@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{tripathi_mainali_madhusoodhanan_yadav_vechalapu_bhattacharya_2016, title={A MV intelligent gate driver for 15kV SiC IGBT and 10kV SiC MOSFET}, volume={2016-May}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84973596466&partnerID=MN8TOARS}, DOI={10.1109/apec.2016.7468153}, abstractNote={This paper presents an Intelligent Medium-voltage Gate Driver (IMGD) for 15kV SiC IGBT and 10kV SiC MOSFET devices. The high voltage-magnitude and high dv/dt(> 30kV/μs) of these MV SiC devices, pose design challenge in form of isolation and EMI. This problem is solved by development of a <; 1pF isolation capacitance power-supply. But due to applied high stress, smaller short-circuit withstand time and the criticality of the application, these devices need to be monitored, well protected, active gate-driven and safely shut-down. This paper presents an EMI hardened IMGD built around a CPLD, sensing and optical interfacing unit. It provides advanced gate-driving, added protection and optically isolated state-monitoring features. The device operating conditions such as module temperature and Vds(on) can be data-logged. They can be used for diagnosis/prognosis purposes such as to predict failure and safely shut-down the system. This paper describes the functionality of different building blocks. The 15kV SiC IGBT has higher second switching slope above its punch-through level which is moderated without increasing losses by using digitally controlled active gate-driving. The shoot-through protection time can be reduced below withstand time by advanced gate driving. Soft turn-on and over-current triggered gate-voltage reduction helps reducing blanking time and quick turn-off reduces the protection response time. In this paper, the IMGD is high side tested at 5kV with device state monitoring on. The active gate-driving is tested at 6kV.}, booktitle={Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC}, author={Tripathi, A. and Mainali, K. and Madhusoodhanan, S. and Yadav, A. and Vechalapu, K. and Bhattacharya, Subhashish}, year={2016}, pages={2076–2082} }
 @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} }
 @inproceedings{mainali_madhusoodhanan_tripathi_vechalapu_de_bhattacharya_2016, title={Design and evaluation of isolated gate driver power supply for medium voltage converter applications}, volume={2016-May}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84973644285&partnerID=MN8TOARS}, DOI={10.1109/apec.2016.7468085}, abstractNote={The commercial gate drivers are available upto 6.5 kV IGBTs. With the advances in the SiC, power devices rated beyond 10 kV are being researched. These devices will have use on medium voltage power converters. Commercial gate drivers rated for such high voltages are not available. These power devices have very high dv/dts (30-100 kV/μs) at switching transitions. Such high dv/dts bring in challenges in the gate driver design. The isolation stage of the gate power supply needs to have very low coupling capacitance to limit the high frequency circulating currents from reaching the gate driver control circuits. Also, the isolation stage has to be designed with insulation several times higher than the peak system voltage level. In this paper, design, development and evaluation of the gate power supply for medium voltage level applications have been investigated. Several isolation transformer designs have been investigated and optimum design, with very low coupling capacitance ≈ 0.5 pF, has been identified and used in the gate driver design. Experimental characterization of the transformer has been done. The performance of the gate driver power supply has been evaluated in several MV power converters, using 10 kV SiC MOSFETs.}, booktitle={Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC}, author={Mainali, K. and Madhusoodhanan, S. and Tripathi, A. and Vechalapu, K. and De, A. and Bhattacharya, Subhashish}, year={2016}, pages={1632–1639} }
 @inproceedings{tripathi_madhusoodhanan_mainali_vcchalapu_chattopadhyay_bhattacharya_2016, title={Enabling DC microgrids with direct MV DC interfacing DAB converter based on 15 kV SiC IGBT and 15 kV SiC MOSFET}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85015358617&partnerID=MN8TOARS}, DOI={10.1109/ecce.2016.7855078}, abstractNote={The 15 kV SiC IGBT and 15 kV SiC MOSFET have been recently developed to enable non-cascaded high-frequency (HF) MV converters. Such direct MV DC interfacing Dual Active Bridge (DAB) converter is getting popular for DC micro-grid application due to higher efficiency, higher power-density and higher MTBF over the cascaded DAB topology. The high dv/dt in these devices on hard-switching with their inherent parasitics, causes increased EMI and switching loss. The suitability of the two family of SiC devices for an application, depends on the switching frequency, load range and magnitude of power, operating temperature and converter power density. This paper compares the two devices for a MV DAB application for dc micro-grid based on simulation and also with supporting MV side converter experiments up to 10kV DC bus and under 5–20kHz switching frequencies.}, booktitle={ECCE 2016 - IEEE Energy Conversion Congress and Exposition, Proceedings}, author={Tripathi, A. and Madhusoodhanan, S. and Mainali, K. and Vcchalapu, K. and Chattopadhyay, R. and Bhattacharya, Subhashish}, year={2016} }
 @inproceedings{madhusoodhanan_mainali_tripathi_vechalapu_bhattacharya_2016, title={Medium voltage (≥ 2.3 kV) high frequency three-phase two-level converter design and demonstration using 10 kV SiC MOSFETs for high speed motor drive applications}, volume={2016-May}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84973597838&partnerID=MN8TOARS}, DOI={10.1109/apec.2016.7468066}, abstractNote={High speed variable frequency motor drives are required for marine applications, compressors for oil and gas industries, wind energy generation systems etc. Traditionally, low voltage high speed motor drives are used in such applications. This results in large currents at high power levels leading to large copper loss in the motor winding. Therefore, medium voltage (MV) drives are being considered. The silicon (Si) based MV drives need gears to increase the speed due to low switching frequency operation of Si devices in the converter. Gears reduce both efficiency and power density. With the development of 10 kV SiC MOSFET, high switching frequency at MV is possible, which has enabled the scope of high power density MV direct drive variable speed controlled motors. In this paper, the design of a three-phase, 2-level, ≥ 2.3 kV MV, high frequency converter based on 10 kV SiC MOSEFT is explained. Performance analysis is presented along with experimental demonstration.}, booktitle={Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC}, author={Madhusoodhanan, S. and Mainali, K. and Tripathi, A. and Vechalapu, K. and Bhattacharya, Subhashish}, year={2016}, pages={1497–1504} }
 @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} }
 @inproceedings{tripathi_madhusoodhanan_mainali_vechalapu_bhattacharya_2016, title={Series injection enabled full ZVS light load operation of a 15kV SiC IGBT based dual active half bridge converter}, volume={2016-May}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84973607429&partnerID=MN8TOARS}, DOI={10.1109/apec.2016.7467976}, abstractNote={The 15kV SiC IGBT has second higher dv/dt turn-off slope above the punch-through level resulting in EMI. Increasing gate-resistance also slows the first dv/dt causing increased switching loss. A snubber capacitor assisted turn-off solves these issues for a high power dual active bridge (DAB) converter based on this device, but the light load turn-on ZVS becomes hard to achieve. This paper proposes a series injection enabled triangular current shaping at the light load turn-off instant in the DAB to create enough current for smooth free-wheeling transition of device voltage during the dead-time period for ZVS turn-on. The proposed technique is validated through simulations followed by experiments on a medium voltage DAB hardware implementation of this technique.}, booktitle={Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC}, author={Tripathi, A. and Madhusoodhanan, S. and Mainali, K. and Vechalapu, K. and Bhattacharya, Subhashish}, year={2016}, pages={886–892} }
 @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} }
 @inproceedings{vechalapu_tripathi_mainali_baliga_bhattacharya_2015, title={Soft switching characterization of 15 kV SiC n-IGBT and performance evaluation for high power converter applications}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84963579482&partnerID=MN8TOARS}, DOI={10.1109/ecce.2015.7310246}, abstractNote={The 15 kV SiC IGBT with 2 μm and 5 μm field-stop buffer layer thicknesses are two state of the art HV SiC devices. These 15 kV SiC IGBTs generate high dv/dt with two slopes in punch through and non-punch through regions. To design 15 kV SiC IGBT with reduced dv/dt and single slope dv/dt similar to 10-15 kV SiC MOSFET, requires significantly larger drift epitaxial layer thickness and it increases the size and cost of the 15 kV SiC IGBT. This paper presents the zero voltage switching (ZVS) characteristics of 15 kV SiC N-IGBTs to reduce the dv/dt at switching pole along with reduction in the switching losses and increase in the switching frequency limits with external snubber capacitor. The ZVS characteristics are reported up to 9 kV dc bus voltage at 25°C and 150°C for both IGBTs. This paper also reports continuous mode experimental demonstration of zero voltage switching (ZVS) of 5 μm 15 kV IGBT in a medium voltage half bridge converter up to 7 kV dc bus voltage and calculation of power dissipation per IGBT module and its comparison of switching frequency limits with hard switching of half bridge converter.}, booktitle={2015 IEEE Energy Conversion Congress and Exposition, ECCE 2015}, author={Vechalapu, K. and Tripathi, A. and Mainali, K. and Baliga, B.J. and Bhattacharya, Subhashish}, year={2015}, pages={4151–4158} }
 @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{mainali_madhusoodhanan_tripathi_patel_bhattacharya_2015, title={Start-up scheme for solid state transformers connected to medium voltage grids}, volume={2015-May}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84937922109&partnerID=MN8TOARS}, DOI={10.1109/apec.2015.7104473}, abstractNote={The development of the high voltage wideband gap semiconductor SiC power devices has enabled the solid state transformer (SST) technology in connecting a medium voltage grid to a low voltage grid. Though, these power devices have superior loss and switching characteristics compared to Si power devices, they have limited inrush current handling capability. The large inrush currents that flow into the SST from the grids when commissioning the SST system can be detrimental to the SiC devices. A proper start-up scheme is required to address this issue. Reported literatures on SST are focused on different topologies and their control aspects. This paper is focused in developing the safe start-up schemes for SST system connecting medium voltage grid to low voltage grid. The paper presents the simulation results and experimental verifications of the proposed SST start-up scheme.}, number={May}, booktitle={Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC}, author={Mainali, K. and Madhusoodhanan, S. and Tripathi, A. and Patel, D. and Bhattacharya, Subhashish}, year={2015}, pages={1014–1021} }
 @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{tripathi_mainali_patel_bhattacharya_hatua_2014, title={Control and performance of a single-phase dual active half bridge converter based on 15kV SiC IGBT and 1200V SiC MOSFET}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84900413266&partnerID=MN8TOARS}, DOI={10.1109/apec.2014.6803599}, abstractNote={A single-phase Dual Active Half Bridge (DAHB) DC-DC converter topology is evaluated for medium voltage (MV) application. A 15kV SiC-IGBT based three-level half-bridge is connected to the high voltage (HV) primary side of a high frequency (HF) transformer operating at 10kHz link-frequency. A 1200V SiC-MOSFET based two-level H-bridge is connected on the low voltage (LV) secondary side. This topology requires fewer switches and is suitable for MV application particularly with high step-down ratio where HF transformer may have considerable parasitics. It offers advantage of half blocking voltage requirement per device on the HV side and a simpler transformer saturation protection implementation. This paper also presents a robust D-Q based inner current control technique for the single phase DAB. The converters on both HV and LV side of the DAHB, can also be switched in 60° zero quasi-square mode to eliminate 3rd harmonic voltage. The square and 60° modes of operation are compared. The DAHB converter topology and controls are validated with simulation results followed by experimental results.}, booktitle={Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC}, author={Tripathi, A. and Mainali, K. and Patel, D. and Bhattacharya, Subhashish and Hatua, K.}, year={2014}, pages={2120–2125} }
 @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{mainali_tripathi_patel_bhattacharya_challita_2014, title={Design, measurement and equivalent circuit synthesis of high power HF transformer for three-phase composite dual active bridge topology}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84900457176&partnerID=MN8TOARS}, DOI={10.1109/apec.2014.6803331}, abstractNote={High voltage high frequency (HF) transformer provides the isolation between high and low dc link voltages in dual active bridge (DAB) converters. Such DAB converters are finding wide applications as an intermediate DC-DC converter in transformerless intelligent power substation (TIPS), which is proposed as an alternative for conventional distribution-transformer connecting 13.8 kV and 480 V grids. The design of HF transformer used in DAB stage of such application is very challenging considering the required isolation, size and cost. In this paper, the specification generation, design, characterization, test and measurement results on a 10kHz HF transformer are presented, highlighting the above challenges.}, booktitle={Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC}, author={Mainali, K. and Tripathi, A. and Patel, D.C. and Bhattacharya, Subhashish and Challita, T.}, year={2014}, pages={342–349} }
 @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{tripathi_mainali_patel_bhattacharya_hatua_2013, title={Closed loop D-Q control of high-voltage high-power three-phase dual active bridge converter in presence of real transformer parasitic parameters}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84891099254&partnerID=MN8TOARS}, DOI={10.1109/ecce.2013.6647446}, abstractNote={Three-phase Dual Active Bridge (DAB) Y : Y/Δ composite topology offers advantage of nearly sinusoidal converter-currents without pulse-width modulation, which can be utilized for D-Q mode control implementation. D-Q control is smooth and regulates power-factor of DAB which ensures zero voltage switching (ZVS) operation of the DAB converter at wide-range loading conditions. A practical DAB high-frequency transformer has certain limitations like small leakage-inductance, limited magnetizing-inductance and unwanted parasitic-capacitance's which distort the primary-side currents at the rated high-voltage because primary inter-turn capacitance is high in per-unit for a real 100kW transformerdesign. This problem can be solved by using secondary currents and estimated magnetizing current to emulate primary-currents for D-Q control. Parasitic are introduced in the LV TIPS set-up by adding lumped elements to emulate real HV-transformer with objective to test the controls in worst case scenario. This paper proposes the solutions for some of the practical implementation problems of the control algorithm for the DAB.}, booktitle={2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013}, author={Tripathi, A.K. and Mainali, K. and Patel, D. and Bhattacharya, Subhashish and Hatua, K.}, year={2013}, pages={5488–5495} }