Environmental Engineering Reference
In-Depth Information
and the three-phase currents on the track side are
⎧
⎨
I
L
1
√
3
∠
I
a
=
0
,
I
L
1
√
3
∠
−
2
3
π,
I
b
=
(9.7)
⎩
I
L
1
√
3
∠
2
3
π.
I
c
=
The corresponding phasor diagrams are shown in Figure 9.4. In this case, the compensation
currents
⎧
⎨
I
L
1
√
3
∠
−
2
3
π,
I
ra
=
I
L
1
√
3
∠
I
rb
=
0
,
(9.8)
⎩
I
L
1
√
3
∠
2
3
π,
I
rc
=
are balanced but in the negative sequence, with the same amplitude as that of the currents on
the secondary side of the V/V transformer.
9.5 Simulation Results
Simulations were carried out in MATLAB
R
/Simulink
R
to verify the strategy. The solver used
was ode23tb with a maximum step size of 1
s.
The model of the high-speed train is shown in Figure 9.5. The turns ratio of the locomotive
transformer is 27.5:1.5 and the parameters are:
R
1
=
μ
0
.
5
,
L
1
=
1
.
5 mH,
C
1
=
1000
μ
F,
F to obtain a
power factor of 0.6. The parameters of the PI controller for the DC-bus voltage are
K
p
=
R
=
6
,
L
=
20 mH and
C
=
460
μ
F. The capacitor
C
1
is chosen as 1000
μ
0
.
1
and
K
i
=
0
.
005. The parameters of the traction power system are given in Table 9.1.
9.5.1 The Case when
cos
1
The THD of the load current was 30%. The system was started at 0 s and the SPC was turned
on at 0.08 s. The load current is shown in Figure 9.6(a) and the three-phase grid-side currents
are shown in Figure 9.6(b). It can be seen that the Phase-C current before compensation is 0.
In addition, there is a significant amount of harmonics in
i
A
and
i
B
. After compensation, the
three-phase grid currents are balanced and clean. Moreover, the amplitude of the grid currents
is reduced considerably. As shown in Figure 9.6(c), the DC-bus voltage was initially set at
4600 V and was maintained close to the reference voltage after the SPC was turned on. The
compensation currents generated by the three-phase converter are shown in Figure 9.6(d). The
THD of Phase-A current at the grid-side dropped from 30% to 1%, as shown in Figure 9.6(e)
and its zoomed version in Figure 9.6(f).
θ
=
9.5.2 The Case when
cos
1
In this case, the train model is changed to a purely resistive load of 5
θ
=
connected to the
locomotive transformer. The corresponding curves are shown in Figure 9.7 when the SPC was
turned on at 0.08 s. Similar performance was obtained.
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