Handbook of Electrical Engineering

GAS TURBINE DRIVEN GENERATORS 45

Figure 2.13 Basic control system block diagram of a gas turbine. The diagram represents the main elements
of the equation of motion.

fzi=frequency set-point of theithgovernor in Hz

Di=governor droop in per unit of theithgovernor

Pi=electrical load of theithgenerator in kW

Gi=electrical power rating of theithgenerator in kW

Transpose (2.62) to findPi,

Pi=(fzi−f)

Gi

Difo

( 2. 63 )

The total power demand P for n generators is,

P=

∑i=n

i= 1

Pi (2.64)

=

1

fo

∑i=n

i= 1

fziGi

Di

−

f

fo

∑i=n

i= 1

Gi

DI

(2.65)

Which is of the simple form,

P=a−bf (2.66)

where

a=

1

fo

∑i=n

i= 1

fziGi

Di

is a constant (2.67)