Method and system for determining transient stability margin of alternating-current and direct-current hybrid system

Abstract

The invention relates to a method and system for determining the transient stability margin of an alternating-current and direct-current hybrid system. The method comprises the steps of: firstly, building a network structure maintenance model of the alternating-current and direct-current hybrid system, employing a 6-order electromechanical model for a synchronous generator, employing a standard electromagnetic model for DC, and employing an electromagnetic model for direct current; secondly, according to an universal energy function model, rewriting a six-order electromechanical model of the synchronous generator and the network structure maintenance model of the alternating-current and direct-current hybrid system, and determining the transient energy function of the alternating-current and direct-current hybrid system; thirdly, calculating an energy function change curve of the alternating-current and direct-current hybrid system after a fault by adopting a trapezoidal integral path method, performing analysis by utilizing the energy function change curve to obtain a transient stability criterion of the alternating-current and direct-current hybrid system; and finally quickly calculating the limit clearing time of the system by adopting a dichotomy to realize transient stability margin evaluation of the alternating-current and direct-current hybrid system. According to the method, the transient stability margin of the alternating-current and direct-current hybrid system is accurately evaluated in the scene that the alternating-current fault causes the commutation failure of a direct-current inverter side.

Description

technical field [0001] The invention relates to the technical field of an AC / DC hybrid system, in particular to a method and system for determining a transient stability margin of an AC / DC hybrid system. Background technique [0002] Due to the reverse distribution of energy bases and load centers, the DC transmission technology based on LCC-HVDC has been successfully applied to the field of long-distance large-capacity power transmission due to its high efficiency and low cost. Since the transmission technology was first put into commercial operation in Sweden, nearly 200 HVDC projects have been built around the world. In China, regional power grids have been interconnected through AC and DC transmission lines, of which DC transmission lines account for 1 / 3 of the transmission capacity. However, when the AC transmission line near the inverter station is disturbed, the probability of commutation failure of the DC inverter is very high. AC failure accompanied by commutation...

AI Technical Summary

Problems solved by technology

However, the DC system model established in this class is not accurate enough to describe the dynamic behavior of the DC system after a fault in detail, such as the disturbance caused by the AC system disturbance that may have a significant impact on the transient stability of the AC-DC hybrid system. DC commutation failure

[0006] Therefore, in the prior art, commutation failure is rarely considered when determining the energy function, making the evaluation of transient stability margin inaccurate

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