A. Tounzi

Modeling of A Linear and Rotary Permanent Magnet Actuator

In this paper, we propose to study an electromagnetic actuator which involves linear and/or rotary movements. The studied device is constituted of permanent magnets, iron teethed armature and concentrated coils with a simplified design. The aim of this paper is to study the main electromagnetic features of the actuator using 3D finite element method (FEM). First, the actuator is described and the design choices are given and discussed. Then, the electric and magnetic behaviors (fluxes, forces, etc.) are studied thanks to 3D-FEM analyses. Results are given and compared to measurements.

Improved direct torque control of an induction generator used in a wind conversion system connected to the grid

This paper presents a modulated hysteresis direct torque control (MHDTC) applied to an induction generator (IG) used in wind energy conversion systems (WECs) connected to the electrical grid through a back-to-back converter. The principle of this strategy consists in superposing to the torque reference a triangular signal, as in the PWM strategy, with the desired switching frequency. This new modulated reference is compared to the estimated torque by using a hysteresis controller as in the classical direct torque control (DTC). The aim of this new approach is to lead to a constant frequency and low THD in grid current with a unit power factor and a minimum voltage variation despite the wind variation. To highlight the effectiveness of the proposed method, a comparison was made with classical DTC and field oriented control method (FOC). The obtained simulation results, with a variable wind profile, show an adequate dynamic of the conversion system using the proposed method compared to the classical approaches.

Study of a Stator Current Excited Vernier Reluctance Machine

This paper deals with the study of a stator current excited Vernier reluctance machine. This structure is well known for operating at low speed and high torque. In the first part of this paper, we introduce an energetic model which yields the conditions on teeth and polarity numbers necessary for the smooth running of such a structure. Then, we give the procedure used to design a prototype. The second part is devoted to a brief look at the two-dimensional numerical approach used to model the machine. Finally, we present, and study, the constructed prototype. Different tests are performed, and the experimental values are compared to the calculated ones. We validate the operating principle of the current excited Vernier reluctance machine, and show its potential for low speed direct driven applications

Study of an Electromagnetic Gearbox Involving Two Permanent Magnet Synchronous Machines Using 3-D-FEM

Recently, magnetic gearboxes know a real interest. Due to the use of rare earth magnets, they reach high performances. However, their design is often issue from the mechanical gearbox one and then they do not offer any degree of freedom. In this paper, we propose an electromagnetic gearbox constituted of two electromagnetic structures, one fit inside the other. As each of both structures has its own electrical supply, this introduces two degrees of freedom. Thus, the system can ensure as well the gear operating than that of the clutch. First, the operating of the system is described and the electromagnetic structures introduced. Then, its behavior is studied using a numerical model based on 3-D-finite-element method (FEM). Different results given by 3-D analysis are presented.

Control strategies for an autonomous induction generator taking the saturation effect into account

In this paper, we present the voltage built up process and a control to regulate the DC voltage of an isolated induction generator connected to a rectifier and driven by a variable speed wind turbine. Two strategies, based on the rotor flux oriented vector control, are proposed. Both rotor flux and DC bus voltage are regulated by two control loops which operate in parallel. The model used for the induction generator is obtained by the application of the Park transform. This model takes account of the saturation effect by a variable magnetizing inductance function of the current. The inductance variation is described by a polynomial function. The proposed control strategies are validated through simulations. The obtained results are presented and discussed.

Calculation of Iron Losses in Solid Rotor Induction Machine Using FEM

This paper presents a study on iron loss estimation for a solid rotor induction motor fed by pulsewidth modulated supply. The iron losses are often determined using an a posteriori method that can lead to more or less important deviations, compared with measurements, depending on the used models and implementation techniques. The methodology proposed here consists of computing the iron losses with an analytical method implemented in a post-processing of a 2-D finite-element analysis. Different implementation techniques are used to investigate the impact of the model on the iron loss.

Study of synchronous generator eccentricities using analytical approach and FEM

This paper deals with the study of rotor turbogenerator eccentricities using an analytical approach and FEM. First, we present the cases of eccentricities and the method, based on the measure of the flux density in the air-gap, used to detect the faults. Both models, the analytical approach and the numerical one are then introduced. Using these models, static, dynamic and combined eccentricities are studied at no load. The results obtained by both approaches are compared and the limits of the analytical model are underlined relatively to the effect of the non linearity of the magnetic material characteristic and the induced eddy currents.

3-D approaches to determine the end winding inductances of a permanent-magnet linear synchronous motor

This paper deals with the determination of the end winding inductance of a permanent-magnet linear synchronous motor (PMLSM). The methods to determine the inductances in three dimensions are given for both classical complementary formulations. In a first step, an elementary cell of the structure is modeled using both methods and the results are analyzed and discussed. In the second step, the complete structure is studied in two and three dimensions using only the scalar potential formulation to limit the computation time. The numerical results are compared with experimental ones.

Stochastic modeling of the pull-in voltage in a MEMS beam structure

This work presents a stochastic approach to model the pull-in voltage in a MEMS (Micro Electro Mechanical Systems) beam structure, using Monte Carlo (MC) simulations. The pull-in model is a coupled FEM (Finite Element Method) electrostatic and analytical mechanical model. The shape and material properties of the MEMS constitute the random variables for the MC simulations. The results allow finding the influence of each input parameter and the distribution of the pull-in voltage.

Maximum Power Point Tracking Based Hybrid Hill-climb Search Method Applied to Wind Energy Conversion System

Abstract Due to the instantaneous variation of wind speed, it is suitable to determine the optimal rotational speed that ensures maximum energy efficiency. This article deals with a comparison between different maximum power point tracking algorithms applied to wind energy conversion systems. The most commonly used algorithms are optimal torque control, power signal feedback, tip-speed ratio, and hill-climb search. The conventional hill-climb search method has an important drawback, which is the wrong directionality under rapid wind change. To solve this problem, using a hybrid hill-climb search method is proposed, which consists of combining the optimal torque control and hill-climb search methods. The proposed approach is applied to a wind energy conversion system based on a permanent magnet synchronous generator under a wind speed profile using a MATLAB®-Simulink® (The MathWorks, Natick, Massachusetts, USA) package to achieve the simulation calculations. The obtained results are then presented and compared to those given by classical algorithms to highlight the interest of the proposed approach in terms of efficiency and response speed.