Abstract:
For sub-/super-synchronous oscillation of renewable energy generation connected into line commutated converter-based high voltage direct current transmission (LCC-HVDC), the existing research mainly adopts the impedance reshaping method of renewable energy to achieve oscillation suppression. Considering the constraints of a large number of grid-connected units, multiple unit types, and fault ride-through performance in the actual system, the design margin is limited. LCC-HVDC impedance reshaping is utilized in this paper to achieve sub-/super- synchronous oscillation suppression. First, the LCC-HVDC impedance reshaping control strategy is proposed, with the fixed trigger angle control adopted at the sending-end converter station and dc current control adopted at the receiving-end converter station. Subsequently, an analytical impedance model of LCC-HVDC considering impedance reshaping is established, and the accuracy of the impedance model is verified. Next, the changes of impedance characteristics between before and after impedance reshaping are compared, and the mechanism of the impedance reshaping control strategy is expounded to eliminate the negative damping caused by the overlapping effect between the original dc current loop and the power circuit at the sending-end converter station. Furthermore, with the LCC-HVDC impedance reshaping control, the system impedance characteristics at the interconnect point of renewable energy units is optimized, and the stability margin of different types of renewable energy bases, including permanent magnet synchronous generator (PMSG), doubly-fed induction generator (DFIG) and photovoltaic (PV), connected into LCC-HVDC can be improved. Finally, simulation results of different types of renewable energy bases connected into LCC-HVDC verify the effectiveness of the proposed LCC-HVDC impedance reshaping-based oscillation suppression strategy.