Abstract
The adverse impacts of commutation failure (CF) of a line-commutated converter (LCC)-based high-voltage direct current (HVdc) system on the connected ac system are becoming more serious for high-power ratings, for example, the development of ultra-HVdc systems. Aiming to solve the problem of CF particularly for higher power/current LCC HVdc systems, this paper proposes a new method, which utilizes a thyristor-based controllable capacitor (TBCC), to eliminate CFs. The topology of the proposed TBCC LCC HVdc and its operating principles are presented. Then, mathematical analysis is carried out for the selection of component parameters. To validate the performance of the proposed method, modified LCC-HVdc and capacitor-commutated converter (CCC)-based HVdc systems based on the modified CIGRE HVdc system are modeled in a real-time digital simulator. Simulation studies for zero impedance single-phase and three-phase faults are carried out, and comparisons are made with both LCC-HVdc and CCC-HVdc systems. Furthermore, voltage and current stress of the TBCC are investigated and power-loss calculations are presented. The results show that the proposed method is able to achieve CF elimination under the most serious faults while the increase of power losses due to the TBCC is small.
Highlights
D UE to the geographical separation of energy sources and load centers, Line Commutated Converter (LCC) based High Voltage Direct Current (HVDC) systems have been successfully applied for long distance bulk power transmission thanks to thyristor’s superior power handling capability and low operating power losses [1]
The adverse impacts of commutation failure (CF) of a line-commutated converter (LCC)-based high-voltage direct current (HVdc) system on the connected ac system are becoming more serious for high-power ratings, for example, the development of ultra-HVdc systems
To eliminate CF especially for LCC HVDC systems with higher power/current ratings (e.g., Ultra High Voltage Direct Current (UHVDC) systems), this paper proposes an approach using Thyrsitor Based Controllable Capacitor (TBCC)
Summary
D UE to the geographical separation of energy sources and load centers, Line Commutated Converter (LCC) based High Voltage Direct Current (HVDC) systems have been successfully applied for long distance bulk power transmission thanks to thyristor’s superior power handling capability and low operating power losses [1]. Due to the limited current handling capability of IGBTs compared with thyristors, their application in LCC HVDC systems with higher power/current ratings (e.g., UHVDC systems) is limited. Reference [24], from a different prospective, uses a superconducting fault current limiter to achieve faster recovery by limiting the AC fault current Another family of power electronics based methods uses shunt connected reactive power compensation devices at the inverter AC side [25], [26]. Those devices are utilized to help the recovery of AC voltage especially during remote fault so that the risk of CF can be reduced. To eliminate CF especially for LCC HVDC systems with higher power/current ratings (e.g., UHVDC systems), this paper proposes an approach using Thyrsitor Based Controllable Capacitor (TBCC). The detailed insertion strategy of TBCC is explained
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