In this paper, a five-level inverter is
used as a shunt active power filter (APF), taking advantages of the multilevel inverter
such as low harmonic distortion and reduced switching losses. It is used to
compensate reactive power and eliminate harmonics drawn from a diode rectifier
feeding a RL load under distorted voltage conditions. The active power filter
control strategy is based on the use of self tuning filters (STF) for reference
current generation and a fuzzy logic current controller. The use of STF instead
of classical extraction filters allows extracting directly the voltage and current
fundamental components in the a-J3 axis without phase locked loop (PLL). This
study is divided in two parts. The first one deals with the harmonic isolator
which generates the harmonic reference currents. The second part focuses on the
generation of the switching pattern of the inverter by using a fuzzy logic controller
applied and extended to a five level shunt APF. The MA TLAB Fuzzy Logic Toolbox
is used for implementing the fuzzy logic control algorithm. The obtained
results show that, the proposed shunt active power filter controller has
produced a sinusoidal supply current with low harmonic distortion and in phase
with the line voltage.
KEYWORDS:
1.
Active filter
2.
Harmonics isolator
3.
Distorted voltage conditions
4.
Self-tuning filter
5.
Fuzzy logic control and PWM control
SOFTWARE: MATLAB/SIMULINK
CIRCUIT DIAGRAM:
Fig1.power
system configuration
EXPECTED SIMULATION RESULTS:
Fig.
2. Supply voltage Vs waveform
Fig.
3. Supply current Is waveform without filtering.
Fig.
4. Supply current Is waveform with filter.
Fig.
5. Active filter current If
Figure
6. APF output voltage Vab (line to line) for a five-level with
PDPWM
Fig.
7. DC voltage of the condensers Vdc
CONCLUSION:
This paper has discussed the control and
performance improvement of a shunt active power filter under distorted voltage
conditions, using a fuzzy logic controller for a five level shunt active power
filter based on the optimization of the reference current generation and using
a modified version of the p-q theory and PDPWM to generate switching signals. Simulation
results have shown high performances in reducing harmonics and power factor
correction. The use of the Self-tuning filter leads to satisfactory
improvements since it perfectly extracts the harmonic currents under distorted conditions.
With the fuzzy logic control, the active filter can be adapted easily to more
severe constraints, such as unbalanced conditions. In addition, results have
demonstrated the major advantages of using STF and fuzzy logic controller in
filter control. The Five-level APF provides numerous advantages such as
improvement of supply current waveform, less harmonic distortion and
possibilities to use it in high power applications. As final conclusion, the
obtained results showed that, the proposed active power filter controller have
provided a sinusoidal supply current with low harmonic distortion and in phase
with the line voltage.
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