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Influence of the converter transformer valve-side bushing fault on commutation reactance protection and improvement scheme

Zhang Yanxia, Dong Guanghao, Wei Le, Ma Jinting, Du Shanshan

Archives of Electrical Engineering

2023

Vol. 72, nr 3

715--735

Commutation reactance is an important component in the voltage-source converter-based high-voltage direct current (VSC–HVDC) transmission system. Due to its connection to the converter, when there is a fault occurring on the valve-side bushing of a converter transformer, the nonlinearity operation of the converter complicates the characteristics of current flowing through commutation reactance, which may lead to maloperation of its overcurrent protection. It is of great significance to study the performance of commutation reactance overcurrent protection under this fault condition and propose corresponding improvement measures to ensure the safe and stable operation of AC and DC systems. In the VSC–HVDC system with the pseudo-bipolar structure of a three-phase two-level voltage source converter, the valve has six working periods in a power frequency cycle, and each period is divided into five working states. According to the difference between the fault phase and non-fault phase of the conductive bridge arms at the time of fault occurrence, these five working states are merged into two categories. On this basis, various faults of the valve-side bushing of a converter transformer are analyzed, and the conclusion is drawn that the asymmetric fault of valve-side bushing can lead to the maloperation of the commutation reactance overcurrent protection. Based on the characteristics that the current flowing through the commutation reactance after the asymmetric fault of the valve-side bushing contains decaying aperiodic components in addition to the fundamental frequency wave, a scheme to prevent the maloperation of commutation reactance overcurrent protection is proposed, which uses the unequal of two half cycle integral values with different starting points to realize the blocking of commutation reactance overcurrent protection, and it makes up the deficiency of existing protection in this aspect. Finally, this paper builds a VSC–HVDC system simulation model in the PSCAD/EMTDC platform to verify the effectiveness of the scheme.

Układy przesyłowe prądu stałego i urządzenia FACTS – Komitet Studiów B4

Madajewski K.

Energetyka

2009

nr 3

171-177

Omówiono referaty zaprezentowane na sesji plenarnej Komitetu Studiów B4 CIGRE "Połączenia prądu stałego i urządzenia energoelektroniczne w systemach elektroenergetycznych" obejmujące trzy tematy preferowane: Rozwiązania konwencjonalne oraz UHV układów HVDC, Nowe rozwiązania i wdrożenia urządzeń energoelektronicznych oraz Zastosowania układów FACTS i nowe rozwiązania w tym zakresie.

Discussed are papers delivered on the CIGRE Study Committee B4 plenary session "Interconnections of direct current and power electronics devices in electric power systems" comprising three preferred subjects: Conventional and UHV solutions of HVDC systems, New solutions and implementation of power electronics devices and FACTS systems applications and new solutions in this field.