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.