The Dutch international was signed from German club Hamburg after the two clubs agreed to a deal earlier this week.
"I feel very good and for me it is the next step in my own career after three years in Germany," he told the club's official website.
"I hope to be successful here.
"The ideas and the planning behind this club are very hopeful and it's a new adventure so I'm delighted to be here right now.
"The stadium looks great and I think it can only be better when it's full of people.
"I'm looking forward to playing here and everybody knows that the Premier League is maybe the biggest competition in the world."