OWFs connection technology | Application | Benefits | Drawback | Economy | Complexity | Reliability | Feasibility | Superiority | |||
---|---|---|---|---|---|---|---|---|---|---|---|
HVAC | Transmission distance under 60Â km Small and medium capacity OWFs | High reliability Mature technology Simple structure | NO black start capability Large reactive power loss | *** | *** | *** | ** | ** | |||
HVDC | LCC-HVDC | Onshore station of OWFs transmit system Higher voltage levels Transmission | Low line cost and loss Asynchronous operation enhanced Mature technology | Large Harmonics Commutation failure NO reactive power capability Large converter station area Difficult in offshore station building | ** | *** | ** | ** | ** | ||
VSC-HVDC | VSC-HVDC (two-port) | Two or Three level VSC | Large-scale integration of OWFs Transmission distance over 100Â km Multi-terminal power grid Distributed power integration Ultra-high voltage levels transmission Distributed energy connection | Independent power control Power flow inversion realized Converter station area reduced No commutation failure problem | Higher power losses Expensive | *** | *** | **** | **** | *** | |
MMC-HVDC | Reactive power absorption absented Higher-power capability Better harmonic performance Inexpensive cable Black start | Short MMC lifetime Huge submodule capacitors Expensive MMC submodule | **** | *** | **** | *** | *** | ||||
MTDC-VSC | MTDC (two level) | Flexible power flow control realized Low Loss High grid security and supply security Renewable power balance improved Congestion is reduced | Pole-to-pole and pole-to-ground faults High fault current | *** | **** | *** | *** | *** | |||
MMC-MTDC | Device efficiency utilized Investment and operational costs are reduced System redundancy increased High flexibility Facilitate access to DC load | Poor dynamic response of voltage adjustments Irrational power allocation Complex control system | **** | *** | *** | *** | **** | ||||
Hybrid-HVDC | Ultra-high voltage and flexible power transmission Large-capacity and high DC failure rate OWFs | Lower switching loss Smaller investments | Power flow reversed problem Start-up difficult Commutation failure | **** | **** | *** | *** | **** | |||
DR-HVDC | Large-capacity OWFs Transmission distance over 100Â km | Volume and weight of offshore platform reduced Transmission capacity increased Transmission losses and costs decreased | AC voltages less set up No start-up powers No reactive power provisions Lack of control possibilities | **** | *** | **** | **** | **** | |||
ALL-DC | Series-connection WTs | Medium and large capacity OWFs Transmission distance over 100Â km | Offshore platform eliminated Capital cost reduced | Insulation trouble Strong power-voltage coupling | ***** | ** | **** | *** | **** | ||
Parallel-connection WTs | High reliability Flexible operation Cost decreased | High DC/DC convert gain Difficult voltage control | ***** | ** | **** | **** | **** | ||||
LFAC | Medium capacity OWFs OWFs integration at a range of 80 km–180 km | Cost reduced High transportation efficiency Low system complexity | Size of offshore transformer Technology is not mature enough | ***** | *** | **** | *** | **** |