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

This paper proposes a new space vector based pulse width modulation (PWM) technique to operate a five phase induction machine fed by two level inverter in the overmodulation region with significantly low harmonic distortion and switching loss. The proposed technique is simulated in MATLAB - SIMULINK and the results are compared with the existing PWM techniques. A comparative study of the performance of the five phase drive using stator flux ripple concept with the proposed PWM technique is presented in the over-modulation region. The simulation results are experimentally validated using TMS320F28379D micro-controller platform with a custom made five phase drive system. It is found that in the over-modulation region, the proposed PWM technique results in considerably low RMS current ripple and switching power loss as compared to those corresponding to the conventional PWM techniques. © 2020 IEEE.

World University root node

9th IEEE International Conference on Power Electronics, Drives and Energy Systems, PEDES 2020

Space vector modulation technique with improved harmonic performance for a five phase induction motor drive in the over-modulation region

The design of apodization and windowing functions forms the predominant part of the beamforming process in ultrasound imaging. However, the detailed analysis of apodization in the case of beamforming for flow imaging is very limited in the literature. This paper introduces the concept of dual apodization technique in vector triangulation for ultrasound-based vector flow imaging. The approach utilizes the idea of multiple apodization to induce a steering effect at receive along with sidelobe suppression for the delay compensated radio-frequency (RF) signals. The method is investigated using extensive simulations for transverse flows with different flow profiles at different velocities, which shows an improvement in resolution and better clutter suppression. The proposed approach is further analyzed using various conventional and data adaptive apodization techniques for a gradient flow profile. The error variance in velocity magnitude estimate is as low as 5.0251\times 10^{-4}\ [m/s]^{2} and the mean angle error is +0.7358° using Hanning-Gaussian apodization for a transverse gradient flow with a peak velocity of 0.25 m/s. © 2020 IEEE.

Proceedings - International Symposium on Biomedical Imaging

Directional Beam Focusing Based Dual Apodization Approach for Improved Vector Flow Imaging

Ultrasound (US) imaging systems typically employ a single beamforming scheme which is the delay and sum (DAS) beamforming due to its reduced complexity. However, DAS results in images with limited resolution and contrast. The limitations of DAS have been overcome by, delay multiply and sum (DMAS) beamforming, making it especially preferable in cases where finer image details are required in larger depth of scans for an accurate diagnosis. But, DMAS is confined to transducer frequencies where the generated harmonics also fall in the processable frequency range of the US system. However, if US systems could provide the flexibility to reconfigure beamforming considering the restrictions of each beamforming scheme, it is possible to select the best beamforming according to the clinical requirement and system constraints. This work is a fundamental step towards enabling reconfigurable beamforming for on-the-fly selection among the DAS and DMAS beamforming schemes, with low reconfiguration overhead, specifically for each imaging scenario to aid better diagnosis. Two novel architectures are proposed, that reconfigures between DAS and DMAS beamforming as a function of transducer's center frequency with minimum additional computational overhead. The implementation results of the proposed architectures on xc7z010clg400-1 FPGA are reported. The possibilities of pixel-level beamforming reconfigurability, where the different tissue regions are beamformed with either DAS or DMAS are also shown through simulations. © 2007-2012 IEEE.

IEEE Transactions on Biomedical Circuits and Systems

Towards A Pixel-Level Reconfigurable Digital Beamforming Core for Ultrasound Imaging

This letter examines a state estimation with event-based transmissions for a linear discrete-time system when multiplicative noise affects the measurements while the additive noises of process and measurements of the sensor are correlated with each other. A general event-based technique is applied to produce the measurements at event-triggering instants and the sum of Gaussians approach is used at remote estimator to address the computation of state estimate when measurements are unavailable. The two-step predicted probability density function with Gaussian assumption is used to derive the recursive equations for the state estimate and its covariance matrix when the correlation between additive noises is at the same epoch. The results proposed are validated by a numerical example. © 2017 IEEE.

IEEE Control Systems Letters

Event-based state estimation with multiplicative measurement noise and correlated additive noises

Functional splitting and packetized fronthaul (FH) are two approaches to realize cloud radio access networks in a cost-effective manner. In the former, some baseband functionalities are offloaded to remote radio units (RRUs) instead of centralizing all of them at a baseband unit pool. This reduces the capacity and latency requirements on FH when massive multiple-input-massive-output RRUs are used. The latter approach aims to use the ubiquitous Ethernet networks for FH. However, this leads to random packet delays due to queuing at switching/aggregating gateways. In this letter, we present a novel analytical framework to characterize the distribution of queuing delays at an aggregation gateway in the uplink. This framework incorporates random user activity, the uplink spectral efficiencies of users, the slotted nature of uplink transmissions, and FH capacity. We study the impact of packet arrival rates, average packet sizes, and FH capacity on queue length and queuing delay distributions. We show that significant statistical multiplexing gains are possible by aggregating traffic from multiple RRUs. © 1997-2012 IEEE.

IEEE Communications Letters

Uplink Latency in Massive MIMO-Based C-RAN with Intra-PHY Functional Split

The cascaded H-bridge (CHB) multilevel converter has been used in various applications, such as the STATCOMs and solid-state transformers. Due to its modular structure, fault tolerance can be incorporated in the CHB multilevel converter. In this article, a model predictive control (MPC)-based fault detection and localization (FDL) scheme is proposed for the CHB multilevel converter that utilizes the already-installed ac current measurement and does not require additional sensors. The proposed FDL scheme can detect single or multiple open-circuit switch faults in the CHB multilevel converter by comparing the predicted states of the MPC controller with the actual measured states. The detected fault(s) is(are) further localized through a fault localization matrix which narrows down the faulty switch using historical fault data. The proposed scheme is shown to complete the FDL process for both single or multiple open-switch faults within a fundamental cycle period, even during low-load conditions. It has also been shown that the proposed scheme is immune to system dynamics such as load and voltage variations, and has been validated experimentally for various open-circuit fault scenarios. © 1986-2012 IEEE.

IEEE Transactions on Power Electronics

Fault Detection and Localization for Cascaded H-Bridge Multilevel Converter with Model Predictive Control

Commercial buildings consume significant portion of electricity in developed countries and air conditioning systems account for bulk demand within the buildings. These air conditioning systems handle large volumes of air and can be utilized effectively as thermal energy storage. This work is focussed on providing Demand Response (DR) ancillary service by adjusting electricity demand from air conditioning system according to grid requirements, considering occupant preferences for additional revenue. First, detailed component-wise mathematical model is developed for the air conditioning system. Subsequently, a transactive market based control algorithm including agent bidding strategies, and market clearing approach is proposed. The proposed control is designed considering the general requirements of the Energy Market Authority (EMA) Singapore's DR programme. Simulation studies are carried out and results show that proposed transactive control is effective in normal operating conditions as well as providing DR services according to market price signals. © 2020 IEEE.

IEEE PES Innovative Smart Grid Technologies Conference Europe

Transactive control of air-conditioning systems in buildings for demand response

Though the merits of matrix-based dual-active-bridge (MB-DAB) as a grid-connected Solid-State-Transformer (SST) submodule have been presented in literature lately, its operation and control in the cascaded configuration have not been explored. The objective of this paper is to present the operation and control challenges of the cascaded matrix-based dual-active-bridge (CMB-DAB) in detail, from the perspective of the Medium-Voltage-AC (MVAC) to Low-Voltage-DC (LVDC) conversion stage of a grid-connected SST. Subsequently, the control strategy required to eliminate the unavoidable power imbalance issue is explained comprehensively. The simulation results are presented for a 7-level 52.65 kVA CMB-DAB converter to demonstrate the inevitable power imbalance issue and the proposed control strategy as a mitigation technique. The proposed power balance controller (PBC) is observed to perform smoothly in adjunction with the LVDC bus control and remediate power imbalances during steady-state as well as transient-states by adding suitable phase-shift correction terms. © 2020 IEEE.

Power balance control of cascaded matrix-based dual-active-bridge converter

In this paper, a three-phase matrix-based AC to DC power converter is presented considering all the practical implementation aspects for battery charging applications. Unlike some of the matrix-based proposal in the literature, the proposed converter uses only six gate drivers for converting three-phase AC to medium-frequency AC, which is then stepped down and rectified to an appropriate voltage for battery interface. Managing energy stored in transformer's leakage inductor is often a problem while utilizing single driver per matrix switch. An additional short-circuit leg is proposed to circulate the stored energy during zero vector periods of the proposed converter, thereby ensuring continuous path for the leakage energy. The analysis and design of the proposed converter is validated on a 2 kW experimental prototype and test results are presented for validation. © 2020 IEEE.

Analysis and implementation of a three-phase matrix-based isolated AC-DC converter with transformer leakage energy management

Cascaded H-bridge (CHB) multilevel converter is widely used for medium voltage motor drives, Static Synchronous Compensator (STATCOMs) and solid-state transformers because of its advantages such as modular design, low harmonic distortion of input current and lower grid-side filter requirements compared to two-level converters. Among the failures in active devices, detection and localization of open-circuit (OC) faults either due to bond-wire lift off (device-side failures) or malfunction of gate driver (drive-side failures) are extensively studied. In this paper, fault detection and localization methods proposed in literature for CHB multilevel converters are analyzed and compared with respect to the time taken for fault localization and additional sensor requirements. For ease of understanding, the methods are classified as model-based, feature-based and hardware-based, and suitability of each classification is recommended for different applications. © 2020 IEEE.