Papers by Mahmoud A Saleh,
Measurement and Control, 1978
The effect of each of the equivalent circuit parameters of a two-phase servomotor on its electrom... more The effect of each of the equivalent circuit parameters of a two-phase servomotor on its electromechanical time-constant is investigated. It is shown that the value of the rotor resistance has a marked effect on the time-constant. There exists a certain value of the equivalent rotor resistance, within the practical range, at which the motor time-constant becomes minimum; this value of rotor resistance is obtained in terms of other para meters. A new criterion is proposed when designing a 2-phase servomotor, namely, the minimum time-constant condition.
Journal of Power …, 2009
In this paper two modes of operating a wound rotor induction machine as a generator at sub-and su... more In this paper two modes of operating a wound rotor induction machine as a generator at sub-and super-synchronous speeds in wind energy conversion systems are investigated. In the first mode, known as double fed induction generator (DFIG), the rotor circuit is fed from the ac mains via a controlled rectifier and a forced commutated inverter. Adjusting the applied rotor voltage magnitude and phase leads to machine operation as a generator at sub-synchronous speeds. In the second mode, the machine is operated in a slip recovery scheme where the slip energy is fed back to the ac mains via a rectifier and line commutated inverter. This mode is described as double output induction generator (DOIG) leading to increase the efficiency of the wind-to electrical energy conversion system. Simulated results of both modes are presented. Experimental verification of the simulated results are presented for the DOIG mode of operation, showing larger amount of power captured and better power factor when compared to conventional induction generators.
Abstract: In this paper the sub-harmonics associated with a specially designed single machine bru... more Abstract: In this paper the sub-harmonics associated with a specially designed single machine brushless doubly fed induction generator (SM-BDFIG) are analyzed at super-synchronous speeds. The SM-BDFIG is coupled to a variable speed wind turbine, and its rotor circuit is connected to a 3-phase rectifier feeding Li-ion batteries. A mathematical model, using Fourier expansion, is developed to define the sub-harmonics created by the time harmonics of the rotor currents irrespective of any other space or time harmonics due to winding distribution, unbalanced grid phases, or presence of harmonics in the grid voltages. The effect of the positive and negative sequence harmonics on the performance of the generator is then presented, showing the speed ranges within which these sub-harmonics are most effective, as well as the speed ranges within which these sub-harmonics are least effective. The obtained results help to design a SM-BDFIG with less harmonic distortion, hence improving its perfo...
International Journal of Engineering Research, 2015
In this paper the sub-harmonics associated with a specially designed single machine brushless dou... more In this paper the sub-harmonics associated with a specially designed single machine brushless doubly fed induction generator (SM-BDFIG) are analyzed at supersynchronous speeds. The SM-BDFIG is coupled to a variable speed wind turbine, and its rotor circuit is connected to a 3phase rectifier feeding Li-ion batteries. A mathematical model, using Fourier expansion, is developed to define the subharmonics created by the time harmonics of the rotor currents irrespective of any other space or time harmonics due to winding distribution, unbalanced grid phases, or presence of harmonics in the grid voltages. The effect of the positive and negative sequence harmonics on the performance of the generator is then presented, showing the speed ranges within which these sub-harmonics are most effective, as well as the speed ranges within which these sub-harmonics are least effective. The obtained results help to design a SM-BDFIG with less harmonic distortion, hence improving its performance in wind energy conversion systems.
Russian Electrical Engineering
ABSTRACT
In this paper the dynamic behavior of a double-output induction generator (DOIG) driven by wind t... more In this paper the dynamic behavior of a double-output induction generator (DOIG) driven by wind turbine under wind speed variation and during and after grid faults, is investigated. Two damping methods are tested to reduce the high transient values of currents and voltages at different parts of the wind energy conversion system. First, connecting 3-phase capacitors in the rotor circuit did not reduce the high transients due to wind speed variations, but only improved the system power factor. In the second method, 3-phase inductance is connected in series with the stator terminals. This method reduced these transients by 50% and improved the system power factor. The inductance value has to be limited to avoid deteriorating the generation system performance. Fault ride through is investigated after symmetrical and unsymmetrical faults by insertion of inductance at the stator terminals. This method led to suppress the induced over-voltages and, hence, over-currents in the rotor windings and converters. Keyword:
British Journal of Applied Science & Technology, 2014
ABSTRACT In this paper a new design for brushless doubly fed induction machine for operation as g... more ABSTRACT In this paper a new design for brushless doubly fed induction machine for operation as generator in wind energy systems is proposed. This machine, named single machine- brushless doubly fed induction generator (SM-BDFIG) is composed of three main components; a regular three phase wound rotor induction machine, a power electronic converter, and a pack of rechargeable Lithium-ion batteries. The converter is mounted on the outer surface of a web reinforced hollow metallic (aluminum) or fiber glass cylinder. The battery packs are embedded in the inner part of the cylinder between the webs. The hollow cylinder is mechanically coupled with the induction machine on the same shaft. Therefore, all the three main components of the SM-BDFIG rotate with the same angular speed. A brief description and analysis of the proposed machine merits, parameters, and characteristics are given. The authors could provide the detailed designs of SM-BDFIG and the required testing facilities to the manufacturer who is ready to fabricate the first product of SM-BDFIG and facilitate their testing.
Smart Grid and Renewable Energy, 2011
In this paper, the operation of the Double Fed Induction Generator (DFIG) in the range from synch... more In this paper, the operation of the Double Fed Induction Generator (DFIG) in the range from synchronous speed down to sub-synchronous speeds is analyzed using the power-flow approach. The objective of this analysis is to determine a ceiling for the rating of the converter interfacing the rotor of the wind driven double fed induction generator (DFIG) to the grid. Sizing the converter is an important issue in determining the economic viability of using the DFIM as a generator at synchronous and sub-synchronous speeds in wind energy conversion systems. The size of the converter is proved to be less than 10% of the rated power of the DFIG, which is 40% to 67% lower than that estimated in previous publications.
Saudi Medical Journal, Feb 1, 2004
Objectives: This study was conducted to examine the smoking habits among male secondary school st... more Objectives: This study was conducted to examine the smoking habits among male secondary school students in Al-Qassim, Kingdom of Saudi Arabia (KSA) and to assess their knowledge and attitudes towards smoking. Methods: This cross-sectional study was conducted in Al-Qassim region, KSA during March 2003. Randomly selected was 14 out of 110 government male secondary schools. In the sample section, care was taken to represent urban and rural communities. In urban areas, 8 schools with the largest number of students were selected. This is in addition to 3 schools, which were the only schools with special education on Islamic, Commercial and Technical programs. In the rural areas the 3 most distant schools were included in the sample. Data were obtained through self-administered questionnaires that contained questions on personal background, smoking behavior, knowledge and attitude towards cigarette smoking. A total of 2203 students responded to the questionnaires with 83% response rate. Results: Of the studied group, 606 (29.8%) were current smokers and among these 83.7% started smoking at the age of 15 years or less. Technical and commercial secondary school students had higher prevalence of the habit of smoking than those in general and Islamic secondary schools. It was found that the more pocket money received by the students, the higher was the prevalence of smoking. The most common reason given for cigarette smoking behavior (CSB) was the influence of friends (63.5%). Family factor, especially the brother's smoking habit (24.8%) was also important. Most of the students knew that smoking is harmful to their own health (89.3%), and to others (73.9%). The association between smoking and lung cancer was 84.3%, 80.9% for chest disease and 78.2% for heart disease, while the relation to other diseases was less known. Conclusions: We conclude that onset of smoking in the young is alarming. This is of immense importance in formulating health education strategies, which should be directed towards pupils, teachers and parents. The religious aspect should also be an integral part of such programs.
2013 IEEE 10th International Conference on Power Electronics and Drive Systems (PEDS), 2013
In this paper the dynamic behavior of a double-output induction generator (DOIG) driven by wind t... more In this paper the dynamic behavior of a double-output induction generator (DOIG) driven by wind turbine under wind speed variation and during and after grid faults, is investigated. Two damping methods are tested to reduce the high transient values of currents and voltages at different parts of the wind energy conversion system. First, connecting 3-phase capacitors in the rotor circuit did not reduce the high transients due to wind speed variations, but only improved the system power factor. In the second method, 3-phase inductance is connected in series with the stator terminals. This method reduced these transients by 50% and improved the system power factor. The inductance value has to be limited to avoid deteriorating the generation system performance. Fault ride through is investigated after symmetrical and unsymmetrical faults by insertion of inductance at the stator terminals. This method led to suppress the induced overvoltages and, hence, over-currents in the rotor windings and converters.
Indonesian Journal of Electrical Engineering and Computer Science, 2019
The effect of three-phase grid fault on the performance of a wind-driven single machine-brushless... more The effect of three-phase grid fault on the performance of a wind-driven single machine-brushless double fed induction generator (SM-BDFIG) is investigated. The fault-ride-through (FRT) of the grid-connected SM-BDFIG is then studied when installing a Static Synchronous Compensator (STATCOM) between the grid and the generator. Recovery from the grid fault before installing the STATCOM is studied and compared to the generation system recovery with installed STATCOM. The performances of the stator and rotor currents, stator and rotor voltages, electric torque, active power, reactive power, and battery pack voltage and current are presented for both cases. The total harmonic distortion (THD) of stator and rotor voltages and currents are also presented and compared. Results proved the faster recovery from grid faults, the continuity of currents and voltages, and the continuity of active power supplied to the grid when installing the STATCOM. However, slightly higher THD took place in the...
2014 IEEE Conference and Expo Transportation Electrification Asia-Pacific (ITEC Asia-Pacific), 2014
ABSTRACT The Unified Power Quality Controller (UPQC) device is an integration of a series active ... more ABSTRACT The Unified Power Quality Controller (UPQC) device is an integration of a series active filter and a shunt active filter. The main purpose of a UPQC is to compensate for voltage flicker, reactive power, and harmonics. It has the capability of improving power quality at the point of installation on power distribution systems or industrial power systems. This paper utilizes the UPQC to enhance the low-voltage ride-through (LVRT) capability of the doubly fed induction generator (DFIG)-based wind energy conversion system (WECS) according to the grid connection requirement. UPQC is applied to protect the system from ground faults, allows fast restoring of generation system steady state characteristics, improves the system power factor, and prevent the system from rotor over-current and dc-link overvoltage. A comparison between the LVRT results using the UPQC and the results when using STATCOM or DVR is also presented
The effect of three-phase grid fault on the performance of a wind-driven single machine-brushless... more The effect of three-phase grid fault on the performance of a wind-driven single machine-brushless double fed induction generator (SM-BDFIG) is investigated. The fault-ride-through (FRT) of the grid-connected SM-BDFIG is then studied when installing a Static Synchronous Compensator (STATCOM) between the grid and the generator. Recovery from the grid fault before installing the STATCOM is studied and compared to the generation system recovery with installed STATCOM. The performances of the stator and rotor currents, stator and rotor voltages, electric torque, active power, reactive power, and battery pack voltage and current are presented for both cases. The total harmonic distortion (THD) of stator and rotor voltages and currents are also presented and compared. Results proved the faster recovery from grid faults, the continuity of currents and voltages, and the continuity of active power supplied to the grid when installing the STATCOM. However, slightly higher THD took place in the...
Energies, 2019
This paper provides an extensive review of the conducted research regarding various microgrids (M... more This paper provides an extensive review of the conducted research regarding various microgrids (MGs) control techniques and the impact of Information Communication Technology (ICT) degradation on MGs performance and control. Additionally, this paper sheds the light on the research gaps and challenges that are to be explored regarding ICT intrinsic-limitations impact on MGs operations and enhancing MGs control. Based on this assessment, it offers future prospects regarding the impact of ICT latencies on MGs and, consequently, on the smart grid. Finally, this paper introduces a case study to show the significance and examine the effect of wireless communication technologies latency on the converters and the DC bus voltage of a centralized controlled DC MG. A DC microgrid with its communication-based control scheme was modeled to achieve this goal. The MATLAB simulation results show that the latency impact may be severe on the converter switches and the DC bus voltage. Additionally, th...
IFAC-PapersOnLine, 2020
This paper aims to provide more insight on the impact of Denial of Service (DOS) attacks on centr... more This paper aims to provide more insight on the impact of Denial of Service (DOS) attacks on centralized controlled DC Microgrids. A mathematical model, which the author previously developed to represent microgrid stability during delays, will be utilized to investigate the impact of DOS attacks. A vulnerability analysis will be conducted to highlight the attack timing and strategy that could jeopardize the microgrid operation.
Energies, 2020
In this paper, a dual-stage modeling and optimization framework has been developed to obtain an o... more In this paper, a dual-stage modeling and optimization framework has been developed to obtain an optimal combination and size of wayside energy storage systems (WESSs) for application in DC rail transportation. Energy storage technologies may consist of a standalone battery, a standalone supercapacitor, a standalone flywheel, or a combination of these. Results from the dual-stage modeling and optimization process have been utilized for deducing an application-specific composition of type and size of the WESSs. These applications consist of different percentages of energy saving due to regenerative braking, voltage regulation, peak demand reduction, estimated payback period, and system resiliency. In the first stage, sizes of the ESSs have been estimated using developed detailed mathematical models, and optimized using the Genetic Algorithm (GA). In the second stage, the respective sizes of ESSs are simulated by developing an all-inclusive model of the transit system, ESS and ESS mana...
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Papers by Mahmoud A Saleh,