Wind power technology - Wind Power Integration: Connection and System Operational Aspects - page 82

3.6.2.5 Control of the generator-side converter
The operation of the generator and the power transferred from the generator to the
DC link are controlled by adjusting the magnitude and angle of the voltage at the
AC terminals of the generator-side converter. This can be achieved using the load
angle control technique where the internal voltage of the generator is the sending
source ( V S ff 0), and the generator-side converter is the receiving source ( V R ffd ). The
inductive reactance between these two sources is the synchronous reactance of the
generator, X gen , as shown in Figure 3.27.
The magnitude, V R , and angle, d , required at the terminals of the generator-side
converter are calculated using (3.29) and (3.30) as

P ref

S gen X gen
V S V R

d ¼ ð 3 : 31 Þ

Q ref

S gen X gen
V S

V R ¼ V S

ð 3 : 32 Þ

where P ref

S gen is the reference value of the active power that needs to be transferred
from the generator to the DC link, and Q ref
S gen

is the reference value for the reactive

power. The reference value P ref

S gen is obtained from the characteristic curve of the
machine for maximum power extraction for a given generator speed, w r . As the
generator has permanent magnets, it does not require magnetising current through
the stator, thus the reactive power reference value can be set to zero, Q ref

S gen ¼ 0 (i.e.
V S and V R are equal in magnitude). The implementation of this load angle control
scheme is illustrated in Figure 3.27.
The major advantage of the load angle control is its simplicity. However, as in
this technique the dynamics of the generator are not considered it may not be very

P S gen

V S ∠0 V R ∠ d

X gen

ref
S gen

P

Grid

ref
S gen

P X gen
V S V R

δ

PWM

δ =

V R (= V S )

V S

ref
S ge Q gen

V R = V S +

V S

ref
S gen

Q = 0

Figure 3.27 Load angle control of the grid-side converter