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The Kunliulong DC project, developed and operated by China Southern Power Grid Co., is currently the world’s largest UHV multi-terminal DC transmission system — but that’s not the only major industry milestone associated with this project.
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The Kunliulong DC project, developed and operated by China Southern Power Grid Co., is currently the world’s largest UHV multi-terminal DC transmission system — but that’s not the only major industry milestone associated with this project. It’s also the world’s first UHV multi-terminal hybrid DC project, the world’s first MMC based UHV DC converter station project, and the world’s first project of this type with the ability to self-clear DC faults on overhead lines.

Kunliulong is a three-terminal hybrid ±800 kV DC system, consisting of an LCC-based converter station at the sending end and two MMC-based converter stations at the receiving end. Kunliulong is a key demonstration project for trans-provincial power transmission in China, with a transmission capacity of 8 GW.  This milestone project had been put into operation at the end of 2020.

China Southern Grid owns and operates one of the world’s largest real-time power system simulators and has a wealth of experience and expertise in applying this technology to challenging projects. Their RTDS Simulator was used to conduct over 2,000 individual tests related to the Kunliulong project.

The RTDS Simulator allows China Southern Grid to perform hardware-in-the-loop testing of the HVDC controls. The real-time simulator provides an electromagnetic transient representation of the converter stations and the AC network.

China Southern Grid used the RTDS Simulator’s GTFPGA-based auxiliary hardware to run highly detailed MMC valve models for the receiving end stations. With these models, each IGBT can be fired individually, allowing for non-standard operating states to be represented, and a mixed half- and full-bridge submodule valve configuration is supported.

The simulation is then physically connected to the HVDC control and protection system in a closed loop. In this way, nearly 2,000 individual tests were carried out with the RTDS Simulator to comprehensively verify the performance of the system under various conditions. Hardware-in-the-loop testing supported the commissioning process for the Kunliulong multi-terminal system, ensuring a smooth transition into reliable, secure operation of a landmark asset with so much to offer to the Chinese grid.

Learn more about HVDC control and protection testing with the RTDS Simulator here.