Search

Formulating highly stable graphene-based conductive inks with consistency in electrical properties over the storage period has remained a significant challenge in the development of wearable electronics. Two highly stable graphene-based inks (Cyclohexanone:Ethylene glycol (CEG) ink and Cyclohexanone:Terpineol (CT) ink) are prepared by using two different organic binary solvents, for the first time, without using solvent exchange methods. Both the inks display remarkably high stability (stable even after two months) with negligible variability in electrical properties. Here, it is demonstrated how such inks can be utilized to coat flexible substrates to create wearable e-textiles. Both the inks coated e-textiles show significantly low sheet resistance (≈209.1 Ω □−1 for CEG ink and ≈322.4 Ω □−1 CT ink) that show less than a 15% increase in electrical resistance over two months. Therefore, these inks offer high productivity and reproducibility and can be one of the most effective methods for formulating graphene-based inks.

Aim: This study aimed to evaluate the effects of discriminate and indiscriminate use of oxytetracycline on hematological parameters, residual status in soft tissue of broiler and of thermal effect on oxytetracycline residual status. Materials and Methods: Eighteen, day-old male broiler chickens were purchased and were divided into three different groups (control group, discriminate group, and indiscriminate group). The control group received no antibiotics. The discriminate group received oxytetracycline 1 g/L drinking water for 5 consecutive days, and 10 days' withdrawal period was maintained before sacrifice. The indiscriminate group received oxytetracycline 1 g/L drinking water till the sacrificed day. Blood samples were collected before sacrificing for hematological analysis. After sacrificing liver, kidney, spleen, and muscle samples were collected for analysis of oxytetracycline residues in raw soft tissues. Since meat is used to cook by traditional method in Bangladesh before consumption that is why positive meat samples were cooked by traditional cooking method to evaluate the thermal effect on oxytetracycline residual status as well. Thin-layer chromatography (TLC) was done for screening of oxytetracycline residues in soft tissues. Results: Mean differences of total erythrocyte count (million/mm3), hemoglobin estimation (gm%), and packed cell volume (%) estimation were not statistically significant among the groups. TLC analysis of raw samples showed 100% positive results of all samples collected from the indiscriminate group. In contrast, samples collected from the discriminate group were negative for oxytetracycline residues. In the control group, all samples were negative for oxytetracycline residue. There was a significant (p

Mycoflora and mycotoxin contamination are major challenges in peanut (Arachis hypogaea L.) production, trading and health concern to humans and animals. A total of 24 peanut samples out of which 12 were raw and 12 were roasted; were collected from different places in Bangladesh. These samples were examined for detection of mycoflora and mycotoxin. The mycoflora associated with the peanuts belonged to 11 fungal genera such as Aspergillus, Alternaria, Chaetomium, Cladosporium, Curvularia, Fusarium, Mucor, Penicillium, Pestalotia, Rhizopus and Trichoderma and frequencies of occurrence ranged from 0.33% to 71.95%. Aspergillus (71.95%) was the most dominant while the least was Trichoderma (0.33%). The fungal genus Aspergillus was found to be the most occurred (5501 colonies) and Pestalotia was the least occurred (25 colonies) pathogen in all samples. The highest number of fungal colonies (393) were formed in raw peanut collected from Sadarpur, Faridpur, however, the lowest number of fungal colonies (232) were formed in raw peanut collected from Potuakhali. Aspergillus was available in all the 24 samples. Penicllium was present in 12 raw peanut samples; on the other hand, Rhizopus was present in 12 samples of roasted peanuts. Aflatoxins were detected from 5 raw samples and 3 roasted samples and detection level of total aflatoxin ranged from 1.72 to 8.52 μg kg-1. The highest level of aflatoxin (8.52 μg kg-1) was detected in raw peanuts from Sibchor, Madaripur. Maximum amount of total aflatoxin among the roasted peanut was 6.71 μg kg-1 collected from Chorvodrasan, Faridpur district of Bangladesh. Finding of this study would help us in planning strategies for awareness and management of aflatoxin.

This paper focuses on the use of alternative insulating oil due to the lack of petroleum resources and concern about the environmental issues. For these purposes, a few vegetable oils available in Bangladesh are investigated for their electrical and physical properties. Vegetable oils are environmentally friendly because of their high biodegradability, low toxicity, high flash points and lower inflammability. This paper demonstrates the kinematic viscosities of sunflower oil, til oil and pithraj oil, which are found as 22.48 mm2/s, 24.81 mm2/s and 29.84 mm2/s, respectively at 20°C. The electrical breakdown voltage obtained for sunflower oil, til oil and pithraj oil are found to be 18.53 kV, 16.17 kV and 15.03 kV, respectively, for a 2.5-mm gap between electrodes at 20°C. The statistical analysis of the breakdown voltage of the vegetable oils is conducted in this paper using ‘R’ software. Finally, the experimental results are compared with mineral oil, which is generally used in distribution transformers.

Due to high heat transfer capacity, liquid dielectrics are widely used in high voltage circuit breakers, transformers and capacitors. The main purposes of liquid dielectric used in transformer are to prevent electric discharge and cooling. Dielectric strength, dissipation factor (loss tangent) which is an indication of the power loss under AC voltage application and heat transfer capacity are the important properties of dielectric materials used in transformer. Mineral oil-based transformer oil is presently used in transformer. Because of limited resources and environmental issues related to mineral oil, researchers are searching for alternative liquid dielectrics. Environmentally friendly, biodegradable vegetable oil is the potential alternative of mineral oil for used in transformer. Vegetable oils such as mustard oil, rice husk oil, palm oil and coconut oil are available in Bangladesh. The electrical and thermal properties of these oils are experimentally investigated. The experimental results are compared with the properties of mineral oil, which is generally used in transformer. It is found that palm oil is the most potential alternative insulation liquid for used in transformer.

The rapid increase in electric vehicle (EV) in Bangladesh requires more energy to run these vehicles. Moreover, the transportation sector produces Green House Gas (GHG) especially CO2 emissions. Due to the excess power needed to recharge these EVs, the national grid has to supply more than 500 MW daily. This paper proposes an Electric Vehicle Charging Station (EVCS) based on solar and biogas to reduce the burden on the national grid. The proposed EVCS integrates a combination of a solar PV module (10 kW), three biogas generators (10 kW), 25 lead acid batteries (each 100 Ah), a converter (10 kW) and charging assemblies. This paper analyzes the technical, economic and environmental feasibility of the proposed EVCS using the Hybrid Optimization of Multiple Energy Renewables (HOMER) Pro software. This configuration estimates a Cost of Energy (COE) of $0.1302/kWh, total net present cost (NPC) of $56,202 and operating cost of $2540. In addition, the proposed model reduces the CO2 emissions by 34.68% compared to a conventional grid-based charging station. The designed EVCS saves approximately $12–$18 per month to recharge an EV which increases the socio-economic standard of EV owner.

BLDC motor is broadly utilized in several fields. For achieving desired motor performance, low ripple input supply and suitable speed controller is necessary. In this paper, BLDC motor performance such as torque, stator current and speed response is analyzed. The motor is fed from solar power through three phase IBC with coupled inductor. For maximum power point tracking, Incremental Conductance algorithm is used. Interleaved converter having coupled inductor helps to minimize the voltage and current ripples. PI, PID and PD controller are applied because of enhancing the BLDC motor speed response parameters such as overshoot, peak time, rise time and settling time. Controller parameters are tuned for improving the motor performance. It is found that three phase IBC fed BLDC motor with PID controller provides superior response of BLDC motor. The proposed system is analyzed using MATLAB/Simulink software.

Bangladesh is a land of densely population. Government has taken lots of initiatives to electrify this densely populated land with conventional limited resources. To electrify this Island and rural areas many researchers proposed hybrid power generation system. Stability of on-grid hybrid power generation system is a major issue. In this paper, stability of on-grid hybrid power generation system has analyzed. The network has energized with conventional and distributed energy resources (DER) like PV and Wind. For the large power system network with renewable energy sources, it is extremely difficult and highly non-linear problem to ensure transient stability. Like many existing methods, Power system Stabilizer (PSS) is a key method to enhance the stability of renewable energy based distribution system. Projected distributed generation sourced power system with power system stabilizer elucidates both small signal stability and transient stability. The stability analysis has carried out in seven bus system. Three phase faults have considered of different faults (like three phase faults, line to ground fault, line to line faults etc.) at different bus levels in combined cycle power plant to gain stability at fault condition. Electrical Transient Analyzer Program software has used to carry out the fault clearing time for stable operation of the system. Effect of power system stabilizer on transient stability has discussed.

While lighting is a potential natural threat to a solar power generation plants and their electrical equipment, conventional protection against it has still remained inadequate. A possible reason is that the effect of lighting is not completely realized with the requirements and design considerations of the protection system. Unlike the other installations and systems susceptible to lighting, the solar panels extended over the large and open area are usually more exposed to the lightning strike. Lightning creates a strong electromagnetic field and induces extremely high voltage for a moment that can damage the photovoltaic (PV) panels, DC lines, inverter, underline cables and other equipment. In support of safety-protection, in this paper, we have modeled a Lightning Protection System (LPS) and investigate the lightning effect on a large-scale solar power plant with the proposed LPS. Additionally, we have analyzed the variations in the electromagnetic field, induced voltage and current due to lightning in the plant with the LPS using Virtual Surge Test Lab (VSTL) simulation. The presented analysis and recommendations would help to determine fundamental requirements and design considerations of an appropriate LPS for a large scale solar power plant.

Electric Vehicles are opening a promising field of engineering research which is very innovative and promising due to increasing consumer swiftly. As like other developed countries, Bangladesh is also experiencing with the use of battery electric vehicles similar to easy bike, auto rickshaw and electric bike. However, the charging stations are not sufficient and hence the electric vehicle batteries are frequently recharged from the residential connection. Due to the huge electricity consumption throughout the country, the power sector has been dropped into higher system loss and failed to earn profit from this sector. In this paper, fuzzy logic based energy management algorithm is developed for electric vehicle charging station in Bangladesh. The fuzzy optimization techniques provide different charging rate for different conditions. It will save energy and makes electric vehicle business profitable to the owner.

Coal gasification technology is an emerging technology to extract coal energy for using in many purposes including chemical production, thermal process and electrical power generation. This is comparatively a new technology for Bangladesh because of lack of financial investment, technical knowledge, support, experts and practical experiences. According to power system master plan (PSMP) of Government of Bangladesh, coal will get the highest priority as primary source of power generation. To generate clean electricity from coal, gasification is the highly efficient and environment friendly technology. Therefore, coal gasification technology has huge prospects in Bangladesh. This paper surveys the coal gasification scenarios in Bangladesh and presents the gasification technology adopted by different industries mentioning their present condition. In addition, coal gasification technology and the potential application of this technology in Bangladesh is discussed.

Solar photovoltaic system commits a fascinating energy resources due to ubiquitous and copiousness of solar energy. In the last decade, the so-called SPV technology is discussed one of the advanced technologies amongst the manifold renewable energy sources. In this proposed work, the idea of PV system, Interleaved Boost Converter (IBC) and Brushless (BLDC) motor is highlighted. For getting better efficiency with diminishing voltage and current ripples IBC are used. IBC predominantly employed for renewable energy origins having an amount of Boost Converter is joined to shunt with phase shift and the same frequency. To accomplish of interleaved converter is to diminish voltage and current ripples, good accomplishment of to power applications and prolongation efficiency. A BLDC motor is deliberated to be eminent performance due to its high reliability, little protection charge and boundless torque (T) and speed (S). To analyze and improve the performance and efficiency in terms of torque and speed using three-stage IBC fed BLDC motor with PID controller has been proposed. The modeling and MATLAB Simulink outcomes are provided to make out the theoretical exploration of PV panel, IBC and BLDC motor.

Electric Vehicles (EV) are adding new dimension in the transportation sector as well as consuming huge electric power. Although, it becomes very popular due to numerous benefits such as- limits fossil fuel consumption, increases the environmental sustainability through low GHG emission, less sound pollution and cost-effective transport medium. However, EV adoption in Bangladesh becomes very challenging due to several barriers. This paper aimed to explore the potential factors that will be the challenges for EV adoption in the context of Bangladesh. In this paper, EV penetration is studied using SWOT analysis. In addition, this paper recommends several policies to overcome those challenges of EV penetration.

Lightning causes intensive induced voltage and can be extremely harmful to a solar power plant. Particularly, due to the exposure to the open sky, Photo-Voltaic (PV) panels are highly susceptible to lightning that can damage the panels, DC lines, inverters and other equipment in the plant. To reduce this effect using a properly designed lightning protection system, in this paper, we investigate the induced voltage phenomena and its characteristics and effects on a large-scale solar power plant. The electromagnetic field and induced voltage in different places of the plant are measured by Virtual Surge Test Lab (VSTL) tool using Finite Difference Time Domain (FDTD) method. Varying characteristics of electromagnetic interference are analyzed for the soil resistance, lightning time, and lightning locations. Our early results verify that the electromagnetic field and induced voltage largely depend on the location of the lightning strike. The induced voltages are also found to vary with the increase of soil resistivity and lightning time. Presented findings would be helpful to the development of a sustainable, safe and effective large-scale solar power plant.

the Inverter is widely used for various applications such as speed control of AC motors, photovoltaic interface, flexible AC transmission system (FACTS) and power conditioning devices. In the Square wave inverter output contains a large amount of lower order harmonics. To solve the problem a large bulky filter is required. In PWM techniques the output consists harmonics of high frequency. A small filter is required at the output to get sinusoidal output. In Hybrid PWM techniques two switches operated with high frequency PWM switching signals and two switches drives by low frequency signals. This causes unequal temperature rise at the switches which decreases the reliability of the system. This reduces the overall switching loss to nearly half compared to PWM technique. In Proposed symmetrical hybrid sine PWM (SHSPWM) technique each switch operated at high frequency and low frequency alternatively and at any time two switches operated at high frequency and two switches operated at low frequency. Therefore, the total switching loss becomes half and equally distributed among the all switches which improve the reliability of the system. In this paper starting from Square wave inverter SHSPWM inverter is simulated step by step and finally SHSPWM inverter is implemented in the laboratory. The performance of implemented SHPWM inverter is analyzed in terms of efficiency and total harmonics distortions (THD).

Due to accidental trauma, war, and congenital anomalies, human beings are suffering since a long ago. Also, amputation and deformity have been carried out. Human hand has complex hierarchical control with large number of degrees of freedom. Thus, the efforts need to perform different movements are relatively small. Beside this, prosthetic arms are only an imitation of the natural hand, with considerably decreased movement freedom & clutching competencies. This paper presents the artificial myoelectric arms that an amputee needed to replace his/her amputated arms with prostheses. In this paper, acquisition of the most useful bio-signals for the prosthetic arm control is demonstrated. In addition, the process of extracting control information from the raw myoelectric signals is described. This paper describes a method to control artificial arm by dint of EMG signals.

Interleaving strategies in power DC-DC converters are gaining ever-increasing importance due to its enormous advantages. Interleaved converter having coupled inductor plays a significant role for minimizing the voltage and current ripples. This paper presents the performance of brushless DC motor fed from solar energy using coupled inductor three phase interleaved boost converter. This converter circuit is controlled by incremental conductance algorithm. The difference between uncoupled and coupled inductor three phase interleaved boost converter are presented. It is found that the output wave forms of coupled inductor three phases interleaved boost converter fed brushless DC motor are smoother than three phases interleaved boost converter fed brushless DC motor. Simulation and analysis of the system are carried out through MATLAB/Simulink.

The abrupt increase of the electric vehicles in Bangladesh needs huge amount of power. As a result, alternative energy sources are emphasized due to limited fossil fuels in order to develop a sustainable energy sector with environment friendly resources. Bangladesh has an enormous potential in the field of renewable resources like biogas and biomass. This paper presents 20 kW electric vehicle charging station (EVCS) utilizing biogas resources where maximum energy requirement is 100 kWh. In this paper, the biogas based EVCS is designed using MATLAB Simulink and HOMER software. Daily 15-20 electric vehicles can be recharged their batteries using the proposed charging station. The proposed system offers lower cost of energy compared to the grid electricity. Moreover, the proposed charging station shows 68.75% reduction in CO2 emission than grid based charging station. In addition, the proposed EVCS will save monthly $ 16.25 and $ 27.50 respectively for easy bike and auto rickshaw type electric vehicles in Bangladesh.

In spite of recent development, Bangladesh is still facing energy shortage. The country's generation plants have been unable to meet power demand over the past decade. In order to overcome not only big power plant but also a small cogeneration plant can be great effort to increase alternative energy generation in Bangladesh. The proposed model is a combination of heat and power system which can be run by bagasse and biogas. The coal is used when bagasse is not available. This research studies to explore 6 MW electricity that could be generated at North Bengal Sugar Mills, and from which 2 MW electricity will be used for its own consumption. The surplus power will be supplied to the National grid and causes earning additional revenue for the sugar mills of Bangladesh.

Energy is one of the essential requirements to alleviate poverty and socioeconomic advancement. Most of the rural area is not under the national grid; therefore, electrification in rural area is the crying need of Bangladesh. Government of the People's Republic of Bangladesh has issued its vision to bring the entire country under electricity service by the year 2030. The reserve of fossil fuel is diminishing; also the price of fuel is increasing throughout the world. Environmental pollution is another important issue. Green energy is current demand for the existence of future world. For that reason, reducing carbon emission and meeting energy demands are the main topologies to plan energy systems. As Bangladesh is an agricultural based country, biomass resources are available here and there is also good prospect of solar energy. In this paper, a solar-biomass hybrid system is proposed for electrification of rural area in Bangladesh.

Economic and reliable operation of power system is a critical foundation to support socio-economic development. Along with technical indicators, financial and commercial indices are also equally important to evaluate the performance of power transmission system. This paper proposed and analyzed a set of financial and commercial indices. Outcome of the Power Grid Company of Bangladesh over last three years were analyzed and presented. With the help of these indices, transmission operators can monitor the trends, take required actions, compare with other utility companies, fix new goals and plan for future development. Ultimately which will help to improve the transmission system performance.

A set of performance indicators are used to evaluate the performance of the Power Grid Company of Bangladesh (PGCB). This paper efforts to develop the framework and define parameters, which can be used to evaluate the operational (financial and technical) performance of Bangladesh power transmission system. This paper also evaluates the key performance indicators (KPIs) during last three fiscal years (2013-2014 to 2015-2016) of Bangladesh Transmission Grid. The obtained results are analyzed and explained in terms of KPIs. By analyzing these results a company can monitor the trend of different KPIs, take necessary actions, plan for future expansion, set targets for upcoming years and comparison can be made with international benchmarks.

Greenhouse gas emission is increasing alarmingly due to bulk electricity generation from fossil fuel such as coal, gas and oil with its limited stock. While researchers are struggling to minimize the emission using suitable mitigation techniques including renewable energy sources, the Government of Bangladesh is implementing several Coal based power plants. This paper presents mathematical model of parameters related to Greenhouse gas emission and demonstrates its emission rates resulting from various fuels used in Bangladeshi power plants. The Greenhouse gas emission from the existing fossil fuel power plants using HOMER (Hybrid Optimization of Multiple Energy Resources) software is analyzed in this research. The result shows that power plants of coal, diesel and natural gas emit 0.90 kg, 0.76 kg and 0.566 kg of CO2 per kWh, respectively. Furthermore, several Greenhouse gas mitigating procedures are proposed for fossil fuel-based power generating stations.

In this work, a new multi-circular ring perfect metamaterial absorber (PMA) with unity solar energy absorption in the infrared and visible frequency ranges is proposed. Its absorption characteristics are strongly affected by various factors, including the devices size, substrate materials, polarisation effects in the transverse electric and transverse magnetic modes, substrate thickness, resonator effects. In the designed PMA, perfect absorbance is obtained by using a multi-circular ring with low conductivity aluminum metallic patterns and a gallium arsenide dielectric substrate. The commercially available CST microwave studio based on a finite integration technique and High Frequency Structural Simulator (HFSS) are utilised to investigate the absorption parameters of the proposed structure. The PMA absorbance spectrum covers both the infrared and visible frequencies due to the excitation of different magnetic and electric modes. In addition, the PMA application as a permittivity sensor is examined as well. It exhibits almost perfect absorbances equal to 99.74% and 99.23% at 245.03 and 376.13 THz in the infrared region and 99.82% at 502.10 THz in the visible region, respectively. The results of numerical simulations demonstrate that the proposed configuration is insensitive to polarisation angle. Hence, the designed metamaterial absorber is characterised by the perfect absorption in the infrared and visible frequency ranges and can be used for renewable solar energy harvesting as well as, for stealth technology, sensing, and imaging applications. Keywords: Infrared and visible frequencies, Perfect metamaterial absorber, Polarisation, Solar energy harvesting

Damages of buried energy pipeline due to direct Lightning strikes on ground has recently appeared substantially noticeable. This paper presents comprehensive study of damages on energy pipelines buried under homogeneous soil due to direct strike on ground over/near the pipeline. The induced voltage on pipeline is analysed using electromagnetic analysis approach. A model was developed to simulate a portion of a pipeline system under varying ground, geometry and lightning parameters, like, lightning current amplitude, rise time, ground resistivity and permittivity, burial depth, and distance of strike point to the buried pipeline. The result showed that induced effect greatly depend on soil electromagnetic parameters and also to strike locations. This paper also presents mutual relationship among horizontal magnetic field and induced current, along with the effect of lightning stroke location and distance from the buried pipeline on the induced disturbances.

Accidents caused by natural phenomena such as lightning are serious problems for the diffusions of wind power generations. To exploit high wind conditions, wind turbine generators are often constructed along the seashore where few tall structures exist; therefore, they are often struck by lightning. Most of the breakdowns and malfunctions of the electrical and control systems inside wind turbine due to lightning are caused by the voltage rise of the grounding system. At a disposal site like seashore where the resistivity of soil is very low, the voltage rise at grounding at the wave front typically becomes larger than that of the steady state because of the inductive behaviour of the grounding system. Voltage rise at grounding of wind turbine due to lightning at a disposal site are computed using electromagnetic analysis approach, and designing of proper grounding system at low resistivity soil is discussed. Finite Difference Time Domain (FDTD) method is used for electromagnetic analysis. Designing of grounding system of wind turbine at a disposal site is discussed.

In this paper, lightning induced overvoltage on DC cables of solar power panel, which was laid on the ground and an underground level with proper insulation thickness, was investigated when a lightning strike at a nearby place and its proper protection scheme was verified. The result shows that on ground cable voltage is approximately 28.83% more than that of the underground cable having soil resistivity 100Ω-m. Moreover, when soil resistivity increases to 1000Ω-m then the underground cable voltage is less about 48.50% than that of the on ground cable. The induced voltage caused by lightning electromagnetic interference on DC cables of solar power system at power conditioning subsystem (PCS) is analysed using electromagnetic field analysis approach. The FDTD method was applied to calculate induced voltage. Virtual Surge Test Lab (VSTL) is used for FDTD calculations, which solve Maxwell's electromagnetic equations with least approximations. The model of solar power system was represented with thin wires.

Scarcity in energy sector is a major problem, which can hamper the growing development of a country. Bangladesh is one of the electricity-deprived countries; however, the energy demand of Bangladesh is increasing day by day. Due to the shortage of natural resources and environmental issues, many nations are now moving towards renewable energy. Among various form of renewable energy, wind energy is one of most potential source. In this paper, the present energy condition of Bangladesh is discussed and the necessity of moving towards renewable energy is clarified. The wind speed found at different locations at different heights and different years from the survey of several organizations are presented. Although, the results of installed low capacity wind turbines (from few kW to few tens of kW) operated by private or government organization at different places in Bangladesh are not so encouraging; however, it is shown that Bangladesh has a high potential of using large wind turbine (MW range) for capturing wind energy at different places. The present condition of wind energy in Bangladesh and other countries in the world are also presented to emphasize the requisite of moving towards wind energy.

IEC TR61400-24 [1] suggests interconnection of grounding electrodes of wind turbines through horizontal electrodes (in the form of insulated or bare conductors) to achieve low steady-state grounding resistance, however, the transient behavior during a lightning strike to an interconnected wind turbine grounding system remains to be discussed. The performance of a large grounding system depends on the wave propagation characteristics through the grounding electrodes. The fundamental wave propagation characteristics through an interconnected wire of wind turbine grounding are studied with the help of Finite Difference Time Domain (FDTD) method. Effectiveness of interconnection of wind turbine grounding is discussed. The influence of soil parameters, distance between turbines, impedance of the wind turbine grounding and the type of a conductor employed for interconnection on the effectiveness of interconnection of wind turbine grounding is also discussed.

IEC TR61400-24 [1] suggests interconnection of the grounding system of wind turbines to achieve low steady-state resistance, however, the transient behavior during a lightning strike to the interconnected wind turbine grounding system remains to be discussed. This paper investigates the influence of interconnection on the lightning surge response of wind turbine grounding system. Two different numerical methods, Numerical Electromagnetics Code (NEC-4) based on Method of Moments (MoM), and Virtual Surge Test Lab (VSTL) based on Finite Difference Time Domain (FDTD) method are used for electromagnetic analysis of lightning surge response of wind turbine grounding system. Comparison of results using NEC-4 and VSTL are made to clarify the usefulness of these methods for transient analysis of a large grounding system. The influences of resistivity of soil and front time of lightning impulse current, on the response of interconnected wind turbine grounding system are analyzed.

The characteristics of Cuk converters in discontinuous-capacitor-voltage mode are studied. A Cuk converter in this mode of operation is an inherent power factor corrector and features soft turn of switching. This paper proposes a Cuk converter in discontinuous-capacitor-voltage mode (DCVM) operation in order to reduce the total harmonic distortion (THD) of a three-phase rectifier. In the proposed circuit pulse width modulation (PWM) is used to regulate the output voltage. A small series LC filter is used at the input side to suppress the low frequency harmonics components that may pass to the input. Some simulation results are presented. The variation of output voltage, THD of input current and power factor with duty cycle of the proposed converter circuit are also presented in this paper.

Voltage sags and extended under voltages have the largest negative impact on industrial productivity and could be the most important type of power quality variation for many industrial and commercial customers. This paper proposes a 3-phase PWM ac-ac Cuk converter with minimum switches to maintain constant output voltage irrespective of the variation of input voltage and load. By PWM duty ratio control the ac-ac converter become a ldquosolid state transformerrdquo with a continuously variable turns ratio. The proposed ac-ac converter employ only two switches compared to the existing circuits that use six switches or more. For minimum number of switches the proposed circuit reduces cost, improves reliability. The operating principle, control method and simulation results of the proposed converter circuit are presented in this paper.

Power quality describes the quality of voltage and current and is one of the most important considerations in domestic, industrial, and commercial applications today. Power quality problems commonly faced are transients, sags, swells, surges, outages, harmonics, and impulses. Among these voltage sags and extended under voltages have the largest negative impact on industrial productivity, and could be the most important type of power quality variation for many industrial and commercial customers. Voltage sags is mainly due to the fault occurring in the transmission and distribution system, loads like welding and operation of building construction equipment, switching of the loaded feeders or equipments. Continuous voltage sags are also prevalent in many areas due to inadequate supply and demand situation. In this paper a switch mode AC voltage regulator is proposed to maintain constant voltage across a medium size domestic or commercial appliance. The proposed regulator has the capability of delivering sinusoidal input current with nearly unity power factor and the efficiency of the proposed regulator is high. This system incorporates high-speed insulated gate bipolar transistor switching technology. In this regulator the gate signal of the switching devices is generated by using a compact and commercially available IC chip SG1524B.