Status of Proof of Stake Implementation?

I’m an undergraduate student working on an independent study on blockchain. I’ll be comparing different consensus algorithms from both a theoretical and an experimental perspective. I’d like to use Cardano as a Proof of Stake coin. (I’ll also be studying Proof of Work, Proof of Importance, and Proof of Space). From a theoretical perspective, Cardano is perfect for this. Having an in-depth breakdown of the project handed to me in the form of the Oroborous paper makes theoretical analysis easy. However, if Cardano does not yet have a Proof of Stake implementation, I can’t really do any experimental evaluation.

What is the current status? The goal of Shelley seems to be decentralization, but are Cardano transactions currently verified via Proof of Stake on a small set of centralized servers? If I should be looking at other coins instead, which coins do you feel have pulled off Proof of Stake well? Ethereum Casper, which is also Proof of Stake, hasn’t been released yet. Thank you!

Also, If this post belongs in a different category please let me know.

Shelley is supposed to be out with POS Q2 2018. I’m not sure about the current implementation.

I think NEO is probably the biggest coin currently using POS successfully. I’ve personally also used POS with Experience Points and thought it worked well. I believe Qtum, Stratis, and Waves are some other notable coins using POS.

For the delegated version of POS (DPOS), which is more similar to Cardano, EOS, Lisk, and Ark are some notable examples. Although Lisk has gotten a lot of criticism for its implementation creating delegate “cartels”.