| Abstract |
For optimal energy extraction, wind turbines should operate at variable speed, with the rotor speed
depending on wind speed. In large wind farms, the wind speed will in general not be the same for all
wind turbines. To enable variable speed operation of wind turbines with (induction) generators and
optimal energy extraction, each turbine should preferably be equipped with its own ac/dc/ac converter.
Utilising a common ac/dc/ac converter in wind farms may reduce cost but requires all turbines to
operate at the same speed. This rotational speed can still be proportional to the average wind speed,
but no longer to the wind speed at each individual wind turbine. In this paper, the energy yield of these
two connection schemes is compared. For both schemes the optimal control strategy is determined,
based on wind speed and spatial wind speed distribution within the farm. Further the difference in
energy yield is determined for various wind speed regimes. The results obtained showed that the
reduction in energy yield found in the parallel-connected scheme is 1.44%, compared to the total
production of the individual connected scheme. Other aspects such as differences in costs and
mechanical stresses due to wind speed variations are not considered. |
