11 months ago


PAGE 24 Ahmed Mirdad

PAGE 24 Ahmed Mirdad Khan Success Stories with Gradate Students Ahmed Khan is an MSc Student at Electrical Engineering, won the best thesis award in the academic year 2015/2016. His thesis title was “Transformerless Microinverter with Low Leakage Current Circulation and Low Input Capacitance Requirement for PV Applications” under the supervision of Prof. Lazhar Ben -Brahim and Prof. Adel Gastli. He has published two journal papers from the result of his thesis in the high prestige journals “Renewable and Sustainable Energy Reviews” (impact factor of 8.05) and “Electric Power Systems Research” (impact factor of 2.688). Thesis Summary: The inevitable depletion of limited fossil fuels combined with their harmful footprint on the environment led to a global pursuit for alternative ener- gy sources that are clean and inexhaustible. Renewable energies such as wind, biomass and solar are the best alternative energy candidates, with the latter being more suitable for GCC countries. Furthermore, recent advances in PV technology, especially grid-connected PV systems revealed the preeminence of using multiple small inverters called (Microinverters) over using the conventional single inverter configuration. Specifically, the break-even cost point can be reached faster and the system modularity increases with microinverters usage. Nonetheless, due to microinverter’s small ratings designers prefer transformerless designs because transformer removal achieves higher efficiency and power density. The objective of his thesis was to design an efficient transformerless microinverter that has low leak- age current circulation and low input capacitance requirement with a minimum number of active switches. In other words, the objective was to increase the safety and the reliability of the system while maintaining the high efficiency. Eventually, the configuration selected is the transformerless differential buck microinverter with LCL filter and it is modeled with passive resonance damping and active resonance damping control. Publications: 1) Khan, L. Ben-Brahim, A. Gastli, M. Benammar, “Review and simulation of leakage current in transformerlessmicroinverters for PV applications”, Renewable and Sustainable Energy Reviews, Vol. 74, July 2017, pp. 1240-1256 2) A. Khan, A. Gastli, L. Ben-Brahim, “Modeling and control for new LLCL filter based grid- tied pv inverters with active power decoupling and active resonance damping capabilities”, Electric Power Systems Research , Vol. 155, February 2018, pp. 307-319 Ahmad Anad Abduallah Ahmad Anad Abduallah got his MSc. at Electrical Engineering Department in Spring 2015 with GPA 3.93/4.00. His Master thesis was about vector modulation techniques for five-phase quasi Z-source inverters under supervision of Dr. Atif Iqbal. As the result of his thesis, he published one journal paper and two conference papers. He got the PhD admission and Dean scholarship from the University of Liverpool John Moores and started his PhD study at this university on Fall 2016. He is working with the Machines and Drives group led by Professor Emil Levi which is one of the strongest research groups in Europe in the field of multiphase machines. Thesis Summary: Impedance source and quasiimpedance source inverters have gained popularity due to their capabilities of inverting and boosting in a single stage. Impedance source and quasi- impedance source inverters have additional switching states when compared to a traditional voltage source inverter (VSI), known as shoot-through (same leg switches are conducting simultaneously) state, that causes the boosting of the source voltage. The shoot-through states are not allowed in a standard VSI since this short circuits the DC source. This is an attractive feature as the inverter can handle wide voltage variation of the DC input source. This thesis proposes space vector pulse width modulation (SVPWM) techniques to control a five-phase two-level impedance source inverter that is equally applicable to quasiimpedance source inverter. Unlike the three-phase twolevel impedance source inverter, the application of the shootthrough technique to five-phase two-level impedance inverter is more complex and offers several switch combination redundancies which gives certain degrees of freedom to generate AC output voltage. Depending on the placement of the shoot-through period in each switching period, various SVPWM techniques are proposed. Each technique offers different voltage stresses on the switches and outputs voltage waveforms with different boosting factors and Total Harmonic Distortion (THD). A thorough comparative study, of the proposed SVPWM techniques, is carried out based on various obtained characteristics such as the boosting gain ratio, THD and DC link voltage ripples. Simulation results are validated using experimental approaches. Publications: Ahmad A. Abduallah, M. Meraj, M. Al-Hitmi, A. Iqbal, “Space Vector Pulse Width Modulation Control Techniques for A Five-Phase Quasi Impedance Source Inverter”, IET Electric Power Applications, to appear. EED NEWSLETTER VOL. 2, ISSUE 1

VOLUME 1, ISSUE 1 PAGE 25 Gradate Students’ Statistics EED NEWSLETTER VOL. 2, ISSUE 1

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