Method for starting modularized multi-level flexible direct-current transmission converter

Abstract

The present invention provides a method for starting a modularized multi-level flexible direct-current transmission converter. The method comprises: connecting a direct-current side pole of each converter station, disconnecting an alternating-current circuit breaker of each converter station, and locking a sub module of each converter station; closing an alternating-current circuit breaker of an active station at one end, and a power supply carrying out passive charging on the active station and the remaining converter stations by using startup resistors; after the passive charging is completed, bypassing the startup resistor of the active station, unlocking the remaining converter stations, and carrying out active charging to reach a rated voltage of a power module; interlocking the remaining converter stations, the converter stations charged by the active station carrying out unlocking and starting direct-current voltage control subjected to a slope until the power module is charged to the rated voltage; and unlocking the remaining converter stations, after entering into a controlled stage again, carrying out grid connection and switching a control policy to a normal operation policy, and increasing power, wherein the converter operates normally. According to the method disclosed by the present invention, voltage consistency of the power module in the starting process can be ensured, so as to avoid startup failure and protection locking caused by unevenness of the capacitance and voltage of the power module.

Description

technical field [0001] The invention relates to the field of flexible direct current transmission, in particular to a method for starting a modularized multilevel flexible direct current transmission converter. Background technique [0002] Modular multilevel converter (MMC) is a flexible DC transmission topology that is developing rapidly in the world at present. Before the converter is started, its core unit sub-modules are in an uncharged state. In order to enable the sub-modules to reach A reasonable and effective start-up method for modular multi-level flexible direct current transmission converters is essential to ensure the rated voltage at work and reduce the impact on the grid and primary equipment during sub-module charging. [0003] Chinese patent application number: 201210462977 discloses a start-up method for a modular multi-level flexible direct current transmission converter, focusing on a sub-module voltage equalization control method for a modular multi-leve...

AI Technical Summary

Problems solved by technology

[0005] In the existing converter start-up method, for the converter station charging on the DC side, the charging of the power modules is only carried out by gradually reducing the number of power modules to the number during normal operation when unlocking the controlled charging for the first time. Consider further reducing the number of input power modules to charge the voltage of the power modules to the rated working voltage. The voltage consistency is poor, and the capacitor voltage of the power modules is uneven, which may easily cause startup failure and protection lockout.

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