Harmonic Instability Judgment Method for Light HVDC 12-pulse Converter

Abstract

The invention discloses a harmonic instability determination method for a light-weight high-voltage direct-current power transmission 12-pulse wave converter. The harmonic instability determination method comprises the following steps of obtaining a relation of modulation from a direct current side current to an alternating current side, and a relation of modulation from an alternating current side voltage to the direct current side according to a 12-pulse wave converter switching function modulation theory; for low-order harmonics, setting a direct current side fundamental frequency harmonic current to be Idcl(t) at a t moment; modulating the direct current side harmonic current to the alternating current side through the converter as follows: a formula which is as shown in the specification; in a (t+<delta>t) moment, obtaining harmonic voltage change as follows: a formula which is as shown in the specification; obtaining harmonic instability engineering criterion of a single-circuit direct current line according to current ratio at the (t+<delta>t) moment and the t moment as follows: a formula which is as shown in the specification; and when a formula which is as shown in the specification is workable, showing that the current in the direct current side system is increased constantly, the system is instable, and the harmonic instability is excited. According to the harmonic instability determination method, by combination with a direct current magnetic bias effect of a transformer, a direct current magnetic bias coefficient is introduced; negative sequence impedance parameters at the alternating current side are omitted; the alternating current side positive sequence secondary impedance and the direct current side fundamental frequency impedance are adopted to determine whether the harmonic instability occurs or not, so that the determination method is more accurate and reliable.

Description

technical field [0001] The invention relates to the field of high-voltage direct current transmission, in particular to a method for judging harmonic instability of a light-duty high-voltage direct current transmission (VSC-HVDC) 12-pulse converter. Background technique [0002] China has a vast territory, and the distribution of energy and load is extremely unbalanced. Hydropower resources are mainly distributed in the western region, coal resources are mainly concentrated in North China and Northwest China, but load centers are mainly distributed in the eastern coastal areas. Therefore, large-capacity long-distance power transmission is inevitable. Compared with traditional AC transmission technology, HVDC transmission has the advantages of high intelligence, large transmission capacity, low loss, and asynchronous networking, which makes it widely used in long-distance large-capacity power transmission and asynchronous networking projects. [0003] With the commissioning ...

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Problems solved by technology

[0005] The above studies are all aimed at six-pulse converters. However, most of the actual projects use 12-pulse converters. There are differences between 12-pulse converters and six-pulse converters in terms of circuit structure and converter transformer parameter configuration. , so it is necessary to conduct special research on the harmonic instability of the 12-pulse converter

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