Optimisation Modelling for Offshore Wind Farms

Offshore wind farms have emerged as the biggest
contributor of renewable energy to the national grid over the
last decade, driven by advanced technology, higher investment,
and lowering operational and maintenance costs. This
demonstrates the value of improving the efficiency in wind
farms, with designs to be selected for the most effective
transmission system implementation.
This paper describes the simulation models developed with
network simulation software (IPSA and PowerWorld) for
evaluating and analyzing the load flow by observing the losses,
voltage magnitude and transmitted power, both active and
reactive. There were three different models, one using standard
inter-array cable (33 kV) and one with upgrade inter-array
cable to 52 kV. The third model proposed replacing high voltage
side transformers with a mechanically switched capacitor
(MSC) rather than the usual static Var compensator.
Results from 52 kV models revealed that high voltage cable in
offshore wind farms is capable of transmitting more active
power than medium voltage. Indeed, the losses in this design are
in the range of theoretical value in between 0.3% and 11%. The
MSC losses agreed using a value of 1.7%. the results of the third
model showed that static Var produced more active power than
mechanically switched capacitor. At the same time, the static
Var produced the highest reactive power at export cable.
Although the static Var models have performed better than
mechanically switched capacitors, in terms of monetary value
mechanically switched capacitors are better than static Var
compensators. The parameters of the design were given by
Siemens, where their supplier confirmed that initial costs
including operation and maintenance cost for mechanically
switched capacitor are lower compared to the transformer.