Judgment method for continuous commutation failure of DC system based on dynamic tracking of short-circuit ratio

Abstract

The invention provides a method for judging whether continuous phase changing of a direct-current system fails on basis of short-circuit ratio dynamic tracking. The method includes the following steps of calculating the ESCR and the MSCR i of an alternating-current system under the condition that the alternating-current system operates normally, calculating the ESCR and the MSCR i of the alternating-current system under the condition that line faults occur and power is cut off, sequencing the line faults, combining the poorest interlocking fault sets, calculating the ESCR 1 and MSCR 1 of the alternating-current system on the condition of interlocking faults, and judging whether phase changing fails. By means of the method, feature analysis is carried out on transient voltage instability accidents which probably exist in existing and planned alternating-current and direct-current hybrid power grids, fault screening and sequencing can be effectively carried out according to hazard degrees of alternating-current faults to stable operation of the direct-current system, by combination of the current transfer situation after the faults, the interlocking fault sets are reasonably built, and failures of continuous phase changing of the direct-current system and received-end power grid voltage instability risks after the faults can be quickly evaluated.

Description

technical field [0001] The invention belongs to the field of safety and stability analysis of electric power systems, and in particular relates to a method for judging continuous commutation failure of a DC system based on short-circuit ratio dynamic tracking. Background technique [0002] At present, my country's power grid has formed a North China-Central China AC interconnected power grid, and the East China Power Grid operates in isolation, and is connected to the North China-Central China Power Grid through a DC system. According to the plan, my country will build dozens of UHV DC projects in the next 10-20 years, and gradually form a UHV AC-DC hybrid power grid to supply power to the central and eastern load centers through UHV DC and AC systems. Conventional HVDC transmission systems require sufficient commutation voltage from the AC system at the receiving end, and will absorb a large amount of reactive power from the AC system after commutation failure occurs. After...

AI Technical Summary

Problems solved by technology

[0004] For the AC / DC hybrid fed into the receiving end grid, the more serious safety and stability problem is the possible cascading failure of the AC / DC system, that is, the failure of the AC system may cause the continuous commutation failure of the DC system, which in turn leads to DC blocking and greater power transfer to the AC channel, triggering a cascading power grid collapse accident

The current research methods for this problem are still single. In engineering, the time domain simulation method is mainly used. Through the transient stability simulation of various AC and DC system fault combinations, it is evaluated whether it will cause the continuous commutation failure of the DC system, and then cause more damage. It is a serious cascading failure; however, this method faces problems such as heavy workload and difficulty in enumerating potential failures

In addition, some studies have been carried out at home and abroad on the formation mechanism and evolution process of cascading faults, and analysis methods such as power flow transfer evaluation after faults and small-world characteristics of power grids have been proposed, which have promoted the development of cascading fault set construction technology; but the current Research methods mostly focus on theoretical analysis or summary of operating experience. How to propose an effective and practical method of cascading fault set construction in combination with the actual situation of the power grid still needs further research

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