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Improved Active Power Filter Performance for Distribution Systems with Renewable Generation
P. Acufia*, L. Monin*, IEEE Fellow Member, M. Riverat, IEEE Member, J. Rodriguez t, IEEE Fellow Member, and J. Dixon+, IEEE Senior Member
Figure 5. Simulation waveforms for the proposed control scheme.
filter starts to operate at t = tl. At this time, the active
power filter injects an output current io to compensate
current harmonic components, current unbalanced, and
neutral current simultaneously. Compensated system cur
rents (is) show sinusoidal waveform, with low distortion
(T H D < 5%). At t = t2, a three-phase balanced load
change is introduced from 0.6 to 1.0 p.u. Compensated
system currents remain sinusoidal despite the change in
the load. Finally, at t = t3, a single-phase load change
is introduced in the phase u from 1.0 to 1.3 p.u. As
expected on the load side, a neutral current flows through
the fourth leg (iLn), but on the source side, no neutral
current is observed (isn). Simulated results show that
the proposed control scheme effectively eliminate current
unbalanced. Additionally, Fig. 5 shows that the DC
voltage remains constant through the whole active power
filter operation. Experimental results corroborate the successful oper
ation of the active filter shown in the simulations. The
dynamic performance of the active filter is tested under
balanced and unbalanced load conditions. Fig. 6 shows
the transient response when APF starts to operate. The
line current immediately becomes sinusoidal and the
capacitor-voltage behavior is as expected. The T H Di is reduced from 27.09% to 4.54%.
Tek JL • Acq Complete M Pos: O,OOOs
iLu ...
VVV
TRIGGER
Type
11m Source
I!il Slope
1m '.\J\J\J'vV a;.m Vdc Coupling -.pa:akt "Vill""� �,�! L. \t.; • �",. .\, f ,. .... 1 l J' II iii "'-CH1 50.0V CH2 SO.OV M 10.0ms Eit..r 312mV
CH3 SO.OV CH4 10.0V 10-Mar-12 03:25 <10Hz
Figure 6. Experimental transient response under APF connection.
In Fig. 7, the response of the series active filter under
load change is shown. The line current remains sinu
soidal and the capacitor voltage returns to its reference
in two cycles, with minimum variation when the load
changes. In this case, a step change is introduced from
0.6 to 1.0 p.u.
Tek JL
"'-
• Acq Complete M Pos: O,OOOs ...
TRIGGER
Type
11m Source
!iii Slope
1m Mode
WllIiIlI Coupling
IiI! CH1 50.0V CH2 SO.OV M 10.0ms
CH3 50.0V CH4 S.OOV 10-Mar-12 04:49
CH1 ..r 32.0V
<10Hz
Figure 7. Experimental results under balanced load change (0.6 to 1.0 p.u.)
In the last case, the phase u load was increased from
1348
1.0 to 1.3 p.u. The corresponding waveforms are shown
in Fig. 8. This figure shows that the active filter is able
to compensate current flow in the neutral wire and has
fast transient performance. Moreover, results show that
the four wire output current ion is effectively controlled,
and the neutral current of the system remains close to
zero even if a unbalance of 30% is applied.
Tek • Acq Complete M Pos: O.OOOs
Vsu I ( II'
TRIGGER
Type
m Source
!!iii Slope
IiII:IliE Mode
I1a Coupling
iii! CH1 50,OV CH2 50,OV M 10,Oms CH1 f 58,OV
CH3 50,OV CH4 50,OV 11-Mar-12 04:41 <10Hl
Figure 8. Experimental results under unbalanced phase u load change (1.0 to 1.3 p.u.)
VII. CONCLUSION
An improved dynamic compensation scheme for
power distribution systems with renewable generation
with a prediction time of one sample has been proposed
to improve the distribution system current quality. The
proposed predictive control algorithm has proved to be
good alternative for active power filter applications.
The advantages of the proposed control scheme re
lated with simplicity, modeling and implementation have
proved that predictive control schemes are a good alter
native to classical methods proposed previously. Sim
ulated and experimental results have shown that com
pensation effectiveness of the active power filter is well
achieved with predictive techniques.
ACKNOWLEDGMENT
The authors wish to thank the financial support from
the the Chilean Fund for Scientific and Technological
Development (FONDECYT) through project 11 10592 Basal Project FB0821.
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