Environmental Engineering Reference
In-Depth Information
5
5
i
ref
i
a
i
ref
i
a
2.5
2.5
0
0
−2.5
−2.5
−5
−5
1.5
1.5
e
i
e
i
1
1
0.5
0.5
0
0
−0.5
−0.5
−1
−1
−1.5
−1.5
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
Time [s]
Time [s]
(a) Grid output current
, its reference
and current tracking error
5
5
THD of i
a
=5.46%
THD of i
a
=5.79%
4
4
3
3
2
2
1
1
0
0
0
5
10
15
20
25
30
0
5
10
15
20
25
30
Harmonics order
Harmonics order
(b) Spectra of the grid output current
Figure 16.6
Experimental results for a PR controller with a resistive local load implemented in the
αβ
frame (left column) and in the
abc
frame (right column)
implementation in the
frame and in the right column of Figure 16.5 for the implementation
in the
abc
frame. The recorded current THD, shown in Figure 16.5(b), was 3
αβ
.
84% (right) in
the
abc
frame compared to 4
frame (left). Both the tracking performance and
the recorded current THD in the
abc
frame were better than that in the
.
14% in the
αβ
αβ
frame.
16.4.1.2 With a Resistive Load
In this experiment a balanced resistive local load with
R
A
=
was connected
to the system. The grid current reference
I
d
was set at 2 A, after connecting the inverter to
the grid. The reactive power was set at 0 Var (
I
q
R
B
=
R
C
=
12
0), which corresponds to the unity power
factor. The grid current output
i
a
and its spectra, the reference current
i
ref
and the current
tracking error
e
i
are shown in the left column of Figure 16.6 for the implementation in the
=
αβ
frame and in the right column of Figure 16.6 for the implementation in the
abc
frame. The
PR controller implemented in the
abc
frame again demonstrated better tracking performance,
although with a higher THD due to the increased 3
rd
harmonics.
16.4.1.3 With an Unbalanced Load
In this experiment, an unbalanced resistive local load with
R
A
=
12
,
R
B
=∞
and
R
C
=
was connected to the system. The grid output current reference
I
d
was set at 2 A (after
connecting the inverter to the grid) and the reactive power was set at 0 Var (
I
q
12
=
0). The output
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