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X-WR-CALNAME:EE
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
TZOFFSETTO:+0530
TZNAME:IST
DTSTART:20240101T000000
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20240723T100000
DTEND;TZID=Asia/Kolkata:20240723T120000
DTSTAMP:20260527T021409
CREATED:20240723T030241Z
LAST-MODIFIED:20240723T030241Z
UID:241491-1721728800-1721736000@ee.iisc.ac.in
SUMMARY:Ph.D. Thesis Colloquium
DESCRIPTION:     Colloquium Announcement\n\nTitle of the Thesis        :  Power Swing Blocking Protection in Presence of Large Scale Grid Following PV Generation\nName of the Student  :  Meenu Jayamohan\nName of the Advisor   :  Dr. Sarasij Das\nDegree Registered       :  PhD (Eng.)\nDate and Time                :  23rd July\, 2024\, 10 AM\nLocation                            :  C 241\, MMCR\, Electrical Engg Dept\n\nAbstract:\nThe penetration of Inverter-Based Resources (IBRs) is increasing in power grids due to environmental concerns. The fault behaviour of IBR is quite different than that of Synchronous Generators (SGs). In addition\, IBRs usually do not have inherent inertia. As a result\, the existing protection schemes\, which are traditionally developed for SG-dominated systems\, can become ineffective. Stable power swings (SPS) and Unstable Power Swings (UPS) caused by oscillations generated during system disturbances may trigger undesired relay operations. Power swing Blocking (PSB) and Out-of-Step Tripping (OST) techniques have been employed to stop distance relays from malfunctioning during SPS and UPS\, respectively. PSB schemes commonly use the magnitude of the rate of change of positive sequence impedance (|dZ/dt|) for SPS detection. This research work focuses on the PSB protection issues in the\npresence of large-scale Grid-Following (GFOL) PV generation. A modified IEEE-39 bus system is used for all the studies presented in this thesis.\n\nAs the converter controls determine how PV generators behave during transients\, the behaviour of SGs used in conventional power systems differs significantly from that of PVs. As a result\, existing protection methods\, including PSB methods\, must be modified to protect the IBR-integrated power systems. This work examines how integrating GFOL PV generation affects power swing impedance (Z) trajectories and |dZ/dt|. The research reveals that the\nGFOL PV systems can significantly alter the Z trajectories observed during power swings compared to that of an SG-dominated system. The results presented demonstrate that the penetration of GFOL PV may increase the speed of Z trajectories and\, hence\, |dZ/dt|\, which may\, in turn\, cause maloperations of the PSB and OST functions. The findings emphasize the critical need to revisit and potentially adapt existing PSB and OST schemes to account for the growing presence of IBRs in power grids.\n\nIn the GFOL control strategy\, the injected power is controlled with respect to the grid voltages measured at the terminal by the Phase-Locked Loop (PLL). Considering a PLL bandwidth in the range of 2−15 Hz for a weak grid\, the PLL dynamics play a significant role in the power swing dynamics. In this work\, the impact of various types and control parameters of PLLs on |dZ/dt| and Z trajectories are analyzed using mathematical analysis. Synchronous Reference Frame PLL with additional Low pass filter (LSRF PLL)\, Multiple Reference Frame (MRF) PLL and Dual Second-Order Generalized Integrator (DSOGI) PLL are used for the study. The impacts of varying penetration of PV and relay locations are also investigated. This study shows that the PLL parameters and bandwidth influence the operation/maloperation of the PSB during SPS.\n\nDuring Fault Ride-Through (FRT)\, the PV system can provide additional reactive power to the grid to maintain the voltage at its terminals. This is achieved through the dynamic voltage or reactive power support and is provided in proportion to the drop in terminal voltage using the K-factor. The study also highlights the importance of considering the active power recovery rate to mitigate the oscillatory behaviour of IBR during the fault recovery process. The findings reveal that\, following fault removal\, the dynamic behaviour of inverters would be significantly influenced by both the K-factor and the active power recovery rate\, which may affect the power swing characteristics. This work emphasizes the need for a comprehensive understanding of how dynamic voltage support features and active power recovery interact with the power swing dynamics and influence PSB operation.\n\nAuto-Reclosing (AR) of a circuit breaker is a technique that attempts to re-energize the faulted line after a predetermined time delay. While IEEE Std C37.104-2012 provides guidelines for minimum AR dead time based on arc de-ionization\, these may not be sufficient for grids with a high penetration of IBRs. This work explores how varying the three-phase AR dead time can influence the severity of power swings that may occur after consecutive Low-Voltage Ride-Through (LVRT) events in a GFOL PV plant. This finding highlights the potential need to revise\nexisting minimum AR dead time standards for grids with high IBR penetration levels to ensure reliable system operation.\nThe studies presented in the previous sections show that existing impedance-based PSB methods might fail in the presence of GFOL PV generation. The lack of inherent inertia of the GFOL PV is one of the reasons behind the increased |dZ/dt| which may cause maloperation of the existing impedance-based PSB schemes. Hence\, a novel PSB method is proposed\, which uses nodal inertia to re-evaluate the |dZ/dt| values. The effectiveness of the proposed method is verified for both the SG-dominated system and the GFOL PV-integrated system using PSCAD simulations.
URL:https://ee.iisc.ac.in/event/ph-d-thesis-colloquium-3/
LOCATION:MMCR\, Hall C 241\, 1st floor\, EE department
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20240724T150000
DTEND;TZID=Asia/Kolkata:20240724T170000
DTSTAMP:20260527T021409
CREATED:20240723T092821Z
LAST-MODIFIED:20240723T092821Z
UID:241494-1721833200-1721840400@ee.iisc.ac.in
SUMMARY:Colloquium
DESCRIPTION:Title: Modelling\, Analysis and Control of Switched Reluctance Motors\n\nSpeaker: THIRUMALASETTY MOULI . of Ph.D. (Engg) in Electrical Engineering under Electrical Engineering \nDate/Time: Jul 24 / 15:00:00 \nLocation: Multi Media Class Room (MMCR)\, EE Department \nResearch Supervisor: Narayanan G \nAbstract:\nSwitched reluctance machine (SRM) is known for many advantages such as permanent magnet-free operation\, robust structure\, low rotor inertia\, low manufacturing cost\, and excellent fault-tolerant capability. Hence\, SRM has been adopted in many applications such as\, electric vehicles\, aerospace\, and robotics. Nonlinear characteristics and pulsations in torque developed are well-known problems\, rendering modelling and control of the SRM challenging. Hence this thesis focuses on the modelling\, analysis and control of switched reluctance machines. Current\, torque and speed control are all part of the scope of study. Conventionally rotors with laminations are used in SRM. However\, in applications where shaft temperatures are very high\, rotors made from a single piece of magnetic material are potential candidates. Solid-rotor and recently proposed slitted-rotor SRMs are prospective candidates for high temperature applications. Blocked rotor experiments and 3D finite element analyses reported show that the slitted-rotor SRM has lower core loss and higher torque density than the solid-rotor SRM. Further\, mutually coupled winding connection is shown to enhance the torque output of both solid- and slitted-rotor SRMs\, compared to conventional winding. Two new current control schemes are proposed in this research work. In the first part\, an extended horizon model-based predictive current controller is proposed for SRM. An analytical equation is reported for real-time computation of the optimal duty ratio to minimize the RMS error between the future current references and predicted currents over a horizon. The proposed controller demonstrates lower RMS error in current tracking and robustness to parameter variations\, with experimental validation on a laboratory prototype drive\, over an existing dead-beat predictive controller. Further\, a fixed-frequency\, model-independent predictive current control for SRM is proposed. Unlike traditional approaches\, this method does not require any pre-measured characteristics of the SRM. Instead\, it only requires two constants: the optimal value of equivalent inductance and the moving average window period. Hence this method eliminates the need for time consuming characterization experiments\, multi-dimensional lookup tables\, and offline curve fitting to model the flux-linkage characteristics of the SRM for current control. A high-performance torque control scheme for SRMs is presented\, incorporating a PI controller\, feedforward compensation\, high-frequency compensation\, and optimized gating functions. This controller achieves significant reduction in pulsating torque and outperforms state-of-the-art techniques across various operating conditions. Further improvement in performance is achieved through a novel PWM-based optimal predictive direct torque control scheme. In this work\, a cost function\, encompassing the instantaneous torque error and the RMS values of phase currents is formulated to be minimized. An analytical expression for the optimal duty ratio towards this objective is derived resulting in improved computational efficiency. This controller delivers improved torque tracking\, higher torque per ampere\, and lower sound pressure levels compared to existing methods. An experimental method for determining the moment of inertia and frictional torque characteristics of SRMs is proposed. Using these identified parameters\, a PI-based speed controller is designed and validated through simulations and experiments\, demonstrating its effectiveness in enhancing the performance of SRM drives. \nMeeting Link 
URL:https://ee.iisc.ac.in/event/colloquium/
LOCATION:Multi-Media Class Room (MMCR)\, EE Department (Hybrid mode)
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20240726T143000
DTEND;TZID=Asia/Kolkata:20240726T170000
DTSTAMP:20260527T021409
CREATED:20240726T085442Z
LAST-MODIFIED:20240726T085654Z
UID:241504-1722004200-1722013200@ee.iisc.ac.in
SUMMARY:Colloquium
DESCRIPTION:Investigations on Pulse Width Modulation Techniques for Split-Phase Induction Motor Drives \nSpeaker: LALGY GOPI . of Ph.D. (Engg) in Electrical Engineering under Electrical Engineering \nDate/Time: Jul 26 / 14:30:00 \nLocation: Multi Media Class Room (MMCR)\, EE Department Team Link \nResearch Supervisor: Narayanan G \nAbstract:\nA split-phase induction motor (SPIM) has two sets of identical three-phase windings separated by 30° in space\, typically fed by two- level voltage-source inverters. This configuration reduces the voltage rating of the windings and the DC-link voltage of the inverters. SPIMs are advantageous for high-power variable-speed applications due to reduced torque pulsations\, lower voltage-rated power converters\, higher torque per ampere\, and increased reliability. However\, they may require more semiconductor switches and circuitry. Although the winding structure avoids harmonic torques of the order 6k (k=1\, 3\, 5…)\, small voltages of harmonic order 6h±1 (h=1\,3\,5…) can cause large currents and increase copper loss. Properly designed pulse width modulation (PWM) techniques can improve SPIM drive performance by reducing stator copper loss and pulsating torque. In triangle comparison (TC) based PWM techniques for SPIM drives\, two sets of modulating signals\, which are phase-shifted by 30° from each other\, are compared against a common carrier wave. In contrast\, space vector (SV) based PWM techniques use the reference voltage vector to calculate the dwell times of each voltage vector\, which are then applied in a specific sequence. TC-based PWM techniques are renowned for their simplicity in implementation\, whereas SV-based techniques offer improved performance but come with increased computational complexity. While the unified understanding of these two types of PWM techniques is well established for three-phase induction motors\, this thesis aims to enhance the unified understanding between TC-based and SV-based PWM techniques for SPIM drives. Several SV-based PWM techniques have been introduced for SPIM drives to enhance harmonic performance. Four-dimensional 24-sector SVPWM techniques outperform 12-sector methods but are more complex to implement. This thesis performs a per-phase analysis of these techniques to develop an efficient implementation scheme. It evaluates and analyses the switching cycle averaged pole voltages to determine the common mode voltage (CMV) for each inverter\, showing that CMV relates to the fundamental voltage of different phases in different sectors. This leads to understanding the offset voltages needed for the two sets of three-phase sinusoidal modulating signals to generate equivalent signals for the two inverters driving the SPIM. Adding the derived zero-sequence signal to the sinusoidal modulating signals results in a computationally efficient implementation method. Equivalent carrier waves are derived based on the switching sequences\, requiring discontinuous carrier waves for improved harmonic performance. This carrier-based implementation significantly reduces computation time on a TMS320F28377S DSP platform. Experimental results of stator current waveforms under steady-state and various dynamic conditions from a 6kW\, 200V\, 50Hz SPIM drive are presented. A comparative study based on the stator flux ripple analysis is carried out to evaluate the stator current harmonic distortion and rms torque ripple. The comparison of analytically evaluated torque ripple factor\, simulated instantaneous torque ripple and harmonic spectra of torque are presented to validate the performance of different PWM techniques. The proposed discontinuous PWM method offers lower total harmonic distortion (THD) of stator current at high speeds. The equivalent modulating signals of the discontinuous PWM technique helped to evaluate the switching loss of semiconductor devices used. A comparison based on switching loss factor is carried to demonstrate the reduced switching loss due to this PWM technique. The discontinuous PWM technique is shown to have reduced switching losses at high power factors than the continuous PWM techniques with significantly low computational effort. An indirect field-oriented control scheme has also been presented to demonstrate the dynamic performance of the proposed implementation scheme. Two advanced bus-clamping pulse width modulation (ABCPWM) techniques are proposed in this thesis for SPIM drives to enhance their performance further. These techniques employ special switching sequences which apply the null vector once and one of the active vectors twice in each sub-cycle. Stator flux ripple-based analysis brings out the superior performance of the proposed special sequences over the conventional sequences at high modulation indices. Switching loss factor-based analysis shows that the inverter switching loss gets significantly reduced with the proposed PWM techniques at high power factors. Simulations and experiments on a 6kW\, 200V\, 50Hz SPIM drive show that the THD of stator current is reduced significantly at high speeds by the proposed PWM techniques at the same average switching frequency. In particular\, one of the proposed techniques improves the no-load stator current THD by 32% at rated frequency\, compared to a state-of-the-art SVPWM technique. \nTeam Link
URL:https://ee.iisc.ac.in/event/colloquium-2/
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20240729T160000
DTEND;TZID=Asia/Kolkata:20240729T170000
DTSTAMP:20260527T021409
CREATED:20240726T070414Z
LAST-MODIFIED:20240726T085523Z
UID:241502-1722268800-1722272400@ee.iisc.ac.in
SUMMARY:PhD Oral Examination of Subhas Chandra Das (ERP)
DESCRIPTION:Name of the Student\n\n\nSUBHAS CHANDRA DAS\n\n\n\n\n\n\n\n\nProgramme / Degree\n\n\nPh.D. (Engg) in Electrical Engg\n\n\n\n\nName of the Department of IISc\n\n\nElectrical Engineering\n\n\n\n\nName of the Research Supervisor\n\n\nNarayanan G\n\n\n\n\nDate & Time of the Oral Examination /Thesis Defense\n\n\n29.07.2024 /16:00:00 /Scheduled\n\n\n\n\nVenue / Mode\n\n\nMulti Media Class Room (MMCR)\, EE Department (Hybrid mode)\n\n\n\n\nTeam Link \nAbstract \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. \nALL ARE WELCOME
URL:https://ee.iisc.ac.in/event/phd-oral-examination-of-subhas-chandra-das-erp/
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20240730T113000
DTEND;TZID=Asia/Kolkata:20240730T123000
DTSTAMP:20260527T021409
CREATED:20240725T043607Z
LAST-MODIFIED:20240725T043808Z
UID:241497-1722339000-1722342600@ee.iisc.ac.in
SUMMARY:CBR/EE: Talk by Prof. Mathews Jacob
DESCRIPTION:Talk on Model based deep Learning for inverse problems in MRI: Beyond Algorithm Unrolling\n\nby Prof. Mathews Jacob\, University of Iowa\, USA.\n\non July 30th\, from 11.30 AM to 12.30 PM.\n\nVenue: CBR Auditorium\, CBR\, IISc.\n\nHost: Prof. Chandra Sekhar Seelamantula\, IISc\n\nAbstract: The reconstruction of MR images from highly undersampled Fourier measurements is a problem that has received a lot of attention in the past decade. Compressed sensing algorithms have been extensively employed in MRI to overcome the challenges associated with the slow nature of MRI acquisition. These methods offer guaranteed uniqueness\, fast convergence\, and stability properties. Model-based deep learning methods that combine imaging physics with learned regularization priors have emerged as more powerful alternatives for MR image recovery in recent years. The talk will introduce different flavors of physics-based deep learning methods and discuss the unique challenges associated with these schemes in high-dimensional settings. Novel memory efficient iterative algorithms that possess guarantees similar to compressive sensing\, while offering improved performance will be introduced. Energy models that allow sampling from the posterior distribution will also be discussed. The talk will draw upon our recent work\, available at https://cbig.iibi.uiowa.edu/publications\n\n\nBiography of the speaker: Mathews Jacob will be starting as a Professor in the Department of Electrical and Computer Engineering at the University of Virginia\, starting August 2024. He is currently a professor in the Department of Electrical and Computer Engineering and is heading the Computational Biomedical Imaging Group (CBIG) at the University of Iowa.  He obtained his B.Tech in Electronics and Communication Engineering from National Institute of Technology\, Calicut\, Kerala\, and his M.E in signal processing from the Indian Institute of Science\, Bangalore. He received his Ph.D. degree from the Biomedical Imaging Group at the Swiss Federal Institute of Technology. He was a Beckman postdoctoral fellow at the University of Illinois at Urbana Champaign.\nDr. Jacob is the recipient of the CAREER award from the National Science Foundation in 2009\, the Research Scholar Award from American Cancer Society in 2011\, and the Faculty Excellence Award for Research from University of Iowa in 2021. He is currently the associate editor of the IEEE Transactions on Medical Imaging and has served as the associate editor of IEEE Transactions on Computational Imaging from 2016-20. He was the senior author on two best paper awards (2015 & 2021) and one best machine learning paper award (2019) from IEEE ISBI. He was the general chair of IEEE International Symposium on Biomedical Imaging\, 2020. He was elected as a Fellow of the IEEE (2022) for contributions to computational biomedical imaging.
URL:https://ee.iisc.ac.in/event/cbr-ee-talk-by-prof-mathews-jacob/
LOCATION:CBR Auditorium\, CBR\, IISc.
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