Voltage Stability Enhancement Based on Optimal Allocation of Shunt Compensation Devices Using Lightning attachment procedure optimization

This paper proposes a combined approach to determine the optimal allocation of different shunt compensation devices (shunt capacitor, static var compensator, and static synchronous compensator) in power systems. The developed approach is a combination between Lightning Attachment Procedure Optimization (LAPO) and loss sensitivity indices (LSIs). Different objective functions such as enhancement of voltage stability index, improvement of voltage profile and minimization of total power losses are considered. Two loss sensitivity indices (LSIs) are developed to reduce the search space in all buses and the total computation time. The developed algorithm is validated using standard IEEE 14-bus and IEEE 30-bus test systems. The developed algorithm successes to achieve the objective functions with the better performance compared with other wellknown optimization techniques such as Teaching learning-based optimization (TLBO), genetic algorithm (GA) and particle swarm optimization (PSO)

Impacts of midpoint FACTS controllers on the coordiantion between generator phase backup protection and generator capability limits

The thesis reports the results of comprehensive studies carried out to explore the impact of midpoint FACTS Controllers (STATCOM and SVC) on the generator distance phase backup protection in order to identify important issues that protection engineers need to consider when designing and setting a generator protection system. In addition, practical, feasible and simple solutions to mitigate the adverse impact of midpoint FACTS Controllers on the generator distance phase backup protection are explored. The results of these studies show that midpoint FACTS Controllers have an adverse effect on the generator distance phase backup protection. This adverse effect, which can be in the form of underreach, overreach or a time delay, varies according to the fault type, fault location and generator loading. Moreover, it has been found that the adverse effect of the midpoint FACTS Controllers extends to affect the coordination between the generator distance phase backup protection and the generator steady-state overexcited capability limit. The Support Vector Machines classification technique is proposed as a replacement for the existing generator distance phase backup protection relay in order to alleviate potential problems. It has been demonstrated that this technique is a very promising solution, as it is fast, reliable and has a high performance efficiency. This will result in enhancing the coordination between the generator phase backup protection and the generator steady-state overexcited capability limit in the presence of midpoint FACTS Controllers. The thesis also presents the results of investigations carried out to explore the impact of the generator distance phase backup protection relay on the generator overexcitation thermal capability. The results of these investigations reveal that with the relay settings according to the current standards, the generator is over-protected and the generator distance phase backup protection relay restricts the generator overexcitation thermal capability during system disturbances. This restriction does not allow the supply of the maximum reactive power of the generating unit during such events. The restriction on the generator overexcitation thermal capability caused by the generator distance phase backup protection relay highlights the necessity to revise the relay settings. The proposed solution in this thesis is to reduce the generator distance phase backup protection relay reach in order to provide secure performance during system disturbances

Effets d’éthanol sur la fertilité du lapin mâle adulte Oryctolagus cuniculus

La consommation chronique d'éthanol est associée à des troubles de la reproduction chez  l’homme. Pour cela, l’objectif de ce travail est d’évaluer chez le lapin mâle adulte Oryctolagus cuniculus l’effet de la consommation chronique d’éthanol sur la reproduction. L’alcool concentré à 20%, 25% et 30% a été administré au lapin mâle par gavage pendant six semaines successives. Après sacrifice des animaux, les testicules et l’épididyme ont été prélevés afin d’évaluer certains paramètres de la reproduction, alors que le sang a été recueilli pour le dosage de la testostérone. Les résultats obtenus montrent une diminution de la mobilité, la vitesse, la vitalité et la concentration des spermatozoïdes, accompagnée d’une augmentation  de leur nombre malformés chez les trois lots d’animaux traités par rapport au lot témoin. Par ailleurs, le traitement à l’alcool a entrainé une diminution du poids des testicules et de l’épididyme, ainsi qu’une diminution du taux de la testostérone chez les animaux des groupes traités comparés au groupe témoin. Les résultats montrent clairement que l’éthanol exerce un effet toxique sur la fertilité du lapin mâle.© 2015 International Formulae Group. All rights reserved.Mots clés: Alcool, épididyme, spermatozoïde, testicule, testostéroneEnglish AbstractChronic ethanol consumption is associated with reproductive disorders in humans. Therefore,  the objective of this study was to evaluate in adult male rabbit Oryctolagus cuniculus the effect of chronic ethanol consumption on reproduction. The concentrated alcohol 20%, 25% and 30% was administered to male rabbits by gavage for six successive weeks. After sacrificing the animals, testis and epididymis were collected to assess certain parameters of the reproduction, while the blood was collected for the determination of testosterone. The results show a decrease in mobility, speed, vitality and spermatozoa concentration, accompanied by an increase in the number of malformed spermatozoa in three batches of treated animals compared to the control group. Moreover, the treatment with alcohol resulted in a decreased weight of the testes and epididymis, and decreased testosterone levels in animals treated groups compared to the control group. The results clearly show that ethanol exerts a toxic effect on the fertility of male rabbit.© 2015 International Formulae Group. All rights reserved.Keywords: Alcohol, epididymis, spermatozoa, testis, testosterone

Voltage Stability Assessment of Radial Distribution Systems Including Optimal Allocation of Distributed Generators

Assessment of power systems voltage stability is considered an important assignment for the operation and planning of power system. In this paper, a voltage stability study using Continuous Power Flow (CPF) is introduced to evaluate the impact of Distribution Generator (DG) on radial distribution systems. On the way to allocate the DG, a hybrid between the Voltage Stability Index (VSI) and Whale Optimization Algorithm (WOA) is developed. The main purpose of using VSI is to find the most sensitive buses for allocating the DG in the system. Hence, Fuzzy logic control with the Normalized VSI (NVSI) and the voltage magnitude at each bus are used to determine the candidate buses. However, the best DG size is calculated using WOA. Four standard radial distribution systems are used in this paper; 12, 33, 69, and 85-bus. The developed hybrid optimization method is compared with other existing analytical and metaheuristic optimization techniques to prove its efficiency. The results prove the ability of the developed method in the allocation of DG. In addition, the influence of the DG integration on enhancing the voltage stability through injecting the proper active and reactive powers is studied

Tree Growth Algorithm for Parameter Identification of Proton Exchange Membrane Fuel Cell Models

Demonstrating an accurate mathematical model is a mandatory issue for realistic simulation, optimization and performance evaluation of proton exchange membrane fuel cells (PEMFCs). The main goal of this study is to demonstrate a precise mathematical model of PEMFCs through estimating the optimal values of the unknown parameters of these cells. In this paper, an efficient optimization technique, namely, Tree Growth Algorithm (TGA) is applied for extracting the optimal parameters of different PEMFC stacks. The total of the squared deviations (TSD) between the experimentally measured data and the estimated ones is adopted as the objective function. The effectiveness of the developed parameter identification algorithm is validated through four case studies of commercial PEMFC stacks under various operating conditions. Moreover, comprehensive comparisons with other optimization algorithms under the same study cases are demonstrated. Statistical analysis is presented to evaluate the accuracy and reliability of the developed algorithm in solving the studied optimization problem

INSECTICIDAL AND ANTIOXIDANT ACTIVITIES OF AQUEOUS EXTRACTS OF TWO ALGERIAN MEDICINAL PLANTS

In this work, we determined the insecticidal activity and antioxidant activity of aqueous extracts of Nerium oleander (Apocynaceae) leaves and Peganum harmala (Zygophyllaceae) seeds, two well-known Algerian medicinal plants. Four concentrations of each extract were applied in total randomization by spraying directly on the eggs and larvae of Ectomyelois ceratoniae (Zeller, 1879) (Lepidoptera: Pyralidae) under laboratory conditions. Our findings revealed that eggs hatching after four days were not affected by the aqueous extract, with a rate of 54% of hatching eggs in both control and treated eggs. Additionally, toxicity by contact on larvae was not evident and the mortality percentage did not exceed 8%, regardless of the extract plant and concentration. Phytochemical screening showed a slight presence of terpenes and saponins and an absence of alkaloids. However, polyphenols were present in medium concentrations in the aqueous extracts of both plants. The antioxidant activities of N. oleander and P. harmala extracts were found to be 71.80 and 72.94%, respectively. Total phenolic content (TPC) and total flavonoid content (TFC) of the studied extracts were 50.69 mg gallic acid equivalent (GAE)/100 g dry weight (DW) and 3.55 in terms of quercetin equivalent (QE)/100 g DW, respectively, in N. oleander. In P. harmala, the TPC and TFC were 52.30 mg GAE/100 g DW and 3.49 mg QE/100 g DW, respectively. Our study clearly shows the limited insecticidal effect of the aqueous extracts, although they showed an interesting antioxidant potential, which could help to decrease the incidence of oxidative stress-induced damage

Optimal Performance of Doubly Fed Induction Generator Wind Farm Using Multi-Objective Genetic Algorithm

The main purpose of this paper is allowing doubly fed induction generator wind farms (DFIG), which are connected to power system, to effectively participate in feeding electrical loads. The oscillation in power system is one of the challenges of the interconnection of wind farms to the grid. The model of DFIG contains several gains which need to be achieved with optimal values. This aim can be accomplished using an optimization algorithm in order to obtain the best performance. The multi-objective optimization algorithm is used to determine the optimal control system gains under several objectives. In this paper, a multi-objective genetic algorithm is applied to the DFIG model to determine the optimal values of the gains of DFIG control system. In order to point out the contribution of this work; the performance of optimized DFIG model is compared with the non-optimized model of DFIG. The results show that the optimized model of DFIG has better performance over the non-optimized DFIG model

Control and Protection of MMC-Based HVDC Systems: A Review

The voltage source converter (VSC) based HVDC (high voltage direct current system) offers the possibility to integrate other renewable energy sources (RES) into the electrical grid, and allows power flow reversal capability. These appealing features of VSC technology led to the further development of multi-terminal direct current (MTDC) systems. MTDC grids provide the possibility of interconnection between conventional power systems and other large-scale offshore sources like wind and solar systems. The modular multilevel converter (MMC) has become a popular technology in the development of the VSC-MTDC system due to its salient features such as modularity and scalability. Although, the employment of MMC converter in the MTDC system improves the overall system performance. However, there are some technical challenges related to its operation, control, modeling and protection that need to be addressed. This paper mainly provides a comprehensive review and investigation of the control and protection of the MMC-based MTDC system. In addition, the issues and challenges associated with the development of the MMC-MTDC system have been discussed in this paper. It majorly covers the control schemes that provide the AC system support and state-of-the-art relaying algorithm/ dc fault detection and location algorithms. Different types of dc fault detection and location algorithms presented in the literature have been reviewed, such as local measurement-based, communication-based, traveling wave-based and artificial intelligence-based. Characteristics of the protection techniques are compared and analyzed in terms of various scenarios such as implementation in CBs, system configuration, selectivity, and robustness. Finally, future challenges and issues regarding the development of the MTDC system have been discussed in detail

Improvement of active distribution systems with high penetration capacities of shunt reactive compensators and distributed generators using Bald Eagle Search

This work proposes an intelligent allocation of distributed generation (DG) units and shunt reactive compensators (SRC) with high penetration capacities into distribution systems for power loss mitigation using the Bald Eagle Search (BES) optimization algorithm. The intelligent allocation causes a reduction in voltage variations and enhances the voltage stability of the systems. The SRC units include shunt capacitors (SC), Static Var Compensators (SVC), and Distribution Static Compensators (DSTATCOM), which are determined according to their capacities. The optimization study includes the 33-bus and the 118-bus distribution systems as medium to large systems. Performance parameters, including the reactive power loss, Total Voltage Deviation (TVD), and Stability Index (SI), besides the power loss, are recorded for each optimization case study. When the BES algorithm optimizes 1, 2, and 3 DG units operating at optimal power factor (OPF) into the 33-bus systems, percentage reductions of power loss reach 67.84%, 86.49%, and 94.44%, respectively. Reductions of 28.26%, 34.47%, 35.24%, and 35.44% are achieved in power loss while optimizing 1, 3, 5, and 7 SRC units. With a combination of DG/SRC units, the power loss reductions achieve 72.30%, 93.89%, and 97.49%, optimizing 1, 3, and 5 pairs of them. Similar reductions are achieved for the rest of the performance parameters. With high penetration of compensators into the 118-bus system, the percentage reductions of power loss are 29.14%, 73.27%, 83.72%, 90.14%, and 93.41% for optimal allocations of 1, 3, 5, 7, and 9 DG units operating at OPF. The reduction reaches 11.15%, 39.08% with 1 and 21 devices when optimizing the SRC. When DG SRC units are optimized together, power loss turns out to be 32.83%, 73.31%, 83.32%, 88.52%, and 91.29% with 1, 3, 5, 7, and 9 pairs of them. The approach leads to an enhanced voltage profile near an acceptable range of bus voltages, reduces the voltage fluctuation substantially, and enhances the system stability. The study also ensures the BES algorithm’s capability to solve these nonlinear optimization problems with high decision-variable numbers