Study on the site selection for synchronous condenser responding to commutation failures of multi-infeed HVDC system

Power system shows increasingly prominent characteristic of strong DC and weak AC' at the primary construction stage of ultrahigh-voltage AC/DC hybrid power grid. Faults occurring in the receiving-end AC grid of the multi-infeed high-voltage DC (HVDC) system may result in simultaneous commutation failures (CFs) and short-time huge power shortage, which are great threats to the stability of power grid. Owing to the strong support ability in reactive power, rotary inertia, and capacity of short circuit, synchronous condenser (SC) has received more and more attention in restraining CFs of multi-infeed HVDC and speeding up transient recovery process after faults. From the angle of interplay between multi-infeed HVDC systems, this study analyses SCs' superiority in restraining CFs, and then determines the optimal dynamic reactive power compensation site layer by layer combining with multi-infeed interaction factor, multi-infeed effective short-circuit ratio, and relative-transient-voltage-drop-area index. Finally, this study proposes a reliable and applicable site selection scheme for SCs to restrain CFs of the multi-infeed HVDC system.