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Friday, 15 May 2015

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

BLOCK DIAGRAM

 Fig.1. Schematic diagram of DVR.

Fig.2. Proposed Z source inverter topology.

SIMULATION RESULTS

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

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

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

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

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.