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

mmWave radars play a vital role in autonomous systems, such as unmanned aerial vehicles (UAVs), unmanned surface vehicles (USVs), ground station control and monitoring systems. The challenging task when using mmWave radars is to estimate the accurate angle of arrival (AoA) of the targets, due to the limited number of receivers. In this paper, we present a novel AoA estimation technique, using mmWave FMCW radars operating in the frequency range 77–81 GHz by utilizing the mechanical rotation. Rotating the radar also increases the field of view in both azimuth and elevation. The proposed method estimates the AoA of the targets, using only a single transmitter and receiver. The measurements are carried out in a variety of practical scenarios including pedestrians, a car, and an UAV, also known as a drone. With measured data, range-angle maps are created, and morphological operators are used to estimate the AoA of the targets. We also process radar range-angle images for improved visual representation. The proposed method will be extremely beneficial for practical ground stations, traffic control and monitoring frameworks for both on-ground and airborne vehicles. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

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Electronics (Switzerland)

Localization of multi-class on-road and aerial targets using mmwave FMCW radar

The optical pickup unit (OPU) is an optical assembly, which is used for reading and writing digital optical disks. It consists of a laser diode, quadrant photodetector, and other optical components to maintain focus. This arrangement of the laser and photodetector is very similar to those in expensive equipment, such as atomic force microscopes, used for nanoscale metrology. Many researchers have hence investigated the use of an OPU to design low-cost alternatives. However, these nonstandard uses of an OPU are challenging since the OPU has originally been optimized to sense reflections from the highly reflecting surface of an optical disk. In this work, we present a new synchronous detection-based method that improves the performance of the OPU in measuring the reflection from poorly reflecting substrates. This method utilizes the high bandwidth of both the laser and photodetector of the OPU. We excite the laser with a pulsed input and look for a signal at the pulsing frequency in the output from the OPU. This signal is further processed through a phase-sensitive detector. We show that this method reduces the offsets in the measurement and allows us to make effective use of a higher gain to measure the reflection from substrates with poor reflectivity. © 1963-2012 IEEE.

IEEE Transactions on Instrumentation and Measurement

Synchronous Detection to Reduce Offsets in Focus Error of an Optical Pickup Unit

arXiv preprint arXiv:2110.

Event-triggered Control for Nonlinear Systems with Center Manifolds

Localized plasmon resonance in metallic nanoparticles can enable polarization-dependent electric field enhancement. Semiconducting monolayers are used in conjunction with polarization-sensitive plasmonic structures, to maximize the field overlap and promote polarization-sensitive photon detection. © 2021 OSA.

2021 Conference on Lasers and Electro-Optics, CLEO 2021 - Proceedings

Polarization Sensitive Photodetection using Semiconducting Monolayers

The design of a wideband reflecting type linear-circular and linear-linear polarization converter in the THz frequency regime is described in depth in this work. The reflective polarizer unitcell seen here is made of a simple circular ring with two orthogonal cuts printed on top of a $\text{Si} 0_{2}$ substrate which is terminated with the ground. Post simulation results show a linearly polarized $((x/y)$ incident wave converted to its cross $(y/x)$ component in two frequency bands (7.19-11.12 THz and 15.28-15.78 THz) after reflection. The reflected wave would also be circularly polarized in the frequency bands (5.77-6.38 THz and 12.40-14.01 THz). The proposed structure has a unitcell periodicity of 0.1846 $\lambda_{\mathrm{L}}$ and an effective thickness of 0.0685 $\lambda_{\mathrm{L}}$, where $\lambda_{\mathrm{L}}$ is the lowest broadband frequency. For linear to cross conversion, the proposed design has a stable reaction up to 45°, and for linear to circular conversion, it has a stable response up to 30°. Authors are convinced that the proposed geometry has several advantages like simple, compact, and angular stable. It is used in real-time applications like polarization beam-splitters and time-domain spectroscopy, where these conversions are the primary concern. © 2021 IEEE.

Proceedings of the 4th International Conference on Microelectronics, Signals and Systems, ICMSS 2021

A Simple Wideband Dual-Slotted Circular Ring Based Linear-Circular and Linear-Cross Reflective Type Polarizer for THz Regime

To utilize the solar photovoltaic (PV) energy efficiently, dc-dc converters are widely used in both grid-connected and stand-alone systems. Among the various topologies, interleaved dc-dc boost converter offers the benefit of modularity, high power density, and high efficiency along with reduced input current ripple to the PV panel, thereby improving its power extraction efficiency. Open-circuit faults in any of the semiconductor switches of interleaved boost converter could lead to unequal loading on the healthy phases and increase in ripple current that reduces the extraction efficiency of the PV system. To address this issue, a new fault detection and localization scheme is proposed in this article. The proposed scheme utilizes the switching-frequency-based harmonic component for fault detection and localization. Once the fault is localized, a postfault restoration and control strategy is also proposed to ensure equal current sharing among the remaining healthy modules within their maximum current rating and minimize the input current ripple in the PV panel. Detailed simulations are carried out to show the effectiveness of the proposed approach. A laboratory prototype of the interleaved converter is built to validate the proposed approach and experimental test results are provided. © 1986-2012 IEEE.

IEEE Transactions on Power Electronics

A Fault Diagnosis and Postfault Reconfiguration Scheme for Interleaved Boost Converter in PV-Based System

In this paper, the effect of min-max zero-sequence voltage (ZSV) injection on the maximum average neutral-point (NP) current control limits of a neutral-point-clamped (NPC) converter is analyzed. These current limits determine the stable operating range of the NPC converter in applications that impose a nonzero average NP current, like-NPC converters feeding multiterminal dc loads, back-to-back-connected NPC converter-based wind and high voltage dc transmission systems, etc. Previously, a dual-mode modulation technique was implemented in the literature which provided the maximum average NP current limits without considering the ZSV effect. As the ZSV injection affects the NP duty cycles, and in turn the NP current, it is necessary to analyze and quantify its effect. In this paper, the effect of ZSV on the current limits is analytically calculated. Simulation results are obtained in MATLAB/Simulink environment to validate the derived analytical equations. © 2021 IEEE.

IECON Proceedings (Industrial Electronics Conference)

Effect of Zero-Sequence Voltage on the Maximum Average Neutral-Point Current Limit of Neutral-Point-Clamped Converters

A three-stage solid-state transformer (SST) is a preferred replacement for line frequency transformer as it provides ancillary services in addition to stepping-up/down of grid voltages. Each active switch in SST is a potential source of failure, and a quick fault detection and isolation help in reducing the downtime. In this article, a novel fault detection and localization algorithm is proposed to localize the open-circuit (OC) faults (be it a single switch fault or multiple switch faults in multiple modules) in the cascaded H-bridge (CHB) stage of the SST. The proposed method is designed such that only one voltage sensor is needed to measure the grid-side voltage of the CHB for fault detection and localization. By comparing the estimated grid-side voltage of the CHB with the measured values, OC fault is detected. Once the fault is detected, the modulation scheme is switched from phase-shifted unipolar sinusoidal pulsewidth modulation (SPWM) to phase-shifted bipolar SPWM to localize the faults. The difference in the measured grid-side voltage of the CHB before and after each module's state change is calculated and faults are localized. The presented algorithm is substantiated using experimental results from a 1-kVA SST prototype. The main advantage of the proposed algorithm is that it requires only 2n comparisons to localize the faulty modules in a CHB with n H-bridges, which takes less than a line cycle to complete. © 1986-2012 IEEE.

A Novel Open-Circuit Fault Detection and Localization Scheme for Cascaded H-Bridge Stage of a Three-Stage Solid-State Transformer

Transformerless inverters are being used for integrating photovoltaic (PV) sources into the grid. Highly efficient and reliable inverter concept (HERIC) inverter is one such topology, which is derived from an H-bridge by adding a bypass leg on the ac side using two back-to-back insulated gate bipolar transistors (IGBTs). Open-circuit fault in the bypass leg would result in conduction of current through antiparallel diodes of the main switches of the inverter, effectively making the inverter operate in bipolar mode. As a result of the fault, there would not be an issue of leakage current, and the operation would continue at the expense of increased conduction losses and dc-offset in the grid current. This article proposes an online noninvasive model-based technique to detect switch faults in the bypass leg of the HERIC inverter. The grid current at the peak of the carrier signal is predicted based on the measured grid current at the start of the zero states. By comparing the estimated and measured grid currents at the peak of the carrier signal, the faulty switch in the bypass leg is localized. Once the fault is localized, the inverter's modulation scheme is changed to conventional bipolar mode to improve the performance of the converter during the post-fault stage. A detailed simulation study is carried out to verify the effectiveness of the proposed approach. Experimental tests on the prototype converter show that the proposed algorithm can reliably detect the open-circuit fault in switches of the bypass leg, and once a fault is detected, the algorithm would change the modulation scheme to bipolar mode to minimize the inverter loss and dc-offset in the grid current. © 2013 IEEE.

IEEE Journal of Emerging and Selected Topics in Power Electronics

Noninvasive Model-Based Open-Circuit Switch Fault Detection of AC-Bypass Leg Switches in Transformerless PV Inverter

Battery energy storage systems (BESSs) are often integrated into stand-alone dc microgrids (dcMGs) with photovoltaic (PV) system to enhance the microgrid reliability and prevent the dc bus voltage instability arising from PV power generation intermittency and load demand transients. The battery degradation rate is critically influenced by its utilization manner. The contribution of this paper is to compare various standalone dcMG coordinated control strategies for the PV and BESSs, and analyze their efficacy and impact on the battery lifetime. The battery lifetime investigation is carried out via simulation case studies with yearly irradiance and load profiles. © 2021 IEEE.