@article{roy_awartani_sen_o'connor_kudenov_2016, title={Intrinsic coincident linear polarimetry using stacked organic photovoltaics}, volume={24}, ISSN={["1094-4087"]}, DOI={10.1364/oe.24.014737}, abstractNote={Polarimetry has widespread applications within atmospheric sensing, telecommunications, biomedical imaging, and target detection. Several existing methods of imaging polarimetry trade off the sensor's spatial resolution for polarimetric resolution, and often have some form of spatial registration error. To mitigate these issues, we have developed a system using oriented polymer-based organic photovoltaics (OPVs) that can preferentially absorb linearly polarized light. Additionally, the OPV cells can be made semitransparent, enabling multiple detectors to be cascaded along the same optical axis. Since each device performs a partial polarization measurement of the same incident beam, high temporal resolution is maintained with the potential for inherent spatial registration. In this paper, a Mueller matrix model of the stacked OPV design is provided. Based on this model, a calibration technique is developed and presented. This calibration technique and model are validated with experimental data, taken with a cascaded three cell OPV Stokes polarimeter, capable of measuring incident linear polarization states. Our results indicate polarization measurement error of 1.2% RMS and an average absolute radiometric accuracy of 2.2% for the demonstrated polarimeter.}, number={13}, journal={OPTICS EXPRESS}, author={Roy, S. Gupta and Awartani, O. M. and Sen, P. and O'Connor, B. T. and Kudenov, M. W.}, year={2016}, month={Jun}, pages={14737–14747} }
 @inproceedings{dutta_roy_bhattacharya_2014, title={A mode switching, multiterminal converter topology with integrated fluctuating renewable energy source without energy storage}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84900400574&partnerID=MN8TOARS}, DOI={10.1109/apec.2014.6803342}, abstractNote={An important functionality of the Solid State Transformer (SST) is the integration of renewable energy sources within the topology itself, acting as a renewable energy hub. Due to the fluctuating nature of the renewable energy source, such integration becomes a challenge and energy storage becomes a requirement. In this paper a topology variant of single phase SST with multi limb magnetic core is proposed which directly integrates the renewable energy source in the high frequency magnetic stage and uses the grid as the energy buffer eliminating the requirement of energy storage.}, booktitle={Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC}, author={Dutta, S. and Roy, S. and Bhattacharya, Subhashish}, year={2014}, pages={419–426} }
 @inproceedings{de_roy_bhattacharya_2014, title={Comparative suitability evaluation of reverse-blocking IGBTs for current-source based converter}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84906662202&partnerID=MN8TOARS}, DOI={10.1109/ipec.2014.6869950}, abstractNote={In this paper, a Reverse Blocking IGBT is compared with various other combinations of switches and diodes keeping Current Source based Converter application in mind. The devices are tested under Reverse Voltage Commutation, Switch Overlap (turn on at non-zero current but zero voltage), Hard Switching, and Zero Current Switching condition. Test Circuits have been constructed and tested at various voltage levels with various combinations of devices. Forward Characteristics have also been compared. The main motivation of the paper is to make a fair judgment on device selection for Partial Resonant Link AC/AC Converter (soft-switched) and Isolated Dynamic Current Converter (hard switched). As for soft switched, majority of the losses are caused due to conduction loss. Therefore, RB-IGBT leads to a huge reduction of losses owing to better forward characteristics (lower conduction loss) as compared to the rest of the set. SiC-MOS and SiC-JBS Diode combination showed significant loss reduction for hard switched converter.}, booktitle={2014 International Power Electronics Conference, IPEC-Hiroshima - ECCE Asia 2014}, author={De, A. and Roy, S. and Bhattacharya, Subhashish}, year={2014}, pages={2562–2568} }
 @inproceedings{roy_de_bhattacharya_2014, title={Current source inverter based cascaded solid state transformer for AC to DC power conversion}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84906690154&partnerID=MN8TOARS}, DOI={10.1109/ipec.2014.6869656}, abstractNote={There are applications like railway traction system where power converters for HVAC to MVDC or MDAC to LVDC are required with a high power/weight ratio. The conventional way is to use heavy line frequency or medium frequency transformers followed by a controlled rectifier. The availability of high voltage SiC devices has made it possible to raise the switching frequency to higher value and hence the size and weight of the transformer can be reduced. This paper proposes a cascaded current source converter based topology with high frequency isolation as a replacement of the huge line frequency transformer. The paper also presents experimental results as a validation of the functionality of the converter.}, booktitle={2014 International Power Electronics Conference, IPEC-Hiroshima - ECCE Asia 2014}, author={Roy, S. and De, A. and Bhattacharya, Subhashish}, year={2014}, pages={651–655} }
 @inproceedings{roy_de_bhattacharya_2014, title={Multi-port solid state transformer for inter-grid power flow control}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84906689584&partnerID=MN8TOARS}, DOI={10.1109/ipec.2014.6870158}, abstractNote={This paper discusses about a multi-port solid state transformer (SST) which can be used as an inter-grid power flow controller. The objective of the converter is to integrate renewable energy sources with the existing grid along with controlled power flow between the grids. As an example, this paper describes a three terminal isolated SST with an integrated battery bank connected to it. The energy extracted from the renewable energy sources can be stored in the battery bank or can be directly fed to the utility grid. A suitable converter structure is chosen to activate bidirectional power flow between the energy sources. The extracted energy can also be used to supply the local demand. A laboratory prototype of the converter has been built and the functionality of the converter is validated with detailed experimental results.}, booktitle={2014 International Power Electronics Conference, IPEC-Hiroshima - ECCE Asia 2014}, author={Roy, S. and De, A. and Bhattacharya, Subhashish}, year={2014}, pages={3286–3291} }
 @inproceedings{dutta_roy_bhattacharya_2013, title={A multi-terminal DC to DC converter topology with power accumulation from renewable energy sources with unregulated DC voltages}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84879384693&partnerID=MN8TOARS}, DOI={10.1109/apec.2013.6520440}, abstractNote={The following paper details out a converter topology which can act as an accumulator of power from different renewable energy sources (RES). Due to the intermittent nature of power availability from RES the DC buses are assumed unregulated. The proposed topology decouples individual voltage sources and reduces unwanted circulation of reactive power between the busses due to mismatch in voltage levels, and at the same time accumulates the power and produces a regulated DC output. The magnetic design of the transformer core has been shown and the topology has been verified with hardware experimental results.}, booktitle={Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC}, author={Dutta, S. and Roy, S. and Bhattacharya, Subhashish}, year={2013}, pages={1124–1130} }
 @inproceedings{de_roy_bhattacharya_2013, title={Bidirectional soft-switched AC/AC high frequency link converter}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84891133946&partnerID=MN8TOARS}, DOI={10.1109/ecce.2013.6647430}, abstractNote={This paper investigates a soft-switching partial-resonant link AC/AC converter. The proposed converter uses 12 unidirectional switches and overcomes the various shortcomings of conventional AC Link schemes. The switching operations occur at zero voltage instants thus lowering the switching losses. The input and output current is harmonic free and the controller also allows setting of desired power factor. It can perform buck and boost operations and has bi-directional power flow capability. As the converter operates at high switching frequency, it offers both improved performance and considerable reduction of volume, weight and cost. Detailed simulation results are presented and prototype converter system has been built and tested.}, booktitle={2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013}, author={De, A. and Roy, S. and Bhattacharya, Subhashish}, year={2013}, pages={5377–5384} }
 @inproceedings{de_roy_bhattacharya_divan_2013, title={Characterization and performance comparison of reverse blocking SiC and Si based switch}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84893572618&partnerID=MN8TOARS}, DOI={10.1109/wipda.2013.6695567}, abstractNote={In this paper a custom made Reverse Voltage Blocking 1200V SiC switch or “current switch” (1200V SiC MOSFET in series with a 1200V SiC JBS diode) is compared with various other combinations of Reverse Voltage Blocking switches (with 1200V Si-IGBT, SiC MOSFET and Si-PIN diodes and SiC JBS diodes). The devices are tested under Reverse Voltage Commutation, Switch Overlap (turn on at non-zero current but zero voltage) and Hard Switching conditions. Test circuits have been constructed and tested at different dc voltage levels with various combinations of devices. The custom made current switch results show remarkable reduction of loss owing to reduced leakage inductance of the package. A new form of switching characteristic has been noticed and presented in this paper. The main motivation of the paper is to make a fair judgment on device selection for current stiff based hard and soft switching topologies.}, booktitle={1st IEEE Workshop on Wide Bandgap Power Devices and Applications, WiPDA 2013 - Proceedings}, author={De, A. and Roy, S. and Bhattacharya, Subhashish and Divan, D.M.}, year={2013}, pages={80–83} }
 @inproceedings{baliga_hazra_singh_roy_bhattacharya_paulakonis_notani_2013, title={Device characterization and performance of 1200V/45A SiC JFET module}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84891141152&partnerID=MN8TOARS}, DOI={10.1109/ecce.2013.6646711}, abstractNote={This paper evaluates the hard-switching performance of a novel cascode configuration of a 1200V/45A SiC JFET module. The device is first characterized and then switched up to 600V through double pulse testing. The capacitive effects of the device are analyzed and account for a significant current spike during turn-on. The switching behavior due to the gate drive circuitintroduction of varied gate resistances is discussed and analyzed. The switching behavior allows for the extraction of rise time, fall time, dV/dt, di/dt, and the switching losses - Eon and Eoff - while applying these varying gate resistances. The gate drive circuit is discussed and the hardware and test setup are shown and presented.}, booktitle={2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013}, author={Baliga, V. and Hazra, S. and Singh, S. and Roy, S. and Bhattacharya, Subhashish and Paulakonis, J. and Notani, S.}, year={2013}, pages={273–278} }
 @inproceedings{de_roy_bhattacharya_divan_2013, title={Performance analysis and characterization of current switch under reverse voltage commutation, overlap voltage bump and zero current switching}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84879373029&partnerID=MN8TOARS}, DOI={10.1109/apec.2013.6520636}, abstractNote={Diode reverse recovery is notorious for increasing switching losses in current stiff converters. A lot of effort has been made over the years to mitigate the reverse recovery losses. However, there exists ways to use this feature to achieve zero voltage transition in the same converter thereby, mitigating the loss incurred as compared to hard switched turn off. An attempt has been made in this paper to demonstrate the behavior of several devices working under Reverse voltage commutation, hard switched and zero current turn off condition. Test Circuits have been constructed and tested at various voltage levels with various combinations of devices. A new form of switching characteristic has been noticed and presented in this paper. The main motivation of the paper is to make a fair judgment on device selection for various soft-switch based topologies.}, booktitle={Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC}, author={De, A. and Roy, S. and Bhattacharya, Subhashish and Divan, D.M.}, year={2013}, pages={2429–2435} }
 @inproceedings{baek_roy_bhattacharya_kim_2013, title={Power flow analysis for 3-port 3-phase dual active bridge dc/dc converter and design validation using high frequency planar transformer}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84891090658&partnerID=MN8TOARS}, DOI={10.1109/ecce.2013.6646727}, abstractNote={In this paper, an inductor-integrated three-winding shell-type planar transformer is designed and analyzed for three-port dual-active bridge (DAB) dc/dc converters in wye wye-delta connection. The steady-state operation principle of the proposed topology has been studied and design parameters of the isolation transformer are analytically determined. The proposed geometry and design method for the ac-link transformer allows us to integrate a large number of bulky inductors required for three phase DAB operation to the transformer without additional connections and unanticipated parasitic effects. It also considerably simplifies the equivalent leakage inductance circuit model and power flow analysis. This configuration is suitable for high power and high step up/down ratio dc/dc converter applications which requires series and/or parallel combination of converters. The experimental and FEM simulation results from prototypes are presented and it validates the theoretical considerations and feasibility of the proposed approach for isolated dc/dc converter applications such as solid-state transformer (SST).}, booktitle={2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013}, author={Baek, S. and Roy, S. and Bhattacharya, Subhashish and Kim, S.}, year={2013}, pages={388–395} }
 @inproceedings{dutta_roy_bhattacharya_2013, title={integration of multi-terminal dc to dc hub architecture with solid state transformer for renewable energy integration}, booktitle={2013 ieee energy conversion congress and exposition (ecce)}, author={Dutta, S. and Roy, S. and Bhattacharya, S.}, year={2013}, pages={4793–4800} }
 @inproceedings{de_roy_bhattacharya_2012, title={Efficiency Comparison of AC-Link and TIPS (SST) Topologies based on accurate device models}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84870894365&partnerID=MN8TOARS}, DOI={10.1109/ecce.2012.6342282}, abstractNote={In this paper, a comparative study on AC-Link™ Topology and a conventional solid state transformer (TIPS) has been shown. Alongside, as a building block, a comparative device level design study has been shown for 6.5kV Si-IGBT/SiC JBS diode, 6.5kV Si-IGBT/Si-PiN Diode and 10kV SiC-MOSFET/SiC-JBS Diode for a zero voltage/current transition and hard switched condition for medium voltage application. It is shown that soft switching yields a considerable reduction of losses for all devices. A low voltage hardware device test prototype has been built and tested. The main motive of the paper is to make a fair judgment on the two topologies with accurate device testing. This is further extended to the maximum attainable frequency analysis, corresponding efficiency comparison, frequency transfer capability and various other topology based comparisons.}, booktitle={2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012}, author={De, A. and Roy, S. and Bhattacharya, Subhashish}, year={2012}, pages={3862–3868} }
 @inproceedings{kumar_green_de_roy_bhattacharya_2012, title={Field Programmable Analog Array (FPAA) based Shunt Active Filter controller}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84870904185&partnerID=MN8TOARS}, DOI={10.1109/ecce.2012.6342708}, abstractNote={The presence of multiple harmonics in the power line due to various non-linear loads like adjustable speed drives, computers, fax machine, PLC's, etc. requires high frequency switching of an active filter inverter so as to reduce the harmonic content at the point of common coupling (PCC) to be typically lower than 5% as specified by IEEE 519 harmonic standards. In this paper, the Field Programmable Analog Array (FPAA) based analog controller has been used to implement a Synchronous Reference Frame (SRF) controller algorithm for harmonic current extraction for Shunt Active Filter controller and the results are compared with the conventional digital implementation on Field Programmable Gate Array (FPGA). The FPAA based analog controller implementation proves to be faster than the digital FPGA implementation and can be a potential to replace analog controllers used for active filters.}, booktitle={2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012}, author={Kumar, M. and Green, E. and De, A. and Roy, S. and Bhattacharya, Subhashish}, year={2012}, pages={1011–1016} }