Inverter turn-off angle control optimization of UHVDC with hierarchical connection to AC grid

Additional reactive power control and emergency control of the ±1100 kV UHVDC system with a hierarchical connection mode

“…Under the constant extinction angle control, a control strategy to balance DC voltage is proposed in [14]. The inverter turn‐off angle control is optimised to improve the receiving ability of the receiving AC systems with the hierarchical connection mode in [15].…”