ABSTRACT:
Power
quality is an all-encompassing concept for a multitude of individual types of
power system disturbances. The presence of harmonics in power supply network
poses a severe power quality problem
that results in greater power losses in the distribution system, interference
problems in communication systems and, sometimes, in operation failures of
electronic equipment. Shunt active power filters are employed to suppress the
current harmonics and reduce the total harmonic distortion (THD). The voltage
source inverter (VSI) is the core of an active power filter. The hysteresis
current control is a method of controlling the VSI. Hysteresis control can be
either of fixed band type or adaptive band type. In this paper, Synchronous Reference
Frame (SRF) theory is implemented for the generation of reference current
signals for the controller. This paper investigates the effectiveness of the
proposed model in harmonics currents mitigation by simulating a model of a
three-phase three wire shunt active power filter based on adaptive hysteresis current
control and SRF theory. Simulation results indicate that the proposed active
power filter can restrain harmonics of electrical source current effectively
KEYWORDS:
1.
Synchronous
reference frame theory
2.
Adaptive
hysteresis control
3.
Harmonic
mitigation
4.
Shunt active
filter
5.
Voltage source
inverter
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:
Fig.
1. Reference Current Generation Block
Fig.
2. Nonlinear Load Currents
Fig.
3. Compensating APF Currents
Fig.4.Source
currents after compensation
Fig.5.
Harmonic analysis of source current with Adaptive Hysteresis Band
CONCLUSION:
In
the adaptive band hysteresis control, the switching frequency is nearly constant with respect to
the system parameters and defined switching frequency. However, at low switching
frequency case, the tracking is not as good as the one in high switching
frequency. Obviously, a decrease in switching frequency results in an increase
in the hysteresis bandwidth that causes the free operation of current error in
a wider range. This higher low-frequency
error, in turn, will lead to higher low order harmonics in the source current,
and hence higher THD. Based on the above facts, the switching frequency should
be kept as high as possible for better performances of adaptive band hysteresis
current control.
The
developed model has the following advantages:
(i)
Simplification of the power conversion
circuit can be achieved.
(ii)
(ii) Under the developed model, the
performance of control strategy can be effectively examined without long
simulation run time and convergence problem.
REFERENCES:
[I]
L. A Moran, J. W. Dixon, "Active Filters", Chapter 33 in "Power Electronics
Handbook", Academic Press, August 200 I, pp. 829-841.
[2]
IEEE Recommended Practices and Requirements for Harmonic Control in Electrical
Power Systems, IEEE Standard 519-1992, 1993
[3]
Singh, 8.; Chandra, A; AI-Haddad K. "Computer-Aided Modeling and Simulation
of Active Power Filters", Electric Power Components and Systems, 27: 11,
1227 -1241,1999
[4]
L. Moran, 1. Dixon, J. Espinoza, R. Wallace "Using Active Power Filters to
Improve Power Quality", 5th Brasilian Power Electronics Conference, COBEP'99,
19-23 September 1999, pp 501-511.
[5]
Massoud, AM. ; Finney, SJ.; Williams, B.W. "Review of harmonic current
extraction techniques for an active power filter", 11th International
Conference on Harmonics and Quality of Power, pp 154 - 159,12-15 Sept. 2004
