High gain non-isolated DC-DC converter topologies for energy conversion systems

PhD ThesisEmerging applications driven by low voltage level power sources, such as photovoltaics, batteries and fuel cells require static power converters for appropriate energy conversion and conditioning to supply the requirements of the load system. Increasingly, for applications such as grid connected inverters, uninterruptible power supplies (UPS), and electric vehicles (EV), the performance of a high efficiency high static gain power converter is of critical importance to the overall system. Theoretically, the conventional boost and buck-boost converters are the simplest non-isolated topologies for voltage step-up. However, these converters typically operate under extreme duty ratio, and severe output diode reverse recovery related losses to achieve high voltage gain. This thesis presents derivation, analysis and design issues of advanced high step-up topologies with coupled inductor and voltage gain extension cell. The proposed innovative solution can achieve significant performance improvement compared to the recently proposed state of the art topologies. Two unique topologies employing coupled inductor and voltage gain extension cell are proposed. Power converters utilising coupled inductors traditionally require a clamp circuit to limit the switch voltage excursion. Firstly, a simple low-cost, high step-up converters employing active and passive clamp scheme is proposed. Performance comparison of the clamps circuits shows that the active clamp solution can achieve higher efficiency over the passive solution. Secondly, the primary detriment of increasing the power level of a coupled inductor based converters is high current ripple due to coupled inductor operation. It is normal to interleaved DC-DC converters to share the input current, minimize the current ripple and increase the power density. This thesis presents an input parallel output series converter integrating coupled inductors and switched capacitor demonstrating high static gain. Steady state analysis of the converter is presented to determine the power flow equations. Dynamic analysis is performed to design a closed loop controller to regulate the output voltage of the interleaved converter. The design procedure of the high step-up converters is explained, simulation and experimental results of the laboratory prototypes are presented. The experimental results obtained via a 250 W single phase converter and that of a 500 W interleaved converter prototypes; validate both the theory and operational characteristics of each power converter.Petroleum Technology Development Fund (PTDF) Nigeri

Pharmacological Activities of Banana

Plants have been in use in traditional medicine since antiquity, and many active metabolic products with biological significance are obtained from them. Recently, pharmaceutical industries have developed great interest in utilizing these products as an alternative to the chemically synthesized drugs. This is due to the discovery of important new medicines from the plants, because of studies on how people of different background use plants as cure and treatment for many diseases, and side effects of the synthesized drugs. Banana, an eatable fruit produced by some herbaceous flowering plants of the genus Musa, is one of the valuable fruits with proven pharmacological potentials. Bananas are spread almost all over the world. Different chemical constituents like apigenin glycosides, myricetin-3-O-rutinoside, kaempferol-3-O-rutinoside, dopamine, and serotonin have been reported in different parts and varieties of banana. The presence of carbohydrate, proteins as well as flavonoids, makes bananas useful in both nutrition and therapeutics. Pharmacologically, bananas have been shown to possess antiulcer, antimicrobial, and antioxidant activities. This chapter discusses the essential information on banana, including its varieties, distribution, pharmacological actions, and its relevance in pharmaceutical industries. This will be beneficial for researchers to further harness the robustness of this fruit in controlling many diseases and modification of drugs

High step-up interleaved boost converter utilising stacked half-bridge rectifier configuration

This paper proposes a solution to complement the insufficient voltage gain and voltage stress distribution of classical interleaved boost converter in high step-up application. An interleaved converter integrating coupled inductor and voltage multiplier cell, which provides an additional voltage gain is proposed. By stacking the secondary side of the interleaved coupled inductor to its primary side, a high step-up voltage gain and distributed voltage stress are realised. Low-voltage rated devices ultimately reduce the conduction losses. The principle of operation and the performance characteristic of the converter are presented and verified by an experimental prototype of 140 W, 12 V input, and 120 V output

A Review on the Incidence, Interaction, and Future Perspective on Zika Virus

Zika virus (ZIKV) belongs to the family Flaviviridae and genus Flavivirus. It is a single‑stranded positive‑sense ribonucleic acid (RNA) virus, has its origin traced to Zika forest in Uganda. Its infection leads to ZIKV fever, characterized by arthralgia, myalgia, rash, conjunctivitis, and asthenia. Clinical presentation of the infection is nonspecific and may often be confused with symptoms of other flaviviral diseases (dengue, West Nile [WN], and chikungunya). Recently, ZIKV has been associated with congenital malformations and neurological complications such as microcephaly and Guillain–Barre’ syndrome. The viral tropism revealed an infection of the skin fibroblasts, keratinocytes, and immature dendritic cells through enhanced expression of dendritic cell‑specific intracellular adhesion molecule 3‑grabbing nonintegrin or anexelecto (Greekword: 'uncontrolled’) and tyrosine protein kinase receptor 3 systems. Silencing of T‑cell immunoglobulin (Ig) and mucin domain 1 (TIM‑1) and AXL RNAs has shown blockage of viral entry through their anti‑TIM‑1 and anti‑AXL antibodies, hence serving as a potential target for ZIKV drug development.Biotechnological approaches targeted toward ZIKV vector control include the development of transgenic mosquitoes to disrupt the genome pool of wild strains and use of an endosymbiotic bacterium to prevent replication of arboviruses within its vector. Other approaches include the use of gene drive and exploration of the genetic redundancy to disrupt the receptors used by the virus to gain entry into its host. It is also imperative to explore the modality through which neutralizing antibodies block this viral infection as this may prove as a potential target to arrest the viral life cycle.KEY WORDS: Flavivirus, microcephaly and Guillain–Barre’ syndrome, mosquito, receptors, Zika viru

Combining electric vehicle battery charging and battery cell equalisation in one circuit

Electric vehicles (EVs) require an onboard battery charger unit and a battery management system (BMS) unit that balances the voltage levels for each battery cell. So far both units are two completely autarkic power electronics systems. This paper presents a circuit that operates as a battery charger when the EV is connected to the grid and as a voltage balancer when the EV is driving. Thus, the proposed circuit utilises two functions in one and therefore eliminates the need of having two autarkic units reducing complexity and reduction in component count. The proposed circuit operates as a flyback converter and achieves power factor correction during battery charging. The constant-current constant-voltage (CC–CV) charging method is employed to charge the batteries. However, to limit the number of sensors that will be employed as a result of varying cells during charging, the battery current is estimated using a single current transducer and embedding a converter model in the controller. The operation of the circuit is presented in detail and is supported by simulation results. A laboratory prototype is built to verify the effectiveness of the proposed topology. Experiment results show that the proposed method provides an integrated solution of on-board charging and voltage equalisation