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UNIFIED LARGE AND SMALL SIGNAL DISCRETE-SPACE MODELING FOR PWM CONVERTERS IN CCM
Title
UNIFIED LARGE AND SMALL SIGNAL DISCRETE-SPACE MODELING FOR PWM CONVERTERS IN CCM.
Creator
Shoubaki, Ehab, Batarseh, Issa, University of Central Florida
Abstract / Description
In this Thesis a Unified Discrete State-Space Model for power converters in CCM is presented. Two main approaches to arriving at the discrete model are used. The first approach involves an impulse function approximation of the duty cycle modulations of the converter switches , and this approach results in a small signal discrete model. The Second approach is direct and does not involve any approximation of the modulations , this approach yields both a large signal nonlinear discrete model and...
Show moreIn this Thesis a Unified Discrete State-Space Model for power converters in CCM is presented. Two main approaches to arriving at the discrete model are used. The first approach involves an impulse function approximation of the duty cycle modulations of the converter switches , and this approach results in a small signal discrete model. The Second approach is direct and does not involve any approximation of the modulations , this approach yields both a large signal nonlinear discrete model and a linear small signal model. Harmonic analysis of the converter states at steady-state is done for steady-state waveform acquisition , which increases the accuracy of the model especially for finding the control to inductor current frequency response. Finally the Discrete model is verified for the Half-Bridge DC/DC topology for its three main control schemes (Asymmetric , Symmetric , DCS). A GUI platform in MATLAB is presented as a wrapper that utilizes the models and analysis presented in this thesis.
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Date Issued
2005
Identifier
CFE0000710, ucf:46607
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0000710
DIGITAL CONTROL OF HALF-BRIDGE DC-DC CONVERTERS WITH CURRENT DOUBLER RECTIFICATION
Title
DIGITAL CONTROL OF HALF-BRIDGE DC-DC CONVERTERS WITH CURRENT DOUBLER RECTIFICATION.
Creator
Yao, Liangbin, Batarseh, Issa, University of Central Florida
Abstract / Description
DC-DC power converters play an important role in powering telecom and computing systems. Complex systems, including power electronics systems, are increasingly using digital controllers because of the major advancements in digital controllers and DSP as well as there ability to perform sophisticated and enhanced control schemes. In this thesis, the digital controller is investigated for DC-DC converters in high current low voltage applications. For an optimal design of a regulated DC-DC...
Show moreDC-DC power converters play an important role in powering telecom and computing systems. Complex systems, including power electronics systems, are increasingly using digital controllers because of the major advancements in digital controllers and DSP as well as there ability to perform sophisticated and enhanced control schemes. In this thesis, the digital controller is investigated for DC-DC converters in high current low voltage applications. For an optimal design of a regulated DC-DC converter, it is necessary to derive a valid model. The current doubler rectified half bridge (CDRHB) DC-DC converter is suitable for high current low voltage applications. In this thesis, the topology operations are analyzed and then the unified state space model, analog small signal model and digital small signal model are derived. Then the digital compensator design is discussed as well as the analog-digital converter (ADC) and the digital pulse-width-modulator (DPWM) design rules. In addition, voltage driving optimization is proposed for the benefit of the digital controller. Finally, experimental results based on the CDRHB are presented and analyzed.
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Date Issued
2005
Identifier
CFE0000706, ucf:46626
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0000706
HIGH SLEW RATE HIGH-EFFICIENCY DC-DC CONVERTER
Title
HIGH SLEW RATE HIGH-EFFICIENCY DC-DC CONVERTER.
Creator
Wang, Xiangcheng, Issa, Batarseh, University of Central Florida
Abstract / Description
Active transient voltage compensator (ATVC) has been proposed to improve VR transient response at high slew rate load, which engages in transient periods operating in MHZ to inject high slew rate current in step up load and recovers energy in step down load. Main VR operates in low switching frequency mainly providing DC current. Parallel ATVC has largely reduced conduction and switching losses. Parallel ATVC also reduces the number of VR bulk capacitors. Combined linear and adaptive...
Show moreActive transient voltage compensator (ATVC) has been proposed to improve VR transient response at high slew rate load, which engages in transient periods operating in MHZ to inject high slew rate current in step up load and recovers energy in step down load. Main VR operates in low switching frequency mainly providing DC current. Parallel ATVC has largely reduced conduction and switching losses. Parallel ATVC also reduces the number of VR bulk capacitors. Combined linear and adaptive nonlinear control has been proposed to reduce delay times in the actual controller, which injects one nonlinear signal in transient periods and simplifies the linear controller design. Switching mode current compensator with nonlinear control in secondary side is proposed to eliminate the effect of opotocoupler, which reduces response times and simplifies the linear controller design in isolated DC-DC converters. A novel control method has been carried out in two-stage isolated DC-DC converter to simplify the control scheme and improve the transient response, allowing for high duty cycle operation and large step-down voltage ratio with high efficiency. A balancing winding network composed of small power rating components is used to mitigate the double pole-zero effect in complementary-controlled isolated DC-DC converter, which simplifies the linear control design and improves the transient response without delay time. A parallel post regulator (PPR) is proposed for wide range input isolated DC-DC converter with secondary side control, which provides small part of output power and most of them are handled by unregulated rectifier with high efficiency. PPR is easy to achieve ZVS in primary side both in wide range input and full load range due to 0.5 duty cycle. PPR has reduced conduction loss and reduced voltage rating in the secondary side due to high turn ratio transformer, resulting in up to 8 percent efficiency improvement in the prototype compared to conventional methods.
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Date Issued
2006
Identifier
CFE0001123, ucf:46877
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0001123
UNIFIED STEADY-STATE COMPUTER AIDED MODEL FOR SOFT-SWITCHING DC–DC CONVERTERS
Title
UNIFIED STEADY-STATE COMPUTER AIDED MODEL FOR SOFT-SWITCHING DC–DC CONVERTERS.
Creator
Al-Hoor, Wisam, Batarseh, Issa, University of Central Florida
Abstract / Description
For many decades, engineers and students have heavily depended on simulation packages such as Pspice to run transit and steady-state simulation for their circuits. The majority of these circuits, such as soft switching cells, contain complicated modes of operations that require the Pspice simulation to run for a long time and, finally, it may not reach a convergent solution for these kinds of circuits. Also, there is a need for an educational tool that provides students with a better...
Show moreFor many decades, engineers and students have heavily depended on simulation packages such as Pspice to run transit and steady-state simulation for their circuits. The majority of these circuits, such as soft switching cells, contain complicated modes of operations that require the Pspice simulation to run for a long time and, finally, it may not reach a convergent solution for these kinds of circuits. Also, there is a need for an educational tool that provides students with a better understanding of circuit modes of operation through state-plan figures and steady-state switching waveforms. The unified steady-state computer aided model proposes a simulation block that covers common unified soft-switching cells operations and can be used in topologies simulation. The simulation block has a simple interface that enables the user to choose the switching cell type and connects the developed simulation model in the desired topology configuration. In addition to the measured information that can be obtained from the circuitry around the unified simulation model, the simulation block includes some additional nodes (other than the inputs and outputs) that make internal switching cell information, such as switching voltages and currents, easy to access and debug. The model is based on mathematical equations, resulting in faster simulation times, smaller file size and greatly minimized simulation convergence problems. The Unified Model is based on the generalized analysis: Chapter 1 discusses the generalized equation concept along with a detailed generalization example of one switching cell, which is the zero current switching quasi-resonant converter ZCS-QRC. Chapter 2 presents a detailed discussion of the unified model concept, the unified model flow chart and the unified model implementation in Pspice. Chapter 3 presents the unified model applications; generating the switching cell inductor current and the switching cell capacitor voltage steady-state waveforms, the State-Plane Diagram , the feedback design using the unified model, and the chapter concludes with how the model can be used with different topologies. Finally, chapter 4 presents the summary and the future work
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Date Issued
2006
Identifier
CFE0001036, ucf:46825
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0001036
SMALL-SCALE HYBRID ALTERNATIVE ENERGY MAXIMIZER FOR WIND TURBINES AND PHOTOVOLTAIC PANELS
Title
SMALL-SCALE HYBRID ALTERNATIVE ENERGY MAXIMIZER FOR WIND TURBINES AND PHOTOVOLTAIC PANELS.
Creator
Kerley, Ross, Batarseh, Issa, University of Central Florida
Abstract / Description
This thesis describes the creation of a small-scale Hybrid Power System (HPS) that maximizes energy from a wind turbine and photovoltaic array. Small-scale HPS are becoming an increasingly viable energy solution as fossil fuel prices rise and more electricity is needed in remote areas. Modern HPS typically employ wind speed sensors and three power stages to extract maximum power. Modern systems also use passive rectifiers to convert AC from the wind turbine to DC that is usable by power...
Show moreThis thesis describes the creation of a small-scale Hybrid Power System (HPS) that maximizes energy from a wind turbine and photovoltaic array. Small-scale HPS are becoming an increasingly viable energy solution as fossil fuel prices rise and more electricity is needed in remote areas. Modern HPS typically employ wind speed sensors and three power stages to extract maximum power. Modern systems also use passive rectifiers to convert AC from the wind turbine to DC that is usable by power electronics. This passive system inefficiently wastes power and introduces damaging harmonic noise to the wind turbine. The HPS described in this thesis does not require external wind speed sensors, and has independent wind and solar Maximum Power Point Tracking (MPPT). It converts AC from the wind turbine to DC with a Vienna rectifier that can be controlled to improve efficiency, allow MPPT, and allow Power Factor Correction (PFC). PFC all but eliminates the harmonic noise that can damage the wind turbine. A prototype HPS was built and evaluated that combines the two renewable sources in such a way that only two power stages are necessary, the Vienna rectifier and a step-down converter. This thesis describes the prototype and reports the results obtained.
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Date Issued
2011
Identifier
CFH0004087, ucf:44799
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFH0004087
EFFICIENCY IMPROVEMENT TECHNIQUES FOR HIGH VOLTAGE CAPACITOR CHARGING METHODS
Title
EFFICIENCY IMPROVEMENT TECHNIQUES FOR HIGH VOLTAGE CAPACITOR CHARGING METHODS.
Creator
Islas, Michael, Batarseh, Issa, University of Central Florida
Abstract / Description
The goal of this thesis is to design and fabricate a DC-to-DC converter for use in high-voltage capacitor charging applications. The primary objectives include increasing the efficiency and reducing the cost of traditional methods used for this application. Traditional methods were not designed specifically for high-voltage capacitor charging and were thus very primitive and exhibited lower efficiency. Prior methods made use of a high voltage power supply and a current limiting resistor or...
Show moreThe goal of this thesis is to design and fabricate a DC-to-DC converter for use in high-voltage capacitor charging applications. The primary objectives include increasing the efficiency and reducing the cost of traditional methods used for this application. Traditional methods were not designed specifically for high-voltage capacitor charging and were thus very primitive and exhibited lower efficiency. Prior methods made use of a high voltage power supply and a current limiting resistor or control scheme. The power supply would often only operate efficiently at a single voltage value and would thus function poorly over a range used in charging a capacitor. The resistor would also dissipate a fair amount of power, also limiting efficiency. This design makes use of a traditional flyback topology utilizing a controller developed specifically for this application, centering the design approach on the LT3750. Hence, taking full advantage of the efficiency improving control scheme it provides. Additionally, through the use of advanced techniques to eliminate noise and power losses, the efficiency may be significantly improved. A detailed theoretical analysis of the charger is also presented. The analysis will then be applied to optimization techniques to select ideal component values to meet specific design specifications. In this research, a specifically designed and developed prototype will be used to experimentally verify the theoretical work and optimization techniques.
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Date Issued
2009
Identifier
CFE0002899, ucf:48025
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0002899
ADAPTIVE EFFICIENCY OPTIMIZATION FOR DIGITALLY CONTROLLED DC-DC CONVERTERS
Title
ADAPTIVE EFFICIENCY OPTIMIZATION FOR DIGITALLY CONTROLLED DC-DC CONVERTERS.
Creator
AL-HOOR, WISAM, Batarseh, Issa, University of Central Florida
Abstract / Description
The design optimization of DC-DC converters requires the optimum selection of several parameters to achieve improved efficiency and performance. Some of these parameters are load dependent, line dependent, components dependent, and/or temperature dependent. Designing such parameters for a specific load, input and output, components, and temperature may improve single design point efficiency but will not result in maximum efficiency at different conditions, and will not guarantee improvement...
Show moreThe design optimization of DC-DC converters requires the optimum selection of several parameters to achieve improved efficiency and performance. Some of these parameters are load dependent, line dependent, components dependent, and/or temperature dependent. Designing such parameters for a specific load, input and output, components, and temperature may improve single design point efficiency but will not result in maximum efficiency at different conditions, and will not guarantee improvement at that design point because of the components, temperature, and operating point variations. The ability of digital controllers to perform sophisticated algorithms makes it easy to apply adaptive control, where system parameters can be adaptively adjusted in response to system behavior in order to achieve better performance and stability. The use of adaptive control for power electronics is first applied with the Adaptive Frequency Optimization (AFO) method, which presents an auto-tuning adaptive digital controller with maximum efficiency point tracking to optimize DC-DC converter switching frequency. The AFO controller adjusts the DC-DC converter switching frequency while tracking the converter minimum input power point, under variable operating conditions, to find the optimum switching frequency that will result in minimum total loss and thus the maximum efficiency. Implementing variable switching frequencies in digital controllers introduces two main issues, namely, limit cycle oscillation and system instability. Dynamic Limit Cycle Algorithms (DLCA) is a dynamic technique tailored to improve system stability and to reduce limit cycle oscillation under variable switching frequency operation. The convergence speed and stability of AFO algorithm is further improved by presenting the analysis and design of a digital controller with adaptive auto-tuning algorithm that has a variable step size to track and detect the optimum switching frequency for a DC-DC converter. The Variable-Step-Size (VSS) algorithm is theoretically analyzed and developed based on buck DC-DC converter loss model and directed towered improving the convergence speed and accuracy of AFO adaptive loop by adjusting the converter switching frequency with variable step size. Finally, the efficiency of DC-DC converters is a function of several variables. Optimizing single variable alone may not result in maximum or global efficiency point. The issue of adjusting more than one variable at the same time is addressed by the Multivariable Adaptive digital Controller (MVAC). The MVAC is an adaptive method that continuously adjusts the DC-DC converter switching frequency and dead-time at the same time, while tracking the converter minimum input power, to find the maximum global efficiency point under variable conditions. In this research work, all adaptive methods were discussed, theoretically analyzed and its digital control algorithm along with experimental implementations were presented.
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Date Issued
2009
Identifier
CFE0002838, ucf:48072
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0002838
UNIFIED LARGE AND SMALL SIGNAL STATE-SPACE BASED MODELING AND SYMBOLIC SIMULATION FOR PWM CONVERTERS
Title
UNIFIED LARGE AND SMALL SIGNAL STATE-SPACE BASED MODELING AND SYMBOLIC SIMULATION FOR PWM CONVERTERS.
Creator
Shoubaki, Ehab, Batarseh, Issa, University of Central Florida
Abstract / Description
In this Dissertation, which concentrates on discrete modeling for control purposes of DC/DC converters and simulation through symbolic techniques. A Unified Discrete State-Space Model for power converters in CCM is presented. Two main approaches to arriving at the discrete model are used. The first approach involves an impulse function approximation of the duty cycle modulation of the converter switches, and this approach results in a small signal discrete model. The Second approach is direct...
Show moreIn this Dissertation, which concentrates on discrete modeling for control purposes of DC/DC converters and simulation through symbolic techniques. A Unified Discrete State-Space Model for power converters in CCM is presented. Two main approaches to arriving at the discrete model are used. The first approach involves an impulse function approximation of the duty cycle modulation of the converter switches, and this approach results in a small signal discrete model. The Second approach is direct and does not involve any approximation of the modulation, this approach yields both a large signal nonlinear discrete model and a linear small signal model. Harmonic analysis of the converter's states at steady-state is done for steady-state waveform acquisition, which increases the accuracy of the model especially for finding the control to inductor current frequency response. Also the harmonic Analysis technique is used to both obtain the response of the converter to a load transient and to finding the optimal duty cycle response that minimizes the disturbance. Finally the Discrete model is verified for the Half-Bridge DC/DC topology for its three main control schemes (Asymmetric, Symmetric, DCS). A GUI platform in MATLAB is presented as a wrapper that utilizes the models and analysis presented in this thesis. Symbolic simulation techniques are developed in general manner for linear piecewise circuits and then through State-Space formalism specialized for DC/DC converters. A general symbolic solver programmed in JAVA that implements said techniques is presented.
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Date Issued
2009
Identifier
CFE0002836, ucf:48061
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0002836
Topology and control investigation for low-voltage high-current isolated DC-DC converters
Title
Topology and control investigation for low-voltage high-current isolated DC-DC converters.
Creator
Mao, Hong, Batarseh, Issa, Engineering and Computer Science
Abstract / Description
University of Central Florida College of Engineering Thesis; High conversion efficiency and fast transient response at high switching frequency are the two main challenges for low-voltage high-current DC-DC converters, which are the motivations of the dissertation work. To reduce the switching power loss, soft switching is a desirable technique to keep power loss under control at high switching frequencies. A Duty-Cycle-Shift (DCS) concept is proposed for half-bridge DC-DC converters to...
Show moreUniversity of Central Florida College of Engineering Thesis; High conversion efficiency and fast transient response at high switching frequency are the two main challenges for low-voltage high-current DC-DC converters, which are the motivations of the dissertation work. To reduce the switching power loss, soft switching is a desirable technique to keep power loss under control at high switching frequencies. A Duty-Cycle-Shift (DCS) concept is proposed for half-bridge DC-DC converters to reduce switching loss. The concept of this new control scheme is shifting one of the two symmetric PWM driving signals close to the other, such that ZVS can be achieved for the lagging switch due to the shortened resonant interval.
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Date Issued
2004
Identifier
CFR0001718, ucf:52921
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFR0001718
Low voltage regulator modules and single stage front-end converters
Title
Low voltage regulator modules and single stage front-end converters.
Creator
Gu, Wei, Batarseh, Issa, Engineering and Computer Science
Abstract / Description
University of Central Florida College of Engineering Thesis; Evolution in microprocessor technology poses new challenges for supplying power to these devices. To meet demands for faster and more efficient data processing, modem microprocessors are being designed with lower voltage implementations. More devices will be packed on a single processor chip and the processors will operate at higher frequencies, exceeding IGHz. New high performance microprocessors may require from 40 to 80 watts of...
Show moreUniversity of Central Florida College of Engineering Thesis; Evolution in microprocessor technology poses new challenges for supplying power to these devices. To meet demands for faster and more efficient data processing, modem microprocessors are being designed with lower voltage implementations. More devices will be packed on a single processor chip and the processors will operate at higher frequencies, exceeding IGHz. New high performance microprocessors may require from 40 to 80 watts of power for the CPU alone. Load current must be supplied with up to 30A/us slew rate while keeping the output voltage within tight regulation and response time tolerances. Therefore, special power supplies and Voltage Regulator Modules (VRMs) are needed to provide lower voltage with higher current and fast response.
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Date Issued
2001
Identifier
CFR0000194, ucf:52938
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFR0000194
THREE-PORT MICRO-INVERTER WITH POWER DECOUPLING CAPABILITY FOR PHOTOVOLTAIC (PV) SYSTEMS APPLICATIONS
Title
THREE-PORT MICRO-INVERTER WITH POWER DECOUPLING CAPABILITY FOR PHOTOVOLTAIC (PV) SYSTEMS APPLICATIONS.
Creator
Harb, Souhib, Batarseh, Issa, University of Central Florida
Abstract / Description
The Photovoltaic (PV) systems have been realized using different architectures, starting with the string and centralized PV system to the modular PV system. Presently, decentralized inverters are being developed at the PV panel power level (known as AC – PV Modules). Such new PV systems are becoming more attractive and many expect this will be the trend of the future. The AC-Module PV system consists of an inverter attached to one PV panel. This integration requires...
Show moreThe Photovoltaic (PV) systems have been realized using different architectures, starting with the string and centralized PV system to the modular PV system. Presently, decentralized inverters are being developed at the PV panel power level (known as AC – PV Modules). Such new PV systems are becoming more attractive and many expect this will be the trend of the future. The AC-Module PV system consists of an inverter attached to one PV panel. This integration requires that both devices have the same life-span. Although, the available commercial inverters have a relatively short life-span (10 years) compared to the 25 –year PV. It has been stated in literature that the energy storage capacitor (electrolytic type) in the single-phase inverter is the most vulnerable electronic component. Hence, many techniques such as (power decoupling techniques) have been proposed to solve this problem by replacing the large electrolytic capacitor with a small film capacitor. This thesis will present a quick review of these power decoupling techniques, and proposes a new three-port micro-inverter with power decoupling capability for AC-Module PV system applications.
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Date Issued
2010
Identifier
CFE0003357, ucf:48474
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003357
CONTROL STRATEGY FOR MAXIMIZING POWER CONVERSION EFFICIENCY AND EFFECTIVENESS OF THREE PORT SOLAR CHARGING STATION FOR ELECTRIC VEHICLES
Title
CONTROL STRATEGY FOR MAXIMIZING POWER CONVERSION EFFICIENCY AND EFFECTIVENESS OF THREE PORT SOLAR CHARGING STATION FOR ELECTRIC VEHICLES.
Creator
Hamilton, Christopher, Batarseh, Issa, University of Central Florida
Abstract / Description
Recent trends in the energy sector have provided opportunities in the research of alternative energy sources and optimization of systems that harness these energy sources. With the rising cost of fossil fuel and rising concern about detrimental effects that fossil fuel consumption has on the environment, electric vehicles are becoming more prevalent. A study put out in 2009 gives a prediction that in the year 2025, 20% of new vehicles will be PHEVs. As energy providers become more concerned...
Show moreRecent trends in the energy sector have provided opportunities in the research of alternative energy sources and optimization of systems that harness these energy sources. With the rising cost of fossil fuel and rising concern about detrimental effects that fossil fuel consumption has on the environment, electric vehicles are becoming more prevalent. A study put out in 2009 gives a prediction that in the year 2025, 20% of new vehicles will be PHEVs. As energy providers become more concerned about a growing population and diminishing energy source, they are looking into alternative energy sources such as wind and solar power. Much of this is done on a large scale with vast amounts of land used for solar or wind farms to provide energy to the grid. However, as population grows, requirements of the physical components of a power transmission system will become more demanding and the need for remote micro-grids will become more prevalent. Micro-grids are essentially smaller subsystems of a distribution system that provide power to a confined group of loads, or households. Using the idea of micro grid technology, a solar charging station can be used as a source to provide energy for the immediate surroundings, or also to electric vehicles that are demanding energy from the panels. Solar charging stations are becoming very popular, however the need for improvement and optimization of these systems is needed. This thesis will present a method for redesigning the overall architecture of the controls and power electronics of typical carports so that efficiency, reliability and modularity are achieved. Specifically, a typical carport, as seen commonly today, has been built on the University of Central Florida campus in Orlando. This carport was designed in such a way that shifting from conventional charging methods is made easy while preserving the fundamental requirements of a practical solar carport.
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Date Issued
2010
Identifier
CFE0003490, ucf:48954
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003490
HIGH-DENSITY AND HIGH-EFFICIENCY SOFT SWITCHING MODULAR BI-DIRECTIONAL DC-DC CONVERTER FOR HYBRID ELECTRIC VEHICLES
Title
HIGH-DENSITY AND HIGH-EFFICIENCY SOFT SWITCHING MODULAR BI-DIRECTIONAL DC-DC CONVERTER FOR HYBRID ELECTRIC VEHICLES.
Creator
Elmes, John, Batarseh, Issa, University of Central Florida
Abstract / Description
This dissertation presents the design of a high-density and high-efficiency soft-switching bi-directional DC-DC converter for hybrid-electric vehicles. The converter operates in a new bi-directional interleaved variable-frequency quasi-square-wave (QSW) mode, which enables high efficiency, high switching frequency, and high power-density. The converter presented utilizes a new variable frequency interleaving approach which allows for each module to operate in an interleaved position while...
Show moreThis dissertation presents the design of a high-density and high-efficiency soft-switching bi-directional DC-DC converter for hybrid-electric vehicles. The converter operates in a new bi-directional interleaved variable-frequency quasi-square-wave (QSW) mode, which enables high efficiency, high switching frequency, and high power-density. The converter presented utilizes a new variable frequency interleaving approach which allows for each module to operate in an interleaved position while allowing for tolerance in inductance and snubber capacitor values. The variable frequency interleaved soft-switching operation paired with a high-density nanocrystalline inductor and high-density system structure results in a very high performance converter, well exceeding that of the current technology. The developed converter is intended to achieve three specific performance goals: high conversion efficiency, high power density, and operation with 100 °C coolant. Two markedly different converter prototype designs are presented, one converter using evaporative spray cooling to cool the switching devices, with the second converter using a more traditional coldplate design to cool the switching devices. The 200 kW (25 kW per module) prototype converters exhibited power density greater than 8 kilowatts/liter (kW/L), and peak efficiency over 98%, while operating with 100 °C coolant.
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Date Issued
2010
Identifier
CFE0003366, ucf:48436
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003366
MODELING AND DESIGN OF MULTI-PORT DC/DC CONVERTERS
Title
MODELING AND DESIGN OF MULTI-PORT DC/DC CONVERTERS.
Creator
Qian, Zhijun, Batarseh, Issa, University of Central Florida
Abstract / Description
In this dissertation, a new satellite platform power architecture based on paralleled three-port DC/DC converters is proposed to reduce the total satellite power system mass. Moreover, a four-port DC/DC converter is proposed for renewable energy applications where several renewable sources are employed. Compared to the traditional two-port converter, three-port or four-port converters are classified as multi-port converters. Multi-port converters have less component count and less conversion...
Show moreIn this dissertation, a new satellite platform power architecture based on paralleled three-port DC/DC converters is proposed to reduce the total satellite power system mass. Moreover, a four-port DC/DC converter is proposed for renewable energy applications where several renewable sources are employed. Compared to the traditional two-port converter, three-port or four-port converters are classified as multi-port converters. Multi-port converters have less component count and less conversion stage than the traditional power processing solution which adopts several independent two-port converters. Due to their advantages multi-port converters recently have attracted much attention in academia, resulting in many topologies for various applications. But all proposed topologies have at least one of the following disadvantages: 1) no bidirectional port; 2) lack of proper isolation; 3) too many active and passive components; 4) no soft-switching. In addition, most existing research focuses on the topology investigation, but lacks study on the multi-port converterÂÂ's control aspects, which are actually very challenging since it is a multi-input multi-output control system and has so many cross-coupled control loops. A three-port converter is proposed and used for space applications. The topology features bidirectional capability, low component count and soft-switching for all active switches, and has one output port to meet certain isolating requirements. For the system level control strategy, the multi-functional central controller has to achieve maximal power harvesting for the solar panel, the battery charge control for the battery, and output voltage regulation for the dc bus. In order to design these various controllers, a good dynamic model of the control object should be obtained first. Therefore, a modeling procedure based on a traditional state-space averaging method is proposed to characterize the dynamic behavior of such a multi-port converter. The proposed modeling method is clear and easy to follow, and can be extended for other multi-port converters. In order to boost the power level of the multi-port converter system and allow redundancy, the three-port converters are paralleled together. The current sharing control for the multi-port converters has rarely been reported. A so called ÂÂ"dual loopÂÂ" current sharing control structure is identified to be suitable for the paralleled multi-port converters, since its current loop and the voltage loop can be considered and designed independently, which simplifies the multi-port converterÂÂ's loop analysis. The design criteria for that dual loop structure are also studied to achieve good current sharing dynamics while guaranteeing the system stability. The renewable energy applications are continuously demanding the low cost solution, so that the renewable energy might have a more competitive dollar per kilowatt figure than the traditional fossil fuel power generation. For this reason, the multi-port converter is a good candidate for such applications due to the low component count and low cost. Especially when several renewable sources are combined to increase the power delivering certainty, the multi-port solution is more beneficial since it can replace more separate converters. A four-port converter is proposed to interface two different renewable sources, such as the wind turbine and the solar panel, one bidirectional battery device, and the galvanically isolated load. The four-port converter is based on the traditional half-bridge topology making it easy for the practicing power electronics engineer to follow the circuit design. Moreover, this topology can be extended into n input ports which allow more input renewable sources. Finally, the work is summarized and concluded, and references are listed.
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Date Issued
2010
Identifier
CFE0003001, ucf:48373
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003001
REALIZATION OF POWER FACTOR CORRECTION AND MAXIMUM POWER POINT TRACKING FOR LOW POWER WIND TURBINES
Title
REALIZATION OF POWER FACTOR CORRECTION AND MAXIMUM POWER POINT TRACKING FOR LOW POWER WIND TURBINES.
Creator
Gamboa, Gustavo, Batarseh, Issa, University of Central Florida
Abstract / Description
In recent years, wind energy technology has become one of the top areas of interest for energy harvesting in the power electronics world. This interest has especially peaked recently due to the increasing demand for a reliable source of renewable energy. In a recent study, the American Wind Energy Association (AWEA) ranked the U.S as the leading competitor in wind energy harvesting followed by Germany and Spain. Although the United States is the leading competitor in this area, no one has...
Show moreIn recent years, wind energy technology has become one of the top areas of interest for energy harvesting in the power electronics world. This interest has especially peaked recently due to the increasing demand for a reliable source of renewable energy. In a recent study, the American Wind Energy Association (AWEA) ranked the U.S as the leading competitor in wind energy harvesting followed by Germany and Spain. Although the United States is the leading competitor in this area, no one has been able successfully develop an efficient, low-cost AC/DC convertor for low power turbines to be used by the average American consumer. There has been very little research in low power AC/DC converters for low to medium power wind energy turbines for battery charging applications. Due to the low power coefficient of wind turbines, power converters are required to transfer the maximum available power at the highest efficiency. Power factor correction (PFC) and maximum power point tracking (MPPT) algorithms have been proposed for high power wind turbines. These turbines are out of the price range of what a common household can afford. They also occupy a large amount of space, which is not practical for use in one's home. A low cost AC/DC converter with efficient power transfer is needed in order to promote the use of cheaper low power wind turbines. Only MPPT is implemented in most of these low power wind turbine power converters. The concept of power factor correction with MPPT has not been completely adapted just yet. The research conducted involved analyzing the effect of power factor correction and maximum power point tracking algorithm in AC/DC converters for wind turbine applications. Although maximum power to the load is always desired, most converters only take electrical efficiency into consideration. However, not only the electrical efficiency must be considered, but the mechanical energy as well. If the converter is designed to look like a purely resistive load and not a switched load, a wind turbine is able to supply the maximum power with lower conduction loss at the input side due to high current spikes. Two power converters, VIENNA with buck converter and a Buck-boost converter, were designed and experimentally analyzed. A unique approach of controlling the MPPT algorithm through a conductance G for PFC is proposed and applied in the VIENNA topology. On the other hand, the Buck-boost only operates MPPT. With the same wind profile applied for both converters, an increase in power drawn from the input increased when PFC was used even when the power level was low. Both topologies present their own unique advantages. The main advantage for the VIENNA converter is that PFC allowed more power extraction from the turbine, increasing both electrical and mechanical efficiency. The buck-boost converter, on the other hand, presents a very low component count which decreases the overall cost and volume. Therefore, a small, cost-effective converter that maximizes the power transfer from a small power wind turbine to a DC load, can motivate consumers to utilize the power available from the wind.
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Date Issued
2009
Identifier
CFE0002730, ucf:48158
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0002730
PULSE FREQUENCY MODULATION ZCS FLYBACK CONVERTER IN INVERTER APPLICATIONS
Title
PULSE FREQUENCY MODULATION ZCS FLYBACK CONVERTER IN INVERTER APPLICATIONS.
Creator
Tian, Feng, Batarseh, Issa, University of Central Florida
Abstract / Description
Renewable energy source plays an important role in energy co-generation and distribution. A traditional solar-based inverter system has two stages cascaded, which has simpler controller but low efficiency. A new solar-based single-stage grid-connected inverter system can achieve higher efficiency by reducing the power semiconductor switching loss and output stable and synchronizing sinusoid current into the utility grid. In Chapter 1, the characteristic I-V and P-V curve of PV array has been...
Show moreRenewable energy source plays an important role in energy co-generation and distribution. A traditional solar-based inverter system has two stages cascaded, which has simpler controller but low efficiency. A new solar-based single-stage grid-connected inverter system can achieve higher efficiency by reducing the power semiconductor switching loss and output stable and synchronizing sinusoid current into the utility grid. In Chapter 1, the characteristic I-V and P-V curve of PV array has been illustrated. Based on prediction of the PV power capacity installed on the grid-connected and off-grid, the trends of grid-tied inverter for DG system have been analyzed. In Chapter 2, the topologies of single-phase grid-connect inverter system have been listed and compared. The key parameters of all these topologies are listed in a table in terms of topology, power decoupling, isolation, bi-directional/uni-directional, power rating, switching frequency, efficiency and input voltage. In Chapter 3, to reduce the capacitance of input filter, an active filter has been proposed, which will eliminate the 120/100Hz low frequency ripple from the PV array's output voltage completely. A feedforward controller is proposed to optimize the step response of PV array output voltage. A sample and hold also is used to provide the 120/100Hz low frequency decoupling between the controller of active filter and inverter stage. In Chapter 4, the single-stage inverter is proposed. Compared with conventional two-stage inverter, which has two high frequency switching stages cascaded, the single-stage inverter system increases the system efficiency by utilizing DC/DC converter to generate rectified sinusoid voltage. A transformer analysis is conducted for the single-stage inverter system, which proves the transformer has no low-frequency magnetic flux bias. To apply peak current mode control on single-stage inverter and get unified loop gain, adaptive slope compensation is also proposed for single-stage inverter. In Chapter 5, a digital controller for single-stage inverter is designed and optimized by the Matlab Control Toolbox. A Psim simulation verified the performance of the digital controller design. In Chapter 6, three bi-directional single-stage inverter topologies are proposed and compared. A conventional single-stage bi-directional inverter has certain shortcoming that cannot be overcome. A modular grid-connect micro-inverter system with dedicated reactive energy processing unit can overcome certain shortcoming and increase the system efficiency and reliability. A unique controller design is also proposed. In Chapter 7, a PFM ZCS flyback inverter system is invented. By using half-wave quasi-resonant ZCS flyback resonant converter and PFM control, this topology completely eliminates switching loss. A detailed mathematical analysis provides all the key parameters for the inverter design. As the inductance of transformer secondary side get smaller, the power stage transfer function of PFM ZCS flyback inverter system demonstrates nonlinearity. An optimized PFM ZCS flyback DC/DC converter design resolves this issue by introducing a MOSFET on the secondary side of transformer. In Chapter 8, experimental results of uni-direcitonal single-stage inverter with grid-connection, bi-directional single-stage inverter and single-stage PFM ZCS flyback inverter have been provided. Conclusions are given in Chapter 9.
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Date Issued
2009
Identifier
CFE0002664, ucf:48198
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0002664
DESIGN AND OPERATION OF STATIONARY DISTRIBUTED BATTERY MICRO-STORAGE SYSTEMS
Title
DESIGN AND OPERATION OF STATIONARY DISTRIBUTED BATTERY MICRO-STORAGE SYSTEMS.
Creator
Al-Haj Hussein, Ala, Batarseh, Issa, University of Central Florida
Abstract / Description
Due to some technical and environmental constraints, expanding the current electric power generation and transmission system is being challenged by even increasing the deployment of distributed renewable generation and storage systems. Energy storage can be used to store energy from utility during low-demand (off-peak) hours and deliver this energy back to the utility during high-demand (on-peak) hours. Furthermore, energy storage can be used with renewable sources to overcome some of their...
Show moreDue to some technical and environmental constraints, expanding the current electric power generation and transmission system is being challenged by even increasing the deployment of distributed renewable generation and storage systems. Energy storage can be used to store energy from utility during low-demand (off-peak) hours and deliver this energy back to the utility during high-demand (on-peak) hours. Furthermore, energy storage can be used with renewable sources to overcome some of their limitations such as their strong dependence on the weather conditions, which cannot be perfectly predicted, and their unmatched or out-of-synchronization generation peaks with the demand peaks. Generally, energy storage enhances the performance of distributed renewable sources and increases the efficiency of the entire power system. Moreover, energy storage allows for leveling the load, shaving peak demands, and furthermore, transacting power with the utility grid. This research proposes an energy management system (EMS) to manage the operation of distributed grid-tied battery micro-storage systems for stationary applications when operated with and without renewable sources. The term "micro" refers to the capacity of the energy storage compared to the grid capacity. The proposed management system employs four dynamic models; economic model, battery model, and load and weather forecasting models. These models, which are the main contribution of this research, are used in order to optimally control the operation of the micro-storage system (MSS) to maximize the economic return for the end-user when operated in an electricity spot market system.
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Date Issued
2011
Identifier
CFE0003964, ucf:48712
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003964
Ultra-Efficient Cascaded Buck-Boost Converter
Title
Ultra-Efficient Cascaded Buck-Boost Converter.
Creator
Ashok Pise, Anirudh, Batarseh, Issa, Mikhael, Wasfy, Sun, Wei, Kutkut, Nasser, University of Central Florida
Abstract / Description
This thesis presents various techniques to achieve ultra-high-efficiency for Cascaded-Buck-Boost converter. A rigorous loss model with component non linearity is developed and validated experimentally. An adaptive-switching-frequency control is discussed to optimize weighted efficiency. Some soft-switching techniques are discussed. A low-profile planar-nanocrystalline inductor is developed and various design aspects of core and copper design are discussed. Finite-element-method is used to...
Show moreThis thesis presents various techniques to achieve ultra-high-efficiency for Cascaded-Buck-Boost converter. A rigorous loss model with component non linearity is developed and validated experimentally. An adaptive-switching-frequency control is discussed to optimize weighted efficiency. Some soft-switching techniques are discussed. A low-profile planar-nanocrystalline inductor is developed and various design aspects of core and copper design are discussed. Finite-element-method is used to examine and visualize the inductor design. By implementing the above, a peak efficiency of over 99.2 % is achieved with a power density of 6 kW/L and a maximum profile height of 7 mm is reported. This converter finds many applications because of its versatility: allowing bidirectional power flow and the ability to step-up or step-down voltages in either direction.
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Date Issued
2017
Identifier
CFE0007277, ucf:52181
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007277
A NEW QUASI RESONANT DC-LINK FOR PHOTOVOLTAIC MICRO-INVERTERS
Title
A NEW QUASI RESONANT DC-LINK FOR PHOTOVOLTAIC MICRO-INVERTERS.
Creator
Grishina, Anna, Batarseh, Issa, Shen, Zheng, Kutkut, Nasser, University of Central Florida
Abstract / Description
PV Inverters have the task of tracking the maximum power point (MPP), and regulating the solar energy generation to this optimal operation point. The second task is the conversion of direct current produced by the solar modules into alternating current compatible with the grid.A new inverter approach such as a single phase micro inverter is emerging aimed to overcome some of the challenges of centralized inverters. As a counterpart to the central inverter, a micro inverter is a small compact...
Show morePV Inverters have the task of tracking the maximum power point (MPP), and regulating the solar energy generation to this optimal operation point. The second task is the conversion of direct current produced by the solar modules into alternating current compatible with the grid.A new inverter approach such as a single phase micro inverter is emerging aimed to overcome some of the challenges of centralized inverters. As a counterpart to the central inverter, a micro inverter is a small compact module attached directly to each solar panel.To provide for the constantly increasing demand for a small size, light weight and high efficiency micro inverter, soft switching power conversion technologies have been employed. The switching stress can be minimized by turning on/off each switch when the voltage across it or the current through it is zero at the switching transition. With the addition of auxiliary circuits such as auxiliary switches and LC resonant components the so called soft switching condition can be achieved for semiconductor devices.Four main purposes to investigate the soft switching technologies for single-phase micro-inverter are:(1) to improve overall efficiency by creating the favorable operating conditions for power devices using soft-switching techniques;(2) to shrink the reactive components by pushing the switching frequency to a higher range with decent efficiency.(3) to ensure soft switching does not exacerbate inverter performance, meaning all conventional PWM algorithms can be applied in order to meet IEEE standards.(4) to investigate which soft switching techniques offer the cheapest topology and control strategy as cost and simple control are crucial for low power inverter applications.An overview on the existing soft-switching inverter topologies for single phase inverter technology is summarized.A new quasi resonant DC link that allows for pulse- width- modulation (PWM) is presented in this thesis. The proposed quasi resonant DC link provides zero-voltage switching (ZVS) condition for the main devices by resonating the DC-link voltage to zero via three auxiliary switches and LC components. The operating principle and mode analysis are given. The simulation was carried out to verify the proposed soft switching technique. A 150W 120VAC single-phase prototype was built. The experimental results show that the soft switching for four main switches can be realized under different load conditions and the peak efficiency can reach 95.6%. The proposed quasi DC link can be applied to both single-phase and three-phase DC/AC micro inverter.In order to boost efficiency and increase power density it is important to evaluate the power loss mechanism in each stage of operation of the micro inverter. Using the datasheet parameters of the commercially available semiconductor switches, conduction and switching losses were estimated. This thesis presents a method to analyze power losses of the new resonant DC link inverter which alleviates topology optimization and MOSFET selection. An analytical, yet simple model for calculating the conduction and switching losses was developed. With this model a rough calculation of efficiency can be done, which helps to speed up the design process and to increase efficiency.
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Date Issued
2012
Identifier
CFE0004379, ucf:49397
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0004379
Virtual resistance based DC-link voltage regulation for Microgrid DG inverters.
Title
Virtual resistance based DC-link voltage regulation for Microgrid DG inverters.
Creator
Shinde, Siddhesh, Batarseh, Issa, Mikhael, Wasfy, Kutkut, Nasser, University of Central Florida
Abstract / Description
This research addresses the practical issues faced by Microgrid Distributed Generation (DG) inverters when operated in islanded mode. A Microgrid (MG) is an interconnection of domestic distributed loads and low voltage distributed energy sources such as micro-turbine, wind-turbine, PVs and storage devices. These energy sources are power limited in nature and constrain the operation of DG inverters to which they are coupled. DG inverters operated in islanded mode should maintain the power...
Show moreThis research addresses the practical issues faced by Microgrid Distributed Generation (DG) inverters when operated in islanded mode. A Microgrid (MG) is an interconnection of domestic distributed loads and low voltage distributed energy sources such as micro-turbine, wind-turbine, PVs and storage devices. These energy sources are power limited in nature and constrain the operation of DG inverters to which they are coupled. DG inverters operated in islanded mode should maintain the power balance between generation and demand. If DG inverter operating in islanded mode drains its source power below a certain limit or if it is incapable of supplying demanded power due to its hardware rating, it turns on its safety mechanism and isolates itself from the MG. This, in turn, increases the power demand on the rest of the DG units and can have a catastrophic impact on the viability of the entire system. This research presents a Virtual Resistance based DC Link Voltage Regulation technique which will allow DG inverters to continue to source their available power even when the power demand by the load is higher than their capacity without shutting off and isolating from the MG.
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Date Issued
2016
Identifier
CFE0006503, ucf:51403
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0006503

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