Comparison of UPFC, SVC and STATCOM in Improving Commutation Failure Immunity of LCC-HVDC Systems

This paper compares the performance of unified power flow controllers (UPFCs), static var compensators (SVCs), and static compensators (STATCOMs) in commutation failure immunity (CFI) improvement of line-commutated converter-based high-voltage direct-current transmission (LCC-HVDC) systems. Theoretical analysis is presented to investigate the capacity requirements of SVCs, STATCOMs, and UPFCs to maintain the inverter-side ac voltage in the cases where three-phase faults occur on the receiving-end ac grids with different short-circuit ratio (SCR). Simulation studies were undertaken to validate the CFI improving performance achieved by UPFCs in comparison to SVCs and STATCOMs. Results of three-phase and single-phase fault tests manifest the superior CFI of LCC-HVDC systems having UPFCs installed.