CN-122026285-A - Active power distribution network single-phase earth fault protection method and system based on current amplitude-phase multi-evidence fusion

CN122026285ACN 122026285 ACN122026285 ACN 122026285ACN-122026285-A

Abstract

The invention provides a single-phase earth fault protection method and a system for an active power distribution network based on current amplitude-phase multi-evidence fusion, wherein after a single-phase earth fault is detected by the method, high-frequency characteristic current frequency is determined in a self-adaptive manner according to resonance avoidance requirements and phase difference stability constraints, and is injected into the power distribution network by a distributed power supply connected with a bus; collecting the amplitude and phase of the high-frequency current at the outlet of each feeder line, and constructing three-dimensional fault evidence of phase lag universe, amplitude relative duty ratio and current time sequence stability; the invention improves the accuracy, transition resistance and robustness of fault line selection under complex working conditions by a multidimensional evidence complementation and conflict processing mechanism, is realized by depending on the existing distributed power supply, does not need additional equipment, reduces the transformation cost, and is suitable for a power distribution network containing a high-permeability distributed power supply.

Inventors

Diao Yanbo

Assignees

重庆城市管理职业学院

Dates

Publication Date: 20260512
Application Date: 20260213

Claims (10)

1. The active power distribution network single-phase earth fault protection method based on current amplitude-phase multi-evidence fusion is characterized by comprising the following steps of: s101, when a single-phase earth fault of the power distribution network is detected, calculating a frequency reference value of the injection current according to the resonance avoidance requirement and the phase angle difference stability constraint of the power distribution network, and injecting high-frequency characteristic current into the power distribution network by a distributed power supply connected with a bus; s102, collecting the amplitude and the phase of high-frequency characteristic current at the outlet of each feeder line; s103, constructing phase lag global evidence, amplitude relative duty ratio evidence and current time sequence stable evidence of single-phase earth faults of the power distribution network according to the acquired feeder high-frequency characteristic current amplitude and phase; s104, calculating membership degree and distribution weight of phase lag universe evidence, amplitude relative duty ratio evidence and current time sequence stable evidence; S105, judging whether the amplitude evidence conflicts with the phase evidence, if so, attenuating the weight of the amplitude evidence, otherwise, executing S106; S106, calculating comprehensive fault comprehensive confidence coefficient of each feeder line, taking the feeder line with the largest comprehensive confidence coefficient as a fault feeder line, and sending out an alarm or tripping signal.
2. The method for single-phase earth fault protection of an active power distribution network based on current amplitude-phase multi-evidence fusion according to claim 1, wherein calculating the frequency reference value of the injected current comprises: ; ; ; Wherein, the To minimum of the injection current frequency reference values, Maximum value of the injection current frequency reference value; is the total number of distributed power sources on the mth feeder line; Equivalent inductance of the kth distributed power supply on the mth feeder line; the equivalent capacitance of the kth distributed power supply on the mth feeder line; The capacitance to ground of the mth feeder line; the combined resonance center frequency of the power distribution network; Is the coefficient of parameter fluctuation.
3. The single-phase earth fault protection method for the active power distribution network based on current amplitude-phase multi-evidence fusion is characterized in that a high-frequency detection device is used for collecting high-frequency characteristic current amplitude values, frequency and phases of all feeder lines, and the sampling frequency of the high-frequency detection device is not lower than 20 times of the characteristic frequency.
4. The active power distribution network single-phase earth fault protection method based on current amplitude-phase multi-evidence fusion according to claim 1, wherein constructing phase lag global evidence, amplitude relative duty ratio evidence and current time sequence stable evidence of the power distribution network single-phase earth fault comprises: the method comprises the following steps of constructing phase lag universe evidence of single-phase earth faults of the power distribution network: ; the amplitude relative duty ratio evidence of the single-phase earth fault of the power distribution network is constructed as follows: ; The current time sequence stable evidence of the single-phase earth fault of the power distribution network is constructed as follows: ; Wherein, the As the total number of feed lines, 、 The high-frequency characteristic currents of the feeder i and the feeder j are respectively; the phase difference of the high-frequency characteristic currents of the feeder j and the feeder i is obtained; The standard deviation of the phase difference of the high-frequency characteristic currents of the feeder line i and the feeder line j is obtained; 、 Respectively is And And the high-frequency characteristic current of the feeder line i is collected at the moment.
5. The method for protecting the single-phase earth fault of the active power distribution network based on current amplitude-phase multi-evidence fusion according to claim 1, wherein the membership degree of the phase lag global evidence is calculated as follows: ; Wherein, the An inflection point of a global evidence membership function for phase lag; is the phase lag global evidence of single-phase earth faults of the power distribution network.
6. The method for protecting the single-phase earth fault of the active power distribution network based on current amplitude-phase multi-evidence fusion according to claim 1, wherein the membership degree of the calculated amplitude relative duty ratio evidence is as follows: ; Wherein, the Inflection points of the membership function of the amplitude relative duty ratio evidence; The method comprises the steps that when a fault feeder is connected with a non-distributed power supply, the maximum value of the high-frequency characteristic current amplitude ratio of the fault feeder and the non-fault feeder is connected with the non-distributed power supply; the method comprises the steps that the maximum value of the amplitude ratio of high-frequency characteristic currents of a fault feeder line and a non-fault feeder line with distributed power supply access is obtained when the fault feeder line is not connected with the distributed power supply; when a distributed power supply is connected to the fault feeder, the maximum value of the amplitude ratio of the high-frequency characteristic current flowing through the fault feeder and the non-fault feeder without the distributed power supply is connected; When the distributed power supply is connected to the fault feeder, the amplitude ratio of the high-frequency characteristic current flowing through the fault feeder and the non-fault feeder connected to the distributed power supply is the maximum value.
7. The active power distribution network single-phase earth fault protection method based on current amplitude-phase multi-evidence fusion according to claim 1, wherein the membership degree of phase time sequence stable evidence is calculated: ; Wherein, the Is the theoretical maximum noise phase of the sampling device; is the minimum phase ripple of the non-faulty feeder due to resonance.
8. The method for protecting single-phase earth fault of active power distribution network based on current amplitude-phase multi-evidence fusion according to claim 1, wherein the calculation and distribution of weight is to determine the weight of fault evidence according to the effective working condition of amplitude-phase characteristics, specifically, the phase lag is used for all working conditions, the core evidence is the core evidence, the weight is the maximum, and the weight is taken as The phase time sequence stable evidence is used for filtering sampling interference and is taken as auxiliary evidence, and the weight of the auxiliary evidence is lower than that of the core evidence The amplitude relative duty ratio evidence is effective under the condition of smaller transition resistance, is taken as secondary auxiliary core evidence 。
9. The active power distribution network single-phase earth fault protection method based on current amplitude-phase multi-evidence fusion according to claim 1, wherein the comprehensive fault comprehensive confidence of each feeder line is calculated as follows: ; Wherein, the As a weight for the phase lag, As a membership of the phase-lag global evidence, As the weight of the evidence of phase timing stabilization, For membership of amplitude versus duty cycle evidence, For weights where the amplitude versus duty cycle evidence is valid only at small transition resistances, The membership degree of the evidence for phase timing stabilization.
10. An active power distribution network single-phase earth fault protection system based on current amplitude-phase multi-evidence fusion is used for executing the active power distribution network single-phase earth fault protection method based on current amplitude-phase multi-evidence fusion according to any of claims 1-9, and is characterized by comprising a high-frequency current injection module, a high-frequency electric quantity acquisition module, a fault evidence construction module and a multi-evidence fusion decision module; The high-frequency current injection module is used for self-adaptive injection of high-frequency characteristic current and comprises a frequency calculation unit, and a frequency reference value is output based on the resonance characteristic and the phase difference stability of the power distribution network; The high-frequency electric quantity acquisition module is used for executing feeder high-frequency electric quantity acquisition and comprises a feeder current acquisition unit, wherein an acquisition object is the amplitude and the phase of high-frequency current at a feeder outlet; the fault evidence construction module is used for constructing fault evidence and comprises a phase lag calculation unit, an amplitude duty ratio calculation unit and a time sequence stability calculation unit; the multi-evidence fusion decision module is used for executing multi-evidence fusion decision and comprises a membership degree calculation unit, a weight distribution unit, a fusion calculation unit and a fault feeder line identification unit.

Description

Active power distribution network single-phase earth fault protection method and system based on current amplitude-phase multi-evidence fusion Technical Field The invention belongs to the technical field of power systems, and particularly relates to a single-phase earth fault protection method and system for an active power distribution network based on current amplitude-phase multi-evidence fusion. Background Under the drive of global energy crisis and environmental problems, renewable energy sources such as solar energy, wind energy and the like are widely connected into a power distribution network by means of a distributed power supply, and the power distribution network is pushed to be converted into a high-permeability distributed power supply connection mode. However, the distributed power supply has the characteristics of limited short-circuit current, controlled fault behaviors, coupling of output characteristics and the like, so that the fault process of the power distribution network presents obvious polymorphism, the line selection accuracy of the traditional single-phase earth fault line selection methods such as a steady-state zero-sequence current amplitude-phase comparison method, a transient traveling wave method and the like is greatly reduced, misoperation and refusal are easy to occur, and the equipment and personal safety and the stable operation of a power grid are seriously threatened. To solve the above-mentioned problems, the prior art proposes an injection protection method for reinforcing fault characteristics by injecting characteristic signals into a power distribution network. The existing injection type protection method has the defects that firstly, the fault criterion depends on the amplitude or phase characteristics of characteristic signals, and under the high-resistance fault and multi-distributed power supply access scene, misjudgment is easily caused by attenuation or interference of the characteristic signals; secondly, an effective evidence conflict processing mechanism is not established, and when the amplitude of the characteristic signal contradicts with the phase characteristic, reasonable decision logic is lacked; thirdly, the amplitude of the injection current does not fully consider the low voltage ride through requirement of the distributed power supply, the safety constraint of equipment and the fault detection sensitivity, so that the detection failure or the equipment overload risk is caused under the high-resistance fault; therefore, a method and a device for self-adaptive protection with conflict processing capability are needed to cooperatively optimize the parameters of the injected signals, fuse multidimensional fault evidence, and improve the accuracy and reliability of single-phase grounding fault line selection of a power distribution network with a high-permeability distributed power supply. Disclosure of Invention The invention provides the active power distribution network single-phase grounding fault protection method and device based on current amplitude-phase multi-evidence fusion, optimizes the frequency and amplitude parameters of the injected current, gives consideration to resonance avoidance, phase difference stability, low voltage ride through requirements of a distributed power supply and equipment safety constraint, builds multi-dimensional fault evidence, strengthens the characteristic difference of fault feeder lines and non-fault feeder lines, builds an evidence conflict processing mechanism and a weight distribution strategy, improves decision reliability under complex working conditions, and realizes accurate line selection of power distribution network single-phase grounding faults under different fault positions and different transition resistance working conditions, thereby having good adaptability and transition resistance capability. An active power distribution network single-phase earth fault protection method based on current amplitude-phase multi-evidence fusion comprises the following steps: s101, when a single-phase earth fault of the power distribution network is detected, calculating a frequency reference value of the injection current according to the resonance avoidance requirement and the phase angle difference stability constraint of the power distribution network, and injecting high-frequency characteristic current into the power distribution network by a distributed power supply connected with a bus; s102, collecting the amplitude and the phase of high-frequency characteristic current at the outlet of each feeder line; s103, constructing phase lag global evidence, amplitude relative duty ratio evidence and current time sequence stable evidence of single-phase earth faults of the power distribution network according to the acquired feeder high-frequency characteristic current amplitude and phase; s104, calculating membership degree and distribution weight of phase lag universe evidence, amplitude relative duty ra