depends on signal injection and is easy to be disturbed by system noise. Moreover, a signal generator needs to be configured, which increases the hardware cost. Document [2] Jia Ke, Chen Miao, Shi Zhiming, et al. Single-ended protection scheme for flexible direct current transmission line based on voltage integral concave-convex of current limiting reactor [J]. Power grid technology, 2021, 45 (11): 4498-4505. The concave-convex of the voltage integral value on the positive and negative poles is used to determine the fault occurrence pole. However, the voltage integral method requires high-precision sensors and high sampling synchronization, and the actual power distribution network parameter fluctuation (such as line impedance and boundary element) may reduce the reliability.

[0004] Obviously, the above-mentioned shortcomings highlight the deficiencies of the current fault pole selection technology in universality, reliability and engineering practicability. Future research needs to focus on breaking through the adaptability of grounding mode and bipolar fault identification. SUMMARY

[0005] The present application provides a direct current power distribution network fault pole selection method, system, device and medium, which is used to solve the problem that the grounding mode adaptability of the prior art is poor and the bipolar fault cannot be identified.

[0006] Therefore, the first aspect of the present application provides a direct current power distribution network fault pole selection method, comprising:

[0007] S1, real-time collection of positive and negative coupling electrical quantities of each line in the power distribution network of the fault candidate pole, and decoupling of the positive and negative coupling electrical quantities into zero mode and one mode through a pole-mode transformation matrix;

[0008] S2, comparing the one-mode voltage with a preset criterion, and judging whether a fault occurs in the DC power distribution network system according to a comparison result, if yes, executing step S3, otherwise executing step S1;

[0009] S3, listing boundary condition equations of fault points of each fault type, and calculating one-mode fault component voltage, one-mode current and zero-mode voltage and zero-mode current at the fault points of the corresponding fault type based on the boundary condition equations;

[0010] S4, constructing a comparison formula of zero-mode voltage and line-mode fault component voltage according to the one-mode fault component voltage, the one-mode current and the zero-mode voltage and the zero-mode current corresponding to each fault type;

[0011] S5, constructing a fault selection criterion based on the comparison formula, and determining a fault selection result according to the fault selection criterion.

[0012] Optionally, the fault types include positive pole grounding fault, negative pole grounding fault, pole-to-pole fault and bipolar grounding fault.

[0013] Optionally, an expression of the comparison formula is:

[0014] ;

[0015] In the formula, is zero-mode voltage, is one-mode fault component voltage at the fault point, is zero-mode current, and are one-mode wave impedance and zero-mode wave impedance of the DC transmission line respectively, is one-mode fault component current at the fault point generated by the fault, is fault point voltage, is transition resistance.

[0016] Optionally, an expression of the fault selection criterion is:

[0017] ;

[0018] In the formula, is zero-mode voltage, is one-mode fault component voltage at the fault point.

[0019] The second aspect of the present application provides a DC power distribution network fault pole selection system, the system comprises:

[0020] A decoupling unit is configured to collect positive and negative pole coupling electrical quantities of each line in the power distribution network of the fault candidate pole in real time, and decouple the positive and negative pole coupling electrical quantities into zero mode and one mode through a pole-mode transformation matrix;

[0021] A judging unit is configured to compare the voltage of the one mode with a preset criterion, and determine whether a fault occurs in the DC power distribution network system according to a comparison result, and if yes, trigger the first construction unit, and if not, trigger the decoupling unit;

[0022] The first construction unit is configured to list boundary condition equations at fault points of each fault type, and calculate one mode fault component voltages, one mode currents and zero mode voltages and zero mode currents at the fault points of the corresponding fault type based on the boundary condition equations;

[0023] The second construction unit is configured to construct a comparison formula of zero mode voltage and line mode fault component voltage according to the one mode fault component voltages, the one mode currents and the zero mode voltages and the zero mode currents corresponding to each fault type;

[0024] The analysis unit is configured to construct a fault selection criterion based on the comparison formula, and determine a fault selection result according to the fault selection criterion.

[0025] Optionally, the fault types include positive pole ground fault, negative pole ground fault, pole-to-pole fault and bipolar ground fault.

[0026] Optionally, the comparison formula has an expression as follows:

[0027] ;

[0028] In the formula, is a zero mode voltage, is a one mode fault component voltage at a fault point, is a zero mode current, and are one mode wave impedance and zero mode wave impedance of a DC transmission line respectively, is a one mode fault component current at the fault point generated by the fault, is a fault point voltage, is a transition resistance.

[0029] Optionally, the fault selection criterion has an expression as follows:

[0030] ;

[0031] In the formula, is a zero mode voltage, is a one mode fault component voltage at a fault point.

[0032] The third aspect of the present application provides a direct current power distribution network fault pole selection device, the device comprising a processor and a memory:

[0033] The memory is used for storing program codes and transmitting the program codes to the processor.

[0034] The processor is used for executing the steps of the direct current power distribution network fault pole selection method according to the instructions in the program codes.

[0035] The fourth aspect of the present application provides a computer readable storage medium, which is used for storing program codes, and the program codes are used for executing the direct current power distribution network fault pole selection method of the first aspect.

[0036] From the above technical solutions, the present application has the following advantages:

[0037] The direct current power distribution network fault pole selection method provided by the embodiment of the present application firstly collects the positive and negative pole coupling electrical quantities of each line in the low-voltage direct current power distribution network in real time, decouples the positive and negative pole coupling electrical quantities into independent modes through a pole-mode transformation matrix, wherein the zero mode reflects the ground fault current path characteristics and is sensitive to single-pole / double-pole ground faults; and the line mode characterizes the voltage difference between poles and is sensitive to inter-pole short-circuit faults. The decoupled mode quantities are determined only by the fault physical characteristics and are irrelevant to the system grounding mode (resistance grounding, floating ground, etc.), thus completely breaking through the dependence of the prior art on a specific grounding mode. Then, whether the system has a fault is judged according to the one-mode, when a fault occurs, the expressions of the zero-mode voltage and the one-mode fault component voltage in the cases of positive pole grounding, negative pole grounding, inter-pole fault and double-pole grounding are derived, and the polarity of the zero-mode voltage and the one-mode fault component voltage is compared to realize fault pole selection. Since the same criterion is used for single-pole grounding, double-pole short-circuit and double-pole grounding faults, it is unnecessary to switch algorithms for different faults, and the blind area of the prior art for double-pole fault identification is solved.

[0038] Compared with the prior art, the fault pole selection method of the present application realizes fault line selection according to the line voltage and current after a fault, and the method of comparing the zero-mode voltage with the line-mode fault component voltage is simple and easy to implement, and has low requirements on the sampling rate (no MHz-level sampling required for traveling wave protection), and is suitable for engineering deployment; high-reliable pole selection is realized only by using local electrical quantities, the active injection which is susceptible to interference and the integral operation which is sensitive to parameters are abandoned, and the noise immunity and robustness are improved by using the essential characteristics (polarity relationship) of the fault; the scene limitation of the prior art is caused by the grounding mode dependence and the double-pole fault blind area, and the present application realizes global application through mathematical decoupling and physical characteristic extraction. Thus, the problem that the grounding mode adaptability of the prior art is poor and the double-pole fault cannot be identified is solved. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only show some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without any creative effort.

[0040] Figure 1 A flowchart of a direct current power distribution network fault pole selection method provided by the embodiment of the present application is shown in the figure.

[0041] Figure 2 A fault component network diagram at a fault point of a direct current transmission line provided by the embodiment of the present application is shown in the figure.

[0042] Figure 3 A structure diagram of a direct current power distribution network fault pole selection system provided by the embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0043] In order to make the purposes, features and advantages of the present application more obvious and easy to understand, 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 following 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 those skilled in the art without any creative effort are within the scope of the present application.

[0044] Please refer to Figure 1 The direct current power distribution network fault pole selection method provided by the embodiment of the present application comprises:

[0045] Step 101, real-time collection of positive and negative pole coupling electrical quantities of each line in the fault-to-be-selected-pole power distribution network, and decoupling of the positive and negative pole coupling electrical quantities into zero mode and one mode through a pole-mode transformation matrix.

[0046] It should be noted that the real-time collection of the positive and negative pole coupling electrical quantities of each line in the fault-to-be-selected-pole power distribution network includes line positive and negative pole voltage and current signals. Since there is coupling between the positive and negative poles of the bipolar direct current transmission line, the positive and negative pole quantities are decoupled into zero mode and one mode through the following formula (1) pole-mode transformation matrix:

[0047] (1)

[0048] In the formula, u and i are voltage and current; subscripts p and n represent positive pole quantity and negative pole quantity respectively; subscripts 1 and 0 represent one mode and zero mode with the positive pole as the reference respectively.

[0049] It is to be noted that the "zero mode" is one of the symmetrical components of the current or voltage of each phase in a three-phase line, which is equal in size and same in phase in the three-phase line. In the fault pole selection system of the DC distribution network, the zero mode component has an important significance. It can be used as a key electrical characteristic quantity for fault monitoring and judgment. When the DC distribution network fails, the zero mode component will change significantly. Through real-time monitoring and analysis of the zero mode component, the system can quickly detect the occurrence of the fault. The "line mode" (including the first mode and the second mode), the first mode is mainly used to reflect the electrical quantity of the line-to-line fault characteristics. When the DC distribution network has a line-to-line fault, the first mode component will show a specific change rule. For example, under different line-to-line short-circuit fault conditions, the amplitude and phase of the first mode current will have obvious differences. Through in-depth analysis of the first mode component, the occurrence and approximate location of the line-to-line fault can be accurately judged.

[0050] Step 102, compare the voltage of the first mode with the preset criterion, and judge whether the DC distribution network system has a fault according to the comparison result, if yes, execute step 103, otherwise execute step 101.

[0051] It is to be noted that if the measured voltage of the first mode meets the preset criterion (2), it indicates that the system has a fault.

[0052] (2)

[0053] In the formula, is the zero sequence voltage starting setting value.

[0054] When satisfies the criterion (2), it is determined that the system has a fault, and step 103 is entered, otherwise step 101 is returned.

[0055] Step 103, list the boundary condition equations of the fault point of each fault type, and calculate the first mode fault component voltage, the first mode current and the zero mode voltage and current at the fault point of the corresponding fault type based on the boundary condition equations.

[0056] It is to be noted that according to the fault component network of the DC transmission line fault point shown in Figure 2 , the boundary condition equations of the fault point of each fault type are listed, wherein the fault types include: positive pole ground fault, negative pole ground fault, pole-to-pole fault and bipolar ground fault, so as to obtain the zero mode fault component voltage and current when the positive pole ground fault, the negative pole ground fault, the pole-to-pole fault and the bipolar ground fault occur.

[0057] 1) Positive pole ground fault:

[0058] When the positive pole ground fault occurs in the DC transmission line, the fault component network is Figure 2(a) The boundary condition equation at the fault point of the DC transmission line can be listed as:

[0059] (3)

[0060] The boundary condition equation (3) is written as:

[0061] (4)

[0062] where Δu f1 is the one-mode fault component voltage at the fault point; Δu f0 is the zero-mode fault component voltage at the fault point; Δi f1 is the one-mode fault component current at the fault point; and Δi f0 is the zero-mode fault component current at the fault point.

[0063] The reference direction of the current is defined as the bus pointing to the line (i.e., the line pointing to the fault point), and the reference direction of the voltage is defined as the line pointing to the ground. In the reference direction, the fault traveling wave is a backward traveling wave, and the fault component voltage and the current satisfy the relationship in equation (5).

[0064] (5)

[0065] where Z c1 and Z c0 are the one-mode wave impedance and the zero-mode wave impedance of the DC transmission line, respectively.

[0066] Since the zero-mode voltage and current are zero when the DC transmission line is in normal operation, the zero-mode fault component voltage and current at the fault point are equal to the zero-mode voltage and current at the fault point. Hereinafter, Δu f0 and Δi f0 are replaced by u f0 and i f0 , respectively.

[0067] The one-mode fault component voltage and current and the zero-mode voltage and current at the fault point when a positive pole fault occurs in the DC transmission line can be solved by combining equation (4) and equation (5):

[0068] (6)

[0069] (7)

[0070] 2) Negative pole grounding fault:

[0071] Similarly, the fault component network Figure 2 (b) The one-mode fault component voltage and current and the zero-mode voltage and current at the fault point when a negative pole fault occurs in the DC transmission line can be solved.

[0072] (8)

[0073] (9)

[0074] 3) Inter-pole fault:

[0075] When the DC transmission line has an inter-pole fault, the fault component network is Figure 2 (c) The boundary condition equation at the fault point of the DC transmission line can be listed as:

[0076] (10)

[0077] Solving equations (5) and (10) together can obtain the one-mode fault component voltage and current and the zero-mode voltage and current at the fault point of the DC transmission line when the inter-pole fault occurs:

[0078] (11)

[0079] (12)

[0080] 4) Bipolar ground fault:

[0081] When the DC transmission line has a bipolar ground fault, the fault component network is Figure 2 (d) The boundary condition equation at the fault point of the DC transmission line can be listed as:

[0082] (13)

[0083] Solving equations (5) and (13) together can obtain the one-mode fault component voltage and current and the zero-mode voltage and current at the fault point of the DC transmission line when the bipolar ground fault occurs:

[0084] (14)

[0085] (15)

[0086] Step 104, constructing a comparison formula of the zero-mode voltage and the line-mode fault component voltage according to the one-mode fault component voltage, the one-mode current, the zero-mode voltage and the zero-mode current corresponding to each fault type.

[0087] It should be noted that the comparison formula (16) of the zero-mode voltage and the line-mode fault component voltage is obtained from equations (6), (8), (11) and (14), and it is found that the results of the zero-mode-line-mode voltage polarity comparison are different under different scenarios of the positive pole ground fault, the negative pole ground fault, the inter-pole fault and the bipolar ground fault.

[0088] (16)

[0089] Step 105, constructing a fault selection criterion based on the comparison formula, determining a fault selection result according to the fault selection criterion.

[0090] It should be noted that according to formula (16), the fault selection criterion (17) is constructed.

[0091] (17)

[0092] It can be understood that according to (17), when the ratio is greater than zero, it is determined that the fault selection result is a positive pole ground fault, when the ratio is less than zero, it is determined that the fault selection result is a negative pole ground fault, and when the ratio is equal to zero, it is determined that the fault selection result is an inter-pole fault or a bipolar ground fault.

[0093] The DC power distribution network fault pole selection method provided in the embodiment of the application first acquires the positive and negative pole coupling electrical quantities of each line in the low-voltage DC power distribution network in real time, decouples the positive and negative pole coupling electrical quantities into independent modes through a pole-mode transformation matrix, wherein the zero mode reflects the ground fault current path characteristics and is sensitive to single-pole / bipolar ground faults; and the line mode characterizes the inter-pole voltage difference and is sensitive to inter-pole short-circuit faults. The decoupled mode quantity is determined only by the fault physical characteristics and is irrelevant to the system grounding mode (resistance grounding, floating ground, etc.), thereby completely breaking through the dependence of the prior art on a specific grounding mode. Then, whether the system has a fault is judged according to the one-mode, when a fault occurs, the expressions of the zero-mode voltage and the one-mode fault component voltage in the cases of positive pole grounding, negative pole grounding, inter-pole fault and bipolar ground fault are derived, and the polarity of the zero-mode voltage and the one-mode fault component voltage is compared to realize fault pole selection. Since the same criterion is used for single-pole grounding, bipolar short-circuit and bipolar ground fault, there is no need to switch algorithms for different faults, thereby solving the blind area of bipolar fault identification in the prior art. Compared with the prior art, the fault pole selection method of the application realizes fault line selection according to the line voltage and current after a fault, and the method of comparing the zero-mode voltage with the line-mode fault component voltage is simple and easy to implement, has low sampling rate requirement (no MHz-level sampling required for traveling wave protection), is suitable for engineering deployment, realizes high-reliability pole selection only with local electrical quantities, discards the active injection which is susceptible to interference and the integral operation which is sensitive to parameters, and improves the noise immunity and robustness by using the essential characteristics (polarity relationship) of the fault. The prior art has scene limitations due to grounding mode dependence and bipolar fault blind area, and the application realizes global applicability through mathematical decoupling and physical characteristic extraction. Thus, the problem of poor grounding mode adaptability and inability to identify bipolar faults in the prior art is solved.

[0094] The above is a DC power distribution network fault pole selection method provided in the embodiment of the application, and the following is a DC power distribution network fault pole selection system provided in the embodiment of the application. ​​​

[0095] Referring to Figure 3 The direct current power distribution network fault pole selection system provided in the embodiment of the application comprises:

[0096] The decoupling unit 201 is configured to collect positive and negative pole coupling electrical quantities of each line in the power distribution network of the fault to-be-selected pole in real time, and decouple the positive and negative pole coupling electrical quantities into zero mode and one mode through a pole-mode transformation matrix.

[0097] The judgment unit 202 is configured to compare the voltage of the one mode with a preset criterion, and determine whether the direct current power distribution network system has a fault according to the comparison result, and if yes, trigger the first construction unit, and if not, trigger the decoupling unit.

[0098] The first construction unit 203 is configured to list boundary condition equations at fault points of each fault type, and calculate one mode fault component voltages, one mode currents and zero mode voltages and zero mode currents at the fault points of the corresponding fault type based on the boundary condition equations.

[0099] The second construction unit 204 is configured to construct a comparison formula of the zero mode voltage and the line mode fault component voltage according to the one mode fault component voltages, the one mode currents, the zero mode voltages and the zero mode currents corresponding to each fault type.

[0100] The analysis unit 205 is configured to construct a fault selection level criterion based on the comparison formula, and determine a fault selection level result according to the fault selection level criterion.

[0101] Further, the embodiment of the application further provides a direct current power distribution network fault pole selection device, which comprises a processor and a memory:

[0102] The memory is configured to store program code and transmit the program code to the processor.

[0103] The processor is configured to execute the steps of the direct current power distribution network fault pole selection method according to the instructions in the program code.

[0104] Further, the embodiment of the application further provides a computer readable storage medium, which is configured to store program code, and the program code is configured to execute the direct current power distribution network fault pole selection method described in the above method embodiment.

[0105] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the system, device and unit described above can refer to the corresponding process in the foregoing method embodiment, which will not be described here.

[0106] In several embodiments provided by the present application, it should be understood that the disclosed system, device and method can be implemented in other manners. For example, the division of the units is only a logical function division, and there can be another division manner for the actual implementation, for example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections between different units, can be indirect couplings or communication connections through some interfaces, devices or units, and can be in electrical, mechanical or other forms.

[0107] The units described as separated components can or can not be physically separated, and the components displayed as units can or can not be physical units, i.e., can be located in one place, or can be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purposes of the embodiments of the present application.

[0108] In addition, each functional unit in the various embodiments of the present application can be integrated in a processing unit, or each unit can exist physically as a separate unit, or two or more units can be integrated in one unit. The integrated unit can be implemented in the form of hardware, or in the form of a software functional unit.

[0109] 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 such an understanding, the technical solutions of the present application essentially or substantially, or all or part of the technical solutions, can be embodied in the form of a software product. The computer software product is stored in a storage medium, and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods in the various embodiments of the present application. The foregoing storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), magnetic disk or optical disk, and various media that can store program codes.

[0110] The above embodiments are only used to illustrate the technical solutions of the present application, rather than limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements for some technical features; and these modifications or replacements do not make the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for faulted pole selection in a direct current distribution network, characterized by, Comprising: S1, real-time acquisition of each line of the positive and negative coupling electrical quantity of the power distribution network of the fault candidate pole, and decoupling the positive and negative coupling electrical quantity into zero mode and one mode through the pole-mode transformation matrix; S2, comparing the voltage of the one mode with the preset criterion, and judging whether the DC power distribution network system has a fault according to the comparison result, if yes, executing step S3, otherwise executing step S1; S3, writing boundary condition equations of fault points of each fault type, and calculating one mode fault component voltage, one mode current and zero mode voltage and zero mode current at the fault points of the corresponding fault type based on the boundary condition equations; S4, constructing a comparison formula of zero mode voltage and line mode fault component voltage according to the one mode fault component voltage, the one mode current and the zero mode voltage and the zero mode current corresponding to each fault type; S5, constructing a fault selection criterion based on the comparison formula, and determining a fault selection result according to the fault selection criterion; The fault type includes: positive pole grounding fault, negative pole grounding fault, pole-to-pole fault and bipolar grounding fault; The expression of the comparison formula is: ； wherein is the zero-mode voltage, is a one-mode fault component voltage at the fault point, is the zero-mode current, and are the one-mode wave impedance and the zero-mode wave impedance of the DC transmission line, respectively, is a one-mode fault component current at the fault point generated by the fault, is the fault point voltage, is the transition resistance.

2. The DC distribution grid faulted pole selection method of claim 1, wherein, The expression of the fault selection criterion is: ； wherein is the zero-mode voltage, is the one-mode fault component voltage at the fault point.

3. A direct current distribution network faulted pole selection system, characterized by, Comprising: The decoupling unit is configured to real-time acquisition of each line of the positive and negative coupling electrical quantity of the power distribution network of the fault candidate pole, and decoupling the positive and negative coupling electrical quantity into zero mode and one mode through the pole-mode transformation matrix; The judgment unit is configured to compare the voltage of the one mode with the preset criterion, and judge whether the DC power distribution network system has a fault according to the comparison result, if yes, trigger the first construction unit, otherwise trigger the decoupling unit; The first construction unit is configured to write boundary condition equations of fault points of each fault type, and calculate one mode fault component voltage, one mode current and zero mode voltage and zero mode current at the fault points of the corresponding fault type based on the boundary condition equations; The second construction unit is configured to construct a comparison formula of zero mode voltage and line mode fault component voltage according to the one mode fault component voltage, the one mode current and the zero mode voltage and the zero mode current corresponding to each fault type; The analysis unit is configured to construct a fault selection criterion based on the comparison formula, and determine a fault selection result according to the fault selection criterion; The fault type includes: positive pole grounding fault, negative pole grounding fault, pole-to-pole fault and bipolar grounding fault; The expression of the comparison formula is: ； wherein is the zero-mode voltage, is a one-mode fault component voltage at the fault point, is the zero-mode current, and are the one-mode wave impedance and the zero-mode wave impedance of the DC transmission line, respectively, is a one-mode fault component current at the fault point generated by the fault, is the fault point voltage, is the transition resistance.

4. The DC distribution grid faulted pole selection system of claim 3, wherein, The expression of the fault selection criterion is: ； wherein is the zero-mode voltage, is the one-mode fault component voltage at the fault point.

5. A DC power distribution network faulted pole selection device, characterized by, The device comprises a processor and a memory: The memory is configured to store program code and transmit the program code to the processor; The processor is configured to execute the DC power distribution network fault pole selection method according to the instructions in the program code.

6. A computer-readable storage medium, characterized in that, The computer readable storage medium is configured to store program code, and the program code is configured to execute the DC power distribution network fault pole selection method.

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