Mohamed Wahab

• Prof. Dr. Mohamed A. A. Wahab
• Minia University

Due to increasing penetration level of renewable energy based Distributed Generation (DG), voltage/reactive power control in distribution networks is currently an important topic. This paper proposes two coordinated voltage/reactive power control approaches in active distribution grids. The proposed coordination control is achieved based on predefi...

Superconducting Magnetic Energy Storage (SMES) unit with a self-commutated converter is capable of controlling both active and reactive power simultaneously and quickly, increasing attention has been focused recently on power system stabilization by SMES control. This paper addresses a new technique robust control design for load-frequency control...

As the Decentralized Generation (DG) penetration dramatically increases in distribution networks, Low Voltage Ride-Through (LVRT) capability of DG becomes a critical issue that has to be investigated and developed. This paper reviews the LVRT requirements of DGs in German grid codes. As the national grid codes are basically valid for transmission n...

This paper introduces a new voltage/reactive power control strategy in active distribution network. The suggested control strategy is based on the Distributed Generation (DG) active power and voltage at the Point of Common Connection (PCC). A comparison between the results of the proposed strategy and standard strategies was presented. The proposed...

The main objectives of the current study are to increase the utilization factor and the penetration level of distributed generation (DG) into distribution network by exploiting the reactive power control capability of the DG. This paper states weak points of the standard reactive power strategies which are already implemented by certain grid operat...

SUMMARY This paper proposes a fault diagnosis system based on the fuzzy relation theory to estimate the faulty item/section(s) of a large power generation station and its transmission lines. Therefore, it diagnoses the faulted item/section(s) in terms of the degree of membership. Besides that, it also examines the mis-operation of corresponding cir...

In this paper, a simplified fault diagnosis method based on Petri nets is proposed to estimate the faulty item/section(s) of a large power generation station. The Petri nets are used as a modeling tool to build fault diagnosis models of item/section(s) of power station which aim to diagnose accurately the faults when a large amount information of S...

This paper presents a simple control strategy for the operation of a variable speed stand-alone wind turbine with a permanent magnet synchronous generator (PMSG). The PMSG is connected to a three phase resistive load through a switch mode rectifier and a voltage source inverter. Control of the generator side converter is used to achieve maximum pow...

The influence of series Flexible AC Transmission Systems (FACTS) device namely, Thyristor-Controlled Series Capacitors (TCSC) on the steady state voltage stability is the main objective of this paper. The Line stability Index LSI under excepted lines outage contingencies is used to identify the critical line which is considered as the best location...

In order to assist and support the operation engineers in control center of a large power station to make rapid and reasonable decision in the critical situations. This paper proposes a fault diagnosis system based on Petri nets to estimate the faulty item/section(s) of that large power generation station and its transmission lines with solving the...

This paper presents a simple control strategy for the operation of a variable speed stand-alone wind turbine with a permanent magnet synchronous generator (PMSG). The PMSG is connected to a three phase resistive load through a switch mode rectifier and a voltage source inverter. Control of the generator side switch mode rectifier is used to achieve...

This paper presents a load power management control strategy for the operation of a stand-alone variable speed wind turbine with a permanent magnet synchronous generator (PMSG) based on the state of charge (SOC) of the battery. The PMSG is connected to a three phase load through a switch mode rectifier and a voltage source inverter. Battery storage...

This paper presents a simple control strategy for a variable speed wind energy conversion system with a permanent magnet synchronous generator (PMSG). PMSG is connected to the grid through a switch mode rectifier and a voltage source inverter. The grid should be supplied by certain levels of powers for certain times from wind energy system accordin...

This article proposes a simplified fault-diagnosis system based on Bayesian networks with noisy-OR/AND nodes to estimate the faulty item/section(s) of a large power station and its transmission lines. The proposed method utilizes the final information of protective relays and corresponding circuit breakers to construct the Bayesian fault diagnosis...

A new and simple maximum power extraction control strategy is proposed for the permanent magnet synchronous generator (PMSG) based variable speed wind energy conversion system (VSWECS). The PMSG is connected to the grid through a switch mode rectifier and a three phase voltage source (VSI) inverter. The generator side switch mode rectifier is contr...

This paper presents a new exact analytical model for single electron transistor (SET) applicable for circuit simulation. It has been developed based on orthodox theory of single electronics using master equation where a scheme has been suggested to determine the most probable occupied electron states. The proposed model is more flexible and is vali...

This paper presents two modeling techniques for the prediction and monitoring of the characteristics of transformer oil. The first employs artificial neural network (ANN) and the second employs non-linear modeling (nlm). The proposed techniques are implemented for predicting the transformer oil residual operating time (trot) which is defined as the...

The precise evaluation and mitigation of the electric field generated by overhead transmission lines has gained great interest due to its impact on health and environmental issues. This paper presents a more generalized technique to calculate the electric field generated by power transmission lines in three dimension coordinates. This technique has...

This paper presents a new exact analytical model for Single electron transistor (SET) applicable for circuit simulation. It was developed based on orthodox theory of single electronics using master equation. A scheme was suggested to determine the most probable occupied electron states. The proposed model is more flexible that is valid for single o...

In this paper, a self-recovery image authentication technique is proposed using randomly-sized blocks. To dived an image into randomly-sized blocks, it undergoes recursive arbitrarily-asymmetric quad tree partitioning. Multiple description coding (MDC) that enhances reliability of altered block recovery, is utilized to generate two block descriptio...

Power variation, voltage fluctuation and resultant flicker are critical issues related to the integration of directly grid-connected constant-speed wind turbines. This study introduces a methodology to enhance the quality of the power and voltage, and minimise the flicker produced from constant-speed direct-connected wind turbines. The method uses...

In this paper the Charge Simulation Method (CSM) is implemented to compute the electric field distribution around Egyptian three phase 500kV transmission line, with the presence and absence of the human model. The human body is simulated as a conducting cylinder object with a hemisphere for his head. Three positions of human body model are consider...

A new static voltage stability index of a radial distribution system is proposed to faithfully evaluate the severity of the loading situation, thereby predicting for voltage instability at definite load value. The pro- posed index includes different parameters which affect the steady-state voltage stability of distribution systems, therefore it give...

The great advance in image processing demands a guarantee for assuring integrity of images. In this paper, a semi-fragile image authentication technique is proposed, which can detect and localize the malicious alteration distinguishing the content-preserving manipulations, such as JPEG compression, from the content alterations. The original image i...

In order to deal with the incomplete information and uncertainties imposed on fault section diagnosis, this paper proposed a fault section diagnosis method based on fuzzy relations for power generation stations, substations and transmission lines. The proposed method utilizes information of protective relays and circuit breakers to build sagittal d...

Digital images are vulnerable to various malicious manipulations. So, effective techniques are demanded for assuring the integrity of image contents. In this paper, a public key self-embedding image authentication technique is proposed which can detect and localize alterations of the image contents and can restore the distorted regions. A doubly li...

� Abstract—Because of the great advance in multimedia technology, digital multimedia is vulnerable to malicious manipulations. In this paper, a public key self-recovery block-based video authentication technique is proposed which can not only precisely localize the alteration detection but also recover the missing data with high reliability. In the...

For the aluminum company at Nag-hammady, resonances are detected for all expected operational conditions. Harmonic filters are designed, and suggested to be installed, and resonances due to expected switchings of those filters are found. Finally methods of harmonic resonance prevention technique in that company network are applied and their effecti...

Keeping the generators operating during transient grid faults becomes an obligation for the bulk wind generation units connected to the transmission network and it is highly desired for distribution wind generators. A proposed scheme is implemented to keep the wind-power DFIG operating during transient grid faults. Challenges imposed on the generat...

This paper introduces an improved strategy to increase the power production of wind turbines equipped with doubly fed induction generators (DFIGs) at low wind speed operation. The performance of DFIG-based wind turbines at low wind speeds, close to the cut in speed, is investigated. A modified control to extend the concept of maximum wind power tra...

The reactive power demand of the induction generator is significantly increased when the generator runs close to the rated operating point. The losses are increased due to the increased reactive power flow. Due to the limitation of converter ratings in the doubly fed induction generator (DFIG) system, power clipping may occur at turbine-rated condi...

This paper introduces a methodology to enhance the quality of the voltage and power produced from fixed-speed direct-connected wind turbines. The method uses an electrolyzer/fuel cell combination to be connected to the point of common coupling via limited rating converters. The control scheme is designed to keep the power ramp rate and voltage fluc...

A new strategy for capacitor allocation in radial distribution systems is presented in this paper. This strategy adds a new constraint to the well-known constraint (allowed voltage violation). The new constraint is the sectional ohmic loss in each branch of the feeder. Sizes and locations of the capacitors are selected in order to achieve the maxim...

The purpose of this paper is to implement non-linear multivariable regression technique (nlm) for the prediction of the residual operating time (ROT) of the transformer oil characteristics. This technique depends on non-linear models for each transformer oil characteristic and linear combination of these non-linear models. The characteristics under...

This paper presents a SPICE model for single electron tunneling (SET) junction based on the orthodox theory of single electronics. This model is more efficient than comparable models. The effect of tunneling resistance, junction capacitance and temperature are included in this model. SET junction is modeled by a resistor, capacitor, voltage control...

This paper presents the effect of the scaling-down of the MOSFET to nanometer regimes on the MOSFET performance. Cut-off frequency, transconductance, CMOS inverter delay and leakage tunneling current are computed. The cut-off frequency is investigated taking into consideration the gate drain and gate source overlap and the fringing capacitances. Th...

This paper presents bandwidth extension of differential CMOS transimpedance amplifier (TIA) using on-chip inductor techniques. On-chip spiral inductor is connected in series with the output node to enhance the bandwidth. The effects of the inductor nonidealities are included in the design. Simple and accurate inductor lumped circuit model is used i...

Withstanding grid faults becomes an obligation for the bulk wind generation units connected to the transmission network and it is highly desired for distribution wind generators. In this paper, a proposed scheme is implemented for DFIG to keep it operating during transient grid faults. Challenges imposed on the generator configuration and the contr...

Power and voltage generated by a wind turbine are more variable than that produced by conventional generators. Therefore, with the increasing penetration of wind energy into the grid, it is very important to simulate precisely the wind turbine/grid interaction to evaluate voltage fluctuation and other power quality aspects. In this paper, the wind...

This paper presents an artificial neural network (ANN) based modeling technique for predicting the voltage stability of radial distribution systems. The modeling technique is based on a new voltage stability index for assessment of radial distribution systems L_v. The index is implemented to investigate a 33-bus distribution system. An A...

Harmonic resonances may damage equipments and interrupt electric power customers services. Shutdowns may affect seriously harmonic resonant frequencies and may initiate new resonances in power systems. Series and shunt capacitors are used as compensators to improve system operational conditions. Controlled static VAR compensators are also used for...

This paper is concerned with the transformer coil dc leakage current under different conditions. These conditions include in-air, and in-oil leakage, currents with or without artificial coil deposits. In-oil leakage, currents are investigated when the coil is immersed in new or used transformer oil at different temperatures. The results showed that...

Shutdowns may affect seriously harmonic resonant frequencies and may initiate new resonances in power systems in presence of series and shunt capacitors which are used as compensators to improve system operational conditions. Influences of these shunt and series capacitors on harmonic resonance conditions in presence of other harmonic sources are s...

This paper introduces a newly modified forced oil-cooling system, which comprises a bypass filter (BPF). The BPF has been introduced in such a way that its intake oil is the hot oil from the transformer top and to deliver it at the inlet of the oil-circulating pump. This system has been used for two transformers. Periodical measurements of the phys...

This paper presents techniques developed to accurately model the characteristics of transformer oil for the purpose of predicting the effect of aging on these characteristics. Aging causes some of the transformer oil characteristics to violate the internationally specified limits. The purpose of this simulation is to develop alternative techniques...

This paper introduces a newly modified forced oil-cooling system in which a bypass filter (BPF) has been used. The BPF was introduced in such a way that its intake oil is the hot oil from the transformer top and the outlet is connected to the input of the oil-circulating pump. This system has been used for two transformers. Periodical measurements...

The growing use of static switching circuits in modern power systems gives a reason for increasing need to analyze and understand these circuits and their interactions with the power system. One of the most important components used in power systems is the Static VAR Compensator (SVC). A compensator contains a Thyristor Controlled Reactor (TCR) whi...

The effect of aging on transformer oil physical, chemical and electrical properties has been studied using the international testing methods for the evaluation of transformer oil quality. The study has been carried out on twelve transformers in the field and for monitoring periods up to 8 years. The properties which are strongly time dependent have...

The effect of aging on transformer oil's physical, chemical and electrical properties was studied using the international testing methods for the evaluation of transformer oil quality. The study was carried out on twelve transformers in the field and for monitoring periods up to eight years. The properties which are strongly time dependent were spe...

In this paper, a study on transformer oil deposits has been carried out by infrared analysis and ferrographic inspection. The results showed that the location at which deposits accumulate has a great influence on their constituents. Deposits have higher water content, total acidity and ash content than the corresponding transformer oils. The functi...

Harmonic resonances may damage equipments and interrupt electric power customers services. Shutdowns may affect seriously harmonic resonant frequencies and may initiate new resonances in distribution power systems. This paper proposes a hybrid active power filter for damping harmonic resonances in distribution power systems. The hybrid filter consi...