@article{gulur_iyer_bhattacharya_2022, title={Integrated Single-Stage EMI Filters for Grid-Tied Voltage Source Converters: A Design Oriented Approach}, ISSN={["2329-3721"]}, DOI={10.1109/ECCE50734.2022.9947614}, abstractNote={This work introduces and elucidates a general framework for designing and evaluating the performance of a standard single-stage, multi-order integrated electromagnetic interference (EMI) filter for grid-tied, 3ϕ voltage source converters (VSCs). The proposed methodology is based on designing the EMI filter to meet power quality (PQ) requirements while providing adequate attenuation to both differential mode (DM) and common mode (CM) noise generated by the 3ϕ VSC to comply with conducted emissions (CE) recommendations. The impact of switching frequency of the power converter on the filter size is investigated to understand the performance limits of single-stage EMI filters and to offer guidelines as to when such a single-stage filter is feasible. A size comparison for the magnetic components used in the EMI filter has been performed using an area product approach. Additionally, various single-stage CM and DM filter performances have been analyzed and compared. A hardware prototype with a single-stage EMI filter has been implemented based on the proposed design guidelines. Time-domain and CE experimental results for a 3ϕ VSC prototype interfaced to the utility grid are provided to showcase the validity of the single-stage integrated EMI filter design to meet multiple performance constraints.}, journal={2022 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE)}, author={Gulur, Srinivas and Iyer, Vishnu Mahadeva and Bhattacharya, Subhashish}, year={2022} }
 @article{gulur_iyer_bhattacharya_2020, title={A CM Filter Configuration for Grid-Tied Voltage Source Converters}, volume={67}, ISSN={["1557-9948"]}, url={https://doi.org/10.1109/TIE.2019.2949530}, DOI={10.1109/TIE.2019.2949530}, abstractNote={Common mode (CM) filters play a crucial role in determining adherence to conducted emissions (CE) standards for grid-tied voltage source converters. Design and implementation of such filters can be challenging since they depend on several factors like identification of CM noise paths, fidelity of passive components and discerning the frequency and amplitude of CM noise sources. In this article, a CM filter has been proposed, which uses passive components along with the converter's heat sink as a circulating return path for the CM currents. Based on the presented CM circuit models with the proposed filter, a detailed design process has been delineated for selecting the passive components required to realize the CM filter. Additionally, the heat-sink potential has been shown to be touch safe during both ideal and nonideal grid conditions with the proposed CM filter. CE spectral results measured using a commercially procured line impedance stabilization network and captured time domain converter operational wave forms for a 2-level, 3$\phi$ grid-tied voltage source converter validate the functionality and effectiveness of the presented design.}, number={10}, journal={IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Gulur, Srinivas and Iyer, Vishnu Mahadeva and Bhattacharya, Subhashish}, year={2020}, pages={8100–8111} }
 @article{iyer_gulur_gohil_bhattacharya_2020, title={An Approach Towards Extreme Fast Charging Station Power Delivery for Electric Vehicles with Partial Power Processing}, volume={67}, ISSN={["1557-9948"]}, url={https://doi.org/10.1109/TIE.2019.2945264}, DOI={10.1109/TIE.2019.2945264}, abstractNote={This article proposes an approach for realizing the power delivery scheme for an extreme fast charging (XFC) station that is meant to simultaneously charge multiple electric vehicles (EVs). A cascaded H-bridge converter is utilized to directly interface with the medium voltage grid while dual-active-bridge based soft-switched solid-state transformers are used to achieve galvanic isolation. The proposed approach eliminates redundant power conversion by making use of partial power rated dc–dc converters to charge the individual EVs. Partial power processing enables independent charging control over each EV, while processing only a fraction of the total battery charging power. Practical implementation schemes for the partial power charger unit are analyzed. A phase-shifted full-bridge converter-based charger is proposed. Design and control considerations for enabling multiple charging points are elucidated. Experimental results from a down-scaled laboratory test-bed are provided to validate the control aspects, functionality, and effectiveness of the proposed XFC station power delivery scheme. With a down-scaled partial power converter that is rated to handle only 27% of the battery power, an efficiency improvement of 0.6% at full-load and 1.6% at 50% load is demonstrated.}, number={10}, journal={IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Iyer, Vishnu Mahadeva and Gulur, Srinivas and Gohil, Ghanshyamsinh and Bhattacharya, Subhashish}, year={2020}, pages={8076–8087} }
 @inproceedings{iyer_gulur_gohil_bhattacharya_2018, title={Extreme fast charging station architecture for electric vehicles with partial power processing}, volume={2018-March}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85046972946&partnerID=MN8TOARS}, DOI={10.1109/apec.2018.8341082}, abstractNote={This paper introduces a power delivery architecture for an Extreme Fast Charging (XFC) station that is meant to simultaneously charge multiple electric vehicles (EVs) with a 300-mile range battery pack in about 15 minutes. The proposed approach can considerably improve overall system efficiency as it eliminates redundant power conversion by making use of partial power rated dc-dc converters to charge the individual EVs as opposed to a traditional fast charging station structure based on full rated dedicated charging converters. Partial power processing enables independent charging control over each EV, while processing only a fraction of the total battery charging power. Energy storage (ES) and renewable energy systems such as photovoltaic (PV) arrays can be easily incorporated in the versatile XFC station architecture to minimize the grid impacts due to multi-mega watt charging. A control strategy is discussed for the proposed XFC station. Experimental results from a scaled down laboratory prototype are provided to validate the functionality, feasibility and cost-effectiveness of the proposed XFC station power architecture.}, booktitle={2018 IEEE Applied Power Electronics Conference and Exposition (APEC)}, author={Iyer, V. M. and Gulur, S. and Gohil, G. and Bhattacharya, S.}, year={2018}, month={Mar}, pages={659–665} }
 @inproceedings{gulur_iyer_bhattacharya_2018, title={Proportional integral — Resonant and dual loop current control structure comparison for grid connected converters in the rotating frame}, volume={2018-March}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85046961004&partnerID=MN8TOARS}, DOI={10.1109/apec.2018.8341233}, abstractNote={Over the past few years, due the increasing penetration of renewable energy, there has been a steady rise in the harmonic content in grid voltages. In such circumstances, a proportional integral (PI) based current control in the synchronous reference rotating frame (dq) for a grid connected voltage source converter may not be adequate to suppress the harmonic components and to precisely follow the fundamental frequency component with zero steady state error. Several current control structures have been proposed, with proportional integral — resonant controller (PI-RES) based structure being one of the most popular. In this paper, the PI-RES has been compared to the recently introduced dual loop current control structure. Both these current control structures have been compared in terms of their tracking, filtering and disturbance rejection capability. Robustness of both these structures has also been analyzed under a grid impedance variation. Simulation and experimental results have been provided to validate the analysis presented.}, booktitle={2018 IEEE Applied Power Electronics Conference and Exposition (APEC)}, author={Gulur, S. and Iyer, V. M. and Bhattacharya, S.}, year={2018}, month={Mar}, pages={1617–1623} }
 @inproceedings{gulur_iyer_bhattacharya_2018, title={Stationary reference frame based current control structure with improved disturbance rejection for grid connected converters}, volume={2018-March}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85046936440&partnerID=MN8TOARS}, DOI={10.1109/apec.2018.8341142}, abstractNote={A proportional resonant (PR) controller is commonly used for tracking the reference current with zero steady state error in the stationary reference frame (abc or αβ) for the voltage source converter. Such a structure suffers from poor disturbance rejection capability when the grid voltages contain harmonic components. This results in higher harmonic distortion in the grid currents which is not desirable. This paper introduces a virtual loop based current control structure for improving the voltage and the current disturbance rejection capability. The virtual loop based current control structure also decouples the reference tracking and disturbance rejection leading to simpler controller designs. Frequency domain plots and analysis have been provided to validate the presented control structure. Detailed circuit simulation results have been used to verify the presented analysis.}, booktitle={2018 IEEE Applied Power Electronics Conference and Exposition (APEC)}, author={Gulur, S. and Iyer, V. M. and Bhattacharya, S.}, year={2018}, month={Mar}, pages={1031–1035} }
 @inproceedings{gulur_iyer_bhattacharya_2017, title={A dual loop current control structure with improved disturbance rejection for grid connected converters in the synchronous rotating reference frame}, volume={2017-January}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85041457092&partnerID=MN8TOARS}, DOI={10.1109/ecce.2017.8096684}, abstractNote={Increase in renewable energy penetration, in the recent past, has been one of the primary causes for serious issues in power quality of the utility grid. This has ushered in the need for a robust and stable control system for reference tracking and disturbance rejection of grid-connected converters. Conventionally, due to its simplicity and ability to achieve zero steady-state error, a simple proportional integral (PI) controller is used in the synchronous reference frame ($dq$) for current control of voltage-source based grid-connected systems. However, the PI controller by itself, may not suffice for adequate disturbance rejection, especially when the utility grid voltages contain other harmonics in addition to the fundamental component. This paper introduces and analyzes a dual-loop current control structure, which utilizes two independent controllers, one for reference tracking and the other for disturbance rejection in the $dq$ frame. A small signal model of the dual-loop current control has been presented and its robustness under grid impedance variation, examined. Extensive experimental results are presented to validate the dual-loop control strategy for improved disturbance rejection capability and filtering action during the presence of grid voltage disturbances and grid impedance variations, without compromising the reference tracking performance.}, booktitle={2017 ieee energy conversion congress and exposition (ecce)}, author={Gulur, S. and Iyer, V. M. and Bhattacharya, S.}, year={2017}, pages={3890–3896} }
 @inproceedings{iyer_gulur_bhattacharya_2017, title={Hybrid control strategy to extend the ZVS range of a dual active bridge converter}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85020000052&partnerID=MN8TOARS}, DOI={10.1109/apec.2017.7930979}, abstractNote={This paper presents a hybrid control strategy for a dual active bridge (DAB) based dc-dc converter which combines the benefits of traditional phase shift and burst mode modulation schemes. The advantage of using such a control strategy stems from the fact that it can extend the zero voltage switching (ZVS) range of all power switches in both the primary and secondary bridges when there is a wide variation in input or output voltage. In addition, the hybrid control strategy improves the light load efficiency of the DAB converter. The paper focuses on the development of the average and small signal models for the DAB converter with the hybrid modulation scheme. Digital implementation considerations of the hybrid control scheme are discussed. The effectiveness of the proposed control strategy has been tested and validated through simulations and experiments.}, booktitle={2017 IEEE Applied Power Electronics Conference and Exposition (APEC)}, author={Iyer, V. M. and Gulur, S. and Bhattacharya, S.}, year={2017}, month={Mar}, pages={2035–2042} }
 @inproceedings{iyer_gulur_bhattacharya_2017, title={Optimal design methodology for dual active bridge converter under wide voltage variation}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85028592472&partnerID=MN8TOARS}, DOI={10.1109/itec.2017.7993306}, abstractNote={Dual active bridge (DAB) converter is a popular topology for bidirectional on-board electric vehicle (EV) charger systems and other energy storage applications. In such systems, wide variation in the battery voltage makes design of the DAB converter non-trivial. The focus of this paper is on the optimal selection of DAB parameters when there is a wide variation in the output voltage. Different optimal strategies based on a minimal Euclidean norm approach, namely ‘minimal rms current design’, ‘minimal peak current design’ and ‘minimal power loss design’ are compared to illustrate the effect on system performance with output voltage variation. The proposed optimal design approaches are shown to be superior to a conventional design approach. A loss model for the DAB converter that can be used in the optimal design process is presented. The proposed optimal strategies are validated with experimental results using a laboratory prototype.}, booktitle={2017 ieee transportation electrification conf and expo (itec)}, author={Iyer, V. M. and Gulur, S. and Bhattacharya, S.}, year={2017}, pages={413–420} }
 @inproceedings{chattopadhyay_juds_gohil_gulur_ohodnicki_bhattacharya_2017, title={Optimized design for three port transformer considering leakage inductance and parasitic capacitance}, volume={2017-January}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85041441738&partnerID=MN8TOARS}, DOI={10.1109/ecce.2017.8096588}, abstractNote={The power flow capability of high frequency phase-shifted dc-dc converter depends on transformer leakage inductance and switching frequency. The design of multi-port transformer requires optimized volume and losses with required leakage inductance for rated power flow. Use of fast-switching SiC devices also demand low inter-winding parasitic capacitance for reduced common mode current. The work in this paper focuses on loss-volume optimized design of three port high frequency transformer integrating PV and Energy Storage(ES) based on leakage inductance and parasitic capacitance model. Two laboratory prototypes of 50kHz and 100kHz operating frequency have been designed to verify the leakage and parasitic capacitance model based design and the losses of the transformers.}, booktitle={2017 IEEE Energy Conversion Congress and Exposition, ECCE 2017}, author={Chattopadhyay, R. and Juds, M.A. and Gohil, G. and Gulur, S. and Ohodnicki, P.R. and Bhattacharya, Subhashish}, year={2017}, pages={3247–3254} }
 @inproceedings{iyer_gulur_bhattacharya_2017, title={Small-signal modeling and stability analysis of a bidirectional electric vehicle charger}, DOI={10.1109/icrera.2017.8191214}, abstractNote={This paper addresses the stability challenges that exist in a bidirectional grid connected electric vehicle (EV) charger. The EV charger under consideration comprises of an ac-dc single phase active rectifier stage followed by a dc-dc dual active bridge (DAB) stage. small-signal models suited for stability analysis of this charger are derived. Controller design considerations are discussed in order to ensure closed loop stability of individual stages and to prevent any instability due to interaction between the stages. Experimental results on an EV charger hardware prototype are presented to validate the proposed models and control design considerations.}, booktitle={2017 ieee 6th international conference on renewable energy research and applications (icrera)}, author={Iyer, V. M. and Gulur, S. and Bhattacharya, S.}, year={2017}, pages={1030–1035} }
 @inproceedings{iyer_gulur_bhattacharya_2017, title={Variable DC bus control for a bidirectional on-board electric vehicle charger}, DOI={10.1109/icrera.2017.8191216}, abstractNote={In this paper, a variable dc bus control strategy is evaluated for a bidirectional grid connected electric vehicle (EV) charger topology. The EV charger under consideration comprises of an ac-dc 3-φ active rectifier stage followed by a dc-dc dual active bridge (DAB) converter. The voltage of the common dc-link between the ac-dc stage and the dc-dc stage is regulated such that it follows the voltage variations of the battery pack. The proposed control strategy helps to minimize circulating reactive currents in the DAB converter and extends the soft-switching operating range of the same to achieve high system efficiency. An optimal design approach is presented to select the DAB converter parameters that can be used in conjunction with the variable dc bus control strategy. Experimental results on a 3.3 kW EV charger hardware prototype validate the benefits of the variable dc bus control and proposed optimal design methodology.}, booktitle={2017 ieee 6th international conference on renewable energy research and applications (icrera)}, author={Iyer, V. M. and Gulur, S. and Bhattacharya, S.}, year={2017}, pages={1041–1046} }