ABSTRACT:
In this study a new method is proposed in order to improve
the harmonic suppression efficiency of Active Power Filter for the problems caused
by the distorted and unbalanced voltages with unbalanced load currents in
control strategy. The proposed control method gives an adequate compensating current
reference even for non ideal voltage and unbalanced current conditions. The
results of simulation study are presented to verify the effectiveness of the
proposed control technique in this study.
KEYWORDS:
1.
Active Power
Filter
2.
Park
Transformation
3.
Clark
Transformation
4.
Self Tuning Filter
5.
Unbalanced
Load Currents and Voltages
SOFTWARE: MATLAB/SIMULINK
Fig.
1. Block diagram of the APF
Fig.
2. Three phase unbalanced and distorted (non-ideal) grid voltage
Fig.
3. Unbalanced varying load current under non-ideal voltage condition.
Fig.
4. Voltage waveforms, a-) Three phase unbalanced and distorted grid voltages,
b-) Grid voltages after transformation to α-β ( at the input of STF),
c-) The obtained balanced and undistorted two phase voltage waveforms (at
the output of STF), d-) The obtained balanced and undistorted three phase
voltage waveforms (at the input of PLL).
Fig.
5. DC-link terminal voltage with the proposed control method
Fig.
6. Three phase converter currents
Fig.
7. Grid current after filtering by proposed control method under distorted and
un-balanced grid voltage with unbalanced load conditions
CONCLUSION:
In
this paper, we have considered to design a control method in order to generate
correct reference current signal to satisfy the requirements of harmonic
suppressing and reactive power compensation for the unbalanced nonlinear loads combination
under case of non-ideal grid voltage conditions. In the propose method, the distorted
and unbalanced voltages first processed by using Self Tuning Filter to
determine the correct angular positions. Then second STF is used to extract balanced
load current waveforms after obtaining the fundamental and harmonic components
of instantaneous currents by using park transformation. In this study, additional
low-pass or high-pass filter is not used to extract harmonic components from the
fundamental. The simulation studies shows that the proposed control technique
gives an adequate compensating current references.
REFERENCES
[1] W. M. Grady, S. Santoso,
"Understanding power system harmonics", IEEE Power Eng., Rev.
21, pp. 8-11.
[2]
B. Singh, K. Al-Haddad, K, A. Chandra, "A review of active filters for power
quality improvement", IEEE Transaction on Industrial Electronics.,
vol. 46, no. 5, pp. 960–971, 1999.
[3]
N. Mariun, A. Alam, S. Mahmod, H. Hizam, "Review of control strategies for
power quality conditioners", PECon 2004, Power and Energy Conference,
vol., no., pp. 109- 115, 29-30 Nov. 2004.
[4]
H. S. Song, “Control scheme for PWM converter and phase angle estimation
algorithm under voltage unbalance and/or sag condition”, Ph.D. thesis in
Electronic and Electrical Engineering. South Korea, 2000.
[5]
M. Abdusalam, P. Poure, S. Saadate, “A New Control Scheme of Hybrid Active
Filter Using Self-Tuning-Filter,” POWERENG 2007 International Conference on
Power Engineering, Energy and Electrical Drives, 2007, vol., no., pp.35-40,
12-14 April 2007.