Faculty Publications
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Publications by NITK Faculty
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Item Pyrene-Oxadiazoles for Organic Light-Emitting Diodes: Triplet to Singlet Energy Transfer and Role of Hole-Injection/Hole-Blocking Materials(American Chemical Society service@acs.org, 2016) Chidirala, S.; Ulla, H.; Valaboju, A.; Raveendra Kiran, M.R.; Mohanty, M.E.; Satyanarayan, M.N.; Umesh, G.; Bhanuprakash, K.; Rao, V.J.Three pyrene-oxadiazole derivatives were synthesized and characterized by optical, electrochemical, thermal, and theoretical investigations to obtain efficient multifunctional organic light emitting diode (OLED) materials. Synthesized molecules were used as emitters and electron transporters in three different device configurations, involving hole-injection/hole-blocking materials that showed good current and power efficiencies. To understand the underlying mechanisms involved in the application of these molecules as emitters and transporters, a detailed photophysical characterization of molecules 4-6 was carried out. The absorption, steady-state fluorescence, phosphorescence, fluorescence lifetime, and phosphorescence lifetime measurements were carried out. The high quantum yield and efficient reverse intersystem crossing leading to delayed fluorescence emission makes the molecule a good emitter, and the charge delocalization properties leading to excimer formation make them efficient electron transporters. Isoenergetic singlet and triplet states of the molecules make the reverse intersystem crossing feasible at room temperature even in the absence of thermal activation. © 2015 American Chemical Society.Item Fuzzy PI controller for bidirectional power flow applications with harmonic current mitigation under unbalanced scenario(AIMS Press, 2018) Nagaraj, C.; Manjunatha Sharma, K.The depletion of fossil fuels and environmental concern forces the extraction of power from low carbon fuels causes generation problem due to intermittent solar-wind renewable energy sources and power electronic applications. Furthermore, the significant amount of non-linear loads in the system causes power quality problems. Nowadays, the more and more DC loads like LED lights to save energy consumption are connected to the AC distribution system. These DC loads are connected at DC grid side in order to avoid the extra AC/DC power conversion loss. In this paper, the proposed d-q reference current method applied for shunt active power filter based 3-phase 4-leg bidirectional interfacing converter with fuzzy PI controller to achieve the real power transfer between DC grid side and AC grid side with current harmonics compensation at common connecting point simultaneously under balanced and unbalanced distorted grid and non-linear load conditions. The hysteresis current control comparator without PLL is used to compare actual grid current with reference filter current and generate the switching pulses for driving the bidirectional interfacing converter. The DC grid shunt connected intermittent hybrid solar-wind energy sources are integrating with AC grid utility through bidirectional interfacing converter has been into consideration for simulation studies. The MATLAB/SIMULINK tool is used to yield the improved grid current THD with fuzzy logic controller over PI controller. © 2018 the Author(s), licensee AIMS Press.Item Enhancement in fluorescence quantum yield of MEH-PPV:BT blends for polymer light emitting diode applications(Elsevier B.V., 2018) K M, K.M.; Satyanarayan, M.N.; Umesh, G.We have investigated the effect of blending electron deficient heterocycle Benzothiadiazole (BT) on the photo-physical properties of conjugated polymer Poly [2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV). Quantum yield (QY) value has been found to increase from 37% for pure MEH-PPV to 45% for an optimum MEH-PPV:BT blend ratio of 1:3. This can be attributed to the efficient energy transfer from the wide bandgap BT (host) to the small bandgap MEH-PPV (guest). The FTIR spectrum of MEH-PPV:BT blended thin film indicates suppression of aromatic C-H out-of-plane and in-plane bending, suggesting planarization of the conjugated polymer chains and, hence, leading to increase in the conjugation length. The increase in conjugation length is also evident from the red-shifted PL spectra of MEH-PPV:BT blended films. Single layer MEH-PPV:BT device shows lower turn-on voltage than single layer MEH-PPV alone device. Further, the effect of electrical conductivity of PEDOT:PSS on the current-voltage characteristics is investigated in the PLED devices with MEH-PPV:BT blend as the active layer. PEDOT:PSS with higher conductivity as HIL reduces the turn on voltage from 4.5 V to 3.9 V and enhances the current density and optical output in the device. © 2018 Elsevier B.V.Item Magnetic Coupling Characteristics and Efficiency Analysis of Spiral Magnetic Power Pads for Inductive WPT System(River Publishers, 2022) Kishan, D.The inductive wireless power transfer system (IWPT) for electric vehicle battery charging works based on the principle of mutual induction (MI). The amount of power transfer from source to vehicle battery be contingent on the mutual inductance (MI) within the inductively coupled pads. This mutual inductance depends on the type of the inductive power pads, the distance among them, their positioning etc. This paper develops and study the inductive coupling characteristics of identical spiral circular and square inductive power pads. The coupling characteristics at various misalignments with different vertical distance between the coils is presented. In this work, the inductive power pads without using ferrite bars, and with ferrite bars are considered. The coupling characteristics of the spiral circular and square are computed using FEM simulations and validated with experimental results. This paper also investigated the power loss and efficiency analysis of the spiral inductive pads of the resonant IWPT system. © 2022 River Publishers.Item Dielectric Metasurface Inspired Directional Multi-Port Luneburg Lens as a Medium for 5G Wireless Power Transfer - A Design Methodology(Institute of Electrical and Electronics Engineers Inc., 2022) Majumder, B.; Vinnakota, S.S.; Upadhyay, S.; Kandasamy, K.In this paper, a novel dielectric metasurface-inspired multi-beam directional Luneburg lens is proposed as a wireless power transfer medium at 5G mm-wave band. The lens is constructed using dielectric-based unit cells made up of a glide symmetric approach. It is connected with a set of microwave detector integrated multi-port tapered rectangular feeds to convert the received RF energy from different directions to DC power across a combined load. The proposed structure can be a potential candidate to harvest ambient energy from a wide coverage range of around 160° and produce a power conversion efficiency of about 76% for an input power of 14.9 dBm at 24 GHz. © 2009-2012 IEEE.Item An integrated PMU architecture for power system applications(De Gruyter Open Ltd, 2022) Aalam, M.K.; Shubhanga, K.N.Time synchronized phasors obtained using Phasor Measurement Units (PMU) spread across wide areas have revolutionized power system monitoring and control. These synchronized measurements must be accurate and fast in order to comply with the latest IEEE standards for synchrophasor measurements. The speed at which a PMU provides an output depends on the group delay associated with that PMU and the permissible group delay in-turn decides the utility of a PMU for either control or measurement application. Based on the group delay compensation techniques, in the literature, two individual types of PMUs, such as causal and non-causal PMUs have been introduced. This paper presents an approach where both causal and non-causal PMUs are combined in an integrated PMU architecture. This method not only illustrates the group delay performance of two PMUs in a single module, but also can be used for multiple functions. In this environment several PMU algorithms have been compared with respect to their group delays and their effect on the response time. Application of the integrated PMU architecture to a four-machine 10-bus power system has been demonstrated using a six-input PMU with three-phase voltage and current signals as inputs. Different causal compensation schemes are introduced due to the availability of voltage and current-based frequency and ROCOF signals. Impact of these compensation schemes on PMU accuracy is evaluated through the Total Vector Error (TVE) index. The influence of these compensation schemes on measurements like power and impedance is also investigated. Finally, outputs from the integrated PMU architecture are fed into a Power System Stabilizer (PSS) to control the small-signal stability performance of a power system during dynamic conditions. © 2021 Walter de Gruyter GmbH, Berlin/Boston.Item A chemically robust amine-grafted Zn(ii)-based smart supramolecular gel as a regenerative platform for trace discrimination of nitro-antibiotics and assorted environmental toxins(Royal Society of Chemistry, 2023) Saha, E.; Chhetri, A.; Venugopal, P.P.; Chakraborty, D.; Mitra, J.Smart supramolecular metallogels are fascinating reusable materials with the potential for a wide range of sustainable applications including the detection of multiple lethal pollutants. We have assembled a chemically robust triazole-containing Zn(ii)-supramolecular gel (ZnGel), where the channels and surface of the gel are strategically decorated with triazole N and appended -NH2 units that are pivotal to ZnGel's efficacy as a multi-sensory probe. ZnGel shows selective fluorescence quenching in the presence of traces of nitro-antibiotics (LOD of nitrofurantoin: 4.62 ppm) and electron-deficient nitrophenols (LOD of 4-nitrophenol: 4.18 ppm), without any prior activation. Density functional theory calculations delineate the importance of the triazole gelator in the turn-off fluorescence response of ZnGel to divergent organo-toxins and substantiate the supramolecular interactions between the ZnGel and the analytes. Significant fluorescence quenching of ZnGel ensued in the presence of a trace amount of Fe3+ (LOD: 6.13 ppm) over other competing metal ions, in addition to visible colorimetric changes in the ZnGel upon metal encapsulation. The quenching ability of ZnGel remains unaltered for multiple cycles toward these environmental pollutants. The noteworthy quenching efficiency is attributed to a combination of static and dynamic fluorescence quenching and resonance energy transfer, which are in harmony with the DFT predictions. Thus, ZnGel provides a platform for the development of gel-based probes for diverse applications in the future. © 2023 The Royal Society of Chemistry.Item Three-Leg DC-DC Converter for Efficient Inductive Power Transfer of Electric Vehicles for Wide-Range Battery Applications(Institute of Electrical and Electronics Engineers Inc., 2023) Vinod, M.; Kishan, D.; Dastagiri Reddy, B.D.The design of an inductive power transfer system for different electric vehicle (EV) models with widely varied battery pack voltages has been a challenging task. The majority of modern EV models are equipped with 400 or 800 V battery packs. To charge both batteries efficiently, an additional dc-dc converter on the receiver side is employed, which reduces the overall system efficiency and also increases the cost. This letter proposes a reduced switch count novel converter to charge distinct EV models without degrading the efficiency of the system. The proposed converter has two operating modes, a voltage doubler mode to charge an 800 V battery and a current doubler mode to charge a 400 V battery at the same power level. MATLAB/Simulink simulations have been carried out to verify the performance of the three-leg converter for both 400 and 800 V batteries at 7.2 kW. Furthermore, a laboratory prototype of the proposed converter for 500 W has been built using the silicon carbide (SiC) devices, and the results obtained are provided. © 1986-2012 IEEE.Item Dual Converters Coupled to Thermal Grid for Simultaneous Control on Regulation and Compensation in a Hybrid AC-DC Network(Taylor and Francis Ltd., 2024) Sowmmiya, U.; Keerthana, M.S.; Karthikeyan, A.; Padmanathan, K.In conventional, radial, AC distribution system, the unbalances in load voltages & source currents at distributor junction (DJ) may affect the quality of power. Mostly, a single converter is employed to address any one unbalance at an instant and the power transfer during critical conditions is not met out effectively. To overcome this, an effective, coordinated operation of dual converters (C1&C2) in a hybrid AC-DC network coupled to thermal grid (Electro-thermal network) for meeting the heating demand of a community, is enunciated in this paper. The DC micro grid (DCM) is energized by renewable for serving the community’s heating and public electrical demands. Irrespective of source voltage & load conditions, the C1&C2 aim at voltage regulation & load compensation at DJ, respectively. Also, the control exhibits around 3% THD which is well within the standard levels. During any source outage/less power production, DCM supplies power to loads through inversion. An uninterrupted, quality power to loads at DJ by the dual converters, irrespective of source voltage & load variations along with a conservative approach through the thermal grid, claims the prime merit of the setup. Various unbalance cases including voltage sag & swell, no source & excess DCM power cases are examined through a supervisory control algorithm for analyzing the effectiveness of the control & system flexibility. The effective performance of the above is verified in real time using Hardware-in-Loop approach through DS1104 (dSPACE Controller) and OP4510 (Opal-Real Time) Controllers. © 2024 Taylor & Francis Group, LLC.Item Finite control set model predictive control of three-port converter for interfacing a PV-battery energy storage system to a three-phase stand-alone AC system(Oxford University Press, 2024) Preeti, G.A.; Karthikeyan, A.This paper proposes a multiport bidirectional non-isolated converter topology that provides advantages in terms of simultaneous multiple operations, single-stage conversion, high power density and reduced power losses due to the lower number of switches. The proposed multiport converter uses a centralized non-linear controller known as a finite control set model predictive controller to manage the flow of power between different ports. It deals with the parallel operation of photovoltaic and battery energy storage systems for stand-alone alternating current (AC) systems. The converter connects the lower voltage battery to the photovoltaic port using a bidirectional buck/boost converter and the photovoltaic port is linked to the stand-alone AC load through a three-phase full-bridge inverter. Each leg of the three-phase converter will act as a bidirectional direct current (DC)/DC converter as well as an inverter simultaneously. Only six switches manage the power transfer between all the connected ports of photovoltaic-battery energy storage system linked to the stand-alone AC load. The proposed multiport converter is mathematically modelled and controlled by a finite control set model predictive controller. The system is validated in simulation (1-kW rating) and experimental environment (200-W rating). The hardware prototype is developed in the laboratory and the controller is implemented on the field-programmable gate array board. Two independent case studies are carried out to validate the efficacy of the system. The first scenario is for a change in solar irradiance, while the second scenario is for a change in the output load. © The Author(s) 2024. Published by Oxford University Press on behalf of National Institute of Clean-and-Low-Carbon Energy.