Spacecraft bus voltage is regulated by power
conditioning unit using switching shunt voltage regulator having
solar array cells as the primary source of power. This source
switches between the bus loads and the shunt switch for fine
control of spacecraft bus voltage. The effect of solar array cell
capacitance [5][6] along with inductance and resistance of the
interface wires between solar cells and power conditioning
unit[1], generates damped sinusoidal currents superimposed on
the short circuit current of solar cell when shunted through
switch. The peak current stress on the shunt switch is to be
considered in the selection of shunt switch in power conditioning
unit. The analysis of current transients of shunt switch in PCU
considering actual spacecraft interface wire length by
illumination of solar panel (combination of series and parallel
solar cells) is difficult with hardware simulation. Software
simulation by modeling solar cell is carried out for a single string
(one parallel) in Pspice [6]. Since in spacecrafts number of
parallels and interface cable length are variable parameters the
analysis of current transients of shunt switch is carried out by
modeling solar array with the help of solar cell model[6] for the
actual spacecraft condition.
ER Publication,
IJETR, IJMCTR,
Journals,
International Journals,
High Impact Journals,
Monthly Journal,
Good quality Journals,
Research,
Research Papers,
Research Article,
Free Journals, Open access Journals,
erpublication.org,
Engineering Journal,
Science Journals,
SIMULATION AND ASSESSMENT OF SINGLE PHASE SEMI-Z-SOURCE INVERTER (S-ZSI)IAEME Publication
The present investigation is a step towards the development of a single phase semi-Z-source inverter (s-ZSI) with photovoltaic, its topology and the assessment with respect to the voltage and current output. The proposed semi-Z-source inverter use only two active switches to achieve a desired output. The simulation was carried out using MATLAB and the results are discussed in various waveforms.
ER Publication,
IJETR, IJMCTR,
Journals,
International Journals,
High Impact Journals,
Monthly Journal,
Good quality Journals,
Research,
Research Papers,
Research Article,
Free Journals, Open access Journals,
erpublication.org,
Engineering Journal,
Science Journals,
SIMULATION AND ASSESSMENT OF SINGLE PHASE SEMI-Z-SOURCE INVERTER (S-ZSI)IAEME Publication
The present investigation is a step towards the development of a single phase semi-Z-source inverter (s-ZSI) with photovoltaic, its topology and the assessment with respect to the voltage and current output. The proposed semi-Z-source inverter use only two active switches to achieve a desired output. The simulation was carried out using MATLAB and the results are discussed in various waveforms.
ANALYSIS OF LIGHTNING STRIKE WITH CORONA ON OHTL NEAR THE SUBSTATION BY EMTP ADEIJ Journal
Lightning protection and insulation coordination of transmission lines and substations require an accurate
knowledge of the magnitudes and waveforms of lightning overvoltage. To simulate the lightning
overvoltage precisely near the substation, this study has shown how to consider the lightning impulse
corona for distortion effect of this overvoltage.
Optimal Placement of Static Series Voltage Regulator (SSVR) in Distribution S...IJERA Editor
This paper presents optimal placement of Static Series Voltage Regulator (SSVR), for voltage profile improvement and power loss reduction in radial distribution systems under steady state condition. SSVR consists of a series compensator. The series compensator injects the series voltage in quadrature with the branch current in such a way that the receiving end voltage is maintained at desired value (up to 1 p.u). The criteria for selection of optimum location of SSVR are under voltage problem mitigation and loss reduction in the network under steady sate condition. Particle Swam Optimization (PSO) technique is used to find the rating of the device. The proposed model is tested using standard distribution system consisting of 33 nodes
Novel technique in charactarizing a pv module using pulse width modulatoreSAT Journals
Abstract The fabrication and characterization of PV modules are always done under standard test conditions (STC). However, The condition of operation are often far from thisstandard conditions. As a result, developing a characterization circuit is considered as a point of interest for researchers.This paper presents a new methodology in characterizing a PV module using an electronic load circuit. The circuit is implemented using a power MOSFET driven by a pulse width modulator (PWM) developed by LABVIEW. The system is tested and its results are validated by comparing it with simulation results performed by Comsol Multiphysics and Matlab. The system shows high accuracy with respect to the previous published work with lower cost and higher simplicity. Keywords: Photovoltaic, Characterization, Electronic load, and Pulse width modulation (PWM)…
The projected diode assisted Neutral Point Diode Clamed (NPC-MLI) with the photovoltaic system produces a maximum voltage gain that is comparatively higher than those of other boost conversion techniques. This paper mainly explores vector selection approach pulse-width modulation (PWM) strategies for diode-assisted NPC-MLI to obtain a maximum voltage gain without compromising in waveform quality. To obtain a high voltage gain maximum utilization of dc-link voltage and stress on the power switches must be reduced. From the above issues in the diode assisted NPC-MLI leads to vector selection approach PWM technique to perform capacitive charging in parallel and discharging in series to obtain maximum voltage gain. The operation principle and the relationship of voltage gain versus voltage boost duty ratio and switching device voltage stress versus voltage gain are theoretically investigated in detail. Owing to better performance, diode-assisted NPC-MLI is more promising and competitive topology for wide range dc/ac power conversion in a renewable energy application. Furthermore, theoretically investigated are validated via simulation and experimental results.
Representing Tap-changer Transformers in Conic Relaxation Optimal Power Flowsinventionjournals
Conic optimization has been applied optimal power flow (OPF) problem recently. Present conic relaxation OPFs only consider for the continuous decision variables, and the transformer tap ratios have not been treated as optimization variables. Based on angle relaxed branch power flow, an extended branch power flow model with tap-changer transformers is proposed. The tap-changer transformers were modeled with bilinear functions. Then the McCormick envelopes were deployed to exactly reformulate the bilinear functions with linear constrains. The effectiveness of the proposed method is demonstrated by the simulation results obtained in the test systems
A single stage photo voltaic grid-connected inverter using spwmSHAIK AMANULLA
A Single-stage PhotoVoltaic Grid-Connected Inverter using SPWM. It was simulated and modeled with MATLAB/SIMULINK. It was simulated with constant and variable irradiation profiles. I got the results with variations in PV characteristics with different irradiation with SPWM technique.
Simulation Model for PV Array & Its CharacteristicsIJEEE
This paper presents the implementation of a photovoltaic model using Matlab software, which can be representative of PV cell module, and array for easy use on simulation. The proposed model is designed with a user-friendly icon and a dialog box like Simulink block libraries. This makes the PV model easily simulated and analyzed in conjunction with power electronics for a maximum power point tracker.
ANALYSIS OF LIGHTNING STRIKE WITH CORONA ON OHTL NEAR THE SUBSTATION BY EMTP ADEIJ Journal
Lightning protection and insulation coordination of transmission lines and substations require an accurate
knowledge of the magnitudes and waveforms of lightning overvoltage. To simulate the lightning
overvoltage precisely near the substation, this study has shown how to consider the lightning impulse
corona for distortion effect of this overvoltage.
Optimal Placement of Static Series Voltage Regulator (SSVR) in Distribution S...IJERA Editor
This paper presents optimal placement of Static Series Voltage Regulator (SSVR), for voltage profile improvement and power loss reduction in radial distribution systems under steady state condition. SSVR consists of a series compensator. The series compensator injects the series voltage in quadrature with the branch current in such a way that the receiving end voltage is maintained at desired value (up to 1 p.u). The criteria for selection of optimum location of SSVR are under voltage problem mitigation and loss reduction in the network under steady sate condition. Particle Swam Optimization (PSO) technique is used to find the rating of the device. The proposed model is tested using standard distribution system consisting of 33 nodes
Novel technique in charactarizing a pv module using pulse width modulatoreSAT Journals
Abstract The fabrication and characterization of PV modules are always done under standard test conditions (STC). However, The condition of operation are often far from thisstandard conditions. As a result, developing a characterization circuit is considered as a point of interest for researchers.This paper presents a new methodology in characterizing a PV module using an electronic load circuit. The circuit is implemented using a power MOSFET driven by a pulse width modulator (PWM) developed by LABVIEW. The system is tested and its results are validated by comparing it with simulation results performed by Comsol Multiphysics and Matlab. The system shows high accuracy with respect to the previous published work with lower cost and higher simplicity. Keywords: Photovoltaic, Characterization, Electronic load, and Pulse width modulation (PWM)…
The projected diode assisted Neutral Point Diode Clamed (NPC-MLI) with the photovoltaic system produces a maximum voltage gain that is comparatively higher than those of other boost conversion techniques. This paper mainly explores vector selection approach pulse-width modulation (PWM) strategies for diode-assisted NPC-MLI to obtain a maximum voltage gain without compromising in waveform quality. To obtain a high voltage gain maximum utilization of dc-link voltage and stress on the power switches must be reduced. From the above issues in the diode assisted NPC-MLI leads to vector selection approach PWM technique to perform capacitive charging in parallel and discharging in series to obtain maximum voltage gain. The operation principle and the relationship of voltage gain versus voltage boost duty ratio and switching device voltage stress versus voltage gain are theoretically investigated in detail. Owing to better performance, diode-assisted NPC-MLI is more promising and competitive topology for wide range dc/ac power conversion in a renewable energy application. Furthermore, theoretically investigated are validated via simulation and experimental results.
Representing Tap-changer Transformers in Conic Relaxation Optimal Power Flowsinventionjournals
Conic optimization has been applied optimal power flow (OPF) problem recently. Present conic relaxation OPFs only consider for the continuous decision variables, and the transformer tap ratios have not been treated as optimization variables. Based on angle relaxed branch power flow, an extended branch power flow model with tap-changer transformers is proposed. The tap-changer transformers were modeled with bilinear functions. Then the McCormick envelopes were deployed to exactly reformulate the bilinear functions with linear constrains. The effectiveness of the proposed method is demonstrated by the simulation results obtained in the test systems
A single stage photo voltaic grid-connected inverter using spwmSHAIK AMANULLA
A Single-stage PhotoVoltaic Grid-Connected Inverter using SPWM. It was simulated and modeled with MATLAB/SIMULINK. It was simulated with constant and variable irradiation profiles. I got the results with variations in PV characteristics with different irradiation with SPWM technique.
Simulation Model for PV Array & Its CharacteristicsIJEEE
This paper presents the implementation of a photovoltaic model using Matlab software, which can be representative of PV cell module, and array for easy use on simulation. The proposed model is designed with a user-friendly icon and a dialog box like Simulink block libraries. This makes the PV model easily simulated and analyzed in conjunction with power electronics for a maximum power point tracker.
Performance analysis of aodv with the constraints of varying terrain area and...Editor Jacotech
Mobile Ad Hoc Networks (MANETs) are wireless networks,
where there is no requirement for any infrastructure support to
transfer data packets between mobile nodes. These nodes
communicate in a multi-hop mode; each mobile node acts
both as a host and router. The main job of Quality of Service
(QoS)[1][2] routing in MANETs is to search and establish
routes among different mobile nodes for satisfying QoS
requirements of wireless sensor networks as PDR, Average
end-to-end delay, Average Throughput. The QoS routing
protocols efficient for commercial, real-time and multimedia
applications are in demand for day to day activities[2].
Traffic Detection System is an Android application that aims at determining the behavior of traffic in a particular location. It calculates the speed of the vehicle and the level of congestion or the amount of traffic is determined on the basis of the values of sensors. If any such obstruct found, then the driver is provided an option to send messages regarding high traffic to his/her friends. After a distinct number of repeated low speed and breaks, the location of the vehicle (latitude and longitude) send to a pre-specified contact (selected in case of traffic congestion) through an SMS. This application uses the features of the Global positioning system. The Latitude, as well as the longitude of the location where traffic jams are formed, is sent to the friends of the user. The Goggle map of the location also sends to the friends. It uses the SMS Manager a functionality of Android. The friends receiving the messages will thereby avoid taking the congested route and hence the level of traffic on the congested road will decrease, and the friends will reach the destination in comparatively less time.
The electric power supplied by a photovoltaic power generation system depends on the solar radiation and temperature. Designing efficient PV systems heavily emphasizes to track the maximum power operating point.
This work develops a three-point weight comparison method that avoids the oscillation problem of the perturbation and observation algorithm which is often employed to track the maximum power point. Furthermore, a low cost control unit is developed, based on a single chip to adjust the output voltage of the solar cell array.
Fingertip Knowledge - Electronic Performance Support SystemsKelly Condron
O/E Learning and LearningGuide co-facilitated this workshop at the Corporate University Week in November 2008.
During the three-hour workshop, participants learned how to design and develop “point-of-need” self-instruction for an EPSS via blended, experiential, and hands-on learning methodologies.
Professional competency, capacity-building and
academia empowerment are the concepts, with marginal
differences and interchangeably need. The prime purpose is
equipping the academia with the technology of effective teaching.
University tertiary academia has been academically regarded the
symbol of knowledge. In many ways this subject knowledge,
although a matter in its own right, formed the classical nation.
Many other sets of variables associated with human aspects,
increases participation in higher education of all students
advantaged and dis advantaged, mixed campus environments,
learning materials and technologies are the grown concern which
calls for a new vision and strategy. Within this frame work, this
study focused on identification of the contents of professional
competency, the patterns of academic performance and judges
their wholesome effects on students’ performance. In depth
review of relevant literature in major areas (professional
Competency, roll of academia, teaching strategy, factor effective
teaching, teaching learning styles, diversified types influencing
academia competency, indicators of professional competency,
interpersonal relationships, ethics, reflections, communication
skills, knowledge of subject matters, pedagogical/androgogical
knowledge, students assessment, academics performance and its
indicators, tertiary students study skills, and associations aspects)
indicated the variables and form the basis of the study
Carbon nano tube based delay model for high speed energy efficient on chip da...elelijjournal
Speed is a major concern for high density VLSI networks. In this paper the closed form delay model for current mode signalling in VLSI interconnects has been proposed with resistive load termination.RLC interconnect line is modelled using characteristic impedance of transmission line and inductive effect.The inductive effect is dominant at lower technology node is modelled into an equivalent resistance. In this model first order transfer function is designed using finite difference equation, and by applying the boundary conditions at the source and load termination. It has been observed that the dominant pole determines system response and delay in the proposed model. Using CNIA tool (carbon nanotube interconnect analyzer) the interconnect line parameters has been estimated at 45nm technology node. The novel proposed current mode model superiority has been validated for CNT type of material. It superiority factor remains to 66.66% as compared to voltage mode signalling. And current mode dissipates 0.015pJ energy where as VM consume 0.045pJ for a single bit transmission across the interconnect over CNT
material. Secondly the damping factor of a lumped RLC circuit is shown to be a useful figure of merit.
The International Journal of Engineering and Science (IJES)theijes
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
International Journal of Engineering Research and DevelopmentIJERD Editor
Electrical, Electronics and Computer Engineering,
Information Engineering and Technology,
Mechanical, Industrial and Manufacturing Engineering,
Automation and Mechatronics Engineering,
Material and Chemical Engineering,
Civil and Architecture Engineering,
Biotechnology and Bio Engineering,
Environmental Engineering,
Petroleum and Mining Engineering,
Marine and Agriculture engineering,
Aerospace Engineering.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Comparative Evaluation of Generalized Multicell Impedance Source Inverter for...IJPEDS-IAES
Voltage-Source Inverter is limited by its only voltage step-down operation. In adding with extra boosting the flexibility is kept active for the number of semiconductors which is unchanged, voltage-type Z-source inverter was earlier proposed. This new class of inverter is generally less sensitive to electromagnetic noises. However, their boosting capabilities are anyhow less with high component stresses and poorer spectral performances caused by low modulation index ratios. Their boosting gains are, therefore, restricted in practice. To overcome these we use the generalized switched-inductor Z- source inverter is proposed, By comparing with PWM technique and SPWM technique, whose extra boosting abilities and other advantages have been verified in simulation analysis and experiment.
Wireless power transfer (WPT) is a technique introduced to transfer power wirelessly. Generally, WPT systems are characterized by low efficiency and low output power. Since WPT process depends mainly on mutual coupling between transmitting and receiving coils in addition to load requirements, it is focused in this work toward enhancing the mutual coupling and conditioning the receiving circuit so as to optimally satisfy the load demand. The mutual coupling between transmitting and receiving nodes is enhanced via inserting three resonating circuits along with energy transmission path and conditioning the receiving circuit such that it accomplishes delivering maximum power to the load node. In this work, an adaptive efficient WPT system is introduced. This system is carried out on PSpice and validated experimentally. Both simulative and experimental WPT systems have accomplished significant enhancement in efficiency. The proposed WPT system has three resonators and three parallel connected identical receiving coils located at 6.61m from the power transmitter. The efficiency enhancement approaches thousands of times the efficiency of a conventional WPT system having similar power transmitter located at the same distance from the receiving circuit, which has a single coil identical to those in the proposed efficient WPT system.
The transmission of electric power has to take place in the most efficient way in addition to providing flexibility in the process. Flexible A.C. Transmission System (FACTS) promotes the use of static controllers to enhance the controllability and increase the power transfer capability. Providing reactive shunt compensation with shunt-connected capacitors and reactors is a well-established technique to get a better voltage profile in a power system. Shunt Capacitors are inexpensive but lack dynamic capabilities, thus some form of dynamically controlled reactive power compensation becomes essential. In this paper, three phase Distribution Static Var Compensator (D-SVC) has been developed and studied under different conditions. Open loop mode and closed loop mode of operation of D-SVC is simulated and studied. The work presented here is very much useful for distribution system, for effective reactive power management and better Voltage control.
The high penetration of power electronic based distributed energy resources (DERs) has increased the importance and attention given to voltage security of distribution systems. Voltage control in the electrical power system is critical for a proper operating condition. Therefore, distribution systems must have the ability to maintain a secure voltage profile. Using inverters for Volt/VAR control (VVC) can provide a faster response for voltage regulation than traditional voltage regulation devices, such as transformer load tap changers and voltage regulators. The primary objective of this paper is to demonstrate how smart inverters can be used to eliminate the voltage deviation by solving a mixed-integer quadratic program to determine the amount of reactive power that should be injected or absorbed at the appropriate nodes. The proposed method incorporates capacitor banks connected to the network and determines whether to turn on or off the capacitor bank for voltage regulation. These processes will be demonstrated in several cases that are focused on mitigating voltage-dips and swells.
The high penetration of power electronic based distributed energy resources (DERs) has increased the importance and attention given to voltage security of distribution systems. Voltage control in the electrical power system is critical for a proper operating condition. Therefore, distribution systems must have the ability to maintain a secure voltage profile. Using inverters for Volt/VAR control (VVC) can provide a faster response for voltage regulation than traditional voltage regulation devices, such as transformer load tap changers and voltage regulators. The primary objective of this paper is to demonstrate how smart inverters can be used to eliminate the voltage deviation by solving a mixed-integer quadratic program to determine the amount of reactive power that should be injected or absorbed at the appropriate nodes. The proposed method incorporates capacitor banks connected to the network and determines whether to turn on or off the capacitor bank for voltage regulation. These processes will be demonstrated in several cases that are focused on mitigating voltage-dips and swells.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Similar to Modeling of solar array and analyze the current transient response of shunt switch voltage regulator in spacecraft power conditioning unit (20)
Performance of Wideband Mobile Channel with Perfect Synchronism BPSK vs QPSK ...Editor Jacotech
Direct-sequence code-division multiple access (DS-CDMA) is
currently the subject of much research as it is a promising
multiple access capability for third and fourth generations
mobile communication systems. The synchronous DS-CDMA
system is well known for eliminating the effects of multiple
access interference (MAI) which limits the capacity and
degrades the BER performance of the system. In this paper,
we investigate the bit error rate (BER) performance of a
synchronous DS-CDMA system over a wideband mobile
radio channel. The BER performance is affected by the
difference in path length ΔL and the number of arriving
signals N. Furthermore, the effect of these parameters is
examined on the synchronous DS-CDMA system for different
users’ number as well as different processing gain Gp. In this
environment and under the above conditions the performances
of the BPSK (Binary Phase Shift Keying) and the QPSK
(Quadrature Phase Shift Keying) modulations are compared.
The promising simulation results showed the possibility of
applying this system to the wideband mobile radio channel.
MOVIE RATING PREDICTION BASED ON TWITTER SENTIMENT ANALYSISEditor Jacotech
With microblogging platforms such as Twitter generating
huge amounts of textual data every day, the possibilities of
knowledge discovery through Twitter data becomes
increasingly relevant. Similar to the public voting mechanism
on websites such as the Internet Movie Database (IMDb) that
aggregates movies ratings, Twitter content contains
reflections of public opinion about movies. This study aims to
explore the use of Twitter content as textual data for
predicting the movie rating. In this study, we extract number
of tweets and compiled to predict the rating scores of newly
released movies. Predictions were done with the algorithms,
exploring the tweet polarity. In addition, this study explores
the use of several different kinds of tweet classification
Algorithm and movie rating algorithm. Results show that
movie rating developed by our application is compared to
IMDB and Rotten Tomatoes.
Non integer order controller based robust performance analysis of a conical t...Editor Jacotech
The design of robust controller for any non linear process is a
challenging task because of the presence of various types of
uncertainties. In this paper, various design methods of robust
PID controller for the level control of conical tank are
discussed. Uncertainties are of different types, among that
structured uncertainty of 30% is introduced to the nominal
plant for analysing the robustness. As a first step, the control
of level is done by using conventional integer order controller
for both nominal and uncertain system. Then, the control is
done by means of Fractional Order Proportional Integral
Derivative (FOPID) controller for achieving robustness. With
the help of time series parameters, a comparison is made
between conventional PID and FOPID with respect to the
simulated output using MATLAB and also analyzed the
robustness.
FACTORS CAUSING STRESS AMONG FEMALE DOCTORS (A COMPARATIVE STUDY BETWEEN SELE...Editor Jacotech
It is an important task of working women to handle two
important tasks. Balancing these two roles at home and
work is very challenging task and causes stress at different
levels. Different dimension of working women’s life
involves in evolving the stress in working women’s life.
These stresses cause the imbalance at the front of and
handling family responsibility. In the current scenario,
doctors face many stressors that are peculiar to the medical
profession and doctors are required to have more
competencies than before in diagnosis ongoing
management of medical conditions. This means increased
responsibilities which may contribute to stress. Stress
experienced at work can have adverse outcomes for the
well-being of individual employees and organization as
whole. My study is focusing on identifying the factors
causing stress among female doctors working for public
and private hospitals and their stress levels associations
with respect to sector. A sample of 300 female doctors
from urban area participated in this study. Out of this, 150
each are from public and private hospitals respectively. A
self-made standardized tool was administered based on five
point scale. Results indicates that the values were found to
be 0.000 in all the cases except, psychosomatic problems
(0.004) which is lesser than (0.05) p-value resulting into
rejection of null hypotheses , consequently revealing an
association between sector of female doctors and stress due
to workload, working condition, physical exertion,
emotional exhaustion, job security, organizational support,
work family conflict, family adjustment, task demands,
psychosomatic problems, patient’s expectation and working
hours.
ANALYSIS AND DESIGN OF MULTIPLE WATERMARKING IN A VIDEO FOR AUTHENTICATION AN...Editor Jacotech
Watermarking technique be employ instance & for a second time for
validation and protection of digital data (images, video and audio
files, digital repositories and libraries, web publishing). It is helpful
to copyright protection and illegal copying of digital data like video
frames and making digital data more robust and imperceptible. With
the advent of internet, creation and delivery of digital data has grown
many fold. In that Scenario has to need a technique for transferring
digital data securely without changing their originality and
robustness. In this paper proposed a plan of latest watermarking
method which involves inserting and adding two or more digital data
or pictures in a single video frame for the principle of protection and
replicate the similar procedure for N no video frames for
authentication of entire digital video. After that digital video is
encrypted and decrypted by using motion vector bit-xor encryption
and decryption technique.
The Impact of Line Resistance on the Performance of Controllable Series Compe...Editor Jacotech
In recent years controllable FACTS devices are increasingly
integrated into the transmission system. FACTS devices that
provide series control such as Controllable Series Compensator
(CSC) has significant effect on the voltage stability of Electric
Power system. In this work impact of line resistance on the
performance of CSC in a single-load infinitive-bus (SLIB)
model is investigated. The proposed framework is applied to
SLIB model and obtained results demonstrates that line
resistance has considerable effect on voltage stability limits and
performance of CSC.
Security Strength Evaluation of Some Chaos Based Substitution-BoxesEditor Jacotech
Recently, handful amount of S-boxes, using the various
methods such as affine transformations, gray coding,
optimization, chaotic systems, etc, have been suggested. It is
prudent to use cryptographically strong S-boxes for the design
of powerful ciphers. In this paper, we sampled some widely
used 8×8 S-boxes which are recently synthesized and security
analysis and evaluation is executed to uncover the best
candidate(s). The performance analysis is exercised against
the crucial measures like nonlinearity, linear approximation
probability, algebraic immunity, algebraic complexity,
differential uniformity. These parameters are custom selected
because their scores decide the security strength against
cryptographic assaults like linear cryptanalysis, algebraic
attacks, and differential cryptanalysis. The anticipated
analysis in this work facilitates the cryptographers, designers,
researchers to choose suitable candidate decided over many
parameters and can be engaged in modern block encryption
systems that solely rely on 8×8 S-box. Moreover, the analysis
assists in articulating efficient S-boxes and to evaluate the
attacks resistivity of their S-boxes.
License plate recognition an insight to the proposed approach for plate local...Editor Jacotech
License Plate Recognition (LPR) system for vehicles is an innovative and a very challenging area for research due to the innumerous plate formats and the nonuniform outdoor illumination conditions during which images are acquired. Thus, most approaches developed, work under certain restrictions such as fixed illumination, stationary background and limited speed. Algorithms developed for LPR systems are generally composed of three significant stages: 1] localization of the license plate from an entire scene image; 2] segmentation of the characters on the plate; 3] recognition of each of the segmented characters. A simple approach for preprocessing of the images, localization and extraction phase has been described in this paper. Numerous procedures have been developed for LPR systems and are assessed in this paper taking into consideration issues like processing time, computational power and recognition rate wherever available.
Design of airfoil using backpropagation training with mixed approachEditor Jacotech
Levenberg-Marquardt back-propagation training method has some limitations associated with over fitting and local optimum problems. Here, we proposed a new algorithm to increase the convergence speed of Backpropagation learning to design the airfoil. The aerodynamic force coefficients corresponding to series of airfoil are stored in a database along with the airfoil coordinates. A feedforward neural network is created with aerodynamic coefficient as input to produce the airfoil coordinates as output. In the proposed algorithm, for output layer, we used the cost function having linear & nonlinear error terms then for the hidden layer, we used steepest descent cost function. Results indicate that this mixed approach greatly enhances the training of artificial neural network and may accurately predict airfoil profile.
Ant colony optimization based routing algorithm in various wireless sensor ne...Editor Jacotech
Wireless Sensor Network has several issues and challenges due to limited battery backup, limited computation capability, and limited computation capability. These issues and challenges must be taken care while designing the algorithms to increase the Network lifetime of WSN. Routing, the act of moving information across an internet world from a source to a destination is one of the vital issue associated with Wireless Sensor Network. The Ant Colony Optimization (ACO) algorithm is a probabilistic technique for solving computational problems that can be used to find optimal paths through graphs. The short route will be increasingly enhanced therefore become more attractive. The foraging behavior and optimal route finding capability of ants can be the inspiration for ACO based algorithm in WSN. The nature of ants is to wander randomly in search of food from their nest. While moving, ants lay down a pheromone trail on the ground. This chemical pheromone has the ability to evaporate with the time. Ants have the ability to smell pheromone. When selecting their path, they tend to select, probably the paths that has strong pheromone concentrations. As soon as an ant finds a food source, carries some of it back to the nest. While returning, the quantity of chemical pheromone that an ant lay down on the ground may depend on the quantity and quality of the food. The pheromone trails will lead other ants towards the food source. The path which has the strongest pheromone concentration is followed by the ant which is the shortest paths between their nest and food source. This paper surveys the ACO based routing in various Networking domains like Wireless Sensor Networks and Mobile Ad Hoc Networks.
An efficient ant optimized multipath routing in wireless sensor networkEditor Jacotech
Today, the Wireless Sensor Network is increasingly gaining popularity and importance. It is the more interesting and stimulating area of research. Now, the WSN is applied in object tracking and environmental monitoring applications. This paper presents the self-optimized model of multipath routing algorithm for WSN which considers definite parameters like delay, throughput level and loss and generates the outcomes that maximizes data throughput rate and minimizes delay and loss. This algorithm is based on ANT optimization technique that will bring out an optimal and organized route for WSN and is also to avoid congestion in WSN, the algorithm incorporate multipath capability..
A mobile monitoring and alert sms system with remote configuration – a case s...Editor Jacotech
One of the parent´s main concerns nowadays it to know their children´s whereabouts. Some applications exist to address this issue and most of them rely on internet connection which makes the solution expensive. In this paper we present a low cost solution, based on SMS, and with the ability to remotely configure the child monitoring process. We also present the architecture and the full flowchart of the child application whenever a SMS is received. This case study uses Android and the more recent location API – the Fused Location Provider. For obvious reasons, the security issue has been a concern, which resulted in a configuration module in the child application to specify authorized senders
Leader Election Approach: A Comparison and SurveyEditor Jacotech
In distributed system, the coordinator is needed to manage the use of the resources in the shared environment. Many algorithms have been proposed for the same. They have various positive and negative parts. Here we will discuss those issues which ensure the efficiency of the algorithm for election leader. Here a comparison will be provided to show the advantages and disadvantages of different election algorithms. The comparison would be based on the number of messages passing and the order of time complexity.
Leader election approach a comparison and surveyEditor Jacotech
In distributed system, the coordinator is needed to manage the use of the resources in the shared environment. Many algorithms have been proposed for the same. They have various positive and negative parts. Here we will discuss those issues which ensure the efficiency of the algorithm for election leader. Here a comparison will be provided to show the advantages and disadvantages of different election algorithms. The comparison would be based on the number of messages passing and the order of time complexity
Modeling of solar array and analyze the current transientEditor Jacotech
Spacecraft bus voltage is regulated by power
conditioning unit using switching shunt voltage regulator having
solar array cells as the primary source of power. This source
switches between the bus loads and the shunt switch for fine
control of spacecraft bus voltage. The effect of solar array cell
capacitance [5][6] along with inductance and resistance of the
interface wires between solar cells and power conditioning
unit[1], generates damped sinusoidal currents superimposed on
the short circuit current of solar cell when shunted through
switch. The peak current stress on the shunt switch is to be
considered in the selection of shunt switch in power conditioning
unit. The analysis of current transients of shunt switch in PCU
considering actual spacecraft interface wire length by
illumination of solar panel (combination of series and parallel
solar cells) is difficult with hardware simulation. Software
simulation by modeling solar cell is carried out for a single string
(one parallel) in Pspice [6]. Since in spacecrafts number of
parallels and interface cable length are variable parameters the
analysis of current transients of shunt switch is carried out by
modeling solar array with the help of solar cell model[6] for the
actual spacecraft condition.
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Modeling of solar array and analyze the current transient response of shunt switch voltage regulator in spacecraft power conditioning unit
1. Journal of Advanced Computing and Communication Technologies (ISSN: 2347 - 2804)
Volume No.3 Issue No. 2, April 2015
33
Abstract— Spacecraft bus voltage is regulated by power
conditioning unit using switching shunt voltage regulator having
solar array cells as the primary source of power. This source
switches between the bus loads and the shunt switch for fine
control of spacecraft bus voltage. The effect of solar array cell
capacitance [5][6] along with inductance and resistance of the
interface wires between solar cells and power conditioning
unit[1], generates damped sinusoidal currents superimposed on
the short circuit current of solar cell when shunted through
switch. The peak current stress on the shunt switch is to be
considered in the selection of shunt switch in power conditioning
unit. The analysis of current transients of shunt switch in PCU
considering actual spacecraft interface wire length by
illumination of solar panel (combination of series and parallel
solar cells) is difficult with hardware simulation. Software
simulation by modeling solar cell is carried out for a single string
(one parallel) in Pspice [6]. Since in spacecrafts number of
parallels and interface cable length are variable parameters the
analysis of current transients of shunt switch is carried out by
modeling solar array with the help of solar cell model[6] for the
actual spacecraft condition.
Index Terms— Shunt regulator, Shunt switch, Current transients,
power conditioning unit
I. INTRODUCTION
In space application, solar energy is the main sources of power apart
from nuclear alternatives used for inter planetary missions. With
increase in power demand the solar array size is increased with more
number of series and parallel cells. In spacecraft bus voltage
regulation, several strings of different ratings and shunt switch
combination as shown in the input of Fig-1 are paralleled to meet the
required load power. At any point of time only one string is switching
and others are either ON or OFF depending on the load power
requirement in sequential shunt switching regulator [1]. The solar cell
capacitance and resistance along with the interface cable line
inductance, plays major role in causing current stress on the shunt
switch. This current transient study is important in the selection of
shunt switch. The effect of solar cell capacitacne and cable
inductance on the performance of power conditioning unit should be
considered in the design. The effect of solar array cell capacitance
has been considered in [ 2]–[4] for the design of shunt power
regulators. The stress on the shunt switch due to cell capacitance and
cable inductance effect has not been addressed. The solar array
strings and shunt interface is through cables of different length for
each circuits. Considering the wiring on the panel, the current
transients are not same for all circuits.
Hardware simulation for all combinations (various string rating
and cable length) wired in the spacecraft is a complex approach. This
is achieved with software simulation through solar cell modeling by
deriving internal cell capacitance and resistance. The equivalent
Fig 1. Schematic of shunt switch regulator
circuit of solar cell is as shown in Fig-2. Measurement of solar cell
capacitance[5] based on the extra output voltage ripple due to cell
capacitance is not an accurate method since cable line inductance has
not been considered in the rise time of shunt switch. The first step for
cell capacitance derivation is the hardware simulation with a single
string and known cable length in the switching path. Many
parameters are available in the current transients of shunt switch to
create a cell model for software simulation, when compared with the
output voltage extra ripple due to rise time of shunt switch.
Fig 2. Solar cell equivalent circuit
II. HARDWARE SIMULATION AND ANALYSIS
A solar string with a minimum generation of 0.5A at 42V (23 cells
Modeling of Solar array and Analyze the Current Transient
Response of Shunt Switch Voltage Regulator in Spacecraft
Power Conditioning Unit
By
1
Thriveni Eshappa, 2
Rajeev Ranjan, 3
Nitin D Ghatpande
1,2,3
Power System Group, ISRO SATELLITE CENTRE, Bangalore-560047
1
thriveni@isac.gov.in, 2
rranjan@isac.gov.in, 3
gpande@isac.gov.in
2. Journal of Advanced Computing and Communication Technologies (ISSN: 2347 - 2804)
Volume No.3 Issue No. 2, April 2015
34
in series) is interfaced with the shunt circuit with definite cable
length. The schematic shown in Fig 1 is for the 42V spacecraft bus
voltage. Instead of closed loop operation a fixed 42V supply is used
as bus voltage. Shunt switch is driven by function generator to
observe the current transients at different switching frequency. String
isolation diode is connected between the solar array and the load.
Solar cells are illuminated by large area pulsed solar simulator
providing sun intensity of 2ms duration. The current and voltage
transients are as shown in Fig 3 and Fig 4 for 15 KHz switching.
Fig 3. Current transient response
The current through the switch when shunted is a damped sinusoidal
with a settling time of 18 µs as shown in Fig 3. Whereas the voltage
rise across the switch when open is ringing and not a smooth
exponential as shown in Fig 4. However these dynamics are not the
actual transients present in the spacecraft since the solar string rating
and harness length are different in the setup. Modeling of solar cell is
essential to carry out software simulation incorporating solar array
circuit connected to shunt switch with required cable length
inductance. A single string is considered in the hardware setup for
derivation of cell capacitance and resistance to model solar cell.
Voltage rise
Fig 4. Voltage transient response
A method for finding solar array capacitance is discussed in [5]
considering the voltage rise across the switch where cable inductance
which also contributes for the voltage rise as shown in Fig 5 is
ignored. This method will not give exact cell capacitance value.
Hence extra ripple is due to cell capacitance as well as cable
inductance in the switching path. Current transient through shunt
switch is taken as input for modeling of solar cell since many
parameters are available compared to voltage rise in the voltage
transient response.
Fig 5. Inductance effect on Voltage rise across switch
The most efficient way of deriving solar cell capacitance, resistance
and interface cable inductance is using current transient parameters
like first peak current, second peak current and damped frequency. At
switching frequency <15 KHz the variation of current parameters are
very minimal as shown below for 10 KHz. Hence the above
mentioned values for 15Khz is considered for derivation.
Fig 6. Current response for 10Khz
III. DERIVATION OF R, L, C USING MATHEMATICAL MODEL
When the shunt switch is open, solar cell capacitor starts charging
and discharges through the switch when closed. The mathematical
model and circuit for this action, including resistance and inductance
in the path is as shown in Fig 7.
Fig 7. Circuit diagram for model
Equation for the given circuit, when switch is shunted
C
dVc
dt
+ Io* u(t) = I(t) (KCL)
sCVc(s) +
Io
s
+ CVo = I(s) (1)
Vc(t) = I(t) R + L
dI(t)
dt
(KVL)
Vc(s) = I(s) (R+Ls) (2)
From (1) and (2)
sC I(s) (R+Ls) +
Io
s
+ CVo = I(s)
I(s) =
IoWn 2
s(s2+2∗zi∗Wn ∗s+1)
+
kWn 2
(s2+2∗zi∗Wn ∗s+1)
Where, Wn =
1
LC
---- natural frequency,
3. Journal of Advanced Computing and Communication Technologies (ISSN: 2347 - 2804)
Volume No.3 Issue No. 2, April 2015
35
Wd = Wn 1 − zi2 =
1
LC
−
R
2L
2
-- damping frequency
Zi =
R
2
C
L
---- damping factor
In time domain I(t) = Io (1 -
𝑒−𝑧𝑖∗𝑊𝑛 ∗𝑡
1−𝑧𝑖2
sin [Wd* t + atan
(
1−𝑧𝑖2
𝑧𝑖
)t ] +
𝑉𝑜
𝑊𝑑𝐿
𝑒−𝑧𝑖∗𝑊𝑛∗𝑡
*sin (Wd*t) (3)
To derive R, L and C, the steady state current Io is considered as zero
for simplicity.
Equation (3) reduces to
I (t) =
𝑉𝑜
𝑊𝑑𝐿
𝑒−𝑧𝑖∗𝑊𝑛∗𝑡
*sin (Wd*t) ---- (4)
Substituting 1st
positive peak, 2nd
positive peak and damping
frequency in eq (4) for different time, the values of R, L and C
obtained are----
Total cell capacitance C= 0.032µF, Total series resistance R = 4.05Ω
and Total Inductance L= 7µh. ------ (5)
A. INDUCTANCE:
One meter wire will have an inductance of 1.1H (straight or
looped). With varying diameter of 500mil (0.49 inches) to 5mil
(0.0049 inches) the change in inductance is from 1H to 1.8H only.
In the hardware setup two wires (spacecraft cable requirement) of 8
meters length was used between cell positive and negative. Mutual
inductance for this setup is given by M=k (𝐿1𝐿2) --- (6)
Where k is the coupling coefficient with 0 ≤ k ≤ 1, L1 is the
inductance of the first wire and L2 is the inductance of the second
wire. The measured effective inductance of two parallel wires of 1 mt
length when closely placed is 0.9µh. Where Leff =
(L1*L2/(L1+L2))*(1+ k) --- (7). Hence k= 0.636. For 8 mts cable
length effective L is given by 4.4*(1+0.636) = 7.19H which is
closely matching with the value in (5).
B. RESISTANCE:
The total series resistance includes, cell internal impedance, wire
resistance and shunt switch ON resistance. The split up of total
resistance is as given below
The On resistance of 2N7391 is 0.2 Ω.
Wire resistance: Any wire carrying alternating current will have
higher resistance than wires carrying dc current due to skin effect
which is given by
10−6 𝑓
𝐷
in Ω/ft. Where D = diameter of wire in
inch, f= frequency of alternating current in hertz. Since transient
response is alternating current, the AC resistance for 22 gauge wire
with D=0.025 inch and f= 333 KHz (frequency is taken from the
practical result from fig3) is Rac= 0.0231 Ω/ft or 0.0757 Ω/mt. For 8
meters length Rac=0.606Ω. Hence for 2 wires effective AC resistance
Rac> 0.3 Ω and ≤ 0.6 Ω because of proximity effect for closely
running wires. Here maximum of 0.6 Ω is considered which
introduces very small percentage variation in the cell resistance
calculations. Hence for 8mtr wire Rac=0.606Ω. Whereas the DC
resistance of the wires (22 gauge) for 1mt length= 50m Ω. And for
8mts parallel wire Rdc= 0.2Ω.
Cell internal resistance: The internal resistance for 23 cells in
series= (4.05 - 0.606-0.2) = 3.244 Ω. Hence the cell internal
impedance= 141mΩ.
C. CELL CAPACITANCE:
The capacitance of each cell is derived from total capacitance. Hence
individual cell capacitance is given by (0 .032*23) = 0.736F.
This value closely matches with the cell data.
IV. CELL MODEL
From the value derived above, cell model is created as shown in
Fig 8. The four diodes in parallel with the current source gives the
open circuit voltage of 2.64 which is equal to actual open circuit
voltage of onboard cells for 42V application. Manufacturer’s data
sheet describes the internal impedance of the cell to vary from 0.1 to
Fig 8. Solar cell model
0.5 Ω. And the cell impedance will tend towards the lower side of
this range. Accordingly impedance of 141mΩ to 153mΩ (considering
the small percentage error due to proximity effect) is obtained in the
calculation.
V. CELL VALIDATION
The solar cell model is validated by connecting 23 equivalent circuits
in series to get one parallel of 0.52A @ 42V and interface with the
shunt switch circuit as shown in Fig 10. When the switch is closed
the current dynamics through it as shown in Fig 9 is same as the
result obtained from the hardware experiment shown in Fig 3.
Fig 9. Simulation Result
Initial Current Io= 0.52A
+ ve Peak current = 2.838A
-ve Peak current= -878mA
Period= 3.04s
tr = 750ns,
Settling time = 20s
4. Journal of Advanced Computing and Communication Technologies (ISSN: 2347 - 2804)
Volume No.3 Issue No. 2, April 2015
36
Since all parameters are matching with respect to hardware results,
the cell model created is validated. Using this cell model, solar string
of any rating connected to shunt regulator with any harness length
can be modeled in the software to analyze shunt switch current stress.
In any spacecraft each string is combination of series and parallel
cells to achieve required string current at required voltage.
Fig 10. Circuit model
VI. ANALYSIS
When the switch is shunted, capacitor is fully charged. Current flow
through the switch is due to generation current of the cell and the
capacitor discharge current. This closed circuit becomes second order
under damped system with damping factor zeta (ξ) <1 given by
R/2 (C/L) . The response of under damped system is always
oscillatory with frequency of damped oscillation Wd= Wn*sqrt (1-ξ2
),
Wn=Natural frequency= 1/ (L C) . The peak current is given by e-
πξ/sqrt (1-ξ^2)
. The contribution of capacitor voltage for peak current is
higher than the solar cell current. The damping occurs due to the
presence of resistance in the switching path where the energy gets
dissipated. Hence the amplitude of current peaks damps
exponentially and settles at 4 * T, (T=
1
Wn ∗ ξ
).
A bypass diode is connected across each cell on the panel to bypass
the cell failed in open mode. The negative peak is limited at 880mA
due to the conduction of this bypass diode when reverse voltage is
greater than total cut in voltage for 23 diodes.
VII. EFFECT OF SERIES DIODE
For higher string rating, single parallel (minimum current) strings are
diode ORed to achieve total string current thereby preventing one
string failure under short circuit of any single parallel. The current
transient through switch with the series diode is as shown below.
Series diode
Fig.11
Hardware Simulation:
CH4= Switch Current, CH2= Drain Voltage
Fig.12
Software Simulation:
Fig.13
As observed in fig12/fig13, there is a ringing current of small
magnitude when the resonating negative current flows through the
diode in the switching path. Since diode blocks this negative current
the reverse voltage across the diode increases for a small duration.
The reverse voltage stress on the series diode for one parallel as
observed in the simulation is shown in fig12.
The reverse voltage across the series diode is 157V as seen above.
The reverse breakdown voltage of 1N5811 used is 160V. This series
diode is blocking negative 880mA (fig9) which causes current
ringing during the entire negative cycle of resonant current. At
negative peak of 200mA ringing current, maximum reverse voltage is
observed across the diode. This peak reverse voltage reduces with
decrease in the ringing current magnitude and becomes zero at the
end of the cycle. Lower the string rating higher is the voltage stress
on the device.
5. Journal of Advanced Computing and Communication Technologies (ISSN: 2347 - 2804)
Volume No.3 Issue No. 2, April 2015
37
Fig.14
VIII. SOLAR ARRAY MODEL
The shunt switch in the spacecraft is switching to regulate the bus
voltage. The string current used onboard is a variable component.
The effect of solar cell capacitance and cable inductance for
maximum and minimum string rating is simulated and analyzed by
creating solar array model. Here minimum of 1A and maximum of
3.6A (2Parallels to 7parallels) is considered.
Solar Array model is generated using solar cell model and measured
cable length from panel to the shunt switch including wiring done on
the spacecraft solar panel. 23 cell models are connected in series to
get one parallel generating 0.52A @ 42V Vmp. The number of
parallels connected depends upon the rating of the switching string to
be connected to the shunt switch. Hence the extreme condition of
minimum and maximum strings solar array model is generated to
study the current response.
A. Maximum string current
The maximum switching current through the shunt switch
considered is 3.6A.
1. Solar String Model
Maximum string is simulated by connecting seven parallels each
0.52A @42V having 23 solar cell models in series. Each parallel
on the panel is running through a series diode to form one string.
2. Estimation of interface cable length
The length of the cable from solar string to the shunt switch includes
Wiring on the panel from cell positive through diode to the
panel connector
From panel connector to SADA connector
From SADA connector to the shunt switch in PCU
Measured cable length is as given below
Panel wiring
Each parallel to the diode anode = 1mt
Diode cathode to panel connector maximum = 3.25mts
String return to Panel connector = 1.65mts
Panel connector to SADA connector = 3mts
SADA to shunt switch in PCU = 3mts
Shunt switch return from the PCU to panel connector =6mts
The total harness length from solar cell live to return is 16.9mts.
Hence L can vary from 16.9H to 8.45H since two wires are
running from series diode cathode to shunt switch drain.
The array model, circuit connection and simulation results are as
shown below.
Fig.15
S1in to S7in » 23 Solar cell equivalent circuit
Bypassdiode1 to bypassdiode7 » 39diodes connected across each
parallel
L17 to L23 »inductance of single wire from each cell positive to
series diode
L40» Inductance from series diode cathode to panel connector
L41» Inductance from panel connector to shunt switch
1) Current transient through shunt switch for L=16.9µH
(with maximum coupling between wires)
Fig.16
+ve Peak = 8A through the switch
-ve peak = 1A above the ground level
Period= 12.14µs, frequency= 82Khz
Settling time= 137µs
For 7 parallels the effective capacitance increases when compared
with single parallel (0.032µ*7). The actual spacecraft harness length
is more than the set up harness length (16.9mts>8mts) which
increases the inductance value. The damping factor reduces since L
is inversely proportional and C is directly proportional to damping
factor. This low value of damping increases the settling time. The
frequency has reduced because of low value of damping factor. The
peak current is not very high since it is dependent on damping factor
200mA
157V
6. Journal of Advanced Computing and Communication Technologies (ISSN: 2347 - 2804)
Volume No.3 Issue No. 2, April 2015
38
as mentioned in page 3 analysis. Also the peak current is mainly due
to capacitor initial voltage which is still at 42V. A DC shift of 3.6A is
present instead of 0.5A (one parallel).
2) Current transient through shunt switch for L/2= 8.59µH
(with no coupling between wires)
Fig.17
+ve Peak of 9.4A flows through the switch
Small current ringing at –ve peak at ground level
Period= 8.71µs, frequency= 114Khz
Settling time= 77µs
For lower value of inductance, peak currents (both +ve and –ve)
increases while settling time decreases. The maximum reverse
voltage across series diode during the blockage of negative swing
current is 17V for <1µs as shown below
Fig.18
The AC resistance of the harness depends directly on the frequency
of damping current and the harness length as described in page 3.
Since length of the harness has increased and frequency is reduced as
shown in the result below, the effective change in the Rac value is
negligible. Hence Rac=0.606Ω is considered.
B. Minimum string current
Simulation is carried out with 2 parallels connected for the same
harness length.
1) Current transient through shunt switch for L=16.9µH
(with maximum coupling between wires)
Fig.19
The negative peak is blocked at zero level
+ve Peak = 3.3A through the switch
Small current ringing at –ve peak at ground level
Period= 6.72µs, frequency= 149 KHz
Settling time= 70µs
Reverse voltage across series diode is 70V for 1µs
2) Current transient through shunt switch for L/2= 8.59µH
(with no coupling between wires)
The negative peak is blocked at zero level
+ve Peak = 3.83A = through the switch
Small current ringing at –ve peak at ground level
Period= 4.75µs, frequency= 211 KHz
Settling time= 34µs
Reverse voltage across series diode is 115V for 1µs
Higher the amplitude of negative current to be blocked by the diode
more is the reverse voltage across it.
IX. Conclusion
The solar cell capacitance and line inductance induces damped
oscillating current through the shunt regulator when the shunt switch
is closed. This peak current stress on the regulator must be considered
during the selection of the shunt switch. Higher the string rating and
harness length the effective capacitance and inductance increases
which reduce the damping factor zeta thereby increasing the settling
time. Hence during switching, the switch may open before the
settling time of damping current. High peak currents are mainly due
to capacitor initial voltage rather than short circuit current from solar
array. A DC shift of short circuit (Isc) current is present in the
dynamics. For higher string rating, each parallel (minimum current)
is diode ORed to achieve total string current. This series diode is
stressed for a short duration during blocking of negative peak current
of the transients. The reverse voltage stress also has to be considered
in the selection of series diode.
REFERENCES
[1] D.O'Sullivan, A. H. Weinberg "The Sequential Switching Shunt Regulator
(S3R)", in Record, ESTEC Spacecraft Power Conditioning Seminar,
1977, ESA SP-126, pp. 123-131.
[2] A.R.Patil,B.H.Cho anf F.C.Lee, “Design consideration for a solar array
switching unit,” in Proc. IECEC’90 Conf.,1990, pp. 373-379.
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Thriveni Eshappa received B.E degree in
electronics and communication from National
institute of Engineering, Mysore University, Mysore,
India in 1997. She was Lecturer in R.V. college of
Engineering, Bangalore from 1998 to 1999. She has
been with ISRO satellite Centre since 1999 in Power
System Group. She is involved in the design and
realization of satellite power systems. Her areas of
interest are solar cell capacitance, spacecraft bus
voltage regulators, Test simulators for spacecraft power system.
Rajeev Ranjan received B.Tech degree in Avionics
from Indian Institute of space science and
technology, Trivandrum, India in 2011. He has been
with ISRO Satellite Centre, Bangalore since 2011.
He is involved in the design of Dc-Dc Converter,
LDOs and satellite power systems. He has published
one conference paper related to artificial intelligence
in international conference. His areas of interest are
solar cell capacitance, S3R, Dc-Dc converters
Design, Magnetics and artificial intelligence.
Nitin D Ghatpande received his B.Tech in Electronics
in 1976 and M.E. in Electrical Engineering in 1990
from Indian Institute of Science. He is
Scientist/Engineer with ISRO since 1977 and worked
in many area related to spacecraft application like
Core Power of spacecraft, EMI/EMC compatibility of
spacecraft, development & analysis of power
conditioning and processing unit. He is currently
Group Director, Power System Group at ISRO
satellite centre. His work area includes development & miniaturization of
power processing unit for onboard usage in spacecraft.