DC side fault positioning system and method of multi-end flexible DC power distribution system

Abstract

The invention relates to the field of relay protection of power systems, and discloses a DC side fault positioning system and method of a multi-end flexible DC power distribution system. The system includes a data acquiring module, a fault positioning module, a DC side fault protection module, and a result output module. The method herein includes the following steps: when a DC side line fault occurs, starting the low voltage over-current protection of a converter station, and transmitting a converter station locking signal; then using the phase jump characteristic of a hyperbolic tangent function to position a fault; locking respective bridge arm sub-module, based on the determination of whether a fault current stops attenuation, removing the DC fault current; after the disconnection of the fault line, closing the switch on non-fault lines. According to the invention, the method can position faults by using the characteristics of phase jump of the function when fault points and reference points match, which addresses the failure of conventional methods to start the closing of the switch by determining whether the corresponding DC line is energized. The method can also fast disconnect the fault lines and ensures normal operation of the non-fault lines.

Description

technical field [0001] The invention belongs to the field of power system relay protection, and in particular relates to a system and method for locating DC side faults of a multi-terminal flexible direct current transmission system (MMC-HVDC). Background technique [0002] With the development of controllable shutdown power electronic device technology, the flexible DC technology with voltage source converter (Voltage Source Converter, VSC) as the core component gradually occupies an important position in the field of DC power transmission and distribution. Compared with traditional point-to-point DC lines, multi-terminal flexible DC transmission systems are more conducive to reducing costs, system operating costs and saving line corridors. DC transmission networks based on this technology are considered to be an important development direction for future power systems. [0003] However, power systems based on flexible DC transmission technology face several technical diffi...

AI Technical Summary

Problems solved by technology

Traditional fault distance evaluation and delay action identification of radial multi-terminal DC transmission fault lines, but it is difficult to meet the requirements in terms of protection quickness; traveling wave signals and wavelet energy can quickly identify fault lines in multi-terminal flexible DC systems, but this This method requires a higher sampling rate, and the method of determining the threshold value of the wavelet energy criterion has great limitations; Based on the tripping of the AC circuit breaker to clear the DC fault, the action speed is slow, and when it is applied to the star multi-terminal flexible DC transmission system, it is impossible to start the reclosing measure by judging whether the corresponding DC line is live.

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