A fast protection method for inter-electrode faults of DC distribution network

Abstract

The invention discloses a direct current power distribution network interpolar fault rapid protection method. A fault transient electrical quantity and a line RL model are used to solve an inductanceparameter of a line, and a fault line is determined according to a size of the inductance parameter. In order to further improve sensitivity of this method, a small boundary inductor is connected in series to a head end of each line, and an inductance voltage is used to replace differential in the line RL model so as to eliminate a truncation error when a difference is used to replace the differential, reduce a calculated amount when a line inductance parameter is calculated, simultaneously simplify a calculation process, and reduce a requirement of an algorithm to a sampling rate.

Description

technical field [0001] The invention belongs to the field of relay protection of electric power systems, and relates to a fault protection method between poles of a flexible DC distribution network. Background technique [0002] In recent years, with the continuous improvement of users' requirements for power supply demand, power supply reliability, and power quality, as well as the widespread access of distributed power sources, energy storage devices, and DC loads, flexible DC distribution networks have received more and more attention. Attention and research, and become an important development direction of the future distribution network. However, compared with the AC system, the flexible DC distribution network has the characteristics of "low inertia and low impedance". The capacitive element) will quickly release energy to the fault point, causing the fault current to reach tens or even hundreds of kiloamperes within a few milliseconds, which seriously threatens the s...

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Problems solved by technology

[0006] (Xianyong Feng, Li Qi, Jiuping Pan. A Novel Fault Location Method and Algorithm for DC Distribution Protection. IEEE Transactions on Industry Applications, 2017, 53(3): 1834–1840) DC distribution network based on inductance parameter identification of line RL model The fault location method uses the fault transient data and the least square method to solve the RL model of the line, and obtains the line inductance from the protection installation to the fault point. The algorithm of this method is relatively complicated, and there is a certain truncation error if the difference is used instead of the differential.

[0007] (Li Meng, Jia Ke, Bi Tianshu, etc. Range-finding protection suitable for DC distribution network. Power Grid Technology, 2016, 40(3):719-724) The voltage drop of the current-limiting reactor at the outlet of the converter is used to replace Differentiation in the RL model gives the numerical solution formula of the line inductance parameters. Although this method is simple, has a small amount of calculation, and does not require high sampling frequency, it still cannot protect the full length of the line, and it is only applicable to the outlet of the converter. In the case where the current limiting reactor can be used as local information, there are certain limitations

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