Analysis on Positive-sequence Second Harmonic Characteristic of Sympathetic Inrush Current for Converter Transformer

作者：Li, Xiaohua; Zhang, Dongyi^*; Ding, Xiaobing; Tian, Qing; Cai, Zexiang

来源：Automation of Electric Power Systems, 2018, 42(13): 202-207.

DOI：10.7500/AEPS20170522009

• Converter transformers
• DC transmission lines
• High voltage direct current
• Second harmonics
• Sympathetic inrush current

A number of DC 50 Hz protection malfunctions have occurred in recent years in China Southern power grid due to no-load closing of the converter transformers. The main cause is that the sympathetic inrush current of the operating converter transformer contains abundant positive-sequence second harmonic, which has been transformed to 50 Hz harmonic by converter. This paper analyzes the impact of the DC operation conditions, such as the AC system voltage and DC transmission power, on the tap of converter transformer and AC filters, which changes the positive-sequence second harmonic of sympathetic current finally. It also analyzes the imbalances of positive-sequence second harmonic of the double circuit DC transmission lines from the view of the positions of poles, current interconnection and so on. To avoid the malfunction of 50 Hz protection, some suggestions are proposed,such as decreasing the impedance of AC system, increasing the voltage of AC bus, limiting the transporting power of running pole, etc. The sympathetic inrush current of the other DC transmission line on the same pole as no-load closing pole should be concerned seriously.

• 出版日期2018-7-10
• 单位华南理工大学