The Aquamarin, Bernstein und Citrinm sites are in the early stages of development, and planning approval is yet to be received.
PNE said it will develop the acquired projects through the permitting process and up to the point where they are ready to start construction.
The company will pay EUR 17 million upon completion of the purchase agreement which is dependent of "various closing conditions" the developer said.
Additional payments, which could come to significantly more than the first payment, will be paid as the projects reach defined points in their development.
Current plans allow for up to 240 wind turbines with 5MW of nominal capacity to be built across the three projects.
"We have demonstrated with the Borkum Riffgrund and Gode Wind projects that we can successfully develop and sell offshore wind farm projects," said Thorsten Fastenau, head of offshore at PNE.