Grounding when you're outdoors

So, I'm wondering, is it possible to use one of those power station things (example of what I'm thinking of is the Anker Solix F2000 power station) to provide power to your theremin and your amp? I ask because I know the theremin needs to be grounded and I don't want to waste money on a power station if I'm not going to be able to use it to play away from a regular power outlet.

Take a look at those threads :

http://www.thereminworld.com/Forums/T/31304/self-powered-amp-speaker-for-busking-with-theremin

http://www.thereminworld.com/Forums/T/32116/amp-for-street-performance-problems