As a grid engineer, I find the Danish case to be somewhat unique because of their strong AC and DC interconnections to Germany and Sweden. Basically, they can free-ride on the large european grid (UCTE), which stretches from Portgual to Russia, to maintain network stability while increasing domestic wind penetrations above 50%.
I think a more interesting case study is Ireland, which has far weaker interconnectors to the UK and operate mainly as an island network. Like Denmark, they are also trying to integrate large amounts of wind (a goal of 40% by 2020, which is equivalent to over 6GW peak), but unlike Denmark, Ireland also have to deal with the resulting stability issues.
An EirGrid engineer I spoke to recently mentioned that frequency stability is already a big issue for them. The main solution proposed in a 2010 study [1] amounted to maintaining a sufficient operating inertial reserve, which would potentially mean curtailing wind generation at times. In the future, I would look to Ireland rather than Denmark for solutions to integrating more wind into the grid, because they are already at the pointy end of it.
I think a more interesting case study is Ireland, which has far weaker interconnectors to the UK and operate mainly as an island network. Like Denmark, they are also trying to integrate large amounts of wind (a goal of 40% by 2020, which is equivalent to over 6GW peak), but unlike Denmark, Ireland also have to deal with the resulting stability issues.
An EirGrid engineer I spoke to recently mentioned that frequency stability is already a big issue for them. The main solution proposed in a 2010 study [1] amounted to maintaining a sufficient operating inertial reserve, which would potentially mean curtailing wind generation at times. In the future, I would look to Ireland rather than Denmark for solutions to integrating more wind into the grid, because they are already at the pointy end of it.
[1] EirGrid Facilitation of Renewables study, http://www.eirgrid.com/renewables/facilitationofrenewables/