Ultra-Efficient Cascaded Buck-Boost Converter

This thesis presents various techniques to achieve ultra-high-efficiency for Cascaded-Buck-Boost converter. A rigorous loss model with component non linearity is developed and validated experimentally. An adaptive-switching-frequency control is discussed to optimize weighted efficiency. Some soft-switching techniques are discussed. A low-profile planar-nanocrystalline inductor is developed and various design aspects of core and copper design are discussed. Finite-element-method is used to examine and visualize the inductor design. By implementing the above, a peak efficiency of over 99.2 % is achieved with a power density of 6 kW/L and a maximum profile height of 7 mm is reported. This converter finds many applications because of its versatility: allowing bidirectional power flow and the ability to step-up or step-down voltages in either direction

Effect of Cold Orifice Diameter and Geometry of Hot end Valves on Performance of Converging Type Ranque Hilsch Vortex Tube

AbstractRefrigeration by vortex tube works on the principle of heat transfer between two layers moving opposite to each other. Various experiments have been performed and has revealed two different approaches one for attaining high cold mass fraction and the other for attaining cold end temperature. The geometry requirement is different for the two approaches. The need is to have a tube to produce higher mass of cold air coming out at low temperature. For this purpose converging type of vortex tube is experimented and the results are promising. The results show increase in cold mass fraction as well as cold end temperature. The overall change in cold end temperature drop was 63% and the COP of the converging tube as compared to straight divergent tube increased by 102%. For conical valve angle of 45° air supply pressure of 5 bars and cold orifice diameter as 7mm the lowest temperature observed was 5°C producing cold mass fraction of about 0.9

A New Maximum Efficiency Point Tracking Technique For Digital Power Converter With Dual Parameters Control

This paper proposes a new maximum efficiency point tracking (MEPT) technique that will achieve the highest efficiency for DC-DC converters by automatically tracking converter efficiency while changing the switching frequency and dead-time control parameters. This new technique helps identify optimal values of each parameter at different power levels. In this paper, the developed MEPT technique is theoretically analyzed and practically verified. The experiment is set up based on a 120W Cascaded Buck-Boost converter, controlled by a centralized digital-signal processor (DSP). It will be shown that the expected theoretical and experimental results are in close agreement with each other