Environmental Engineering Reference
In-Depth Information
D
p
-
˙
T
m
1
θ
1
θ
Js
s
-
T
e
Formulas
of
T
e
,
Q
,
e
Q
e
M
f
i
f
i
Figure 18.3
Electronic part of a synchronverter (without control)
circuit breaker can be adopted to interface with the grid. If a neutral line is needed, then the
strategies discussed in (Zhong
et al
. 2005a, 2006) and Part II to provide a neutral line without
affecting the control of the three-phase inverter can be used.
It is advantageous to assume that the field (rotor) winding of the synchronverter is fed by
an adjustable DC current source
i
f
instead of a voltage source
v
f
. In this case, the terminal
v
f
varies, but this is irrelevant. As long as
i
f
is constant, the generated voltage from
(18.4) is
voltage
˙
M
f
i
f
sin
e
=
θ
θ.
(18.8)
v
a
v
b
v
c
]
T
given in (18.3) should be the capacitor voltages, as
shown in Figure 18.2. The inductance
L
s
and resistance
R
s
of the inductor can be chosen to
represent the stator impedance of a synchronous generator. The switches in the inverter are
operated so that the average values of
e
a
,
e
b
and
e
c
over a switching period should be equal
to
e
given in (18.8), which can be achieved by the usual PWM technique. Also shown in
Figure 18.2 are three interfacing inductors
L
g
(with series resistance
R
g
) and a circuit breaker
to facilitate the synchronisation/connection with the grid.
The terminal voltages
v
=
[
18.2.2 Electronic Part
Define the generated real power
P
and reactive power
Q
(as seen from the inverter legs) as
P
=
i
,
e
and
Q
=
i
,
e
q
,
where
e
q
has the same amplitude as
e
but with a phase delayed from that of
e
by
2
,
i.e.
,
M
f
i
f
sin
θ
−
2
˙
˙
e
q
=
θ
=−
θ
M
f
i
f
cos
θ.
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