Mr. Ahmed A S Mohamed is a Ph.D. student in Electrical and Computer Engineering in the Energy Systems Research Laboratory at Florida International University. He received his Bs.C and M.S. degrees in Electrical Engineering from , Zagazig University, Egypt. His research focus is on control and power electronic of PV applications and wireless power transfer for electric vehicle applications. Supervisors: PROF. OSAMA MOHAMED Phone: 7866603760 Address: Miami, Florida, USA
In this paper, a new bi-directional wireless power transfer (BWPT) charging and discharging conce... more In this paper, a new bi-directional wireless power transfer (BWPT) charging and discharging concept is analyzed for its feasibility in integration at traffic signals. Classified as quasi-dynamic WPT (QDWPT), a string of coils are proposed to be installed beneath the road surface to provide grid-to-vehicle (G2V) and vehicle-to-grid (V2G) services to battery electric vehicles (BEVs) while stopped. An experimentally verified lithium ion battery array and BIWPT system is combined to provide a comprehensive simulation under 3 proposed scenarios. First, 4 fixed SAE J2954 standardized WPT charging levels are evaluated under a FTP-72 city driving profile. Second, a variable charging scenario autonomously adjusts the charging level based on the BEV state-of-charge (SOC). Third, an algorithm is proposed to toggle between charging and discharging based on the BEV psychological and grid retail price to evaluate V2G service viability. For each scenario, a comparison over the maximum driving range per drive cycle and range gained for each consumed kWh is quantified. Moreover, the effect of WPT coil misalignment over the driving performance is investigated and evaluated. This study concludes that, QDWPT at traffic signals is a promising solution to substantially extend the driving range and operating time for city driving especially at high charging levels.
Electromagnetic emission produced by high frequency switching current of inductive components has... more Electromagnetic emission produced by high frequency switching current of inductive components has an adverse effect on sensitive devices in power converters. This paper investigates the effect of components placement on the radiated emissions in printed circuit board (PCB). The goal of this research is to minimize the electromagnetic interference (EMI) on susceptible devices. The optimum design for the location and orientation of the components on the PCB was achieved by a 3D-FE analysis and Genetic Algorithms (GA). A comparison between the optimum and non-optimum PCB designs were simulated and experimentally tested.
Severe power quality problems, due to nonlinear and dynamic loads, have been reported in recent y... more Severe power quality problems, due to nonlinear and dynamic loads, have been reported in recent years. These issues become more significant in high penetration of power electronics devices and renewable power systems. Thus, this paper deals with the control design of the shunt active power filter (SAPF), as one of the outstanding solution for these issues. The paper proposes an adaptive reference current detection technique for SAPF applications. The proposed technique is based on the adaptive interference cancelling (AIC) theory. The way to design and evaluate the performance of the proposed adaptive filter, is explained in details. The proposed methodology and design is simulated and tested in MatLab software. The results certified the ability of the technique to extract the compensating current in case of stationary and non-stationary situations.
This book presents a detailed study of photovoltaic water pumping systems. Each component in the ... more This book presents a detailed study of photovoltaic water pumping systems. Each component in the system is studied separately and stands on its types and design approaches. After this through study of these parts, the best one from each of them is chosen to achieve a simple and efficient system. Then a complete modeling and simulation for the whole system is done using the commercial software MATLAB. The simulation is used to study the performance of photovoltaic pumping system uses PM DC motor and positive displacement pump, under different environmental conditions. Also, this thesis studies the effect of parasitic resistances and diode ideality factor on characterization parameters of photovoltaic modules. Which are helpful for module manufactures for improving the manufacturing process. Besides the system contains a control system to keep the module operates at its maximum power point (Maximum power point tracker MPPT) to improve the system efficiency and decrease its cost. Thesi...
COMPEL International Journal of Computations and Mathematics in Electrical
Electromagnetic emission produced by high frequency switching current of inductive components has... more Electromagnetic emission produced by high frequency switching current of inductive components has an adverse effect on the sensitive devices in power converters. Accurate modeling of the power electronic converter can be developed using a quasi-static field analysis. This paper investigates the effect of components placement on the radiated emissions of the printed circuit board (PCB) of power converters. The goal of this research is to minimize the electromagnetic interference (EMI) on sensitive devices and components on the PCB. The optimum design for the location and orientation of the components on the PCB was achieved by a combination of 3D-FE analysis and Genetic Algorithms (GA). A comparison between the optimum and non-optimum PCB designs were simulated and experimentally tested to verify the advantages of the proposed design technique.
This paper presents a performance evaluation procedure for an inductive wireless power transfer (... more This paper presents a performance evaluation procedure for an inductive wireless power transfer (WPT) system with a parallel-parallel compensation network. The effect of the WPT system design parameters on its efficiency is investigated. The WPT system is modeled using a 3D electromagnetic field technique coupled with circuit simulation. The 3D finite element (3DFE) model is created and a MATLAB-FEA automated routine configures the model parameters. Moreover, the paper proposes a mathematical model for efficiency assessment purposes. The results from the 3DFE and mathematical model are compared with a Matlab Simulink model results for the same system. The results show a good agreement between all the models.
— This paper presents a new methodology of active power flow control for a bidirectional inductiv... more — This paper presents a new methodology of active power flow control for a bidirectional inductive wireless power transfer (BIWPT) system in electric vehicle (EV) ancillary services based on the system analytical model. The controller exists on the vehicle side to consider the EV's owner's desire for providing energy to the other sources. The owner is able to choose between three different control modes; Charge, Discharge and Abstain (no interaction). The controller considers the EV's battery state-of-charge (SOC) which is provided by the battery management system (BMS). The control parameters are predicted based on a simple and an accurate analytical model for the BIWPT system. The misalignment effect on the controller performance is considered by adaptively estimating the wireless pads mutual inductance. The proposed controller is implemented and tested by means of simulations and experiments for stationary and quasi-dynamic wireless power transfer situations.
— Flexible, automatic, reliable and safe charging and discharging system for electric vehicle (EV... more — Flexible, automatic, reliable and safe charging and discharging system for electric vehicle (EV) and hybrid electric vehicle (HEV) is crucial in vehicle-to-grid (V2G) operation. The bidirectional inductive wireless power transfer system (BIWPTS) is ideal solution in this situation. With authentic power flow models for the BIWPTS in hand, designers and operators can predict, optimize and analyze the interaction performance between EV and the grid. Thus, this paper presents harmonics-based theoretical power-flow model for BIWPTS for charging and discharging EVs in V2G applications. The proposed model provides accurate estimation for the active and reactive power flow during V2G and grid-to-vehicle (G2V) modes. Moreover, the impact of the circuit losses and harmonics, due to the high frequency (HF) power inverters, on the power flow performance, is investigated. This effect is stated mathematically by four novel power flow criteria formulas. Also, new conditions for achieving maximum active and reactive power, and unity and zero power factor system operation, are developed. The sensitivity of the circuit performance to the variation of its parameters, has been studied. For validation purposes, computer-based model and experimental platform of BIWPTS for EV applications are developed and tested. The comparison between the theoretical, simulation and experimental results verified the proposed models and analysis.
This paper presents a clear methodology for achieving the optimum design of LCL bidirectional ind... more This paper presents a clear methodology for achieving the optimum design of LCL bidirectional inductive wireless power transfer system (BIWPTS) for electric vehicle (EV) applications. The proposed strategy depends on electromagnetic field computations joined with analytical models. A three dimensional finite element model (3D-FEM) for 8 kW polarized doubleD (DD) power pad was modeled, optimized and built. Moreover, the choice of the power factor correction and impedance matching elements was investigated. Following the proposed design considerations, a BIWPTS model was developed in MatLab Simulink and its outcomes were compared with the theoretical model results. Additionally, a small scale prototype was assembled using the same design with reduced dc voltage levels. The models were tested during charging and discharging operation and good correlation were seen between every one of them.
—This paper presents a cost effective control algorithm for standalone batteryless photovoltaic (... more —This paper presents a cost effective control algorithm for standalone batteryless photovoltaic (PV) systems. The control is driven by a fuzzy-based maximum power point tracker which has the capabilities to maintain high-energy conversion efficiency under different weather and load conditions. General design considerations are presented based on the linearization of the dynamic model of the entire system which consists of PV panel, Cuk converter, and motor load. For our particular fuzzy-MPPT controller , these design considerations are combined with an artificial intelligent technique to achieve the optimum control design. Furthermore , the developed control algorithm has voltage regulation capability to protect the load from overvoltage during light load conditions and a fast digital overload protection. The transient and steady-state performance of the entire system was modeled by a nonlinear state-space representation. The proposed control is simulated in MATLAB and experimentally tested under the fast variation of climatic conditions for verification purposes A very good agreement has been shown between theoretical, simulations, and experimental results Index Terms—Design, dynamic modeling, fuzzy logic control (FLC), genetic algorithms (GA), maximum power point tracker (MPPT), pumping system, small signal analysis, state-space model.
This paper investigates the effect of changing cell temperature and solar irradiance on the choic... more This paper investigates the effect of changing cell temperature and solar irradiance on the choice and design of different topologies of DCeDC converter commonly used in photovoltaic (PV) systems. Under fluctuation of climatic conditions, the maximum power point (MPP) of PV generator will change. The maximum power point tracker (MPPT) must adjust the converter duty cycle to track the new MPP. Thus the converter must be chosen to be able to match the MPP under different atmospheric conditions. In addition, when the duty cycle changes as a result of changed climatic conditions, the boundary of the converter design parameters will change. So these parameters must be chosen to achieve the highest performance at all. The study shows that, only the buckeboost and the C 0 uk converter are capable of achieving the optimal operation regardless of the load value. And for a permanent operation in continuous conduction mode the filter inductance for all converter topologies must be greater than the maximum value of boundary inductance. Also in order to limit the ripple in the output voltage below a certain value, the filter capacitance must be larger than the maximum value of boundary capacitance. Crown
This paper studies the effect of the location of stator inter-turn short-circuit (ITSC) faults on... more This paper studies the effect of the location of stator inter-turn short-circuit (ITSC) faults on the squirrel-cage induction machine (IM) model parameter's. The ITSC location can be affected in three different ways, however we studied two of them: the physical placement for a fixed number of turns fault and the variation of the number of turns short-circuited. Both different cases will influence the rotating magnetic field shape in the airgap and thus the stator and rotor parameters. Two investigations are conducted, the former one is a finite element analysis (FEA) of four location cases of equal severity factor ITSC in the IM phase " a ". The latter is a theoretical and mathematical analysis where the ITSC is modeled by a step-down auto-transformer in the faulty circuit. The results of the FEA corroborate that different locations impacts the IM parameters, however, the effect is not substantial and the theoretical model indicates how the parameters vary with the fault. Moreover, a comparative study of two IM damaged models that present different approach to the stator leakage inductance is performed. The asymmetric mathematical model is presented, simulated and experimentally compared. Index Terms— Fault detection and identification, finite element analysis, induction machines, inter-turn short-circuit location.
—This paper presents an improved complex-vector dynamic model for a three-phase induction machine... more —This paper presents an improved complex-vector dynamic model for a three-phase induction machine (IM) with stator inter-turn short-circuit (ITSC) fault. The paper proposes an accurate and meaningful approach to the faulty stator leakage inductance and describes a non-linear phenomenon in the faulty circuit. The asymmetric model is developed in detail and represented in state-space (SS) form with the flux-linkages as the SS variable. Based on the proposed model, steady-state complex-vector, operational, and sequence component equivalent circuits (EC) are derived for fault detection and identification (FDI) purposes. For reasons of verification, the model is simulated in MatLab environment and experimentally corroborated for a 1HP three-phase squirrel-cage IM. The simulations and experiments are compared at no-load and loading condition for both transient and steady-state response. The permanent regime analysis studies the model with respect to the fault severity factor, fault resistance and load variation. The proposed model shows high correlation with the experimental results. Index Terms— Complex-vector, fault detection and identification, induction motor, inter-turn short-circuit fault, state-space modeling.
In this paper, a new bi-directional wireless power transfer (BWPT) charging and discharging conce... more In this paper, a new bi-directional wireless power transfer (BWPT) charging and discharging concept is analyzed for its feasibility in integration at traffic signals. Classified as quasi-dynamic WPT (QDWPT), a string of coils are proposed to be installed beneath the road surface to provide grid-to-vehicle (G2V) and vehicle-to-grid (V2G) services to battery electric vehicles (BEVs) while stopped. An experimentally verified lithium ion battery array and BIWPT system is combined to provide a comprehensive simulation under 3 proposed scenarios. First, 4 fixed SAE J2954 standardized WPT charging levels are evaluated under a FTP-72 city driving profile. Second, a variable charging scenario autonomously adjusts the charging level based on the BEV state-of-charge (SOC). Third, an algorithm is proposed to toggle between charging and discharging based on the BEV psychological and grid retail price to evaluate V2G service viability. For each scenario, a comparison over the maximum driving range per drive cycle and range gained for each consumed kWh is quantified. Moreover, the effect of WPT coil misalignment over the driving performance is investigated and evaluated. This study concludes that, QDWPT at traffic signals is a promising solution to substantially extend the driving range and operating time for city driving especially at high charging levels.
Electromagnetic emission produced by high frequency switching current of inductive components has... more Electromagnetic emission produced by high frequency switching current of inductive components has an adverse effect on sensitive devices in power converters. This paper investigates the effect of components placement on the radiated emissions in printed circuit board (PCB). The goal of this research is to minimize the electromagnetic interference (EMI) on susceptible devices. The optimum design for the location and orientation of the components on the PCB was achieved by a 3D-FE analysis and Genetic Algorithms (GA). A comparison between the optimum and non-optimum PCB designs were simulated and experimentally tested.
Severe power quality problems, due to nonlinear and dynamic loads, have been reported in recent y... more Severe power quality problems, due to nonlinear and dynamic loads, have been reported in recent years. These issues become more significant in high penetration of power electronics devices and renewable power systems. Thus, this paper deals with the control design of the shunt active power filter (SAPF), as one of the outstanding solution for these issues. The paper proposes an adaptive reference current detection technique for SAPF applications. The proposed technique is based on the adaptive interference cancelling (AIC) theory. The way to design and evaluate the performance of the proposed adaptive filter, is explained in details. The proposed methodology and design is simulated and tested in MatLab software. The results certified the ability of the technique to extract the compensating current in case of stationary and non-stationary situations.
This book presents a detailed study of photovoltaic water pumping systems. Each component in the ... more This book presents a detailed study of photovoltaic water pumping systems. Each component in the system is studied separately and stands on its types and design approaches. After this through study of these parts, the best one from each of them is chosen to achieve a simple and efficient system. Then a complete modeling and simulation for the whole system is done using the commercial software MATLAB. The simulation is used to study the performance of photovoltaic pumping system uses PM DC motor and positive displacement pump, under different environmental conditions. Also, this thesis studies the effect of parasitic resistances and diode ideality factor on characterization parameters of photovoltaic modules. Which are helpful for module manufactures for improving the manufacturing process. Besides the system contains a control system to keep the module operates at its maximum power point (Maximum power point tracker MPPT) to improve the system efficiency and decrease its cost. Thesi...
COMPEL International Journal of Computations and Mathematics in Electrical
Electromagnetic emission produced by high frequency switching current of inductive components has... more Electromagnetic emission produced by high frequency switching current of inductive components has an adverse effect on the sensitive devices in power converters. Accurate modeling of the power electronic converter can be developed using a quasi-static field analysis. This paper investigates the effect of components placement on the radiated emissions of the printed circuit board (PCB) of power converters. The goal of this research is to minimize the electromagnetic interference (EMI) on sensitive devices and components on the PCB. The optimum design for the location and orientation of the components on the PCB was achieved by a combination of 3D-FE analysis and Genetic Algorithms (GA). A comparison between the optimum and non-optimum PCB designs were simulated and experimentally tested to verify the advantages of the proposed design technique.
This paper presents a performance evaluation procedure for an inductive wireless power transfer (... more This paper presents a performance evaluation procedure for an inductive wireless power transfer (WPT) system with a parallel-parallel compensation network. The effect of the WPT system design parameters on its efficiency is investigated. The WPT system is modeled using a 3D electromagnetic field technique coupled with circuit simulation. The 3D finite element (3DFE) model is created and a MATLAB-FEA automated routine configures the model parameters. Moreover, the paper proposes a mathematical model for efficiency assessment purposes. The results from the 3DFE and mathematical model are compared with a Matlab Simulink model results for the same system. The results show a good agreement between all the models.
— This paper presents a new methodology of active power flow control for a bidirectional inductiv... more — This paper presents a new methodology of active power flow control for a bidirectional inductive wireless power transfer (BIWPT) system in electric vehicle (EV) ancillary services based on the system analytical model. The controller exists on the vehicle side to consider the EV's owner's desire for providing energy to the other sources. The owner is able to choose between three different control modes; Charge, Discharge and Abstain (no interaction). The controller considers the EV's battery state-of-charge (SOC) which is provided by the battery management system (BMS). The control parameters are predicted based on a simple and an accurate analytical model for the BIWPT system. The misalignment effect on the controller performance is considered by adaptively estimating the wireless pads mutual inductance. The proposed controller is implemented and tested by means of simulations and experiments for stationary and quasi-dynamic wireless power transfer situations.
— Flexible, automatic, reliable and safe charging and discharging system for electric vehicle (EV... more — Flexible, automatic, reliable and safe charging and discharging system for electric vehicle (EV) and hybrid electric vehicle (HEV) is crucial in vehicle-to-grid (V2G) operation. The bidirectional inductive wireless power transfer system (BIWPTS) is ideal solution in this situation. With authentic power flow models for the BIWPTS in hand, designers and operators can predict, optimize and analyze the interaction performance between EV and the grid. Thus, this paper presents harmonics-based theoretical power-flow model for BIWPTS for charging and discharging EVs in V2G applications. The proposed model provides accurate estimation for the active and reactive power flow during V2G and grid-to-vehicle (G2V) modes. Moreover, the impact of the circuit losses and harmonics, due to the high frequency (HF) power inverters, on the power flow performance, is investigated. This effect is stated mathematically by four novel power flow criteria formulas. Also, new conditions for achieving maximum active and reactive power, and unity and zero power factor system operation, are developed. The sensitivity of the circuit performance to the variation of its parameters, has been studied. For validation purposes, computer-based model and experimental platform of BIWPTS for EV applications are developed and tested. The comparison between the theoretical, simulation and experimental results verified the proposed models and analysis.
This paper presents a clear methodology for achieving the optimum design of LCL bidirectional ind... more This paper presents a clear methodology for achieving the optimum design of LCL bidirectional inductive wireless power transfer system (BIWPTS) for electric vehicle (EV) applications. The proposed strategy depends on electromagnetic field computations joined with analytical models. A three dimensional finite element model (3D-FEM) for 8 kW polarized doubleD (DD) power pad was modeled, optimized and built. Moreover, the choice of the power factor correction and impedance matching elements was investigated. Following the proposed design considerations, a BIWPTS model was developed in MatLab Simulink and its outcomes were compared with the theoretical model results. Additionally, a small scale prototype was assembled using the same design with reduced dc voltage levels. The models were tested during charging and discharging operation and good correlation were seen between every one of them.
—This paper presents a cost effective control algorithm for standalone batteryless photovoltaic (... more —This paper presents a cost effective control algorithm for standalone batteryless photovoltaic (PV) systems. The control is driven by a fuzzy-based maximum power point tracker which has the capabilities to maintain high-energy conversion efficiency under different weather and load conditions. General design considerations are presented based on the linearization of the dynamic model of the entire system which consists of PV panel, Cuk converter, and motor load. For our particular fuzzy-MPPT controller , these design considerations are combined with an artificial intelligent technique to achieve the optimum control design. Furthermore , the developed control algorithm has voltage regulation capability to protect the load from overvoltage during light load conditions and a fast digital overload protection. The transient and steady-state performance of the entire system was modeled by a nonlinear state-space representation. The proposed control is simulated in MATLAB and experimentally tested under the fast variation of climatic conditions for verification purposes A very good agreement has been shown between theoretical, simulations, and experimental results Index Terms—Design, dynamic modeling, fuzzy logic control (FLC), genetic algorithms (GA), maximum power point tracker (MPPT), pumping system, small signal analysis, state-space model.
This paper investigates the effect of changing cell temperature and solar irradiance on the choic... more This paper investigates the effect of changing cell temperature and solar irradiance on the choice and design of different topologies of DCeDC converter commonly used in photovoltaic (PV) systems. Under fluctuation of climatic conditions, the maximum power point (MPP) of PV generator will change. The maximum power point tracker (MPPT) must adjust the converter duty cycle to track the new MPP. Thus the converter must be chosen to be able to match the MPP under different atmospheric conditions. In addition, when the duty cycle changes as a result of changed climatic conditions, the boundary of the converter design parameters will change. So these parameters must be chosen to achieve the highest performance at all. The study shows that, only the buckeboost and the C 0 uk converter are capable of achieving the optimal operation regardless of the load value. And for a permanent operation in continuous conduction mode the filter inductance for all converter topologies must be greater than the maximum value of boundary inductance. Also in order to limit the ripple in the output voltage below a certain value, the filter capacitance must be larger than the maximum value of boundary capacitance. Crown
This paper studies the effect of the location of stator inter-turn short-circuit (ITSC) faults on... more This paper studies the effect of the location of stator inter-turn short-circuit (ITSC) faults on the squirrel-cage induction machine (IM) model parameter's. The ITSC location can be affected in three different ways, however we studied two of them: the physical placement for a fixed number of turns fault and the variation of the number of turns short-circuited. Both different cases will influence the rotating magnetic field shape in the airgap and thus the stator and rotor parameters. Two investigations are conducted, the former one is a finite element analysis (FEA) of four location cases of equal severity factor ITSC in the IM phase " a ". The latter is a theoretical and mathematical analysis where the ITSC is modeled by a step-down auto-transformer in the faulty circuit. The results of the FEA corroborate that different locations impacts the IM parameters, however, the effect is not substantial and the theoretical model indicates how the parameters vary with the fault. Moreover, a comparative study of two IM damaged models that present different approach to the stator leakage inductance is performed. The asymmetric mathematical model is presented, simulated and experimentally compared. Index Terms— Fault detection and identification, finite element analysis, induction machines, inter-turn short-circuit location.
—This paper presents an improved complex-vector dynamic model for a three-phase induction machine... more —This paper presents an improved complex-vector dynamic model for a three-phase induction machine (IM) with stator inter-turn short-circuit (ITSC) fault. The paper proposes an accurate and meaningful approach to the faulty stator leakage inductance and describes a non-linear phenomenon in the faulty circuit. The asymmetric model is developed in detail and represented in state-space (SS) form with the flux-linkages as the SS variable. Based on the proposed model, steady-state complex-vector, operational, and sequence component equivalent circuits (EC) are derived for fault detection and identification (FDI) purposes. For reasons of verification, the model is simulated in MatLab environment and experimentally corroborated for a 1HP three-phase squirrel-cage IM. The simulations and experiments are compared at no-load and loading condition for both transient and steady-state response. The permanent regime analysis studies the model with respect to the fault severity factor, fault resistance and load variation. The proposed model shows high correlation with the experimental results. Index Terms— Complex-vector, fault detection and identification, induction motor, inter-turn short-circuit fault, state-space modeling.
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Papers by Ahmed A S Mohamed