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X-ORIGINAL-URL:https://ee.iisc.ac.in
X-WR-CALDESC:Events for EE
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TZID:Asia/Kolkata
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TZOFFSETFROM:+0530
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DTSTART:20230101T000000
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20230927T160000
DTEND;TZID=Asia/Kolkata:20230927T170000
DTSTAMP:20260919T145617
CREATED:20230926T041251Z
LAST-MODIFIED:20230926T041251Z
UID:241091-1695830400-1695834000@ee.iisc.ac.in
SUMMARY:PhD Thesis Colloquium - Subhas Chandra Das\, EE (ERP)
DESCRIPTION:Title: Experimental Investigations on Switching Behaviour of Traction-Grade IGBTs over Wide Operating Conditions\n\nSubhas Chandra Das (PhD -ERP) \n\nSupervisor: Prof. G. Narayanan\nDate and Time: 27 Sep 2023 (Wednesday)\, 4 pm – 5 pm\nVenue: MMCR\, EE Department (Hybrid mode)\n\nTeams meeting link:\n\nAbstract\n\n\nInsulated gate bipolar transistors (IGBTs) are the dominant power semiconductor devices in high power applications\, such as\, locomotive traction and megawatt-level renewable energy systems. Power electronic converters in such applications are expected to have a long-life span of about 20-30 years. Hence\, efficiency and reliability of these converters are very important. IGBT switching behavior has a direct influence on both power conversion efficiency and system reliability. \nThe various switching characteristics parameters of IGBTs\, which are available in the respective device datasheets\, are limited to certain operating conditions. For an example\, the switching characteristic parameters are available for only one or two DC link voltages; however\, in applications such as diesel-electric locomotives\, IGBTs have to operate over a wide range of the DC link voltages. Similarly\, the characteristic parameters are available at only one or two junction temperatures (e.g. 25 oC and 125 oC); but\, the IGBTs in traction and wind energy systems have to operate over wide range of temperatures including sub-zero ambient temperatures. \nIn this work\, switching behavior of IGBTs of four different makes are studied experimentally over a wide range of operating conditions. The load current is considered upto 1.667p.u.\, where 1 p.u corresponds to the rated current of the IGBTs. The range of DC link voltage considered is from 0.571 p.u. to 1.321p.u.\, where 1.0 p.u. is the nominal voltage of the application. The junction temperature range is considered from -35 oC to +125 oC. The following are the major highlights of the research work: \n1. Generation of experimental data on switching behavior of IGBTs over wide range of operating conditions as mentioned above. \n2. The experimental data\, which are generated\, complement the technical information available in device datasheets. \n3. The experimental investigation are carried out on four traction-grade IGBTs of different makes and of comparable ratings to ensure that the findings of the study are applicable to reasonable cross-section of the available commercial devices. \n4. Experimental study on the switching behavior of an IGBT converter leg\, having top and bottom devices of two different makes\, and its comparison with the switching behavior of a converter leg\, having complementary devices of the same make. \n5. Experimental study of the rise and fall times of the device switching voltages and currents\, both during turn-on and turn-off\, over the complete range of operating conditions. \n6. Evaluation of turn-on and turn-off switching energy losses as functions of load current\, DC link voltages and junction temperatures\, which are valid over the complete operating range. \n7. Experimental study of reverse recovery characteristics of anti-parallel diode of IGBTs with varying DC link voltage\, load current and junction temperatures. \n8. Experimental investigation on the effect of variations in DC link voltage\, load current and junction temperatures on device peak stress parameters\, namely\, peak device voltage\, peak device current\, peak rate of change of device voltage\, and peak rate of change of device current. \n9. Experimental study of sub-intervals of the turn-on switching delay\, turn-off switching delays and parameters related to the switching delay intervals over the complete operating range. \n10. Correlation of the various turn-on and turn-off switching parameters with junction temperatures based on the experimental data generated. \n11. Study of the consistency of the above correlations across different traction-grade devices of comparable ratings and different makes. \n12. Critical review of various thermo-sensitive electrical parameters (TSEPs) already reported in literature. \n13. Identification of new TSEPs that can be obtained from the measured gate-emitter voltage during switching delay times. \n\n\nALL ARE WELCOME
URL:https://ee.iisc.ac.in/event/phd-thesis-colloquium-subhas-chandra-das-ee-erp/
LOCATION:Multi-Media Class Room (MMCR)\, EE Department (Hybrid mode)
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DTSTART;TZID=Asia/Kolkata:20230929T100000
DTEND;TZID=Asia/Kolkata:20230929T110000
DTSTAMP:20260919T145617
CREATED:20230925T092359Z
LAST-MODIFIED:20230925T092359Z
UID:241089-1695981600-1695985200@ee.iisc.ac.in
SUMMARY:[EE Thesis Defense] - "Speech Dereverberation Using Autoregressive Models of Sub-band Envelopes"\, Anurenjan\,
DESCRIPTION:Title Dereverberation of Speech Using Autoregressive Models of Sub-band Envelopes. \nSpeaker Anurenjan P. R.  \nFaculty Advisor: Dr. Sriram Ganapathy \nExaminer : Prof. Umesh S. (IITM) \nAbstract \nThe speech-based technologies are radically changing the way we interact with systems and how we access information. In many of these applications\, the users prefer to interact with the system through a far-field microphone without the nuance of a handheld or body-worn device. Examples of such applications are automated meeting analysis\, speech-based dictation systems\, hands-free interfaces for controlling consumer-products\, IoT\, virtual assistants in mobile phones and smart speakers. The major challenge in capturing speech from the far-field is the degradation of the signal quality due to reverberation. Reverberation refers to the delayed and weighted summation of the direct component of the speech signal with the reflected versions. This talk is focused on developing methods for speech dereverberation\, i.e.\, restoring the functional quality of reverberated speech\, using autoregressive models of sub-band envelopes. signal analysis  \nThe technique of frequency domain linear prediction (FDLP) is used for finding the autoregressive model parameters.  The FDLP is the frequency domain dual of the conventional Time Domain Linear Prediction (TDLP). Just as the TDLP estimates the spectrum of a signal\, the FDLP estimates the temporal envelopes of the signal using an autoregressive model. We apply the FDLP approach to the sub-bands of speech signal that are distributed in the mel-scale. \nThis talk will describe two broad directions for addressing issues in the far-field speech using the FDLP approach. In the first part of the talk\, we explore a front-end design for automatic speech recognition (ASR) applications that suppresses the reverberation artifacts in the FDLP envelope. In the second part of the thesis\, we develop a speech enhancement model using the envelope and carrier decomposition given by the FDLP technique. \nIn the design of the ASR front end\, I will discuss a novel approach for 3-D acoustic modeling framework\, where the spatio-spectral features from all the sub-band channels are extracted. The features that are input to the 3-D CNN are extracted by modeling the signal peaks in the spatio-spectral domain using a multi-variate autoregressive modeling approach. In the subsequent part of this section\, I will describe a neural model for speech dereverberation using the long-term sub-band envelopes of speech. The neural dereverberation model estimates the envelope gain\, which when applied to reverberant signals\, allows the suppression of the late reflection components. The de-reverberated envelopes are used for feature extraction in speech recognition. The key novelty in this model is the joint learning of the reverberation and the ASR system. In these ASR experiments using the proposed framework\, we illustrate significant performance gains over previously proposed front ends.  \nThe second part of the thesis deals with the FDLP based speech dereverberation for enhancement applications\, where the goal is to restore the audible quality of the speech signal. For this task\, we decompose the sub-band speech signal into the constituent envelope and carrier part. A dereverberation neural model is designed that attempts to enhance the envelope and carrier signals jointly. Further\, joint learning of the speech enhancement model with the end-to-end ASR model is proposed with a single neural framework. The proposed model therefore can generate improved audio quality and provide robust representations for far-field ASR. Finally\, I will illustrate the subjective quality improvement of the audio signal as well as the improvement in ASR performance obtained by the proposed envelope-carrier model.     \nAcknowledgement This work was partly supported by project grants from Samsung Research India\, Bangalore and the College of Engineering\, Trivandrum\, Kerala.  \nBio Mr. Anurenjan is a PhD student at the LEAP lab\, Electrical Engineering\, IISc. He is also working as Assistant Professor in Government Engineering College\, Idukki. Mr. Anurenjan completed his Bachelors in Technology from Government Engineering College\, Barton Hill\, Trivandrum\, Kerala in 2006 and his Masters in Technology from College of Engineering\, Trivandrum\, Kerala in 2008. He joined the LEAP lab as a PhD candidate under AICTE-QIP program in the year 2017. He hails from Trivandrum district of Kerala. He is interested in signal processing\, machine learning and speech processing. Mr. Anurenjan is a member of IEEE SPS and the ISCA. During his free hours\, Mr. Anurenjan likes to play badminton and goes for swimming.  \n——- \nAll are invited. Coffee/Tea will be served before the talk. 
URL:https://ee.iisc.ac.in/event/ee-thesis-defense-speech-dereverberation-using-autoregressive-models-of-sub-band-envelopes-anurenjan/
LOCATION:MMCR\, Hall C 241\, 1st floor\, EE department
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DTSTART;TZID=Asia/Kolkata:20230929T160000
DTEND;TZID=Asia/Kolkata:20230929T173000
DTSTAMP:20260919T145617
CREATED:20230913T053937Z
LAST-MODIFIED:20230918T040821Z
UID:241060-1696003200-1696008600@ee.iisc.ac.in
SUMMARY:[EE Faculty Colloquium] Overview of Research on Pulse Width Modulation\, Motor Control and Electrical Machines
DESCRIPTION:Title: Overview of Research on Pulse Width Modulation\, Motor Control and Electrical Machines at EE\, IISc \nSpeaker: Prof. G. Narayanan\, Professor\, Electrical Engineering\, IISc \nVenue: MMCR\, EE & Online Teams link \nTime: 4pm\, 29 September 2023 \nAbstract:\nThe talk will provide a brief overview of research on pulse width modulation (PWM)\, motor control and electrical machines\, which the speaker has been a part of\, in the department of electrical engineering over the past 2-3 decades. Research highlights will be presented on the following aspects: \n\nSpace vector based PWM for motor drives and four-quadrant voltage-source converters\nOffline optimized PWM for induction motor drives\nHigh power converters for motor drives and active front-end converters\nPower-electronic control of induction motor and its variants\nEffect of inverter dead-time and its compensation\nInduction motor drive-based emulation of wind turbine\nPower electronic based emulation of electrical machines\n\nRecent and on-going activities on the following with be discussed briefly: \n\nPermanent-magnet-free high-performance motors based on reluctance principle\nHigh-speed switched reluctance motors and contact-free electromagnetic bearings\nMulti-disciplinary initiatives involving multiple departments\, multiple institutions / organizations across technical domains\n\nSpeaker’s Bio:\nG. Narayanan received his BE from College of Engineering Guindy\, Anna University\, Chennai\, in 1992; MTech from IIT Kharagpur in 1994; and PhD from IISc in 2000. He has been on the faculty of EE\, IISc\, since August 2003. He researches in the areas of power electronics\, motor drives and electrical machines. He has taught / has been teaching multiple courses in these broad domains.\n\n* All are welcome * \n—————————————-
URL:https://ee.iisc.ac.in/event/ee-faculty-colloquium-overview-of-research-on-pulse-width-modulation-motor-control-and-electrical-machines/
LOCATION:MMCR\, Hall C 241\, 1st floor\, EE department
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