Research on Commutation Failure Suppressing Technology Based on Flexible LCC System

This paper proposes a flexible line commutated converter (LCC) system with a cascaded H-bridge connected serially on the valve side of the converter transformer to solve the intrinsic commutation failure problem of the traditional LCC system. The proposed system can realize the decoupled control of...

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Bibliographic Details
Published in2020 5th International Conference on Power and Renewable Energy (ICPRE) pp. 429 - 435
Main Authors Liu, Yindi, Zeng, Xiangjun, Luo, Yiping, Bao, Hailong, Ren, Maoxin, Cao, Junzheng
Format Conference Proceeding
LanguageEnglish
Published IEEE 12.09.2020
Subjects
cascaded H-bridge
commutation failure
grid voltage dip
LCC-HVDC
Mathematical model
power factor improvement
Reactive power
Renewable energy sources
Stability analysis
Valves
Voltage control
Voltage fluctuations
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Summary:This paper proposes a flexible line commutated converter (LCC) system with a cascaded H-bridge connected serially on the valve side of the converter transformer to solve the intrinsic commutation failure problem of the traditional LCC system. The proposed system can realize the decoupled control of the direct current (DC) bus voltage and the actual extinction angle through the LCC and the cascade H-bridge respectively. It can also improve low power factor issue of the traditional LCC system, which is analyzed and proved by the mathematical model of the flexible LCC system. Further, the coordinative control strategy fitting in with different grid conditions is presented and validated by the simulation model established in PSCAD/EMTDC. In comparison with the traditional LCC system, the proposed system demonstrates stronger ability to suppress commutation failure and maintain stability of DC bus voltage regardless of the depth of grid voltage dip. In addition, the proposed system will not increase the reactive power demand on the grid side during the fault time as the traditional LCC system. In contrast, it can offer reactive power support to the grid.
DOI:10.1109/ICPRE51194.2020.9233149