ABSTRACT:
This
paper studies different energy transmission solutions for AC offshore wind
farms. This transmission of energy is based on AC submarine cables that present
a strong capacitive behavior. Therefore, an analysis is necessary to determine
transmission characteristics such as, the number of submarine cables, voltage
or rated power. For that purpose, three different transmission configurations
will be considered: unique HVAC, various HVAC and MVAC, combined with three
submarine cables of different characteristics. By using a design procedure, it
is shown that based on the electric characteristics provided by the manufacturer
of the submarine cable, it is possible to determine the most efficient energy
transmission solution, from the perspective of the submarine cable. Different
variables will be taken into account, including transmission current, active
power losses, the cost of the transmitted energy and the reactive power
compensation required. In addition, the consequences of the selected
transmission solution to other more general aspects of the wind farm such as,
necessity of the offshore platform or local inter turbine network are also
discussed.
KEYWORDS:
1.
Wind energy
2.
Transmission of electrical energy
3.
AC-cable
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAMS:
Fig.
2: General layout of MVAC offshore wind farm.
Fig.
3: General layout of offshore wind farm with multiple HVAC connections.
EXPECTED SIMULATION RESULTS:
Fig.
4: Module of the current through the submarine cable vs cable length. With
compensation at both ends (red) and onshore compensation (blue). a) 5x30MW-36kV
configuration. b) 150MW 150Kv
Fig.
5: Active power losses for 50km cable length, with compensation at both ends
(red) and onshore compensation (blue) a) 150MW-150kV, 2x75MW-87kV, 3x50MW-66kV
y 5x30MW-36kV configurations b) 150MW-220kV
Fig.
6: a) Rayleigh distribution for different average wind speeds b) Generated
power on wind farm on function of the wind speed.
Fig.
7: Energy transmission cost for different layouts.
CONCLUSION:
In
agreement with built wind farms, a MVAC transmission system is the best option
near to shore. This is because submarine cables are very expensive. With big
cable lengths the cables costs do not compensate the money saved in the
offshore platform. With short cable lengths (<20Km) MVAC connections are
better than other layouts. Moreover, at 150 MW rated power MVAC configuration
can be the best option to 60Km cable length. However in this case the clusters
are of (40-50MW) and the submarine cables operates at 70-80% (or more depending
the cable length) of their load capability. This can cause an inadmissible
voltage drop in the transmission system or other harmful effects. In this paper
only conduction losses in the submarine cables have been considered, armor
losses or dielectric losses have also not been taken into account. But this
simplification affect to cable parameterization and not to layout selection
procedure. 220kV HVAC system is not the best option for any cable length. But
the cable used in this evaluation has 3 times higher resistive component than
other cables.
REFERENCES:
[
1 ] S. Lundberg, "Wind farm configuration and energy efficiency studies
series DC versus AC layouts," Thesis, Chalmers University of Technology
2006.
[
2 ] S. Lundberg, "Evaluation of wind farm layouts," EPE Journal
(European Power Electronics and Drives Journal), vol. 16, pp. 14-20, 2006.
[
3 ] Å. Larsson, A. Petersson, N. Ullah, O. Carlson, “Krieger’s Flak Wind Farm”,
Nordic wind power conference, May 2006
[
4 ] S.D. Wright, A.L. Rogers, J.F. Manwell, A. Ellis, “Transmision options for
offshore wind farms in the united states,” AWEA 2002
[
5 ] S. Chondrogiannis, M. Barnes, “Technologies for integrating wind farms to
the grid (Intering report)”, DTI 2006.
