ABSTRACT:
Voltage sag is the most common and severe
power quality problem in the recent times due to its detrimental effects on
modern sensitive equipment. Generally, direct-on-line starting of the
three-phase induction motor (IM) and various kinds of short circuit fault are
directly responsible for this event. This study investigates the impacts of
starting and stopping of two threephase IMs on the load voltage profile. To be
more critical, two three-phase short circuit faults and one unsymmetrical fault
are also simulated in the same network at different instants of time. A simple
control algorithm of a real power optimised dynamic voltage restorer (DVR) with
a reduced power factor strategy is presented to protect the sensitive load from
these types of detrimental events. A novel fuzzy-proportional–integral based
self-tuned control methodology is implemented in the proposed work to
compensate the loss in the DVR circuit as well as to regulate the load voltage
and the direct current link voltage. The results show the effectiveness of the
adopted control scheme in DVR application to mitigate the voltage sag.
SOFTWARE: MATLAB/SIMULINK
DIAGRAM:
Fig. 1 Investigated distributed test system with DVR
EXPECTED SIMULATION RESULTS:
Figure
2. Voltage profile of load and DVR (a)
Without DVR, (b) DVR voltage, (c) With DVR, (d) DC voltage
Figure
3 Torque profile of IMs (a) Motor 1without DVR, (b) Motor 2 without DVR, (c) Motor 1 with DVR, (d) Motor 2 with DVR
Figure 4. Pertaining to unsymmetrical fault (a) Load voltage without DVR, (b) DVR voltage, (c) Load
voltage with DVR
Figure
5. Active DVR power profile pertaining to (a) In-phase compensation, (b) Present technique
CONCLUSION:
This study divulges a simple yet
robust reduced power factor controlled energy optimised algorithm in DVR to
offer a common solution to mitigate the severe voltage sag. Minimisation of
energy delivered may increase the life of the ESU, therefore limits the expenditure
indirectly. The self-tuned fuzzy-PI scheme also plays a significant role to
regulate the active power through the DVR as well as to compensate the load
voltage and DVR losses. The results obtained in this work shows that the
proposed DVR solution provides a good and satisfactory level of compensation.
The system voltage has been compensated nearly up to its nominal value. The DC
voltage is also very fairly regulated. The application of DVR reduces the level
of oscillation in the torque profile of the IM. The proposed method is also
compared with other strategies surfaced in the existing literature and it is unfold
that the proposed strategy offers better harmonic compensation and it also
provides better damping in the load voltage. Thus, it may be concluded that the
proposed control technique of DVR, operated by adaptive fuzzy control scheme,
may be justified for utilising the same as a common sag mitigating device. Within
the context of the present study, the work is ended with simulation only.
However, the same may be tested on an experimental bench.
REFERENCES:
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J.J.G., Lopez-Rodriguez, M.A., et al.: ‘Improvement of power quality
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[3] Bollen, M.H.J.: ‘Understanding power
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[4] Honrubia-Escribano, A.,
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