Department of Electrical Engineering

Indian Institute of Technology Palakkad&nbsp;(IIT Palakkad or IIT PKD) is a public autonomous&nbsp;engineering&nbsp;and&nbsp;research&nbsp;institute located in&nbsp;Palakkad,&nbsp;Kerala. It was&nbsp;one of the five new&nbsp;IITs&nbsp;proposed in the&nbsp;2014 Union budget of India. The campus was inaugurated on 3 August 2015. The institute has 94 faculty, 978 students, and 63 non-teaching staffs.

IT Palakkad currently offers four-year Bachelor of Technology (B.Tech) and two years MS programmes in 8 different engineering disciplines including&nbsp;Computer Science, Electrical, Mechanical, Civil among others.

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IIT Palakkad

A distance relay mal-operating during power swing has been very frequently attributed to triggering the events leading to a power system blackout. The existing methods rely on settings being proposed by the operators, which in turn are calculated from exhaustive offline simulation studies. Apart from being cumbersome, these methods are not adaptable to the changes in the power system. As such, the requirement of an algorithm to identify power swings based on local measurements and without settings cannot be emphasized enough. This paper examines the effectiveness of one such method to detect power swings based on continuous impedance measurements, and identifies the cases where the same is found to be lacking. Necessary modifications are suggested to make the algorithm overcome the identified shortcomings. The benefit of this method is that it employs a very simplistic approach in analyzing the locus of the impedance trajectory to identify power swings and the suggested improvements do not require any additional functional blocks to improve its effectiveness. The effectiveness of the suggested approach is validated on Western Systems Coordinating Council (WSCC) 9-bus system. The results show improved performance in terms of power swing identification over wide range of swing frequency. © 2018 IEEE.

World University root node

2018 IEEMA Engineer Infinite Conference, eTechNxT 2018

An improved setting-free power swing blocking scheme using local end information

This paper suggests a conceptual framework for dynamic stress assessment in power transmission system to support wide area early warning system (WAEWS). Two indices termed as 'relative center of reactive power voltage reference (RCORPVR) and relative center of active power speed reference (RCOAPSR) are introduced to access stress level of a power system. The suggested technique is validated on IEEE-39 bus test system. The proposed framework can be integrated with the existing energy management system (EMS). This will enhance overall situational awareness of the power system, which is very much essential to prevent cascaded outages leading to blackouts. © 2017 IEEE.

2017 14th IEEE India Council International Conference, INDICON 2017

Dynamic Stress Assessment in Power Transmission Network to Support Wide Area Early Warning System

This paper presents a decentralized-approach-based wide-area back-up protection scheme to identify the faulted line in a power transmission network. The proposed scheme divides the whole power system under study into different protection zones (PZs) corresponding to generator bus(es). Furthermore, a 'gain in momentum' (GIM) index at each generator bus is used to minimize the search set. This information helps in reducing the search space to the PZ corresponding to the generator bus with highest GIM following a fault. This area is termed as a vulnerable protection zone (VPZ). Once the VPZ is identified, positive-sequence voltage magnitudes of each bus within the VPZ are monitored to locate the bus closest to the fault (BCF). Finally, reactive power-flow information of each line connected to the BCF is used to identify the faulted line. The performance of the proposed scheme is extensively validated on the Western System Coordinating Council-9 bus system, the IEEE-39 bus New England system, and 246-bus North India Grid using the Power System Simulation for Engineering. The test results indicate that the proposed scheme is highly effective for the WABP of transmission lines. © 2007-2012 IEEE.

IEEE Systems Journal

A New Decentralized Approach to Wide-Area Back-Up Protection of Transmission Lines

This paper proposes a Front-end Matrix based Bidirectional Solid-State-Transformer (SST) for a nanogrid having both AC and DC power distribution networks. A single-phase Matrix-converter (MC) is used to convert the line-frequency grid voltage to High-Frequency AC (HFAC). The MC is modulated using a modified Sinusoidal-Pulse-Width Modulation (SPWM) scheme. The HFAC voltage is then fed to a Current-Doubler-Rectifier (CDR) to form a stiff Low-Voltage DC (LVDC) bus. A bidirectional-converter is used to facilitate energy interaction in between the AC and DC buses of the nanogrid. Simulation of the proposed SST scheme is performed and the results are presented to verify the theoretical analysis. A comparative analysis of the proposed topology with other relevant topologies is also presented. The proposed topology has comaparatively high reliability, exhibits high power density and superior input side power quality. © 2018 IEEE.

Proceedings of 2018 IEEE International Conference on Power Electronics, Drives and Energy Systems, PEDES 2018

A Matrix-Based Solid-State-Transformer for A Hybrid Nanogrid

Modular Multilevel Converters (MMC) are emerging as a promising technology for high power conversion at high voltage levels. When frequency droop regulated MMC is used as a front-end converter to integrate wind farm into HVDC grid, variation in the fundamental operating frequency results in the change of circulating current harmonic frequencies. Due to this variation in harmonic frequencies, conventional time-domain based repetitive controller with fixed sampling frequency will fail to alleviate the circulating harmonic currents. In this paper, a spatial repetitive controller (SRC) based circulating current controller is proposed to effectively attenuate the harmonics in the circulating currents even under variable frequency operation of MMC, to improve its steady-state performance. SRC has a strong periodic disturbance rejection capability, therefore, can effectively alleviate the circulating harmonic currents and is independent of the fundamental AC line frequency of the MMC. A scaled-down laboratory prototype of a single phase, 5-level MMC is developed to experimentally validate the performance of the proposed control strategy. Experimental results are presented to substantiate the improvement in steady-state performance of the MMC with the proposed spatial repetitive based circulating current controller. © 2018 IEEE.

Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC

Spatial repetitive controller for improved steady state performance of droop regulated modular multilevel converter in wind farm application

In the present work, tin oxide and Ag doped tin oxide thin films were fabricated using jet nebulizer spray pyrolysis technique and the photocatalytic properties of the prepared samples were analyzed by studying the photodegradation of methylene blue dye under visible light. The rate constant value is 0.0254 and 0.0193 min(-1) for SnO2 and SnO2:Ag films, respectively. The results confirm that SnO2:Ag film exhibits better photocatalytic activity compared to SnO2 film. The XRD study shows that the film has tetragonal rutile structure of SnO2. The mechanism involved in the enhancement of the photocatalytic efficacy of the SnO2 film due to the addition of Ag is explained on the basis of photoluminescence, FESEM, AFM and optical studies.

JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS

Ag activated SnO2 films for enhanced photocatalytic dye degradation against toxic organic dyes

Conventional voltage-source inverters used for induction motor drives generate a hexagonal space vector structure. In the overmodulation range, the hexagonal space vector structure generates low-order harmonics in the phase voltage resulting in low-order torque ripple in the motor. Inverter topologies with an octadecagonal (18 sided) space vector structure eliminate fifth-, seventh-, eleventh-, and thirteenth-order harmonics from the phase voltage, and hence, the dominant sixth- and twelfth-order torque ripple generation is eliminated. Octadecagonal space vector structures proposed in the past require multiple dc sources, which makes four-quadrant operation of the drive system difficult and costly. In this paper, the formation of a multilevel nine-concentric octadecagonal space vector structure using a single dc source is proposed. Detailed experimental results, using open-loop V/f control and rotor field-oriented control, are presented to validate the effectiveness of the proposed drive scheme. © 2017 IEEE.

IEEE Transactions on Power Electronics

A Low-Order Harmonic Elimination Scheme for Induction Motor Drives Using a Multilevel Octadecagonal Space Vector Structure With a Single DC Source

Orthogonal frequency-division multiplexing (OFDM) is a multi-carrier modulation scheme that has been employed in many communication standards. The performance of OFDM is severely degraded by the presence of impulsive noise caused due to different nonlinear devices and power amplifiers. In this paper, we propose a novel automated framework to detect and remove impulse noise in OFDM system. The proposed method is based on sparse decomposition and l1-norm optimization algorithm of the received signal over an over-complete matrix composed of both sine and cosine waveforms and time-shifted impulse waveforms. By proper construction of the over-complete matrix, the impulse removal and symbol decoding have been performed simultaneously. Thus, it can reduce the computational complexity. Our method does not require any assumption about the location and magnitude of the impulse and does not demand pilot symbols or null subcarriers unlike other existing methods. Thus, the proposed method is blind in nature. The method is evaluated using different levels of impulse noise and signal-to-noise ratios varying from 0 to 20 dB. Preliminary evaluation results demonstrate the effectiveness of the sparse representation with the proposed dictionaries in effectively removing the impulse noise and improving the bit error rate under different noise levels. © 2017, Springer Science+Business Media New York.

Circuits, Systems, and Signal Processing

Blind Impulse Estimation and Removal Using Sparse Signal Decomposition Framework for OFDM Systems

In this paper, the authors present an automated method for quality assessment of electrocardiogram (ECG) signal. Our proposed method not only detects and classifies the ECG noises but also localizes the ECG noises which can play a crucial role in extracting reliable clinical features for ECG analysis systems. The proposed method is based on three stages: Wavelet decomposition of ECG signal into sub-bands; simultaneous ECG signal and noise reconstruction; extraction of temporal features such as maximum absolute amplitude, zerocrossings, kurtosis and autocorrelation function for detection, localization and classification of ECG noises including flat line (FL), time-varying noise or pause (TVN), baseline wander (BW), abrupt change (AB), power line interference (PLI), muscle artifacts (MA) and additive white Gaussian noise (AWGN). The proposed method is tested and validated against manually annotated ECG signals corrupted with aforementioned noises taken from MIT-BIH arrhythmia database, Physionet challenge database, and real-time recorded ECG signals. Comparative detection and classification results depict the superior performance of the proposed method over state of art methods. Detection results show that our method can achieve an average sensitivity (Se), average specificity (Sp) and accuracy (A) of 99.61%, 98.51%, 99.49% respectively. Also, the method achieves a Se of 98.18%, and Sp of 94.97% for real-time recorded ECG signals. The method has an average timing error of 0.14 s in localizing the noise segments. Further, classification results demonstrate that the proposed method achieves an average sensitivity (Se), average positive predictivity (PP) and classification accuracy (Ac) of 98.53%, 98.89%, 97.50% respectively. © 2017 Nalecz Institute of Biocybernetics and Biomedical Engineering of the Polish Academy of Sciences

Biocybernetics and Biomedical Engineering

An automated ECG signal quality assessment method for unsupervised diagnostic systems

This paper presents a method of detecting voltage sag, swell and interruption events based on a signal processing tool viz. variational mode decomposition (VMD). The proposed method is able to keep track of variations in amplitude, phase, frequency and undelivered energy due to such events. Voltage signal is half-wave rectified and then decomposed by VMD to get DC part representing instantaneous amplitude envelope, thereby obtaining start/end times and depth of sag/swell. The phase jump and frequency deviations are observed from instantaneous phase, obtained from analytic signal of VMD mode having center frequency nearer to fundamental. Algorithm is tested for various cases of synthetic and simulated signals in MATLAB/Simulink. Comparative performance with recursive discrete Fourier transform and Hilbert transform based method is demonstrated. © 2017 IEEE.