Multi-terminal flexible DC system with inductive superconducting current limiter and DC circuit breaker

Abstract

The invention discloses a multi-terminal flexible DC system with an inductive superconducting current limiter and a DC circuit breaker. The system comprises m current converter stations which are connected to the same DC power transmission network frame, and the current converter stations are connected with each other through n-loop DC circuits. Each current converter station employs a true bipolar structure. The MMCs of the positive and negative electrodes are connected to the positive and negative DC busbars of the current converter station through the inductive superconducting current limiter. The DC circuit breaker is installed between a DC line and a DC bus, and the inductive superconducting current limiter is formed by the series connection of a superconducting current limiter body and a steady-state overcurrent protection device. The system is based on the inductive superconducting current limiter, so the system can reduce the requirements of the ON / OFF currents of the DC circuit breaker in a multi-terminal flexible DC grid, wherein a superconducting winding does not have a quench state and the recovery time is short, so that the system has a restart possibility. The systemcan replace the role of a smoothing reactor in fault current suppression, and avoids the adverse effect of the smoothing reactor on the performance of the DC system.

Description

technical field [0001] The invention belongs to the technical field of electric power transmission and distribution, and in particular relates to a multi-terminal flexible direct current system including an inductive superconducting current limiter and a direct current circuit breaker. Background technique [0002] The new generation of power transmission technology represented by flexible direct current has shown great development potential in the field of long-distance large-capacity power transmission in recent years. From the perspective of its own physical characteristics, flexible DC transmission technology avoids the problem of commutation failure, and can still maintain a certain power transmission capacity during AC faults without power interruption, reducing the power / capacity energy faced by the receiving end grid during faults Impact; From the perspective of topology, the flexible DC system is easy to form a multi-terminal structure for decentralized access to th...

AI Technical Summary

Problems solved by technology

However, in reality, the short-circuit current of a high-voltage large-capacity flexible DC transmission system can usually rise to dozens of times the rated value within a few milliseconds after a fault, far exceeding the breaking capacity of current high-voltage DC circuit breakers.

At present, the method of installing a smoothing reactor on the DC line is usually used to reduce the requirements for the breaking current of the circuit breaker. Although the smoothing reactance can suppress the fault current rising rate to a certain extent, an excessively large smoothing reactor will increase The response time of the large DC system may even lead to instability of the DC system

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