Global Journal of Technology and Optimization

A developed mathematical critical voltage proximity index is investigated in this paper. Mathematical description of the index is provided. Background theory on established statistical indices, as well as mathematical indices recently developed, are presented, highlighting the successful application of the index in distribution systems, featuring low X/R ratio values, and the need for investigation of the index at transmission level. The index is applied on a transmission test system and verified for its compatibility through the use of tap changing transformers as voltage sag mitigation scheme. Three induction motor load variation scenarios are investigated in order to establish the effectiveness and accuracy of the index. The development of a multiple tap changing controller scheme within PSCAD software is also described. The index improves the power quality of a system, through providing a tool for on-line voltage sag mitigation, featuring multiple potential applications.

Today, most remote areas in UAE are fully powered using diesel generators; however, high operating cost and recent concerns from government and activists are rising due to pollution and vibrations from diesel generators, which are affecting the desert’s landscape and demography. Therefore, the objective of this study is to provide remote customers with viable hybrid-system (renewable/variable speed diesel generator) solution rather than stand-alone constant speed diesel generator. The study is based on measured load requirements of an existing safari camp in Abu Dhabi over a whole year. HOMER software has been utilized to simulate several alternatives for the case study. The selected solution is based on the system cost and the availability of the renewable energy resource at the location of interest (e.g., wind speed and solar irradiance). The study can be extended to remote farms within UAE.

Presently, there is no method of producing cost-effective hydrogen, environmentally-friendly, and suitable for a largescale production. Thermo-chemical cycles, represented essentially by the hybrid-sulphur cycle and the electrolysis of water, are the most promising processes for ‘clean’ hydrogen mass production for the future. This paper presents a new cleaner process for hydrogen mass production; the idea consists in coupling the electrolysis phenomenon upstream to the sulphuric acid plant. In other words, this proposition consists in modifying the hybrid cycle Westinghouse by the elimination of the sulphuric acid decomposition stage, which corresponds to 61% of the energy distribution of this cycle. To confirm the efficiency of this process, a mass balance study is carried out on sulphuric acid plant, using a double contact/double absorption process, this study demonstrates that this new method can treat 8 t.day-1 of sulphur dioxide, recover 12 t.day-1 of sulphuric acid 50%wt and produce 6889 m3.day-1 of hydrogen. The application of this idea can achieve economical and environmental benefits. It is concluded that the usage of this electrochemical process can significantly reduce the SO2 air pollution in Gabes (South Tunisia) by the elimination of 46 .94 t. day-1. The results are ambitious for future application of the new process which can succeed in the realisation of 3.92 million dollars of gain every day.

Solving systems of nonlinear equations is a relatively complicated problem for which a number of different approaches have been presented. In this paper, a new algorithm is proposed for the solutions of systems of nonlinear equations. This algorithm uses a combination of the gradient and the Newton’s methods. A novel dynamic combinatory is developed to determine the contribution of the methods in the combination. Also, by using some parameters in the proposed algorithm, this contribution is adjusted. We use the gradient method due to its global convergence property, and the Newton’s method to speed up the convergence rate. We consider two different combinations. In the first one, a step length is determined only along the gradient direction. The second one is finding a step length along both the gradient and the Newton’s directions. The performance of the proposed algorithm in comparison to the Newton’s method, the gradient method and an existing combination method is explored on several well known test problems in solving systems of nonlinear equations. The numerical results provide evidence that the proposed combination algorithm is generally more robust and efficient than other mentioned methods on some important and difficult problems.

The unit commitment problem has been broadly studied in recent years in many researches. However, this is not all of the important tasks for independent system operator. One of the most important tasks is the optimal provision of primary frequency regulation reserve with the lowest cost that should be considered in the unit commitment problem. Frequency control in power system, as an ancillary service, has closed dependence to hourly scheduling of energy. In this paper, a novel approach is proposed to solve simultaneous scheduling of energy and primary reserve using genetic algorithm. The proposed methodology is fast and simple against conventional methods. In addition, applicability of scheduled primary reserve has been considered in optimization process. Finally, simulation results for a 17 unit case study are presented in comparison with a related work. The simulation results using Matlab 2009a are presented which verify the effectiveness and robustness of the proposed method.

In this paper some initial results concerning the evolution of flame propagation in 4-valve engines with tilted valves were presented. Results were obtained by dint of multidimensional modeling of reactive flows in arbitrary geometry with moving boundaries. During induction fluid flow pattern was characterized with organized tumble motion followed by small but clearly legible deterioration in the vicinity of BDC. During compression the fluid flow pattern is entirely threedimensional and fully controlled by vortex motion located in the central part of the chamber. The effect of turbulence model variation on flame propagation was tackled as well. Namely, some results obtained with eddy-viscosity model i.e. standard k-ε model were compared with results obtained with k-ξ-f model of turbulence in domain of 4-valve engine in-cylinder flow. Some interesting results emerged rendering impetus for further quest in the near future. In the case of combustion all differences ensuing from turbulence model variation, encountered in the case of non-reactive flow were annihilated entirely. Namely the interplay between fluid flow pattern and flame propagation is invariant as regards both turbulence models applied

In this paper, the thermal field of underground power cable is solved using two intelligent techniques which are newly introduced for thermal assessment of power cables. A backpropagation neural network (BPNN) and an adaptive neuro-fuzzy inference system (ANFIS) models were developed to predict the cable temperature under geometrical parameter variations. The effect of cable spacing and cable burial depth on cable ampacity is investigated. The two models are trained using an input-output pattern generated using finite element (FE) method, which is extensively used in this field. Furthermore, a portion of the FEgenerated output results, which have not been provided to the models – as input data - in the training phase, were utilized to compare the cable temperature of the three methods (FE, ANN and ANFIS). The results of the two intelligent methods show high agreement with the finite element solution, which confirms that introducing intelligent techniques provides a reliable and simple alternative approach for the thermal field evaluation by avoiding the numerous computational complexities of the numerical methods