Control and Design of Microgrid Components - Power Systems ...

Inverter
V∠δ E∠δE
P,Q
v
X L
AC
Grid
δ = δ − δ
VE
P = sin( δp)
XL
δp
Q =
V 2
− VE cos( )
X
Figure 4.5 P and Q as a Function of the Voltages and their Angles.
p
v
E
L
The size of the inductor is derived from the inverter voltage ratings, the regulated bus voltage
and the limits on the power angle. The power angle is the angle difference between the voltages
at the inverter and the regulated bus. Typical limits can be:
- Limit on V (such as V max ≤ 12 . pu ). This condition is dictated by the value of the voltage at the
DC bus and by the kind of power electronic bridge used in the inverter.
- Limit on δ (such as δ
max
≤ 30 deg rees ). This condition derives from the need for the controller
to operate in the linear portion of the P( δ p ) characteristic: as Figure 4.6 shows, 30 degrees is a
reasonable choice for the maximum value for δ p .
Figure 4.6 Power-Angle Characteristic.
The power angle characteristic is already a great place to start to limit the size of the inductor,
because it provides some upper and lower boundaries for its value. If the value of the inductance
is too large, then the resulting angle at maximum power would not satisfy the condition of
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