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S. Dasgupta,S. N. Mohan,S. K. Sahoo,S. K. Panda 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
In this paper, inverter reference current generation for a three phase grid connected PV inverter under generalized grid voltage conditions is proposed. The proposed method facilitates high bandwidth grid active and reactive power flow control along with minimum DC link ripples with grid current THD control facility by finding suitable current reference directly in the a-b-c frame. The proposed method is much faster than the conventional methods because of the absence of phase lock loop (PLL) and Park’s transformation requirements. The proposed method is also independent of grid voltage fundamental frequency and capable of rejecting the grid voltage harmonics. These advantages make it more suitable for micro-grid applications. The proposed method is validated with rigorous experiments and test results presented depict the efficacy of the proposed system.
S. Dasgupta,S. N. Mohan,S. K. Sahoo,S. K. Panda 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
In this paper, a novel control system is proposed to control the active and reactive grid power flow in a three phase grid connected PV inverter. The control system not only controls the grid power but also reduces the grid current THD in the presence of typical non-linear loads in parallel with grid at the point of common coupling (PCC). The proposed control system also takes care of not only the grid voltage unbalance but also the unbalance in the connecting line side inductors. The stability of the proposed control system is ensured by the direct method of Lyapunov. The proposed control system is not only simple to implement in the digital form but also provides superior performance over the conventional multiple PI or resonant control methods. A new grid connected inverter modeling technique is also proposed to take care of unbalances in the inverter system. Experimental results are provided to show the efficacy of the proposed control system.
Kinetic model of Janaki et al.'s bifurcated current sheet : YOON ET AL.
Yoon, P. H.,Janaki, M. S.,Dasgupta, B. American Geophysical Union 2014 JOURNAL OF GEOPHYSICAL RESEARCH. SPACE PHYSICS Vol.119 No.1
Space satellite observations show that current sheets in the space plasma environment are often characterized by bifurcated structures. In a recent paper a two-fluid model of the bifurcated current sheet was constructed on the basis of the pseudo potential method. A straightforward generalization of Janaki et al.'s two-fluid model to kinetic formalism, however, leads to an unphysical situation of negative particle velocity distribution function occurring over a certain range of velocity space. If one assumes an isotropic background plasma population, however, one can show that a rigorous, physically valid kinetic solution of the bifurcated current sheet can be obtained.Key Points<list list-type='bulleted'> <list-item id='jgra50781-li-0001'>Kinetic model of bifurcated current sheet <list-item id='jgra50781-li-0002'>Generalization of Janaki et al's fluid model
Low power SRAM design for 14nm GAA Si-nanowire technology
Kaushal, G.,Jeong, H.,Maheshwaram, S.,Manhas, S.K.,Dasgupta, S.,Jung, S.O. Mackintosh Publications] 2015 Microelectronics Journal Vol.46 No.12
This paper presents a low power and stable 6-T nanowire SRAM cell design by tuning the extension length of the access transistor. Our approach significantly reduces the power dissipation with a low active area and improves the SRAM cell read stability. We utilize device design parameters such as the nanowire diameter, the number of nanowires, and the device extension length to improve the stability of the SRAM cells. We find that the extension length tuning technique exhibits 15% and ~60% savings in active area and static power consumption, respectively, in comparison to a conventional multi-nanowire tuning technique. In addition, the proposed technique achieves 6% and 8% improvements in the read and hold noise margins, respectively, with a 6.5% decrease in write noise margin and a ~14% increase in the read/write access time. Our results show that the extension length-tuned access transistor is an excellent option for improving the satiability with low power for sub-14-nm technologies.
Studies on Nanostructured Amorphous Carbon by X-ray Diffraction and Small Angle X-ray Scattering
Dasgupta, K.,Krishna, P.S.R.,Chitra, R.,Sathiyamoorth, D. Korean Carbon Society 2003 Carbon Letters Vol.4 No.1
The structural studies of amorphous isotropic carbon prepared from pyrolysis of phenol formaldehyde resin have been carried out using X-ray diffraction. X-ray diffraction from as prepared sample at $1000^{\circ}C$ and a sample treated at $1900^{\circ}C$ revealed that both are amorphous even though there are small differences in short range order. It is found that both are graphite like carbon (GLC) with predominantly $sp^2$ hybridization. Small angle X-ray scattering results show that as prepared sample mainly consists of thin two dimensional platelets of graphitic carbon whereas they grow in thickness to become three dimensional materials of nano dimensions.
Studies on Nanostructured Amorphous Carbon by X-ray Diffraction and Small Angle X-ray Scattering
K. Dasgupta,P.S.R. Krishna,R. Chitra,D. Sathiyamoorth 한국탄소학회 2003 Carbon Letters Vol.4 No.1
The structural studies of amorphous isotropic carbon prepared from pyrolysis of phenol formaldehyde resin have been carried out using X-ray diffraction. X-ray diffraction from as prepared sample at 1000℃ and a sample treated at 1900℃ revealed that both are amorphous even though there are small differences in short range order. It is found that both are graphite like carbon (GLC) with predominantly sp2 hybridization. Small angle X-ray scattering results show that as prepared sample mainly consists of thin two dimensional platelets of graphitic carbon whereas they grow in thickness to become three dimensional materials of nano dimensions.
An Optimized MPPT Circuit for Thermoelectric Energy Harvester for Low Power Applications
Ko Ko Win,Souvik Dasgupta,Panda S.K. 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
A novel approach of maximum power point tracking (MPPT) control method for thermoelectric generator (TEG) is reported in this paper. The maximum power point tracking is achieved by using impedance matching principle. Unlike the existing MPPT methods, the proposed implementation does not require any voltage and current sensors and computations of any nature. The implementation of the MPPT control circuit is carried out using buck-boost DC/DC converter and a simple gating signal generator using only one Op-amp. The proposed method needs the least power consumption of the MPPT control circuit ? less than 250㎼. Experimental tests results obtained from series connected 3xTEGs (24 ㎜ x 6 ㎜) show an average power harvesting of 5.6㎽ at △T of 24℃. The proposed thermoelectric energy harvester is used to power a battery which subsequently feeds a sensor node. The low power thermoelectric energy harvester system provides an overall power management circuit efficiency of up to 85%. The efficiency calculation takes care of power losses in the MPPT circuit.
Evaluating Applicability of a Scroll Expander for CO2 Refrigeration System at Warm Climate
Simarpreet Singh,M. S. Dasgupta 대한설비공학회 2017 International Journal Of Air-Conditioning and Refr Vol.25 No.2
Performance of a trans-critical CO2 refrigeration cycle equipped with a scroll work recovery expander is investigated using a semi-empirical model of the scroll, for high ambient temperature application. Maximum isentropic efficiency of 61% is obtained, for a pressure ratio of about 3.7 for the scroll expander. Simulation results obtained are further validated against the reported experimental results. It is also observed that, about 20% of the total energy consumed can be recovered with the help of scroll expander during trans-critical operation. Based on year-round ambient temperature data, at New Delhi (India), an economic analysis is carried out for installation of work recovery scroll system. Total payback period (PBP) for scroll expanders of various capacities are also determined. It is noted that the PBP of scroll expander is about 1 to 2 years or less, which is encouraging. Total Equivalent Warming Impact (TEWI) of the system is compared with that of a conventional trans-critical CO2 refrigeration system and system running on low global warming potential (GWP) hydrofluoroolefin (R1234yf) refrigerant. Trans-critical CO2 system along with work recovery scroll expander appears justified as the same has about 15% lower TEWI compared to conventional trans-critical CO2 system but is 50% more than R1234yf system