Indexing

Abstract: ECG is the main tool used by the physicians for identifying and for interpretation of Heart condition. The ECG should be free from noise and of good quality for the correct diagnosis. In real time situations ECG are corrupted by many types of noises. The high frequency noise is one of them. In this thesis, analysis has been carried out the use of neural network  for denoising the ECG signal. A multilayer artificial neural network (ANN) is designed. Here gradient descent method (GDM) is used for training of artificial neural network. The noisy ECG signal is given as input to the neural network. The output of neural network is compared with De-noised(original) ECG signal and value of Root Mean Square Error(RMSE) is computed. In training process the weights are updated until the value of RMSE is minimized. Several iteration has to be performed in order to find Minimum Mean Square Error(MMSE). At MMSE network weights are finalized. Subsequently, network parameters are used for Noise reduction. The comparison with other technique shows that the neural networks method is able to better preserve the signal waveform at system output with reduced noise. Our results shows better accuracy in terms of parameters root mean square error, signal to noise ratio and smoothness (RMSE,SNR and R)  as compare to GOWT[18].The database has been collected from MIT-BIH arrhythmias database.

Abstract:A single-phase, bridgeless Cuk AC/DC power factor correction (PFC) rectifier with regulated positive output voltage is proposed in this work. For low output voltage product applications, the rectifier is designed to convert high input voltage to low output voltage. This work presents bridgeless single-phase AC-DC power factor correction (PFC) rectifier based on Cuk topology. The topology does not possess input diode bridge and have only single semiconductor switches in the current owing path during each interval of the switching cycle, which resulting in less conduction losses and better thermal management. This topology is designed to work in discontinuous conduction mode (DCM). The advantages of Cuk converter are also available when bridgeless circuit topology is introduced. The operation is symmetrical in two half-line cycles of input voltage. In conventional, output voltage varies according to input voltage. A closed loop control technique is designed to regulate the output voltage in the desired level.  Performance and applicability of this converter is presented on the basis of simulation in MATLAB/SIMULINK.

Abstract: Electromagnetic microscale and mesoscale power generators with low voltage outputs are now widely used as kinetic energy harvesters. The extrinsic vibrations on the generator can excite the internal oscillations between the proof mass magnet and the electrical damper coils. These oscillations produce a periodically varying magnetic flux in coil, inducing a corresponding AC output voltage. This output can be converted to dc and can be used to supply power to electronic loads. The conventional AC-DC converters for energy harvesting system with diode rectifiers suffer considerable voltage drop resulting increase in power loss of circuitry and complexity. As a remedy various bridgeless boost converters were designed and implemented. Standard H bridge converter with 4 switch or 2 switch, dual polarity boost converters, parallel combination of boost and buck-boost converter, integrated boost and buck-boost combination bridgeless rectifier are some of these. These circuits are studied, simulated and compared. The simulation models are drawn and simulated using MATLAB R2010a.

Abstract: A traditional boost converter cannot provide high voltage gain because of the equivalent series resistance present in the circuit. Studies are going on to develop high gain boost converters without extremely high duty ratio. Coupled inductor or transformer link can be used in to get a high step up converter. Transformer links make the circuit bulkier. A dual switch step up converter is a compact solution to get high conversion ratio. High voltage gain can be obtained in a dual switch boost converter, with a low voltage and current stress on the switches. Here a method to further improve the voltage gain of a dual switch converter is presented. A dual switch step up DC/DC converter circuit with high voltage gain is explained. The converter achieves high voltage gain with a low duty cycle.  For the same conversion ratio, voltage stress across the switches is also low compared to the traditional dual switch converter. Simulation results in MATLAB/Simulink are also presented. 

Abstract: Induction heating is a promising technology which requires power electronics component. It is a heating method for electrically conductive materials using the heat generated by the eddy currents, by means of a varying magnetic field. The power converter feature a half-bridge resonant converter operating with a switching frequency between 50kHz and 120kHz to improve efficiency, accurate smooth power control while assuring the safety of power devices. Power requirement of an induction heating system can be varied during the heating process. A closed loop control is required to have a smooth control over the power. This work presents the analysis of an AC-AC resonant converter with closed loop which is based on the half-bridge series resonant inverter for induction heating. Only two diodes are used in this topology to rectify the mains voltage. The converter can be operated with zero-voltage switching during both switch-on and switch-of transitions. In conventional AC-AC resonant boost converter output power varies according to input voltage. In the designed system a closed loop is implemented in order to keep output power at desired value irrespective of supply voltage. The circuit is simulated using PSIM.

Abstract: In this paper circuit for coilgun is simulated and analyzed using SIMULINK. Behavior of the magnetic field due to the current carrying coil is analyzed. Also, the effect on the coilgun performance for different weights of projectiles is investigated. The speed profile for different positions of the projectile is observed which is a critical parameter for coilgun operation. A comparison is drawn between the simulated and experimental results.

Abstract: This paper presents an introduction to design a single-stage reluctance coilgun. An equivalent circuit for coilgun is analyzed and equation for current through the coil is derived. Main components while designing the coilgun selection like capacitor, IGBTs, projectile for coil design are discussed in detail and their effect on performance of the coilgun is studied. The circuit is designed for measuring speed of the projectile using IR based sensors.

Abstract: Multilevel inverter output voltage produce a staircase output waveform, this waveform look like a sinusoidal waveform. The multilevel output voltage having less number of harmonics compare to conventional bipolar inverter output voltage. The desired output of a multilevel inverter is synthesized by several sources of DC voltage. With an increasing   number of DC voltage sources, the converter output voltage waveform approaches nearly sinusoidal waveform while using a fundamental switching frequency scheme.
Based on the topology multilevel inverters are classified as: (i) Diode-clamped multi-level inverter (ii) Flying-capacitor multi-level inverter (iii) Cascaded H-bridge multi level inverter
While each of these converters fulfils the basic requirements of a multilevel inverter advantages, there are also some disadvantages associated with them.
(i)         A diode clamped inverter uses many clamping diodes with the increase in level in output voltage. The diode reverse voltage rating differs for each level and has to be calculated each time as the number of level increases.
(ii)        In flying capacitor inverter, the number of storage capacitors required increases with increase in levels. Balancing the charging and discharging rates of the capacitor is also a problem.
(iii)       In cascaded H-bridge inverter which requires reduced number of electronic devices as compared to other two topologies, there is a drawback of increased number of sources with increase in the output voltage.
In this paper Harmonic distortion analysis of output voltage in a cascaded H-bridge multilevel inverter at different conduction angles is presented with the help of simulink / matlab.

Abstract: The output voltage of an inverter has in general non-sinusoidal shape. The required AC output quantity – frequency and voltage – is created by a sequence of segments properly cut out from the input variable quantity, which is a DC-voltage. The required output quantities, AC voltage amplitude and frequency, are created either from rectangular pulses or by the pulse-width- modulation (PWM). Power source with a non-sinusoidal voltage applied to a electric equipment brings some undesirable effects. For example, it can cause additional losses in the windings and ferromagnetic circuits of transformers. In AC motors the additional losses are higher and operating characteristics of motors are worse. In photovoltaic power sources, the use of inverters must be carefully considered, because a wide range of harmonics can be generated. This would greatly decline the quality of produced and transmitted electric energy. Demand for high-voltage, high power converters capable of producing of producing high-quality waveform while utilizing low voltage devices and reduced switching frequency has led to the multilevel inverter development with regard to semiconductor power switch voltage limit. In this paper an overview is presented of different Multilevel inverter techniques to reduce the total harmonic distortion of output voltage in a inverter.

Abstract: Nowadays, step-down power converters such as buck scheme are widely employed in a variety of applications such as power supplies, spacecraft power systems, hybrid vehicles and power supplies in particle accelerators. This paper presents a comprehensive small-signal model for the DC-DC buck converter operated under Continuous Conduction Mode (CCM) for a magnetic load. Initially, the buck converter is modeled using state-space average model and dynamic equations, depicting the converter, are derived. The proposed model can be used to design powerful, precise and robust closed loop controller that can satisfy stability and performance conditions of the DC-DC buck regulator. This model can be used in any DC-DC converter (Buck, Boost, and Buck-Boost) by modifying the converter mathematical equations.

Abstract: In present era, power engineers need to plan the power system design in such a way that the system can sustain its Power Quality (PQ) even after facing all the above said problems. Along with that the system should also be compatible with the increasing demand of power supply. Quality of power depends on the system design, reliability and efficiency so study of PQD is important. PQD affects industrial as well as large commercial customers. Voltage sag is also referred as voltage dip. Voltage dip is the term given by IEC while the term "voltage sag" (VS) is used by North American power quality commission. VS creates disturbance in the pure sinusoidal waveform of voltage which in turn deteriorates the power quality of the system. VS occur for very short duration of 0.5 to 30 cycles. It is decrease in RMS voltage of about 90 %  to  10 %  of nominal voltage. Although VS occurs for very short duration but its effects deteriorates system with time decreases life period of the system. The present work is an attempt to analyse the voltage sag on power distribution network with different transformer connections. The field specifications obtained are used in MATLAB/SIMULINK and the results are discussed.