Differential protection system and differential protection method for flexible DC distribution network line

Abstract

A differential protection system and a differential protection method for a flexible DC distribution network line are provided. An FPGA-based protection device sends a sample pulse to a data collector. To achieve synchronized sampling and data window synchronization, line dual-end protection devices are arranged as a reference end and a following end respectively. The following end firstly sends a synchronization request command including a number of a sample and a corresponding time of the sample. The reference end returns information including a sample number and a corresponding sample time of the reference end after receiving the command sent by the following end. After receiving a corresponding data message of the reference end, the following end calculates a communication transmission time delay and a deviation between the sample times of the two sides. Through compensation of the communication transmission time delay and a secondary interpolation sampling synchronization method, synchronized sampling of the following end and the reference end is achieved. Through calculating the differential current of two ends of a direct current line, the method determines whether differential current protection criteria are satisfied and achieves differential protection of the direct current line. The system and the method can ensure correct actions on internal faults and correct non-actions on external faults.

Description

Technical field [0001] The invention belongs to the technical field of power system relay protection and safety control, and particularly relates to the realization of a line current differential protection method for a flexible DC power distribution network, especially after the flexible DC line passes through high-speed data communication and synchronization processing on both sides of the current differential Application in protection. Background technique [0002] In recent years, flexible DC transmission technology has developed very rapidly. Flexible DC transmission can realize multi-power supply and multi-drop-point power reception, without considering the frequency and phase synchronization between various power sources; and can effectively isolate various voltage disturbances in the AC system, and improve the power quality on the user side; at the same time; The voltage source converter itself is an excellent reactive power, transient voltage sag and harmonic compensati...

AI Technical Summary

Problems solved by technology

[0008] At present, in the protection of high-voltage DC lines, the main applications are overcurrent protection and traveling wave protection, which can basically meet the requirements for the operation of DC lines that have not yet constituted a DC network.

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