Journal Articles
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Item A roadmap to UV-protective natural resources: Classification, characteristics, and applications(Royal Society of Chemistry, 2021) P, P.; Salian, A.; Dutta, S.; Mandal, S.Alongside the innumerable benefits of solar rays, the adverse effects of ultraviolet (UV) radiation must be considered. All organisms are subjected to the deleterious effects of UV radiation, particularly UVA (315-400 nm) and UVB (280-315 nm). Continuous UV exposure leads to skin cancer, erythema, and sunburn mediated by reactive oxygen species (ROS). Photoprotection is hence an indispensable feature in all strata of the ecosystem across the microbial, plant, and animal kingdoms, especially under the present circumstance of increased ozone depletion. Photoprotective compounds, like gadusols, mycosporine-like amino acids (MAAs), scytonemin, phenolic compounds like flavonoids, anthocyanins, lignin, and less-explored compounds like sporopollenin, parietin, and usnic acid have been identified in various organisms. Accumulation of photoprotective pigments is a universal mechanism of passive protection against UV, developed by organisms during the early stages of their evolution. Furthermore, many of these compounds contribute to antioxidant and anti-inflammatory actions, which offer additional protection. In this review, the attributes of naturally available UV-screening compounds are investigated. Their taxonomic diversity, mechanism of UV absorption, extraction, and characterization techniques are discussed. In the wake of recent studies that indicate free radical generation in inorganic sunscreen compounds like TiO2 and ZnO, natural products have become a necessity. Insights into natural compounds for photoprotective functions in commercial applications like cosmetics and textiles are also reviewed. Biocompatibility and minimal side effects of these natural compounds open the gateway into an era of green products in the arena of photoprotection. © the Partner Organisations.Item A 20-Pulse Asymmetric Multiphase Staggering Autoconfigured Transformer for Power Quality Improvement(Institute of Electrical and Electronics Engineers Inc., 2018) P, P.; Kalpana, R.; Singh, B.; Bhuvaneswari, G.This letter presents a 20-pulse multiphase staggering autoconfigured transformer (MSAT) for power quality improvement in medium and high power applications. The proposed autoconfigured transformer is a combination of delta and zig-zag transformers. Contrary to the prior art multipulse autoconnected transformers, magnetic rating of the proposed configuration is only 40% of the load rating in addition to improved power quality indices. Moreover, the creation of a neutral point ascribed to inbuilt zig-zag windings supplements as one of the remarkable advantages of the proposed MSAT. Therefore, with this suggested configuration, the performance of zig-zag transformer is accomplished within the autoconfigured transformer. A detailed comparison of the proposed MSAT configuration with that of other multipulse autoconnected transformers in terms of magnetic rating and power quality indices are presented. Further, the feasibility and operability of the proposed MSAT are verified and validated through experimental tests on the laboratory prototype. The test results so obtained complies with the IEEE-519 and IEC 61000-3-2 standards on power quality requirements. © 2017 IEEE.Item Power Quality Enhancement Using Current Injection Technique in a Zigzag Configured Autotransformer-Based 12-Pulse Rectifier(Institute of Electrical and Electronics Engineers Inc., 2018) Kalpana, R.; Chethana, K.S.; P, P.; Singh, B.This paper proposes a DC-side circuit configuration that improves the harmonic suppression ability of a 12-pulse diode bridge rectifier (DBR) using a zigzag configured autotransformer. The DC-side circuit uses a single-phase DBR along with interphase transformer which generates the required circulating current thereby modifies the DC currents at the DBR output, in turn shapes the input line current near to a sine wave. The proposed single-phase DBR is connected in parallel with the load which enables to reuse the harmonic energy thus improving the energy conversion efficiency. The zigzag configured autotransformer used for 12-pulse DBR possesses the inbuilt ability to hinder the zero-sequence components, which expel the need of zero sequence blocking transformer. The proposed configuration is analyzed, simulated in MATLAB Simulink and the simulation results are presented, which confirm the reduction of total harmonic distortion (THD) in the input line current thereby improving the power quality under large load variations. Furthermore, the viability of the proposed configuration is verified by experimental results, which confirm the suitability of the proposed configuration in industrial applications. © 1972-2012 IEEE.Item Three-phase three-level boost-type front-end PFC rectifier for improving power quality at input AC mains of telecom loads(Korean Institute of Power Electronics editor@kipe.or.kr, 2018) P, P.; Kalpana, R.; Singh, B.A three-phase, three-switch, and three-level boost-type PWM rectifier (Vienna rectifier) is proposed as an active front-end power factor correction (PFC) rectifier for telecom loads. The proposed active front-end PFC rectifier system is modeled by the switching cycle average model. The relation between duty ratios and DC link capacitor voltages is derived in terms of the system input currents. Furthermore, the feasible switching states are identified and applied to the proposed system to reduce the switching stress and DC ripples. A detailed equivalent circuit analysis of the proposed front-end PFC rectifier is conducted, and its performance is verified through simulations in MATLAB. Simulation results are verified using an experimental setup of an active front-end PFC rectifier that was developed in the laboratory. Simulation and experimental results demonstrate the improved power quality parameters that are in accordance with the IEEE and IEC standards. © 2018, Korean Institute of Power Electronics. All rights reserved.Item Application of voltage multiplier in 12-pulse rectifier for sinusoidal input current(Institution of Engineering and Technology journals@theiet.org, 2018) P, P.; Kalpana, R.; Singh, B.; Bhuvaneswari, G.A DC current injection circuit of a trifurcated autotransformer (TAT)-based 12-pulse diode bridge rectifier (DBR) is proposed which can help reduction of harmonics in the AC mains. The circuit at the DC side employs a voltage multiplier (VM) circuits namely voltage doubler, voltage tripler and voltage quadrupler and an interphase transformer which provides the required circulating current. This induced circulating current shapes the input AC line current near to a sine wave. The output of VM circuits is connected across the load and thereby reuses the harmonic energy absorbed by the system. Thus, improves the energy conversion efficiency of the proposed system. The TAT-based 12-pulse DBR has the implicit ability to prevent the zero sequence components thus expels the necessity of zero sequence blocking transformer. The proposed configuration is analysed, simulated in MATLAB Simulink and the simulation results are presented, which confirms the improvement in power quality parameters in the input AC line current. Further, the viability of the proposed configuration is verified by experimental results which confirm the suitability of the proposed configuration in AC-DC applications. © 2018 Springer Verlag. All rights reserved.Item Inclusive Design and Development of Front-End Multiphase Rectifier with Reduced Magnetic Rating and Improved Efficiency(Institute of Electrical and Electronics Engineers Inc., 2020) P, P.; Kalpana, R.; Singh, B.This article proposes a 20-pulse asymmetric multiphase converter (AMPC) suitable for medium-and high-power applications. Unlike the other state-of-the-art 20-pulse delta-connected autotransformers, the proposed delta-connected AMPC has an ability to reduce input harmonics, maintains high efficiency, and requires a magnetic rating of only 30.12% of the nominal load; thereby, a significant reduction in space, weight, and overall cost required is the salient features of the proposed AMPC. A detailed power quality performance analysis and an efficiency calculation are discussed. First, the proposed AMPC configuration is simulated in MATLAB/Simulink environment for evaluating its viability under different loading conditions, and the results are illustrated. A detailed comparison of the proposed AMPC configuration with other multipulse transformers is included, which confirms the merits of the proposed system. Also, a prototype is developed, and the experimental measurements obtained are presented to validate the feasibility and operability of the proposed AMPC. The proposed AMPC offers a total harmonic distortion of 3.7% and can operate at near-unity power factor complying with the IEEE and IEC standards. © 2013 IEEE.Item Study of melt pool geometry and solidification microstructure during laser surface melting of Inconel 625 alloy(Elsevier GmbH, 2021) Chaurasia, J.K.; Jinoop, A.N.; P, P.; Paul, C.P.; Bindra, K.S.; Bontha, S.The present study aims to comprehend thermo-fluid conditions during laser surface melting (LSM) of Inconel 625 (IN625) alloy using experimental and numerical modelling approaches. Nine tracks were melted on an IN625 plate at different laser powers and scan speeds. Melt pool geometry and grain morphology were evaluated using microscopy techniques. A 3-D finite volume model based on heat conduction solidification equation (HCS model) was used to simulate LSM process. Further, HCS model was expanded to include effects of fluid dynamics (HCS-FD model). Both the numerical models were used to predict melt pool geometry, peak temperatures, temperature gradients and cooling rates. The error in predictions of melt pool geometry from the HCS-FD model was lower when compared to the HCS model. The velocity vectors show a strong surface tension driven flow which has resulted in narrow and deeper melt pools in agreement with the cross sectional images of the melted tracks. Further, solidification characteristics were interpreted to obtain inferences about grain size and morphology. © 2021 Elsevier GmbHItem Modified Current Control for Tracking Global Peak Under Fast Changing Partial Shading Conditions(Institute of Electrical and Electronics Engineers Inc., 2022) P, P.; Vignesh Kumar, V.; Balasubramanian, B.; Ramana, V.The power - voltage (P-V) characteristics of photovoltaic (PV) systems exhibit multiple power peaks under partially shaded conditions. Several global maximum power point tracking (GMPPT) algorithms in the literature recognize the irradiance change, only after the convergence of operating point to global peak, or use additional hardware to call GMPPT subroutine at definite time intervals to detect any insolation change, and thus track the global peak. However, during fast changing partial shading conditions, these methods are less effective, as they do not detect any irradiance change during the tracking phase of any shading pattern. This paper proposes a novel modified current control approach that uses current as a parameter to detect the insolation change during the tracking phase and track the global peak under fast changing partial shading conditions without any additional hardware. The proposed technique improves the tracking efficiency by as much as 39%, thus proving to be effective under fast-changing partial shading conditions. The superior tracking performance of the proposed algorithm over the existing techniques in terms of its tracking efficiency, dynamic tracking capability, tracking speed, and convergence to the global peak is demonstrated with extensive simulations using MATLAB/Simulink and experimental results. © 1986-2012 IEEE.Item A Novel Algorithm Based on Voltage and Current Perturbation to Track Global Peak Under Partial Shading Conditions(Institute of Electrical and Electronics Engineers Inc., 2022) P, P.; Vignesh Kumar, V.; Koothu Kesavan, K.K.; Balasubramanian, B.Under partial shading conditions, photovoltaic (PV) systems exhibit multiple peaks in their power-voltage (P-V) characteristics. It is essential to extract maximum energy from the PV system. The global maximum power point tracking (GMPPT) algorithms presented in the literature, track the global peak using different methods. It is imperative to have minimal convergence time for GMPPT process. This paper proposes a novel algorithm to track the global peak using voltage and current perturbation. The new GMPPT algorithm operates in a current perturbation or voltage perturbation mode, based on the value of a control variable. In either mode, the proposed technique generates reference current or reference voltage, for navigating the operating point to GMPP location. The proposed algorithm is compared with two GMPPT algorithms, namely, modified maximum power trapezium (M-MPT) and high-performance GMPPT algorithms. The simulation studies are performed in MATLAB and is validated using a laboratory prototype, with dSPACE 1202 MicroLabBox controller for implementing GMPPT methods. Simulation and experimental results show that the new technique exhibits superior performance in terms of tracking time. Also, the energy efficiency is improved by 40% while using the proposed GMPPT algorithm for the irradiance profiles considered in this paper compared to the other two techniques. © 1986-2012 IEEE.Item A Novel Cubic Boost Converter With Continuous Source Current for PV Applications(Institute of Electrical and Electronics Engineers Inc., 2024) Srinivas, B.; P, P.; Nagendrappa, H.; Balasubramanian, B.A converter with high voltage gain is generally necessary for interfacing the photovoltaic (PV) systems with grid. However, more semiconductor components are needed to obtain a higher voltage gain, which results in increased losses. This brief proposes a novel non-isolated cubic boost (NNICB) DC-DC converter for high-voltage PV applications with a wide voltage gain at a lower duty ratio. Compared to traditional high-gain DC-DC converter, the NNICB converter counters the drawbacks of increased component count and high voltage stress. The NNICB DC-DC converter has a continuous source current for PV applications with low-voltage stress across the diodes and switches. A detailed steady-state analysis of the NNICB topology is carried out for the ideal and non-ideal models, and their corresponding voltage gain equations are computed. Furthermore, the analysis is performed using MATLAB/Simulink and is validated using a 230 W laboratory prototype. The experimental results show that the efficiency of the proposed NNICB topology is 94.42% with a voltage gain of 10.5 at 45% duty ratio. This proves the superior performance of the proposed novel converter in comparison with the existing topologies. © 2004-2012 IEEE.