Influence of AC Outlet Mode of Converter Station on Energizing No-Load Converter Transformer

doi:10.12204/j.issn.1000-7229.2021.09.012

Abstract

Abstract:

In recent years, the proportion of cable lines in the transmission grid has increased. It may have impact on the resonance characteristics between the converter station and the transmission grid. In order to analyze the effect of the AC outlet mode of converter station on energizing the no-load converter transformer, the phenomenon of inrush current and ferromagnetic resonance is introduced, and different AC outlet modes with overhead lines and cables are established. Taking typical ± 500 kV DC project in China as an example, by means of the PSCAD/EMTDC, the influence of inrush current and ferromagnetic resonance caused by different outlet modes, the ratio of the cable in total lines and the closing resistance of the breaker are analyzed. Results show that different outlet modes have no significant effect on the inrush current, but the cable outlet mode is more likely to cause ferromagnetic resonance, and the higher the cable ratio is, the easier the ferromagnetic resonance occurs. Meanwhile, the suppression effect of closing resistance on inrush current and ferromagnetic resonance is verified.

Key words: HVDC, converter transformer, no-load energize, inrush current, ferromagnetic resonance

CLC Number:

TM406

WANG Tongtong, WEN Jun, JIN Haiqiang, HAN Minxiao. Influence of AC Outlet Mode of Converter Station on Energizing No-Load Converter Transformer[J]. ELECTRIC POWER CONSTRUCTION, 2021, 42(9): 112-119.

Figures/Tables 12

Fig.1 Schematic diagram of no-load transformer closing of single-pole DC converter

Fig.2 Equivalent circuit of no-load closing of the converter transformer

Fig.3 Flux waveform after closing (excluding transient magnetic flux attenuation)

Fig.4 Magnetization curve of Converter transformer core

Fig.5 Parallel ferromagnetic resonance

Table 1 Basic parameters of converter transformer

Fig.6 Excitation characteristic curve of converter transformer

Table 2 Results of inrush current

Fig.7 Inrush current waveform excluding Rs at M1(σ=0)

Fig.8 Voltage and current waveform during ferromagnetic resonance without closing resistance at M2 (σ = 0.8)

Table 3 Simulation results of ferromagnetic resonance(without closing resistance)

Fig.9 Converter bus voltage and current waveform with closing resistance at M2 (σ = 0.8)

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