Point of Connection Voltage Regulation Strategies for AC Connected Large Offshore Wind Farms

The offshore wind energy generation industry is developing rapidly in the UK. The long submarine cable connection needed between the wind turbine generators and the onshore Point of Connection (PoC) introduces additional difficulties for compliance with the GB Grid Code reactive power requirement. To address this problem, this paper investigates different PoC voltage regulation strategies. The methods are compared in terms of control requirements, fault behaviour of the wind farm and economics. It is shown that for long connection distances to the PoC, additional dynamic reactive compensation equipment and/or a tap-changing transformer at the offshore platform will probably be needed for Grid Code Compliance. It is shown that a strategy where a STATCOM solely regulates the PoC voltage, leads to increased capital expenditure. However, this provides advantages in respect to its simplicity, speed of PoC voltage regulation and wind turbine behaviour for a fault at the PoC.