Dr. Nasrullah Khan - Academia.edu (original) (raw)

Papers by Dr. Nasrullah Khan

Innovative Systems Design and Engineering, 2016

Due to immense increase in needs of human being, the power generation system encounters a deficie... more Due to immense increase in needs of human being, the power generation system encounters a deficiency of key energy sources as a result the demand is increasing day by day without an increase in alternative generation resources and transmission line capability. The constantly increase of electrical power demands and loads, especially non-linear loads making the power system network become more complicate to operate and the system becomes unstable with large power flows without proper control and operation. The advancement in power system with time have brings new challenges and sometimes it is difficult to operate system in stable condition due to complex system network. One of the invention of power electronics is FACTS technology. FACTS (Flexible Alternating Current Transmission Systems) devices are based on power electronics and other dynamic controllers that provide control of one or more AC transmission system parameters to upgrade the controllability and to inc...

Energy Storage, 2020

To meet heating demand without global warming is a huge target for the energy community these day... more To meet heating demand without global warming is a huge target for the energy community these days. To attain this challenge, solar energy harvesting to meet domestic hot water demand is a promising solution. Carbon dioxide (CO2) is becoming ever more significant as heat transporting fluid. Simulation‐based efficiency assessment models are requisite for analogous advances. This research presents a dynamic simulation model of high temperature concentrated solar plant using directly heated molten salt to indirectly power a supercritical CO2 Brayton cycle. Target of the study is to achieve 1 MW generation and simulation work is performed in TRNSYS computer software. The operating conditions for the plant cycle and efficiency for indirectly heated CO2 recompression Brayton cycle are also calculated with the help of engineering equation solver. The system is divided into three major loops: solar thermal heat collection, power generation, and heat recovery. Results have shown overall cycl...

Journal of Magnetics, 2017

This paper presents a 2-D analytical method to calculate the back EMF of the axial flux permanent... more This paper presents a 2-D analytical method to calculate the back EMF of the axial flux permanent magnet synchronous generator (AFPMSG) with coreless stator and dual rotor having magnets mounted on both sides of rotor yoke. Furthermore, in order to reduce the no load voltage total harmonics distortion (VTHD), the initial model of the coreless AFPMSG is optimized by using a developed analytical method. Optimization using the 2-D analytical method reduces the optimization time to less than a minute. The back EMF obtained by using the 2-D analytical method is verified by a time stepped 3-D finite element analysis (FEA) for both the initial and optimized model. Finally, the VTHD, output torque and torque ripples of both the initial and optimized models are compared with 3D-FEA. The result shows that the optimized model reduces the VTHD and torque ripples as compared to the initial model. Furthermore, the result also shows that output torque increases as the result of the optimization.

Environmental Systems Research, 2019

Background: After food and water, clean air is essential for continuity of life on the planet. Co... more Background: After food and water, clean air is essential for continuity of life on the planet. Complex trans-boundary air pollution problem is often linked to sustenance and eutrophication. Air pollution problem has no universal conventions like Montreal and Kyoto protocols in case of refrigerants, except regional cooperative solutions. Polluter-pays principle is typically restricted to the source country. Under article 16, International Environment Law mentions the polluter-pay principle without any legitimate power to mitigate the transboundary air pollution risks. Mongolia, Botswana, and Pakistan are ranked as the most polluted countries, although their accumulative emissions are lesser than any of the coal power producing countries. Results: China, South Africa, and India produce 68-79% of their electricity using coal-fired power plants, emitting harmful pollutants into the common air. Regional winds drive upwind smog into their adjacent downwind countries like Pakistan. This paper compares the published transboundary air pollutant flows data of the most polluted countries (Mongolia, Botswana, Pakistan) with the cleanest ones (Estonia, Mauritius, Australia). Conclusions: Air pollution externality problem can only be solved either by regional cooperation or global environment law which yet does not exist. Drawing an analogy from water contamination laws, this work proposes an extension of the polluter-pays principle to transboundary air pollutants to compensate the public losses. We should collectively go for the international environmental law as we cannot divide air like land. Industrialization near the border may be banned to avoid air pollutant migrations to neighbors.

Renewable and Sustainable Energy Reviews, 2016

Transport of energy over long distances from remote natural sources to consumers in big cities re... more Transport of energy over long distances from remote natural sources to consumers in big cities requires technical, economic and environmental considerations. Uncertain wind flow, sunshine, faults and communication failures can compromise system safety, reliability, power quality during small signal and large scale power system oscillations. HVAC systems tackle power swing issue by electrical islanding protection schemes which would need to be revised for integrated AC/DC systems. Advent of DC transformers, CSC-HVDC, VSC-HVDC and MMC-HVDC technologies have enabled the enhancement of power delivery and integration of renewable energy sources under smart grid vision. HVDC transmission lines are recognized as an efficient alternative to HVAC lines. HVAC system power transfer capability is limited by reactance, whereas HVDC lines can be loaded up to the conductor thermal limit. This paper reviews power transfer capabilities of HVAC, HVDC and High Phase Order (HPO) HVAC lines to compare their relative performance under diverse conditions. Techno-economic analysis of converting existing AC lines into DC lines is presented. High voltage race has been analyzed in context of environmental concerns and HVDC transmission systems are concluded to be the right path to energy transition.

Journal of Magnetics, 2016

In this paper, model of the axial-flux permanent magnet synchronous generator (AFPMSG) having arc... more In this paper, model of the axial-flux permanent magnet synchronous generator (AFPMSG) having arc-shaped trapezoidal permanent magnets (PM) is presented. The proposed model reduces the cogging torque and torque ripple, at the expense of lowering the average output torque. Optimization of the proposed model is performed by considering the asymmetric overhang configuration of the PMs, as to make the output torque of the proposed model competitive with the conventional model. The time stepped 3D finite element analysis (FEA) is performed for the comparative analysis. It is demonstrated that the torque ripple of the optimized model is highly reduced as well as average output torque is increased.

Engineering, 2016

This paper reports 10 kV to 100 kV high voltage impulse generator. Generation of variable outputs... more This paper reports 10 kV to 100 kV high voltage impulse generator. Generation of variable outputs impulse generator can be designed by combination of flyback transformer and Marx generator which can produce different high voltages. It is a portable device for field. The experimental final results have been taken by using spark gap measurements and voltage divider technique. This high voltage lightning impulse generator produces standard T1/T2 waveshape impulses. The testing of protection devices such as SPD (surge protection device) is extremely important to find out whether these devices can operate in standard conditions or not. That's why the high voltage lightning impulse generator is developed for such testing. Similarly, our research work consists of modeling and practical design of a 100 kV impulse generator.

VFAST Transactions on Education and Social Sciences

Modern technology is akin to a double edged dagger, which helps when held right and hurts when tr... more Modern technology is akin to a double edged dagger, which helps when held right and hurts when tried razors side. Right technology in wrong hands becomes a dexter sinister complexity. Technology helps society to improve health, education, communication and prosperity but all at the expense of a high crime rate. Man is behind all innovatory technologies, which now have started to control the master himself. As being a victim of one’s own creation, technologists now have to look for intelligent ways that explain how we can use the same existing technology to control these rampant crimes. Technology has brought about an information revolution in our society at the expense of wreaking terrorism havoc. Security agencies use smart devices but criminals have access to smarter alternatives as well. It’s time to choose between personal freedom and collective security. We have to be cautious during public debates as media discourse creates more heat than light. Opportunities, social injustice...

Procedia Computer Science, 2015

Modern lifestyle, growing industrial and economy thrive on energy which is getting expensive over... more Modern lifestyle, growing industrial and economy thrive on energy which is getting expensive over time. Natural convection based systems are getting attraction for their promising heat transfer efficiency and zero energy utilization. Refrigerants having ozone depletion potential (ODP) and high Global Warming Potential (GWP) have been banned or under time bared permission under the Montreal (1987) and Kyoto (1997) protocols. To retrofit and modify existing cooling and heating systems, various natural and synthetic refrigerants are being investigated worldwide. We have devolved a Refrigerant Parametric Quantification (RPQ) method for the choice of optimal refrigerant for thermosyphon driven solar water heaters. A set of 29 refrigerants are simulated Using REFPROP under various temperature and pressure conditions. The optimal parameters of thermosyphon system are identified from governing equations, international environmental and safety protocols. The proposed RPQ method shows most appropriate refrigerant for given temperature range. In the second part, a glass evacuated tube collector is designed; fabricated and tested employing the best refrigerant emerged from a simulation study.

International Journal of Computer and Electrical Engineering, 2012

Proceedings of the 6th …, 2007

This work was arranged to develop the scientific database and integrate the application of lasers... more This work was arranged to develop the scientific database and integrate the application of lasers in high voltage engineering. The design and experimental studies on continuous wave (CW) / repetitively pulsed CO 2 laser was carried out in detail to determine the laser characteristics between various design parameters and the effect of varying one parameters on others. The thresholds and steady state input voltage and power across the laser tube are determined. The maximum and minimum output energy and power of the laser system are also presented as function of the pulse repetition rate and discharge current. The CO 2 laser system was operated at 10.6 µm wavelengths range of infrared electromagnetic spectrum. This study is presented due to the wide applications of CO 2 lasers in industry and for this project for CNG-DI ignition.

International Journal of Smart Grid and Clean Energy, 2013

Smart and super grid visions have attracted electrical engineers worldwide. Smart grid offers inn... more Smart and super grid visions have attracted electrical engineers worldwide. Smart grid offers innumerable advantages over conservative electric grid due to widespread integration of information and communication technologies (ICT). Information technology (IT) stimulates conscious in dumb electric grid hardware to think at its own how to operate economically in varying load conditions conducting real-time state estimation. Smart grid promises to offer bidirectional power flow capability and self-healing ability against faults. Advance metering infrastructures (AMI) help utilities track down power thefts supplying consumer home automation facilities. Smart grid helps stiff utilities to reduce operational losses and generation deficient utilities to implement live load shedding instead of revolving blackouts to help customers keeping their lights on during virtual load shedding. Smart grid promises package is subject to its complete implementation by the end of long road ahead. Communication capacity and speed limitations, cyber security risks, faults and traffic congestions have to be considered prior to rollout. This paper describes a live load shedding scheme for existing electric grids on 11kV feeders using smart grid option and evaluates technical, economic, societal and bio-effects challenges that smart grid vision might face ahead.

IEEE Access, 2020

Axial flux permanent magnet machine (AFPMM) provides high torque characteristics at low speeds wi... more Axial flux permanent magnet machine (AFPMM) provides high torque characteristics at low speeds without any mechanical gears. AFPMMs have numerous applications in wind energy, electric cars, and direct drive elevator applications. These machines have low cost and improved power to weight ratio. However, single sided AFPM suffers from torque ripples because of its non-sinusoidal back emf, cogging torque, and rotor eccentricity. There are two major components of pulsating torque, namely torque ripples and cogging torque. In PM machine design, the cogging torque is a serious concern because it adds unwanted harmonics to the pulsating torque. Whereas the torque ripples cause noise and vibrations. In order to gain high efficiency, torque ripples should be minimum. The aim of this research is to design ''Slotted axial field flux switching permanent magnet machine''. Mathematical models are used to design the machine and Finite element method (FEM) has been used to analyze the machine. In addition, Latin hypercube sampling (LHS) has been used to create the samples. Finally, Kriging Method is used for approximating the model and genetic algorithm has been applied to get the optimum machine. The results showed 61.8 % reduction of the cogging torque in the proposed machine model as compared to the conventional one. Moreover, the optimized model further provided 6.15 % reduction in the cogging torque as compared to the proposed one. INDEX TERMS Axial flux permanent magnet machine, cogging torque, slotted stator, flux switching, finite element method.

Bonfring International Journal of Power Systems and Integrated Circuits, 2019

Energy Storage, 2019

Energy storage and transportation are essential keys to make sure the continuity of energy to the... more Energy storage and transportation are essential keys to make sure the continuity of energy to the customer. Electric power generation is changing dramatically across the world due to the environmental effects of Greenhouse gases (GHG) produced by fossil fuels. The unpredictable daily and seasonal variations in demand for electrical energy can be tackled by introducing the energy storage systems (ESSs) and hence mitigating the extra GHG emission in the atmosphere. Energy storage techniques can be mechanical, electro-chemical, chemical, or thermal, and so on. The most popular form of energy storage is hydraulic power plants by using pumped storage and in the form of stored fuel for thermal power plants. The classification of ESSs, their current status, flaws and present trends, are presented in this article. The present state of fossil fuel reserves, their production, consumption, and as a consequence of these the CO 2 emissions are also discussed. The primary energy carriers coal, oil and gas are not evenly distributed along the globe. Long distances are involved in transporting these energy carriers and transportation and delivery of these key resources to the prime customers is always necessary. The different methods to transport the energy from the source end to demand end is also discussed in this article. The assessment of various energy storage methods on the basis of several factors and present status and development of storage and transportation of energy in Pakistan is discussed.

Renewable and Sustainable Energy Reviews, 2018

Refrigerant is the fluid used for heat transfer in a refrigerating system that absorbs heat durin... more Refrigerant is the fluid used for heat transfer in a refrigerating system that absorbs heat during evaporation from the region of low temperature and pressure, and releases heat during condensation at a region of higher temperature and pressure."This heat transfer generally takes place through a phase change of the refrigerant. This research studies various refrigerants used in the refrigeration system along with their effects on the environment, effects on global warming.

International Journal of Photoenergy, 2017

Smart grid for the past few years has been the prime focus of research in power systems. The aim ... more Smart grid for the past few years has been the prime focus of research in power systems. The aim is to eliminate load shedding and problematic blackout conditions, further offering cheap and continuous supply of electricity for both large and small consumers. Another benefit is to integrate renewable energy resources with existing dump grid in more efficient and cost-effective manner. In past few years, growing demand for sustainable energy increases the consumption of solar PV. Since generation from solar PV is in DC and most of the appliances at home could be operated on DC, AC-DC hybrid distribution system with energy management system is proposed in this paper. EMS helps to shift or control the auxiliary load and compel the users to operate specific load at certain time slots. These techniques further help to manage the excessive load during peak and off peak hours. It demonstrates the practical implementation of DC-AC network with integration of solar PV and battery storage wit...

The Review of Laser Engineering, 2004

This work presents a theoretical explanation and experimental evidence of pulses-intensity displa... more This work presents a theoretical explanation and experimental evidence of pulses-intensity displacement and pulse-broadening profiles of a Q-switched and mode-locked Nd:YAG laser-pumped distributed feedback dye laser (DFDL). Experimental results followed by a theoretical simulation indicate that DFDL pulses peaked noticeably later than their corresponding Nd:YAG laser pulses. The DFDL pulse corresponding to the peakpower pump laser pulse occurs few pulses later than the expected location. The observed and simulated delays were found to depend upon the inter-pulse periods of the pumping Q-switched and mode-locked laser. We report the theoretical basis for the influence of temperature grating relaxation times on the dye laser's pulse characteristics, and apply the transient grating technique to measure the refractive index of a lasing dye solution. Results indicate that the thermal effects of preceding pulses integrate the gain for receding pulses. These results provide a good understanding of temperature grating relaxation times and their impact on the lasing characteristics of DFDL.

Journal of Lightning Research, 2013

Lightning is one of the fascinating phenomena exhibiting tremendous natural power. It is source o... more Lightning is one of the fascinating phenomena exhibiting tremendous natural power. It is source of awe, curiosity, enticement, inspiration as well as fear. On average, 50 lightning strikes occur on earth in one second. Fortunately not all of them kill people, albeit 10% people fall prey to lightning annually, out of which hardly 20 to 25% die. Lightning injures victims by heat, shockwave, intense brightness, radio waves, and secondary slip or fall mechanisms. Lightning injury is different from the normal electric shock as it involves transient flashover unlike the electrical contact freeze, wherein alternating (AC) and direct currents (DC) pass through the conductive interior body. Vacuity in knowledge is the driving force behind discoveries and inventions. Lightning experts had hardly developed any concurrence on lightning physics, and the observation of dark lightning complicated the Gordian knot. Lightning preventive, alerting and control devices help reduce fatality rates by the bolts out of blue skies. Lightning was considered to be the second cause of death making natural disasters after flashfloods but preventive measures have slithered it down to the third place in developed countries. Lightning prevention rule recommends 'when the thunder roars, go indoors'. This work describes lightning characteristics, damage thresholds to humans, machines, energy infrastructures, airplanes, wind turbines, light railway tractions, underground cables and pipelines. Power and energy lifelines such as transmission lines, oil tankers and gas or petroleum pipelines are susceptible to lightning strikes. Artificial rocket and laser triggered lightning protection and control techniques help to divert the lightning attacks. Interaction of lightning with power and energy infrastructures disrupts these lifelines. However, lightning itself is viewed as an extraterrestrial energy source. Lightning energy harvesting is an interesting application which has been investigated quantitatively.