Most of this has been dealt with in the meantime, but such problems really do occur, but they're utterly blown out of proportion by the anti-renewables lobby.
> He said Germany could solve the problem by allowing its grid operators to turn off renewable sources at times of excess production, which is not currently possible under German law.
This is not a technical problem, but a legal one. And even the legal issue has at least 3 technical solutions, they're just negotiating over who should bear the cost of working around the legal situation.
https://www.google.com/search?q=germany+czech+grid+windfarm+...
Most of this has been dealt with in the meantime, but such problems really do occur, but they're utterly blown out of proportion by the anti-renewables lobby.