What are the names of the sonic tv series?

Loads- There was:

Adventures of Sonic the Hedgehog
Sonic-X
Sonic Underground

And a few others I've seemed to misplace...

SatAM
AoStH
Sonic Underground
Sonic X
Those are the ones I know.

Sonic X is the Japanese anime and the most well-known StH show.
The Adventures of Sonic the Hedgehog was the first StH show which was made for the younger fans of Sonic.
Sonic the Hedgehog (commonly known as SatAM) was made around the same time as AoStH to appeal to the older fans of Sonic and introduced the characters now seen and used in the Archie Sonic comics.
Sonic Underground was another show made after SatAM was cancelled (and the rights to SatAM were more or less given to Archie Comics), this show introduced Sonic's siblings Manic and Sonia.
There was also an OVA made in Japan for StH, though it was released in the U.S as a film.

Hope this helps!

Adventure of Sonic the hedgehog
Sonic Underground
Sonic SatAM
Sonic X
And that's all.