This document summarizes a research paper that proposes a new high-efficiency voltage clamped DC-DC converter design with reduced reverse recovery current and switch voltage stress. The design uses a combination of an inductor and transformer to increase voltage gain. An additional inductor provides a reverse current path for the transformer to improve core utilization. Voltage clamping is used to reduce switch voltage stress, allowing the use of Schottky diodes at the output. Experimental results using a 250W proton exchange membrane fuel cell power source demonstrate the effectiveness of the proposed power conversion strategy.
High Voltage Gain Boost Converter for Micro source Power Conversion systemIDES Editor
The document presents a new high voltage gain boost converter design that uses a coupled inductor and voltage lift technique. Key features of the proposed converter include:
1) It can achieve a high voltage gain while operating at a duty ratio close to 0.65, allowing continuous conduction mode operation.
2) The coupled inductor design recycles energy stored in the leakage inductance, increasing efficiency by clamping voltage on the active switch.
3) A 250W prototype was built with 25V input and 240V output to demonstrate the converter's performance operating at 50kHz.
Steady-state analysis and derivations of voltage gain formulas are provided to explain the operating principles and performance advantages of the proposed
1. The document discusses a novel multistring inverter topology for distributed energy resources (DERs) based DC/AC conversion systems.
2. A high step-up converter is introduced as a front-end stage to improve conversion efficiency and stabilize the output DC voltage of various DERs, such as photovoltaics, for use with a simplified multilevel inverter.
3. The proposed inverter topology uses fewer switches than conventional designs to achieve multiple voltage levels, reducing cost, component counts, losses, and improving reliability.
1) The document presents a half bridge converter topology for battery charging applications.
2) A single stage half bridge converter is proposed that provides DC voltage regulation and power factor correction with only one controller.
3) The converter operation depends on whether the inductor is operating in discontinuous or continuous conduction mode, with discontinuous mode avoiding high voltage stress at light loads.
A HIGH EFFICIENCY CHARGE PUMP FOR LOW VOLTAGE DEVICESVLSICS Design
This document summarizes and analyzes different types of charge pump circuits. It begins by introducing charge pumps and their applications. It then reviews the Dickson charge pump circuit and identifies its limitation of threshold voltage drops across diodes. The document proposes a static CTS charge pump to address this but finds it also has issues from reverse charge sharing. Finally, a dynamic CTS charge pump is presented that uses additional transistors to fully turn on and off switches to prevent reverse charge flow and improve efficiency. Simulation results show its output voltage is higher than other designs.
PV Cell Fed High Step-up DC-DC Converter for PMSM Drive ApplicationsIJMTST Journal
In this concept novel high step-up dc–dc converter with an active coupled-inductor network is presented for
a sustainable energy system. The proposed converter contains two coupled inductors which can be
integrated into one magnetic core and two switches. The primary sides of coupled inductors are charged in
parallel by the input source, and both the coupled inductors are discharged in series with the input source to
achieve the high step-up voltage gain with appropriate duty ratio, respectively. In addition, the passive
lossless clamped circuit not only recycles leakage energies of the coupled inductor to improve efficiency but
also alleviates large voltage spike to limit the voltage stresses of the main switches. The reverse-recovery
problem of the output diode is also alleviated by the leakage inductor and the lower part count is needed;
therefore, the power conversion efficiency can be further upgraded. The voltage conversion ratios, the effect of
the leakage inductance and the parasitic parameters on the voltage gain are discussed. The voltage stress
and current stress on the power devices are illustrated and the comparisons between the proposed converter
and other converters are given. The simulation results are presented by using Mat lab/Simulink software.
Voltage Control of Dual Active Bridge Converter for CO-Amorphous Core Materia...kuldeep12555
Solid-State Transformer (SST) provides versatile power system operation. In the smart world, there are technologies where everything is incorporated that reduce the size and eventually save time in delivering a fast process. It has been seen that solid-state transformer voltage begins to decrease during operation that needs to be regulated through some control strategy. In this paper, a Dual Active Bridge (DAB) converter has been used to control the voltage of SST that employs the Single-Phase Shift (SPS) technique. For further efficiency improvement Co73(Si, B)27 co-amorphous material has been used for the core of SST because co-amorphous alloy has much lower loss compared with Fe-amorphous cores and have limited saturation flux density. Real-time parameters of core have been used in the analysis. It has been evident from the results that DAB dc-dc converter-based SST with SPS control technique is simple and offers better performance compared to stand-alone SST. It improves the overall performance and efficiency of the system. This paper has been accomplished in Matlab® / Simulink environment.
Keywords: Co73 (Si, B)27 Amorphous Core Material; Solid-State transformer (SST); Dual Active Bridge (DAB); High
voltage (HV) Application.
This document presents a high-efficiency interleaved active clamped DC-DC converter with a fuel cell for high voltage applications. Two current fed DC-DC converters are interleaved by connecting their inputs in parallel and outputs in series to reduce current ripples in the fuel cell and regulate output voltage ripples. An active clamping circuit is used to absorb switch turn-off voltage spikes, allowing low voltage devices with low resistance to be used. Voltage doubler circuits double the output voltage with a smaller transformer turns ratio and increased flexibility. Simulation in MATLAB verifies the proposed design's accuracy. The converter shows benefits including reduced current ripples, increased power handling, and improved voltage regulation for high power fuel cell systems.
Two-Stage Power Conversion Architecture Suitable for Wide Range Input VoltageProjectsatbangalore
This paper proposes a two-stage power conversion architecture suitable for wide input voltage ranges. The architecture combines a soft-charging switched-capacitor pre-regulator stage to compress a wide input voltage range into a narrower intermediate range, with a high-frequency magnetic regulator stage. This merged two-stage topology enables high efficiency, power density, and power factor for applications up to 30W requiring wide input voltage regulation, such as LED drivers. The approach is demonstrated through implementations of a 25-200V dc-dc converter achieving 88-96% efficiency at 30W, and an ac-dc converter with 88% efficiency and 0.93 power factor at 8.4W from an AC line.
High Voltage Gain Boost Converter for Micro source Power Conversion systemIDES Editor
The document presents a new high voltage gain boost converter design that uses a coupled inductor and voltage lift technique. Key features of the proposed converter include:
1) It can achieve a high voltage gain while operating at a duty ratio close to 0.65, allowing continuous conduction mode operation.
2) The coupled inductor design recycles energy stored in the leakage inductance, increasing efficiency by clamping voltage on the active switch.
3) A 250W prototype was built with 25V input and 240V output to demonstrate the converter's performance operating at 50kHz.
Steady-state analysis and derivations of voltage gain formulas are provided to explain the operating principles and performance advantages of the proposed
1. The document discusses a novel multistring inverter topology for distributed energy resources (DERs) based DC/AC conversion systems.
2. A high step-up converter is introduced as a front-end stage to improve conversion efficiency and stabilize the output DC voltage of various DERs, such as photovoltaics, for use with a simplified multilevel inverter.
3. The proposed inverter topology uses fewer switches than conventional designs to achieve multiple voltage levels, reducing cost, component counts, losses, and improving reliability.
1) The document presents a half bridge converter topology for battery charging applications.
2) A single stage half bridge converter is proposed that provides DC voltage regulation and power factor correction with only one controller.
3) The converter operation depends on whether the inductor is operating in discontinuous or continuous conduction mode, with discontinuous mode avoiding high voltage stress at light loads.
A HIGH EFFICIENCY CHARGE PUMP FOR LOW VOLTAGE DEVICESVLSICS Design
This document summarizes and analyzes different types of charge pump circuits. It begins by introducing charge pumps and their applications. It then reviews the Dickson charge pump circuit and identifies its limitation of threshold voltage drops across diodes. The document proposes a static CTS charge pump to address this but finds it also has issues from reverse charge sharing. Finally, a dynamic CTS charge pump is presented that uses additional transistors to fully turn on and off switches to prevent reverse charge flow and improve efficiency. Simulation results show its output voltage is higher than other designs.
PV Cell Fed High Step-up DC-DC Converter for PMSM Drive ApplicationsIJMTST Journal
In this concept novel high step-up dc–dc converter with an active coupled-inductor network is presented for
a sustainable energy system. The proposed converter contains two coupled inductors which can be
integrated into one magnetic core and two switches. The primary sides of coupled inductors are charged in
parallel by the input source, and both the coupled inductors are discharged in series with the input source to
achieve the high step-up voltage gain with appropriate duty ratio, respectively. In addition, the passive
lossless clamped circuit not only recycles leakage energies of the coupled inductor to improve efficiency but
also alleviates large voltage spike to limit the voltage stresses of the main switches. The reverse-recovery
problem of the output diode is also alleviated by the leakage inductor and the lower part count is needed;
therefore, the power conversion efficiency can be further upgraded. The voltage conversion ratios, the effect of
the leakage inductance and the parasitic parameters on the voltage gain are discussed. The voltage stress
and current stress on the power devices are illustrated and the comparisons between the proposed converter
and other converters are given. The simulation results are presented by using Mat lab/Simulink software.
Voltage Control of Dual Active Bridge Converter for CO-Amorphous Core Materia...kuldeep12555
Solid-State Transformer (SST) provides versatile power system operation. In the smart world, there are technologies where everything is incorporated that reduce the size and eventually save time in delivering a fast process. It has been seen that solid-state transformer voltage begins to decrease during operation that needs to be regulated through some control strategy. In this paper, a Dual Active Bridge (DAB) converter has been used to control the voltage of SST that employs the Single-Phase Shift (SPS) technique. For further efficiency improvement Co73(Si, B)27 co-amorphous material has been used for the core of SST because co-amorphous alloy has much lower loss compared with Fe-amorphous cores and have limited saturation flux density. Real-time parameters of core have been used in the analysis. It has been evident from the results that DAB dc-dc converter-based SST with SPS control technique is simple and offers better performance compared to stand-alone SST. It improves the overall performance and efficiency of the system. This paper has been accomplished in Matlab® / Simulink environment.
Keywords: Co73 (Si, B)27 Amorphous Core Material; Solid-State transformer (SST); Dual Active Bridge (DAB); High
voltage (HV) Application.
This document presents a high-efficiency interleaved active clamped DC-DC converter with a fuel cell for high voltage applications. Two current fed DC-DC converters are interleaved by connecting their inputs in parallel and outputs in series to reduce current ripples in the fuel cell and regulate output voltage ripples. An active clamping circuit is used to absorb switch turn-off voltage spikes, allowing low voltage devices with low resistance to be used. Voltage doubler circuits double the output voltage with a smaller transformer turns ratio and increased flexibility. Simulation in MATLAB verifies the proposed design's accuracy. The converter shows benefits including reduced current ripples, increased power handling, and improved voltage regulation for high power fuel cell systems.
Two-Stage Power Conversion Architecture Suitable for Wide Range Input VoltageProjectsatbangalore
This paper proposes a two-stage power conversion architecture suitable for wide input voltage ranges. The architecture combines a soft-charging switched-capacitor pre-regulator stage to compress a wide input voltage range into a narrower intermediate range, with a high-frequency magnetic regulator stage. This merged two-stage topology enables high efficiency, power density, and power factor for applications up to 30W requiring wide input voltage regulation, such as LED drivers. The approach is demonstrated through implementations of a 25-200V dc-dc converter achieving 88-96% efficiency at 30W, and an ac-dc converter with 88% efficiency and 0.93 power factor at 8.4W from an AC line.
A Novel Three Phase Multi-string Multilevel Inverter with High DC-DC Closed o...rnvsubbarao koppineni
This document proposes and analyzes a novel three-phase multi-string multilevel inverter for photovoltaic systems. The inverter uses a high step-up DC-DC converter to boost and stabilize the output DC voltage from multiple renewable energy sources. It then uses a simplified multilevel inverter topology with only six switches instead of the eight switches used in conventional cascaded H-bridge multilevel inverters, reducing losses. Simulation and experimental results show the inverter provides improved output waveforms, lower harmonics, reduced size and cost compared to other topologies.
This document describes a proposed three-phase isolated boost DC-DC converter for high voltage applications. Some key points:
1. The converter uses a Delta-Wye transformer connection to reduce the transformer turn ratio by half, addressing issues with high turn ratios like large leakage inductance.
2. A clamp circuit clamps surge voltages and reduces circulating currents, lowering conduction losses.
3. The converter achieves zero-voltage switching for all switches over a wide load range without affecting duty cycle, improving efficiency.
4. Simulation results validate the operating principles and features, making the converter well-suited for applications like electrolyzers that require high step-up voltage conversion.
Improving the Stability of Cascaded DC Power Supply System by Adaptive Active...IJMER
Abstract: When all links are changes in the cascade is the corner of the shape in the dc division
energy orbit (DEO). When resistances are intermission betwixt one by one stylish changes in that
would possibly end up so the cascaded orbits are unsteady. They are antecedent we can place in a
nearer to the useful in the cascaded orbit can be got in compelled to vary the supply they have load
changes in the internal structure of the same regions in the electrical device they can be opposed in
a quality of the characteristic of dc DEO. Throughout the Associate in nursing adaptation active
device in the (AACC) we can know another determined in the cascaded orbit. Therefore the AACC
was connected by side by side in the cascaded orbit’s they can mediate in between the carries and
completely a requirement of a notice then they carries the voltage with none modification in this
subsystems. Then it will have a stylish to the customary have basic units to measuring in the dc
DEO. When the AACC is additionally a similar bus device to cut back the output resistance of the
supply device, therefore averting in a interiority have their load changes in the input resistance, of
the cascaded orbit have their solutions then they becomes constant. We have important carrier
device it will computing in the AACC adaptation in line with they have output energy to the
cascaded orbit, they have energy vesting in the AACC that’s way they will reduced and therefore
they have a lot of energy in a reacting to the orbit so it is a best in the orbit of a submissive device.
What\'s many, since no capacitance have a requirement among an AACC, when the cascaded orbits
have their quantity of it slowly it will extend in time. They have activity fundamental truth to stop
their magnificence thought in the AACC are mentioned throughout of this project, it can have four
thousand eight hundred and zero watts cascaded orbit was contain a strive of process to move in a
full-bridge changes they can be styli shed and evaluated. So when the simulation solutions have to
clear the performance of the arrangement of AACC.
An Electrolytic-Free Offline LED Driver with a Ceramic-Capacitor-Based Compac...Projectsatbangalore
This document summarizes a research paper that presents the design and implementation of an electrolytic-free offline LED driver using a ceramic-capacitor-based stacked switched capacitor (SSC) energy buffer. The SSC energy buffer allows the driver to maintain a narrow DC bus voltage range while efficiently charging and discharging the ceramic capacitors over a wide voltage range. This improves the effective energy density compared to electrolytic capacitors. The prototype LED driver uses an optimized SSC energy buffer that achieves over 98% round-trip efficiency while reducing the total passive volume by more than half compared to an electrolytic-based design.
This document describes a study comparing the power dissipation of a 2:1 multiplexer designed using static CMOS logic versus an adiabatic logic style called 2PADCL (Two Phase Adiabatic Dynamic CMOS Logic). The 2:1 multiplexer was designed and simulated using both logic styles. Simulation results found that the multiplexer using 2PADCL adiabatic logic consumed significantly less power than the static CMOS implementation, with power savings of up to 65% observed under certain operating conditions. Adiabatic logic styles like 2PADCL achieve lower power by slowly charging and discharging circuit nodes and recycling stored charge, rather than abruptly switching nodes from 0V to the supply voltage.
This document summarizes a research paper that proposes and evaluates a novel interleaved ZCS boost DC-DC converter topology for photovoltaic interfaces. The converter uses two quasi-resonant switch blocks and lossless snubbers to achieve soft switching. Simulation results show the converter achieves reduced voltage and current ripple compared to conventional designs. A dual loop control scheme with an outer voltage loop and inner current loop is used to regulate the output. Coupling inductors between converter cells further improve transient response and reduce ripple. The proposed converter design and control scheme effectively interfaces photovoltaic systems with loads.
IRJET - A Zero Voltage Switching Pulse Width Modulated Multilevel Buck ConverterIRJET Journal
This document presents a new five-level zero voltage switching pulse width modulated multilevel buck converter. The proposed converter uses a multilevel topology to reduce voltage stresses on switches without adding extra voltage. It achieves zero voltage switching for all switches by utilizing active clamping and circulating reactive energy throughout the converter. Simulations in MATLAB were used to verify the performance of the proposed converter. The converter design and operating principles are explained, including modes of operation, component sizing equations, and simulation details.
Fuzzy Logic Controller based Bridgeless (BL) Isolated Interleaved Zeta Conver...IJPEDS-IAES
In recent times, high-brightness light emitting diodes (HB-LEDs) are
developing rapidly and it is confirmed to be the future development in
lighting not only because of their high efficiency and high reliability,
however also because of their other exceptional features: chromatic variety,
shock and vibration resistance, etc. In this paper, a bridgeless (BL) Isolated
Interleaved Zeta Converter is proposed for the purpose of reducing the diode
failures or losses; the value of output ripples also gets decreased. The
proposed BL isolated interleaved zeta converter operating in discontinuous
conduction mode (DCM) is used for controlling the brightness of LED
Driver with inherent PFC at ac mains using single voltage sensor. The fuzzy
logic controller (FLC) is used to adjust the Modulation Index of the voltage
controller in order to improve the dynamic response of LED Lamp driver.
Based on the error of converter output voltage, FLC is designed to select the
optimum Modulation Index of the voltage controller. The proposed LED
driver is simulated to achieve a unity power factor at ac mains for a wide
range of voltage control and supply voltage fluctuations.
Reduced Dielectric Losses for Underground Cable Distribution SystemsIJAPEJOURNAL
This paper describes the process to reduce dielectric losses for underground cable distribution system. As already known, that system is an alternative solution to energy distribution systems in urban areas. Influence of large capacitance is a separate issue that needs to be resolved.
Large capacitance effect on Express Feeder of 10 miles long has resulted in power losses more than 100 MW per month. In the no-load condition, current dispatch has recorded 10 Amperes, and has increased the voltage at receiving end by 200-500 Volts, with leading power factors.
Installation of the inductor to reduce cable loss dielectrics is done by changing the power factor (pf) to 0.85 lagging. After installation of the inductor, which is 5 mH/700 kVAR, dielectric losses is reduced to 3.57%, which is from 105,983 kW to 102,195 kWh per month. The capacitive leakage current has also been reduced from 249.61 Ampere to 245.17 Ampere.
IRJET- A DC-DC Converter with High Voltage Gain for Motor Applications us...IRJET Journal
This document describes a proposed DC-DC boost converter with high voltage gain for use in motor applications powered by a fuel cell. The converter aims to step up the low voltage output of the fuel cell to the higher voltage required by the motor drive. It uses a switched capacitor circuit and voltage multiplier configuration to achieve high voltage gain while maintaining a common ground and reducing voltage stress on the power switches. Simulation and experimental results show the converter can achieve a voltage gain sufficient for motor applications with high efficiency and a wide input voltage range. The proposed converter provides advantages over existing designs for fuel cell powered motors.
Single-Phase Inverter with Energy Buffer and DC-DC Conversion CircuitsAsoka Technologies
This paper proposes a new single-phase inverter topology and describes the control method for the proposed inverter. The inverter consists of an energy buffer circuit, a dc-dc conversion circuit and an H-bridge circuit. The energy buffer circuit and H-bridge circuit enable the proposed inverter to output a multilevel voltage according to the proposed pulse width modulation (PWM) technique. The dc-dc conversion circuit can charge the buffer capacitor continuously because the dc-dc conversion control cooperates with the PWM. Simulation results confirm that the proposed inverter can reduce the voltage harmonics in the output and the dc-dc conversion current in comparison to a conventional inverter consisting of a dc-dc conversion circuit and H-bridge circuit. Experiments demonstrate that the proposed inverter can output currents of low total harmonic distortion and have higher efficiency than the conventional inverter. In addition, it is confirmed that these features of the proposed inverter contribute to the suppression of the circuit volume in spite of the increase in the number of devices in the circuit.
Reliability improvement of micro inverter through ac-ripples voltage compensatorhunypink
This document summarizes a research paper that proposes a method to improve the reliability of micro-inverters by reducing AC ripples on the DC link capacitor. It describes how AC ripples from the inverter stage cause excess heat in the capacitor and reduce its lifespan. The paper presents a design for an "active power decoupling circuit" that uses a film capacitor, H-bridge, and control circuit to convert the second harmonic AC ripples into DC, thereby mitigating the ripples and increasing the capacitor life up to 19 years. Simulations show the proposed circuit reduces ripples from 9.4% to 3.2% compared to using just a bulk capacitor, while still maintaining total harmonic distortion
IRJET- Review on Various Topologis used for Decoupling of Fluctuating Power i...IRJET Journal
This document reviews various topologies used for decoupling fluctuating power in single-phase AC circuits. It discusses how active power decoupling techniques can help mitigate issues caused by power fluctuations, such as distorted power factor correction and reduced maximum power point tracking efficiency in applications like solar inverters. Specifically, it analyzes a symmetrical half-bridge circuit topology that uses minimal passive components to absorb power surges. The document also reviews several past studies on active power decoupling methods, capacitive energy storage approaches, and the benefits of film capacitors over electrolytic capacitors for power decoupling applications.
Conductor sag comparison for 132 kV overhead transmission line improvement in...journalBEEI
This paper presents conductor sag comparison for 132 kV overhead transmission line improvement in Malaysia. Increasing industrialization and population growth around the world demands higher electricity supply. Power generation has yet to decline but transmitting sufficient electricity to consumers is worrisome due to scarce land space occupied by rapid urbanization. Hence reconductoring method was chosen to improve existing 132 kV overhead transmission line in Malaysia. A group of selected conductors were chosen for comparison where the high temperature low sag conductor stood out the most producing up to 40% sag reduction. This paper focuses on providing conductor alternatives to improve maximum sag of lowest conductor to ground for 132 kV transmission line in Malaysia in accordance to her climate and geographical factor.
Architecture of an efficient dual band 1.8/2.5 GHz rectenna for RF energy har...TELKOMNIKA JOURNAL
This paper presents a highly efficient rectenna of RF energy harvesting systems operating at
1.8 GHz and 2.5 GHz bands for battery-less sensor application. The antenna is design by CST-MWS.
The Schottky diode used for rectifying circuit is HSMS 286B in which designed by Agilent ADS. The key
finding of the paper is that the simulated DC output voltage of the rectenna is 1.35 V for low input power of
-25 dBm at a high resistance load of 1M Ω. Correspondingly, the RF-DC conversion efficiency of
the rectification process is 59.51% and 45.75% at 1.8 GHz and 2.5 GHz, which are high efficiency and much
better compared to literature respectively. The rectenna is capable to produce 1.8 V from an input power of
-20 dBm. Thus, the proposed RF energy harvesting system offers a promising solution designed for efficient
functionality at a low power level of RF energy in the dual band.
Review of Reduction of Leakage Current in Cascaded Multilevel InverterIJRST Journal
Multilevel inverters are a source of high power, often used in industrial applications and can use either sine or modified sine waves. A multilevel inverter uses a series of semiconductor power converters (usually two to three) thus generating higher voltage. Reverse leakage current in a semiconductor device is the current from that semiconductor device when the device is reverse biased. In earlier method transformer is used for generating multilevel output and grid synchronization. Transformer increases the leakage current. Now transformerless method and sine modulation techniques are presented to reduce the leakage current.
1) The document presents a control strategy for a grid-interfacing inverter connected to renewable energy sources to improve power quality at the distribution level grid connection point.
2) By controlling the inverter, it can act as both a power converter to inject renewable power into the grid and as an active power filter to compensate for current unbalance, load harmonics, reactive power demand, and neutral current without additional hardware costs.
3) The control strategy aims to maximize utilization of the inverter rating and allows the inverter and nonlinear/unbalanced load at the point of common coupling to appear as a balanced linear load to the grid, maintaining power quality standards.
Electrical transmission systems and smart gridsSpringer
This document summarizes key components of electricity distribution systems and how distributed generation can impact their design and operation. It discusses distribution systems, substations, common distribution devices, and how automation schemes can integrate distributed generation while maintaining reliability and safety. Automation allows faults to be detected, isolated and service restored to unaffected areas, improving reliability metrics. Safety is ensured through various checks prior to automation actions.
Electrical transmission systems and smart gridsSpringer
This document summarizes key components of electricity distribution systems and how distributed generation can impact their design and operation. It discusses distribution systems, substations, common distribution devices, and how automation schemes can integrate distributed generation while maintaining reliability and safety. Automation allows faults to be detected, isolated and service restored to unaffected areas, improving reliability metrics. Safety is ensured through various checks prior to automation actions.
This document discusses simultaneous AC-DC power transmission through overhead transmission lines. It proposes a scheme where conductors can carry both AC and DC power independently. The DC power is injected at the neutral point of zig-zag transformers to avoid core saturation. Simulation studies are carried out to control the independent AC and DC power flows. This scheme allows existing transmission lines to be upgraded for higher power transfer without modifications to the lines, increasing their utilization.
Modeling, Simulation And Implementation Of Adaptive Optical System For Laser ...IJMER
Adaptive Optical System (AOS) for correction of beam jitter in a high power laser source is described. The jitter in a high power laser may results from platform vibrations and dynamically varying in-homogeneities in the lasing medium. The effect of beam jitter on the performance of high power laser in directed energy weapon (DEW) system is discussed. Simulation studies have been carried out to optimize parameters of jitter correction system. An experimental arrangement to stabilize a high power laser beam is described and results are presented.
Effect of Molybdenum Disulphide on Physical Properties of Neodymium-Iron-Boro...IJMER
The present paper reports the effect of molybdenum disulfide (MoS2) on magnetic and
mechanical properties of neodymium iron boron (NdFeB) bonded magnet. Powder metallurgy process
has been used to prepare the test samples containing 0.0, 0.5, 1, 1.5 and 2 percentage of MoS2. Compact
and hardness tests have been performed to measure the physical properties of samples. Saturation
magnetization, remanence and intrinsic coercivity have been checked using vibrating sample
measurement (VSM) test
A Novel Three Phase Multi-string Multilevel Inverter with High DC-DC Closed o...rnvsubbarao koppineni
This document proposes and analyzes a novel three-phase multi-string multilevel inverter for photovoltaic systems. The inverter uses a high step-up DC-DC converter to boost and stabilize the output DC voltage from multiple renewable energy sources. It then uses a simplified multilevel inverter topology with only six switches instead of the eight switches used in conventional cascaded H-bridge multilevel inverters, reducing losses. Simulation and experimental results show the inverter provides improved output waveforms, lower harmonics, reduced size and cost compared to other topologies.
This document describes a proposed three-phase isolated boost DC-DC converter for high voltage applications. Some key points:
1. The converter uses a Delta-Wye transformer connection to reduce the transformer turn ratio by half, addressing issues with high turn ratios like large leakage inductance.
2. A clamp circuit clamps surge voltages and reduces circulating currents, lowering conduction losses.
3. The converter achieves zero-voltage switching for all switches over a wide load range without affecting duty cycle, improving efficiency.
4. Simulation results validate the operating principles and features, making the converter well-suited for applications like electrolyzers that require high step-up voltage conversion.
Improving the Stability of Cascaded DC Power Supply System by Adaptive Active...IJMER
Abstract: When all links are changes in the cascade is the corner of the shape in the dc division
energy orbit (DEO). When resistances are intermission betwixt one by one stylish changes in that
would possibly end up so the cascaded orbits are unsteady. They are antecedent we can place in a
nearer to the useful in the cascaded orbit can be got in compelled to vary the supply they have load
changes in the internal structure of the same regions in the electrical device they can be opposed in
a quality of the characteristic of dc DEO. Throughout the Associate in nursing adaptation active
device in the (AACC) we can know another determined in the cascaded orbit. Therefore the AACC
was connected by side by side in the cascaded orbit’s they can mediate in between the carries and
completely a requirement of a notice then they carries the voltage with none modification in this
subsystems. Then it will have a stylish to the customary have basic units to measuring in the dc
DEO. When the AACC is additionally a similar bus device to cut back the output resistance of the
supply device, therefore averting in a interiority have their load changes in the input resistance, of
the cascaded orbit have their solutions then they becomes constant. We have important carrier
device it will computing in the AACC adaptation in line with they have output energy to the
cascaded orbit, they have energy vesting in the AACC that’s way they will reduced and therefore
they have a lot of energy in a reacting to the orbit so it is a best in the orbit of a submissive device.
What\'s many, since no capacitance have a requirement among an AACC, when the cascaded orbits
have their quantity of it slowly it will extend in time. They have activity fundamental truth to stop
their magnificence thought in the AACC are mentioned throughout of this project, it can have four
thousand eight hundred and zero watts cascaded orbit was contain a strive of process to move in a
full-bridge changes they can be styli shed and evaluated. So when the simulation solutions have to
clear the performance of the arrangement of AACC.
An Electrolytic-Free Offline LED Driver with a Ceramic-Capacitor-Based Compac...Projectsatbangalore
This document summarizes a research paper that presents the design and implementation of an electrolytic-free offline LED driver using a ceramic-capacitor-based stacked switched capacitor (SSC) energy buffer. The SSC energy buffer allows the driver to maintain a narrow DC bus voltage range while efficiently charging and discharging the ceramic capacitors over a wide voltage range. This improves the effective energy density compared to electrolytic capacitors. The prototype LED driver uses an optimized SSC energy buffer that achieves over 98% round-trip efficiency while reducing the total passive volume by more than half compared to an electrolytic-based design.
This document describes a study comparing the power dissipation of a 2:1 multiplexer designed using static CMOS logic versus an adiabatic logic style called 2PADCL (Two Phase Adiabatic Dynamic CMOS Logic). The 2:1 multiplexer was designed and simulated using both logic styles. Simulation results found that the multiplexer using 2PADCL adiabatic logic consumed significantly less power than the static CMOS implementation, with power savings of up to 65% observed under certain operating conditions. Adiabatic logic styles like 2PADCL achieve lower power by slowly charging and discharging circuit nodes and recycling stored charge, rather than abruptly switching nodes from 0V to the supply voltage.
This document summarizes a research paper that proposes and evaluates a novel interleaved ZCS boost DC-DC converter topology for photovoltaic interfaces. The converter uses two quasi-resonant switch blocks and lossless snubbers to achieve soft switching. Simulation results show the converter achieves reduced voltage and current ripple compared to conventional designs. A dual loop control scheme with an outer voltage loop and inner current loop is used to regulate the output. Coupling inductors between converter cells further improve transient response and reduce ripple. The proposed converter design and control scheme effectively interfaces photovoltaic systems with loads.
IRJET - A Zero Voltage Switching Pulse Width Modulated Multilevel Buck ConverterIRJET Journal
This document presents a new five-level zero voltage switching pulse width modulated multilevel buck converter. The proposed converter uses a multilevel topology to reduce voltage stresses on switches without adding extra voltage. It achieves zero voltage switching for all switches by utilizing active clamping and circulating reactive energy throughout the converter. Simulations in MATLAB were used to verify the performance of the proposed converter. The converter design and operating principles are explained, including modes of operation, component sizing equations, and simulation details.
Fuzzy Logic Controller based Bridgeless (BL) Isolated Interleaved Zeta Conver...IJPEDS-IAES
In recent times, high-brightness light emitting diodes (HB-LEDs) are
developing rapidly and it is confirmed to be the future development in
lighting not only because of their high efficiency and high reliability,
however also because of their other exceptional features: chromatic variety,
shock and vibration resistance, etc. In this paper, a bridgeless (BL) Isolated
Interleaved Zeta Converter is proposed for the purpose of reducing the diode
failures or losses; the value of output ripples also gets decreased. The
proposed BL isolated interleaved zeta converter operating in discontinuous
conduction mode (DCM) is used for controlling the brightness of LED
Driver with inherent PFC at ac mains using single voltage sensor. The fuzzy
logic controller (FLC) is used to adjust the Modulation Index of the voltage
controller in order to improve the dynamic response of LED Lamp driver.
Based on the error of converter output voltage, FLC is designed to select the
optimum Modulation Index of the voltage controller. The proposed LED
driver is simulated to achieve a unity power factor at ac mains for a wide
range of voltage control and supply voltage fluctuations.
Reduced Dielectric Losses for Underground Cable Distribution SystemsIJAPEJOURNAL
This paper describes the process to reduce dielectric losses for underground cable distribution system. As already known, that system is an alternative solution to energy distribution systems in urban areas. Influence of large capacitance is a separate issue that needs to be resolved.
Large capacitance effect on Express Feeder of 10 miles long has resulted in power losses more than 100 MW per month. In the no-load condition, current dispatch has recorded 10 Amperes, and has increased the voltage at receiving end by 200-500 Volts, with leading power factors.
Installation of the inductor to reduce cable loss dielectrics is done by changing the power factor (pf) to 0.85 lagging. After installation of the inductor, which is 5 mH/700 kVAR, dielectric losses is reduced to 3.57%, which is from 105,983 kW to 102,195 kWh per month. The capacitive leakage current has also been reduced from 249.61 Ampere to 245.17 Ampere.
IRJET- A DC-DC Converter with High Voltage Gain for Motor Applications us...IRJET Journal
This document describes a proposed DC-DC boost converter with high voltage gain for use in motor applications powered by a fuel cell. The converter aims to step up the low voltage output of the fuel cell to the higher voltage required by the motor drive. It uses a switched capacitor circuit and voltage multiplier configuration to achieve high voltage gain while maintaining a common ground and reducing voltage stress on the power switches. Simulation and experimental results show the converter can achieve a voltage gain sufficient for motor applications with high efficiency and a wide input voltage range. The proposed converter provides advantages over existing designs for fuel cell powered motors.
Single-Phase Inverter with Energy Buffer and DC-DC Conversion CircuitsAsoka Technologies
This paper proposes a new single-phase inverter topology and describes the control method for the proposed inverter. The inverter consists of an energy buffer circuit, a dc-dc conversion circuit and an H-bridge circuit. The energy buffer circuit and H-bridge circuit enable the proposed inverter to output a multilevel voltage according to the proposed pulse width modulation (PWM) technique. The dc-dc conversion circuit can charge the buffer capacitor continuously because the dc-dc conversion control cooperates with the PWM. Simulation results confirm that the proposed inverter can reduce the voltage harmonics in the output and the dc-dc conversion current in comparison to a conventional inverter consisting of a dc-dc conversion circuit and H-bridge circuit. Experiments demonstrate that the proposed inverter can output currents of low total harmonic distortion and have higher efficiency than the conventional inverter. In addition, it is confirmed that these features of the proposed inverter contribute to the suppression of the circuit volume in spite of the increase in the number of devices in the circuit.
Reliability improvement of micro inverter through ac-ripples voltage compensatorhunypink
This document summarizes a research paper that proposes a method to improve the reliability of micro-inverters by reducing AC ripples on the DC link capacitor. It describes how AC ripples from the inverter stage cause excess heat in the capacitor and reduce its lifespan. The paper presents a design for an "active power decoupling circuit" that uses a film capacitor, H-bridge, and control circuit to convert the second harmonic AC ripples into DC, thereby mitigating the ripples and increasing the capacitor life up to 19 years. Simulations show the proposed circuit reduces ripples from 9.4% to 3.2% compared to using just a bulk capacitor, while still maintaining total harmonic distortion
IRJET- Review on Various Topologis used for Decoupling of Fluctuating Power i...IRJET Journal
This document reviews various topologies used for decoupling fluctuating power in single-phase AC circuits. It discusses how active power decoupling techniques can help mitigate issues caused by power fluctuations, such as distorted power factor correction and reduced maximum power point tracking efficiency in applications like solar inverters. Specifically, it analyzes a symmetrical half-bridge circuit topology that uses minimal passive components to absorb power surges. The document also reviews several past studies on active power decoupling methods, capacitive energy storage approaches, and the benefits of film capacitors over electrolytic capacitors for power decoupling applications.
Conductor sag comparison for 132 kV overhead transmission line improvement in...journalBEEI
This paper presents conductor sag comparison for 132 kV overhead transmission line improvement in Malaysia. Increasing industrialization and population growth around the world demands higher electricity supply. Power generation has yet to decline but transmitting sufficient electricity to consumers is worrisome due to scarce land space occupied by rapid urbanization. Hence reconductoring method was chosen to improve existing 132 kV overhead transmission line in Malaysia. A group of selected conductors were chosen for comparison where the high temperature low sag conductor stood out the most producing up to 40% sag reduction. This paper focuses on providing conductor alternatives to improve maximum sag of lowest conductor to ground for 132 kV transmission line in Malaysia in accordance to her climate and geographical factor.
Architecture of an efficient dual band 1.8/2.5 GHz rectenna for RF energy har...TELKOMNIKA JOURNAL
This paper presents a highly efficient rectenna of RF energy harvesting systems operating at
1.8 GHz and 2.5 GHz bands for battery-less sensor application. The antenna is design by CST-MWS.
The Schottky diode used for rectifying circuit is HSMS 286B in which designed by Agilent ADS. The key
finding of the paper is that the simulated DC output voltage of the rectenna is 1.35 V for low input power of
-25 dBm at a high resistance load of 1M Ω. Correspondingly, the RF-DC conversion efficiency of
the rectification process is 59.51% and 45.75% at 1.8 GHz and 2.5 GHz, which are high efficiency and much
better compared to literature respectively. The rectenna is capable to produce 1.8 V from an input power of
-20 dBm. Thus, the proposed RF energy harvesting system offers a promising solution designed for efficient
functionality at a low power level of RF energy in the dual band.
Review of Reduction of Leakage Current in Cascaded Multilevel InverterIJRST Journal
Multilevel inverters are a source of high power, often used in industrial applications and can use either sine or modified sine waves. A multilevel inverter uses a series of semiconductor power converters (usually two to three) thus generating higher voltage. Reverse leakage current in a semiconductor device is the current from that semiconductor device when the device is reverse biased. In earlier method transformer is used for generating multilevel output and grid synchronization. Transformer increases the leakage current. Now transformerless method and sine modulation techniques are presented to reduce the leakage current.
1) The document presents a control strategy for a grid-interfacing inverter connected to renewable energy sources to improve power quality at the distribution level grid connection point.
2) By controlling the inverter, it can act as both a power converter to inject renewable power into the grid and as an active power filter to compensate for current unbalance, load harmonics, reactive power demand, and neutral current without additional hardware costs.
3) The control strategy aims to maximize utilization of the inverter rating and allows the inverter and nonlinear/unbalanced load at the point of common coupling to appear as a balanced linear load to the grid, maintaining power quality standards.
Electrical transmission systems and smart gridsSpringer
This document summarizes key components of electricity distribution systems and how distributed generation can impact their design and operation. It discusses distribution systems, substations, common distribution devices, and how automation schemes can integrate distributed generation while maintaining reliability and safety. Automation allows faults to be detected, isolated and service restored to unaffected areas, improving reliability metrics. Safety is ensured through various checks prior to automation actions.
Electrical transmission systems and smart gridsSpringer
This document summarizes key components of electricity distribution systems and how distributed generation can impact their design and operation. It discusses distribution systems, substations, common distribution devices, and how automation schemes can integrate distributed generation while maintaining reliability and safety. Automation allows faults to be detected, isolated and service restored to unaffected areas, improving reliability metrics. Safety is ensured through various checks prior to automation actions.
This document discusses simultaneous AC-DC power transmission through overhead transmission lines. It proposes a scheme where conductors can carry both AC and DC power independently. The DC power is injected at the neutral point of zig-zag transformers to avoid core saturation. Simulation studies are carried out to control the independent AC and DC power flows. This scheme allows existing transmission lines to be upgraded for higher power transfer without modifications to the lines, increasing their utilization.
Modeling, Simulation And Implementation Of Adaptive Optical System For Laser ...IJMER
Adaptive Optical System (AOS) for correction of beam jitter in a high power laser source is described. The jitter in a high power laser may results from platform vibrations and dynamically varying in-homogeneities in the lasing medium. The effect of beam jitter on the performance of high power laser in directed energy weapon (DEW) system is discussed. Simulation studies have been carried out to optimize parameters of jitter correction system. An experimental arrangement to stabilize a high power laser beam is described and results are presented.
Effect of Molybdenum Disulphide on Physical Properties of Neodymium-Iron-Boro...IJMER
The present paper reports the effect of molybdenum disulfide (MoS2) on magnetic and
mechanical properties of neodymium iron boron (NdFeB) bonded magnet. Powder metallurgy process
has been used to prepare the test samples containing 0.0, 0.5, 1, 1.5 and 2 percentage of MoS2. Compact
and hardness tests have been performed to measure the physical properties of samples. Saturation
magnetization, remanence and intrinsic coercivity have been checked using vibrating sample
measurement (VSM) test
Simcoe website presentation version 2 dec 16Miles McDonald
Simcoe Renewable Energy is a Canadian company that secures investment for solar energy projects including microgrids and utility-scale solar plants. The document outlines Simcoe's microgrid project for the Simcoe area, which would provide reliable solar-generated electricity. Key benefits of the microgrid include no upfront capital costs, an established price per kWh, reliability independent of the wider electricity grid, and energy cost savings of 20% compared to current costs. Simcoe handles project development, financing, construction, and long-term operation and maintenance through a power purchase agreement with the client.
User Navigation Pattern Prediction from Web Log Data: A SurveyIJMER
This paper proposes a survey of Web Page Prediction Techniques. Prefetching of Web page
has been widely used to reduce the access latency problem of the Web users. However, if Prefetching of
Web page is not accurate and Prefetched web pages are not visited by the users in their accesses, the
limited bandwidth of network and services of server will not be used efficiently and may face the problem
of access delay. Therefore, it is critical that we need an effective prediction method during prefetching.
The Markov models have been widely used to predict and analyze users navigational behavior. All the
activities of web users have been saved in web log files. The stored users session is used to extract
popular web navigation paths and predict current users next web page visit
This document contains a list of vocabulary words that could appear on the SAT exam. Some of the words in the list include revert, procrastinate, interminable, servile, fickle, pious, assimilate, amorphous, virulent, anarchy, transient, callow, desist, refute, extemporaneous, antiquate, waive, intermittent, supplant, and alchemy.
The document proposes a solution to allow apps to work seamlessly while still utilizing proxy server functionality like filtering and monitoring. The solution uses a transparent proxy and captive portal for authentication. A test bed was created using VirtualBox VMs including pfSense firewall, which has integrated proxy and captive portal services. Windows 8 and Ubuntu apps were tested and worked successfully without compromising proxy features. The proposed open source solution is widely applicable and cost-effective.
This document discusses websockets and their use for real-time communication. It begins with a definition of websockets as providing full-duplex communication channels over a single TCP connection. It then notes some key aspects of websockets like sending UTF-8 text or binary data, built-in heartbeating support, and browser support issues. The document highlights benefits of websockets like two-way communication and real-time data transfer without firewall interference but also notes compatibility concerns. It describes the websocket lifecycle and then outlines a project using websockets with Nginx, Node.js, and CoffeeScript for high-performance real-time applications across browsers.
The document summarizes a research study on the effect of case hardening treatment on the structure and properties of automobile gears. Specifically, it analyzes three gear materials: EN353, 20MNCR5, and SAE8620. The study examines the heat treatment procedures, microstructure, inclusion ratings, hardness gradients, and conclusions. Key findings include that inclusion ratings were within desired limits for all materials, 20MNCR5 showed the highest hardness gradient, and EN353 exhibited a sudden drop in hardness at the case depth of 0.6mm likely due to its lower chromium content.
A Threshold fuzzy entropy based feature selection method applied in various b...IJMER
Large amount of data have been stored and manipulated using various database
technologies. Processing all the attributes for the particular means is the difficult task. To avoid such
difficulties, feature selection process is processed.In this paper,we are collect a eight various benchmark
datasets from UCI repository.Feature selection process is carried out using fuzzy entropy based
relevance measure algorithm and follows three selection strategies like Mean selection strategy,Half
selection strategy and Neural network for threshold selection strategy. After the features are selected,
they are evaluated using Radial Basis Function (RBF) network,Stacking,Bagging,AdaBoostM1 and Antminer
classification methodologies.The test results depicts that Neural network for threshold selection
strategy works well in selecting features and Ant-miner methodology works best in bringing out better
accuracy with selected feature than processing with original dataset.The obtained result of this
experiment shows that clearly the Ant-miner is superiority than other classifiers.Thus, this proposed Antminer
algorithm could be a more suitable method for producing good results with fewer features than
the original datasets.
Seasonal Variational Impact of the Physical Parameters On Mohand Rao River F...IJMER
The paper depicts the seasonal variational impact on water quality of Doon Valley . Study was
proposed to analyze the various water sample of Mohand-Rao river flowing in the Mohand Anticline in
the lower parts of Shiwalik hills in Doon Valley for physico-chemical characteristics of water quality
parameters such as pH; Temperature; Conductivity; Hardness; Alkalinity; Total Solids; Total Dissolved
Solids; Total Suspended Solids..To analyze the physical, chemical, and toxicological parameters of
Streams and rivers.
This document provides tips for taking photos to accompany articles, emphasizing the importance of capturing stories through photos and taking multiple photos from different angles and perspectives to ensure the subject is captured effectively. Photographers are advised to get close to their subject, be aware of lighting, include action shots with emotion, vary high and low angles, focus on details, include repetition, and be patient when taking photos to tell the story. The assignment is to take at least 100 original photos during lunch without posed "grab and grin" shots.
An Effective Policy Anomaly Management Framework for FirewallsIJMER
International Journal of Modern Engineering Research (IJMER) is Peer reviewed, online Journal. It serves as an international archival forum of scholarly research related to engineering and science education.
Seemas Academy is an ISO 9001-2008 registered company based in Solapur, Maharashtra, India that was established in 2003 to provide brain development and math/science training courses based on Japanese abacus and Indian Vedic math concepts. The company aims to explore human talent and serve national advancement through imparting internationally standardized brain training. Courses offered include midbrain activation, speed reading, abacus, mental arithmetic, and Vedic mathematics for both children and adults.
Experimental studies have been conducted to understand disc brake noise and vibration. Researchers have used brake dynamometers and on-road testing to examine different parameters and operating conditions. They have measured vibration behavior using microphones and accelerometers. Studies have found that slotted discs can eliminate squeal vibration, while friction material and pad geometry changes can reduce it. Holographic interferometry has been used to view vibration modes on self-excited brakes. Further research aims to standardize noise measurement methods and remove subjective assessments to better understand noise generation and reduction.
The Impact of HIV/AIDS on Rural Household Welfare in Rukungiri District-UgandaIJMER
Many able bodied household members in Rukungiri district have died of
HIV/AIDS. Consequently there are many house heads (often young and married) whose partners
died. This study investigated the impact of HIV/AIDS on rural household welfare in Rukungiri
district. A control group approach was used. Data was collected by the use of questionnaires and
empirical observation from both the affected households and unaffected households. The study
aimed at finding out how HIV/AIDS has led to depletion of households’ productive assets. A
binary logistic regression analysis was used to establish whether there is a significant difference
in the sources of income for medical expenses between the affected households and unaffected
households with the aim of finding out the extent to which HIV/AIDS has led to depletion of
households’ productive assets and consequent deterioration in households’ welfare. The study has
established that HIV/AIDS has led to deterioration in the welfare of the affected households
through exhaustion of savings and increased borrowing, with the end result of depletion of
productive assets leaving the survivors with minimal means of survival. Productive assets
commonly depleted include; land, cattle, goats, chicken, sewing machines, wheelbarrows and
bicycles. However, affected households have adopted many coping strategies including those that
aim at improving food security, raising and supplementing their incomes so as to maintain their
expenditure patterns, and coping with loss of labour. Since emergency traditional indigenous
groups are already operating in all the communities in the district acting as a source of
psychosocial support to individuals and communities affected by HIV/AIDS with their activities
such as assisting with burial ceremonies, communal farming, supporting sick patients, rebuilding
dwellings and rehabilitating farms, supporting survivors and creating income generating activities
and providing material support, the study recommends government support in collaboration with
donor agencies to provide them with training in HIV/AIDS home care support and enough funds to
enable them meet their requirements. Government in collaboration with NGOs operating in the
area should introduce short-term training courses in the affected areas to empower the survivors
with practical skills and equip them with capital that can enable them create jobs for themselves.
Further, improving agricultural yields through teaching them modern farming practices, provision
of free anti-retroviral therapies by the government to all the affected households, accompanied by
provision of food rations for boosting nutritional requirements would reduce the depletion of
productive assets of these households.
Crack in component if undetected may lead to catastrophic failure of the component. The
cracked rotor problem received the first attention in 1970 and after that the interest among the
researchers started. The vibration behavior of cracked structures, in particular cracked rotors, is
important to study as the introduction of the crack alters the vibration characteristics of the structure.
The problem of damage and crack detection in structural components has acquired important role in past
few years. However, cracked rotor studies are mainly deals with single crack. For multiple cracked
structures the problem of crack sizing and location becomes more complex. Only few authors have
pointed out the multiple crack assessment in the rotor. The proposed work is on vibration analysis of
multiple cracked shaft beam. An Euler Bernoulli beam fixed at one end with two transverse cracks is
considered. The vibration characteristics of the shaft are studied using Experimental Modal Analysis and
Finite Element Analysis. The mode shapes and natural frequencies of the beams are studied and their
variation with change in position and depth of the crack is also studied. The study shows good agreement
of the results obtained using Finite Element Analysis and Experimental Modal Analysis.
Report Card Night is an event where teachers meet with parents for 3 minute "mini conferences" over a 90 minute period in the gym to discuss student progress and grades. Teachers are seated alphabetically at tables with students' grades and laptops. Parents pick up report cards, choose which teachers to meet with, and visit them directly for feedback. This format provides more meaningful parent-teacher interaction than traditional open houses. Benefits include immediate feedback, no lost report cards, and parents can target specific teachers. Potential issues are ensuring enough space and technology for conferences within the 90 minute time period.
Speech Recognition for Agriculture based Interactive Voice Response SystemIJMER
This document discusses the development of an interactive voice response system (IVRS) for agricultural assistance for farmers in Marathi. It summarizes:
1) A Marathi speech database was created related to agricultural applications, including names of crops, infection symptoms, and disease names and solutions. This database was used to train and test the IVRS system.
2) An IVRS model called AGRO IVRS was proposed that would allow farmers to get information about crop diseases and solutions by phone in their native Marathi language.
3) The system was experimentally tested and achieved an overall recognition rate of 91% for 260 sentences. The IVRS model has the potential to provide farmers with 24/7 remote access to
Performance of MMSE Denoise Signal Using LS-MMSE TechniqueIJMER
This paper presents performance of mmse denoises signal using consistent cycle spinning
(ccs) and least square (LS) techniques. In the past decade, TV denoise technique is used to reduced the
noisy signal. The main drawback is the low quality signal and high MMSE signal. Presently, we
proposed the CCS-MMSE and LS-MMSE technique .The CCS-MMSE technique consists of two steps.
They are wavelet based denoise and consistent cycle spinning. The wavelet denoise is powerful
decorrelating effect on many signal domains. The consistent cycle spinning is used to estimation the
MMSE in the signal domain. The LS-MMSE is better estimation of MMSE signal domain compare to
CCS-MMSE.The experimental result shows the average MMSE reduction using various techniques.
The magazine uses a bright color scheme and prominent masthead to attract older, loyal viewers interested in weekly television programs. It encourages brand loyalty through its website listed in the masthead and provides value with multiple television program features and images. The largest headline teases a mystery to engage readers in learning more about the main story.
Design and implementation a novel single switch high gain DC-DC converter ba...IJECEIAES
A novel high-gain and high-efficiency direct current to direct current
(DC-DC) converter is introduced in this paper. The presented converter is suitable for low-voltage renewable energy resources such as photovoltaic (PV) and fuel cell (FC). The existence of series inductance with the input source ensures continuous and low-ramp input current, which is important for extracting maximum power from resources. Using coupled inductor technology and an intermediate capacitor in the suggested converter leads to a high gain voltage. In the presented topology for recovering energy from the leakage inductor, reducing voltage stress on the power switch, and so decreasing overall converter losses, a passive clamp circuit is used. The suitable operation range of duty cycle in the converter, besides the leakage inductor, decreases the problem of reverse recovery in diodes. The low value of the leakage inductor and the low volume and cost of the proposed converter are due to the low turn ratio of the coupled inductor. Details of the operation principles of the proposed converter have been discussed in this paper. The presented simulation and laboratory prototype results verify the theoretical analysis and performance of the suggested topology.
The document discusses design and implementation of a soft switched high gain current fed full bridge DC-DC converter for fuel cell applications. It provides background on fuel cells and the need for a power electronics interface to convert unregulated electric power from alternative energy sources into usable power. The challenges include designing an efficient and low cost power converter with high efficiency during load operation, large step-up ratio, and low input ripple current. Various converter topologies are reviewed from literature including boost, interleaved boost, coupled inductor, flyback, and half/full-bridge converters. The proposed converter design and steady state analysis is presented along with theoretical waveforms and discussion of hardware implementation.
High Step-Up Converter with Voltage Multiplier Module for Renewable Energy Sy...IJRES Journal
In this project, A novel high step-up converter, which is suitable for renewable energy system, is proposed.Through a voltage multiplier module composed of switched capacitors and coupled inductors, a conventional interleaved boost converter obtains high step-up gain without operating at extreme duty ratio.The configuration of the proposed converter not only reduces the current stress but also constrains the input current ripple, which decreases the conduction losses and lengthens the lifetime of the input source. In addition, due to the lossless passive clamp performance, leakage energy is recycled to the output terminal. Hence, large voltage spikes across the main switches are alleviated, and the efficiency is improved.
High Step-Up Converter with Voltage Multiplier Module for Renewable Energy Sy...irjes
In this project, A novel high step-up converter, which is suitable for renewable energy system, is proposed.Through a voltage multiplier module composed of switched capacitors and coupled inductors, a conventional interleaved boost converter obtains high step-up gain without operating at extreme duty ratio.The configuration of the proposed converter not only reduces the current stress but also constrains the input current ripple, which decreases the conduction losses and lengthens the lifetime of the input source. In addition, due to the lossless passive clamp performance, leakage energy is recycled to the output terminal. Hence, large voltage spikes across the main switches are alleviated, and the efficiency is improved.
High-Power Bidirectional Dual Active Bridge and Double Dual Active Bridge DC-...IRJET Journal
The document summarizes a high-power bidirectional dual active bridge DC-DC converter. It discusses how dual active bridge converters use two full-bridge circuits connected by a transformer and inductor to enable bidirectional power flow and control power transfer between two DC sources by phase shifting square wave voltages generated by each bridge. Zero-voltage switching is enabled through resonance of the inductor and snubber capacitor, improving efficiency. The dual active bridge converter is well-suited for applications requiring high power density and bidirectional power flow such as balancing energy storage systems in aircraft.
Analysis of Fuel Cell Based Multilevel DC-DC Boost Converter for Induction MotorIJMTST Journal
In this paper new topologies and interleaving modulation concepts for multilevel DC-DC boost converter
enabling a significantly less loss and a reduced chip size of the power semiconductors are proposed. The
distributed generation (DG) systems based on the renewable energy sources have rapidly developed in
recent years. These DG systems are powered by micro sources such as fuel cells, photovoltaic (PV) systems,
and batteries. Fuel cells are considered to be one of the most promising sources of distributed energy because
of their high efficiency, low environmental impact and scalability. Non-isolated high step-up DC-DC
converters are required in the industrial applications. Many of these conventional DC–DC converters have the
disadvantages of operating at high duty-cycle, high switch voltage stress and high diode peak current. A
three-level step up converter is implemented to boost the fuel cell stack voltage of 96V to 340V. The proposed
converter consists a system of fuel cell based Multilevel DC-DC converter with PI controller is modeled and
simulated by using Matlab/Simulink.
A Novel Integrated AC-DC Five Level Converter Strategy for Power Factor Corre...IJMTST Journal
Multilevel configuration has the advantage of its simplicity and modularity over the configurations of the other converters. With the application of multilevel converter in the high voltage and large power occasions in recent years, its modulation strategy has become a research hot point in the field of power electronics. The proposed power-factor-correction circuit can achieve unity power factor and ripple-free input current using a coupled inductor. The proposed rectifier can also produce input currents that do not have dead band regions and an output current that is continuous for all load conditions. The features of this converter are that it has lower input section peak current stresses and a better harmonic content than similar converter with a non-interleaved output, the output current is continuous for all load ranges, and the dc bus voltage is less than 450 for all line and load conditions. In this paper, the operation of the new converter is explained, its steady-state characteristics are determined by analysis, and these characteristics are used to develop a procedure for the design of the converter. Hence the simulation results are obtained using MATLAB/SIMULINK software. The proposed system provides a closed loop control for variable output voltage. The SSPFC AC/DC converter can operate with lower peak voltage stresses across the switches and the DC bus capacitors as it is a three-level converter. The proposed concept can be implemented with 5-level for efficient output voltage.
Universal demand for power increases due to continuous development to fulfil all these demand. Resources
are used with optimization. A high efficiency and high power factor converters are the major parts of energy
transfer system. This paper present a general review on single stage forward and flyback converter topologies to get
better its performance. This is paper presents a kind general idea of increasing efficiency and power factor of single
stage forward and fly back converter.
An Asymmetrical Dc-Dc Converter with a High Voltage GainIJMER
An asymmetrical full bridge converter is proposed in the paper. The proposed converter
achieves zero voltage switching of all the power switches. Zero current switching of all the output diodes
are also achieved here. This in turn provides a highly efficienct operation. The proposed converter can
provide a high voltage gain and the voltages across the semi- conductor devices are effectively clamped.
The converter can be utilised effectively in high voltage applications as embedded systems, renewable
energy systems, fuel cells, mobility applications and uninterrupted power supply
A Novel High Step-Up DC–DC Converter for Hybrid Renewable Energy System appli...IJERD Editor
Large electric drives and utility applications require advanced power electronics converter to meet
the high power demands. As a result, power converter structure has been introduced as an alternative in high
power and medium voltage situations using Renewable energy sources (RES). This paper describes a new
DC/DC converter with safety, high efficiency and high step up capabilities. This converter is best suited for
Wind/Fuel cell(FC)based Induction Motor applications for pumping systems. The safety feature of this
converter makes it friendly for the farmers to use it for irrigation and agriculture usages. The converter achieves
high step-up voltage gain with appropriate duty ratio and low voltage stress on the power switches. Also, the
energy stored in the leakage inductor of the coupled inductor can be recycled to the output. The maximum
output voltage is determined by the number of the capacitors. The capacitors are charged in parallel and are
discharged in series by the coupled inductor, stacking on the output capacitor. Thus, the proposed converter can
achieve high step-up voltage gain with appropriate duty ratio and interfaced to induction motor through 9-level
inverter and also energy fed to grid system when no load operation. The simulation results are obtained using
MATLAB/SIMULINK software.
IRJET- A DC-DC Converter with High Voltage Gain for Motor Applications using ...IRJET Journal
This document describes a proposed DC-DC boost converter with high voltage gain for use in motor applications powered by fuel cells. The converter aims to step up the low output voltage of the fuel cell to the higher voltage required by the motor drive system. It uses two inductors, five capacitors, and two switches operating simultaneously to achieve a high voltage gain without extreme duty cycles. The converter is intended to address issues with existing converters, such as high voltage stress on components, lack of a common ground, and inability to power motor loads. It is analyzed theoretically and through simulation to validate its performance.
Closed loop simulation and hardware implementation of a LED driving circuit f...IJERA Editor
This work deals with the design and implementation of an AC to DC LED driving circuit consisting of a buck
boost converter and a flyback converter. A buck boost converter is integrated with a fly back converter by
sharing a single power switch. A recycling path is also provided to recycle the leakage energy stored in
transformer. An EMI filter and a diode bridge rectifier is also included in this converter topology, EMI filter is
used to eliminate high frequency current harmonics at the input line. Diode bridge rectifier is used to convert
AC source voltage to DC voltage. The control of this single switch is done by using DSPIC 30F2010.This
converter has simple structure, low cost, and ease of control as well. In this way, the developed converter can
provide high PF and low total harmonic distortion.
The detailed circuit operations and analysis are provided. The theoretical studies and analysis are tested by a
prototype of 16-W LED driver with a switching frequency of 60 kHz and also a closed loop simulation is done
in MATLAB simulink. The developed converter has maximum power factor of 0.96 and total harmonic
distortion of 10.54%
Coupled Inductor Based High Step-Up DC-DC Converter for Multi Input PV SystemIJERA Editor
With the shortage of the energy and ever increasing of the oil price, research on the renewable and green energy
sources, especially the solar arrays and the fuel cells, becomes more and more important. How to achieve high
step-up and high efficiency DC/DC converters is the major consideration in the renewable power applications
due to the low voltage of PV arrays and fuel cells. In this paper a coupled inductor dc-dc converter for photovoltaic
system is proposed. The circuit configuration of the proposed converter is very simple. Thus, the
proposed converter has higher step-up and step-down voltage gains than the conventional bidirectional dc–dc
boost/buck converter. Under same electric specifications for the proposed converter and the conventional
bidirectional boost/buck converter, the average value of the switch current in the proposed converter is less than
the conventional bidirectional boost/buck converter. The operating principles have been applied to multi input
photovoltaic system and outputs have been observed.
Basic MOSFET Based vs Couple-Coils Boost Converters for Photovoltaic GeneratorsIJPEDS-IAES
This document discusses different boost converter designs for photovoltaic generators. It compares a basic MOSFET-based boost converter to a proposed couple-coils boost converter. The basic converter uses discrete components like an inductor, freewheeling diode, and power MOSFET switch. Loss analyses are performed on these components. A coupled-coils design is proposed to minimize losses by integrating a low voltage MOSFET and very low resistance inductor. The goal is to design high efficiency converters for medium and high voltage photovoltaic systems connected to 230V AC grids.
This document summarizes a research paper that proposes a novel high-gain DC-DC boost converter design with a low component count. The key points are:
1) The proposed converter uses one power switch, two inductors, two capacitors, and three diodes to achieve high voltage gain while keeping the overall component count lower than other similar designs.
2) It operates in two switching modes and was simulated using PSIM software, with promising results showing reliable performance.
3) A mathematical analysis of the converter's steady-state voltage gain, voltage stresses, and efficiency is presented. The design could enable applications requiring high voltage gain in small spaces.
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Most of the industrial applications use any one of the basic DC-DC converter configurations namely buck,
boost, buck–boost, and Cuk converters. These converters are non-isolating converters. Buck-boost converters
use inductors for storing energy from the source and release the same to load or output. This results in high
stress across magnetic components. This drawback restricts usage of buck-boost converters to low power
applications. Flyback converters popularly have known as buck-boost converters uses transformers for
achieving wide range of step down and step up voltages. Coupled inductor based converters or tapped inductor
based converters are used for achieving wide input – wide output conversion ratios. Coherent transition between
step-down and step-up modes is achieved by a proper control scheme. This paper proposes fuzzy logic based
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This paper proposes a non-isolated soft-switching bidirectional dc/dc converter for interfacing energy storage in DC microgrid. The proposed converter employs a half-bridge boost converter at input port followed by a LCC resonant tank to assist in soft-switching of switches and diodes, and finally a voltage doubler circuit at the output port to enhance the voltage gain by two times. The LCC resonant circuit also adds a suitable voltage gain to the converter. Therefore, overall high voltage gain of the converter is obtained without a transformer or large number of multiplier circuit. For operation in buck mode, the high side voltage is divided by half with capacitive divider to gain higher step-down ratio. The converter is operated at high frequency to obtain low output voltage ripple, reduced magnetics and filters. Zero voltage turn-on is achieved for all switches and zero current turn-on and turn-off is achieved for all diodes in both modes i.e., buck/boost operation. Voltage stress across switches and diode is clamped naturally without external snubber circuit. An experimental prototype has been designed, built and tested in the laboratory to verify the performance of the proposed converter.
The document describes a novel high-gain, high-power DC-DC converter topology for photovoltaic applications. The proposed converter consists of three interleaved boost converters with coupled inductors as the input inductors, along with two voltage multiplier cells. It is able to achieve a voltage gain of 10 and deliver 3kW of output power at 88% efficiency. The operating principle involves eight stages where the switches and diodes operate to transfer energy between the inductors and capacitors, providing high voltage gain while reducing voltage stress on the components. Simulation results validate the design concept and its advantages over existing solutions.
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Voltage Clamped Dc-Dc Convertor with Reduced Reverse Recovery Current And Stability Analysis
1. International Journal of Modern Engineering Research (IJMER)
www.ijmer.com Vol.2, Issue.6, Nov-Dec. 2012 pp-4273-4279 ISSN: 2249-6645
Voltage Clamped Dc-Dc Convertor with Reduced Reverse Recovery
Current And Stability Analysis
Dharamalla. ChadraSekhar, 1 D. Jagan, 2
1, 2
Assistant Professor /GATE Engineering College / JNTU, Hyderabad/ AP /INDIA.
Abstract: this paper in vest gates a high-efficiency soft switching. In [8] and [9], coupled inductors were
clamped-voltage dc–dc converter with reduced reverse- employed to provide ea high step-up ratio and to reduce the
recovery current And switch-voltage stress. In the circuit switch-voltage stress substantially, and the reverse-recovery
topology, it is designed by way of the combination of in duct problem of the output diode was also alleviated efficiently.
or and transformer to increase the corresponding voltage In this case, the leakage energy of the coupled
gain. Moreover, one additional inductor provides the inductor is another problem as the main switch was turned
reverse-current path of the transformer to enhance the OFF. It will result in a high voltage ripple a cross the main
utility rate of magnetic core. In addition, the voltage- switch due to the resonant phenomenon induced by the
clamped technology issued to reduce the switch-voltage leakage current. In order to protect the switch devices, either
stress so that it can select the Scotty diode in the output a high-voltage-rated device with higher RDS (ON) or a
terminal for all aviating the reverse recovery current and snubber circuit is usually adopted to deplete the leakage
decreasing the witching and conduction losses. Fur the energy. Consequently, the power-conversion efficiency will
more; the closed-loop control methodology is utilization the be degraded. Zhao and Lee [10] introduced a family of high-
proposed scheme to overcome the voltage-drift problem of efficiency high-step-up dc–dc converters by only adding one
power source under the variation of loads. Thus, the addition diode and a small capacitor. It can recycle the
proposed converter topology has a favor able voltage- leakage energy an
clamped effect and superior conversion efficiency. Some
experimental results via an example of a proton exchange
membrane fuel cell (PEMFC) power source with a 250-W
nominal rating are given to demonstrate the effectiveness of
the proposed power-conversion strategy.
Index Terms: Converter, fuel cell, proton-exchange
membrane (PEM), reverse recovery, voltage clamped.
I. INTRODUCTION
INRECENT years, dc–dc converter switch steep
voltage ratio are usually require din many industrial
applications, e.g., the front-end stage for clean energy
sources, the dc backup energy system for an uninterruptible
power supply (UPS),high-intensity discharge (HID) lamps Fig. 1. System configuration of a high -efficiency
for automobile head lamps, And the telecommunication voltage-clamped dc–dc converter.
industry[ 1]–[3].The conventional boost converters cannot
provide such a high dc-voltage ratio due to the losses Alleviate the reverse-recovery problem. However,
associated with the inductor, filter capacitor, main switch, a snubber circuit is still required in the output diode terminal
and output diode. Even for an extreme duty cycle, It will with extra energy losses.
result in serious reverse-recovery problems and increase The Nowadays, fuel cells are in the news because they
rating of the output diode. As a result, the conversion appear to be one of the most efficient and effective solutions
efficiency is degraded, and the electromagnetic interference to the environmental pollution problem [11]–[17]. A fuel
(EMI) problem is severe under this situation [4].In order to cell is an energy conversion device that produces electricity
increase the conversion efficiency and voltage gain, many by electrochemically combining fuel (hydrogen) and oxidant
modified boost converter topologies have been investigated (oxygen from the air) gases through electrodes, across an
in the past decade[5]–[10]. ion conduction electrolyte. This process produces much
Although voltage-clamped techniques are higher conversion efficiency than any conventional thermal-
manipulated in the converter design to overcome the severe mechanical system, because it operates without combustion
reverse-recovery problem of the output diode in high-level and extracts more electricity from the same amount of fuel.
voltage applications, there still exist over large switch- This system has the merits of high efficiency, energy
voltage stresses, and the voltage gain is limited by the turn- security, reliability, pollution free, and quiet operations. Fuel
ON time of the auxiliary switch [5], [6].da Silva et al. [7] cells have been known to science for more than 160 years
presented a boost soft-single-switch converter, which has and have recently become the subject of intense research
only one single active switch. It is able to operate with soft and development. Up to the present, many demonstration
switching in a pulse width modulation (PWM) way without projects have shown fuel-cell systems to be feasible for
high voltage and current stresses. Unfortunately, the voltage portable power, transportation, utility power and on-site
gain is limited below four in order to achieve the function of power generation in a variety of building applications.
www.ijmer.com 4273 | Page
2. International Journal of Modern Engineering Research (IJMER)
www.ijmer.com Vol.2, Issue.6, Nov-Dec. 2012 pp-4273-4279 ISSN: 2249-6645
For portable power, a fuel cell with a fuel container transformer is modeled as an ideal transformer with a
can offer a higher-energy density and more convenience secondary leakage inductor (Lk). The turn’s ratio of this
than conventional battery systems. Moreover, portable ideal transformer is defined as
power packs using fuel cells can be lighter and smaller in
volume for an equivalent amount of energy. In
(1)
transportation applications, fuel cells offer higher efficiency
Where N1 and N2 are the primary and secondary
and better part-load performance than conventional engines.
winding turns. The additional inductor (L) is located in
In stationary power applications, low emissions permit fuel
parallel with the primary side of the transformer. Moreover,
cells to be located in high-power requirement areas, where
the rectifier diodes (D1, D2, D3, and D4) are connected
they can supplement the existing utility grid. Using fuel
between the primary and secondary sides of the transformer.
cells and hydrogen technology, electrical power can be
The voltages across the additional inductor, the main switch,
delivered cleanly, efficiently and sustainability where and
the ideal transformer primary and secondary winding, the
when required. The greatest research interests throughout
secondary leakage inductor, the balanced capacitor, and the
the world have focused on proton-exchange membrane
output diode are vL, vDS, vLp , vLs , vLk , vCs , and vDo,
(PEM) and solid oxide cell stacks. Specially, PEM
respectively. The clamped capacitor Cc is assumed to be
fuel cell (PEMFC) has promising characteristics as follows:
large enough to be viewed as a constant voltage source, VCc
1) the by-product waste is water; 2) low-temperature
. The conductive voltage drops of the main switch
operation; and 3) they use a solid polymer as the electrolyte
(S) And all diodes (D1, D2, D3, D4, and Do) are
that reduces concerns related to construction, transportation,
neglected to simplify the circuit analyses. The characteristic
and safety issues [16]. Thus, it seems to be a good
waveforms of the proposed high-efficiency converter are
alternative source for distributed generation systems.
depicted in Fig. 3. In addition, Fig. 4 illustrates the
The aim of this study is to design a high-efficiency
operational modes in one switching cycle, and the detailed
voltage clamped dc–dc converter with reduced reverse-
operation stages are described as follows.
recovery current and switch-voltage stress to provide a
stable constant dc voltage. To achieve this goal, the
manipulation of inductor and transformer is adopted to
increase the voltage gain and to enhance the utility rate of
the magnetic core. Moreover, the voltage-clamped
technology is used for reducing the switch voltage stress and
solving the reverse-recovery problem. In addition, the
closed-loop control methodology is utilized in the proposed
converter to overcome the voltage-drift problem of power
source under the variation of loads. The prototype is
developed for a PEMFC application requiring an output
power of 310 W, an output voltage of 200 V, and an input
voltage varying from 27 to 37.5 V. The remainder of this
study is organized as follows. Section II presents the
converter design and analyses in detail. Experimental results
for a PEMFC power source with a 250-W nominal rating are
provided to validate the effectiveness of the proposed power
conversion system in Section III. Conclusions are drawn in Fig. 2. Equivalent circuit.
Section IV.
II. CONVERTER DESIGN AND ANALYSES:
A newly designed converter topology is depicted in
Fig. 1, where it contains five parts including a dc-input
circuit, a primary-side circuit, a secondary-side circuit, a dc-
output circuit, and a feedback-control mechanism. The
major symbol representations are summarized as follows. Vi
and Ii denote the dc-input voltage and current, and Ci is the
input filter capacitor in the dc-input circuit. Lp represents
the primary inductor of the transformer; L is the additional
inductor in the primary-side circuit; and S is the main
switch. Ls denote the secondary inductor of the transformer;
Cs and Cc are the balanced capacitor and clamped capacitor
in the secondary-side circuit; and D1, D2, D3, and D4 are
the rectifier diodes. Vo and Io describe the output voltage
and current; Ro is the output load; Do, and Co are the output
diode and filter capacitor in the output circuit. Vcom and TS
are the output-voltage command and switch-driving signal Fig. 3. Characteristic waveforms.
in the feedback-control mechanism, respectively.
The equivalent circuit and state definition of the A. Mode 1 (t0 − t1) [Fig. 4(a)]
newly designed converter is depicted in Fig. 2, where the
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www.ijmer.com Vol.2, Issue.6, Nov-Dec. 2012 pp-4273-4279 ISSN: 2249-6645
At time t = t0, the main switch (S) is turned ON. At
the sametime, the diodes (D1 and D4) become conducted,
and other diodes (D2, D3, and Do) are reverse biased. The
additional inductor (L) and clamped capacitor (Cc) are
linearly charged by the input-voltage source (Vi) through the
transformer. Applying Kirchhoff’s law [4], the voltages of
vL, vLp , vLs , and vLk during this period can be expressed
as
vL =vLp =Vi (2)
vLs =nVi (3)
vLk =VCc− nVi − vCs . (4)
According to (2)–(4), the rate of change of the additional
inductor current (iL), the primary-side current (iLp ), and the
secondary-side current (iLs ) of the transformer can be
represented as
Fig.4.Operational modes: (a) mode 1 [t0 − t1]; (b) mode
2 [t1 − t2];(c) mode 3 [t2 − t3]; (d) mode 4 [t3 − t4].
B. Mode 2 (t1 − t2) [Fig. 4(b)]
At time t = t1, the main switch (S) is turned OFF.
At this time, the diodes (D2, D3, and Do) become forward
biased to start conducting, and other diodes (D1 and D4) are
reverse biased. The stored energy of the additional inductor
(L) and clamped capacitor (Cc) in Mode 1 is released to
output loads. Moreover, the transformer can be operated at Where iDo is the current of the output diode Do;
four quadrants to enhance the utility rate of the magnetic iCc is the current of the clamped capacitor Cc. According to
core and to keep the clamped voltage (VCc), since the (11), the cutoff voltage of the main switch (S) is clamped at
additional inductor (L) sup supplies energy to the output Vo − VCc. Moreover, the main switch (S) with low-voltage-
terminal by way of the transformer. Applying Kirchhoff’s rated capacity can be selected since the switch-voltage stress
law [4], the voltage and current relations of each element (vDS) is smaller than the output voltage (Vo). The selection
during this mode can be described by of a low-voltagerated device with lower RDS (ON) is useful
for improving the conversion efficiency. Referring to (8)–
(10), the rate of change of iL, iLp and iLs is given by
C. Mode 3 (t2 − t3) [Fig. 4(c)]
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switch-voltage stress (vDS) can be calculated(11),and (22)
as
Where d is the duty cycle of the main switch (S).
Continuously, the main switch (S) is turned ON at time t =
t4 to begin the next switching cycle.
By analyzing (24), the switch-voltage stress (vDS)
is not related to the dc-input voltage (Vi) and duty cycle (d)
if the values of the output voltage (Vo) and the turns ratio
(n) are fixed. Thus, it can ensure that the sustainable voltage
of the main switch (S) is constant. As long as the dc-input
voltage is not higher than the rated voltage of the main
switch, the high-efficiency voltage clamped dc–dc converter
can be applied well to the low-voltage power sources even
with large voltage variations, e.g., fuel cell, solar cell, etc.
Fuel-cell generation systems have been receiving
more attention in the last years due to the advantages of
high-conversion efficiency, low aggression to the
environment, no moving parts, and superior reliability and
At time t = t2, the residual energy of the clamped capacitor durability. Owing to the electrochemical reaction, fuel cell
(Cc) is discharged entirely, i.e., iCc (t2) = 0. Immediately, has the power quality of low voltage and high current.
the clamped capacitor (Cc) is charged by the energy of the However, the fuel-cell stack with high output voltage is
additional inductor (L) through the transformer, and the rate difficult to fabricate and it may be failure when any single
of change of the clamped-capacitor current (iCc) can be cell is inactive. Besides, the output voltage is varied easily
denoted as Moreover, the stored energy of the additional with respect to the load variations. In order to satisfy the
inductor (L) is released continuously to the output terminal requirement of high-voltage demand, a stable boost
by way of the transformer. The rate of charge of iDo is converter with high voltage gain and superior conversion
given by efficiency is necessary to utilize the fuel-cell energy more
efficiently. The validity of the proposed converter is verified
by the following experimental results via an example of a
PEMFC power source.
III. EXPERIMENTAL RESULTS
In order to verify the effectiveness of the designed
converter topology, the clean energy of a PEMFC system is
utilized for the low-voltage power source in the proposed
D. Mode 4 (t3 − t4) [Fig. 4(d)] high-efficiency voltage-clamped dc–dc converter, and its
At time t = t3, the clamped-capacitor current (iCc ) application circuit is depicted in Fig. 5. The PEMFC system
equals to the secondary-side current (iLs ) of the used in this study is the PowerPEMTM-PS250
transformer, and the output diode current (iDo ) decays to 0, manufactured by the H power Company. It is a dc power
i.e., iDo (t3) = 0. During this period, the voltage of the source with 250-W dc nominal power rating.
output diode (vDo ) Maintains the zero status until the main The system operates on an ambient air and clean
switch (S) is turned ON. Moreover, the magnitude of the pressurized hydrogen fuel. The fuel-cell system consists of a
additional inductor current (iL) is equal to the one of the (40) cell stack of the PEM type, mechanical auxiliaries, and
primary-side current (iLp ). According to (13) and (14), the electronic control module. In experimentation, the high-
rate of change of iLp and iLs can be represented as Since the efficiency voltage-clamped dc–dc converter is designed to
secondary leakage inductor (Lk) and the change rate of iLs operate from the fuel-cell variability dc input, Vi = 27−37.5
in the transformer are very small, the voltage of the V, to deliver a constant dc output, Vo = 200 V, with the
secondary leakage inductor (vLk ) can be neglected. maximal capability of output power, Po,max = 330 W. If the
According to the concept of the zero average voltage across maximal value of main switch voltage (vDS) is arranged for
the inductor over one period [4], the voltages of vCs , VCc , clamping at 50 V, the turns ratio can be determined as n =
and Vo for steady state operation can be described via (2), (2Vo/vDS(max)) − 2 = 6 according to (24). As can be seen
(4), (8), and (10) as. from Figs. 3 and 4, the voltage stress of the output diode
Since the voltage difference may be caused by the (vDo ) is the same as the switch-voltage stress. In addition,
secondary inductor of the transformer, as d = 0.5, the major the voltage stresses of rectifier diodes (vD1, vD2, vD3, and
function of the balanced capacitor (Cc) is used for keeping vD4) can be calculated via (21) and (23) as nvDS/2 = 150 V.
the cutoff voltages of the rectifier diodes (D1, D2, D3, and For conservative consideration, the main switch (FQI90N08,
D4) balanced. Moreover, it also can avoid the overlarge 80 V), the output diode (Schottky diode SR20100, 100 V),
current that passed through the rectifier diodes. According to and the rectifier diodes (Schottky diode SR20200, 200 V)
(22), the voltage gain can be tuned by regulating the turn’s are adopted in the experimental converter.
ratio (n) in the transformer to overcome the boost- ratio In order to solve the problem of the fuel-cell output voltage
limitation of the conventional converter. In addition, the varied with the variations of loads, the proposed converter
with dc-voltage feedback control is utilized to ensure the
system stability, and a PWM control IC TL494 is adopted to
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5. International Journal of Modern Engineering Research (IJMER)
www.ijmer.com Vol.2, Issue.6, Nov-Dec. 2012 pp-4273-4279 ISSN: 2249-6645
achieve this goal of feedback control. The prototype with According to Fig. 10, the converter output voltage, Vo = 200
the following V, is insensitive to the variation of loads due to the closed-
Specifications are designed in this section to loop control, and the output current ripple is also slightly
illustrate the design procedure given in Section II: extreme as a result of the high switching frequency. Fig. 11
Switching frequency fs = 100 kHz; summarizes the conversion efficiency of the proposed
Turns ratio n = 6; converter and the PEMFC output voltage under different
Additional inductor L = 5.9 μH; output powers. From the experimental results, the measure
Primary inductor of transformer Lp = 213.6 μH of efficiency of the proposed converter operating at 310-W
Secondary inductor of transformer Ls = 7689.6 μH; output power is 95.6%, and the maximal efficiency is 96.5%
Secondary leakage inductor Lk = 0.6 μH; at 190-W output power. The above experimental results
Balanced capacitor Cs = 4× 6.8 μF; agree well with those obtained from the design procedure
Clamped capacitor Cc = 6× 4.7 μF; given in Section II. However, slight differences in these
Input filter capacitor Ci = 3300 μF; results are attributed to the factor of system uncertainties in
Output filter capacitor Co = 3× 4.7 μF; practical applications.
Main switch S: FQI90N08 (80 V,
RDS (ON) = 16 mΩ);
Output diode Do: Schottky diode
SR20100 (100 V, 20 A);
Rectifier diodes D1, D2, D3, D4:
Scotty diode SR20200 (200 V, 20 A).
Fig. 5 depicts the experimental voltage and current
curves of the main switch (S) at 310-W output power. As
can be seen from this figure, the shaken switch voltage at
the beginning is caused by the line inductor when the switch Fig 5 (a)output voltage
is turned OFF. Fortunately, the steady state of this switch-
voltage stress is about 50 V due to the utilization of voltage-
clamped technique, and it is much smaller than the output
voltage, Vo = 200 V. It has the merit of selecting a low-
voltage-rated device in order to reduce the conduction loss
of the switch.
The experimental current waveforms of the
additional inductor (L), in parallel with the transformer,
primary inductor of transformer (Lp), and secondary
inductor of transformer (Ls) at 310-W output power, are
depicted in Fig. 5(c). By observing the currents of iLp and
Fig 5 (b)output current:
iLs, it is obvious that the transformer is manipulated during
the four-quadrant operation so that the utility rate of the
magnetic core is improved to exhibit the transformer
characteristics completely. The experimental voltage and
current responses of the diodes (Do, D3, and D4) at 310-W
output power are depicted in Fig. 5. From these results, the
reverse-recovery currents in these diodes are small to give
the credit to the utilization of Schottky diodes with
extremely low switching and conduction losses. Thus, it can
alleviate the reverse-recovery problem for further raising the
conversion efficiency. As can been seen from Fig. 5(a) and Fig 5 (c) clamped capacitor voltage
(b),
The balanced capacitor (Cs) can be used for
balancing the current and cutoff voltage of the diodes (D3
and D4) when the condition of d _= 0.5 holds. For verifying
the voltage-clamped property, the experimental voltage
responses of the output voltage (Vo), clamped capacitor
(Cc), output diode (Do), and main switch (S) at 310-W
output power are depicted. As can be seen from this figure,
the output voltage, Vo = 200 V, is strode mainly across the
clamped capacitor in the secondary-side circuit (i.e., VCc =
150 V). Thus, the switch-voltage stress and the cutoff
voltage of the output diode are clamped at about 50 V. In Fig 5 (d) clamped capacitor current
order to examine the robust performance of the proposed
converter scheme, the experimental results of the converter
output voltage (Vo), output current (Io), and the PEMFC
output current (Ii) under the step load variation between no
load (0 W) and full load (310 W) are depicted Fig. 10.
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6. International Journal of Modern Engineering Research (IJMER)
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[4] N. Mohan, T. M. Undeland, and W. P. Robbins, Power
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The authors would like to express their gratitude to [15] M. W. Ellis, M. R. Von Spakovsky, and D. J. Nelson,
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7. International Journal of Modern Engineering Research (IJMER)
www.ijmer.com Vol.2, Issue.6, Nov-Dec. 2012 pp-4273-4279 ISSN: 2249-6645
Dharamalla.ChandraSekhar- was
born in Andhra Pradesh, INDIA in 1982. He received the
B.Tech degree from JNTU Hyderabad in 2004 and M.Tech
degree in Power Electronics from JNTU Hyderabad in
2010.
Since July 2004-Sept 2008 he has been Assistant Professor
in the Department of Electrical and Electronics in Hi-Tech
Engineering College. From October-2008 he was been
working as a Head of Department of Electrical and
Electronics Engineering in GATE Engineering College,
JNTUH, AP. His areas of interest are Electrical Machines,
Power Electronics and Drives, Control Systems and
Electrical Circuits.
D Jagan - was born in Andhra Pradesh,
INDIA in 1988. He received the B.Tech degree from JNTU
Hyderabad in 2010, the M.Tech degree in Power Electronics
from JNTU Ananthapur I n 2012.
Since July 2010-Oct 2012 he has been Assistant Professor in
the Department of Electrical and Electronics in GATE
Engineering College, JNTUH, and AP. His areas of interest
are Electrical Machines, Power Electronics and Drives,
Control Systems and Electrical Circuits.
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