ABSTRACT:
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, Space Vector
4.
Pulse Width Modulation (SVPWM)
5.
Total Harmonic Distortion (THD)
6.
Voltage Source Inverter (VSI).
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:
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,”
Proc.IEE-Elec. Power Applicat., Vol. 147, no. 5, Sept. 2000, pp. 403-413.
[2]
Akagi, H., “New Trends in Active Filters for Power Conditioning,” IEEE Trans.
on Industry applications, Vol. 32, No. 6, Nov-Dec, 1996, pp. 1312-1322.
[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. 960-971.
