Environmental Engineering Reference
In-Depth Information
R
L
R
r
C
r
N
Figure 14.8
Model of non-linear loads
14.4.4.2 Regulation of the RMS Voltage
In order to address the third aspect, another loop is added to regulate the RMS value of the
phase voltages generated, as shown in Figure 14.6(d) or Figure 14.6(e). The controller takes
the form of a simple PI controller, with the RMS value of the phase voltage generated as
feedback. This makes sure that all three-phase voltages have the same RMS value even when
loaded. The output of the PI controller plays the role of the peak amplitude of the reference
phase voltage, which is multiplied with the phase information sin(
3
)
provided by the synchronisation unit shown in Figure 14.6(a) to form the reference phase
voltage
3
2
2
ω
t
−
) or sin(
ω
t
+
v
rb
or
v
rc
.
14.5 Simulation Results
Simulations were carried out in MATLAB
R
/Simulink
R
to verify the topology and the control
strategy. The solver used was ode23tb with a maximum step size of 1
s. Different simulations
with linear balanced loads and non-linear unbalanced loads were carried out. The model of
non-linear loads is shown in Figure 14.8 and the other parameters of the system are given in
Table 14.1. The band of the hysteresis controllers is 0.5 A and the
K
h
are 20
μ
,
10, 5 and 5,
respectively, for the 3rd, 5th, 7th and 9th harmonics.
K
i
=
4, the parameters of the PI controller
for the DC-link voltage are
K
P
=
.
,
=
0
8
K
I
10 and the parameters of the PI controller for
the RMS phase voltages are
K
P
=
16
,
K
I
=
248.
14.5.1 With Three-phase Linear Balanced Loads
In this simulation, the three-phase loads were linear and balanced, consisting of a resistor of
5
in series with an inductor of 10 mH for each phase. The simulation was started at 0 s with
the rectifier leg and the neutral leg turned on at 0.04 s and the phase legs turned on at 0.12 s,
respectively. The simulation results are shown in Figure 14.9.
Table 14.1
Parameters of the system
Parameters
Values
Supply voltage
220 V
L
s
and
L
r
1
.
5mH
L
1mH
C
20
μ
F
C
N
+
and
C
N
−
4000
μ
F
Initial DC-link voltage
600 V
DC-link voltage
800 V
Search WWH ::
Custom Search