Comparative Study on Small-Signal Stability of LCC-HVDC System With Different Control Strategies at the Inverter Station

The constant extinction angle control and constant DC voltage control are widely used for the inverter station of Line Commutated Converter based High Voltage Direct Current (LCC-HVDC) system in practical engineering. Under different control strategies, the control system parameters would have totally different effects on the stability of the LCC-HVDC system. In this paper, the small-signal models of the LCC-HVDC system with constant extinction angle control and LCC-HVDC system with constant DC voltage control are developed, respectively. Based on the eigenvalue analysis, this paper conducts a comprehensive comparison of the effects of a phase-locked loop (PLL) and LCC controller on the small-signal stability of LCC-HVDC system with different control strategies at the inverter station under weak AC grid condition. Then, the coupling effect between the PLL and LCC controller parameters is investigated when LCC-HVDC system adopts different control strategies. This paper can provide useful guidance for the systematic design and control parameter selection of LCC-HVDC projects.