MMC-HVDC direct current transmission line fault positioning method

Abstract

The invention discloses an MMC-HVDC direct-current transmission line fault positioning method, which comprises the steps of decoupling bipolar voltage through a symmetric component transformation matrix to obtain a line mode component and a zero mode component of the bipolar voltage; carrying out VMD decomposition on the line mode component and the zero mode component, and carrying out parameter alternate optimization on the modal number k and the penalty factor in the decomposition process, so as to enable the values of the modal number k and the penalty factor to be more reasonable; performing analyzing by utilizing S transformation, positioning a fault mutation point, and accurately detecting the time when the wave head of the traveling wave arrives at two sides; and achieving accuratepositioning of the fault of the high-voltage direct-current transmission line by using a fault distance measurement algorithm for eliminating the wave velocity influence. According to the method, thenumber K of modes and the penalty factor are optimized through an alternate parameter optimization method, on the basis, the VMD is used for decomposing the traveling wave signal and extracting the intrinsic mode component of the traveling wave signal, then S transformation is used for accurately positioning a fault mutation point, and finally accurate fault positioning is achieved.

Description

technical field [0001] The invention relates to direct current transmission technology, in particular to an MMC-HVDC direct current transmission line fault location method based on improved VMD and S transformation. Background technique [0002] In recent years, the scale of my country's power grid has continued to expand, followed by the continuous improvement of voltage levels and the continuous increase of transmission capacity. Compared with AC transmission, HVDC transmission has better economy and larger transmission capacity, and also has many advantages such as easy power adjustment, narrow line corridor, and quick grid interaction. As an extremely important part of the power system, the MMC-based HVDC (High Voltage Direct Current Based on MMC, MMC-HVDC) system plays an irreplaceable role in the safe operation of the entire power grid. Therefore, it is necessary to conduct in-depth research on the fault location technology of DC transmission lines in MMC-HVDC systems...

AI Technical Summary

Problems solved by technology

[0004] There are literatures that use the current mutation polarity to realize the fault location of DC transmission lines, but this method has relatively high requirements for data synchronization at both ends

There are literatures that can accurately locate metallic faults, but the prerequisite for this method is that the phase angle of the current components at both ends of the fault point is consistent or the voltage at the fault point is zero. When a high-impedance fault occurs on the transmission line, this method The measurement accuracy will be greatly reduced

Some literatures have proposed a method for locating line faults by combining the amplitude ratio of different frequency components and the fault distance. Although this method avoids synchronous measurement, its application range is limited to distribution lines

Some literatures analyze the factors of bipolar faults and propose corresponding bipolar fault protection methods, but they do not consider the fault location of transmission lines in the event of ground faults.

Although some literatures have verified the feasibility of the fault waveform in the protection zone, the measurement accuracy needs to be further improved

Some literature proposes to use empirical mode decomposition (EMD) algorithm to realize fault location, but in the process of decomposing fault signals, modal confusion will occur, which will affect the accuracy of fault location

There are literatures that use S-transform to detect signal mutation points to detect faults, but this method cannot guarantee the measurement accuracy when the fault signal is affected by strong noise

Some literature proposes to use improved EMD to realize fault location, but it does not fundamentally eliminate the influence of modal aliasing on fault location

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