Jaleleddine Ben Hadj Slama

Comparative study between two and three-level topologies of grid connected photovoltaic converters

The main objective of this paper is to achieve a comparative study between two and three-level converters used in transformerless grid connected two-stage photovoltaic systems. For this purpose, a numerical model of the conversion system has been implemented in Matlab/Simulink software. It consists of a PV array feeding a DC/DC converter as well as a three-phase voltage source converter that ensures the power transfer to the grid through a line inductor. The simulation results showed that the three-level voltage source converter has better performance than the two-level topology in terms of line current harmonic distortion (THD) as well as the line inductors volume.

Wind speed and direction prediction for wind farms using support vector regression

Predicting wind speed and direction is one of the most important and critic tasks in a wind farm, since wind turbine blades motion and thus energy production is closely related to wind behaviour. Machine learning techniques are often used to predict the non-linear wind evolution. In this context, this paper proposes a short term wind data prediction model based on support vector machines in their regression mode, which have the advantage of being simple, fast and well adapted for the short term. This research tries also to prove how wind direction may influence power generation, and why it is important to predict it. A real data set of wind speed and direction historical values is used, from Sidi Daoud wind farm, north-eastern Tunisia, in order to evaluate the proposed model. This forecasting system predicts wind speed and direction for the short term, from one to 10 hours in advance, using a set of past samples.

Power RF N-LDMOS ageing effect on conducted electromagnetic interferences

Using semiconductor components in power electronics (static converters) circuits has many objectives: high frequency switching, high current, high voltage, increase their operating temperature and reduce the volume of equipment. However, working with these conditions for semiconductor components increases the electromagnetic interferences (EMI) that can have a significant impact on the neighboring systems. This paper presents a study of the ageing (electrical and/or thermal) of Power Radio Frequency Transistors RF N-LDM.S effect on conducted electromagnetic interferences emitted by DC-DC converter circuits. Conducted electromagnetic interference characterizations are performed for circuits using safe and aged power RF N-LDM.S. Through examination of experimental results, an accelerated ageing effect on the LDM.S transistor shows variations on conducted electromagnetic disturbance in common and differential mode voltage.

Development and validation of analytic equations of the electromagnetic fields radiated by the elementary dipoles in time domain

In this paper, we will present the development of the analytic equations and the corresponding calculating code to models and evaluate the electromagnetic field radiated by the elementary dipoles in time domain. Results obtained with analytic equations are compared to those obtained after simulations made with software based on numerical method in the time domain. Then, they are compared to results obtained with analytic and numerical methods working in frequency domain. In this paper, the development of analytic resolution is carried out in order to implement the electromagnetic inverse method in time domain.

Random forests model for one day ahead load forecasting

Short term load forecasting is one of the most important tasks for power suppliers, and it is getting more important with deregulation of electricity market and emergence of smart grids. This paper proposes a load prediction model of one day ahead with resolution of one hour, using regression random forests. With information about season, temperature, type of the day and hourly load, a training process is performed to build the adopted model. A real load data set from Tunisian Power Company is used for test, and special attention is paid to the load profile which is specific to warm countries with excessive and unstable demand in summer. The results reflect accuracy and effectiveness of the proposed method, keeping low prediction error for long test periods.

Enhancement of Time-Domain Electromagnetic Inverse Method for Modeling Circuits Radiations

To ensure the reliability and safety of the modern electronic systems face of these electromagnetic interference which are becoming more and more important, modeling methods based on the emissions in the near field of these systems are needed. However, the developed methods and in particular the electromagnetic inverse method in the frequency domain have several limitations to model and characterize the systems which emit a nonsinusoidal electromagnetic radiation. To cope with these limitations, in this paper, the electromagnetic inverse method in the time domain has been developed. Using measured near-field cartography above the studied system, the method, based on genetic algorithms, consists in identifying equivalent emitting dipoles. The identification traverses the entire mapping by identifying all sources from the most intense to the lowest source. The proposed method has been validated, first, using calculated cartographies above known dipoles and, second, using measured cartographies above actual dc-dc converters. A very good agreement has been observed between the near magnetic field cartography calculated using the obtained model and thats emitted by the studied system. The proposed method can be used for the identification of equivalent emitting sources of systems excited by nonsinusoidal currents in a widely lowest time as that of the frequency method.

Design and control of a grid-tied three-phase three-level diode clamped single-stage photovoltaic converter

This paper introduces a single-stage grid-connected photovoltaic power conversion system based on a three-phase three-level Neutral Point Clamped (NPC) converter. The main benefits of the proposed structure are the elimination of the intermediate DC/DC power conversion stage that is usually used to boost the dc-voltage and ensure MPPT operation. Therefore, two control schemes based on a current controller and an MPPT algorithm are handled in only one processing stage. The MPPT algorithm computes in real-time the dc voltage that should be applied across the PV generator so as to extract the maximum power. The output of the MPPT algorithm is thereafter considered as a reference of a current controller that should perform a perfect tracking of the dc-voltage reference and also near unity input power factor operation. The proposed photovoltaic power conversion topology and control method are tested by numerical simulations. The obtained results demonstrate that the designed PV conversion system provides effective response in steady state, fast and perfect tracking of the maximum power point, and robust in case of a partial shading.

Time domain electromagnetic inverse method for non-sinusoidal circuits

In this paper, we propose a new method of an electromagnetic compatibility study. The electromagnetic inverse method in the time domain is proposed to analyze the electromagnetic radiation of power electronic circuits which emit signals that are not sinusoidal. Using measured near-field cartography above the studied circuit, the method, based on genetic algorithms, consists in identifying the dipole sources. To validate the proposed method, we have applied it to theoretical temporal signals emitted by the known electric and magnetic dipoles. The obtained results show a good agreement between the cartography of the near magnetic field, obtained by the developed model, and the calculated one. The results allow us to conclude that the proposed method is suitable for the identification of equivalent-source structures excited by different current forms.

Genetic algorithm based geometry optimization of inductively coupled printed spiral coils for remote powering of electronic implantable devices

Electronic biomedical implantable devices need powering to perform. Among the main reported approaches, inductive links are the most commonly used method for remote powering of such devices. Power efficiency is the most important characteristic to be considered when designing inductive links to transfer energy to implantable devices. The maximum power efficiency is obtained for maximum coupling and quality factors of the coils and is generally limited as the coupling between the inductors is usually very small. This paper is dealing with geometry optimization of inductively coupled printed spiral coils for the powering of a given implant system. For this aim, simple mathematical models that approximate coil parameters and link efficiency are derived, and using these models two different approaches are used to provide optimal coil geometries for a maximum efficiency of the link. First an iterative design procedure is implemented then genetic based algorithm optimisation is derived to find the optimal coil geometries of the used coil structure. Theoretical results are verified by simulation using HFSS software. A comparative analysis confirmed the effectiveness of the genetic algorithm based approach to provide the optimal coil geometries.

Contribution of the PSO in the electromagnetic inverse method in terms of convergence and simplicity of implementation

In this paper, we present an electromagnetic inverse particle swarm optimization (PSO)-based method for modeling the electromagnetic radiation of components or systems of power electronics using the near-field technique. The implementation of this method has been applied to the cartography of the magnetic field emitted by different structures. To fully appreciate our approach, the obtained results along with the proposed methods were compared to those obtained by the inverse method, based on the genetic algorithm (GA). Basically, we will compare the results at two levels, theoretical and practical. For the theoretical comparison, both methods are applied to several calculated cartographies of the magnetic field, using the analytical equations of the magnetic and electric dipoles. For the practical comparison, we have used results based on the measurements performed on real systems. The purpose of these comparisons is to show that using the PSO in the electromagnetic inverse method is more interesting than the GA. In fact, the obtained results have shown that the PSO-based method is at least six times faster than the GA-based one.