Table 5 Topology of hybrid HVDC for OWFs

Hybrid-HVDC

VSC

LCC

Zeng et al. [108]

•  Cost saved

•  Power consumption reduced

•  Power flow

•  Difficult start-up

•  Commutation failure

****

LCC

VSC

Torres et al. [109]

•  Power losses cut down

•  Low possibility of commutation failure

•  Building scale

•  High capital cost

*

VSC(FB-MMC)

LCC

Li et al. [110]

•  DC fault cleared

•  Commutation failure rate reduced

•  High costs

•  High power losses

****

PWM-CSC

LCC

Xia et al. [111, 112]

•  Circuit structure simple

•  Coupling simple

•  Cost saved

•  Reactive power surplus

•  AC system voltage fluctuation

**

VSC(HB-MMC)

LCC

Torres et al. [115]

•  Ability of DC FRT enhanced

•  Oscillation is suppressed

•  System stability ensured

•  Great scalability

•  Complex control

•  Transmission distance

•  Realization of multi-terminal system

****