Autosynchronization of Hydro Plant

I am not an expert on this, but since no one else has chimed in yet, I will make a suggestion. Gensets are typically higher speed, lower mass, with lower rotational inertia. They, along with their governors, are thus quick in responding to load variations (short time constant). On the other hand, hydro turbines are slower, heavier, and higher in rotational inertia. Thus they will not react so quickly to load changes (longer time constant). This will affect the tuning of control loops.

The hydro plant has this butterfly valve and a vertical motor to open and close the water. In our design the pulse width for raise and lower frequency is same assuming the system is linear, it worked fine with gas turbine but in hydro the motor does more work to close the gate against water and less work to open so for the same pulse width ,the change in speed is different for raise and lower.
2. Is this the way all Hydro plant works with different characteristics for raise and lower? This plant is 87 years old with old system.

It sounds as though the speed of whatever drives the valve is influenced by the load. What type of drive system is it?

Can you set different pulse rates/widths for opening versus closing?

Interesting problem. I'm not too familiar with hydro specifics, so this is all conceptual generalities from me.