• Energy Research

This article is to study the static stability of Tunisian electrical network face to many current technical constraints to maintain the security of the entire system power. In this context, we present a study based on the modal analysis of the linearized system. This study allows us to determine the optimum location of power regulators PSS injected at the input of voltage regulator AVR based on a matrix called “participation”. The regulators method residues perform the calculation of these parameters.

This study focused on the use of the non‐dominated sorting genetic algorithm (NSGA‐II) to achieve an optimal power system stabiliser (PSS) parameters for a given operating point with a renewable source of energy so as to increase the system damping and guarantee enough stability margin. The parameters tuning was formulated using an eigenvalue‐based multi‐objective function. In recent years, the changeability and fluctuation of the wind power injected into the network have led to new challenges in small signal stability (SSS). These wind speed change and load demand change perturbations take place routinely and cause the variation of the operating conditions. However, as the conventional PSS is conceived for a fixed operating point in order to obtain the linearised transfer function model, it cannot yield good results when the operating range is too wide. To this end, the adaptive neuro‐fuzzy inference system was proposed to estimate the stabiliser parameters in real time after a learning phase. The nine‐bus Western System Coordinating Council and the obtained simulations results were assessed using Matlab/Simulink package. The validity of the proposed methodology was checked through the PSS parameters evolution simulation for daily load forecast curves and monthly wind speed prediction curves.

Abstract Three-dimensional investigation has been carried out to simulate buoyancy induced heat transfer and fluid flow as well as entropy creation inside C-shaped enclosure charged with based water CNT–Al2O3 (15–85%) hybrid nanofluid. Left side is isothermally heated while the vertical portions of the right wall are isothermally cooled. Effects of various parameters on the flow behavior and the produced irreversibilities, namely the cavity aspect ratio (0.1 ≤ Ar ≤ 0.4), Rayleigh number (103 ≤ Ra ≤ 106) and volumetric fraction of hybrid nanofluid (0 ≤ φ ≤ 0.06) have been examined. It was revealed that the aspect ratio is the main controlling parameter of thermal energy transfer and generated entropy. In addition, for specific Ra, adding hybrid nanoparticles leads to the increase of the average Nusselt number while the highest produced entropy is observed with higher Rayleigh number. Moreover, the maximum Bejan number occurred for a shape factor Ar = 0.1 and Ra = 104 disregarding the hybrid nanoparticles volume fraction showing the dominance of thermal irreversibility over the viscous dissipation irreversibility in such conditions.

This paper dealt with the optimal distribution network planning (DNP) under loads growth condition where the Particle Swarm Optimization with Constriction Factor (PSO-CF) was considered. This paper aimed at ensuring that the consumers' load demands which always increase with time can be satisfied in an optimum way by the distribution network reconfiguration (DNR). The planning problem was addressed as a mono-criterion one with reduced power losses cost objective. The radiality, voltages limits, and power balance constraints were taken into consideration in this study. So as to evaluate the active power losses, a load flow technique was carried out. The PSO-CF was tested on IEEE-10 bus. All simulation studies and results showed the algorithm efficiency and capability to fulfill good results.

Power system stabilizers (PSSs) are generally used to solve the low-frequency oscillation problem. To overcome this type of oscillation, this paper presented a new method by using the genetic algorithm (GA) to identify PSS settings. The tuning of PSS parameters was formulated relying on an eigenvalue-based objective function aiming at maximizing the stability margin. This was achieved by increasing the sum of the squares of negative real parts of the system eigenvalues. The small disruptions in the form of load change take place routinely; the controller parameters should be adjusted to the changing conditions. To remedy this defect, an adjustment of parameters as a function of the load was required. Thus, a neuronal model by using a historical database determined by the GA solutions for various load levels can approximate the simulation studies, since it could estimate the stabilizer parameters in real time after the learning phase. The validity of the proposed technique was checked through the evolution simulation of the regulator parameters for a load forecast curve. These concepts were discussed in details on a multi-machine network Western System Coordinating Council (WSCC) comprising three generators and nine nodes. The eigenvalue analysis and time domain simulation results were presented at different operating conditions and under various disturbances in order to show the effectiveness of this study.

The interconnections between the national power systems was developed parallel to networks of each country. Originally, the interconnections used to get outside help in case of failure could affect the security of a country national electricity supply. In electrical power networks small oscillations appear from time to time. These oscillations concern the quantities determining the equilibrium point of the system, and following which, system stability and system behaviors are influenced. To improve system behaviors and dynamic stability it is necessary to minimize these transient states. The objective of our study is, first, to check the static stability of the high voltage power to small perturbations of electrical network In this context, we present a study based on the modal analysis of the linearized system. The results of this analysis allow us to obtain the optimal placement of power regulators PSS injected at the input of voltage regulator AVR based on the matrix of participation. The calculation of these parameters is performed by the regulators method residues. In this paper, the study is structured around one main objective: to have a real interconnection Tunisia-Libya with a stable, efficient and solider operation.

L'irradiation horizontale globale prévue (GHI) peut aider à la conception, au dimensionnement et à l'analyse des performances des systèmes photovoltaïques (PV), y compris les systèmes de pompage PV à eau utilisés pour les applications d'irrigation. Dans cet article, divers modèles de réseaux neuronaux profonds (DNN) pour la prédiction à un jour du GHI à Hail city (Arabie saoudite) sont développés et étudiés. Les modèles DNN considérés comprennent la mémoire à long terme (LSTM), le LSTM bidirectionnel (BiLSTM), l'unité récurrente fermée (GRU), le GRU bidirectionnel (Bi-GRU), le réseau neuronal convolutionnel unidimensionnel (CNN 1D ) et d'autres configurations hybrides telles que CNN-LSTM et CNN-BiLSTM.A. L'ensemble de données des enregistrements quotidiens GHI collectés entre le 1er janvier 2000 et le 30 juin 2020 auprès de la National Aeronautics and Space Administration (NASA) à un endroit aride (Hail, Arabie Saoudite) est utilisé pour développer et comparer les modèles basés sur DNN ci-dessus. Les paramètres affectant la précision des modèles ont également été analysés en profondeur. Seules les valeurs historiques du GHI quotidien ont été utilisées pour construire les modèles basés sur DNN, tandis que des paramètres météorologiques supplémentaires tels que la température de l'air, la vitesse du vent, la direction du vent, la pression atmosphérique et l'humidité relative ne sont pas pris en compte dans ce travail. La bibliothèque Keras et le langage Python ont été utilisés utilisé pour développer et comparer les modèles de prévision GHI. Les métriques d'évaluation telles que le coefficient de corrélation (r), l'erreur absolue moyenne en pourcentage (MAPE), l'erreur absolue moyenne (MAE), la fonction de distribution cumulative (CDF) et l'écart type (σ ) sont choisies pour évaluer la performance des modèles de prévision. Les résultats obtenus ont montré que les modèles DNN ont fourni de bonnes performances à l'échelle mondiale avec une valeur maximale atteinte de r = 96 %, pour la prévision quotidienne GHI. La irradiación horizontal global pronosticada (GHI) puede ayudar a diseñar, dimensionar y analizar el rendimiento de los sistemas fotovoltaicos (PV), incluidos los sistemas de bombeo de agua PV utilizados para aplicaciones de riego. En este documento, se desarrollan e investigan varios modelos de redes neuronales profundas (DNN) para la predicción de un día de anticipación de GHI en la ciudad de Hail (Arabia Saudita). Los modelos DNN considerados incluyen memoria a largo plazo (LSTM), LSTM bidireccional (BiLSTM), unidad recurrente cerrada (GRU), GRU bidireccional (Bi-GRU), red neuronal convolucional unidimensional (CNN 1D ) y otras configuraciones híbridas como CNN-LSTM y CNN-BiLSTM. Un conjunto de datos de grabaciones diarias de GHI recopiladas durante el 1 de enero de 2000 al 30 de junio de 2020 de la Administración Nacional de Aeronáutica y del Espacio (NASA) en una ubicación árida (Hail, Arabia Saudita) se utiliza para desarrollar y comparar los modelos basados en DNN anteriores. Los parámetros que afectan la precisión de los modelos también se han analizado profundamente. Solo se han utilizado valores históricos de GHI diarios para construir los modelos basados en DNN, mientras que los parámetros climáticos adicionales como la temperatura del aire, la velocidad del viento, la dirección del viento, la presión atmosférica y la humedad relativa no se consideran en este trabajo. Biblioteca Keras y lenguaje Python han sido utilizado para desarrollar y comparar los modelos de pronóstico de GHI. Las métricas de evaluación como el coeficiente de correlación (r), el error porcentual absoluto medio (MAPE), el error absoluto medio (MAE), la función de distribución acumulativa (CDF) y la desviación estándar (σ ) se optan para evaluar el rendimiento de los modelos de predicción. Los resultados obtenidos mostraron que los modelos DNN han proporcionado un buen rendimiento a nivel mundial con un valor máximo alcanzado de r = 96%, para el pronóstico diario de GHI. Forecasted global horizontal irradiation (GHI) can help for designing, sizing and performances analysis of photovoltaic (PV) systems including water PV pumping systems used for irrigation applications.In this paper, various deep neural networks (DNN) models for one day-ahead prediction of GHI at Hail city (Saudi Arabia) are developed and investigated.The considered DNN models include long-shortterm memory (LSTM), bidirectional-LSTM (BiLSTM), gated recurrent unit (GRU), bidirectional-GRU (Bi-GRU), one-dimensional convolutional neural network (CNN 1D ) and other hybrid configurations such as CNN-LSTM and CNN-BiLSTM.A dataset of daily GHI recordings collected during January 1, 2000 to June 30, 2020 from National Aeronautics and Space Administration (NASA) at an arid location (Hail, Saudi Arabia) is used to develop and compare the above DNN-based models.The parameters affecting the accuracy of the models have been also deeply analyzed.Only historical values of daily GHI have been used to build the DNN-based models whereas additional weather parameters such as air temperature, wind speed, wind direction, atmospheric pressure and relative humidity are not considered in this work.Keras library and Python language have been used to develop and compare the GHI forecasting models.The evaluation metrics such as correlation coefficient (r), Mean Absolute Percent Error (MAPE), Mean Absolute Error (MAE), cumulative distribution function (CDF) and standard deviation (σ ) are opted to evaluate the performance of the prediction models.The obtained results showed that the DNN models have provided globally good performances with a maximum reached value of r = 96%, for daily GHI forecasting. يمكن أن يساعد الإشعاع الأفقي العالمي المتوقع (GHI) في تصميم وتحجيم وتحليل أداء الأنظمة الكهروضوئية (PV) بما في ذلك أنظمة ضخ المياه الكهروضوئية المستخدمة في تطبيقات الري. في هذه الورقة، يتم تطوير نماذج مختلفة للشبكات العصبية العميقة (DNN) للتنبؤ قبل يوم واحد من GHI في مدينة حائل (المملكة العربية السعودية) والتحقيق فيها. تشمل نماذج DNN التي يتم النظر فيها الذاكرة قصيرة المدى (LSTM)، ثنائية الاتجاه - LSTM (BiLSTM)، وحدة متكررة مسورة (GRU)، ثنائية الاتجاه - GRU (Bi - GRU)، شبكة عصبية التفافية أحادية البعد (CNN 1D ) والتكوينات الهجينة الأخرى مثل CNN - LSTM و CNN - BiLSTM. يتم استخدام مجموعة بيانات من تسجيلات GHI اليومية التي تم جمعها خلال الفترة من 1 يناير 2000 إلى 30 يونيو 2020 من الإدارة الوطنية للملاحة الجوية والفضاء (ناسا) في موقع قاحل (حائل، المملكة العربية السعودية) لتطوير ومقارنة النماذج القائمة على DNN المذكورة أعلاه. كما تم تحليل المعلمات التي تؤثر على دقة النماذج بعمق. تم استخدام القيم التاريخية فقط لـ GHI اليومية لبناء النماذج القائمة على DNN بينما لا يتم النظر في معلمات الطقس الإضافية مثل درجة حرارة الهواء وسرعة الرياح واتجاه الرياح والضغط الجوي والرطوبة النسبية في هذا العمل. تستخدم لتطوير ومقارنة نماذج التنبؤ بمؤشر GHI. يتم اختيار مقاييس التقييم مثل معامل الارتباط (r)، متوسط النسبة المئوية المطلقة (MAPE)، متوسط الخطأ المطلق (MAE)، وظيفة التوزيع التراكمي (CDF) والانحراف المعياري (σ ) لتقييم أداء نماذج التنبؤ. أظهرت النتائج التي تم الحصول عليها أن نماذج DNN قد قدمت أداءً جيدًا عالميًا بحد أقصى للقيمة التي تم الوصول إليها r = 96 ٪، للتنبؤ اليومي بمؤشر GHI.

This paper presents a Multi-objective Economic Dispatch and Unit Commitment Problems (EDUCP) Considering valve point effect Using heuristic algorithm (MOPSO). The proposed method can be applied to solve dynamic power dispatch problem (with specific period such as 24 h) and to solve unit commitment problem. The proposed method also can be combined with other metaheuristic or classical methods to create more powerful optimization technique. The test systems with up to 10 generating units have been used to show the performance of MOPSO. A ten-unit test system with nonsmooth fuel cost function is used to illustrate the effectiveness of the proposed method compared with those obtained from ECE, MDE, HSP and HBPSO.

This paper presents a study of performances evaluation of lead-lag Power System Stabilizers ‘PSSs’ equipped with adaptive mechanisms performed on the basis of artificial intelligence techniques (neuronal networks, and neuro-fuzzy networks). These adaptive and intelligent PSSs with on-line self-tuned parameters have allowed a good damping of rotoric oscillations for various operating conditions and disturbances. Based on a linearized model of a multimachine power system, an optimized design of lead-lag PSSs has been performed using NSGA-II optimization technique.