21-05-2013, 04:45 PM
Wind Power on the Swedish Island of Gotland
ABSTRACT
The aim of this article is to give an overview about the subjects that Gotlands Energi AB
(GEAB), as owner of the network, has been studding and are considered to be the most
important impacts for the grid operator. Some solution that has been implemented
describes, but the aim has not to go in to details. One of the most important experiences is
to have roles and clear responsibility border for the different parts in a deregulated marked.
In Sweden the owners of windmills mostly are independent producers.
The network consists on approx. 300 km 70 kV lines, 100 km 30 kV lines and 2.000 km 10
kV lines. Normally there is no local production except the Wind Power. The energy
turnover in the system is about 900 GWh and the peak load approx. 160 MW and the
minimum load is around 40 MW. About 37.000 customers are connected. Today, there are
160 windmills with total installed power of 90 MW producing more than 200 GWh.
Normally there is no local production except the Wind Power. The HVDC-Link transfers
power from the mainland and regulates the frequency on the island.
The amounts of installed wind power are high compared with the maximum power, energy
and the short cross circuit power in the system. With around 25% wind power energy in a
islanding system we can study system aspects and also more local aspects for the impact
from windmills.
With the relevant grid data and the power flow from the windmills and loads it is possible
to anticipate the impact in real time. During measurements it has been notes that the 3P
disturbances synchronize for several windmills connected to the same 10 kV system.
Possible flicker problems have been solved with power electronics in several places. The
first project for this kind of solution was the offshore wind park Bokstigen.
For the system aspects the fault situations are more sensitive. The asynchronous generators
and capacitor banks give a big transient fault current in a very short time. After 100 to 200
msec the generator absorb reactive power. That must be considered in the selective plans
for the relay protections.