Electrical Engineering

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This study presents a novel approach to estimate the maximum power point (MPP) of a photovoltaic (PV) array on an hourly basis using meteorological data. The estimation of MPP of a PV array based on its characteristic equation is done by using Levenberg-Marquardt (LM) method. The monthly averaged daily and hourly global solar irradiation during sunshine hours of Guwahati city is estimated by taking relative humidity and ambient temperature data using empirical relations. The actual and estimated maximum powers of a PV array of monthly averaged daily and hourly basis is calculated using MATLAB. It is demonstrated that each of the estimated maximum power of a PV array on an hourly basis is nearly equal to each of the actual maximum power. The MPP of a PV module estimated by the LM method is validated with the actual and experimental results. A comparative study of MPP of a PV module estimated from the proposed method with perturb-and-observe based on proportional-integral, genetic algorithm and Gauss-Seidel is performed. The performance of the proposed algorithm for estimation of MPP of a PV array ensures the accuracy and faster convergence. © The Institution of Engineering and Technology 2016.

(SoE) School of Engineering

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IET Generation, Transmission and Distribution

Numerical approach to estimate the maximum power point of a photovoltaic array

Photoconductive Antenna(PCA) is considered to be very simple and compact Terahertz (THz) generation source based on opto-electrical conversion method. In recent years, several experimental and simulation studies have been performed to analyze a PCA behavior. However, an accurate equivalent electrical circuit model is needed for theoretical analysis of a PCA. As the electrode gap region of PCA can be modeled as a charged capacitor, this work deals with the calculation of time dependent capacitance of a pulsed PCA system. The analysis of time dependent capacitance provides a better understanding of carrier dynamics in PCA and also helps in creating an accurate equivalent electrical circuit of PCA. © 2015 IEEE.

2015 IEEE Applied Electromagnetics Conference, AEMC 2015

Time dependent capacitance in Photoconductive Antenna

The Power quality has become one of the most vital issue to both electric utilities and end level users of electric power. Automation has completely changed the load nature due to widespread use of power electronic based drives such as adjustable speed drives, Energy efficient lighting, PC's, office accessories etc. All power electronic based sensitive equipments are the major fatalities of power quality problems such as voltage Sag, Swell, Waveform distortion, Poor power factor etc. In this paper, a three phase three wire Distribution Static Compensator (DSTATCOM) which is fed by Photovoltaic (PV) array is proposed for power quality improvement. The DSTATCOM is a three leg voltage source Inverter (VSI) with a DC link capacitor. Photovoltaic module is used to keep regulate the desired voltage at DC link. The Power quality improvement is achieved in terms of reactive power compensation, Power factor correction, Harmonic reduction, DC voltage control. In this paper, the performance of DSTATCOM is shown for Power factor correction(PFC) and Zero voltage regulation (ZVR) modes using d-q and p-q theories of control. The effectiveness of the PV based DSTATCOM is verified with simulation results. The simulation is carried out on MATLAB software using Simulink and PSB toolboxes. © 2015 IEEE.

Proceedings on 2015 1st International Conference on Next Generation Computing Technologies, NGCT 2015

Performance analysis of photovoltaic based DSTATCOM using SRF and IRP control theory1

The p-type semiconducting properties of a triphenylene-fused triindole mesogen, have been studied by applying two complementary methods which have different alignment requirements. The attachment of only three flexible alkyl chains to the nitrogen atoms of this π-extended core is sufficient to induce columnar mesomorphism. High hole mobility values (0.65 cm2 V-1 s-1) have been estimated by space-charge limited current (SCLC) measurements in a diode-like structure which are easily prepared from the melt, rendering this material a good candidate for OPVs and OLEDs devices. The mobility predicted theoretically via a hole-hopping mechanism is in very good agreement with the experimental values determined at the SCLC regime. On the other hand the hole mobility determined on solution processed thin film transistors (OFETs) is significantly lower, which can be rationalized by the high tendency of these large molecules to align on surfaces with their extended π-conjugated core parallel to the substrate as demonstrated by SERS. Despite the differences obtained with the two methods, the acceptable performance found on OFETs fabricated by simple drop-casting processing of such an enlarged aromatic core is remarkable and suggests facile hopping between neighboring molecular columns owing to the large conducting/isolating ratio found in this discotic compound. © 2016 American Chemical Society.

ACS Applied Materials and Interfaces

Mobility versus Alignment of a Semiconducting π-Extended Discotic Liquid-Crystalline Triindole

Two regioisomeric triads D-A1-D and D-A2-D composed of benzodithiophene donors and BODIPY acceptors were synthesized and exhibited spectral coverage up to 700 nm due to efficient intramolecular charge transfer. Structural differences and planarity of these triads lead to distinct photoinduced electron transfer characteristics and charge carrier mobilities of up to ∼10-4 cm2 V-1 s-1. © 2016 The Royal Society of Chemistry.

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RSC Advances

Regioisomeric donor-acceptor-donor triads based on benzodithiophene and BODIPY with distinct optical properties and mobilities

Degradation of organic light emitting diodes (OLEDs) is the most serious obstacle towards their commercialization. OLED degrades due to various internal and external mechanisms. External degradation is mainly caused due to the instability of low work function cathode, pin-hole formation during fabrication which provides a path for oxygen and moisture infiltration. Operation of OLED also leads to degradation with major causes being morphological instability of organic layers, trap formation, indium or oxygen diffusion from anode, interface deterioration etc. Heat generation in the OLED also acts as a source of degradation. Most of the heat is generated instantaneously upon biasing of OLED due to resistive or Joule heating as a consequence of high resistance of organic layers and non-radiative recombination. Generated heat can be reduced by reducing the effects of the generation sources such as improving conductivity of organic layers by doping, using additional layers to improve charge injection, employing emissive layers with low recombination losses etc. However, these ways can only reduce the heat up to a certain amount. To further improve the lifetime of OLED, the generated heat can be dissipated by employing heat sinks using either thermally conducting substrate or encapsulation etc. We present a review on OLED degradation with a particular focus on heat generation, its consequences and ways of reduction. © 2015 Elsevier B.V. All rights reserved.

Synthetic Metals

Degradation of organic light emitting diode: Heat related issues and solutions

Detection of polarisation of microwave signals using infrared thermography is described in this paper. A metal grating consisting of parallel, equally spaced metallic strips is placed in between a microwave source (antenna) and a microwave absorption screen for permitting the determination of direction of electric field vector (polarisation). Very low frequency modulation of the microwave source is added to permit lock-in thermography which enhances thermal resolution.In case of linear polarisation when the metallic strips of the grating are parallel to the direction of electric field vector, the temperature rise on the screen as observed by an infrared camera, is minimum. On the other hand if the metallic strips are perpendicular to the electric field vector the temperature rise observed on the screen is maximum. The orientation of the grid is changed by rotating the grid about a central axis perpendicular to its plane. With each different orientation of the grid a change in temperature rise is observed on the screen.In case of circular polarisation the temperature rise on the absorption screen is almost independent of the grid orientation i.e. there is negligible change in temperature rise with each different orientation of the grid, as the electric field strength perpendicular to grid strips is almost constant for all grid orientations, corresponding to an axial ratio of unity. While in case of elliptical polarisation the temperature change is appreciable depending on the axial ratio.The proposed method is validated on linearly, circularly and elliptically polarised patch antennas radiating at 8 GHz. Simulation is carried out in CST MICROWAVE STUDIO (CST MWS2013) and a good agreement between simulated and experimental (thermographic) results is observed. © 2016 IETE.

IETE Journal of Research

Determination of Polarisation of Microwave Signals by Lock-in Infrared Thermography

Radio Frequency (RF) Microelectromechanical system (MEMS) switches are becoming more and more popular in the electronics industry. The main concern in using RF MEMS switch is its high actuation voltage. Thus the main focus in this paper is to obtain low actuation voltage. This paper presents the simulation and analysis of RF MEMS cantilever beam and Fixed - Fixed beam switches. RF MEMS switches simulated in this paper use electrostatic actuation method. Simulations were done using finite element modeling. Different designs and parameters such as gap between electrodes, beam thickness, beam length, and relative permittivity values of medium between electrodes were chosen for analyzing the deflection of beams for various actuation voltages. Perforations of different dimensions were made on both type of beams and the resulted deflections were studied. The simulation results show that the Cantilever and Fixed - Fixed beams follow approximately similar deflection pattern with Cantilever beam deflecting more for applied actuation voltage in all the studies. © 2016 IEEE.

Proceedings - 2016 International Conference on Micro-Electronics and Telecommunication Engineering, ICMETE 2016

Simulation and analysis of actuation voltage of electrostatically actuated RF MEMS cantilever and fixed - Fixed switches with variable beam parameters

The tape helix slow wave structures used in travelling wave tube (TWT) amplifiers are exploited for use as radiating devices through the fast wave analysis. The dispersion equation is derived from accurate boundary conditions that neither involve assumptions on the current density distribution, nor considers a defined distribution function for a dielectric loaded tape helix slow wave structure surrounded by a conductor or a conductor placed inside the tape helix. Analytical computation of the dispersion characteristics of both the structures revealed the presence of fast wave modes usable for applications such as antennas. © 2016 IEEE.

Fast wave propagation characteristics of dielectric loaded tape helix structures placed around and within a cylindrical core

The next generation sub1GHz Wireless local area network (WLAN) IEEE802.11ah is being standardized to operate around 1GHz ISM band. It is currently much less congested and enable the WLAN devices to access the network to send burst data. It penetrates easily the obstacles and is less affected by frequency fading and thus offers a long range. It offers simple architecture, high energy efficiency, long life of sensor nodes, improvement in range capability with better data rates in comparison with present IEEE802.15.x WPAN (ZigBee, Bluetooth) which works at 2.4GHz for short ranges and due to high power consumption in Bluetooth sensor nodes life is very short. The ZigBee provides data rates up to 250kbps. The 802.11 ah based on Wi-Fi sensor nodes combines the sensors and communication applications together to obtain high data rates from 100kbps to several Mbps. In Internet of Things (IoT) the smart objects are coverted from physical to virtual world to connect with Internet. The Internet of Things enables smart objects to observe, identify, and understand the world without intervention of human-being. The 802.11 ah has architecture similar to IEEE802.11 WLAN to operate on existing infrastructure, which will commercially empower the future of technology to develop and deploy many applications in IoT era and WSN world. © 2015 IEEE.