Pot experiment was conducted at the Botanical Garden of the Department of Biological Science, Usmanu Danfodiyo University, Sokoto Nigeria, during the 2013 dry season. The main objective of this research was to determine the effect of water stress and variety on productivity of rice (Oryza sativa) at Sokoto. The treatment consisted of water stress at three growth stages (Tillering, flowering, Grain filling) and unstress (control) and three rice varieties (FARO 44, NERICA 2 and FARO 15) laid out in a Completely Randomised Design (CRD) replicated three times. The result indicated that water stress significantly (P < 0.05) resulted to decreased in plant height, number of leaves per plant, total biomass, harvest index and grain yield. The results indicated significant (P < 0.05) differences among genotypes. Faro 44 differed significant from in plant height, number of leaves per plant, total biomass, harvest index and grain yield. FARO 44 differed significantly from NERICA 2 and FARO 15 at all the parameters under study. Water is very vital as far as rice production is concern should be applied at every stage of rice production. FARO 44 is recommended for the area for higher yield.
Multi-level converters are every day attracting research interest due to it tremendous positive contributions they are making in the power industries. The converter has put hope in the minds of power electronic engineers that a time will come when it will break a record by providing an efficient means of utilizing the abundant renewable energy resources.<strong> </strong>The paper presents a review of multilevel voltage source converters that are widely being used in engineering applications. It reports the technological advancements in converter topologies of Flying Capacitor (FC), Neutral Point (NPC) /Diode Clamped, and Cascaded H-Bridge (CHB) with their respective advantages and disadvantages. Recent customized/hybrid topologies of the three-phase multilevel inverter with reduced component count and switching combination are reported. The paper also reviewed different modulation techniques such as the multilevel converter carrier base PWM, Space Vector Modulation techniques (SVM), and Selective Harmonic Elimination method (SHE-PWM). Finally, various multilevel converters areas of application were highlighted. This review will expose the reader to the latest developments made in the multi-level topologies, modulation techniques, and applications.
The paper presents a 5-level cascaded H-bridge voltage source inverter. The converter topology composed of two-cascaded H-bridge modules connected in parallel and powered by a single DC source. The benefit of this topology in comparison with the conventional H-Bridge configuration is that it uses single input DC source instead of two to achieve the same output steps/levels. Selective Harmonic Elimination (SHE) is the modulation technique employed. The generated non-linear transcendental equations are solved using an optimised Genetic algorithms to find the switching angles. This property makes the topology and the control function suitable for three phase applications where triplen harmonics are said to cancel out at the line-to-line voltages. This concept of SHE modulation extends the value of the filter cut-off frequency, which translates to smaller sized filter, compact cooling system and reduced system weight. This advantage makes the topology attractive to automotive and renewable energy applications. The topology was simulated using PSIM software.
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