Adaptive reclosure method for monopolar grounding fault of true bipolar MMC-HVDC power transmission system

Abstract

The present invention discloses an adaptive reclosure method for the novel monopolar grounding fault of a true bipolar MMC-HVDC power transmission system. According to the invention, after the occurrence of a monopolar grounding fault and the isolation of a faulty electrode circuit, the grounding voltage Uf of the faulty electrode circuit is measured after the experience of a certain period of dissociation process. According to the principle of electrostatic induction between power transmission circuits, if Uf is larger than Uset, the residual voltage occurs to the circuit. A fault point has disappeared, and the fault is determined as a transient fault. After the time delay of delta t2, a faulty electrode converter is restarted. If the fault isolation is achieved by a DC circuit breaker, the DC circuit breaker needs to be re-switched on. If Uf is smaller than Uset, little residual voltage occurs to the circuit. The fault point still exists, and the fault is determined as a permanent fault. The faulty electrode converter is not restarted. By adopting the above method, the pre-judgment of a fault type can be realized without unlocking the converter, so that the secondary damage of the system is avoided. Compared with existing reclosure methods for the true bipolar MMC-HVDC power transmission system, the secondary overcurrent impact caused by the reclosure of a permanent monopolar grounding fault is effectively avoided.

Description

technical field [0001] The invention relates to the field of power system protection and control, in particular to a unipolar grounding self-adaptive reclosing judging method suitable for a true bipolar MMC-HVDC power transmission system. Background technique [0002] When a single-pole ground fault occurs in the overhead line of the true bipolar MMC-HVDC transmission system, after the faulty pole is isolated, the non-faulty pole can still continue to operate. Considering the high probability of transient faults during overhead line transmission, it is necessary to configure the reclosing method to judge the nature of the fault, so as to ensure that in the case of transient faults, the fault pole can be quickly restored after the fault disappears. [0003] At present, the reclosing method of the true bipolar MMC-HVDC configuration based on overhead line transmission is generally: after isolating the faulty pole line and going through a period of deionization process, unlock ...

AI Technical Summary

Problems solved by technology

[0004] Aiming at the problem that the reclosing method of the current overhead line flexible direct current transmission system will cause a secondary overcurrent impact to the system when the reclosing method overlaps with a permanent fault, the present invention proposes a new type of single-pole ground fault automatic Adapt to the reclosing method, and can realize the prediction of the nature of the fault

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