The invention relates to a distribution network ground fault arc suppression method based on three-phase cascade H bridge converters. The three-phase cascade H bridge converters are adopted to replace arc suppression coils and mounted between phase lines and the ground, and power is supplied to capacitors on the direct current side of the converters by using phase voltages, so that boosting transformers and grounding transformers are saved, and the problem of source taking difficulty on the direct current side of the converters is solved. The converters inject current to a distribution network in a phase splitting mode to compensate the total current of a ground fault to be zero or to inhibit the phase voltage of the fault to be zero, so that the arc is automatically extinguished; and the reference compensation current is calculated by using real-time measured zero sequence voltage, so that the fault phase identification link is saved. The operation is simplified by using the voltage arc suppression method of controlling the zero sequence voltage to adjust the injected compensation current. In view of the influence of circuit parameters and load current on the arc suppression effect and the deduced relation between the ground fault residual current after the voltage arc suppression method is applied and the zero sequence voltage after the fault, an adaptive arc suppression method is put forward by using the zero sequence voltage as a voltage and current arc suppression method.

Distribution network ground fault arc suppression method based on three-phase cascade H bridge converters

The invention discloses a ground fault fully compensated controllable voltage source output voltage computing method, comprising the steps of obtaining circuit ground capacitance, leakage resistance,fault ground resistance, arc suppression coil inductance, resistance and controllable voltage source internal resistance when a ground fault occurs; computing parallel impedance of a circuit ground parameter and a compensation inductance parameter according to the arc suppression coil inductance, the resistance, the leakage resistance and the circuit ground capacitance; and computing a controllable voltage source output voltage according to the fault ground resistance, the controllable voltage source internal resistance and the parallel impedance of the circuit ground parameter and the compensation inductance parameter According to the method, in a voltage source access mode, the state problem that an arc suppression coil inductance parameter and the circuit ground capacitance approximateto power frequency resonance does not need to be taken into consideration; control is relatively easy; a fault current can be effectively compensated; and arc quenching is carried out on a fault point According to the method, phase and amplitude of the output voltage are obtained through computing, the current at the fault point is quenched through control over the phase and amplitude of a controllable voltage source, and safe and stable operation of a power grid is ensured

Ground fault fully compensated controllable voltage source output voltage computing method

The invention discloses a train bogie bearing service process monitoring and fault diagnosis system and method. The system comprises vibration sensors, a collecting board card, an AD chip, a digital signal processing board card and a diagnosis service mainframe, the digital signal processing board card is of a double-processor architecture with a DSP (digital signal processor) and an FPGA (field programmable gate array), the vibration sensors are arranged on an axle end cap of a train, and each bogie is provided with four vibration sensors. The vibration sensors collect vibration signals of a bogie bearing, analog signals are acquired through the collecting board card integrating amplifying and filtering functions, digital signals are acquired after the AD chip samples the analog signals and then input into the FPGA of the digital signal processing board card, and the FPGA primarily preprocesses the collected digital signals, inputs the same into the DSP to complete preprocessing and sends results to the diagnosis service mainframe for analyzing, fault diagnosis and fault grading. The train bogie bearing service process monitoring and fault diagnosis system and method has the advantages of low cost, high engineering implementation performance and capability of realizing online realtime monitoring.

Train bogie bearing service process monitoring and fault diagnosis system and method

The invention relates to a small current grounding system fault line selecting method based on analytic graph solving and an SVM The method comprises the following steps that first judging whether a fault initial phase angle at the moment a fault occurs is equal and larger than 90 degrees and smaller than 270 degrees, if yes, utilizing EEMD to resolve a transient state zero sequence current in a 1/6 power frequency period, obtaining a zero sequence characteristic current through a related coefficient, and conducting Hilbert conversion on the zero sequence characteristic current; then selecting a characteristic analyzing point, and respectively obtaining virtual phase characteristic angles and constructing virtual phase characteristic angle vectors; finally, utilizing the virtual phase characteristic angle vectors to train an SVM1 classifier, inputting a test set, and outputting a line selecting result If the initial phase angle is smaller than 90 degrees and equal to and larger than 270 degrees, then utilizing the same processing method to obtain the virtual phase characteristic angle vectors, further training an SVM2 classifier, inputting a test set, and outputting a line selecting result It is proved by principle analysis and a simulation result, the principle of the line selecting method is simple, and line selecting accuracy is high

Small current grounding system fault line selecting method based on analytic graph solving and SVM

The invention discloses a method for recognizing the fault type of a feed line of a power distribution line, and the method comprises the steps: obtaining waveform sampling data, and sequentially carrying out the Hilbert-Huang transformation and band-pass filtering of the waveform sampling data; reconfiguring a time frequency matrix according to the band-pass filtering data, solving the singular value of the time frequency matrix, and forming feature vector matrixes; carrying out the normalization processing of all feature vector matrixes, and enabling the feature vector matrixes to serve as the input samples of a multi-stage support vector machine after normalization processing, so as to recognize the fault type of the feed line of the power distribution line. The invention also provides a device for recognizing the fault type of the feed line of the power distribution line. The multi-stage support vector machine is good in performance, is clear in logic, is simple, and can recognize four types of power grid faults: single-phase grounding faults, two-phase grounding faults, two-phase short-circuit faults and three-phase short-circuit faults. The method provided by the invention is stronger in adaptive capability, and still has a high recognition rate of fault types under the impact of noise.

Method and device for recognizing fault type of feed line of power distribution line

The invention relates to a classification line selection method for the single-phase earth fault of a resonance earthing system The classification line selection method comprises the steps of calculating the selected frequency band of the system according to the grid structure and the line parameters of a power distribution network, monitoring the bus zero sequence voltage waveform, judging whether the bus zero sequence voltage waveform meets the fault line selection starting condition, reading the waveform of one power frequency cycle of the line transient state zero sequence currents after the fault, carrying out EEMD on the fault zero sequence currents of a half of the power frequency cycle, summing Hilbert time-frequency spectrums and Hilbert marginal spectrums of all the line transient state zero sequence currents, calculating the frequency spectrum energy scale factor P, the transient state factor T and the Hilbert time frequency entropy S, classifying the faults by adopting a support vector machine, and carrying out line selection by adopting the corresponding line selection criteria for different fault types According to the classification line selection method, rich fault information in the transient state zero sequence currents is utilized fully, and the accuracy of fault line selection of the resonance earthing system is improved

Classification line selection method for single-phase earth fault of resonance earthing system

The invention relates to a power distribution network fault arc extinction method by connecting a neutral point to the ground through multi-level converter. The power distribution network fault arc extinction method is characterized in that the cascade H-bridge multi-level converter is adopted and directly connected at the position of the neutral point of a power distribution network through a reactor; at the initial moment when the power distribution network has a single-phase earth fault, synthetic operation is conducted to generate offset currents needed to be injected (img file='69356dest_path_image001. TIF'wi'19' he'=25' /), then the offset currents are quickly put into the multi-level converter, the multi-level converter is controlled by aid of the current tracking control algorithm and the PWM (Pulse-Width Modulation) modulation strategy to generate offset currents (img file='652784dest_path_image001. TIF'wi'19' he'=25' /), and the offset currents are put into the neutral point of the power distribution network so as to compensate grounding total currents of the fault point. In addition, the fault phase voltage is forced to be 0 constantly so the instantaneous grounding fault can be cleared automatically, and further the technical problem of the existing fault arc extinction technology of poor arc extinction effect can be solved.

Power distribution network fault arc extinction method by connecting neutral point to the ground through multi-level converter

The invention relates to a resonant grounding system fault line selection method with clustering achieved by means of time-frequency matrix singular values. The resonant grounding system fault line selection method comprises the steps that empirical mode decomposition is carried out on the transient-state zero-sequence current waveform of each circuit and the transient-state zero-sequence current waveform of a bus after a fault occurs to obtain a plurality of IMF components; Hilbert conversion is carried out on the IMF components to obtain a two-dimensional Hilbert gray-scale time-frequency spectrogram of transient-state zero-sequence currents; a time-frequency matrix of the transient-state zero-sequence current waveforms is constructed by means of HHT band-pass filtering; singular value decomposition is carried out on the time-frequency matrix to obtain a series of singular values which can reflect time-frequency characteristics of the waveforms, and the singular values serve as the characteristic quantity of transient-state zero-sequence currents of each circuit and the bus; vague C mean value clustering is carried out on the singular values to select a fault line. According to the resonant grounding system fault line selection method, influence of distributed capacitance and currents of a sound long line is avoided when a short line breaks down, and accurate line selection can be achieved under the conditions of high resistance grounding, noise interference, arc faults and the like.

One-phase grounding clustering line selection method of resonant grounding system

The invention relates to a method for selecting single-phase ground fault lines of power distribution networks on the basis of convolutional neural networks. The method includes acquiring zero-sequence voltages of busbars and zero-sequence current signals of various feed lines; carrying out continuous wavelet transformation on the various zero-sequence current signals according to set decomposition scales; acquiring time-scale wavelet coefficient gray-level graphs; identifying fault feed lines by the aid of trained convolutional neural network algorithms. The method for selecting the single-phase ground fault lines of the power distribution networks on the basis of the convolutional neural networks has the advantage that the fault feed lines and the non-fault feed lines can be accurately identified by the aid of the method under various fault working conditions when single-phase ground faults occur.

Yang Gengjie

Papers

Classification line selection method for single-phase earth fault of resonance earthing system

Power distribution network fault arc extinction method by connecting neutral point to the ground through multi-level converter

Distribution network ground fault arc suppression method based on three-phase cascade H bridge converters

One-phase grounding clustering line selection method of resonant grounding system

Method for selecting single-phase ground fault lines of power distribution networks on basis of convolutional neural networks