A method for handling DC side faults of flexible DC power grids

Abstract

The invention provides a method for processing faults on the DC side of a flexible DC power grid. The method includes: calculating the auxiliary inductance parameters for DC side fault protection of the DC power grid; detecting the fault parameters of the DC power grid, and judging the fault location according to the parameters; position action. The technical solution provided by the invention can quickly and accurately isolate faulty lines, ensure that non-faulty parts continue to operate normally during the fault process, and realize reliable protection for DC faults. The selection principle of the auxiliary inductance of the DC circuit breaker provided by the invention can solve the problem of insufficient discrimination of DC faults and realize the protection selectivity.

Description

technical field [0001] The invention belongs to the field of safety and protection of direct current power grids, and in particular relates to a method for processing faults on the direct current side of a flexible direct current power grid. Background technique [0002] High voltage direct current grid (HVDC grid) technology is one of the effective methods to solve large-scale new energy collection, long-distance transmission and large-scale consumption. Among them, the modular multilevel converter (MMC) has become the first choice for the construction of HVDC grid converter stations due to its characteristics of bidirectional power flow, no commutation failure, and fast decoupling control of active and reactive power. Technical solutions. [0003] Although the MMC-based HVDC grid has many advantages, it still faces many unresolved technical problems, especially the protection of the grid under DC faults, such as fault identification, location, and isolation. Since the im...

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Problems solved by technology

For example, the "handshake principle" discloses identifying and isolating faulty lines by detecting DC line voltage and controlling AC circuit breakers and DC switches. Tens of milliseconds are slow, and the system recovery time is long, so it may cause harm to the operation of the DC grid and the AC grid connected to it

Secondly, although self-blocking MMC can be used for fault isolation on the DC side, this type of MMC increases the investment cost of the converter station, and can only avoid the overcurrent of the converter itself, but cannot completely isolate the DC fault. resulting in short-term outages of all converter stations in the DC grid

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