Most Helpful Member
So I thought to the varicap (varactor) which can be voltage-controlled by a micro (Arduino in my case) but these kind of components have a so low capacitance values (in the order of few pF) that this makes them useless for my purposes. Furthermore, in the presence of so high voltage peaks, they will be destroyed in microseconds!
They are available up to several hundred pF and 10s of kV rating. Have a look here: