S. Sreejakumar
M.Tech Project :
DSP based, high power factor, high frequency link AC-DC converter
Department of Electrical Engineering
Indian Institute of Technology Bombay, Powai, Mumbai 400 076.
Supervisor(s): Vivek Agarwal
The main objective of this work is to apply DSP as a controller in high-frequency link, high power factor AC-DC converter. The high-frequency link is a resonant converter and the power factor corrector is a boost power factor correction stage. The DSP acts an independent controller, controlling the boost power factor corrector and resonant link converter. TMS320C5402 was the DSP used and a high-speed ADC was used for data acquisiton.
Suresh Suralkar
M.Tech Project :
Design and development of a reliable AC drive.
Department of Electrical Engineering
Indian Institute of Technology Bombay, Powai, Mumbai 400 076.
Supervisor(s): Vivek Agarwal
As the technology is evolving in the areas of power electronics, the various new power-switching devices are being introduced and their capacities enhanced. New methods for speed control of motors are emerging. Correspondingly the variable frequency AC drive (VFD) has become more complex and reliability issues are surfacing. If the reliability is improved, the cost of the drive goes up. Nevertheless there is a great urge from industry for highly reliable and economical VFD. Our aim in this project is to find out more reliable method, calculate reliability and suggest the reliability improvements. As a first step, various problems associated with the drives are listed. One of the methods for speed control is selected for the prototype. The prototype is made and the reliability is calculated. Suggestions are given for reliability improvements. For reliability calculation, the method stipulated in Military Handbook MIL-HDBK-217F is chosen. This method is developed by United States Military Department and is being used worldwide for reliability calculations of electronic circuits.
S. Santhosh
M.Tech Project :
Design and fabrication of 1kVA uninterruptible power supply system
Department of Electrical Engineering
Indian Institute of Technology Bombay, Powai, Mumbai 400 076.
Supervisor(s): Vivek Agarwal
Some equipment like computers, process control systems, communication links, hospital equipments, etc need better quality of power supply for their better operation, because they are very sensitive to the nature of the supply. Also the wave shape of the power supply is important.So to meet the requirements of the critical equipments, the quality of their power supply must meet certain specifications. A UPS has emerged as the single most important equipment for the industrial and business growth for satisfactory operation of the critical equipment. A typical UPS protects systems against power defects like surges and sags which are caused by rapid fluctuation in the amplitude of the alternating current and insures them against low voltage and no power conditions. There are different types of UPS systems available in the literature among these the most commonly used configuration is on-line UPS system. This report presents an on-line UPS system for critical equipment. The proposed topology is based on a high-frequency transformer link between the standby battery and the low frequency inverter. Achieving power output from the high-frequency link push-pull converter during back-up mode provides a simple, efficient and galvanically isolated topology for use in critical load. During the normal mode (when AC mains is available) of operation the inverter draws power from the AC mains through a high-frequency DC to DC boost converter at the same time the standby batteries are charged by the battery charger. In this topology is based on a high-frequency transformer link between the standby battery and the low frequency inverter. Achieving power output from the high-frequency link push-pull converter during back-up mode provides a simple, efficient and galvanically isolated topology for use in critical load. During the normal mode (when AC mains is available) of operation the inverter draws power from the AC mains through a high-frequency DC to DC boost converter at the same time the standby batteries are charged by the battery charger. In this topology, the single phase low frequency inverter uses SPWM technique and the rectifier used is the low frequency full-bridge type. The design details of 1 kVA on-line UPS system is included in this report. A prototype has been fabricated for the proposed topology. Experimental results from the prototype under operating conditions are also presented in this report.
Nitesh Singh
M.Tech Project :
Design and Fabrication of Remote Controlled AC Drives
Department of Electrical Engineering
Indian Institute of Technology Bombay, Powai, Mumbai 400 076.
Supervisor(s): Vivek Agarwal
For more than a decade, significant progress has been made in the development of variable speed ac drives. Advancement in power converters has made it possible to obtain high performance drives. In parallel with the advances in the technology, there has been major advances in digital eletronics including the advent of the microprocessors. Taking the advantage of microprocessor we can use a remote control for the speed control. In this thesis the rectifier, inverter, buffer circuit are used and the microprocessor has been used for the generation of the PWM. The Philips remote control was used whose protocol was shift coded. However we can use any of the remote control, it will require the change in the software.
Pradeep Anand
M.Tech Project :
Development of an efficient electric drive for robotics application
Department of Electrical Engineering
Indian Institute of Technology Bombay, Powai, Mumbai 400 076.
Supervisor(s): Vivek Agarwal
One of the basic assumptions in the synthesis and analysis of a four bar mechanism is that angular velocity of the input link is constant. However this assumption may not be valid when an electric motor is connected to drive the mechanism. In this report, the motor mechanism combination is treated as a single system. The objective is to control the angular speed so that crank angular speed fluctuation of a four bar linkage is reduced. A dynamic model of a four bar mechanism coupled to a printed armature motor is present. The dynamic equations are solved using C- language based software. Plots of angular speed of the input link of the four bar mechanism against armature voltage and/ or current help in understanding the nature of interaction between the motor and the mechanism. These plots are included. The control scheme to reduce the speed fluctuations of a four bar mechanism is explained. The control algorithm has been practically realized using Atmel's 89C55 microcontroller. A four quadrant MOSFET based chopper has been designed and fabricated in the laboratory to test the theoretical results. The duty cycle of the MOSFET is predetermined using the theory and stored in the microcontroller in a look up table. The validity of the propsed model and analysis is confirmed by the experimental results. Possibility of regenerating power has also been studied to make the drive more efficient.
Prashant Gugle
M.Tech Project :
DSP based power factor correction by active shaping of input current
Department of Electrical Engineering
Indian Institute of Technology Bombay, Powai, Mumbai 400 076.
Supervisor(s): Vivek Agarwal
In most of the Power Electronics processing the first stage is an AC to DC converter. In conventional AC to DC converter in order to obtain ripple free DC voltage a large capacitor is placed at the output of the diode bridge rectifier. But due to this the source current waveform is peaky. There is large harmonic distortion in the current. In order to get better total harmonic distortion in the current and unity power factor a boost converter is placed at the output of diode bridge rectifier. The inductor current is controlled in such a way that it follows the sinusoidal waveshape with hysteresis. Hysteresis band width ,decides switching frequency of the boost switch and total harmonic distortion in the current . Smaller the bandwith larger the switching frequency and better the thd and larger the switching losses. So in order to reduce the switching losses band width is increased till we get the desired maximum acceptable total harmonic distortion in the current and optimised switching losses.
Mini Rajeev
M.Tech Project :
Design and implementation of a single stage single switch power factor correction technique for switched mode power supplies.
Department of Electrical Engineering
Indian Institute of Technology Bombay, Powai, Mumbai 400 076.
Supervisor(s): Vivek Agarwal
A single stage single switch power factor correction technique which combines the boost stage with a continuous conduction mode dc/dc output stage is described. Due to the ability to keep a relatively low voltage (less than 450V dc) on the energy storage capacitor, this technique is suitable for universal line voltage applications. The voltage on the energy storage capacitor is kept within the desirable range by tapping the primary winding. The principle of operation of the circuit with fly back dc/dc converter is presented. Results obtained from simulation and experimental work are included. A modification has also been proposed with a view to reducing the EMI.
B. Krishna
M.Tech Project :
DSP based control of energy efficient incremental motion DC drive
Department of Electrical Engineering
Indian Institute of Technology Bombay, Powai, Mumbai 400 076.
Supervisor(s): Vivek Agarwal
In order to achieve better efficiency in applications such as limited supply drives, like those employed in submarines and autonomous robots, a separate control strategy is required for speed control. In this work, a control algorithm has been chosen, which generates the reference speed profile for the drive in order to minimize the losses. Hardware implementation details (including interfacing using TLV1562 to DSP '5x and design of power stage) have been presented. Also included are the simulation results of the proposed strategy applied to an incremental motion DC drive.
R.Vishwanath
M.Tech Project :
Gamma Radiation Effects on Operational Amplifier Integrated Circuits
Department of Electrical Engineering
Indian Institute of Technology Bombay, Powai, Mumbai 400 076.
Supervisor(s): Vivek Agarwal
Linear Integrated Circuits (ICs) or Operational Amplifiers (Op-Amps) are extensively used in many of the electronic applications of today. Since applications and measurements have become more sophisticated in today's world, presision Op-Amps have become essential. They are used in critical applications such as space avionics, ion-chamber amplifiers, bio-medicine etc. However, each of the above applications may work under diffferent conditions of temperature, humidity and radiation. This thesis presents a study exclusively devoted to precision and non-precision Op-Amps with respect to their gamma radiation performance. The Op-Amps chosen for comparison have different makes and input stages, such as MOS and FET structures. The main endeavour of this thesis has been to study and establish the degradation of their vital characteristics such as bias currents and offset voltages with respect to the total dose of gamma radiation to which they are exposed, with all such experimentation done 'on-line'. As an extension of the research, extensive simulation runs have also been performed on typical instrumentation systems which have these Op-Amps as their mainstay. This feature is very helpful to extrapolate the radiation effects without actually rigging up the entire circuit. All simulation and experimental results are presented. It is hoped that this research would be useful in aiding thought in the direction of setting up a benchmark for radiation testing, especially for electronic devices like Op-Amps used in critical applications as mentioned above.
Hiren Patel
M.Tech Project :
Microcontroller based intelligent battery charger system operating at unity power factor.
Department of Electrical Engineering
Indian Institute of Technology Bombay, Powai, Mumbai 400 076.
Supervisor(s): Vivek Agarwal
A novel scheme for battery charger system is presented. It is based on a smart battery monitoring chip (Dallas Semiconductor's DS2438) to monitor the battery parameters like current, voltage and temperature. The system works under the control of an intelligent controller (Intel's 8051), which communicates with DS2438 and estimates the state of charge of the battery and accordingly controls the battery charger circuit to give appropriate charging profile. The advantage with this kind of system is that it can be easily extended to manage a pack of several batteries. The battery charger circuit is based on a two-switch cascaded buck-boost topology and is controlled by hysteresis current control to give a unity power factor operation at the ac source. To ensure fast charging, the microcontroller controls the charger's operation to give constant current-constant voltage method. The control scheme involves a simple mechanism of adjusting the charging current and hence provides flexibility to use the same hardware with the battery of several different ratings. The presence of an intelligent controller facilitates various features like adjustment of charging voltage for variation in temperature, continuous tracking of SOC, adjustment of appropriate charge profile, flexibility to charge batteries of different ratings etc.
Sandeep Dhadich
M.Tech Project :
Design and Implementation of a DSP based Single Stage Grid connected PV system.
Department of Electrical Engineering
Indian Institute of Technology Bombay, Powai, Mumbai 400 076.
Supervisor(s): Vivek Agarwal
Photo voltaic systems have emerged as key player in the field of non conventional energy. They become more efficient as well as economic with grid connection, in comparison to stand-alone system. A single-phase grid connected photovoltaic system has been designed which employs single stage (dc-ac) power conversion. Conventional grid connected PV systems use, two stage systems ? a dc-dc stage for boosting of the solar PV voltage followed by an inverter stage. Proposed scheme has higher efficiency and lower cost. A DSP based controller, ADMCF 341 is used to implement maximum power point tracking (MPPT) controller. The advantages of DSP implementation are higher controllability and reliability. Hysteresis current control is used for the control of inverter. Keywords: Voltage source inverter (VSI), Photovoltaic (PV) system, Maximum power point tracking (MPPT), Grid connection, Single stage conversion.
N.Reddy
M.Tech Project :
A Hybrid Distributed Power Generation System Based On Solar And Fuel Cells With Compensation Feature
Department of Electrical Engineering
Indian Institute of Technology Bombay, Powai, Mumbai 400 076.
Supervisor(s): Vivek Agarwal
The demand for energy is rapidly increasing with increasing population and industrialization. Conventional energy sources mostly consist of fossil fuels which cause severe damage to the environment. The above two factors have motivated the modern world towards extensive research into non-conventional energy sources and their usage. Photovoltaics and fuel cells are among the popular sources out of all non-conventional energy sources. This report presents the details of design and development of a compensator plus local power source which can feed power from a hybrid source of photovoltaic cells and fuel cells. Apart from feeding active power to the load, the system is capable of feeding reactive power too. In the proposed scheme, both fuel cells and PV cells feed power to a common DC bus. An inverter connected to this DC bus converts DC power into AC power. As long as solar insolation is available, the PV panels supply the required load current and any excess power generated is fed into the grid. When the solar insolation is not available, fuel cells supply the required active power. Unlike solar cells, the power generated by the fuel cells can be controlled. Thus, the combined operation of these two sources can supply reliable power to the load.
N.C.S. Ramachandran
M.Tech Project :
Design and Development of Web Server Based Spirometer
Department of Electrical Engineering
Indian Institute of Technology Bombay, Powai, Mumbai 400 076.
Supervisor(s): Vivek Agarwal
Spirometers are used to measure and estimate lung capacity. Spirometric measurements are important for effective treatment. Unfortunately, the usefulness of spirometry has not been utilised fully due to the high cost of the instrument involved. This report presents the details of the development of a low cost, portable spirometer with a web server embedded in it. The experimental prototype includes an MEMS based pressure sensor to detect the airflow by measuring its pressure, a keyboard for data input, an LCD for data display, a microcontroller for controlling and co-ordinating all the operations, an Ethernet and a serial port for communication with other devices. Eltrax 100LX development board from Axis communications is used for the web server application. All the software and hardware details of this instrument are presented. Its cost is estimated to be approximately 80 USD, which is expected to be even lower if a large number of such units are produced.
Sandeep Satav
M.Tech Project :
Design and development of microcontroller based EMI measurement system for EMC pre-compliance
Department of Electrical Engineering
Indian Institute of Technology Bombay, Powai, Mumbai 400 076.
Supervisor(s): Vivek Agarwal
Electromagnetic Interference is a growing problem and a matter of concern for electrical and electronic product designers, manufacturers and consumers. Practices of Electromagnetic Compatibility like shielding, filtering, grounding, bonding and 'EMC by Design' keep the EMI at its lowest and confirm electromagnetic cohesiveness in the environment. Formal and final EMC compliance tests are expensive and can not be performed frequently during product development cycle. Concept of low cost, relatively less accurate but reproducible in-house, pre-compliance testing is popular among product designers for many years. This work describes an economical, reproducible measurement system for EMI measurement to test EMC pre-compliance of the product. It comprises of a set of 4 probes to measure radiated E-field and H-field in various frequency bands which covers most of the formal EMC standards requirements. It also consists of a current probe with peak detector to measure conducted emission in the frequency band recommended by CISPR. An inexpensive microcontroller based EMI data measurement and display system measures and processes outputs of the probe and display them in appropriate units. To present EMI data in several graphical forms like bar charts, time-stamped plots etc., the measurement system can transfer the data to a computer over a serial bus. A custom made GUI based application software can store, format and display the collected data as per the users requirements. To facilitate calibration of the probes and to perform several pre-compliance tests, Helmholtz coils and TEM cell have been designed and fabricated. They constitute an important part of the presented EMI measurement system. The measurement system is a portable instrument, with data logging facility, which makes it suitable for electromagnetic survey of the fields/sites.
Vineet Aras
M.Tech Project :
Design of electronic control unit(ECU) for automobiles - electronic engine management system(EMS), hardware with on-board diagnostics(OBD)
Department of Electrical Engineering
Indian Institute of Technology Bombay, Powai, Mumbai 400 076.
Supervisor(s): Vivek Agarwal
The main goal of this project is the Design of Electronic control Unit (ECU) for Engine Management with On-Board Diagnostics (OBD). We have designed, implemented and tested this system in the lab. This report illustrates a number of innovations we have come up with in the design of the interfaces of the controller with sensors and actuators. With respect to the regulations demanding lower emissions, together with the need for better performance, fuel economy, continuous diagnosis, electronic systems form an inevitable part of Engine management. An electronic systems design approach has been used to break down the whole electronic engine management hardware into various modules. The various modules use technologies such as smart programmable sensors and actuators that increase accuracy and reduce system size, ASICs that improve efficiency, controller that can execute complex processing algorithms and a fault diagnostics OBD circuit that detect and indicate faults in system. Some new designs for sensing, actuting and OBD are developed and explained, in an attempt to provide advantages over the existing technology. These designs are particularly for engine position and speed sensing developed using Triaxis hall sensing technology, Electronic Ignition and Distribution, and Regulator fault detection and indication. Each of these sections of engine management is explained thoroughly. In each module the drawbacks in the current technology being used are listed, followed by improved technology that would possibly provide effective solutions to the problems. The advantages of the new technologies are the factors taken into consideration for selecting the components or Integrated Circuits that would assist in building up an efficient Electronic Engine Management System with OBD as a whole. The whole design is implemented, smart ICs programmed and tested with evaluations and results. Towards the end of the report, the complete actual implemented Electronic circuit diagram and the Input/Output circuit diagram of the Engine Management System with OBD is shown.
A.N.V. Uday Kiran
M.Tech Project :
New single stage single switch AC/DC converter topology operating at high power factor
Department of Electrical Engineering
Indian Institute of Technology Bombay, Powai, Mumbai 400 076.
Supervisor(s): Vivek Agarwal
In this report, a new single-stage, single-switch, AC/DC converter configuration operating at high power factor is proposed. In the proposed configuration, a part of the power is directly transferred to the load without being stored in the bulk capacitor. Due to this, the efficiency of the converter is enhanced and the stresses on the devices are reduced. The salient features of the proposed configuration include a lower component count, use of single switch, simple PWM control and high power factor (greater than 0.95) with output voltage regulation. In addition to these, the voltage across the bulk capacitor is low right from the rated load conditions to light load conditions. This feature renders the proposed converter suitable to work with universal voltage. The converter is capable of operating in both DCM and CCM, the latter resulting in reduced current stresses. All the operating modes of this converter are studied and analyzed. A design procedure is presented and expressions for device stresses are derived. The feasibility of acheiving high power factor with both voltage and current control is investigated. All the details of anlytical, simulation and experimental work are presented.
Kapil Maheshwari
M.Tech Project :
Design and development of flexible solar cell based photovoltaic system with maximum power point tracking
Department of Electrical Engineering
Indian Institute of Technology Bombay, Powai, Mumbai 400 076.
Supervisor(s): Vivek Agarwal
The aim of this project is to study the properties and performance of flexible solar cells and develop a suitable Maximum Power Point Tracking (MPPT) technique for flexible solar cells in contoured layout. Flexible solar cells are likely to be the preferred technology for building integrated applications in the future. MPPT techniques have been applied extensively to crystalline silicon (c-Si) based robust PV systems. In this work, amorphous silicon (a-Si) based triple-junction flexible PV systems, that have the advantage of being light-weight and the ability to be mounted on contoured surfaces, are studied. In a countered layout, the PV panels have significantly different electrical characteristics compared to c-Si PV panels. Most significantly, the power-voltage characteristics contain several local maxima and one global maximum. Because of such characteristics, conventional MPPT methods applied in case of c-Si based PV system, cannot be applied for a-Si flexible solar cells. In this report, a modified hill climbing MPPT method is presented as an extension of the conventional hill climbing algorithm. The simulation and experimental results show that the proposed modified MPPT technique can effectively track the global maximum in the presence of several local maxima. All the analytical and experimental details of this work are presented.
Milan Sheta
M.Tech Project :
Energy optimized control of incremental motion DC drives
Department of Electrical Engineering
Indian Institute of Technology Bombay, Powai, Mumbai 400 076.
Supervisor(s): Vivek Agarwal
Minimization of resistive and frictional power dissipation in a separately excited DC motor based incremental motion drive has been discussed. The drive is required to displace a given, fixed load through a definite angle in specified time, with minimum energy dissipation in the motor windings and minimum frictional losses. Accordingly, an energy optimal control strategy is proposed in which the motor is first accelerated to track a specific speed profile for a pre-determined optimal time period. Thereafter, both armature and field power supplies are disconnected and the motor decelerates and comes to a halt at the desired displacement point in the desired total displacement time. The optimal time period for the initial acceleration phase is computed so that the motor stores just enough energy to decelerate to the final position at the specified displacement time. The parameters, such as the moment of inertia and coefficient of friction, which depend on the load and other external conditions, have been obtained using system identification method. Comparison with earlier control techniques is included. The results show that the proposed energy optimal control strategy results in a drastic decrease in energy losses compared to the existing ones. All the analytical, simulation and experimental details of the work are presented.
Pundlik Ghate
M.Tech Project :
Implementation Of Advanced Control Techniques For DC-DC Converters.
Department of Electrical Engineering
Indian Institute of Technology Bombay, Powai, Mumbai 400 076.
Supervisor(s): Vivek Agarwal
Dc-dc converters pose a challenging problem from the control point of view, due to their inherent non-linearity. Common control techniques may not ensure robust behavior of the dc-dc converter. This project deals with comparative study and implementation of advanced control techniques to dc-dc converters. A buck type dc-dc converter has been considered for detailed investigation. QFT(Quantitative feedback Theory) and PI controllers are simulated and implemented using microcontroller 89c51. QFT is a simple graphical approach for designing a robust controller for given uncertainties of the plant. Compared to conventional PI controller QFT design procedure is structured and result oriented. All the analytical and experimental results of this work are presented.
Krishnanjulu Thota
An improved single stage single-switch power factor corrected AC/DC converter with higher efficiency
M.Ravi
A semi- resonant high power factor rectifier with clamped resonating tank on loan side for high output voltage applications
Shabbir Bohra
Single phase single stage grid connected PV based inverter utilizing one cycle control technique with modited MPPT
Atul Gupta
Maximum power point tracking scheme for photovoltic systems based on fixed freqency implementation of sliding mode control
Biswanath Naik
Development of an FPGA and DSP based integrated INS/GPS system using extended kalman filter
Ashwini Dixit
Design, Simulation and Fabrication of 1KV, 1KW DC Power source based on voltage fed PWM Inverter
Ashish Talwalker
FPGA based operation and performance comparison of Contemporary Single-stage Single-switch (S4)PFC Topologies
J.Suryaprabha
A comparison of Forward and Flyback S4PFC Topologies for a high power factor Lithium-ion battery charging application
Pradeep Sharma
Optimization of Energy Sources with respect to size, economy, efficiency and other parameters for a Hybrid Distributed..
Sincy George
Phd
Active Filter Based Power Factor Correction and Harmonic Elimination under Non-Sinusoidal Conditions
Department of Electrical Engineering
Indian Institute of Technology Bombay, Powai, Mumbai 400 076.
Supervisor(s): Vivek Agarwal
In recent years, there has been an increased use of power electronic systems in industry as well as among residential consumers. Such loads draw non-sinusoidal currents from the source causing non-sinusoidal voltage drops across the transmission line and transformer impedances. In addition, voltage source harmonic producing loads such as diode rectifiers with large filter capacitors inject voltage harmonics into the system. This results in non-sinusoidal voltages in the system and the voltage at the point of common coupling is no longer sinusoidal. Further, asymmetrical distribution of large, 1- Ψ loads results in voltage and current imbalance in the 3-Ψ system. Non-sinusoidal, unbalanced voltage and/or current have several adverse effects on utilities and the loads connected to it. Hence, an effective elimination of these harmonics and imbalance from the supply system is essential for the utilities and end users. Further, one must, as usual, compensate for the reactive power drawn from the source due to ever-present reactive loads. Harmonic contents in the system vary randomly and consequently the conventional solution for harmonic reduction using tuned filters is ineffective. This thesis presents a new control algorithm for a shunt active filter for compensation of harmonics, reactive power and imbalance in current under non-sinusoidal supply voltage conditions. Under non-sinusoidal supply conditions, any attempt to achieve unity power factor, results in a non-sinusoidal current, which increases the total harmonic distortion. On the other hand, attempt at getting harmonic free current may not yield unity power factor because of the harmonics present in the voltage waveform. The proposed algorithm optimizes this trade-off using the Lagrange multiplier technique and achieves the best compromise. It does not employ the normally used p-q theory and is applicable to both single phase and three phase systems. With the proposed technique, it is possible to obtain an optimized power factor satisfying the specified current THD limit. The algorithm has been modified for optimizing the power factor while restricting the voltage THD within the limit using a series active filter. This may be necessary for loads which are sensitive to the distortion in the voltage waveforms. It has been shown that apart from controlling the voltage THD, the algorithm is also capable of eliminating the imbalance in 3-Ψ voltage supply. Realizing the significant impact of individual harmonics on the life and performance of equipment and components connected to the power system, regulatory agencies have specified limits for individual harmonics in addition to the total harmonic distortion. Considering this, the algorithm has also been modified for individual harmonic control in voltage and current in addition to the total harmonic distortion. The applicability of the algorithm for series-shunt active filter is also investigated. The algorithm and its various modifications have been validated under various supply and load conditions using MATLAB-SIMULINK based computer simulations. Also, the performance of the algorithm is tested on an actual experimental prototype, in which DSP TMS320LF2407A has been used for computation and control purpose. All the analytical, simulation and experimental results are presented. The results show that the proposed algorithm is capable of meeting the requirements of IEEE 519/IEC 61000 while optimizing the power factor. Key words: Active filters, digital signal processor, harmonics, imbalance, non-sinusoidal supply, optimization, power factor, reactive power, selective harmonics, THD, IEEE 519, IEC 61000.
R.D.Kulkarni
Phd
Performance Evaluation and Improvement of Safety-Related Instruments and Equipment in Nuclear Power Plants
Department of Electrical Engineering
Indian Institute of Technology Bombay, Powai, Mumbai 400 076.
Supervisor(s): Vivek Agarwal
Safety is a very important issue in the operation of nuclear reactors. Various instruments and equipment used for monitoring the vital, performance and safety parameters must be highly reliable as they work in a nuclear environment. These instruments and equipment must meet the required qualification standards as per IEEE: 323-2003 to work satisfactorily in normal as well as in accidental situation and to maintain the safety norms guided by the regulatory authorities. The most critical equipment and instruments viz. Differential Pressure Switch (DPS), electronic Pressure Transmitter (PT), Differential Pressure Transmitter (DPT) and Ion Chamber Amplifiers (ICA) have been considered in this thesis for a detailed performance evaluation against nuclear hazards including Loss Of Coolant Accident (LOCA). The most cost effective, quality conscious and statistical method suggested by Taguchi has been used for optimizing the performance of ICA working in a nuclear environment. An ICA is used in reactor regulation and protection system, which is a safety system in nuclear reactors. The functional robustness of the optimized circuit of an ICA is reproduced under the realistic operating conditions. The thesis presents the use of many conventional methodologies for the performance improvement and subsequent qualification of these instruments and equipment. Besides, some non-conventional techniques have also been tried in a satisfactory manner for the desired qualification. These methodologies/techniques have been worked out, appropriately experimented and successfully implemented. The actual experimental validation and software simulation for some cases have been performed and found effective. A suitable lead shield and sealed chamber ?Igloo? has been recommended for encapsulation of PT, DPT and ICA to safeguard them from nuclear radiation including LOCA. The Igloo has been designed, fabricated and experimental results are presented. The ?non-conventional? method of physically separating the front end system (comprising sensor module of PT and DPT and ion chamber bin of ICA) and signal conditioning electronics module (comprising electronics PCB for PT and DPT and preamplifier circuit for ICA) has been executed for total elimination of radiation hazards in the vicinity of signal conditioning electronics module of these instruments in a nuclear reactor. The combined performance of separation of front end system and signal conditioning electronics and then encapsulation of signal conditioning electronics in an igloo was observed to be an effective way of qualifying the PT, DPT and ICA from the gamma radiation dose, which is of the order of 40 Mrads during LOCA event. The modifications implemented in the instruments and equipment, based on the adopted methodology, has substantially improved the reliability of the safety-related systems in NPP. All the details of this work are presented. The results meet the guidelines of the standards IEEE: 323-2003 and IEC: 60780-1998.
Sachin Jain
Phd
Single Stage Grid Connected Photovoltaic Systems with Maximum Power Point Tracking
Department of Electrical Engineering
Indian Institute of Technology Bombay, Powai, Mumbai 400 076.
Supervisor(s): Vivek Agarwal
Conventional (fossil) fuels are depleting fast. As a result, the non-conventional (renewable) energy sources, such as PhotoVoltaic (PV), wind and Fuel Cell (FC) are receiving a lot of attention from researchers all over the world. A major advantage of renewable sources is that, in general, they do not cause any pollution and most of them are available in abundance. PV is one of the popular renewable sources and is the focus of the work presented in this thesis. PV systems do not cause any noise pollution and incur nearly zero maintenance and running costs, which adds to its popularity. However, due to higher initial investment and limited life span, it is important to utilize the PV array as effectively as possible and extract maximum possible power. Effective utilization of the PV array, however, presents several challenges, like changing environmental conditions due continuous rotation and revolution of earth around the Sun and non-linear i-v characteristics which result in a unique maximum power point on its power-voltage curves. Appropriate Maximum Power Point Tracking (MPPT) schemes are, therefore, required to track maximum power from PV systems. A major application of PV is in grid connected systems ? as part of some distributed generation scheme or for compensation purposes. PV source is also an attractive candidate for hybrid distributed generation systems. The work reported in this thesis deals with single phase grid connected PV systems and MPPT schemes. A new, fast and accurate MPPT algorithm has been proposed. This algorithm, which works in two stages, first achieves an approximate Maximum Power Point (MPP) and then tracks the exact MPP using the conventional hill climbing method. During the first stage, the algorithm uses a large iteration step-size to quickly reach within a close proximity to the actual MPP, with the help of an intermediate variable ? defined in the thesis. The given algorithm has been analytically proven and simulated using a boost converter interface. A new single-phase, grid-connected inverter configuration operating in Discontinuous Conduction Mode (DCM) is proposed. The proposed PV configuration is a single-stage solution for grid connected PV systems. It is simple, symmetrical and requires minimum number of switching devices. It can not only boost the low PV array voltage, but also converts the solar DC power into high quality AC power for feeding into the grid, while tracking the maximum power from the PV array. Total Harmonic Distortion (THD) of the current, fed into the grid, is restricted as per the IEEE Std 519-1992. The proposed topology has several desirable features such as better utilization of the PV array, higher efficiency, low cost and compact size. The given configuration is also simulated for Continuous Conduction Mode (CCM) and critical conduction mode with the proposed MPPT scheme. The reference waveforms of the inductor current for CCM as well as critical conduction operation are also derived. A complete steady-state analysis, including the design procedure and expressions for peak device stresses, is included in the thesis. A comparative study is also carried out for various MPPT algorithms applied to single stage grid connected inverter configuration operating in DCM. The details of this work are also included. The proposed PV configuration is coupled with an FC source through a buck-boost converter, providing an integrated solution for Hybrid Distributed Generation Systems (HDGS). It is observed that the presence of FC increases the reliability of the system. In the proposed HDGS system, PV is used as the primary source of power operating at MPP with FC feeding only the deficit power requirement. The proposed inverter configuration is also used for compensating harmonic current required by the rectifier loads. The proposed configuration can feed harmonic current required by the rectifier loads at the point of common coupling and the remaining active power into the grid with PV array operating at MPP. An important drawback of the proposed buck-boost inverter configuration is that there is no direct transfer of energy from input source to the output. This result in large current stresses compared to other basic converters (buck and boost etc.). Thus, a need is felt for an inverter configuration which can perform all the three basic operations. Accordingly, a new topology, capable of buck, boost and buck-boost operations has been proposed. This configuration can operate and shuffle between buck, boost or buck-boost configurations even while the system is in operation and hence termed as ?Universal?. It can inherently exploit the advantages of any basic configuration during its operation. The key results of the work presented in the thesis, have been experimentally verified and are found to be in close agreement with theoretical and simulation results. Key words: Photovoltaic, maximum power point tracking, single?stage, hybrid distributed generation system, harmonic current compensation, universal inverter.