Control and operation of a hybrid HVDC integrating wind farm based on SB‐MMC and LCC

To integrate offshore wind power, a hybrid high‐voltage DC (HVDC) system consisting of the self‐blocking modular multilevel converter (SB‐MMC) and line commutated converter (LCC) is investigated. The SB‐MMC is installed at the sending end to support the wind farm and the LCC is installed at the power grid side. The start‐up strategy of the hybrid system is studied. To eliminate the transients during start‐up, a virtual limiting resistor is introduced for the LCC and a grouping sequentially charging method is proposed for the SB‐MMC. The DC fault behaviour and isolation of the hybrid system is analysed. The response during AC fault and commutation failure at LCC is considered. Finally, the feasibility of start‐up, DC fault isolation and AC fault ride through of the hybrid HVDC system is verified by simulations in power systems computer‐aided design/electro‐magnetic transient design and control.