Doaa Khalil Ibrahim

Car exhaust is one of the most common causes of ozone hole aggravation, electrical vehicles (EVs) represent a promising solution to avoid this problem. Despite the benefits of EVs, their random charging behavior causes some difficulties regarding the electric network performance, such as increased energy losses and voltage deviations. This paper aims to achieve the proper scheduling of the EVs charging process, avoid its negative impacts on the network, and satisfy the EVs users’ requirements. The EVs charging process is formulated as an optimization problem and solved using particle swarm optimization. The optimization problem formulation considers the EV arrival and departure times and the state of charge required by the user. Different strategies such as separated, accumulated, and ranked strategies with continuous or interrupted fixed charging have been applied to solve the uncoordinated EVs charging problem. These strategies are extensively tested on the modified IEEE 31 bus system (499-node network), using the combination of both Open DSS and MATLAB m-files. The simulation results confirm the effectiveness of the proposed accumulated ranked strategy with interrupted fixed charging in improving the overall power system performance. The achieved improvements include minimizing: the peak power consumed, the peak power losses, and the voltage drop. Moreover, the cost of the EVs charging in most of the feeders has been decreased to a satisfying value. A comparison between the proposed strategy and some previously reported strategies has been performed to ensure the technical and economic enhancement of the proposed strategy.

Thyristor controlled series compensation (TCSC) is widely used in long transmission lines to mainly improve power transfer capability. However, TCSC produces complicated impedance that negatively affects distance protection operation. The wind energy generation system produces additional complexity to the distance protection performance due to the variation of wind speed and fault current level. This paper proposes an integrated scheme to change adaptively the settings of the Mho distance protection by shifting the relay characteristics considering the bad impacts of TCSC, wind power and fault resistance. The proposed scheme achieves its main stages starting from fault detection, until relay tripping decision procedure including online estimation for preliminary fault location, impedance of TCSC and fault resistance using limited communication requirements. By extensive MATLAB simulations, the performance of the proposed scheme is examined compared with the conventional Mho relays under different fault locations, fault inception angle, fault resistance, different wind power penetration, different wind speeds and different TCSC ring angles. The achieved results ensured that the proposed scheme improves significantly Mho distance relay operation and avoids under-reaching and over-reaching problems irrespective of the large shunt capacitance along the transmission line, and also without identifying the parameters of TCSC such as the capacitance, the inductance or the ring angle.

Optimizing the Photovoltaic (PV) hosting capacity (HC) considering the irradiance’s variability properly and the load during the day represents a critical matter. Typically, the high PV HC results in overvoltage and high voltage fluctuations at the point of common coupling (PCC) with the utility. In this paper, a new algorithm is proposed for enhancing PV HC by considering the smart inverter functions to overcome key PCC issues. The Volt-Var and dynamic reactive current functions of the smart inverter are suggested to increase the PV HC. Furthermore, the time of use tariff is utilized for mitigating the duck curve issue at the utility by reducing the peak to valley difference of the substation net load curve. Quasi-static timeseries simulations are performed using the OpenDSS program to prove the effectiveness of the proposed algorithm. The proposed algorithm is validated by extensive numerical analysis on the standard IEEE 123 node test feeder. Deduced outcomes are very encouraging in mitigating the overvoltage, reducing the energy losses, limiting the considerable number of on-load tap changes, and alleviating the high voltage fluctuations.

Portable devices are part of people’s daily lives, since they provide the capabilities that make life easier. However, they consume much energy that requires continuous charging. Integrating renewable energy sources, especially photovoltaic (PV) modules into wireless charging, has been widely adopted in order to increase availability, flexibility, safety, and robustness. In this paper, a new variable frequency control technique for inductive power transfer (IPT) is proposed in order to overcome the switching frequency limitation and increase the transfer efficiency without increasing the switching frequency. At first, charging power (PV power) is stored in a battery. Then, it is transferred based on inductive coupling when needed. The hardware of the proposed wireless charging system has been carried out for two different configurations. The first one is the single switch using a variable frequency control algorithm, which has achieved 40% efficiency. The other one uses half-wave inverter applying no resonance for two types of core: Nano-crystalline and ferrite. For that configuration, the maximum achieved efficiency has been 80% at zero air gap and 36.91% at the 5 mm air gap by the Nano-crystalline core.

From about two decades passed, a new expression was proposed for the first time: ‘‘Virtual Power Plants (VPPs)”. At this moment, a question was asked about if the VPPs can contribute as a trustworthy and environmentally oriented energy supply, or not? From this instant, over two hundred articles was presented for the management and optimal utilization of such a system, reliability and adaptation of VPP with the network connected to, retail and wholesale markets . . . etc. Most or approximately all articles intended with VPPs focused on studying VPPs from economical point of view only and did not studied the electrical and energy performance of VPPs. This paper represents a novel combined model for economical and electrical performances together of a generic VPP (GVPP); the electro-economical model (EEM). Two main targets are required from the proposed GVPP EEM: best performance and active network energy management of this GVPP. Also, a proposal for the first real case study in Egypt is taken under consideration: Siwa Oasis, Egypt. Siwa Oasis proposed VPP is modeled also with EEM. EEM for these two cases (GVPP and Siwa Oasis VPP) are simulated to obtain best performance and active network energy management for these VPPs. All data and results are stated and discussed.

Increasing energy demand worldwide has resulted in more penetration of renewable sources for developing non-polluted electric energy despite their prices are not economically competitive to traditional generation systems due to intermittent nature of renewable resources. Energy storage systems are used to counteract the intermittent nature of renewable sources. Therefore, the optimal sizing and design of stand-alone renewable generating systems is a significant concern to get a more cost-effective system. This paper focuses on achieving the optimum design and size of a microgrid to meet the load requirements and reducing the total cost including capital, investment, operational and maintenance costs. For this aim, the sizing problem is formulated to be solved using three well-known metaheuristic algorithms, namely, Particle Swarm Optimization (PSO), Grey Wolf Optimization (GWO) and Cuckoo Search Optimization (CSO). The employed microgrid comprises hybrid renewable energy sources of PV/Wind systems integrated with a hybrid energy storage system of Battery and FC/Electrolyzer set for supplying AC loads located in Zafarana, Egypt. On the basis of real meteorological data of the studied location, the produced energies from the renewable sources are estimated using MATLAB developed algorithms. The simulation results showed that the optimized design using CSO can robustly and efficiently yield the optimal design of a microgrid.

The capability of the inductive power transfer (IPT) for wireless charging mainly depends on both coil structure and inverter topology. The paper presents the resonant inverter based on the concept of energy injection and free oscillation which are applied to increase the resonant frequency without raising the switching frequency. The implemented inverter utilizes the variable frequency zero current switching (ZCS) control strategy for parallel configuration that ensure the high operating frequency at multiplies of the inverter switching frequency. Consequently, it will result in decreasing the inverter switching loss and also reducing the coil size that operates at resonant frequency. The coil design methodology is introduced in details while studying the different factors affecting the coil behavior. The performance of the overall designed system is evaluated via simulation tests carried out using ANSYS Maxwell and MATLAB SIMULINK.

This paper investigates the impacts of the centralized and distributed grid-connected photovoltaic systems on radial distribution networks. Different weather conditions are considered. Different PV penetration levels are investigated in both centralized and distributed PV configurations. Daily simulation is performed using the Open Distribution System Simulator (OpenDSS). The study will include the impacts on voltage magnitude, the voltage regulators, the voltage unbalance factor and losses during the day. The simulations results are presented in details and conclusions are drawn based on them.

From about fifteen years passed, a new term was proposed for the first time by Dielmann and Velden: "Virtual Power Plant (VPP)", and they asked about if the VPPs can contribute as a reliable and environmentally oriented energy supply, or not?, at this moment, they considered some problems that must be examined to insure the success of this idea; like: management of such a system (optimal utilization), adaptation of VPP with the network connected to (reliability), markets (retail and wholesale) … etc. If these problems are solved, then the VPP has a large opportunity to deliver an important contribution as an economic, reliable and nonpolluting energy supply system. The market is the dominant factor for the success of VPPs being. Before the age of distributed generation (DG), the energy delivery pricing model was the cost against service. The model states that consume (buy) energy then pay -buy and pay-. When the age of renewables raised up, the model of buy and pay is shifted away to a new market based pricing model: pay at first and then buy. Another conceptual model starts to appear including active demand side participation using the transactive energy concept. In this paper, a new combined model for market and electrical performance of VPPs is presented; the electro-economical model (EEM). The model will include the four basic components of any VPP: dispatchable power plants, flexible loads, storage units, and stochastic generating units. Two main targets for the proposed modeling: optimal operation of VPPs, and active network energy management of VPPs. The VPP can earn profit from the market and as a result, its objective reduces to maximizing its profit (ρ). Energy management in a VPP or active network management means the optimal operation of this VPP in order to manage energy flow. Optimal operation is based on a stochastic basis of energy sources and multi-market framework.

Most of the previous researches which intended with the subject of virtual power plants (VPPs), focused on the study of VPPs from economical point of view: auctions, bidding, trading, markets, pricing, cost, profit, benefits, risk, investors … etc. Merely conjecture, all the VPPs' models presented are financial and economical models, with no one prescribed electrical model. In this paper, a generic VPP will be proposed and considered for the study. The proposed generic VPP will be modeled with a novel Electro-Economical Model (EEM). The proposed model was constructed on three steps: construction of electrical model, construction of economical model, and combining both electrical and economical models to form EEM of the proposed generic VPP. The proposed generic VPP consisting of four basic components: dispatchable power plant(s), flexible load(s), storage unit(s), and stochastic generating unit(s); was illustrated. This system model has been simulated. All simulation results will be demonstrated and discussed.

A new Power Management Regulation Control (PMRC) integrated with Demand Side Management (DSM) strategies is proposed to enhance the Energy Management System (EMS) of a stand-alone hybrid microgrid. The microgrid combines Wind and PV systems as Renewable Energy Sources (RES) with a hybrid Energy Storage System (ESS) of Battery and Fuel Cell/Electrolyzer set. Towards achieving Net Zero Energy Supply, such microgrid is adequate in remote and isolated new communities with AC controllable critical and noncritical loads. The proposed PMRC implies two-levels of control based on Multi-Agent System (MAS). The first level keeps the output power of each source in its maximum available output power by applying maximum power point tracking (MPPT) techniques. The second level is based on making proper decisions for achieving the power balancing regulation and coordination between the available and the reserve power of the RES and ESS under different operating modes. Valley Filling, Energy Conservation and Load Shifting are applied as DSM strategies to improve loads sustainability during system contingencies. Considering the battery as the most expensive part in the microgrid, the effectiveness of the proposed strategy is further verified by determining the maximum permissible estimated battery lifetime during the operation in all possible scenarios. Extensive simulation studies for various scenarios of microgrid operation in a year were carried out using Matlab/ Simulink with realistic typical wind speed, solar irradiation data and restricted by the status of available ESS.

The presence of DGs in power system networks tends to negatively affect the protective relays coordination. The proposed method introduces an approach to minimize the numbers of relays that acquire new settings on contrary to their original settings (case without DG), to achieve relays coordination in case of adding DG, since relays coordination with minimum number of relays of readjusted settings represents economical target, especially in networks containing mixture of electromechanical and adaptive digital relays. The scheme decides the possible minimum number of re-adjusted relays and their locations in an optimum manner to achieve proper relays coordination in case of adding DGs. The proposed approach is divided into two successive phases; the first phase is stopped when the first relays coordination solution is achieved. The second phase increases the possibility to keep higher number of relays at their original settings than that obtained in first phase through achieving multi solutions of relays coordination. The proposed approach is implemented and effectively tested on the well-known IEEE-39 bus test system.

The presence of DGs in power networks tends to negatively affect relays coordination. Adding fault current limiters FCLs is one of the possible solutions to mitigate negative impacts of DGs addition on protection systems. Traditional schemes have estimated the minimum value of FCL to restore relays coordination when adding DGs without resetting of any relays. That minimum value of FCL in such case is called a critical value, where below this value the relays coordination will be lost.
Nowadays, designing FCL to simultaneously achieve two conflicted objectives of good performance and low cost is considered a great challenge. The paper introduces a new scheme to determine to what extent we could decrease FCL impedance value below its critical value with re-adjusting the original settings of only one adaptive relay to get relays coordination. Decreasing FCL value below its critical value will reduce the cost especially for superconductivity FCL. The proposed scheme can determine the location of that selected relay to be an adaptive one and estimate its re-adjusted new settings to be applied when DGs are added while inserting the reduced value of FCL.
Actually the proposed scheme can be applied for any networks irrespective of the number of added DGs and their capacities; while having an adaptive relay is the only requirement to implement it. The proposed approach is implemented and effectively tested on the large well-known interconnected IEEE-39 bus test system with 84 relays. Its results are compared with other approaches where, no readjusted relays settings are applied. A noteworthy advantage of the proposed scheme is the ability to implement a reduced FCL value than the critical value, by adjusting only one relay settings in the whole network. The proposed scheme may also be extended to re-adjust settings of more than one relay and get further reduced value of FCL. Furthermore, it is also shown that a more optimum value of the total operating time of all primary relays for near end faults is achieved when applying the proposed method rather than other traditional schemes.

In this contribution, the three-phase underground cable is modelled using COMSOL Multiphysics software to evaluate the steady state and transient thermal performances. Finite element technique is applied using the heat conduction equation to study the temperature distributions in power cables components and the surrounding environment for both linear and non-linear loads. A real case study of 220 kV, 340 MVA three phase single core copper cables insulated by XLPE is studied. Other types of insulation such as oil, and SF6 gas and their contributions of convection and radiation are investigated at trefoil and flat configurations. The loading capability under different ambient conditions for average moisture soil and dry soil with low moisture content are also evaluated taking into account the unfavourable effect of dry zones formation. Moreover, the challenge of predicting the accurate thermal performance and estimating the required derating factor in the presence of odd harmonics is considered. The effect of the change of the frequency spectrum of the non-linear load current by involving different simultaneous harmonic orders for the same total harmonic distortion is extensively investigated for both flat and trefoil configurations. It is concluded that all harmonics contributions should be considered, to accurately calculate the required cable derating.

This paper presents an automated fault location scheme for MV overhead distribution networks. The scheme utilizes only the measurements of voltage signals at the main substation. Clarke and Fast Fourier transformations are applied to get the frequency of the travelling wave generated during the
fault. A simple automation system is implemented to identify the faulted lateral. A typical 22 kV distribution system is used to test and validate the proposed scheme. ATP program is used to simulate the tested network while the required calculations are performed by MATLAB developed algorithms. Extensive fault cases are carried out at different fault positions, inception angles, fault resistance and load levels. The calculated errors indicate that the proposed scheme has low sensitivity to the change of the fault conditions that ensures the effectiveness and robustness of the proposed scheme.

Synchronous generator in electric power plants –as well as the power transformer - is very important and expensive element so it should be provided with fully protection system to protect it against any abnormal conditions. Failure can occur in a generator or transformer due to different reasons. The protection system must prevent the protected equipment from being affected by external faults in addition to prevent evolving damage in case of internal faults. Repeated breaks of generation power stations in last few years are recorded. Because of their great impact on the Egyptian unity network (500 kV and 220 kV), it is essential to deeply review the efficiency of various existing protection schemes designed for generating stations. Detailed analyses of some of the major and destructive real faults recorded at some stations are carried out. Accordingly, modifications for the power plant protection schemes are recommended.

In this paper, coordination strategy that considers using user defined characteristics for the inverse time overcurrent relays is proposed. Typically, the coordination between relays operating times within meshed systems are achieved by adjusting two relay settings; pick up current and time multiplier setting (TDS and Ip). The equation that models the digital inverse time overcurrent relay operation has two constants; one of them represents the constant for relay characteristics (A) and the other one represents the inverse time type (B). The proposed coordination strategy considers the two relay characteristics constants as continuous variable settings that can be adjusted. These (A and B) values are chosen optimally in addition to (TDS and Ip) to achieve coordination. The coordination problem is formulated as a nonlinear programming problem where the main objective is to minimize the overall time of operation of relays during primary and backup operation considering faults at different locations. The results are compared against the relay coordination using the conventional settings. The problem is applied to the meshed power distribution network of the IEEE 30 bus systems equipped with synchronous based DGs. The results show that the proposed strategy can significantly reduce the overall relay operating time and thus making it an attractive option for meshed distribution systems with DG.

Coordination between inverse time overcurrent relays within meshed systems are achieved by adjusting two relay settings; pick up current and time multiplier settings. The operating time of these relays is also a function of two additional constants; one represents the constant for relay characteristics and the other one represents the inverse time type. For typical relays, each of these two constants has four definite values and choosing between them indicates the selected relay operating curve: either standard inverse, very inverse, extremely inverse or long time standby earth fault time-current relay characteristics. In this paper, a coordination strategy, that takes advantage of the available capabilities in microprocessor based relays, is proposed by considering the two relay characteristic constants as continuous variable settings that can be adjusted in addition to the conventional pickup current and Time Dial Setting (TDS). The protection coordination problem is formulated as a nonlinear programming problem where the main objective is to minimize the overall time of operation of relays taking into account protection coordination constraints. The proposed approach is applied to the IEEE 14 bus system and is compared with the conventional two setting relay.

FCL (fault current limiter) is used to solve relays miscoordination problem arises from DG (distributed generation) installation. In most published researches, different optimization methods are developed to obtain optimal relay settings to achieve coordination in case of not installing DG, then depending on the achieved optimal obtained relay settings, FCL impedance is deduced to ensure relays coordination restoration in case of installing DG. Based on original optimal relay settings, obtained FCL impedance is not the minimum one required to achieve relay coordination. The contribution of this paper is the generation of multi sets of original relay settings that increase the possibility of finding FCL impedance of minimum value which is lower than the calculated value based on original optimal relay settings. The proposed method achieves better economic target by reducing FCL impedance. The proposed approach is implemented and tested on IEEE-39 bus test system.

Directional inverse time overcurrent relays are used in protection systems of meshed networks to operate for fault currents in its forward zone of operation. They are used for primary and backup protection and their operation needs to be coordinated to assure selectivity. Different optimization techniques have been used to select their settings to achieve protection coordination, however the optimal protection coordination problem formulation doesn’t consider the fault current direction to assure correct operation especially for
backup relays. This paper proposes the addition of fault current direction constraint to the formulation of the optimal directional inverse overcurrent relays coordination. The proposed formulation is tested on the distribution portion of the IEEE 30 bus system considering the effect of distributed generation addition. Results show that the proposed formulation gives more accurate optimal relay settings and thus highlighting the importance of inclusion of the proposed direction constraint in the protection coordination problem.

Connection of distributed generation (DGs) powered by renewable energy resources in power systems has numerous benefits. However the presence of these (DGs) increase the fault current levels in different points, and disturb the protection coordination of the existing relays. Two approaches are proposed for coordination of directional overcurrent relays (DOCRs) in power systems with (DGs), depending on the types of system relays either adaptive or non adaptive. For adaptive protection system, the first proposed approach is based on linear programming technique which used to calculate the relay settings in case of DGs existing or not. For non-adaptive protection system, the second proposed approach is introduced, in which minimum impedance of fault current limiter is calculated to restore the coordination of relays without altering the original relay settings. The two proposed approaches are implemented and tested on IEEE-39 bus test system.

Nuclear Power Reactors (NPRs) are large in scale and complex, so the information from local fields is excessive, and therefore plant operators cannot properly process it. When a plant malfunction occurs, a great data influx is occurred, so the cause of the malfunction cannot be easily or promptly identified.
A typical NPR may have around 2,000 alarms in the Main Control Room (MCR) in addition to the display of analog data. During plant transients, hundreds of alarms may be activated in a short time. Hence, to increase the plant safety, this paper proposes a support system based on neurofuzzy that assists alarming and diagnosis systems. Throughout this framework the neurofuzzy fault diagnosis system is employed to fault diagnosis of nuclear reactors. To overcome weak points of both linguistic and neuro learning based approaches, integration between the neural networks and fuzzy logic has been applied by which the
integrated system will inherit the strengths of both approaches.