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Mechanism Analysis of Near Fundamental-Frequency Positive/Negative-Sequence Oscillations in MMC-HVDC Connected Direct-Drive Wind Farm
YU Jing, LIN Hongfei, WANG Xiao, Lü Jing, WU Linlin, LI Yunhong
Electric Power Construction ›› 2024, Vol. 45 ›› Issue (2) : 10-25.
PDF(15619 KB)
PDF(15619 KB)
Mechanism Analysis of Near Fundamental-Frequency Positive/Negative-Sequence Oscillations in MMC-HVDC Connected Direct-Drive Wind Farm
Positive- and negative-sequence oscillation phenomena close to the fundamental frequency (40-60 Hz) occur in a practical modular multilevel converter-based high-voltage DC (MMC-HVDC) transmission system for new energy integration, which has led to a decrease in the power output of new energy sources. The mechanism of near-fundamental-frequency oscillations is more complex and has more influencing factors than oscillations in other frequency bands. This study focuses on the near-fundamental-frequency oscillation stability of an MMC-HVDC-connected direct-drive wind farm. Refined impedance models of the direct-drive wind turbine and sending-end MMC are established by considering positive and negative sequence controls. Based on the established impedance models, the mechanisms of the near-fundamental-frequency positive- and negative-sequence oscillations between the direct-drive wind farm and the sending-end MMC are revealed. In addition, the parameter phase-margin sensitivity is defined, and the key influencing factors of the near-fundamental-frequency oscillation stability of the interconnected system were analyzed quantitatively. Finally, an electromagnetic transient simulation model of the MMC-HVDC-connected direct-drive wind farm is developed. The near-fundamental-frequency positive- and negative-sequence oscillation phenomena in the actual project are reproduced, and the correctness of the near-fundamental-frequency oscillation mechanism analysis is validated.
wind farm / flexible DC transmission / near-fundamental-frequency oscillation / negative-sequence control / negative-sequence oscillation / sensitivity
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