I think you may have confused ship propulsion system with ship electrical generation and usage.
The 055 DDGs use COGAG propulsion system, where 4x CGT-25M gas turbine engines provide ~27MW each (or ~108MW total) to propel the ship forward in water during full speed dash (30+ knots).
However, these gas turbine engines are only meant for the ship's propulsion, and is not connected to the shipboard electrical grid that powers everything else (i.e. radars, sensors, computing systems, weaponry etc etc). The latter is powered by a separate, yet-to-be-publicized number and models of diesel and/or gas turbine engines.
