Flexible direct-current power distribution network monopole fault line selection and section positioning method and system

Abstract

The invention discloses a flexible direct-current power distribution network monopole fault line selection and section positioning method and system. The method comprises the steps that positive and negative currents of each feeder line of a direct-current power distribution line are collected and filtered; current sudden change data in a data window is extracted, S-transform is carried out on thedata to obtain a complex time-frequency S matrix of current signals; a characteristic frequency band is calculated according to line parameters; STCFB and W are calculated according to the complex time-frequency S matrix; a monopole fault line selection criterion and a section positioning criterion of the direct-current power distribution feeder lines are established, and fault feeder line identification is carried out on the basis of current sudden change Pearson correlation coefficients according to the line selection criterion; if the line is a faulty feeder line, the transient energy sumsof positive current and negative current sudden change characteristic frequency bands are compared for fault pole judgment; if the line is a faulty polar line, fault feeder line identification is carried out by using current sudden change correlation between the left side and the right side of each feeder line section. The method is not affected by factors such as transition resistance, data asynchronization and fault positions, and is rapid, sensitive and reliable.

Description

Technical field [0001] The invention relates to the technical field of fault line selection and positioning of a direct current distribution network, in particular to a method and system for single-pole fault line selection and section positioning of a flexible direct current distribution network. Background technique [0002] With the rapid development of power electronic devices and the massive demand for renewable energy, DC transmission and distribution technologies based on voltage source converters have developed rapidly. The Medium-Voltage DC (MVDC) distribution network has the characteristics of low line loss, high power supply efficiency, and excellent power quality. It has significant advantages in the integration of distributed power sources and the construction of urban DC power grids. Modular multilevel converter (MMC) has low switching frequency, low loss, and excellent dynamic and static voltage equalization, so it is more popular in flexible DC projects. At prese...

AI Technical Summary

Problems solved by technology

[0006] The existing technology uses the least square method to calculate the equivalent reactance value, but it is difficult to identify the specific feeder in the multi-branch system

[0007] Existing technologies comprehensively use three criteria, the polarity that first reaches the fault current threshold value when a fault occurs, the time difference between two poles to reach the threshold value, and the current change rate with time to detect internal and external faults. The method is too complicated

[0008] The existing technology constructs a zero-mode sequence network to identify line capacitance parameters, which can effectively identify the faulty feeder, but it is difficult to locate the faulty section on the faulty feeder

[0009] The existing technology uses wavelet transform for multi-scale analysis, and uses the high and low frequency energy differences of transient quantities to construct criteria, which can correctly judge faults, but the calculation results of wavelet transform are easily affected by wavelet base selection and noise

[0010] In summary, the existing methods for unipolar fault identification of DC power grid have their own characteristics, but there is no method with strong reliability, no influence of transition resistance, etc., and high sensitivity

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