Method for tripping during re-unlocking frequency overlimit after temporary locking of flexible DC control system

Abstract

The invention provides a method for tripping during re-unlocking frequency overlimit after temporary locking of a flexible DC control system. When an AC system of a connected variable network side is in a short-term failure, a valve control system judges bridge arm overcurrent, temporary locking of the valve control system is triggered and a pole control system is informed to lock, after bridge arm current gradually declines, the temporary locking state disappears and the pole control system is re-unlocked after a certain time delay. When the connected variable network side is in a serious failure, the valve control system and the pole control system can repeatedly be subjected to temporary locking and unlocking processes, and the pole control system achieves a locking tripping function when the unlocking frequency exceeds the limit. According to the method, the crossing success rate of the flexible DC control system in an AC failure is improved and primary equipment of a flexible DC converter valve is also protected.

Description

technical field [0001] The invention belongs to the technical field of electric power electronic control, and in particular relates to a method for tripping over a value of the number of times of re-unlocking after a flexible DC control system is temporarily locked. Background technique [0002] The flexible DC converter valve technology based on the modular multilevel converter (MMC, hereinafter referred to as MMC) has independent adjustment of active and reactive power, no need for large-capacity reactive power compensation and filters, and no commutation The failure, the receiving end can be connected to the passive system and other advantages, mainly used in new energy power generation system networking, asynchronous grid connection and other occasions. [0003] Flexible DC transmission systems generally use modular multilevel converters as primary equipment. MMC consists of 6 bridge arms (hereinafter referred to as converter valve bridge arms in this application), and e...

AI Technical Summary

Problems solved by technology

[0004] When the AC failure of the flexible DC transmission system is connected to the substation side, due to factors such as control system sampling delay, communication delay, and internal link delay of the control device, under rated power operation, a failure occurs on the connection substation side, which may easily cause replacement. Throttle valve bridge arm current overcurrent

At present, the industry generally adopts the method of directly blocking the converter valve and tripping after the bridge arm is over-current, and isolating the converter valve from the AC system to protect the converter valve equipment. This method reduces the ride-through of the flexible DC transmission technology in dealing with AC system faults. rate, the flexible direct current direct current transmission technology based on MMC has not been fully utilized

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