Hybrid cascade type direct-current fault ride-through system based on fault current limiter and control method

Abstract

The invention discloses a hybrid cascade type direct-current fault ride-through system based on a fault current limiter and a control method. The hybrid cascade type direct-current fault ride-through system is characterized in that: the fault current limiter is arranged between a hybrid cascade type direct current receiving end high-end LCC direct current outlet and a corresponding hybrid cascade type direct current receiving end low-end MMC direct current inlet; after an LCC has a commutation failure fault, a fault current limiter control system detects that MMC direct current reaches fault current limiter starting criterion current, a current limiting resistor is put in, the direct current fault current is suppressed, and an MMC valve group is prevented from being locked; and when a low-end MMC at the receiving end has a single-pole grounding fault, the fault current limiter blocks a discharge loop from the normal MMC and the fault MMC to a fault point by means of the topology of the fault current limiter, and the MMC valve group is protected. Through simple control, ride-through of a high-end LCC commutation failure fault of the receiving end is achieved, the recovery process is good, ride-through of the low-end MMC single-pole grounding fault of the receiving end can be achieved without any control receiving end, the fault current limiter does not adopt a full-control device, and meanwhile the development problem of a large-capacity direct-current circuit breaker is avoided.

Description

technical field [0001] The invention relates to the technical field of direct current transmission, in particular to a hybrid cascaded direct current fault ride-through system and a control method based on a fault current limiter. Background technique [0002] The hybrid cascaded HVDC transmission system adopts LCC at the sending end, high-end LCC and low-end half-bridge MMC parallel group (MMCB) in direct series at the receiving end, combines the respective advantages of LCC and MMC, and naturally has the ability to ride through DC line faults. In addition, The low-end MMCB at the receiving end can provide certain reactive power support for the high-end LCC and reduce the risk of commutation failure in the LCC. [0003] The thyristor valve group has ten times the over-current margin, but the fully-controlled device IGBT used by MMC is relatively fragile and can only withstand the over-current of twice the rated current. When a commutation failure occurs in the high-end LCC...

AI Technical Summary

Problems solved by technology

[0005] In view of the above problems, the object of the present invention is to provide a hybrid cascaded DC fault ride-through method based on a fault current limiter to overcome the current hybrid cascaded DC receiving terminal LCC commutation failure fault and MMC single-pole ground fault ride-through capability Insufficient problem

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