Comparison of Three LCC-MMC Hybrid HVDC Links Based on AC Fault Response Characteristics

Combining the advantages of the line commutated converter (LCC) and the modular multilevel converter (MMC), and aiming at the projects of west-to-east power transmission in China, this paper studies three hybrid HVDC systems. Three systems include: rectifier are LCCs, inverter are half-bridge sub-module MMCs with diode in series; rectifier are LCCs, inverter are hybrid MMCs composed of half-bridge sub modules and full-bridge sub modules; rectifier are LCCs, inverter is a hybrid inverter with a LCC and half- bridge sub-module MMCs connected in series. First, this paper introduces the topologies and control modes of three hybrid HVDC systems. Then, three hybrid HVDC systems are built in PSCAD /EMTDC, and the response characteristics of AC fault at the inverter are compared and analyzed. Finally, based on the simulation results, the advantages and disadvantages of three topologies are summarized. The results show that under the receiving-end AC system fault, the response characteristics of scheme 1 are better than the other two schemes.