Adel Gastli
Qatar University, Electrical Engineering, Faculty Member
The elimination of the transformer in solar photovoltaic inverters has reduced the size, the weight and the losses in the system. On the other hand, the galvanic connection between the DC source and the grid generates leakage current... more
The elimination of the transformer in solar photovoltaic inverters has reduced the size, the weight and the losses in the system. On the other hand, the galvanic connection between the DC source and the grid generates leakage current through the earth parasitic capacitance. The leakage current depends on both the inverter topology and the control strategy. Among the existing inverters is the Highly Efficient and Reliable Inverter Concept (HERIC) topology that has low leakage current level and high efficiency. However, this topology suffers from low frequency harmonics and current zero crossings distortion s . To eliminate these harmonics and distortions, a new transformerless inverter is proposed. The design is a conventional full bridge inverter with an extra AC bypass. The bypass branch disconnects the inverter from the grid during the freewheeling period. Simulation results indicate that the zero crossings distortions are totally eliminated and that the low frequency harmoni...
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This paper focuses on a MATLAB/Simulink model of a photovoltaic cell. This model is based on mathematical equations and is described through an equivalent circuit including a photocurrent source, a diode, a series resistor and a shunt... more
This paper focuses on a MATLAB/Simulink model of a photovoltaic cell. This model is based on mathematical equations and is described through an equivalent circuit including a photocurrent source, a diode, a series resistor and a shunt resistor.The developed model allows the prediction of PV cell behavior under different physical and environmental parameters. The model can also be used to extract the physical parameters for a given solar PV cell as a function of temperature and solar radiation. In addition, this study outlines the working principle of PV module as well as PV array.In order to validate the developed model, an experimental test bench was built and the obtained results exhibited a good agreement with the simulation ones.
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When a galvanic connection between the grid and the PV array is made, a common-mode voltage exists that generates common-mode currents. These common-mode currents may produce electromagnetic interferences, grid current distortion and... more
When a galvanic connection between the grid and the PV array is made, a common-mode voltage exists that generates common-mode currents. These common-mode currents may produce electromagnetic interferences, grid current distortion and additional losses in the system. Therefore, to avoid the leakage currents that would penalize the transformerless power chains, it is worth focusing on topologies that do not generate common-mode currents. Some topologies available in the market touch more or less such a crucial ...
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This paper is a review of axial-field electrical machines, which were at the origin of the invention of electrical machines such as the famous Faraday’s disk. The different configurations of the axial-field machines are presented along... more
This paper is a review of axial-field electrical machines, which were at the origin of the invention of electrical machines such as the famous Faraday’s disk. The different configurations of the axial-field machines are presented along with their advantageous key steady state characteristics such as high efficiency and high power to weight ratio. The differences between axial-field machines and conventional radial-field machines are discussed. The disc-type axial-field electrical machines with permanent-magnet excitation seem to be among the best designs in terms of compactness, suitable shape, robustness, and electric characteristics. Axial-field machines are expected to be used in a large number of applications in the future owing to their special features and distinct advantages compared to conventional radial-field machines.
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Device mobility in dense Wi-Fi networks offers several challenges. Two well-known problems related to device mobility are handover prediction and access point selection. Due to the complex nature of the radio environment, analytical... more
Device mobility in dense Wi-Fi networks offers several challenges. Two well-known problems related to device mobility are handover prediction and access point selection. Due to the complex nature of the radio environment, analytical models may not characterize the wireless channel, which makes the solution of these problems very difficult. Recently, cognitive network architectures using sophisticated learning techniques are increasingly being applied to such problems. In this paper, we propose data-driven machine learning (ML) schemes to efficiently solve these problems in wireless LAN (WLAN) networks. The proposed schemes are evaluated and results are compared with traditional approaches to the aforementioned problems. The results report significant improvement in network performance by applying the proposed schemes. The proposed scheme for handover prediction outperforms traditional methods i.e. received signal strength method and traveling distance method by reducing the number o...
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In this paper, an energy management (EM) controller capable of operating in real-time and its verification in Controller Hardware in Loop (CHIL) is proposed. A coordinated multi-agent system-based optimization scheme is developed for the... more
In this paper, an energy management (EM) controller capable of operating in real-time and its verification in Controller Hardware in Loop (CHIL) is proposed. A coordinated multi-agent system-based optimization scheme is developed for the energy management for EV integration. The real-time simulation testbed is developed with Typhoon HIL 602+ unit interfaced to RTDS. The Typhoon HIL unit emulates an EV and the RTDS mimics the grid. The EM controller is developed in Java Agent Development Framework (JADE) and it is interfaced to the testbed through Ethernet (Socket) protocol. The results presented in this paper validate the real-time operation of the controller and the cost optimization at the workplace microgrid.
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We consider multiple source nodes (consumers) communicating wirelessly their energy demands to the meter data-management system (MDMS) over the subarea gateway(s). We quantify the impacts of passive and active security attacks on the... more
We consider multiple source nodes (consumers) communicating wirelessly their energy demands to the meter data-management system (MDMS) over the subarea gateway(s). We quantify the impacts of passive and active security attacks on the wireless communications system's reliability and security as well as the energy-demand estimation-error cost in dollars paid by the utility. We adopt a multiple-input multiple-output multi-antenna-eavesdropper (MIMOME) wiretap channel model. To secure the MIMO wireless communication system, the legitimate nodes generate artificial noise (AN) vectors to mitigate the effect of the passive eavesdropping attacks. In addition, we propose a redundant design where multiple gateways are assumed to coexist in each subarea to forward the consumers' energy-demand messages. We quantify the redundant designs impact on the communication reliability between the consumers and the MDMS and on the energy-demand estimation-error cost.
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This paper presents a novel modeling technique of electric appliances using Matlab/Simulink based on their actual measured current waveforms. Home appliances were used as the study case, but the proposed approach can be applied to any... more
This paper presents a novel modeling technique of electric appliances using Matlab/Simulink based on their actual measured current waveforms. Home appliances were used as the study case, but the proposed approach can be applied to any electric appliance as long as the supply voltage is maintained constant. In the proposed method, the measured current waveform is split into two parts: transient and steady state. Each part is stored in one data vector. The transient is stored in a long vector while the steady state is represented by one cycle only (e.g. 20 ms for 50 Hz). When the appliance is switched on, the transient data vector is used during the transient period only and then the steady-state data vector is repeated every supply cycle indefinitely until the appliance is switched off or the simulation is terminated. Compared to previously published methods, the proposed method is much more simple and accurate since it is based on the actual current waveform and not on any mathematical approximation or curve fitting. Finally, the created library of models in this study will be very useful for researchers when designing energy management.
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6 Several potential benefits to the quality and relia bility of delivered power can be attained with the installation of distributed generation units. To ta ke 7 full advantage of these benefits, it is essential t o place optimally sized... more
6 Several potential benefits to the quality and relia bility of delivered power can be attained with the installation of distributed generation units. To ta ke 7 full advantage of these benefits, it is essential t o place optimally sized distributed generation unit s a appropriate locations. Otherwise, their 8 installation could provoke negative effects to powe r quality and system operation. Over the years, var ious powerful optimization tools were 9 developed for optimal integration of distributed ge neration. Therefore, optimization techniques are co ntinuously evolving and have been recently the 10 focus of many new studies. This paper reviews recen t optimization methods applied to solve the problem of placement and sizing of distributed 11 generation units from renewable energy sources base d on a classification of the most recent and highly cited papers. In addition, this paper analyses 12 the environmental, economic, technological, technic al, and regulatory drivers that hav...
This paper proposes a bidirectional three phase single stage ac-dc converter for applications like Electric Vehicle (EV) chargers. AC side of the proposed converter consists of current fed half bridge converter for each of the three... more
This paper proposes a bidirectional three phase single stage ac-dc converter for applications like Electric Vehicle (EV) chargers. AC side of the proposed converter consists of current fed half bridge converter for each of the three phases and the DC side has three phase full bridge converter. The primary and secondary side of the converter are connected through star connection of high frequency transformer. The proposed converter achieves zero current switching (ZCS) of primary side switches and zero voltage switching (ZVS) for secondary side devices, while feeding power from grid to the dc side. The converter has soft switching on the primary side switches when transferring power from the dc side to the grid. The paper also presents a novel modulation and control scheme for the bidirectional power flow. The converter is evaluated using PSIM simulation tool for its operation in all the four quadrants of the PQ plot. The design of the converter, control strategy and the results are presented for a 10KVA converter for EV charger.
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Abstract: Finding the most appropriate configuration of series-parallel connections of PV units to make a PV array is a key issue for obtaining a PV system with maximum generated power. In most cases, a PV array is constructed from a... more
Abstract: Finding the most appropriate configuration of series-parallel connections of PV units to make a PV array is a key issue for obtaining a PV system with maximum generated power. In most cases, a PV array is constructed from a combination of standard PV units (solar cells or panels) connected in series and/or in parallel to obtain the desired power, voltage and current ratings. However, the non-linear behaviour a solar cells or panels exhibits as a function of internal physical parameters and optical irradiance and ...
Batteries are combinations of electrochemical cells that generate electricity to power electrical devices. Batteries are continuously converting chemical energy to electrical energy, and require appropriate maintenance to provide maximum... more
Batteries are combinations of electrochemical cells that generate electricity to power electrical devices. Batteries are continuously converting chemical energy to electrical energy, and require appropriate maintenance to provide maximum efficiency. Management systems having specialized monitoring features; such as charge controlling mechanisms and temperature regulation are used to prevent health, safety, and property hazards that complement the use of batteries. These systems utilize measures of merit to regulate battery performances. Figures such as the state-of-health (SOH) and state-of-charge (SOC) are used to estimate the performance and state of the battery. In this paper, we propose an intelligent method to investigate the aforementioned parameters using a data-driven approach. We use a machine learning algorithm that extracts significant features from the discharge curves to estimate these parameters. Extensive simulations have been carried out to evaluate the performance o...
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Energy efficiency is a key to reduced carbon footprint, savings on energy bills, and sustainability for future generations. For instance, in hot climate countries such as Qatar, buildings are high energy consumers due to air conditioning... more
Energy efficiency is a key to reduced carbon footprint, savings on energy bills, and sustainability for future generations. For instance, in hot climate countries such as Qatar, buildings are high energy consumers due to air conditioning that resulted from high temperatures and humidity. Optimizing the building energy management system will reduce unnecessary energy consumptions, improve indoor environmental conditions, maximize building occupant’s comfort, and limit building greenhouse gas emissions. However, lowering energy consumption cannot be done despite the occupants’ comfort. Solutions must take into account these tradeoffs. Conventional Building Energy Management methods suffer from a high dimensional and complex control environment. In recent years, the Deep Reinforcement Learning algorithm, applying neural networks for function approximation, shows promising results in handling such complex problems. In this work, a Deep Reinforcement Learning agent is proposed for contro...
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Recently, electric vehicles (EVs) have become an increasingly important topic in the field of sustainable transportation research, alongside distributed generation, reactive power compensation, charging optimization, and control. The... more
Recently, electric vehicles (EVs) have become an increasingly important topic in the field of sustainable transportation research, alongside distributed generation, reactive power compensation, charging optimization, and control. The process of loading on existing power system infrastructures with increasing demand requires appropriate impact indices to be analyzed. This paper studies the impact of integrating electric vehicle charging stations (EVCSs) into a residential distribution network. An actual case study is modeled to acquire nodal voltages and feeder currents. The model obtains the optimal integration of solar photovoltaic (PV) panels with charging stations while considering reactive power compensation. The impact of EV integration for the case study results in two peaks, which show a 6.4% and 17% increase. Varying the inverter to the PV ratio from 1.1 to 2 decreases system losses by 34% to 41%. The type of charging is dependent on the maximum penetration of EVCSs that the...
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Fast and accurate arctangent approximations are used in several contemporary applications, including embedded systems, signal processing, radar, and power systems. Three main approximation techniques are well-established in the... more
Fast and accurate arctangent approximations are used in several contemporary applications, including embedded systems, signal processing, radar, and power systems. Three main approximation techniques are well-established in the literature, varying in their accuracy and resource utilization levels. Those are the iterative coordinate rotational digital computer (CORDIC), the lookup tables (LUTs)-based, and the rational formulae techniques. This paper presents a novel technique that combines the advantages of both rational formulae and LUT approximation methods. The new algorithm exploits the pseudo-linear region around the tangent function zero point to estimate a reduced input arctangent through a modified rational approximation before referring this estimate to its original value using miniature LUTs. A new 2nd order rational approximation formula is introduced for the first time in this work and benchmarked against existing alternatives as it improves the new algorithm performance....
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This paper investigates the capability of some samples of transient surge suppressors (TVSSs), used in electrical submersible pump (ESP) installations, to withstand non-destructive standard impulse tests. Tests were performed on different... more
This paper investigates the capability of some samples of transient surge suppressors (TVSSs), used in electrical submersible pump (ESP) installations, to withstand non-destructive standard impulse tests. Tests were performed on different ratings of the TVSS and with a voltage rating up to 2.5 kV, to fulfill the basic impulse withstand level (BIL) of the ESP motors. On the other hand, used and unused TVSS were also tested by the standard high-amplitude impulse currents to examine the degradation effect. Compared to the (old) ...
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This paper focuses on a Matlab/SIMULINK model of a photovoltaic cell. This model is based on mathematical equations and is described through an equivalent circuit including a photocurrent source, a diode, a series resistor and a shunt... more
This paper focuses on a Matlab/SIMULINK model of a photovoltaic cell. This model is based on mathematical equations and is described through an equivalent circuit including a photocurrent source, a diode, a series resistor and a shunt resistor. The developed model allows the prediction of PV cell behaviour under different physical and environmental parameters. The model can also be used to extract the physical parameters for a given solar PV cell as a function of temperature and solar radiation. In addition, this study outlines the working principle of PV module as well as PV array. In order to validate the developed model, an experimental test bench was built and the obtained results exhibited a good agreement with the simulation ones.
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ABSTRACT In this paper the measured results of Desert Type PV, in Muscat governorate in Oman, is discussed and analyzed. Several factors were measured and calculated for one whole year including, solar radiation, efficiency of the... more
ABSTRACT In this paper the measured results of Desert Type PV, in Muscat governorate in Oman, is discussed and analyzed. Several factors were measured and calculated for one whole year including, solar radiation, efficiency of the modules, temperature of the modules, energy production and number of sunshine hours. It was found that the average efficiency of this type of PV is 15% during the whole year. Although the number of sunshine hours is more during the summer time, the solar insolation is reduced owing to the high temperature. The power production and efficiency during winter are higher due to the reduction in the ambient temperature. From the measurements we can conclude that this type of PV is suitable for harsh weather such as the hot weather in Arabian Gulf Countries.
ABSTRACT Worldwide, many countries are being affected by greenhouse gas (GHG) emissions. The Sultanate of Oman is no exception. In Oman, both oil- and natural-gas-related activities have the most important shares of the nation's... more
ABSTRACT Worldwide, many countries are being affected by greenhouse gas (GHG) emissions. The Sultanate of Oman is no exception. In Oman, both oil- and natural-gas-related activities have the most important shares of the nation's Gross Domestic Product (GDP). Hence, they are expected to be the primary cause of GHG emissions within the country. In this study, the greenhouse carbon dioxide emissions (CO2) released from the fossil fuels (i.e., oil and natural gas) used in the country for energy production purposes was computed by using the Intergovernmental Panel on Climate Change (IPCC) reference approach for National Greenhouse Gas Inventories. The objective was to develop the CO2 emissions for Oman over the last 40 years starting from year 1972. The obtained results indicated that Oman has a growth in its CO2 GHG emissions. This study is very important and essential, as it will assist Oman to monitor its progress in reducing CO2 emissions. © 2015 Society of Chemical Industry and John Wiley & Sons, Ltd
ABSTRACT With the increased involvement of Distributed Power Generation Systems (DPGSs) into the conventional power system, the structure has evolved and therefore has brought in various challenges albeit improving flexibility and... more
ABSTRACT With the increased involvement of Distributed Power Generation Systems (DPGSs) into the conventional power system, the structure has evolved and therefore has brought in various challenges albeit improving flexibility and smartness of the system. This paper addresses modeling one of these challenges where a Simulink model for inverter-based distributed generation (IBDG) active islanding detection technique is introduced. Out of the various types of active islanding detection methods, the modeling of the general electric islanding detection method which uses the positive feedback of the voltage or frequency at the point of common coupling (PCC) for the detection of an island is presented. This methodology is modeled and applied for an IBDG connected to a low voltage distribution network. The simulation results are presented for a 20kW, three-phase IBDG showing that the system is able to detect islanding and cease the current flow from the IBDG even under critical operating condition of a close matching between the power delivered by the inverter and the load demand (zero nondetection zone operation).
Abstract AV/f control algorithm is presented that is based on constant air-gap flux control with inverter output voltage autoboost. This algorithm permits the realization of variable-voltage-variable-frequency (VVVF) control with a simple... more
Abstract AV/f control algorithm is presented that is based on constant air-gap flux control with inverter output voltage autoboost. This algorithm permits the realization of variable-voltage-variable-frequency (VVVF) control with a simple system configuration. In addition, as a ...
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Abstract Simulations have predicted high performance control characteristics in the torque and speed sensorless control algorithm which uses a stator-flux-controlled V/f PWM inverter. However, in the actual control system, different... more
Abstract Simulations have predicted high performance control characteristics in the torque and speed sensorless control algorithm which uses a stator-flux-controlled V/f PWM inverter. However, in the actual control system, different problems occurred. Among these problems, there are the fluctuation of the inverter input voltage and the voltage error due to switching time lag of power transistors and to voltage drop in inverter power devices. These voltage errors are a big effect on the flux estimation and cause oscillations of the torque and even ...
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Résumé/Abstract The authors present the application of artificial neural network techniques to the load identification and control of AC voltage regulators. The simplicity and cost-effectiveness of these SCR-based AC-AC converters are... more
Résumé/Abstract The authors present the application of artificial neural network techniques to the load identification and control of AC voltage regulators. The simplicity and cost-effectiveness of these SCR-based AC-AC converters are overshadowed by the complexity of their control logic. With unknown and/or variable inductive loads, the SCR's triggering and extinction angles depend on the load parameters in a highly nonlinear fashion. The ANN techniques are proven suitable for parameter identification and control of such nonlinear ...
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Abstract Recently, the development of HVDC cables with polymeric insulation has received a renewed attention. The present work aims at determining the dependence of the dc insulation resistivity on temperature and electric field for... more
Abstract Recently, the development of HVDC cables with polymeric insulation has received a renewed attention. The present work aims at determining the dependence of the dc insulation resistivity on temperature and electric field for low-density polyethylene (LDPE) which is used for manufacturing modern high voltage ac cables. Using a highly precise technique, resistivity measurements were made using thick (~ 2 mm) disc samples at different dc electric fields ranging from 17 kV/mm to 33 kV/mm for a temperature range ...
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Abstract This article presents a theoretical simulation and analysis of all possible factors due to transient overvoltages (TOVs) that could contribute to electrical failures of electric submersible pump (ESP) motors used in oil fields. A... more
Abstract This article presents a theoretical simulation and analysis of all possible factors due to transient overvoltages (TOVs) that could contribute to electrical failures of electric submersible pump (ESP) motors used in oil fields. A transient calculations software package PSCAD is used to simulate a single cable-fed, 3.3-kV induction motor including the mains of the 33-kV distribution system. The factors studied are cable length, earthing resistance and parameters (insulation permittivity and permeability), opening time of CB and its location, ...
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Abstract This paper describes a set of automatic tuning schemes for speed sensorless vector controlled induction motors. The importance of a self-commissioning inverter for sensorless drive systems is highlighted and a new tuning method... more
Abstract This paper describes a set of automatic tuning schemes for speed sensorless vector controlled induction motors. The importance of a self-commissioning inverter for sensorless drive systems is highlighted and a new tuning method of parameters needed for a sensorless drive system is proposed and explained. The tuning includes the estimation of the induction motor parameters used to estimate the speed and to control the motor. The proposed method is compared to recursive least-squares estimation (RLSE) which is ...
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Voltage instability problems in power systems today are, in many countries, one of the major concerns in power system planning and operation. This paper presents the assessment of voltage stability margins for Muscat power system under... more
Voltage instability problems in power systems today are, in many countries, one of the major concerns in power system planning and operation. This paper presents the assessment of voltage stability margins for Muscat power system under normal operating condition and under contingencies. The modal analysis method is applied to identify the weak buses in the system, which could lead to voltage instability. These weak buses are selected as the best locations for applying remedial actions to enhance the stability margins. The results show ...
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ABSTRACT When a galvanic connection between the grid and the PV array exists, a common-mode voltage exists which generates a common-mode currents. These common-mode currents may produce electromagnetic interferences, grid current... more
ABSTRACT When a galvanic connection between the grid and the PV array exists, a common-mode voltage exists which generates a common-mode currents. These common-mode currents may produce electromagnetic interferences, grid current distortion and additional losses in the system. Therefore, to avoid the leakage currents penalizing transformerless power chains, it is worth focusing topologies which do not generate common-mode currents. Some topologies available in the market touch more or less such a crucial requirement. This is said, a small room for improvement still exists. The aim of this work is to focus on recently developed topologies which do not generate common-mode voltage. It was shown that the HERIC topology does not generate common-mode voltage with high efficiency. The focus also will be on different ways to reduce harmonics in the output inverter waveform and to maximize the PV cells output power.