A
system (1) for transforming a variable output into an input having a desired speed value, including a transmission (30) receiving the output having a first speed (Ve) and producing the input having a second speed (Vgen), first, second and third sensors (12,10,7) producing data (39,32,37) corresponding to the first speed (Ve), second speed (Vgen) and a
power demand (Pdem) for the input, a ratio
set point controller (34), a ratio controller (36) and a speed controller (4). The ratio
set point controller (34) receives the data (39,32,37) and calculates an available power (Pav), a stability level of the
system (S,U1,U2), a desired value for the first speed (Ve), and a desired value and rate of change for the
transmission ratio. The ratio controller (36) interfaces the ratio
set point controller (34) and actuates the transmission (30) to change the
transmission ratio to the desired value following the desired rate of change. The speed controller (4) changes the first speed (Ve) until the second speed (Vgen) corresponds to the desired speed value.