A small current ground fault active arc extinguishing fault point arc extinguishing detection method

Abstract

The present application relates to a kind of small current grounding fault active arc extinguishing when fault point arc extinguishing detection method, comprising the following steps: after detecting that small current grounding fault occurs, gradually increase the amplitude of neutral point voltage by active inverter control, make the voltage of fault phase gradually reduce;During the process of gradually increasing the amplitude of neutral point voltage, the injection current of active inverter and the corresponding bus zero sequence voltage at different time are measured and recorded in real time, the change value of injection current and bus zero sequence voltage are obtained by calculating the change of adjacent two different time measurement values, and the power frequency component is extracted by the change value of injection current and bus zero sequence voltage;Based on power frequency component, the admittance and impedance angle of system are calculated;According to impedance angle and the preset impedance angle threshold value, whether the fault point is arc extinguished is judged.

Description

TECHNICAL FIELD

[0001] The application relates to a detection method for arc extinction at a fault point during active arc extinction of a small-current grounding fault, and belongs to the technical field of small-current grounding fault detection. BACKGROUND

[0002] When a single-phase grounding fault occurs in a distribution network, reducing the current at the fault point can promote arc extinction at the fault point, reduce fault damage, and avoid accident expansion. An arc suppression coil is a common arc suppression device in the distribution network, but it can only compensate for the reactive component of the grounding fault current and cannot compensate for the active and harmonic components, so it cannot ensure reliable arc extinction at the grounding point. Active arc extinction technology using an active inverter as an active power injection source can realize full compensation of the grounding fault current and reliable arc extinction at the grounding point.

[0003] How to accurately determine whether arc extinction occurs at the fault point can provide a basis for setting the subsequent compensation state of the active inverter and avoid the occurrence of abnormal compensation of the voltage arc extinction method. SUMMARY

[0004] In order to solve the problems in the prior art, the application provides a detection method for arc extinction at a fault point during active arc extinction of a small-current grounding fault.

[0005] The technical scheme of the application is as follows:

[0006] On the one hand, the application provides a detection method for arc extinction at a fault point during active arc extinction of a small-current grounding fault, which comprises the following steps:

[0007] After detecting the occurrence of a small-current grounding fault, the amplitude of the neutral point voltage is gradually increased by an active inverter control, so that the voltage of the fault phase is gradually reduced;

[0008] During the process of gradually increasing the amplitude of the neutral point voltage, the injection current of the active inverter and the corresponding bus zero sequence voltage at different times are measured and recorded in real time, the change values of the injection current and the bus zero sequence voltage are calculated by using the measurement values at adjacent two different times, and the fundamental frequency components are extracted by using the change values of the injection current and the bus zero sequence voltage;

[0009] The system admittance and impedance angle are calculated based on the fundamental frequency components;

[0010] Whether the fault point is extinguished is determined according to the impedance angle and a preset impedance angle threshold.

[0011] As a preferred embodiment, during the process of gradually increasing the amplitude of the neutral point voltage by the active inverter control, different step coefficients k are set, 0 < k < 1;

[0012] The control target of the active inverter under different step coefficients k is set as wherein bus zero sequence voltage, fault phase power supply voltage;

[0013] gradually increase the step coefficient k, and when it is determined that the arc at the fault point is extinguished or k = 1, the step coefficient is no longer increased.

[0014] As a preferred embodiment, the method of extracting the power frequency component through the injected current change value and the bus zero sequence voltage change value is specifically:

[0015] Based on the injected current change value and the bus zero sequence voltage change value, the power frequency components of the two are calculated respectively by using Fourier transform and wherein is the injected current power frequency component, is the bus zero sequence voltage power frequency component;

[0016] The formula for calculating the system admittance and the impedance angle based on the power frequency component is specifically:

[0017]

[0018] wherein, is the system admittance, is the impedance angle, is the real part of is the imaginary part of

[0019] In another aspect, the present application also provides a small current grounding fault active arc extinguishing fault point arc extinguishing detection system, comprising:

[0020] An arc extinguishing control module is configured to, after detecting the occurrence of a small current grounding fault, gradually increase the amplitude of the neutral point voltage through an active inverter to gradually reduce the fault phase voltage;

[0021] A compensation module is configured to, during the process of gradually increasing the amplitude of the neutral point voltage, measure and record the injected current of the active inverter and the corresponding bus zero sequence voltage at different time points in real time, calculate the change amount of the injected current and the bus zero sequence voltage by using the measurement values at adjacent two different time points, and extract the power frequency component through the injected current change value and the bus zero sequence voltage change value;

[0022] A parameter calculation module is configured to calculate the system admittance and the impedance angle based on the power frequency component;

[0023] An arc extinguishing detection module is configured to determine whether the arc at the fault point is extinguished according to the impedance angle and a preset impedance angle threshold.

[0024] ​​As a preferred embodiment, in the compensation module, different step coefficients k are set in the process of gradually increasing the neutral point voltage amplitude and gradually reducing the fault phase voltage through active inverter control, and 0 < k < 1.

[0025] The control target of the active inverter under different step coefficients k is set as Wherein, is the bus zero sequence voltage, is the fault phase power supply voltage;

[0026] The step coefficient k is gradually increased, and the step coefficient is no longer increased after the arc extinguishing point is determined or k = 1.

[0027] As a preferred embodiment, the method for extracting the power frequency component through the injected current change value and the bus zero sequence voltage change value in the parameter calculation module is specifically as follows:

[0028] Based on the injected current change value and the bus zero sequence voltage change value, the power frequency components of the two are calculated by using Fourier transform And Wherein, is the injected current power frequency component, is the bus zero sequence voltage power frequency component;

[0029] The formula for calculating the admittance and impedance angle based on the power frequency component is specifically as follows:

[0030]

[0031] Wherein, is the system admittance, is the impedance angle, is the real part of is the imaginary part of

[0032] In another aspect, the application also provides an electronic device, which comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the small current grounding fault active arc extinguishing fault point arc extinguishing detection method according to any one of the embodiments of the application when executing the program.

[0033] In another aspect, the application also provides a computer readable storage medium, which stores a computer program, and the program is executable on the processor to implement the small current grounding fault active arc extinguishing fault point arc extinguishing detection method according to any one of the embodiments of the application.

[0034] The application has the following beneficial effects:

[0035] ​​The application discloses a small-current grounding fault active arc extinguishing fault point arc extinguishing detection method. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 A system structure schematic diagram of small-current grounding fault active arc extinguishing is provided for the embodiment of the application.

[0037] Figure 2 A method flow schematic diagram is provided for the embodiment of the application.

[0038] Figure 3 A simulation data schematic diagram is provided for the embodiment of the application. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the application will be apparently and completely described below with reference to the drawings in the embodiments of the application. Apparently, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without any creative work under the premise that the embodiments in the application are within the protection scope of the application.

[0040] It should be understood that the step numbers used herein are only for the convenience of description, and are not limited to the execution sequence of the steps.

[0041] It should be understood that the terms used in the specification of the application are only for the purpose of describing specific embodiments and are not intended to limit the application. As used in the specification and the appended claims of the application, the singular forms "a", "an" and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0042] The terms "comprise" and "include" indicate the presence of described features, whole, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, whole, steps, operations, elements, components and / or sets thereof.

[0043] The term "and / or" means any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0044] Embodiment one:

[0045] Referring to Figure 1 , Figure 1 A system structure diagram of small-current grounding fault active arc extinguishing, three-phase voltage of the system The three-phase voltage is Zero-sequence voltage The neutral point zero-sequence impedance of the system is Z L The current during a ground fault is Z in resonant grounding system L The zero-sequence impedance of the arc suppression coil. For the compensation current of the arc suppression coil, Z is the current in an ungrounded system. L Approximately ∞ The compensation current of the active inverter is 0; The three-phase ground capacitance of the system is C A C B C C The three-phase resistance to ground is R. A R B R C In practical applications, R can be ignored. A R B R C Impact on calculation results; grounding point F transition resistance R f The fault current is

[0046] The controller measures system phase voltage, zero-sequence voltage, active inverter injection current, and arc suppression coil compensation current (for resonant grounding systems) in real time to detect grounding faults and control the switching and compensation of the active inverter. The active inverter converts the DC signal into a single-phase power frequency AC current with controlled amplitude and phase angle, which is then injected into the system neutral point via an isolation step-up transformer to control the faulty phase voltage to 0.

[0047] See Figure 2 This embodiment provides a method for detecting arc extinction at the fault point during active arc suppression of a low-current grounding fault, specifically including the following steps:

[0048] S100, controller real-time measurement system for three-phase voltage and zero-sequence voltage The zero-sequence voltage amplitude was detected to exceed the set threshold. ( It is generally set to 15% of the phase power supply voltage. When a ground fault is detected, the neutral point voltage amplitude is gradually increased by controlling the active inverter to gradually reduce the fault phase voltage to 0.

[0049] S200. Compare the phase voltage amplitudes after the fault occurs to determine the faulty phase X (one of phases A, B, and C); set the initial value k0 of the step coefficient k (based on the zero-sequence voltage of the system when the active inverter is not engaged); engage the active inverter for compensation, and set the initial target for the zero-sequence voltage as follows: Then gradually increase the value of k, 0 < k < 1; in the process of controlling the gradual increase of the neutral point voltage amplitude, the output current variation of the active inverter at different k values is measured and calculated in real time And the variation of the output voltage The power frequency components of the two are calculated by Fourier transform And

[0050] S300, calculate the system admittance Y based on the power frequency component k And the impedance angle According to the formula:

[0051]

[0052] Wherein, The real part of The imaginary part of The imaginary part of

[0053] S400, according to the impedance angle And the preset impedance angle threshold ( can be set, generally 70°) to determine whether the fault point is arc extinguished, when The fault point is extinguished, and the step coefficient k of the active inverter in the next period is maintained unchanged; when The fault point is not extinguished, the step coefficient k of the active inverter continues to increase, and steps S200 and S300 are repeated.

[0054] S500, when the step coefficient is no longer increased and the output of the active inverter is no longer changed when the fault point is extinguished or the step coefficient k = 1 is detected during the output of the active inverter.

[0055] As shown in Figure 3 As shown in Figure 3 The change graph of the output voltage (zero sequence voltage), output current and fault point current of the active inverter is shown when a single-phase ground fault occurs in the static mode simulation system using the method of the embodiment. It can be seen that the method based on the embodiment can accurately determine the arc extinguishing point.

[0056] Example two:

[0057] The embodiment provides a small current ground fault active arc extinguishing fault point arc extinguishing detection system, comprising:

[0058] The arc extinguishing control module is used for detecting the occurrence of the small current ground fault, gradually increasing the amplitude of the neutral point voltage through the active inverter, and gradually reducing the fault phase voltage; the module is used for realizing the function of step S100 in the embodiment one, and details are not repeated here;

[0059] ​The compensation module is configured to measure and record the injection current of the active inverter and the corresponding bus zero sequence voltage at different time points in real time during the process of gradually increasing the neutral point voltage amplitude, calculate the injection current change value and the bus zero sequence voltage change value by using the change of the injection current and the bus zero sequence voltage measured at adjacent two different time points, and extract the power frequency component by using the injection current change value and the bus zero sequence voltage change value. The compensation module is configured to realize the function of step S200 in the first embodiment, and thus will not be described here again.

[0060] The parameter calculation module is configured to calculate the system admittance and the impedance angle based on the power frequency component. The parameter calculation module is configured to realize the function of step S300 in the first embodiment, and thus will not be described here again.

[0061] The arc extinguishing detection module is configured to determine whether the fault point is arc extinguished according to the impedance angle and the preset impedance angle threshold. The arc extinguishing detection module is configured to realize the function of step S400 in the first embodiment, and thus will not be described here again.

[0062] As a preferred embodiment of the present embodiment, in the compensation module, different step coefficients k are set during the process of gradually increasing the neutral point voltage amplitude by using the active inverter to gradually reduce the fault phase voltage, and 0 < k ≤ 1.

[0063] The control target of the active inverter under different step coefficients k is set as wherein is the bus zero sequence voltage, is the fault phase power supply voltage.

[0064] The step coefficient k is gradually increased, and the step coefficient is not increased after the fault point is determined to be arc extinguished or k = 1.

[0065] As a preferred embodiment of the present embodiment, the method for extracting the power frequency component by using the injection current change value and the bus zero sequence voltage change value in the parameter calculation module is specifically as follows:

[0066] Based on the injection current change value and the bus zero sequence voltage change value, the power frequency components of the injection current and the bus zero sequence voltage are calculated by using Fourier transform and wherein is the injection current power frequency component, is the bus zero sequence voltage power frequency component.

[0067] The formula for calculating the system admittance and the impedance angle based on the power frequency component is specifically as follows:

[0068]

[0069] wherein, is the system admittance, is the impedance angle, is the real part of . Imaginary part of

[0070] Embodiment three

[0071] The embodiment provides an electronic device, including a memory, a processor and a computer program stored in the memory and executable on the processor, and the processor implements the arc extinguishing detection method for fault point when small current grounding fault is actively arc extinguished according to any embodiment of the present application.

[0072] Embodiment four

[0073] The embodiment provides a computer readable storage medium, and a computer program is stored in the computer readable storage medium, and the computer program is executable on the processor, and the processor implements the arc extinguishing detection method for fault point when small current grounding fault is actively arc extinguished according to any embodiment of the present application.

[0074] In the embodiments of the present application, "at least one" means one or more, and "multiple" means two or more. The "and / or" describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B, which can represent the cases of A alone, A and B together, and B alone. Wherein A and B can be singular or plural. The character " / " generally represents that the associated objects before and after it are in an "or" relationship. "At least one of the following" and the like means any combination of these items, including any combination of single or multiple items. For example, at least one of a, b and c can represent: a, b, c, a and b, a and c, b and c or a and b and c, wherein a, b and c can be single or multiple.

[0075] Those skilled in the art can realize that each unit and algorithm step described in the embodiments disclosed in the present application can be realized by electronic hardware, computer software and combination of electronic hardware and computer software. Whether the functions are realized by hardware or software depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to realize the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0076] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the above-mentioned system, device and unit can refer to the corresponding process in the foregoing method embodiments, which will not be described here.

[0077] ​In several embodiments provided in the present application, any function, if realized in the form of a software function unit and sold or used as an independent product, can be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present application or the parts of the technical solutions that essentially contribute to the prior art or the parts 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 a plurality of 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 method described in the embodiments of the present application. The aforementioned storage medium includes a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, and various media that can store program codes.

[0078] The above description is only some embodiments of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation, or direct or indirect application in other related technical fields, based on the content of the specification and drawings of the present application, are also included in the patent protection scope of the present application.

Claims

1. A method for detecting arc extinction at the fault point during active arc suppression of a low-current grounding fault, characterized in that, Includes the following steps: After a small current ground fault is detected, the neutral point voltage amplitude is gradually increased by controlling the active inverter, so that the fault phase voltage gradually decreases. During the process of gradually increasing the amplitude of the control neutral point voltage, the injection current of the active inverter and the corresponding bus zero-sequence voltage are measured and recorded in real time at different times. The changes in the two are calculated using the measurement values ​​at two adjacent different times to obtain the change value of the injection current and the change value of the bus zero-sequence voltage. The power frequency component is extracted through the change value of the injection current and the change value of the bus zero-sequence voltage. Calculation of system admittance and impedance angle based on power frequency components; The fault point is determined to be extinguished based on the impedance angle and the preset impedance angle threshold.

2. The method for detecting arc extinction at the fault point during active arc suppression of a low-current grounding fault according to claim 1, characterized in that: In the process of gradually increasing the amplitude of the neutral point voltage through the active inverter to gradually decrease the voltage of the fault phase, different step coefficients k are set, where 0 < k ≤ 1. The control target setting of the active inverter under different timing coefficients k is as follows in This is the zero-sequence voltage of the bus. The power supply voltage of the faulty phase; The step coefficient k is gradually increased. Once the fault point is determined to be extinguished or k = 1, the step coefficient is no longer increased.

3. The method for detecting arc extinction at the fault point during active arc suppression of a low-current grounding fault according to claim 1, characterized in that, The method for extracting the power frequency component by analyzing the changes in injected current and the changes in bus zero-sequence voltage is as follows: Based on the changes in injected current and bus zero-sequence voltage, the power frequency components of both are calculated using Fourier transform. and in To inject the power frequency component of the current, The zero-sequence voltage of the bus is the power frequency component; The specific formula for calculating the system admittance and impedance angle based on the power frequency component is as follows: in, For system admittance, It is the impedance angle. for The real part, for The imaginary part.

4. A fault point arc extinction detection system for active arc suppression of low-current grounding faults, characterized in that, include: The arc suppression control module is used to detect a small current ground fault and then gradually increase the neutral point voltage amplitude through the active inverter, so that the fault phase voltage gradually decreases. The compensation module is used to measure and record the injection current and corresponding bus zero-sequence voltage of the active inverter in real time during the process of gradually increasing the amplitude of the control neutral point voltage. It calculates the change in the injection current and the change in the bus zero-sequence voltage by using the measurement values ​​at two adjacent different times, and extracts the power frequency component through the change in the injection current and the change in the bus zero-sequence voltage. The parameter calculation module calculates the system admittance and impedance angle based on the power frequency component. The arc extinction detection module is used to determine whether the fault point has extinguished the arc based on the impedance angle and the preset impedance angle threshold.

5. The fault point arc extinction detection system for active arc suppression of low-current grounding faults according to claim 4, characterized in that: In the compensation module, different step coefficients k are set, where 0 < k ≤ 1, during the process of gradually increasing the neutral point voltage amplitude by controlling the active inverter to gradually decrease the fault phase voltage. The control target setting of the active inverter under different timing coefficients k is as follows in This is the zero-sequence voltage of the bus. The power supply voltage of the faulty phase; The step coefficient k is gradually increased. Once the fault point is determined to be extinguished or k = 1, the step coefficient is no longer increased.

6. The fault point arc extinction detection system for active arc suppression of low-current grounding faults according to claim 4, characterized in that, The parameter calculation module extracts the power frequency component using the injected current change value and the bus zero-sequence voltage change value as follows: Based on the changes in injected current and bus zero-sequence voltage, the power frequency components of both are calculated using Fourier transform. and in To inject the power frequency component of the current, The zero-sequence voltage of the bus is the power frequency component; The specific formula for calculating the system admittance and impedance angle based on the power frequency component is as follows: in, For system admittance, It is the impedance angle. for The real part, for The imaginary part.

7. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the fault point arc extinction detection method as described in any one of claims 1 to 3 for active arc extinguishing of low-current grounding faults.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by the processor, the program implements the fault point arc extinction detection method as described in any one of claims 1 to 3 for active arc extinguishing of low-current grounding faults.

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