I've tried both:
sudo add-apt-repository ppa:linrunner/tlp
sudo apt-get update
and
sudo apt-add-repository ppa:linrunner/tlp
sudo apt-get update
and I too get the error:
Cannot add PPA: 'ppa:linrunner/tlp'.
Please check that the PPA name or format is correct.
I believe this is because the server is having connectivity issues as when I try to visit the launchpad page https://launchpad.net/~linrunner/+archive/tlp in Firefox I get an error too:
Please try again
Sorry, there was a problem connecting to the Launchpad server.
Try reloading this page in a minute or two. If the problem persists, let us know in the #launchpad IRC channel on freenode.
Thanks for your patience.
My suggestion would be to try again later, or tomorrow.