Modern industrial equipments are more sensitive to power quality problems such as voltage sag, voltage swells, interruption, harmonic, flickers and impulse transient. Failures due to such disturbances create high impact on production cost. So nowadays high quality power is became basic needs of highly automated industries This paper deals with modeling and simulation technique of a Dynamic Voltage Restore (DVR).The DVR is a dynamic solution for protection of critical loads from voltage sags/swells. The DVR restores constant load voltage and voltage wave form by injecting an appropriate voltage. Present novel structure improves power quality by compensating voltage sag and voltage swells. This control scheme provides superior performance compared to conventional control methods because it directly measurers the rms voltage at the load point without involving any transformation process. A new topology based on Z-source inverter is presented in order to enhance the voltage restoration property of dynamic voltage restorer. Z-source inverter would ensure a constant DC voltage across the DC-link during the process of voltage compensation. The modeling of Z-source based dynamic voltage restorer is carried out component wise and their performances are analyzed using MATLAB software.

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Implementation of Z-Source Based Dynamic Voltage
Restorer for the Mitigation of Voltage Sag /Swell
ABSTRACT: Modern industrial equipments are more sensitive to power quality problems
such as voltage sag, voltage swells, interruption, harmonic, flickers and impulse transient.
Failures due to such disturbances create high impact on production cost. So nowadays high
quality power is became basic needs of highly automated industries This paper deals with
modeling and simulation technique of a Dynamic Voltage Restore (DVR).The DVR is a dynamic
solution for protection of critical loads from voltage sags/swells. The DVR restores constant load
voltage and voltage wave form by injecting an appropriate voltage. Present novel structure
improves power quality by compensating voltage sag and voltage swells. This control scheme
provides superior performance compared to conventional control methods because it directly
measurers the rms voltage at the load point without involving any transformation process. A new
topology based on Z-source inverter is presented in order to enhance the voltage restoration
property of dynamic voltage restorer. Z-source inverter would ensure a constant DC voltage
across the DC-link during the process of voltage compensation. The modeling of Z-source based
dynamic voltage restorer is carried out component wise and their performances are analyzed
using MATLAB software.
KEYWORDS:
1. Point Of Common Coupling (PCC)
2. Dynamic Voltage Restorer (DVR)
3. Active Power Filter (APF)
SOFTWARE:MATLAB/SIMULINK

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BLOCK DIAGRAM
Fig.1. Schematic diagram of DVR.
Fig.2. Proposed Z source inverter topology.

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SIMULATION RESULTS
Fig.3. Simulation waveform of DVR based system when sag occurred.

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Fig.4. Simulation waveform of DVR based system when swell occurred.

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Fig.5. Simulation waveform of DVR based system when sag/swell occurred.

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Fig.6. Simulation waveform of DVR based system when connected to Z-source inverter.

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CONCLUSION
Simulation of Z-source DVR for Power Quality Improvement is one of the techniques to
improve the power quality by using Z-source DVR. This project has presented a discrete PWM
control scheme for Dynamic Voltage Restorer to improve the system response and injection
capability for the mitigation of voltage sag/swell. As opposed to fundamental frequency
switching schemes already available in the MATLAB/SIMULINK, this PWM control scheme
requires only rms value of the voltage.
REFERENCES
[1] M.H.J Bollen „Understanding Power Quality Problems : Voltage sag and Interruptions” New
York IEEE Press ,1999.
[2] J.C. smith J.Lamoree ,P.Vinett,T.Duffy M.Klein “The impact of voltage sag Industrial plant
load” International Conference Power quality end use application and perspective pp171-178.
[3] Akagi H,”New trends in active filters for power conditioning” IEEE Transaction
Ind.Application,vol 32 pp 1312-1322 Nov/Dec 1996.
[4] Ghosh A and Ledwich G (2002) “Power quality Enhancement using Custom Power
Devices”.Kluwr Academics publishers, United States.
[5] O. Anaya-Lara, E. Acha, “Modeling and Analysis of Custom Power Systems by
PSCAD/EMTDC,” IEEE Trans., Power Delivery, PWDR vol-17 (1), pp. 266-272, 2002.