Flexible DC converter valve AC connecting line single-phase earth fault protection system and method

Abstract

The invention relates to a flexible DC converter valve AC connecting line single-phase earth fault protection system and method. The method comprises the following steps that 1) an earth fault is detected according to flexible DC converter protection or valve control; (2) the fault converter valve is locked, and information is sent to pole control; 3) the pole control sends the information to the pole protection, and comprehensively judges the protection action condition; (4) only 800kV pole differential protection action is performed, and the whole pole is locked and stopped immediately; 5) whether converter protection or valve control imbalance protection is earlier than 400kV low-end valve group differential protection or not is judged; (6) a fault VSC converter valve is stopped firstly and a non-fault VSC converter valve is stopped in a delayed mode by means of flexible direct current converter protection or valve control imbalance protection action information; (7) on the basis of the 400kV low-end valve group differential protection action information, the fault VSC converter valve is stopped firstly, and the non-fault VSC converter valve is stopped in a delayed mode; and 8) the protection action process is ended. The system and method can be widely applied to the field of power grid safe operation.

Description

Technical field [0001] The present invention relates to a single-phase ground fault protection system and method for a flexible transmissive valve AC connection line, particularly with respect to a single-phase ground fault protection method for a single-phase grounding valve AC connection line for mixed grade high pressure DC engineering. Belong to the security operation of the grid. Background technique [0002] Based on the high-voltage DC transmission of the LINE COMMUTATED CONVERTER, LCC, is commonly referred to as conventional DC, has the advantages of large capacity, long distance, low loss, suitable for power transmission from a large power source base to a long-distance load center However, the problem of displacement failure of the LCC converter valve, and normal operation requires the support of the grid voltage, there is a certain requirement for the intensity of the access. Based on the flexible DC transmission of Voltage Sourced Converter, VSC) has the advantages of...

AI Technical Summary

Problems solved by technology

[0004] However, in the hybrid cascaded UHVDC project with bipolar wiring, when a single-phase ground fault occurs in the AC connection line of the flexible DC converter valve, due to the continuous injection of electric energy in the rectifier station and the existence of the freewheeling path of the diode, only the AC connection The line differential protection action blocks the faulty converter valve, and the DC converter valve sub-module will withstand high voltage, which often exceeds the tolerance value of the converter valve sub-module overvoltage lockout and even the device, which can easily cause equipment damage

Therefore, for the single-phase grounding fault of the AC connection line of the flexible DC converter valve of the hybrid cascaded UHV DC project, the traditional protection settings are difficult to ensure the safety of the converter valve equipment, and new protection methods must be considered

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