I don't think the 50/60 Hz will make a big difference (if anything, less power is consumed at 50 Hz, e.g. with motors).
Especially since the power is converted to DC for most computer electronics.
However, voltage in Frankfurt is 240 V, not 220 V. That's about 10% more volts or 20% more power than your rating.
I'm looking at my transformers and just about everything that is "dual voltage" will handle 100-2409v, 50-60 Hz. Even a cell phone charger that I just noticed is good for 230v 50 Hz has been working happily on 117v, 60 Hz. Even stranger, some of the 110-120v transformers will take 50-60 Hz.