Single-end quantity protection method of a ring-shaped flexible power network line

Abstract

The invention belongs to the technical field of fault diagnosis of DC power network, in particular to a single-terminal quantity protection method of ring-shaped flexible power network line. The method comprises the following steps: measuring voltages of two terminals of additional inductors at the installation position of DC power line protection; The equivalent model of post-fault converter is established. The MMC is equivalent to the series circuit of capacitor and inductor, and the VSC and DCT are equivalent to the parallel capacitor on the DC side. The complex modulus network of DC line based on 0-modulus and 1-modulus is established. The initial value of the additional inductance voltage after the fault is obtained by solving the complex modulus network of the DC line. The relationship between the initial value of the additional inductor voltage and the fault types in and out of the region is obtained. The fault location identification criterion based on the initial value of additional inductance voltage is established and the fault location identification threshold is adjusted. Based on the initial value of the additional inductor voltage, the fault pole judgment criterion and the fault pole judgment threshold are established. Single-ended electrical quantity is used to identify faults quickly and accurately, and communication is not needed, and the reliability is high.

Description

technical field [0001] The invention belongs to the technical field of DC power grid fault diagnosis, and in particular relates to a single-ended quantity protection method for a ring-shaped flexible direct power grid line. Background technique [0002] Rapid and reliable identification of DC line faults is one of the technical difficulties in the development of multi-terminal flexible DC power grids. The DC fault protection of the flexible DC system is the key technology for the reliable and stable operation of the DC system, and its immaturity has become a bottleneck restricting the rapid development and wide application of DC power distribution technology. Due to the small inertia of the DC system, once the DC line fails, the fault process develops very rapidly, and the superposition of the outputs of multiple converter stations in the DC grid aggravates the fault hazards such as line overcurrent. Therefore, the rapid isolation and reliable and rapid identification of fa...

AI Technical Summary

Problems solved by technology

Some scholars have designed a complete protection scheme for multi-terminal flexible DC power distribution systems. Among them, the quick-acting protection can judge the fault type and fault interval based on the magnitude and direction of the line current, and the backup protection can solve the large-resistance grounding fault based on the unbalanced current of positive and negative poles. In addition, different from the above-mentioned protection based on electrical quantities such as fault current and voltage, some scholars have proposed the protection idea of ​​identifying system parameter values ​​to distinguish internal and external faults, but they are all based on DC systems at both ends. The structure is complex, there are many nodes, and the application of the protection principle based on parameter identification in the flexible DC power grid needs to be studied

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