ABSTRACT:
This paper presents a control system based on a
repetitive controller to compensate for key power-quality disturbances, namely
voltage sag, harmonic voltages, and voltage imbalances, using a dynamic voltage
restorer (DVR). The control scheme deals with all three disturbances
simultaneously within a bandwidth. The control structure is quite simple and
yet very robust; it contains a feed forward term to improve the transient
response and a feedback term to enable zero error in steady state. The
well-developed graphical facilities available in PSCAD/EMTDC are used to carry out
all modeling aspects of the repetitive controller and test system. Simulation
results show that the control approach performs very effectively and yields
excellent voltage regulation.
KEYWORDS:
1.
Dynamic
voltage restorer (DVR)
2.
harmonic
distortion
3.
power quality
(PQ)
4.
repetitive
control
5.
voltage sag
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:
Fig.
1. Test system implemented in PSCAD/EMTDC.
CONCLUSION:
The use of dynamic
voltage restorers in PQ-related applications is increasing. The most popular
application has been on voltage sags amelioration but other voltage-squality
phenomena may also benefit from its use, provided that more robust control schemes
than the basic PI controller become available. A case in point is the so called
repetitive controller proposed in this paper, which has a fast transient
response and ensures zero error in steady state for any sinusoidal reference
input and for any sinusoidal disturbance whose frequencies are an integer
multiple of the fundamental frequency. To achieve this, the controller has been
provided with a feed forward term and feedback term. The design has been
carried out by studying the stability of the closed-loop system including
possible modeling errors, resulting in a controller which possesses very good
transient and steady-state performances for various kinds of disturbances.
A key feature of this
control scheme is its simplicity; only one controller is required to eliminate
three PQ disturbances, namely, voltage sags, harmonic voltages, and voltage
imbalances. The controller can be implemented by using either a stationary
reference frame or a rotating reference frame. In this paper, the highly
developed graphical facilities available in PSCAD/EMTDC have been used very
effectively to carry out all aspects of the system implementation.
Comprehensive simulation results using a simple but realistic test system show
that the repetitive controller and the DVR yield excellent voltage regulation,
thus screening a sensitive load point from upstream PQ disturbances.
REFERENCES:
[1]
M. H. J. Bollen, “What is power quality?,” Elect. Power Syst. Res., vol.
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[2]
J. G. Nielsen and F. Blaabjerg, “A detailed comparison of system topologies for
dynamic voltage restorers,” IEEE Trans. Ind. Appl., vol. 41, no. 5, pp.
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[3]
V. K. Ramachandaramurthy, A. Arulampalam, C. Fitzer, C. Zhan, M. Barnes, and N.
Jenkins, “Supervisory control of dynamic voltage restorers,” Proc. Inst.
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[4]
P. T. Nguyen and T. K. Saha, “Dynamic voltage restorer against balanced and
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[5]
M. H. J. Bollen, Understanding Power Quality Problems: Voltage Sags and
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