Comparative Study of the Dynamics of Cosmic Rays for the Pakistan and China Atmospheric Regions

This paper presents an analysis of cosmic ray intensity in Pakistan air space using spatial interpolation, comparing it with Chinese cosmic ray records from 1984 to 1993. The Exploratory Data Analytic (EDA) approach was applied to compare the cosmic ray fluctuations in both countries. The time series plot of the monthly cosmic rays showed relatively flatter counts in Pakistan than in China. The cosmic ray data for the years 1984 to 1993 fell within Solar Cycle 22, which lasted from 1986 to 1996, with its maximum phase in 1989 to 1991. The cosmic radiation varies between the atmospheric regions of Pakistan and China due to modulations in intensity that are accessible accordingly. It can be explained by purely astrophysical phenomena: (1) the source of emission of cosmic radiation may be different, (2) the rate at which emanation takes place depends on bursts of deep space dynamical objects from their sources that may be affected by solar wind and other solar radiations. Therefore, modulations in intensity are not only due to different geophysical locations. This study will help government organizations to predict and forecast cosmic rays values

Use of spread spectrum time domain reflectometry to estimate state of health of power converters

pre-printA new online measurement and analysis method has been presented in this paper to identify the state of health of power converter circuits. Using spread spectrum time domain reflectometry (SSTDR), impedance in the various current paths inside the converter as well as any fault can be identified without interrupting the circuit's normal operation. Multiple sets of test data have been generated while the SSTDR process is applied to each of the components i.e. the power MOSFETs, the dc bus capacitor and the load. These obtained test data are analyzed to show how these test results are consistent with the impedances in various current paths. An impedance matrix was formed for a non-aged converter and a corresponding matrix using SSTDR data was formed as well. The matrices could be formed for any power converter, and the impedance matrix for the non-aged converter could be considered as a "Reference matrix" for comparison purpose. By comparing these two matrices, the variation in path impedances due to aging could be determined. This research aims to identify the measurable quantities to characterize the aging process, their origins of these quantities and propose convenient methods to measure them

Quantifying device degradation in live power converters using SSTDR assisted impedance Matrix

pre-printA noninterfering measurement technique designed around spread spectrum time domain reflectometry (SSTDR) has been proposed in this paper to identify the level of aging associated with power semiconductor switches inside a live converter circuit. Power MOSFETs are one of the most age-sensitive components in power converter circuits, and this paper demonstrates how SSTDR can be used to determine the characteristic degradation of the switching MOSFETs used in various power converters. An SSTDR technique was applied to determine the aging in power MOSFETs, while they remained energized in live circuits. In addition, SSTDR was applied to various test nodes of an H-bridge ac-ac converter, and multiple impedance matrices were created based on the measured reflections. An error minimization technique has been developed to locate and determine the origin and amount of aging in this circuit, and this technique provides key information about the level of aging associated to the components of interest. By conducting component level failure analysis, the overall reliability of an H-bridge ac-ac converter has been derived and incorporated in this paper

Hybrid electric vehicle power management solutions based on isolated and nonisolated configurations of multilevel modular capacitor-clamped converter

Journal ArticleAbstract-This paper presents the various configurations of a multilevel modular capacitor-clamped converter (MMCCC), and it reveals many useful and new formations of the original MMCCC for transferring power in either an isolated or nonisolated manner. The various features of the original MMCCC circuit are best suited for a multibus system in future plug-in hybrid or fuel-cell-powered vehicles' drive train. The original MMCCC is capable of bidirectional power transfer using multilevel modular structure with capacitor-clamped topology. It has a nonisolated structure, and it offers very high efficiency even at partial loads. This circuit was modified to integrate single or multiple high-frequency transformers by using the intermediate voltage nodes of the converter. On the other hand, a special formation of the MMCCC can exhibit dc outputs offering limited isolation without using any isolation transformer. This modified version can produce a high conversion ratio from a limited number of components and has several useful applications in providing power to multiple low-voltage loads in a hybrid or electric automobile. This paper will investigate the origin of generating ac outputs from the MMCCC and shows how the transformer-free version can be modified to create limited isolation from the circuit. In addition, this paper will compare various modified forms of the MMCCC topology with existing dc-dc converter circuits from compactness and component utilization perspectives

Universal multilevel DC-DC converter with variable conversion ratio, high compactness factor and limited isolation feature

Journal ArticleA multilevel dc-dc converter with programmable conversion ratio (CR) is presented in this paper. This converter is a modified version of the MMCCC converter. A universal version of the MMCCC is developed in this paper, and the CR can be easily changed within a wide range. The MMCCC converter is based on capacitor-clamped topology, and the conversion ratio of the circuit depends on the number of active modules. However, like any other capacitor-clamped circuit, the MMCCC circuit requires a large number of transistors and capacitors to attain a high conversion ratio (CR). In this paper, a new circuit module will be introduced that can be connected in a cascade pattern to form the new converter. By using the new modular cell, it is possible to attain very high conversion ratio using a limited number of components, and thus more compactness compared to the predecessor MMCCC circuit can be achieved

A 5 kW Bi-directional multilevel modular DC-DC converter (MMCCC) featuring built in power management for fuel cell and hybrid electric automobiles

Journal ArticleAbstract- A new capacitor clamped modular dc-dc converter with bi-directional power handling capability will be presented in this paper. This inductor-free design is modular, and it is possible to integrate multiple loads and sources simultaneously in the converter. Moreover, this 5 kW dc-dc converter can produce multiple ac outputs to feed power to ac loads get further control over the conversion ratio of the circuit. This high efficiency modular converter has flexible conversion ratio, and it could be successfully used in a multi-bus power system by virtue of its inherent power management properties