Low Frequency AC Transmission - Elements of a Design for Wind Farm Connection

Low frequency AC (LFAC) provides an alternative to HVDC and HVAC connections for offshore wind farms. Charging current is reduced as compared to standard 50Hz or 60Hz transmission and cable length thus may be extended. LFAC links to wind farms may be interconnected to form an offshore network - a significant advantage over HVDC technology which currently lacks a matured circuit breaker technology to allow such networks. SPEN and University of Warwick, supported by Network Innovation Allowance funding in the UK, initialized a systematic study on the feasibility of an LFAC system. This paper summarises the initial design considerations. A system design for an LFAC connection is established and the key components discussed. The effect of lowering frequency upon transformer design is assessed by developing example designs for the both the wind farm and wind turbine transformer. The next stage of the study will be focused on optimisation of the components and system level simulations as well as cost benefit analysis to reveal the niche market of this technology.