Operating Characteristics and Control Strategy of HVDC Transmission with Controllable Line-Commutated Converter

The paper discusses the implementation of a controllable line-commutated converter (CLCC) in Nanqiao converter station to prevent commutation failure in multi-infeed high voltage direct current (HVDC) transmission systems. The CLCC utilizes an auxiliary branch to enhance commutation voltage and incorporates an IGBT (Insulated Gate Bipolar Transistor) in series with a thyristor, offering improved switching capacity. The topology, commutation process, and working principle of CLCC are introduced, along with a discussion on the control strategy for the CLCC-HVDC system. The control strategy of the CLCC-HVDC system is also described in detail in the paper. A simulation model of a 500kV HVDC transmission system, incorporating CLCC at the receiving end is presented. Simulation results demonstrate the system's performance under various conditions, showcasing its ability to prevent commutation failure caused by AC system faults and enhancing overall power system stability.