@article{tripathi_mainali_madhusoodhanan_kadavelugu_vechalapu_hatua_2017, title={A Novel ZVS range enhancement technique of a high-voltage dual active bridge converter using series injection}, volume={32}, number={6}, journal={IEEE Transactions on Power Electronics}, author={Tripathi, A. K. and Mainali, K. and Madhusoodhanan, S. and Kadavelugu, A. and Vechalapu, K. and Hatua, K.}, year={2017}, pages={4231–4245} }
 @article{madhusoodhanan_mainali_tripathi_patel_kadavelugu_bhattacharya_hatua_2017, title={Harmonic Analysis and Controller Design of 15 kV SiC IGBT-Based Medium-Voltage Grid-Connected Three-Phase Three-Level NPC Converter}, volume={32}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85012231749&partnerID=MN8TOARS}, DOI={10.1109/tpel.2016.2582803}, abstractNote={Cascaded converters are generally used for medium-voltage (MV) grid-connected applications due to the limitation in the voltage rating of available silicon (Si) power devices. These converters find application in active power filters, STATCOM or as the active front end converters for solid state transformers at the distribution voltage levels. The high voltage wide bandgap semiconductor devices have enabled the grid connected operation of noncascaded converters. This results in high power density, less number of switching devices, and high efficiency for three-phase MV grid interface. This also results in control simplicity without the need for complex dc bus balancing algorithms otherwise needed for cascaded converters. However, such noncascaded, grid-connected converters introduce challenges in maintaining power quality at low currents. This paper investigates the harmonic performance and current distortion of the grid-connected, three-level neutral point clamped converter using 15 kV silicon carbide Insulated Gate Bipolar Transistor (IGBTs). A suitable control scheme for stable harmonic compensation is proposed. The challenges and control performance are explained through frequency domain analysis, simulations, and experimental validation on a developed prototype of the three-phase converter up to 4.16 kV, three-phase MV grid-connected operation.}, number={5}, journal={IEEE Transactions on Power Electronics}, author={Madhusoodhanan, S. and Mainali, K. and Tripathi, A. and Patel, D. and Kadavelugu, A. and Bhattacharya, Subhashish and Hatua, K.}, year={2017}, pages={3355–3369} }
 @inproceedings{madhusoodhanan_mainali_tripathi_kadavelugu_vechalapu_patel_bhattacharya_2016, title={Comparative evaluation of 15 kV SiC IGBT and 15 kV SiC MOSFET for 3-phase medium voltage high power grid connected converter applications}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85015416448&partnerID=MN8TOARS}, DOI={10.1109/ecce.2016.7854933}, abstractNote={The advent of high voltage (HV) wide band-gap power semiconductor devices has enabled the medium voltage (MV) grid tied operation of non-cascaded neutral point clamped (NPC) converters. This results in increased power density, efficiency as well as lesser control complexity. The multi-chip 15 kV/40 A SiC IGBT and 15 kV/20 A SiC MOSFET are two such devices which have gained attention for MV grid interface applications. Such converters based on these devices find application in active power filters, STATCOM or as active front end converters for solid state transformers. This paper presents an experimental comparative evaluation of these two SiC devices for 3-phase grid connected applications using a 3-level NPC converter as reference. The IGBTs are generally used for high power applications due to their lower conduction loss while MOSFETs are used for high frequency applications due to their lower switching loss. The thermal performance of these devices are compared based on device loss characteristics, device heat-run tests, 3-level pole heat-run tests, PLECS thermal simulation based loss comparison and MV experiments on developed hardware prototypes. The impact of switching frequency on the harmonic control of the grid connected converter is also discussed and suitable device is selected for better grid current THD.}, booktitle={ECCE 2016 - IEEE Energy Conversion Congress and Exposition, Proceedings}, author={Madhusoodhanan, S. and Mainali, K. and Tripathi, A. and Kadavelugu, A. and Vechalapu, K. and Patel, D. and Bhattacharya, Subhashish}, year={2016} }
 @article{madhusoodhanan_mainali_tripathi_kadavelugu_patel_bhattacharya_2016, title={Power Loss Analysis of Medium-Voltage Three-Phase Converters Using 15-kV/40-A SiC N-IGBT}, volume={4}, ISSN={["2168-6777"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84982806206&partnerID=MN8TOARS}, DOI={10.1109/jestpe.2016.2587666}, abstractNote={Medium-voltage (MV) silicon carbide (SiC) devices such as the 15-kV SiC N-insulated gate bipolar transistor (IGBT) have better thermal withstanding capability compared with silicon (Si)-based devices. These devices also have lower switching and conduction losses at high switching frequencies and high power levels, respectively. The maximum safe operating junction temperature for the 15-kV SiC IGBT is 175 °C. This enables high power density design of the MV converters using this device. Heat sink with forced air cooling is considered for dissipating the heat generated during converter operation. In this paper, the power loss analysis of three-phase MV converters based on 15-kV/40-A SiC N-IGBT is discussed. The converter thermal analysis is carried out based on the experimental loss data and the continuous heat-run test of the device. It is supported by analytical calculations, PLECS thermal simulations, and FEM simulations in COMSOL Multiphysics software. Hardware prototypes of the converters are developed and the experimental results support the analysis. Experimental results are given for both hard-switched grid-connected converter and soft-switched dual active bridge converter. The paper mainly focuses on the semiconductor losses in the converter.}, number={3}, journal={IEEE JOURNAL OF EMERGING AND SELECTED TOPICS IN POWER ELECTRONICS}, author={Madhusoodhanan, Sachin and Mainali, Krishna and Tripathi, Awneesh Kumar and Kadavelugu, Arun and Patel, Dhaval and Bhattacharya, Subhashish}, year={2016}, month={Sep}, pages={902–917} }
 @article{tripathi_mainali_patel_kadavelugu_hazra_bhattacharya_hatua_2015, title={Design Considerations of a 15-kV SiC IGBT-Based Medium-Voltage High-Frequency Isolated DC-DC Converter}, volume={51}, ISSN={["1939-9367"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84937876123&partnerID=MN8TOARS}, DOI={10.1109/tia.2015.2394294}, abstractNote={A dual active bridge (DAB) is a zero-voltage switching (ZVS) high-power isolated dc-dc converter. The development of a 15-kV SiC insulated-gate bipolar transistor switching device has enabled a noncascaded medium voltage (MV) isolated dc-dc DAB converter. It offers simple control compared to a cascaded topology. However, a compact-size high frequency (HF) DAB transformer has significant parasitic capacitances for such voltage. Under high voltage and high dV/dT switching, the parasitics cause electromagnetic interference and switching loss. They also pose additional challenges for ZVS. The device capacitance and slowing of dV/dT play a major role in deadtime selection. Both the deadtime and transformer parasitics affect the ZVS operation of the DAB. Thus, for the MV-DAB design, the switching characteristics of the devices and MV HF transformer parasitics have to be closely coupled. For the ZVS mode, the current vector needs to be between converter voltage vectors with a certain phase angle defined by deadtime, parasitics, and desired converter duty ratio. This paper addresses the practical design challenges for an MV-DAB application.}, number={4}, journal={IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS}, author={Tripathi, Awneesh K. and Mainali, Krishna and Patel, Dhaval C. and Kadavelugu, Arun and Hazra, Samir and Bhattacharya, Subhashish and Hatua, Kamalesh}, year={2015}, pages={3284–3294} }
 @inproceedings{madhusoodhanan_tripathi_mainali_patel_kadavelugu_bhattacharya_2015, title={Distributed Energy Storage Device integration with three phase distribution grid using a Transformerless Intelligent Power Substation}, volume={2015-May}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84937940471&partnerID=MN8TOARS}, DOI={10.1109/apec.2015.7104422}, abstractNote={The advent of SiC devices has resulted in the development of 3-phase, Medium Voltage (MV) grid tied Solid State Transformers (SSTs). One such SST is the 100 kVA Transformerless Intelligent Power Substation (TIPS) based on 15 kV SiC IGBTs and 1200 V SiC MOSFETs which interconnects the 13.8 kV distribution grid with the 480 V utility grid. TIPS has an ac-dc-dc-ac multi-module configuration. The availability of 800 V dc and 480 V ac terminals in the system allows for the integration of Distributed Energy Storage Devices (DESDs) with the 13.8 kV MV grid. These DESDs store the energy derived from the renewable sources like solar, wind and wave. The complex nature of the overall system makes the power flow control very challenging during integration. This paper investigates the steady state and transient behavior of the TIPS system when integrated with a battery model representing the DESD. Complete system simulation is carried out using the switching model of the converters along with the dynamic model of the battery and a feeder model similar to IEEE-34 bus system. Experimental verification is done on TIPS prototype at scaled down voltage and power levels.}, number={May}, booktitle={Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC}, author={Madhusoodhanan, S. and Tripathi, A. and Mainali, K. and Patel, D. and Kadavelugu, A. and Bhattacharya, Subhashish}, year={2015}, pages={670–677} }
 @inproceedings{tripathi_madhusoodhanan_mainali_kadavelugu_patel_bhattacharya_hatua_2015, title={Grid connected CM noise considerations of a three-phase multi-stage SST}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84961872947&partnerID=MN8TOARS}, DOI={10.1109/icpe.2015.7167873}, abstractNote={Solid State Transformer (SST) is an alternative to the conventional distribution transformer for smart grid applications. By employing a compact Medium-Frequency (MF) transformer for isolation, the SST has merits on size and weight. It also provides flexible utilization as a FACTS component. The switching converters are a potential source of Common-Mode (CM) and HF EMI noises. These noises are more nuisance in a SiC device based SST which switches at a high dV/dT at the Medium-Voltage (MV) level resulting in high CM voltages. The SST floating metalic surfaces such as heatsink and the output must be grounded for safety and smooth operation. However there are various significant low impedance paths present, including the parasitics of the compact transformer, which may conduct CM noise to the grid. The generated CM noise may affect the controls. This paper presents the CM and grounding challenges in the multistage integration of a three-phase SST system based on 15kV SiC IGBTs termed as Transformerless Intelligent Power Substation (TIPS). The TIPS interfaces MV 13.8kV and LV 480V grids using MV ac-dc, MV to LV dc-dc dual active bridge and LV dc-ac inverter stages. A study on the CM noise in the TIPS and a passive filter solution for its attenuation is presented in this paper. A time domain simulation considering the passive filter specification is also presented. The experimental results for line to line 3.64kV MV grid integration are presented. A LV prototype is used to verify the complete grounding and the CM choke design at a scaled-down condition.}, booktitle={9th International Conference on Power Electronics - ECCE Asia: "Green World with Power Electronics", ICPE 2015-ECCE Asia}, author={Tripathi, A. and Madhusoodhanan, S. and Mainali, K. and Kadavelugu, A. and Patel, D. and Bhattacharya, Subhashish and Hatua, K.}, year={2015}, pages={793–800} }
 @inproceedings{tripathi_mainali_madhusoodhanan_patel_kadavelugu_hazra_bhattacharya_hatua_2015, title={MVDC microgrids enabled by 15kV SiC IGBT based flexible three phase dual active bridge isolated DC-DC converter}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84963593747&partnerID=MN8TOARS}, DOI={10.1109/ecce.2015.7310462}, abstractNote={The Dual Active Bridge (DABC) dc-dc converter is an integral part of the recently popular Medium-Voltage (MV) dc micro-grid application due to its high-power density. The advent of 15kV SiC IGBT and 10kV SiC MOSFET, has enabled a non-cascaded MV and Medium-Frequency (MF) DABC converter which is expected to have higher MTBF than the cascaded H-bridge topology due to relatively small number of switches. A composite DABC three-level three-phase topology earlier proposed for MV-MF application, has dual secondary side bridges to meet the rated load conditions. The duty-ratio control of the primary and the independent operation of dual secondary bridges as a single active bridge, can be utilized to solve the light load ZVS problem. This paper presents flexible operating modes of this MV DABC for ZVS and higher efficiency. The MV DABC simulations are presented to bring out the advantages of this topology in wide range load and voltage-ratio conditions. This paper reports 8kV experimental validation of this DABC while using 15kV/40A SiC IGBTs on the MV side.}, booktitle={2015 IEEE Energy Conversion Congress and Exposition, ECCE 2015}, author={Tripathi, A. and Mainali, K. and Madhusoodhanan, S. and Patel, D. and Kadavelugu, A. and Hazra, S. and Bhattacharya, Subhashish and Hatua, K.}, year={2015}, pages={5708–5715} }
 @inproceedings{kadavelugu_mainali_patel_madhusoodhanan_tripathi_hatua_bhattacharya_ryu_grider_leslie_2015, title={Medium voltage power converter design and demonstration using 15 kV SiC N-IGBTs}, volume={2015-May}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84937857287&partnerID=MN8TOARS}, DOI={10.1109/apec.2015.7104530}, abstractNote={This paper summarizes the different steps that have been undertaken to design medium voltage power converters using the state-of-the-art 15 kV SiC N-IGBTs. The 11 kV switching characterization results, 11 kV high dv/dt gate driver validation, and the heat-run test results of the SiC IGBT at 10 kV, 550 W/cm2 (active area) have been recently reported as individual topics. In this paper, it is attempted to link all these individual topics and present them as a complete subject from the double pulse tests to the converter design, for evaluating these novel high voltage power semiconductor devices. In addition, the demonstration results of two-level H-Bridge and three-level NPC converters, both at 10 kV dc input, are being presented for the first-time. Lastly, the performance of two-chip IGBT modules for increased current capability and demonstration of three-level poles, built using these modules, at 10 kV dc input with sine-PWM and square-PWM modulation for rectifier and dc-dc stages of a three-phase solid state transformer are presented.}, number={May}, booktitle={Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC}, author={Kadavelugu, A. and Mainali, K. and Patel, D. and Madhusoodhanan, S. and Tripathi, A. and Hatua, K. and Bhattacharya, Subhashish and Ryu, S.-H. and Grider, D. and Leslie, S.}, year={2015}, pages={1396–1403} }
 @inproceedings{madhusoodhanan_mainali_tripathi_patel_kadavelugu_bhattacharya_hatua_2015, title={Performance evaluation of 15 kV SiC IGBT based medium voltage grid connected three-phase three-level NPC converter}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84963604269&partnerID=MN8TOARS}, DOI={10.1109/ecce.2015.7310184}, abstractNote={Cascaded converters are generally used for Medium Voltage (MV) grid connected applications due to the limitation in the voltage rating of available Silicon (Si) power devices. These converters find application in Active Power Filters, STATCOM or as Active Front End Converters for Solid State Transformers at the distribution voltage levels. The wide bandgap semiconductor devices have enabled the grid connected operation of non-cascaded converters. This results in high power density, less number of switching devices, high efficiency and control simplicity for three-phase MV grid interface. 15 kV SiC IGBT is one such device which can be switched at 5 kHz between MV and zero levels with forced air cooling. However, this device in a grid connected non-cascaded converter introduces few additional challenges which are analyzed in this paper. The paper investigates the performance of the grid connected converter using 15 kV SiC IGBT through simulations and experiments till 4.16 kV, 3-phase operation. The concerned areas of study are Total Harmonic Distortion (THD) at low currents, effect of practical sensor-feedback path errors, effect of switching ripple on the distribution transformer, effect of filter parasitic capacitance and elimination of high common mode current.}, booktitle={2015 IEEE Energy Conversion Congress and Exposition, ECCE 2015}, author={Madhusoodhanan, S. and Mainali, K. and Tripathi, A. and Patel, D. and Kadavelugu, A. and Bhattacharya, Subhashish and Hatua, K.}, year={2015}, pages={3710–3717} }
 @article{madhusoodhanan_tripathi_patel_mainali_kadavelugu_hazra_bhattacharya_hatua_2015, title={Solid-State Transformer and MV Grid Tie Applications Enabled by 15 kV SiC IGBTs and 10 kV SiC MOSFETs Based Multilevel Converters}, volume={51}, ISSN={["1939-9367"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84937880113&partnerID=MN8TOARS}, DOI={10.1109/tia.2015.2412096}, abstractNote={Medium-voltage (MV) SiC devices have been developed recently which can be used for three-phase MV grid tie applications. Two such devices, 15 kV SiC insulated-gate bipolar transistor (IGBT) and 10 kV SiC MOSFET, have opened up the possibilities of looking into different converter topologies for the MV distribution grid interface. These can be used in MV drives, active filter applications, or as the active front end converter for solid-state transformers (SSTs). The transformerless intelligent power substation (TIPS) is one such application for these devices. TIPS is proposed as a three-phase SST interconnecting a 13.8 kV distribution grid with a 480 V utility grid. It is an all SiC device-based multistage SST. This paper focuses on the advantages, design considerations, and challenges associated with the operation of converters using these devices keeping TIPS as the topology of reference. The efficiency of the TIPS topology is also calculated using the experimentally measured loss data of the devices and the high-frequency transformer. Experimental results captured on a developed prototype of TIPS along with its measured efficiency are also given.}, number={4}, journal={IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS}, author={Madhusoodhanan, Sachin and Tripathi, Awneesh and Patel, Dhaval and Mainali, Krishna and Kadavelugu, Arun and Hazra, Samir and Bhattacharya, Subhashish and Hatua, Kamalesh}, year={2015}, pages={3343–3360} }
 @inproceedings{madhusoodhanan_mainali_tripathi_kadavelugu_patel_bhattacharya_2015, title={Thermal design considerations for medium voltage power converters with 15 kV SiC IGBTs}, booktitle={Ieee international symposium on power electronics for distributed}, author={Madhusoodhanan, S. and Mainali, K. and Tripathi, A. and Kadavelugu, A. and Patel, D. and Bhattacharya, S.}, year={2015}, pages={265–272} }
 @inproceedings{madhusoodhanan_tripathi_mainali_kadavelugu_patel_bhattacharya_hatua_2015, title={Three-phase 4.16 kV medium voltage grid tied AC-DC converter based on 15 kV/40 a SiC IGBTs}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84963600033&partnerID=MN8TOARS}, DOI={10.1109/ecce.2015.7310594}, abstractNote={Recently, with the emergence of Wide Bandgap semiconductor devices having higher blocking voltage capabilities and higher switching speed, ac-dc converters for Medium Voltage (MV) and Low Voltage (LV) dc micro-grid applications are becoming popular. In this paper, the first time experimental demonstration of such a 3-phase, isolated ac-dc power converter based on the newly developed 15 kV/40 A SiC IGBT is presented for 4.16 kV ac distribution grid interface. The presented converter consists of two bidirectional stages - the 4.16 kV ac to 8 kV dc front end converter followed by an 8 kV dc to 480 V dc dual active bridge converter with high frequency isolation. These stages are switched at 5 kHz and 10 kHz respectively. The converter design is presented along with experimental validation on a prototype at 9.6 kW.}, booktitle={2015 IEEE Energy Conversion Congress and Exposition, ECCE 2015}, author={Madhusoodhanan, S. and Tripathi, A. and Mainali, K. and Kadavelugu, A. and Patel, D. and Bhattacharya, Subhashish and Hatua, K.}, year={2015}, pages={6675–6682} }
 @inproceedings{kadavelugu_bhattacharya_2014, title={Design considerations and development of gate driver for 15 kV SiC IGBT}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84900410469&partnerID=MN8TOARS}, DOI={10.1109/apec.2014.6803505}, abstractNote={The 15 kV SiC N-IGBT is the state-of-the-art high voltage power semiconductor device developed by Cree. The SiC IGBT is exposed to a peak stress of 10-11 kV in power converter systems, with punch-through turn-on dv/dt over 100 kV/μs and turn-off dv/dt about 35 kV/μs. Such high dv/dt requires ultralow coupling capacitance in the dc-dc isolation stage of the gate driver for maintaining fidelity of the signals on the control-supply ground side. Accelerated aging of the insulation in the isolation stage is another serious concern. In this paper, a simple transformer based isolation with a toroid core is investigated for the above requirements of the 15 kV IGBT. The gate driver prototype has been developed with over 100 kV dc insulation capability, and its inter-winding coupling capacitance has been found to be 3.4 pF and 13 pF at 50 MHz and 100 MHz respectively. The performance of the gate driver prototype has been evaluated up to the above mentioned specification using double-pulse tests on high-side IGBT in a half-bridge configuration. The continuous testing at 5 kHz has been performed till 8 kV, and turn-on dv/dt of 85 kV/μs on a buck-boost converter. The corresponding experimental results are presented. Also, the test methodology of evaluating the gate driver at such high voltage, without a high voltage power supply is discussed. Finally, experimental results validating fidelity of the signals on the control-ground side are provided to show the influence of increased inter-winding coupling capacitance on the performance of the gate driver.}, booktitle={Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC}, author={Kadavelugu, A. and Bhattacharya, Subhashish}, year={2014}, pages={1494–1501} }
 @inproceedings{tripathi_mainali_patel_kadavelugu_hazra_bhattacharya_hatua_2014, title={Design considerations of a 15kV SiC IGBT enabled high-frequency isolated DC-DC converter}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84906658515&partnerID=MN8TOARS}, DOI={10.1109/ipec.2014.6869673}, abstractNote={The advent of the 15kV SiC IGBT device has made a single series stage medium-voltage (MV) and high-frequency (HF) DC-DC Dual Active Bridge (DAB) converter application viable. The Y: Y/Δ three-phase DAB is a high-power isolated DC-DC converter based on three-level neutral-point clamped (NPC) on the MV side. A MV/HF transformer used in the DAB, has significant parasitic capacitances, which cause ringing in the DAB current under high dV/dT switching. In addition, the converters need sufficient dead-time between complimentary switches to avoid possibility of any shoot-through. The length of the dead-time depends on switching characteristics. Both the dead-time and transformer parasitics affect zero voltage switching (ZVS) performance of the DAB. Thus, the DAB design has to be closely coupled with the switching characteristics of the devices and MV/HF transformer parasitics. For the ZVS mode, the current-vector needs to be between converter voltage vectors with a certain margins defined by dead-time, parasitics and desired duty ratio of three-level MV converter. This paper addresses these design challenges for the MV DAB application.}, booktitle={2014 International Power Electronics Conference, IPEC-Hiroshima - ECCE Asia 2014}, author={Tripathi, A. and Mainali, K. and Patel, D. and Kadavelugu, A. and Hazra, S. and Bhattacharya, Subhashish and Hatua, K.}, year={2014}, pages={758–765} }
 @inproceedings{kadavelugu_bhattacharya_ryu_brunt_grider_leslie_2014, title={Experimental switching frequency limits of 15 kV SiC N-IGBT module}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84906675160&partnerID=MN8TOARS}, DOI={10.1109/ipec.2014.6870034}, abstractNote={This paper presents extensive experimental switching characteristics of a state-of-the-art 15 kV SiC N-IGBT (0.32 cm2 active area) up to 10 kV, 10 A and 175°C. The influence of the thermal resistance of the module package, cooling mechanism, and the increased energy loss with temperature are investigated for determining the switching frequency limits of the IGBT. Detailed FEM analysis is conducted for extracting the thermal resistance of each layer in the 15 kV module from the IGBT junction to the base plate, and then down to the ambient. Using this thermal information and the experimental switching data, the inductive switching frequency limits are analytically evaluated for liquid and air cooling cases with 660 W/cm2 and 550 W/cm2 power dissipation densities respectively, considering 150°C as maximum junction temperature. The air cooling power dissipation density of the 15 kV IGBT is experimentally validated using a dc-dc boost converter at 10 kV, 6.4 kW output and 550 W/cm2 under steady state operating conditions. The gate resistances used for the entire experiments are RG(ON) = 20 Ω and RG(OFF) = 10 Ω.}, booktitle={2014 International Power Electronics Conference, IPEC-Hiroshima - ECCE Asia 2014}, author={Kadavelugu, A. and Bhattacharya, Subhashish and Ryu, S.-H. and Brunt, E. Van and Grider, D. and Leslie, S.}, year={2014}, pages={3726–3733} }
 @inproceedings{madhusoodhanan_tripathi_kadavelugu_hazra_patel_mainali_bhattacharya_hatua_2014, title={Experimental validation of the steady state and transient behavior of a transformerless intelligent power substation}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84900439832&partnerID=MN8TOARS}, DOI={10.1109/apec.2014.6803809}, abstractNote={Transformerless Intelligent Power Substation (TIPS) is a 3-phase Solid State Transformer (SST) to interconnect 13.8 kV, 3-phase distribution grid with 480 V, 3-phase utility grid. The concept of TIPS was proposed as a solid state alternative to the conventional line frequency transformer. Various advantages of TIPS include unity power factor operation, controlled bidirectional power flow capability, reactive power compensation to improve grid voltage profile under necessary conditions, high frequency d.c link based isolation, small size and weight due to Silicon Carbide (SiC) devices, and renewable energy integration. This paper focuses on the system integration and hardware demonstration of the functions of TIPS at lower voltage and power levels. In addition, it focuses on various operational strategies like smooth start-up/shut-down scheme, stability criteria at the high voltage d.c link, fault protection for the various modules of TIPS, power quality improvement and performance under sudden load transients. Experimental results are given for each module separately and for fully integrated TIPS.}, booktitle={Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC}, author={Madhusoodhanan, S. and Tripathi, A. and Kadavelugu, A. and Hazra, S. and Patel, D. and Mainali, K. and Bhattacharya, Subhashish and Hatua, K.}, year={2014}, pages={3477–3484} }
 @inproceedings{madhusoodhanan_tripathi_patel_mainali_kadavelugu_hazra_bhattacharya_hatua_2014, title={Solid State Transformer and MV grid tie applications enabled by 15 kV SiC IGBTs and 10 kV SiC MOSFETs based multilevel converters}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84906706613&partnerID=MN8TOARS}, DOI={10.1109/ipec.2014.6869800}, abstractNote={Recently, medium voltage SiC devices have been developed which can be used for grid tie applications at medium voltage. Two such devices - 15 kV SiC IGBT and 10 kV SiC MOSFET have opened up the possibility of looking into different converter topologies for medium voltage distribution grid interface. These can be used in medium voltage drives, active filter applications or as the active front end converter for Solid State Transformers (SST). Transformer-less Intelligent Power Substation (TIPS) is one such application for these devices. TIPS is proposed as a 3-phase SST interconnecting 13.8 kV distribution grid with 480 V utility grid. The Front End Converter (FEC) of TIPS is made up of 15 kV SiC IGBTs. This paper focuses on the advantages, design considerations and challenges associated with the operation of converters using these devices keeping TIPS as the topology of reference.}, booktitle={2014 International Power Electronics Conference, IPEC-Hiroshima - ECCE Asia 2014}, author={Madhusoodhanan, S. and Tripathi, A. and Patel, D. and Mainali, K. and Kadavelugu, A. and Hazra, S. and Bhattacharya, Subhashish and Hatua, K.}, year={2014}, pages={1626–1633} }
 @inproceedings{kadavelugu_bhattcharya_baliga_ryu_grider_palmour_2014, title={Zero voltage switching characterization of 12 kV SiC N-IGBTs}, DOI={10.1109/ispsd.2014.6856048}, abstractNote={This paper reports experimental zero voltage switching (ZVS) characteristics of the state-of-the-art 12 kV SiC N-IGBTs with 2 μm and 5 μm field-stop buffer layer thicknesses. Extensive results up to 7 kV and 150°C are presented for both IGBTs with and without an external snubber capacitor. The 12 kV SiC IGBTs have been found to have significantly larger magnitude of turn-off current bump in comparison to the results reported for the commercial (≤ 6.5 kV) Si IGBTs, because of deep punch-through design. The turn-off current shape is majorly influenced by slower voltage rise before the punch-through, followed by faster voltage rise after the punch-through voltage. In addition, the difference in current gain resulting from different buffer layer thicknesses has considerable effect on the overall switching behavior and energy loss of the two IGBTs. A detailed explanation of all these phenomena is presented along with the considerations for power converter design while employing the ZVS technique with these ultrahigh voltage IGBTs.}, booktitle={Proceedings of the international symposium on power semiconductor}, author={Kadavelugu, A. and Bhattcharya, S. and Baliga, B. J. and Ryu, S. H. and Grider, D. and Palmour, J.}, year={2014}, pages={350–353} }
 @inproceedings{patel_kadavelugu_madhusoodhanan_bhattacharya_hatua_leslie_ryu_grider_agarwal_2013, title={15 kV SiC IGBT based three-phase three-level modular-leg power converter}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84891113691&partnerID=MN8TOARS}, DOI={10.1109/ecce.2013.6647132}, abstractNote={The 15kV /20A, 4H-SiC n-IGBT is the state-of-the-art high voltage power semiconductor device. The transformerless intelligent power substation (TIPS) [1] for 13.8kV grid interfacing is built using this device. It is proposed to use a three-phase, three-level, diode clamped topology as the front end converter (FEC) in TIPS. A modular-leg structure has been employed for FEC. In modular-leg structure, each phase-leg will have its own DC-link capacitors and a low inductance bus-bar. However, modular-leg structure adds complexity in DC bus over-load protection, which is studied in this paper. Experimental results of modular-leg converter at 3kV DC link voltage and scale down prototype of AC switch for DC bus fault protection are presented.}, booktitle={2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013}, author={Patel, D.C. and Kadavelugu, A. and Madhusoodhanan, S. and Bhattacharya, Subhashish and Hatua, K. and Leslie, S. and Ryu, S.-H. and Grider, D. and Agarwal, A.}, year={2013}, pages={3291–3298} }
 @inproceedings{kadavelugu_bhattacharya_ryu_brunt_grider_agarwal_leslie_2013, title={Characterization of 15 kV SiC n-IGBT and its application considerations for high power converters}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84891115267&partnerID=MN8TOARS}, DOI={10.1109/ecce.2013.6647027}, abstractNote={The 4H-SiC n-IGBT is a promising power semiconductor device for medium voltage power conversion. Currently, Cree has successfully built 15 kV n-IGBTs. These IGBTs are pivotal for the smart grid power conversion systems and medium voltage drives. The need for complex multi-level topologies or series connected devices can be eliminated, while achieving reduced power loss, by using the SiC IGBT. In this paper, characteristics of the 15 kV n-IGBT have been reported for the first time. The turn-on and turn-off transitions of the 15 kV, 20 A IGBT have been experimentally evaluated up to 11 kV. This is highest switching characterization voltage ever reported on a single power semiconductor device. The paper includes static characteristics up to 25 A (forward) and 12 kV (blocking). The dependency of the power loss with voltage, current and temperature are provided. In addition, the basic converter design considerations using this ultrahigh voltage IGBT for high power conversion applications are presented. Also, a comparative evaluation is reported with an IGBT with thicker field-stop buffer layer as a means to show flexibility in choosing the IGBT design parameters based on the power converter frequency and power rating specification. Finally, power loss comparison of the IGBTs and MOSFET is provided to consummate the results for a complete reference.}, booktitle={2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013}, author={Kadavelugu, A. and Bhattacharya, Subhashish and Ryu, S.-H. and Brunt, E. Van and Grider, D. and Agarwal, A. and Leslie, S.}, year={2013}, pages={2528–2535} }
 @inproceedings{madhusoodhanan_cho_kadavelugu_bhattacharya_grider_ryu_agarwal_leslie_2013, title={Comparative evaluation of SiC devices for PWM buck rectifier based active front end converter for MV grid interface}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84891099153&partnerID=MN8TOARS}, DOI={10.1109/ecce.2013.6647097}, abstractNote={In this paper a new method for implementation of a 3-phase medium voltage rectifier is presented for Active Front End grid interface applications. A current source based PWM buck rectifier with Silicon Carbide (SiC) devices, different from the traditional GTO based current source rectifier, is used to grid tie with 3-phase, 4.16 kV grid. The power level considered is 100 kVA. Simplicity of construction, very high efficiency, better input line current control and small volume are the main advantages of this system. Due to low switching losses compared with traditional GTOs, PWM operation of the rectifier at higher switching frequencies is possible. A detailed simulation shows the validity of the proposed method. Efficiency comparison of the PWM Buck rectifier with 10 kV/10 A SiC MOSFET and 15 kV/20 A SiC IGBT as the active devices is also presented. Low voltage hardware prototype based high frequency switching validation is also carried out.}, booktitle={2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013}, author={Madhusoodhanan, S. and Cho, Y. and Kadavelugu, A. and Bhattacharya, Subhashish and Grider, D. and Ryu, S.-H. and Agarwal, A. and Leslie, S.}, year={2013}, pages={3034–3041} }
 @inproceedings{kadavelugu_bhattacharya_ryu_grider_agarwal_leslie_2013, title={Evaluation of 15 kV SiC N-IGBT and P-IGBT for complementary inverter topology with zero dv/dt stress on gate drivers}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84891060348&partnerID=MN8TOARS}, DOI={10.1109/ecce.2013.6647026}, abstractNote={The complementary inverter topology with N-channel and P-channel switching devices is a known method of eliminating dv/dt stress on the gate drivers. In the Silicon (Si) based applications, this advantage did not gain wide attention due to inherent inefficiency of the P-type devices, and the matured technology to handle the dv/dt stress levels produced by these devices with highest blocking voltage rating of 6.5 kV. On the other hand, the ultrahigh voltage (> 12 kV) SiC devices generate high dv/dt due to their high speed switching. This requires meticulous design of the gate drivers for reliable operation of high power converters. As an easy alternative, the option of using a complementary inverter has been explored in this paper. Both N-channel and P-channel IGBTs with blocking capability of 15 kV have been investigated for the complementary structure. The N-IGBT is found to be more efficient than the P-IGBT, based on the experimental switching characterization results at 6 kV and 5 A. The results of the 3 kV half-bridge complementary inverter prototype are also presented. The option of trade-off of P-IGBT field-stop buffer layer parameters (thickness, doping concentration and lifetime) for better switching characteristics can provide the use of complementary topologies a promising alternative for high power conversion.}, booktitle={2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013}, author={Kadavelugu, A. and Bhattacharya, Subhashish and Ryu, S.-H. and Grider, D. and Agarwal, A. and Leslie, S.}, year={2013}, pages={2522–2527} }
 @inproceedings{kadavelugu_wang_bhattacharya_huang_2012, title={Auxiliary power supply for Solid State Transformers}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84870892973&partnerID=MN8TOARS}, DOI={10.1109/ecce.2012.6342647}, abstractNote={In contrast to traditional 60 Hz transformer, solid state transformer (SST) offers power flow control, integration of renewables and maintaining grid stability in high renewable penetration scenario. Like a typical power converter, SST requires low voltage (24 V dc) power for its control and sensing circuits. In running condition, this power is derived from its low voltage dc bus at 400 V. But it is challenging to derive it during start-up, because the only source available during start-up is the distribution grid at 7.2 kV, 60 Hz. Due to high input voltage (7.2 kV, 60 Hz), deriving a control supply of about 150 W, even for just start-up duration of about 200 ms, presents a novel power electronics problem. In this paper, two solutions have been proposed to address this issue, by taking a 20 kVA, 6.5 kV Si IGBT and 15 kV SiC MOSFET based SSTs as the reference converters. The first solution is generic and is based on storing the required start-up energy in a dc capacitance. This is based on developing a cost-effective high voltage switch using low voltage IGBTs with self-driven functionality. The second solution, applicable only to SST topologies with high voltage ac capacitive filter, is to tap the energy from the capacitor itself. The fundamental constraints considered for both the solutions are practical feasibility at high voltage (7.2 kV ac or over 10 kV dc), power loss, size, weight and cost-effectiveness. Experimental validation of extracting continuous power for the IGBT gate driver ICs from the snubber is presented with 200 V input. And, the results of the auxiliary power derivation from the filter capacitor are shown with 5.7 kV ac input.}, booktitle={2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012}, author={Kadavelugu, A. and Wang, G. and Bhattacharya, Subhashish and Huang, A.}, year={2012}, pages={1426–1432} }
 @inproceedings{wang_she_wang_kadavelugu_zhao_huang_yao_2011, title={Comparisons of different control strategies for 20kVA solid state transformer}, DOI={10.1109/ecce.2011.6064196}, abstractNote={This paper presents and compares different control strategies for 20kVA silicon IGBT based solid state transformer (SST). The SST has a cascaded seven level rectifier stage, three output parallel Dual Active Bridge (DAB) DC/DC stage and an inverter stage. The voltage of the three high voltage capacitors must be balanced for the safe operation of the IGBTs, however, the mismatch of power devices parameters and variance of high frequency transformer leakage inductance of the DAB stage will cause voltage unbalance for these capacitors as well as the power unbalance of the three output parallel DAB stages. This paper analyzed these effects and discussed the limitations and merits for several different control strategies. The newly proposed control strategy for the SST has been determined as the most suitable strategy in terms of performance and simplicity. Simulation and experiment results are presented to validate the analysis.}, booktitle={2011 IEEE Energy Conversion Congress and Exposition (ECCE)}, author={Wang, G. Y. and She, X. and Wang, F. and Kadavelugu, A. and Zhao, T. F. and Huang, A. and Yao, W. X.}, year={2011}, pages={3173–3178} }
 @inproceedings{kadavelugu_baliga_bhattacharya_das_agarwal_2011, title={Zero voltage switching performance of 1200V SiC MOSFET, 1200V silicon IGBT and 900V CoolMOS MOSFET}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-81855177139&partnerID=MN8TOARS}, DOI={10.1109/ecce.2011.6064006}, abstractNote={This paper evaluates zero voltage switching (ZVS) performance of 1200 V SiC MOSFET with respect to 1200 V silicon IGBTs (PT and FST) and 900 V CoolMOS MOSFET. The converter topology chosen for the study is a dual active bridge (DAB) dc-dc converter. Typically, in a high power DAB converter, ZVS is achieved through LC resonance of leakage inductance of the high frequency transformer and external capacitance across the drain and source (or collector and emitter for IGBTs) terminals. However, the SiC MOSFET offers a completely new set of parameters for ZVS when compared to its Silicon counterparts. In this paper, it is shown that a high power converter is possible with ZVS turn-on as well as low-loss turn-off using SiC MOSFETs, with out adding any external capacitance. The unique features of the SiC MOSFET that helps in achieving this are its CDS value, the variation of CDS with drain voltage, and low current turn-off time. The corresponding parameters of the silicon IGBTs and CoolMOS devices are presented to show the uniqueness of the SiC MOSFET. Simulation results corresponding to a 6 kW, 100 kHz DAB converter are presented with the SiC MOSFET as well as the silicon IGBTs and CoolMOS to provide a comparative ZVS performance.}, booktitle={IEEE Energy Conversion Congress and Exposition: Energy Conversion Innovation for a Clean Energy Future, ECCE 2011, Proceedings}, author={Kadavelugu, A. and Baliga, V. and Bhattacharya, Subhashish and Das, M. and Agarwal, A.}, year={2011}, pages={1819–1826} }