Fault protection method and system for hybrid cascaded multi-terminal direct-current power transmission system

Abstract

The invention discloses a fault protection method for a hybrid cascaded multi-terminal direct-current power transmission system. The fault protection method comprises the following steps: detecting that one of at least two modular multilevel converters connected in parallel in an inversion converter station has a fault; the inverter converter station immediately locking the faulty modular multilevel converter and tripping off an alternating current switch connected with the modular multilevel converter, and sending a phase shift command to the rectifier converter station through inter-stationcommunication; the rectification converter station immediately executing phase shift after receiving the command; and after the inverter converter station waits for a first preset time, locking othernon-fault modular multilevel converters connected in parallel. According to the invention, the problem of sub-module overvoltage caused by simultaneous locking of modular multilevel converters in a hybrid cascaded multi-terminal direct-current power transmission system can be effectively solved, the energy demand of a direct-current energy consumption device can be effectively reduced, and the safety of each device can be better protected.

Description

technical field [0001] The invention belongs to the field of direct current transmission, and in particular relates to a fault protection method and system for a hybrid cascade multi-terminal direct current transmission system. Background technique [0002] In recent years, integrated LCC-HVDC has low cost, low loss, mature operation technology and VSC-HVDC can realize active power and reactive power decoupling control, can supply power to passive network, compact structure, small footprint, and no inverter The hybrid DC transmission technology for the problem of commutation failure on the rectifier side has achieved rapid development and has good engineering application prospects. By using LCC-HVDC on the rectifier side and VSC-HVDC on the inverter side, the commutation failure on the inverter side can be reduced or avoided. problems, and at the same time guarantee the advantages of project cost to a certain extent. [0003] In order to meet the requirements of long-distan...

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Problems solved by technology

[0004] The purpose of the present invention is to provide a hybrid cascaded multi-terminal direct current transmission system fault protection method and system, which can effectively solve the sub-module overvoltage caused by simultaneous blocking of modular multi-level converters in the hybrid cascaded multi-terminal direct current transmission system problems, can effectively reduce the energy demand of DC energy-consuming devices, and better protect the safety of various equipment

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