Page 105 - Handbook of Electrical Engineering

86 HANDBOOK OF ELECTRICAL ENGINEERING

Step 3. Derive the steady state conditions of the AVR for no load and full-load on the generator.

Step 3a) No load
From Figure 4.1 it can be seen that at no load V = 1.0. Assuming that the exciter is not saturated,

e e = V fd = V = 1.0, since at no load G g = 1.0

Let
V o = V at no load

Hence,
e e
e a = and V ref = e a + V o
G a
And so,
V o = G a (V ref − V o ) (4.3)

Step 3b) Full-load
From Figure 4.1 it can be seen that at full-load, V = 0.995, V fd = 2.7259 from equation (4.1) and
therefore G g = 0.365.
Again assume that the exciter is not saturated and so,

e e = V fd =|E|= 2.7259 pu

Let
V 1 = V at full-load

Hence,
e e
e a = and V ref = e a + V 1
G a
And so,

V 1 = G a G g (V ref − V 1 ) (4.4)

Step 4. Find V ref and G a
There are two equations, equations (4.3) and (4.4), containing two unknowns V ref and G a . Divide
(4.4) by V 1 and rearrange to give,

V ref
G a G g − G g = 1.0 (4.5)
V 1
In (4.3) the voltage V o = 1.0, and so,

G a (V ref − 1.0) = 1.0 (4.6)