There cant be. In practice if the generator isn't being fed enough torque, its phase lags and the grid drives the generator!
Its very simple. You run your generator with no load. match the phases and connect to the grid. The generator is now locked to the grid as surely as any other synchronous motor is.
Then when you push the steam into the turbines all that happens is that the current rises and the phase advances slightly. Very slightly.
Don't think you really understand how it works.