It is known from the fact that Harmonic Distortion
is one of the main power quality problems frequently encountered by the
utilities. The harmonic problems in the power supply are caused by the
non-linear characteristic based loads. The presence of harmonics leads
to transformer heating, electromagnetic interference and solid state device
mal-functioning. Hence keeping in view of the above concern, research has been
carried out to mitigate harmonics. This paper presents an analysis and control
methods for hybrid active power filter using Discrete Pulse Width Modulation and
Space Vector Pulse Width Modulation (SVPWM) for Power Conditioning in
distribution systems. The Discrete PWM has the function of voltage stability,
and harmonic suppression. The reference current can be calculated by‘d-q’
transformation. In SVPWM technique, the Active Power Filter (APF) reference
voltage vector is generated instead of the reference current, and the desired
APF output voltage is generated by SVPWM. The THD will be decreased
significantly by SVPWM technique than the Discrete PWM technique based Hybrid
filters. Simulations are carried out for the two approaches by using MATLAB, it
is observed that the %THD has been improved from 1.79 to 1.61 by the SVPWM
technique.
KEYWORDS:
1.
Discrete PWM
Technique
2.
Hybrid Active
Power Filter
3.
Reference
Voltage Vector
4.
Space Vector
Pulse Width Modulation (SVPWM)
5.
Total Harmonic Distortion (THD)
6.
Voltage
Source Inverter (VSI)
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:
Figure 1. Configuration of an APF
using SVPWM
EXPECTED SIMULATION RESULTS:
Figure 2. Source current waveform
with hybrid filter
Figure 3. FFT analysis of source
current with hybrid filter
Figure 4. Simulation results of balanced linear
load
(a)
The phase-A supply voltage and load current waveforms
(b)
The phase-A supply voltage and supply current waveforms
Figure 5. Simulation results of unbalanced linear
load
(a)
Three-phase load current waveforms
(b)
Three-phase supply current waveforms
Figure 6. Simulation results of non-linear load
(a)
The three-phase source voltage waveforms
(b)
The three-phase load current waveforms
(c)
The three-phase source current waveforms
Figure 7. Harmonic spectrum of non-linear load
(a)
The phase-A load current harmonic spectrum
(b)
The phase-A source current harmonic spectrum
CONCLUSION:
In
this paper, a control methodology for the APF using Discrete PWM and SVPWM is
proposed.
These
methods require a few sensors, simple in algorithm and are able to compensate
harmonics and unbalanced loads. The performance of APF with these methods is
done in MATLAB/Simulink. The algorithm will be able to reduce the complexity of
the control circuitry. The harmonic spectrum under non-linear load conditions
shows that reduction of harmonics is better. Under unbalanced linear load, the
magnitude of three-phase source currents are made equal and also with balanced
linear load the voltage and current are made in phase with each other. The
simulation study of two level inverter is carried out using SVPWM because of
its better utilization of DC bus voltage more efficiently and generates less
harmonic distortion in three-phase voltage source inverter. This SVPWM control methodology
can be used with series APF to compensate power quality distortions. From the
simulated results of the filtering techniques, it is observed that Total
Harmonic Distortion is reduced to an extent by the SVPWM Hybrid filter when
compared to the Discrete PWM filtering technique i.e. from 1.78% to 1.61%.
REFERENCES:
[1]
EI-Habrouk. M, Darwish. M. K, Mehta. P, “Active Power Filters-A Rreview,”
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[2]
Akagi, H., “New Trends in Active Filters for Power Conditioning,” IEEE Trans.
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[3]
Singh.B, Al-Haddad.K, Chandra.A, “Review of Active Filters for Power Quality
Improvement,” IEEE Trans. Ind. Electron., Vol. 46, No. 5, Oct, 1999, pp.
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[4]
Ozdemir.E, Murat Kale, Sule Ozdemir, “Active Power Filters for Power
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