@article{prabowo_iyer_agarwal_bhattacharya_aeloiza_2023, title={Modular Hybrid Transformers Toward Grid Resilience: Efficiency Analysis and Operation}, volume={12}, ISSN={["1557-9948"]}, url={https://doi.org/10.1109/TIE.2023.3340215}, DOI={10.1109/TIE.2023.3340215}, abstractNote={This article proposes modular hybrid transformer architectures to improve grid resilience. The conventional line-frequency transformer is augmented with a partially rated power electronics converter to realize a hybrid transformer system. The proposed modular approach is envisioned to replace a single large power low-frequency transformer with multiple smaller rated hybrid transformer systems during disasters and emergencies. A hybrid transformer system enables controlled current sharing between the modular system. The efficiency analysis and operational aspects of a modular hybrid transformer architecture are thoroughly discussed in this article. The proposed efficiency analysis combines empirical data and numerical analysis of the overall modular hybrid transformer system. The optimum current sharing ratio to achieve maximum efficiency operation is presented for the proposed architectures. One of the proposed architectures (Configuration B) also offers load voltage regulation in case of grid voltage sag/swell occurrence. The proposed concept and analyses are experimentally validated through a scaled-down hardware prototype. The total ownership cost of the proposed system is also presented to emphasize the potential cost-benefits. Supplementary video files accompany this article to showcase the extensive experimental validation cases.}, journal={IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS}, author={Prabowo, Yos and Iyer, Vishnu Mahadeva and Agarwal, Apoorv and Bhattacharya, Subhashish and Aeloiza, Eddy}, year={2023}, month={Dec} }
 @article{agarwal_prabowo_bhattacharya_2023, title={Analysis and Design Considerations of Input Parallel Output Series-Phase Shifted Full Bridge Converter for a High-Voltage Capacitor Charging Power Supply System}, volume={59}, ISSN={["1939-9367"]}, url={https://doi.org/10.1109/TIA.2023.3276353}, DOI={10.1109/TIA.2023.3276353}, abstractNote={Capacitor charging power supply (CCPS) is used for impulse-power applications such as electromagnetic rail guns, flash lamps, medical sterilization, and rock crushing, among many other application fields. This article describes the design and analysis of an Input Parallel Output Series-Phase Shifted Full Bridge converter for CCPS. The proposed system has a low output current ripple to improve the lifetime of the high-voltage pulsed capacitor. Design considerations of topology's electrical parameters such as HF transformer's leakage inductor and output inductor for the CCPS application are presented. The intermediate DC-link capacitance is provided as an energy storage element to minimize the disturbances (power variation) on the source for the CCPS application. Analysis and sizing of the capacitance for two different charging methods are analyzed and compared. A controller design procedure for the Active Front End Converter (AFEC) is also included to ensure near-constant power drawn, rejecting the load disturbances. Finally, a complete design procedure for the whole CCPS system is presented. Design and simulation results are presented for a rated system, followed by experimental results from a scaled-down hardware prototype to validate the design.}, number={5}, journal={IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS}, author={Agarwal, Apoorv and Prabowo, Yos and Bhattacharya, Subhashish}, year={2023}, month={Sep}, pages={6037–6050} }
 @article{sharma_prabowo_bhattacharya_2023, title={Control of a Dual-Active-Bridge DC-DC Converter in a MV Grid-Compliant Solid-State Transformer Based DC Fast Charger}, ISSN={["1048-2334"]}, DOI={10.1109/APEC43580.2023.10131314}, abstractNote={A solid-state transformer (SST) system comprising cascaded H-bridge (CHB) and dual-active bridge (DAB) converters is a promising solution for a DC fast charger. This paper primarily focuses on the control design of the DAB converters for this system and utilizes a dual-loop based control scheme. The dual-loop consists of central voltage and inner current control loops. The inner current loops are needed to achieve current sharing between the paralleled DABs. In this paper, the inner current loop uses the DC output current of each DAB as the feedback signal. Thus, the control structure implemented in this paper is more cost-effective and computationally less intensive than the traditional approach of using a high-frequency current as the feedback signal. To provide a well-regulated output DC bus voltage, the control design considers the input disturbance due to the double-line frequency component in the DC-link voltage and the output disturbance due to load throw-off scenarios. An analytical model is derived for the complete dual-loop control structure of the DAB converter. The model evaluates the impact of disturbances due to the double-line frequency component and load throw-off scenarios on output DC bus voltage for different bandwidth combinations of the central voltage and inner current loops. Experimental results validating the analytical model are shown and discussed using a prototype of an SST system.}, journal={2023 IEEE APPLIED POWER ELECTRONICS CONFERENCE AND EXPOSITION, APEC}, author={Sharma, Shrivatsal and Prabowo, Yos and Bhattacharya, Subhashish}, year={2023}, pages={3147–3153} }
 @article{prabowo_sharma_bhattacharya_tripathi_bhavaraju_2023, title={ZVS Boundary Analysis and Design Guideline of MV Grid-Compliant Solid-State Transformer for DC Fast Charger Applications}, volume={9}, ISSN={["2332-7782"]}, url={https://doi.org/10.1109/TTE.2022.3229223}, DOI={10.1109/TTE.2022.3229223}, abstractNote={A solid-state transformer (SST) comprising a cascaded H-bridge and a dual active bridge (DAB) converter is a promising solution for a megawatt medium-voltage dc fast charger application. The new IEEE Std 1547.9-2022 comprehensively discusses extending the minimum reactive power capability to electric vehicle chargers. This article analyzes the impact of operating the grid compliant single-phase SST on the overall system. The impact of the dc-link voltage due to the single-phase implementation of the H-bridges on the DAB converter zero-voltage switching (ZVS) mode at light-load operation is highlighted. The system’s operational boundary is analyzed, which defines the reactive power capability limit while ensuring the DAB converter ZVS mode operation for the defined operating points. This ZVS mode boundary analysis is then used to develop a design guideline as part of the SST design process. The proposed guideline allows a simultaneous design of a dc-link capacitor and DAB inductance to ensure the ZVS mode for the defined operating points. It leads to dc-link capacitance reduction that offers cost- and footprint-savings. The proposed concept is validated through simulations and experimental results. Furthermore, a potential benefit analysis is provided to emphasize the effectiveness of the proposed concept. A supplementary video is included to showcase the system’s dynamic active and reactive power operation.}, number={4}, journal={IEEE TRANSACTIONS ON TRANSPORTATION ELECTRIFICATION}, author={Prabowo, Yos and Sharma, Shrivatsal and Bhattacharya, Subhashish and Tripathi, Awneesh Kumar and Bhavaraju, Vijay}, year={2023}, month={Dec}, pages={4964–4980} }
 @article{prabowo_sharma_bhattacharya_tripathi_bhavaraju_2022, title={ZVS Boundary Analysis and Design Guideline of MV Grid-Compliant Solid-State Transformer for DC Fast Charger Applications}, ISSN={["2329-3721"]}, DOI={10.1109/ECCE50734.2022.9947559}, abstractNote={A solid-state transformer comprising a cascaded H-bridge followed by a dual-active bridge converter is a promising solution for a megawatt medium voltage DC fast charger application. Previously, IEEE Std 1547– 2018 mandates a system with the capability of exporting an active power to have a minimum continuous reactive power capability to comply with IEEE Std 1547–2018. An approved revision of IEEE Std 1547–2018 comprehensively discusses to extend the minimum reactive power capability of electric vehicle chargers. This paper analyzes the impact of operating the grid compliant single-phase solid-state transformer on the overall system. The impact of the double-line frequency component of DC-link voltage on the DAB converter zero-voltage switching mode is emphasized. The zero-voltage switching mode boundary analysis is used to propose the design guidelines as part of the single-phase solid-state transformer design process. The proposed design guidelines are validated using switching simulations and experimental results.}, journal={2022 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE)}, author={Prabowo, Yos and Sharma, Shrivatsal and Bhattacharya, Subhashish and Tripathi, Awneesh K. and Bhavaraju, Vijay}, year={2022} }
 @article{agarwal_prabowo_bhattacharya_2021, title={Analysis and Design Considerations of Input Parallel Output Series-Phase Shifted Full Bridge Converter for a High-Voltage Capacitor Charging Power Supply}, ISSN={["2150-6078"]}, DOI={10.1109/ECCE-Asia49820.2021.9479247}, abstractNote={Capacitor charging power supplies (CCPS) are used for pulsed-power applications such as electromagnetic guns, radar applications, and pulsed lasers for aesthetic medicine, among many other application fields. This paper describes the design and analysis of an Input Parallel Output Series-Phase Shifted Full Bridge converter (IPOS-PSFB) for CCPS. In CCPS application, attaining long-lifetime of the high voltage (HV) pulsed capacitor is critical. The proposed system possesses low output current ripple to improve the lifetime of the pulsed capacitor. With the output voltage not being constant, modifications on the output current ripple equations for selecting an appropriate output inductor parameter is required. The proposed system employs a Constant Current - Constant Power (CC-CP) charging profile instead of a Constant-Current (CC) charging profile. Comparative evaluation of the CC-CP charging profile is presented to elucidate the advantage of employing CC-CP. Circuit simulation and experimental results from a hardware prototype are included to validate the design and to show the effectiveness of the proposed system.}, journal={2021 IEEE 12TH ENERGY CONVERSION CONGRESS AND EXPOSITION - ASIA (ECCE ASIA)}, author={Agarwal, Apoory and Prabowo, Yos and Bhattacharya, Subhashish}, year={2021}, pages={1068–1075} }
 @article{prabowo_iyer_bhattacharya_aeloiza_2021, title={Controller Design for the Rating-Proportional Current Sharing in Modular Hybrid Critical Load Substation Transformers}, ISSN={["2150-6078"]}, DOI={10.1109/ECCE-Asia49820.2021.9479434}, abstractNote={Partially rated power electronic modules (PEMs) can be interfaced with conventional line-frequency transformers (LFTs) to realize hybrid transformers (HTs). Hybrid transformers possess higher controllability as compared to conventional LFTs. In this paper, the parallel operation of multiple such hybrid transformer systems to form a modular architecture is proposed. The proposed system utilizes back-to-back power converter units with a lead/follower (L/F) control strategy. It entails reliable and resilient operations for critical load substation deployment during disasters and emergencies. The partially-rated power electronic module is exploited to achieve rating-proportional current sharing and voltage regulation. The controller design for the rating-proportional current sharing is presented. The DC-side stability of the back-to-back power converter unit with the proposed current sharing controller is assessed. Simulation results are included to validate the proposed concept.}, journal={2021 IEEE 12TH ENERGY CONVERSION CONGRESS AND EXPOSITION - ASIA (ECCE ASIA)}, author={Prabowo, Yos and Iyer, Vishnu Mahadeva and Bhattacharya, Subhashish and Aeloiza, Eddy}, year={2021}, pages={899–905} }
 @inproceedings{anurag_acharya_prabowo_gohil_kassa_bhattacharya_2018, title={An accurate calorimetric method for measurement of switching losses in silicon carbide (SiC) MOSFETs}, volume={2018-March}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85046966591&partnerID=MN8TOARS}, DOI={10.1109/apec.2018.8341245}, abstractNote={An accurate measurement of switching losses in SiC MOSFETs is necessary in order to design and evaluate the thermal performance of modern converter systems. Conventionally, electrical measurement methods, such as the double-pulse test (DPT) are used for calculating the hard-switching losses. However, with the advent of wide-bandgap devices, which have fast switching transients, it is rather difficult to capture the waveforms accurately during switching transitions, and consequently the measurement of switch loss suffers. This paper presents an accurate calorimetric method for measuring the switching losses. The conventional calorimetric measurement methods can accurately measure the device losses. However, the segregation of the conduction, turn-on and turn-off loss is not possible. This paper addresses this issue and proposes a method that can be used to determine individual loss components. The calorimetric test setup is described and a novel modulation scheme is introduced which enables the separation of turn-on and turn-off switching losses. The experimental test setup has been built and the method has been verified by measuring the losses of a Wolfspeed CMF10120D device.}, booktitle={Thirty-third annual ieee applied power electronics conference and exposition (apec 2018)}, author={Anurag, A. and Acharya, Sayan and Prabowo, Y. and Gohil, G. and Kassa, H. and Bhattacharya, S.}, year={2018}, pages={1695–1700} }