In this paper a voltage quadrupler dc-dc converter with coupled inductor
and π filter is presented. The use of the coupled inductor reduces the high
leakage inductance which is present in a transformer enabled converter.
The output ripples in the converter is reduced by providing a π filter.
The interleaved voltage quadrupler is used in this system in order to boost the
output voltage. The voltage multiplier improves the output voltage gain.
The main advantage of this system is more voltage gain when compared with
the transformer eneabled circuit and the overall efficiency of the system is
improved. The circuit is simple to control. As a final point of this research,
the simulation and the hardware investigational results are presented to
demonstrate the effectiveness of this proposed converter.
High gain dc-dc step up converters have been used in renewable energy systems, for example, photovoltaic grid connected system and fuel cell power plant to step up the low level dc voltage to a high level dc bus voltage. If the conventional boost converter is to meet this demand, it should be operated at an extreme duty cycle (duty cycle closes to unity), which will cause electromagnetic interference, reverse recovery problem and conduction loss at the power switches. This paper proposes a class of non-isolated dc-dc step up converters which provide very high voltage gain at a small duty cycle (duty cycle < 0.5). Firstly, the converter topologies are derived based on active switched inductor network and combination of active and passive switched inductor networks; secondly, the modes of operation of proposed active switched inductor converter and combined active and passive switched inductor converter are illustrated; thirdly, the performance of the proposed converters are analyzed mathematically in details and compared with conventional boost converter. Finally, the analysis is verified by simulation results.
Interleaved Boost Converter with Cumulative Voltage Unitpaperpublications3
Abstract: A boost converter is a DC to DC converter with an output voltage greater than the source voltage. But it produces large input current ripple. In order to improve the efficiency of the boost converter and reduce the ripple current, an interleaved boost converter is used. An interleaved boost converter consists of several boost converters connected in parallel with switching frequency and a phase shift of 180˚. A new interleaved high step-up DC-DC converter with the circuit of cumulative voltage unit (CVU) is presented in this work. This converter is suitable for the high gain applications. Only two switches are required to form the boosting path and the interleaved topology. Each CVU module can share common diodes to reduce the number of the components and step up the voltage gain. The interleaved structure in the input end can reduce the power loss in each current-owing component and the input current ripple. The interleaved boost converter with voltage summation unit can be verified by using MATLAB/SIMULINK.
Keywords: Cumulative voltage unit, Boost converter, Interleaved boost converter, Voltage Stress.
Title: Interleaved Boost Converter with Cumulative Voltage Unit
Author: Shyma H, Prof. Smitha Paulose, Prof. Leela Salim
ISSN 2349-7815
International Journal of Recent Research in Electrical and Electronics Engineering (IJRREEE)
Paper Publications
International Journal of Engineering Research and DevelopmentIJERD Editor
Electrical, Electronics and Computer Engineering,
Information Engineering and Technology,
Mechanical, Industrial and Manufacturing Engineering,
Automation and Mechatronics Engineering,
Material and Chemical Engineering,
Civil and Architecture Engineering,
Biotechnology and Bio Engineering,
Environmental Engineering,
Petroleum and Mining Engineering,
Marine and Agriculture engineering,
Aerospace Engineering.
International Journal of Engineering Research and Applications (IJERA) aims to cover the latest outstanding developments in the field of all Engineering Technologies & science.
International Journal of Engineering Research and Applications (IJERA) is a team of researchers not publication services or private publications running the journals for monetary benefits, we are association of scientists and academia who focus only on supporting authors who want to publish their work. The articles published in our journal can be accessed online, all the articles will be archived for real time access.
Our journal system primarily aims to bring out the research talent and the works done by sciaentists, academia, engineers, practitioners, scholars, post graduate students of engineering and science. This journal aims to cover the scientific research in a broader sense and not publishing a niche area of research facilitating researchers from various verticals to publish their papers. It is also aimed to provide a platform for the researchers to publish in a shorter of time, enabling them to continue further All articles published are freely available to scientific researchers in the Government agencies,educators and the general public. We are taking serious efforts to promote our journal across the globe in various ways, we are sure that our journal will act as a scientific platform for all researchers to publish their works online.
High gain dc-dc step up converters have been used in renewable energy systems, for example, photovoltaic grid connected system and fuel cell power plant to step up the low level dc voltage to a high level dc bus voltage. If the conventional boost converter is to meet this demand, it should be operated at an extreme duty cycle (duty cycle closes to unity), which will cause electromagnetic interference, reverse recovery problem and conduction loss at the power switches. This paper proposes a class of non-isolated dc-dc step up converters which provide very high voltage gain at a small duty cycle (duty cycle < 0.5). Firstly, the converter topologies are derived based on active switched inductor network and combination of active and passive switched inductor networks; secondly, the modes of operation of proposed active switched inductor converter and combined active and passive switched inductor converter are illustrated; thirdly, the performance of the proposed converters are analyzed mathematically in details and compared with conventional boost converter. Finally, the analysis is verified by simulation results.
Interleaved Boost Converter with Cumulative Voltage Unitpaperpublications3
Abstract: A boost converter is a DC to DC converter with an output voltage greater than the source voltage. But it produces large input current ripple. In order to improve the efficiency of the boost converter and reduce the ripple current, an interleaved boost converter is used. An interleaved boost converter consists of several boost converters connected in parallel with switching frequency and a phase shift of 180˚. A new interleaved high step-up DC-DC converter with the circuit of cumulative voltage unit (CVU) is presented in this work. This converter is suitable for the high gain applications. Only two switches are required to form the boosting path and the interleaved topology. Each CVU module can share common diodes to reduce the number of the components and step up the voltage gain. The interleaved structure in the input end can reduce the power loss in each current-owing component and the input current ripple. The interleaved boost converter with voltage summation unit can be verified by using MATLAB/SIMULINK.
Keywords: Cumulative voltage unit, Boost converter, Interleaved boost converter, Voltage Stress.
Title: Interleaved Boost Converter with Cumulative Voltage Unit
Author: Shyma H, Prof. Smitha Paulose, Prof. Leela Salim
ISSN 2349-7815
International Journal of Recent Research in Electrical and Electronics Engineering (IJRREEE)
Paper Publications
International Journal of Engineering Research and DevelopmentIJERD Editor
Electrical, Electronics and Computer Engineering,
Information Engineering and Technology,
Mechanical, Industrial and Manufacturing Engineering,
Automation and Mechatronics Engineering,
Material and Chemical Engineering,
Civil and Architecture Engineering,
Biotechnology and Bio Engineering,
Environmental Engineering,
Petroleum and Mining Engineering,
Marine and Agriculture engineering,
Aerospace Engineering.
International Journal of Engineering Research and Applications (IJERA) aims to cover the latest outstanding developments in the field of all Engineering Technologies & science.
International Journal of Engineering Research and Applications (IJERA) is a team of researchers not publication services or private publications running the journals for monetary benefits, we are association of scientists and academia who focus only on supporting authors who want to publish their work. The articles published in our journal can be accessed online, all the articles will be archived for real time access.
Our journal system primarily aims to bring out the research talent and the works done by sciaentists, academia, engineers, practitioners, scholars, post graduate students of engineering and science. This journal aims to cover the scientific research in a broader sense and not publishing a niche area of research facilitating researchers from various verticals to publish their papers. It is also aimed to provide a platform for the researchers to publish in a shorter of time, enabling them to continue further All articles published are freely available to scientific researchers in the Government agencies,educators and the general public. We are taking serious efforts to promote our journal across the globe in various ways, we are sure that our journal will act as a scientific platform for all researchers to publish their works online.
Hardware Implementation of Solar Based Boost to SEPIC Converter Fed Nine Leve...IJPEDS-IAES
Multi level inverters are widely used in high power applications because of
low harmonic distortion. This paper deals with the simulation
and implementation of PV based boost to SEPIC converter with multilevel
inverter. The output of PV system is stepped up using boost to sepic
converter and it is converted into AC using a multilevel inverter.
The simulation and experimental results with the R load is presented in this
paper. The FFT analysis is done and the THD values are compared. Boost to
SEPIC converter is proposed to step up the voltage to the required value. The
experimental results are compared with the simulation results. The results
indicate that nine level inverter system has better performance than seven
level inverter system.
Modeling and Analysis of Transformerless High Gain Buck-boost DC-DC ConvertersIAES-IJPEDS
This paper proposes a transfomerless switched capacitor buck boost converter model, which provides higher voltage gain and higher efficiency when compared to the conventional buck boost converter. The averaged model based on state- space description is analyzed in the paper. The simulation results are presented to confirm the capability of the converter to generate high voltage ratios. The comparison between the proposed model and the traditional model is also provided to reveal the improvement. The proposed converter is suitable for for a wide application which requires high step-up DC-DC converters such as DC micro-grids and solar electrical energy.
IEEE 2015-15 Power Electronics and Power System Project titles for ME and BE Students,Bangalore.power electronics and power system projects in bangalore.
This project is proposed to integrate the Fuel cell emulator with a boost converter and load the DC motor
and the performance analysis is done. Fuel cell as a renewable energy source is considered to be one of the most
promising sources of electrical power. The characteristics of fuel cell is such that the DC power extracted from it is
at low voltage level, this project proposes a prototype of a new power electronics based fuel cell emulator. After
proposing a fuel cell emulator, it is integrated with a boost converter and DC motor is loaded. After the successful
working of the boost converter, it can be directly connected with the actual Fuel Cell Systems (FCS) to satisfy the
DC motor load which is integrated with fuel cell emulator and boost converter.
Various Resonant Converters for high voltage and high power applications have been designed. Different Topologies of LLC, LCC, and CLL Resonant Converters have been simulated and compared for the same input voltage. The simulation was done at a very high frequency. The Output Power and the Efficiency of all the three Resonant Converters were calculated.With the results, it has been proved that LCC Resonant Converters were very much suited to give an output voltage of around 62 Kilovolts with a output power of 20 kilowatts.
High Efficiency Dc-Dc Converter for Renewable Energy Applications and High Vo...IOSRJEEE
Renewable sources like solar PV cell is prefer to be operated at low voltages. This paper proposes a novel high voltage gain, high efficiency dc-dc converter based on coupled inductor, intermediate capacitor. The input energy acquired from the source is first stored in the coupled inductor and intermediate capacitor in a lossless manner. Improve the voltage gain and efficiency of the system. Exorbitant duty cycle values are not required for high voltage gain, when prevent the problems such as diode reverse recovery. Presence of a passive clamp network causes reduced voltage stress on the switch. Overall performance of the renewable energy with a step-up DC/DC converter using closed loop control action is used in the proposed system, improving the overall efficiency of the system.
Single Phase Matrix Converter for Input Power Factor Improvementiosrjce
IOSR Journal of Electrical and Electronics Engineering(IOSR-JEEE) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of electrical and electronics engineering and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in electrical and electronics engineering. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Brushless DC motor is a synchronous machine that makes use of electronic commutation instead of mechanical commutator. Brushless DC motors makes use of inverter encompassing static switches for its operation. A simple bridge converter when used for BLDC drive as front end converter makes input source power factor to get reduced which is unacceptable in the power system. To avoid the distortions in the source voltage and source currents, Buck converter which was used as power factor correction (PFC) converter in this paper to improve the power factor. Presence of power electronic converters deteriorates system power factor effecting overall system performance. This paper presents buck converter for power factor correction in brushless DC motor drive system. Buck converter is operated with current control strategy rather to conventional voltage follower control. Simulation model was obtained using MATLAB/SIMULINK software and the brushless DC motor performance characteristics were shown for conditions with different DC link voltages and step variation in DC link voltage. Total harmonic distortion in source current was also presented.
Push-Pull Converter Fed Three-Phase Inverter for Residential and Motor LoadIJPEDS-IAES
The proposed paper is an new approach for power conditioning of a PV
(photo-voltaic) cell array. The main objective is to investigate an approach to
provide and improve the delivered electric energy by means of power
conditioning structures with the use of alternative renewable resources
(ARRs) for remote rural residential or industrial non-linear loads. This
approach employs a series-combined connected boost and buck boost DCDC
converter for power conditioning of the dc voltage provided by a photovoltaic
array. The input voltage to the combined converters is 100 V
provided from two series connected PV cells, which is converted and
increased to 200 V at the dc output voltage. Series-combined connected
boost and buck-boost DC-DC converters operate alternatively. This helps to
reduce the input ripple current and provide the required 400 Vdc on a
sinusoidal PWM three-phase inverter. Analysis of the two series-combined
DC-DC converters is presented along with simulation results. Simulations of
the series-combined DC-DC converters are presented with an output DC
voltage of 200 V and a maximum output load of Po=600 W.
Design and analysis of boost converter with cld celleSAT Journals
Abstract
In this paper, the output voltage in renewable energy sources is improved by using DC-DC converter topology. Basically Boost
converter is used for improving the voltage gain. In this converter switching frequency is limited, hence the output voltage is
reduced. To overcome this issue, by using the boost converter with CLD cell is proposed .In this proposed paper for comparing
the voltage stress and efficiency by using two converters topology. For the duty ratio of 0.5 the output voltage is compared with
the conventional boost converter.
Keywords- Boost Converter, Boost Converter with CLD, Voltage Stress
A Comparative Study of Various AC-DC Converters for Low Voltage Energy Harves...paperpublications3
Abstract: Electromagnetic microscale and mesoscale power generators with low voltage outputs are now widely used as kinetic energy harvesters. The extrinsic vibrations on the generator can excite the internal oscillations between the proof mass magnet and the electrical damper coils. These oscillations produce a periodically varying magnetic flux in coil, inducing a corresponding AC output voltage. This output can be converted to dc and can be used to supply power to electronic loads. The conventional AC-DC converters for energy harvesting system with diode rectifiers suffer considerable voltage drop resulting increase in power loss of circuitry and complexity. As a remedy various bridgeless boost converters were designed and implemented. Standard H bridge converter with 4 switch or 2 switch, dual polarity boost converters, parallel combination of boost and buck-boost converter, integrated boost and buck-boost combination bridgeless rectifier are some of these. These circuits are studied, simulated and compared. The simulation models are drawn and simulated using MATLAB R2010a.
Recently, Re-boost seven-level inverter has been developed as an alternative between Photovoltaic system and single-phase load. DC level is increased using a re-boost regulator and its output is rehabilitated into single-phase AC utilizing a seven-level inverter. The re-boost converter is utilized to escalate the voltage gain. The objective of the suggested closed loop Re-boost Seven Level Inverter fed Induction Motor (RBSLIIM) system is to enhance the dynamic response of RBSLIIM using FO-P-I-D controller. Simulink models are developed for P-I and FO-P-I-D controlled RBSLIIM systems. The results of P-I and FO-P-I-D based RBSLIIM systems indicate that the voltage response with FO-P-I-D is superior to P-I controlled RBSLIIM system.
This paper presented single DC bus single phase seven level cascaded H-bridge (CHB) inverter for multi-panel photovoltaic grid-connected applications. A single DC bus supplying flyback converters to produce DC link voltages for CHB cells is suggested. A balanced operation of CHB inverter cells is obtained irrespective to power unbalance occurred by individual maximum power point tracking boost converter of photovoltaic (PV) panels due to the non-uniform irradiation and partial shading. A DC bus voltage control system with addition of estimated DC bus ripple voltage to the reference is proposed to eliminate the second order harmonic contained in the feedback voltage of DC bus enabling to design high bandwidth of DC voltage control loop. This produces fast dynamic response, low total harmonic distortion (THD) of grid current and smaller DC bus capacitance. Mathematical modeling of bus voltage control system is presented. PSIM simulation program is used and the simulation results are obtained to validate the proposed control system.
Development of a Novel Three Phase Grid-Tied Multilevel Inverter TopologyIAES-IJPEDS
The conventional line-commutated ac-to-dc converters/ inverters have square-shaped line current. It contains higher-order harmonics which generates EMI and it causes more heating of the core of distribution or power transformers. PWM based inverters using MOSFET/IGBT have higher switching losses, and the power handling capability and reliability are quite low in comparison to thyristors/ SCR. A thyristor based forced commutated inverters are not suitable for PWM applications due to the problems of commutation circuits. A pure sinusoidal voltage output or waveform with low harmonic contents is most desirable for ac load using dc to ac conversion. This paper presents a new multilevel inverter topology in which three phase ac- to-dc converter circuits are used in inversion mode by controlling the switching angle. Due to natural commutation, no separate circuit is required for synchronization. In this paper simulation and analysis are done for grid-tied three-phase 6-pulse, Two three-phase, 3-pulse and 12-pulse converter. These converters are analysed for different battery voltage and different switching angle combinations in order to reduce the total harmonic distortion (THD). Three-phase harmonic filters are further added to the grid side to reduce the harmonic content in the line current. A comparative study of these converters is also presented in this paper.
Application of single phase matrix converter topology to an uninterruptible p...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
This paper presents the simulation design of dc/dc interleaved boost converter with zero-voltage switching (ZVS). By employin the interleaved structure, the input current stresses to switching devices were reduced and this signified to a switching conduction loss reduction. All the parameters had been calculated theoretically. The proposed converter circuit was simulated by using MATLAB/Simulink and PSpice software programmes. The converter circuit model, with specifications of output power of 200 W, input voltage range from 10~60 V, and operates at 100 kHz switching frequency was simulated to validate the designed parameters. The results showed that the main switches of the model converter circuit achieved ZVS conditions during the interleaving operation. Consequently, the switching losses in the main switching devices were reduced. Thus, the proposed converter circuit model offers advantages of input current stress and switching loss reductions. Hence, based on the designed parameters and results, the converter model can be extended for hardware implementation.
A High Step Up Hybrid Switch Converter Connected With PV Array For High Volt...ijitjournal
T
his paper
presents
a
ste
p up DC
-
to
-
DC converter with
hybrid switch capacitor technique having
high
voltage conversion ratio with small
switch voltage stress
. The converter is suitable for the applications
where high voltage conversion is required. The proposed
DC
-
DC converter
has low voltage ratted
MOSFET switch and is connected to PV array to get high output voltage at small duty ratios.
Hence it has
high efficiency.
The principles of operations and the theoretical analysis are presented in this paper.
All the
simulations are
done in MATLAB
-
SIMULINK Environment and
results were obtained with voltage
conversion ratio of 4.
Hardware Implementation of Solar Based Boost to SEPIC Converter Fed Nine Leve...IJPEDS-IAES
Multi level inverters are widely used in high power applications because of
low harmonic distortion. This paper deals with the simulation
and implementation of PV based boost to SEPIC converter with multilevel
inverter. The output of PV system is stepped up using boost to sepic
converter and it is converted into AC using a multilevel inverter.
The simulation and experimental results with the R load is presented in this
paper. The FFT analysis is done and the THD values are compared. Boost to
SEPIC converter is proposed to step up the voltage to the required value. The
experimental results are compared with the simulation results. The results
indicate that nine level inverter system has better performance than seven
level inverter system.
Modeling and Analysis of Transformerless High Gain Buck-boost DC-DC ConvertersIAES-IJPEDS
This paper proposes a transfomerless switched capacitor buck boost converter model, which provides higher voltage gain and higher efficiency when compared to the conventional buck boost converter. The averaged model based on state- space description is analyzed in the paper. The simulation results are presented to confirm the capability of the converter to generate high voltage ratios. The comparison between the proposed model and the traditional model is also provided to reveal the improvement. The proposed converter is suitable for for a wide application which requires high step-up DC-DC converters such as DC micro-grids and solar electrical energy.
IEEE 2015-15 Power Electronics and Power System Project titles for ME and BE Students,Bangalore.power electronics and power system projects in bangalore.
This project is proposed to integrate the Fuel cell emulator with a boost converter and load the DC motor
and the performance analysis is done. Fuel cell as a renewable energy source is considered to be one of the most
promising sources of electrical power. The characteristics of fuel cell is such that the DC power extracted from it is
at low voltage level, this project proposes a prototype of a new power electronics based fuel cell emulator. After
proposing a fuel cell emulator, it is integrated with a boost converter and DC motor is loaded. After the successful
working of the boost converter, it can be directly connected with the actual Fuel Cell Systems (FCS) to satisfy the
DC motor load which is integrated with fuel cell emulator and boost converter.
Various Resonant Converters for high voltage and high power applications have been designed. Different Topologies of LLC, LCC, and CLL Resonant Converters have been simulated and compared for the same input voltage. The simulation was done at a very high frequency. The Output Power and the Efficiency of all the three Resonant Converters were calculated.With the results, it has been proved that LCC Resonant Converters were very much suited to give an output voltage of around 62 Kilovolts with a output power of 20 kilowatts.
High Efficiency Dc-Dc Converter for Renewable Energy Applications and High Vo...IOSRJEEE
Renewable sources like solar PV cell is prefer to be operated at low voltages. This paper proposes a novel high voltage gain, high efficiency dc-dc converter based on coupled inductor, intermediate capacitor. The input energy acquired from the source is first stored in the coupled inductor and intermediate capacitor in a lossless manner. Improve the voltage gain and efficiency of the system. Exorbitant duty cycle values are not required for high voltage gain, when prevent the problems such as diode reverse recovery. Presence of a passive clamp network causes reduced voltage stress on the switch. Overall performance of the renewable energy with a step-up DC/DC converter using closed loop control action is used in the proposed system, improving the overall efficiency of the system.
Single Phase Matrix Converter for Input Power Factor Improvementiosrjce
IOSR Journal of Electrical and Electronics Engineering(IOSR-JEEE) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of electrical and electronics engineering and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in electrical and electronics engineering. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Brushless DC motor is a synchronous machine that makes use of electronic commutation instead of mechanical commutator. Brushless DC motors makes use of inverter encompassing static switches for its operation. A simple bridge converter when used for BLDC drive as front end converter makes input source power factor to get reduced which is unacceptable in the power system. To avoid the distortions in the source voltage and source currents, Buck converter which was used as power factor correction (PFC) converter in this paper to improve the power factor. Presence of power electronic converters deteriorates system power factor effecting overall system performance. This paper presents buck converter for power factor correction in brushless DC motor drive system. Buck converter is operated with current control strategy rather to conventional voltage follower control. Simulation model was obtained using MATLAB/SIMULINK software and the brushless DC motor performance characteristics were shown for conditions with different DC link voltages and step variation in DC link voltage. Total harmonic distortion in source current was also presented.
Push-Pull Converter Fed Three-Phase Inverter for Residential and Motor LoadIJPEDS-IAES
The proposed paper is an new approach for power conditioning of a PV
(photo-voltaic) cell array. The main objective is to investigate an approach to
provide and improve the delivered electric energy by means of power
conditioning structures with the use of alternative renewable resources
(ARRs) for remote rural residential or industrial non-linear loads. This
approach employs a series-combined connected boost and buck boost DCDC
converter for power conditioning of the dc voltage provided by a photovoltaic
array. The input voltage to the combined converters is 100 V
provided from two series connected PV cells, which is converted and
increased to 200 V at the dc output voltage. Series-combined connected
boost and buck-boost DC-DC converters operate alternatively. This helps to
reduce the input ripple current and provide the required 400 Vdc on a
sinusoidal PWM three-phase inverter. Analysis of the two series-combined
DC-DC converters is presented along with simulation results. Simulations of
the series-combined DC-DC converters are presented with an output DC
voltage of 200 V and a maximum output load of Po=600 W.
Design and analysis of boost converter with cld celleSAT Journals
Abstract
In this paper, the output voltage in renewable energy sources is improved by using DC-DC converter topology. Basically Boost
converter is used for improving the voltage gain. In this converter switching frequency is limited, hence the output voltage is
reduced. To overcome this issue, by using the boost converter with CLD cell is proposed .In this proposed paper for comparing
the voltage stress and efficiency by using two converters topology. For the duty ratio of 0.5 the output voltage is compared with
the conventional boost converter.
Keywords- Boost Converter, Boost Converter with CLD, Voltage Stress
A Comparative Study of Various AC-DC Converters for Low Voltage Energy Harves...paperpublications3
Abstract: Electromagnetic microscale and mesoscale power generators with low voltage outputs are now widely used as kinetic energy harvesters. The extrinsic vibrations on the generator can excite the internal oscillations between the proof mass magnet and the electrical damper coils. These oscillations produce a periodically varying magnetic flux in coil, inducing a corresponding AC output voltage. This output can be converted to dc and can be used to supply power to electronic loads. The conventional AC-DC converters for energy harvesting system with diode rectifiers suffer considerable voltage drop resulting increase in power loss of circuitry and complexity. As a remedy various bridgeless boost converters were designed and implemented. Standard H bridge converter with 4 switch or 2 switch, dual polarity boost converters, parallel combination of boost and buck-boost converter, integrated boost and buck-boost combination bridgeless rectifier are some of these. These circuits are studied, simulated and compared. The simulation models are drawn and simulated using MATLAB R2010a.
Recently, Re-boost seven-level inverter has been developed as an alternative between Photovoltaic system and single-phase load. DC level is increased using a re-boost regulator and its output is rehabilitated into single-phase AC utilizing a seven-level inverter. The re-boost converter is utilized to escalate the voltage gain. The objective of the suggested closed loop Re-boost Seven Level Inverter fed Induction Motor (RBSLIIM) system is to enhance the dynamic response of RBSLIIM using FO-P-I-D controller. Simulink models are developed for P-I and FO-P-I-D controlled RBSLIIM systems. The results of P-I and FO-P-I-D based RBSLIIM systems indicate that the voltage response with FO-P-I-D is superior to P-I controlled RBSLIIM system.
This paper presented single DC bus single phase seven level cascaded H-bridge (CHB) inverter for multi-panel photovoltaic grid-connected applications. A single DC bus supplying flyback converters to produce DC link voltages for CHB cells is suggested. A balanced operation of CHB inverter cells is obtained irrespective to power unbalance occurred by individual maximum power point tracking boost converter of photovoltaic (PV) panels due to the non-uniform irradiation and partial shading. A DC bus voltage control system with addition of estimated DC bus ripple voltage to the reference is proposed to eliminate the second order harmonic contained in the feedback voltage of DC bus enabling to design high bandwidth of DC voltage control loop. This produces fast dynamic response, low total harmonic distortion (THD) of grid current and smaller DC bus capacitance. Mathematical modeling of bus voltage control system is presented. PSIM simulation program is used and the simulation results are obtained to validate the proposed control system.
Development of a Novel Three Phase Grid-Tied Multilevel Inverter TopologyIAES-IJPEDS
The conventional line-commutated ac-to-dc converters/ inverters have square-shaped line current. It contains higher-order harmonics which generates EMI and it causes more heating of the core of distribution or power transformers. PWM based inverters using MOSFET/IGBT have higher switching losses, and the power handling capability and reliability are quite low in comparison to thyristors/ SCR. A thyristor based forced commutated inverters are not suitable for PWM applications due to the problems of commutation circuits. A pure sinusoidal voltage output or waveform with low harmonic contents is most desirable for ac load using dc to ac conversion. This paper presents a new multilevel inverter topology in which three phase ac- to-dc converter circuits are used in inversion mode by controlling the switching angle. Due to natural commutation, no separate circuit is required for synchronization. In this paper simulation and analysis are done for grid-tied three-phase 6-pulse, Two three-phase, 3-pulse and 12-pulse converter. These converters are analysed for different battery voltage and different switching angle combinations in order to reduce the total harmonic distortion (THD). Three-phase harmonic filters are further added to the grid side to reduce the harmonic content in the line current. A comparative study of these converters is also presented in this paper.
Application of single phase matrix converter topology to an uninterruptible p...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
This paper presents the simulation design of dc/dc interleaved boost converter with zero-voltage switching (ZVS). By employin the interleaved structure, the input current stresses to switching devices were reduced and this signified to a switching conduction loss reduction. All the parameters had been calculated theoretically. The proposed converter circuit was simulated by using MATLAB/Simulink and PSpice software programmes. The converter circuit model, with specifications of output power of 200 W, input voltage range from 10~60 V, and operates at 100 kHz switching frequency was simulated to validate the designed parameters. The results showed that the main switches of the model converter circuit achieved ZVS conditions during the interleaving operation. Consequently, the switching losses in the main switching devices were reduced. Thus, the proposed converter circuit model offers advantages of input current stress and switching loss reductions. Hence, based on the designed parameters and results, the converter model can be extended for hardware implementation.
A High Step Up Hybrid Switch Converter Connected With PV Array For High Volt...ijitjournal
T
his paper
presents
a
ste
p up DC
-
to
-
DC converter with
hybrid switch capacitor technique having
high
voltage conversion ratio with small
switch voltage stress
. The converter is suitable for the applications
where high voltage conversion is required. The proposed
DC
-
DC converter
has low voltage ratted
MOSFET switch and is connected to PV array to get high output voltage at small duty ratios.
Hence it has
high efficiency.
The principles of operations and the theoretical analysis are presented in this paper.
All the
simulations are
done in MATLAB
-
SIMULINK Environment and
results were obtained with voltage
conversion ratio of 4.
This paper presents a step up DC-to-DC converter with hybrid switch capacitor technique having high voltage conversion ratio with small switch voltage stress . The converter is suitable for the applications where high voltage conversion is required. The proposed DC-DC converter has low voltage ratted MOSFET switch and is connected to PV array to get high output voltage at small duty ratios. Hence it has high efficiency. The principles of operations and the theoretical analysis are presented in this paper. All the simulations are done in MATLAB- SIMULINK Environment and results were obtained with voltage conversion ratio of 4.9.
Design and Simulation of Efficient DC-DC Converter Topology for a Solar PV Mo...Sajin Ismail
Modulated Integrated Converter systems are considered to be the new and global turning point in the field of
Solar PV systems. These converters are highly recognised for its modular size and compact nature and they are supposed to
be attached directly with each PV module and since one PV module is having the power rating of a few watts ranging from
0-500Ws, the design rating would be in the same range and thus the most vital condition in such a design is efficiency
under these relatively low loads. In this paper an isolated interleaved boost converter topology is considered in the DC-DC
section and which is designed and simulated for a specific power rating (250W) and the efficiency is analysed with varying
load conditions and compared with the target efficiency of the system.
Modified Bidirectional Converter with Current Fed InverterIJPEDS-IAES
A bidirectional dc-dc converter with multiple outputs are concatenated with a
high frequency current source parallel resonant push pull inverter is
presented in this paper. The two outputs are added together and it is taken as
the input source for the inverter. The current source parallel resonant push
pull inverter implemented here with high frequency applications like
induction heating, Fluorescent lighting, Digital signal processing sonar. This
paper proposes a simple photovoltaic power system consists of a
bidirectional converter and a current fed inverter for regulating the load
variations. Solar power is used as the input source for the system. Simulation
of the proposed system is carried out in PSIM software and experimentally
verified the results.
This paper presents the improved single phase AC-DC super lift Luo converter for enhancing quality of power by mitigating the issues. The proposed converter is used for output voltage control, power factor improvement and reduced source current harmonics at supply side. The main intention of this work is to design appropriate closed loop controllers for this AC-DC super lift Luo converter to achieve unity power factor in the source end. The designed control system comprises of two control loops, voltage control in outer loop and the current controller is devised in the inner loop. Fuzzy controller is used for current controller whereas PI controller as voltage controller. In the MATLAB/SIMULINK platform, simulation of the proposed AC-DC super lift Luo converter is done. It is clear from the simulation results that PI integrated fuzzy controller for voltage and control is proven to be better than classical PI with hysteresis controllers. The proposed system is able to achieve high input power factor along with supply current harmonic distortions of less than 5%.
A Novel Three Phase Multi-string Multilevel Inverter with High DC-DC Closed o...rnvsubbarao koppineni
this inverter reduces
number power devices and high performances.
Before this inverter provide a high step up DC-DC
converter with PI controller for better conversion
efficiency and to improve the output dc voltage of
varies renewable energy sources. This multi-string
multilevel inverter consists of six switches only
instead of eight switches in cascaded H-bridge
multilevel inverter in order to reduce conversion
losses. The main objective of this paper is to save
cost and size by removing any kind of transformer
as well as reducing the power devices
Filter Based Solar Power Generation System with a Seven Level InverterIJMTST Journal
This paper proposes a new solar power generation system, which is composed of a DC/DC power converter and a new seven-level inverter. The DC/DC power converter integrates a DC-DC boost converter and a transformer to convert the output voltage of the solar cell array into two independent voltage sources with multiple relationships. This new seven-level inverter is configured using a capacitor selection circuit and a full-bridge power converter, connected in cascade. The capacitor selection circuit converts the two output voltage sources of DC-DC power converter into a three-level DC voltage and the full- bridge power converter further converts this three- level DC voltage into a seven-level AC voltage. In this way, the proposed solar power generation system generates a sinusoidal output current that is in phase with the utility voltage and is fed into the utility. The salient features of the proposed seven-level inverter are that only six power electronic switches are used and only one power electronic switch is switched at high frequency at any time. A prototype is developed and tested to verify the performance of this proposed solar power generation system.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
The papers for publication in The International Journal of Engineering& Science are selected through rigorous peer reviews to ensure originality, timeliness, relevance, and readability.
A new closed loop AC to DC ĈUK converter is presented in this paper. The conventional ĈUK AC to DC converter has no feedback circuit. Thereby, the output voltage of the converter changes while changing the load. The proposed closed loop converter can regulate voltage with the variation of load over a wide range. Moreover, the power factor and Total Harmonic Distortion (THD) of the supply side current found quite satisfactory from this closed loop ĈUK converter. The converter operates in four steps with a different combination of voltage polarities and switching states. The feedback path consists of a voltage control loop and a current control loop. The closed loop ĈUK converter in this study is compared with the open loop version. Additionally, the comparison is made with the conventional converter of the same topology. The effectiveness in terms of power factor and THD of the proposed converter is verified using simulation results.
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.
ZVZCS Based High Frequency Link Grid Connected SVM Applied Three Phase Three ...IAES-IJPEDS
This article proposes a newly proposed highly effective Zero Voltage and Zero Current switching based Front end converter with a High Frequency Transformer with a Three Phase Three Level Diode Clamped Inverter in photovoltaic applications. The switching scheme is implemented in MATLAB/ Simulink condition. ZVZCS condition is achieved. This type of converter shows high efficiency and very negligible switching loss. Finally ZVZCS based High Frequency Link Diode Clamped Inverter is connected to Grid. An MCI optimized Current controller is used with SVM switching technique. In This article, responses with three types of controllers (I, PI, PID) have been examined and compared. Simulation results show the effectiveness, and validity of this technique.
An Efficient High Gain DC-DC Converter for Automotive ApplicationsIJPEDS-IAES
This paper presents a high gain DC-DC converter which uses a clamp circuit
to achieve soft switching. The proposed converter is designed to supply a
high intensity discharge (HID) lamp used in automobile head lamps. The
converter operates from a 12V input supply and provides an output voltage
of 120V at 35W output power. A clamp circuit consisting of a clamp
capacitor, clamp switch and resonant inductor will help to achieve zero
voltage switching (ZVS) of the both main and clamp switches. The practical
performance of the converter was validated through experimental results.
Results obtained from the prototype hardware prove that the converter meets
the requirements of HID lamp application and can be a very good alternative
to existing converters.
Similar to Transformer Less Voltage Quadrupler Based DC-DC Converter with Coupled Inductor and PI Filter for Increased Voltage Gain and Efficiency (20)
Inter-Area Oscillation Damping using an STATCOM Based Hybrid Shunt Compensati...IJPEDS-IAES
FACTS devices are one of the latest technologies which have been used to
improve power system dynamic and stability during recent years. However,
widespread adoption of this technology has been hampered by high cost
and reliability concerns. In this paper an economical phase imbalanced shunt
reactive compensation concept has been introduced and its ability for power
system dynamic enhancement and inter-area oscillation damping are
investigated. A hybrid phase imbalanced scheme is a shunt capacitive
compensation scheme, where two phases are compensated by fixed shunt
capacitor (C) and the third phase is compensated by a Static Synchronous
Compensator (STATCOM) in shunt with a fixed capacitor (CC). The power
system dynamic stability enhancement would be achieved by adding
a conventional Wide Area Damping Controller (WADC) to the main control
loop of the single phase STATCOM. Two different control methodologies
are proposed: a non-optimized conventional damping controller
and a conventional damping controller with optomised parameters that are
added to the main control loop of the unbalanced compensator in order to
damp the inter area oscillations. The proposed arrangement would, certainly,
be economically attractive when compared with a full three-phase
STATCOM. The proposed scheme is prosperously applied in a 13-bus
six-machine test system and various case studies are conducted to
demonstrate its ability in damping inter-area oscillations and power system
dynamic enhancement.
Fuzzy Gain-Scheduling Proportional–Integral Control for Improving the Speed B...IJPEDS-IAES
In this article, we have set up a vector control law of induction machine
where we tried different type of speed controllers. Our control strategy is of
type Field Orientated Control (FOC). In this structure we designed a Fuzzy
Gain-Scheduling Proportional–Integral (Pi) controller to obtain best result
regarding the speed of induction machine. At the beginning we designed a Pi
controller with fixed parameters. We came up to these parameters by
identifying the transfer function of this controller to that of Broïda (second
order transfer function). Then we designed a fuzzy logic (FL) controller.
Based on simulation results, we highlight the performances of each
controller. To improve the speed behaviour of the induction machine, we
have designend a controller called “Fuzzy Gain-Scheduling Proportional–
Integral controller” (FGS-PI controller) which inherited the pros of the
aforementioned controllers. The simulation result of this controller will
strengthen its performances.
Advance Technology in Application of Four Leg Inverters to UPQCIJPEDS-IAES
This article presents a novel application of four leg inverter with
conventional Sinusoidal Pulse Width Modulation (SPWM) Scheme to
Unified Power Quality Conditioner (UPQC). The Power Quality problem
became burning issues since the starting of high voltage AC transmission
system. Hence, in this article it has been discussed to mitigate the PQ issues
in high voltage AC systems through a three phase Unified Power Quality
Conditioner (UPQC) under various conditions, such as harmonic mitigation
scheme, non linear loads, sag and swell conditions as well. Also, it proposes
to control harmoincs with various artificial intelligent techniques. Thus
application of these control technique such as Neural Networks (ANN)
Fuzzy Logic makes the system performance in par with the standards
and also compared with existing system. The simulation results based on
MATLAB/Simulink are discussed in detail to support the concept developed
in the paper.
Modified SVPWM Algorithm for 3-Level Inverter Fed DTC Induction Motor DriveIJPEDS-IAES
In this paper, a modified space vector pulse width modulation (MSVPWM)
algorithm is developed for 3-level inverter fed direct torque controlled
induction motor drive (DTC-IMD). MSVPWM algorithm simplifies
conventional space vector pulse width modulation (CSVPWM) algorithm for
multilevel inverter (MLI), whose complexity lies in sector/subsector/subsubsector
identification; which will commensurate with number of levels. In
the proposed algorithm sectors are identified as in two level inverter
and subsectors/sub-subsectors are identified by shifting the original reference
vector to sector 1 (S1). This is valid due to the fact that a three level space
vector plane is a composition of six two level space planes, and are
symmetrical with reference to six pivot states. Switching state/sequence
selection is also very important while dealing with SVPWM strategy for
MLI. In the proposed algorithm out of 27 available switching states apt
switching state is selected based on sector and subsector number, such that
voltage ripple is considerably less. To validate the proposed algorithm, it is
tested on a three level neutral point clamped (NPC) inverter fed DTC-IMD.
The performance of the MSVPWM algorithm is analyzed by comparing no
load stator current ripple of the three level DTC-IMD with two level
DTC-IMD. Significant reduction in steady state torque and flux ripple is
observed. Hence, reduced acoustic noise is a distinctive facet of the proposed
method.
Modelling of a 3-Phase Induction Motor under Open-Phase Fault Using Matlab/Si...IJPEDS-IAES
The d-q model of Induction Motors (IMs) has been effectively used as an
efficient method to analyze the performance of the induction machines. This
study presents a step by step Matlab/Simulink implementation
of a star-connected 3-phase IM under open-phase fault (faulty 3-phase IM)
using d-q model. The presented technique in this paper can be simply
implemented in one block and can be made available for control purposes.
The simulated results provide to show the behavior of the star-connected 3-phase IM under open-phase fault condition.
Performance Characteristics of Induction Motor with FielIJPEDS-IAES
With development of power electronics and control Theories, the AC motor
control becomes easier. So the AC motors are used instead of the DC motor
in the drive applications. With this development, a several methods of control
are invented. The field oriented control and direct torque control are from the
best methods to control the drive systems. This paper is compared between
the field oriented control and direct torque control to show the advantages
and disadvantages of these methods of controls. This study discussed the
effects of these methods of control on the total harmonic distortion of the
current and torque ripples. This occurs through study the performance
characteristics of the AC motor. The motor used in this study is an induction
motor. This study is simulated through the MATLAB program.
A Novel Modified Turn-on Angle Control Scheme for Torque- Ripple Reduction in...IJPEDS-IAES
In recent years, Switched Reluctance Motors (SRM) have been dramatically
considered with both researchers and industries. SRMs not only have a
simple and reliable structure, but also have low cost production process.
However, discrete torque production of SRM along with intensive magnetic
saturation in stator and rotor cores are the major drawbacks of utilizing in
variety of industrial applications and also causes the inappropriate torque
ripples. In this paper, a modified logical-rule-based Torque Sharing Function
(TSF) method is proposed considering turn-on angle control. The optimized
turn-on angle for conducting each phase is achieved by estimating the
inductance curve in the vicinity of unaligned position and based on an
analytical solution for each phase voltage equation. Simulation results on a
four-phase switched reluctance motor and comparison with the conventional
methods validates the effectiveness of the proposed method.
Modeling and Simulation of Induction Motor based on Finite Element AnalysisIJPEDS-IAES
This paper presents the development of a co-simulation platform of induction
motor (IM). For the simulation, a coupled model is introduced which
contains the control, the power electronics and also the induction machine.
Each of these components is simulated in different software environments.
So, this study provides an advanced modeling and simulation tools for IM
which integrate all the components into one common simulation platform
environment. In this work, the IM is created using Ansys-Maxwell based on
Finite Element Analysis (FEA), whereas the power electronic converter is
developed in Ansys-Simplorer and the control scheme is build in MATLABSimulink
environment. Such structure can be useful for accurate design
and allows coupling analysis for more realistic simulation. This platform is
exploited to analyze the system models with faults caused by failures of
different drive’s components. Here, two studies cases are presented: the first
is the effects of a faulty device of the PWM inverter, and the second case is
the influence of the short circuit of two stator phases. In order to study the
performance of the control drive of the IM under fault conditions,
a co-simulation of the global dynamic model has been proposed to analyze
the IM behavior and control drives. In this work, the co-simulation has been
performed; furthermore the simulation results of scalar control allowed
verifying the precision of the proposed FEM platform.
Comparative Performance Study for Closed Loop Operation of an Adjustable Spee...IJPEDS-IAES
In this paper an extensive comparative study is carried out between PI
and PID controlled closed loop model of an adjustable speed Permanent
Magnet Synchronous Motor (PMSM) drive. The incorporation of Sinusoidal
Pulse Width Modulation (SPWM) strategy establishes near sinusoidal
armature phase currents and comparatively less torque ripples without
sacrificing torque/weight ratio. In this closed loop model of PMSM drive, the
information about reference speed is provided to a speed controller, to ensure
that actual drive speed tracks the reference speed with ideally zero steady
state speed error. The entire model of PMSM closed loop drive is divided
into two loops, inner loop current and outer loop speed. By taking the
different combinations of two classical controllers (PI & PID) related with
two loop control structure, different approximations are carried out. Hence a
typical comparative study is introduced to familiar with the different
performance indices of the system corresponding to time domain and
frequency domain specifications. Therefore overall performance of closed
loop PMSM drive is tested and effectiveness of controllers will be
determined for different combinations.
Novel Discrete Components Based Speed Controller for Induction MotorIJPEDS-IAES
This paper presents an electronic design based on general purpose discrete
components for speed control of a single phase induction motor drive. The
MOSFETs inverter switching is controlled using Sampled Sinusoidal Pulse
Width Modulation (SPWM) techniques with V/F method based on Voltage
Controlled Oscillator (VCO). The load power is also controlled by a novel
design to produce a suitable SPWM pulse. The proposed electronic system
has ability to control the output frequency with flexible setting of lower limit
to less than 1 Hz and to higher frequency limits to 55 Hz. Moreover, the
proposed controller able to control the value of load voltage to frequency
ratio, which plays a major parameter in the function of IM speed control.
Furthermore, the designed system is characterized by easy manufacturing
and maintenance, high speed response, low cost, and does not need to
program steps as compared to other systems based on Microcontroller
and digital signal processor (DSP) units. The complete proposed electronic
design is made by the software of NI Multisim version 11.0 and all the
internal sub-designs are shown in this paper. Simulation results show the
effectiveness of electronic design for a promising of a high performance IM
PWM drive.
Sensorless Control of a Fault Tolerant PMSM Drives in Case of Single-Phase Op...IJPEDS-IAES
This paper introduces a sensorless-speed-controlled PMSM motor fed by a
four-leg inverter in case of a single phase open circuit fault regardless in
which phase is the fault. To minimize the system performance degradation
due to a single phase open circuit fault, a fault tolerant control strategy that
includes taking appropriate actions to control the two remaining healthy
currents is used in addition to use the fourth leg of the inverter. Tracking the
saliency is done through measuring the dynamic current responses of the
healthy phases of the PMSM motor due the IGBT switching actions using the
fundamental PWM method without introducing any modification to the
operation of the fourth leg of the inverter. Simulation results are provided to
verify the effectiveness of the proposed strategy for sensorless controlling of
a PMSM motor driven by a fault-tolerant four-phase inverter over a wide
speed ranges under the case of a single phase open circuit.
Improved Stator Flux Estimation for Direct Torque Control of Induction Motor ...IJPEDS-IAES
Stator flux estimation using voltage model is basically the integration of the
induced stator back electromotive force (emf) signal. In practical
implementation the pure integration is replaced by a low pass filter to avoid
the DC drift and saturation problems at the integrator output because of the
initial condition error and the inevitable DC components in the back emf
signal. However, the low pass filter introduces errors in the estimated stator
flux which are significant at frequencies near or lower than the cutoff
frequency. Also the DC components in the back emf signal are amplified at
the low pass filter output by a factor equals to . Therefore, different
integration algorithms have been proposed to improve the stator flux
estimation at steady state and transient conditions. In this paper a new
algorithm for stator flux estimation is proposed for direct torque control
(DTC) of induction motor drives. The proposed algorithm is composed of a
second order high pass filter and an integrator which can effectively
eliminates the effect of the error initial condition and the DC components.
The amplitude and phase errors compensation algorithm is selected such that
the steady state frequency response amplitude and phase angle are equivalent
to that of the pure integrator and the multiplication and division by stator
frequency are avoided. Also the cutoff frequency selection is improved; even
small value can filter out the DC components in the back emf signal. The
simulation results show the improved performance of the induction motor
direct torque control drive with the proposed stator flux estimation algorithm.
The simulation results are verified by the experimental results.
Minimization of Starting Energy Loss of Three Phase Induction Motors Based on...IJPEDS-IAES
The purpose of this paper is to minimize energy losses consumed by three
phase induction motors during starting with wide range of load torque from
no load to full load. This will limit the temperature rise and allows for more
numbers of starting during a definite time. Starting energy losses
minimization is achieved by controlling the rate of increasing voltage
and frequency to start induction motor under certain load torque within a
definite starting time. Optimal voltage and frequency are obtained by particle
swarm optimization (PSO) tool according to load torque. Then, outputs of the
PSO are used to design a neuro-fuzzy controller to control the output voltage
and frequency of the inverter during starting for each load torque. The
starting characteristics using proposed method are compared to that of direct
on line and V/F methods. A complete model of the system is developed using
SIMULINK/MATLAB.
IRAMY Inverter Control for Solar Electric VehicleIJPEDS-IAES
Solar Electric Vehicles (SEV) are considered the future vehicles to solve the issues of air pollution, global warming, and the rapid decreases of the petroleum resources facing the current transportation technology. However, SEV are still facing important technical obstacles to overcome. They include batteries energy storage capacity, charging times, efficiency of the solar panels and electrical propulsion systems. Solving any of those problems and electric vehicles will compete-complement the internal combustion engines vehicles. In the present work, we propose an electrical propulsion system based on three phase induction motor in order to obtain the desired speed and torque with less power loss. Because of the need to lightweight nature, small volume, low cost, less maintenance and high efficiency system, a three phase squirrel cage induction motor (IM) is selected in the electrical propulsion system. The IM is fed from three phase inverter operated by a constant V/F control method and Space Vector Pulse Width Modulation (SVPWM) algorithm. The proposed control strategy has been implemented on the texas instruments TM320F2812 Digital Signal Processor (DSP) to generate SVPWM signal needed to trigger the gates of IGBT based inverter. The inverter used in this work is a three phase inverter IRAMY20UP60B type. The experimental results show the ability of the proposed control strategy to generate a three-phase sine wave signal with desired frequency. The proposed control strategy is experimented on a locally manufactured EV prototype. The results show that the EV prototype can be propelled to speed up to 60km/h under different road conditions.
Design and Implementation of Single Phase AC-DC Buck-Boost Converter for Powe...IJPEDS-IAES
This paper discusses the Power Factor Correction (PFC) for single phase AC-DC Buck-Boost Converter (BBC) operated in Continuous Conduction Mode (CCM) using inductor average current mode control. The proposed control technique employs Proportional-Integral (PI) controller in the outer voltage loop and the Inductor Average Current Mode Control (IACMC) in the inner current loop for PFC BBC. The IACMC has advantages such as robustness when there are large variations in line voltage and output load. The PI controller is developed by using state space average model of BBC. The simulation of the proposed system with its control circuit is implemented in MatLab/Simulink. The simulation results show a nearly unity power factor can be attained and there is almost no change in power factor when the line frequency is at various ranges. Experimental results are provided to show its validity and feasibility.
Improvement of Wind farm with PMSG using STATCOMIJPEDS-IAES
This paper studies about the dynamic performance of the Permanent Magnet Synchronous Generator with Static Synchronous Compensator (STATCOM) for Wind farm integration. A whole dynamic model of wind energy conversion system (WECS) with PMSG and STATCOM are established in a MATLAB environment. With this model the dynamic behaviour of the generator and the overall system has been studied to determine the performance of them with and without STATCOM. Final results portrays that the WECS based PMSG with STATCOM improves the transient response of the wind farm when the system is in fault.
Modeling and Control of a Doubly-Fed Induction Generator for Wind Turbine-Gen...IJPEDS-IAES
This paper presents a vector control direct (FOC) of double fed induction generator intended to control the generated stator powers. This device is intended to be implemented in a variable-speed wind-energy conversion system connected to the grid. In order to control the active and reactive power exchanged between the machine stator and the grid, the rotor is fed by a bi-directional converter. The DFIG is controlled by standard relay controllers. Details of the control strategy and system simulation were performed using Simulink and the results are presented in this here to show the effectiveness of the proposed control strategy.
A Review on Design and Development of high Reliable Hybrid Energy Systems wit...IJPEDS-IAES
Hybrid Energy system is a combination of two or more different types of energy resources. Now a day this hybrid energy system plays key role in various remote area power applications. Hybrid energy system is more reliable than single energy system. This paper deals with high reliable hybrid energy system with solar, wind and micro hydro resources. The proposed hybrid system cable of multi mode operation and high reliable due to non communicated based controllers (Droop Characteristic Control) are used for optimal power sharing. Size of battery can be reduced because hydro used as back up source and Maximum power point Tracking also applied to solar and wind energy systems.
Fuzzy Sliding Mode Control for Photovoltaic SystemIJPEDS-IAES
In this study, a fuzzy sliding mode control (FSMC) based maximum power point tracking strategy has been applied for photovoltaic (PV) system. The key idea of the proposed technique is to combine the performances of the fuzzy logic and the sliding mode control in order to improve the generated power for a given set of climatic conditions. Different from traditional sliding mode control, the developed FSMC integrates two parts. The first part uses a fuzzy logic controller with two inputs and 25 rules as an equivalent controller while the second part is designed for an online adjusting of the switching controller’s gain using a fuzzy tuner with one input and one output. Simulation results showed the effectiveness of the proposed approach achieving maximum power point. The fuzzy sliding mode (FSM) controller takes less time to track the maximum power point, reduced the oscillation around the operating point and also removed the chattering phenomena that could lead to decrease the efficiency of the photovoltaic system.
An Experimental Study of P&O MPPT Control for Photovoltaic SystemsIJPEDS-IAES
Tracking the maximum power point plays an important role for the optimization of the solar energy. The objective here is to study experimentally optimizing photovoltaic (PV) systems connected to a DC-DC converter (Boost) and a resistive load. For this, tests were conducted to determine the law of open loop control (power versus the duty cycle) for different solar irradiance values and load with an approximately constant cell temperature. The obtained results showed that the power passes through a maximum point. In order to extract the maximum power, for different values of solar irradiance and load, an MPPT control "Perturb and Observe" P & O has been implemented on a DSPACE 1104. The experimental results showed the performance of the method suggested.
HEAP SORT ILLUSTRATED WITH HEAPIFY, BUILD HEAP FOR DYNAMIC ARRAYS.
Heap sort is a comparison-based sorting technique based on Binary Heap data structure. It is similar to the selection sort where we first find the minimum element and place the minimum element at the beginning. Repeat the same process for the remaining elements.
NUMERICAL SIMULATIONS OF HEAT AND MASS TRANSFER IN CONDENSING HEAT EXCHANGERS...ssuser7dcef0
Power plants release a large amount of water vapor into the
atmosphere through the stack. The flue gas can be a potential
source for obtaining much needed cooling water for a power
plant. If a power plant could recover and reuse a portion of this
moisture, it could reduce its total cooling water intake
requirement. One of the most practical way to recover water
from flue gas is to use a condensing heat exchanger. The power
plant could also recover latent heat due to condensation as well
as sensible heat due to lowering the flue gas exit temperature.
Additionally, harmful acids released from the stack can be
reduced in a condensing heat exchanger by acid condensation. reduced in a condensing heat exchanger by acid condensation.
Condensation of vapors in flue gas is a complicated
phenomenon since heat and mass transfer of water vapor and
various acids simultaneously occur in the presence of noncondensable
gases such as nitrogen and oxygen. Design of a
condenser depends on the knowledge and understanding of the
heat and mass transfer processes. A computer program for
numerical simulations of water (H2O) and sulfuric acid (H2SO4)
condensation in a flue gas condensing heat exchanger was
developed using MATLAB. Governing equations based on
mass and energy balances for the system were derived to
predict variables such as flue gas exit temperature, cooling
water outlet temperature, mole fraction and condensation rates
of water and sulfuric acid vapors. The equations were solved
using an iterative solution technique with calculations of heat
and mass transfer coefficients and physical properties.
CW RADAR, FMCW RADAR, FMCW ALTIMETER, AND THEIR PARAMETERSveerababupersonal22
It consists of cw radar and fmcw radar ,range measurement,if amplifier and fmcw altimeterThe CW radar operates using continuous wave transmission, while the FMCW radar employs frequency-modulated continuous wave technology. Range measurement is a crucial aspect of radar systems, providing information about the distance to a target. The IF amplifier plays a key role in signal processing, amplifying intermediate frequency signals for further analysis. The FMCW altimeter utilizes frequency-modulated continuous wave technology to accurately measure altitude above a reference point.
Sachpazis:Terzaghi Bearing Capacity Estimation in simple terms with Calculati...Dr.Costas Sachpazis
Terzaghi's soil bearing capacity theory, developed by Karl Terzaghi, is a fundamental principle in geotechnical engineering used to determine the bearing capacity of shallow foundations. This theory provides a method to calculate the ultimate bearing capacity of soil, which is the maximum load per unit area that the soil can support without undergoing shear failure. The Calculation HTML Code included.
6th International Conference on Machine Learning & Applications (CMLA 2024)ClaraZara1
6th International Conference on Machine Learning & Applications (CMLA 2024) will provide an excellent international forum for sharing knowledge and results in theory, methodology and applications of on Machine Learning & Applications.
Welcome to WIPAC Monthly the magazine brought to you by the LinkedIn Group Water Industry Process Automation & Control.
In this month's edition, along with this month's industry news to celebrate the 13 years since the group was created we have articles including
A case study of the used of Advanced Process Control at the Wastewater Treatment works at Lleida in Spain
A look back on an article on smart wastewater networks in order to see how the industry has measured up in the interim around the adoption of Digital Transformation in the Water Industry.
Cosmetic shop management system project report.pdfKamal Acharya
Buying new cosmetic products is difficult. It can even be scary for those who have sensitive skin and are prone to skin trouble. The information needed to alleviate this problem is on the back of each product, but it's thought to interpret those ingredient lists unless you have a background in chemistry.
Instead of buying and hoping for the best, we can use data science to help us predict which products may be good fits for us. It includes various function programs to do the above mentioned tasks.
Data file handling has been effectively used in the program.
The automated cosmetic shop management system should deal with the automation of general workflow and administration process of the shop. The main processes of the system focus on customer's request where the system is able to search the most appropriate products and deliver it to the customers. It should help the employees to quickly identify the list of cosmetic product that have reached the minimum quantity and also keep a track of expired date for each cosmetic product. It should help the employees to find the rack number in which the product is placed.It is also Faster and more efficient way.
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
Saudi Arabia stands as a titan in the global energy landscape, renowned for its abundant oil and gas resources. It's the largest exporter of petroleum and holds some of the world's most significant reserves. Let's delve into the top 10 oil and gas projects shaping Saudi Arabia's energy future in 2024.
2. ISSN: 2088-8694
IJPEDS Vol. 7, No. 4, December 2016 : 1023-1030
1024
switching stress and conduction loss. By using the voltage quadrupler, the output voltage is increased four
times. In this work, the π filters are connected at the output in order to reduce the current ripples and thereby
reducing the losses in the load.
The use of transformers are detached in theproposed circuit. Instead of using the transformer,
coupled inductors are used. Because the use of transformer enhances the saturation loss. The coupled
inductors have multiple windings coiled on the same core for high value of inductance in common mode
current while giving low value of inductance for the differential mode current. Coupled inductors have lower
leakage inductance and AC current losses when compared to the transformers.
Figure 1. Block Diagram of the Proposed System
In the voltage multiplier circuit, two or more peak rectifiers are cascaded to produce a DC voltage
equal to multiplier peak input voltages [7-8]. In this paper voltage quadrupler is used. The association of
another diode capacitor section with the voltage tripler circuit produces an output four times the peak voltage.
In this circuit, a π filter is proposed. A typical capacitor input filter or a π filter consists of a filter or reservoir
capacitor C1, connected to the rectifier output, an inductor L, in series and another filter or smoothing
capacitor, C2, connected to the load, RL. A filter of this type is designed for use at a particular frequency,
generally fixed by the AC line frequency and rectifier configuration. When used in this system, the filter
performance is often characterized by its regulation and ripple.
Generally, the capacitor C1 offers a low reactance to the AC component of the rectifier output while
it offers infinite resistance to the DC component. As a result, the capacitor shunts an appreciable amount of
the AC component while the DC component continues its journey to the inductor L. The inductor L offers
high reactance to the AC component but it offers almost zero resistance to the DC component. As a result the
DC component flows through the inductor while the AC component is blocked. The capacitor C2 shunts the
AC component which the inductor had failed to block. As a result only the DC component appears across the
load RL. The main merits of using a π filter are that it provides output voltage and also it achieves the ripple
free output.
Figure 2. Proposed System Circuit Diagram
3. IJPEDS ISSN: 2088-8694
Transformer Less Voltage Quadrupler Based DC-DC Converter with Coupled Inductor … (C. Sujitha)
1025
3. MODES OF OPERATION
The operation principle of the proposed circuit can be explained with four modes:
3.1. Mode 1 Operation
In this mode of operation, both the switches S1 and S2 are conducting which is exposed in Figure 3.
So the energy is stored in the coupled inductor. Along with the self inductance, there exists the mutual
inductance. Due to the mutual inductance, the output is increased.
Figure 3. Mode 1 Operation
3.2. Mode 2 Operation
The mode-2 operation is revealed in the Figure 4. In this mode, only the switch S1 is conducting.
The energy is stored by the inductor L1 and also some energy will be induced in the inductance L2 by the
principle of mutual inductance. The path followed by the induced energy will be Ca–Db2–Lf –C2.
Figure 4. Mode 2 Operation
3.3. Mode 3 Operation
The mode-3 operation is shown in the Figure 5. This mode of operation is similar to the mode 1
operation. In this mode also both the switches S1 and S2 areconducting. The energy is stored bythe coupled
inductor. Along with the self-inductance, the occurrence of the mutual inductance also takes place and due to
this the output value is increased.
4. ISSN: 2088-8694
IJPEDS Vol. 7, No. 4, December 2016 : 1023-1030
1026
Figure 5. Mode 3 Operation
3.4. Mode 4 Operation
The mode-4 operation is revealed in the Figure 6. In this mode of operation, the switch S2 will be
conducting. In the coil L1, some energy is induced due to the mutual inductance. The path followed by the
induced energy is from C1–Lf–R Db1–C2. In this mode, the output capacitor voltage is the sum of the voltage
across VCb andVCa.
4. MATLAB SIMULATION EXPLANATION
The simulation was done in the MATLAB/Simulink platform. The simulation block diagram is
shown the in Figure 7. The proposed converter uses the input of 16 V voltage which is shown in Figure 8
and the output voltage achieved is 240 V which is shown in Figure 9. The switching frequency used in this
circuit is 40 kHz and the duty ratio of S1, S2 is 0.50. This duty ratio is used to reduce voltagestress
and current and finally the conduction loss. The interleaved structure can effectively decrease the switching
losses.
Figure 6. Mode 4 Operation
Figure 7. MATLAB Simulink Circuit for the
Proposed Converter
5. IJPEDS ISSN: 2088-8694
Transformer Less Voltage Quadrupler Based DC-DC Converter with Coupled Inductor … (C. Sujitha)
1027
Figure 8. MATLAB Simulation of Input Voltage Figure 9. MATLAB Simulation of Output Voltage
5. EXPERIMENTAL MODULE
The overall block diagram of the laboratory prototype is shown in Figure 10. The hardware power
circuit is shown in Figure 11. Each block of the laboratory prototype is explained as follows. DC source gives
the DC supply to the boost converter. The DC source may be Battery or fuel cell or rectified from AC source.
Rectifier converts AC to DC. This output has ripples. It is filtered with thehelp of Capacitor. It is used to run
the motor, battery charging, and telecommunication applications. PIC 16F877A microcontroller is used to
generate triggering pulse for MOSFETs. It is used to control the outputs. Microcontrollers have more
advantages such as fast response, low cost, small size and etc. Interleaved Boost converter converts low
voltage dc supply to high voltage DC supply. The output voltage is controlled by controlling the firing angle
of the MOSFET. Interleaved concept is used to reduce the output ripple current. Regulated Power supply
(RPS) gives 5V supply for microcontrollers and 12V supply for driver. It is converted from the AC supply.
The AC supply is step down using step down transformer. The driver 1 and 2 arealso called as power
amplifier andthey are used to amplify the pulse output from microcontroller. It is also called asoptocoupler
IC. It provides isolation between microcontroller and power circuits. The components and ratings are shown
in Table 1.
Figure 10. Hardware Block Diagram
6. ISSN: 2088-8694
IJPEDS Vol. 7, No. 4, December 2016 : 1023-1030
1028
Table 1. Components and Ratings
Components Name Ratings
MOSFET IRF
840
500V, 8A
Diode IN
4007
1000V, 1A
Capacitor 10µf, 63V
Output Capacitor 470µf, 63V
Inductor 150µh, 2 A
Resistor 15KOhms,
10 Watt
Coupled Inductor 1:1 Ratio
Figure 11. Hardware Power Circuit
6. RESULTS AND DISCUSSION
The input voltage is givenin the simulation of the proposed circuit is 16 V which is shown in the
Figure 8. The output voltage achieved in the simulation is 240 V which is shown in the Figure 9. The overall
picture of the hardware kit is revealed in the Figure 12. The output voltage from the hardware obtained is
136.4 V which is shown in the Figure 13. The voltage output waveform of the hardware is shown in
Figure 14. From the simulation and hardware results, the proposed system achieved increased output voltage
gain with high efficiency and also the system is simple to control.For the transformer enabled system without
π filter, the voltage gain is 16 times and the efficiency is 78 %. But for the proposed system with π filter, the
voltage gain is increased to 18 times and also the efficiency increases by 83%. The output ripples in this
system is also reduced to minimum amount by using the π filter. From the simulation and the hardware
results obtained for the proposed system, the transformerless interleaved voltage quadrupler converter with π
filter and coupled inductor increases the output voltage gain, efficiency and decreases the output ripples by
using π filter and also the switching voltage stress can be reduced.
Figure 12. Hardware Picture of the Proposed System Figure 13. Output Voltage from the Hardware
7. IJPEDS ISSN: 2088-8694
Transformer Less Voltage Quadrupler Based DC-DC Converter with Coupled Inductor … (C. Sujitha)
1029
Figure 14. CRO Output Voltage Waveform
7. CONCLUSION
In this paper the interleaved Voltage quadrupler DC-DC converterwith coupled inductor was
discussed and it achieved high voltage gain and reduced voltage stress, current ripple and conduction losses.
With the help of interleaved boost converter with voltage quadrupler circuits and to get a balanced output
voltage connection of balanced capacitor finally the input voltage is 16V and the output voltage is 240V.
By using the coupled inductor the saturation loss also can bereduced. Hence the output voltage gain,
efficiency is increased and the switching voltage stress, output ripple content, conduction loss and switching
loss is reduced in this system. Hence the desired outcome was achieved by the use of interleaved quadrupler
voltage DC-DC converter with coupled inductor.
REFERENCES
[1] T.K. Santhosh and C. Govindraju, "Development of Predictive current controller for multi port dc-dc converter",
International journal of power electronics and drive systems, vol. 6, pp. 683-692, 2015.
[2] S. Ravi et.al. “Design and Implementation of a Microcontroller Based Buck Boost Converter as a Smooth Starter
for Permanent Magnet Motor”, Telkominka International Journal of Electrical Engineering and Computer Science,
vol. 1, pp. 566-574, 2016.
[3] Dingzhen Li, Haizhen Guo, “Control Strategy of Three Phase PWM by Three Half Bridge Topology Bidirectional
DC/DC Converter and Resonant”, Telkominka Indonesian Journal of Electrical and Computer Engineering. vol.
12, pp. 6111-6118, 2014.
[4] S. Ravi and P.A. Balakrishnan, “Design of Synthetic Optimizing Neuro Fuzzy Temperature Controller for Dual
Screw Profile Plastic Extruder Using LabVIEW”, Journal of Computer Science, vol. 7, pp. 671-677, 2011.
[5] J. Linares Flores and H. Sira Ramırez, "DC motor velocity control through a DC-to-DC power converter",
Proceedings of the IEEE 43rd Conf. Decis.Control, 2004, vol. 5, pp. 5297– 5302.
[6] S. Ravi, "Modelling and Control of an ANFIS Temperature Controller for Plastic Extrusion Process", Proceedings
of the 2010 IEEE International Conference on Communication Control and Computing Technologies.
[7] Oladimeji Ibrahim et.al., "PID controller response to set point change in DC-DC converter control", International
journal of power electronics and drive systems, vol. 7, 2016.
[8] K. Vinoth Kumar et.al., "Soft computing module of High step up DC-DC converter for PV module using simulink
environment", International journal of power electronics and drive systems, vol. 3, pp. 53-61, 2013
BIOGRAPHIES OF AUTHORS
Ms. C. Sujitha received his B.E degree in Electrical and Electronics Engineering from Nandha
Engineering college, Erode, India in 2009. She received her M.E degree in Power electronics
from Kumaraguru College of Technology, Coimbatore in 2011. Also she received her M.B.A.
degree in Human Resources from Bharathiyar University, Coimbatore. Presently she is working
as an assistant professor in the department of Electrical and Electronics Engineering, SRM
University, Kattankulathur, Chennai, India. Her research interests includes the area of renewable
energy resources, smart grid, power quality issues, application of power electronics and drives,
web and embedded systems. She is a life member of Indian Society of Technical Education,
member of Indian Science Congress and a member of IEEE.
8. ISSN: 2088-8694
IJPEDS Vol. 7, No. 4, December 2016 : 1023-1030
1030
S. Ravireceived his B.E degree in Electrical and Electronics Engineering from Periyar
University, Salem, India in 2003. He received his M.E degree in Power Electronics and Drives
from Anna University, Chennai, India in 2006. He received his Ph.D degree in the area of
Intelligent Control Systems from Anna University, Chennai, India in 2012. Presently he is
working as a Senior Lecturer in the Department of Electrical, College of Engineering and
Technology, Botswana International University of Science and Technology, Botswana. His
research areas are intelligent control systems, Solar PV systems, Power Electronic Converters.
He has published 50 research papers in reputed International Journals and Conferences.
Bakary Diarra received his B.E degree in Electrical Engineering in 2008 from Joseph Fourier
University of Grenoble, France. He received his M.E degree in Electrical Engineering in 2010
from the National Institute of Applied Sciences of Lyon (INSA Lyon), France. He obtained his
PhD in 2013 in ultrasound imaging and optimization from Claude Bernard University of Lyon in
co-supervision with the University of Florence in Italy. His research focuses on the design and
the optimization of 2D matrix sensor array using global optimization algorithms. Currently, Dr
Diarra is a lecturer in electrical engineering at Botswana International University of Science and
Technology (BIUST).
Joseph M. Chuma is an Associate Professor of Telecommunication and Wireless
Communications at the Botswana International University of Science and Technology. He
received a BEng in Electrical and Electronic Engineering from University of Nottingham, UK in
1992, an MSc in Telecommunications and Information Systems and a PhD in Electronic Systems
Engineering from University of Essex, UK in 1995 and 2001 respectively. His main areas of
research are in the design of compact single and dual mode dielectric resonator filters for mobile
communications. His research work has led to successful results in the development of dielectric
loaded filters and shown that the size of the conventional combline filter can be reduced in
excess of 75%. In this example, a dielectric ring has been used to load a conventional combline
resonator. Prof Chuma has served as the Dean of the Faculty of Engineering and Technology at
University of Botswana. He is also serving as a Board Member in a member of
ParastatalsOrganisation in Botswana. He has also served as a Postgraduate and Undergraduate
external examiner in a number of Universities.