In this paper, a new analytical method for the modeling of the star connected induction motors operating under unbalanced power supply is developed using coupled circuits theory. This method takes into account the increase of the common point voltage during unbalanced supply conditions. The equations, which describe the state model as well as the calculation of machine inductances, are presented. The calculation of inductances is based on the magnetomotive force distribution through the machine air-gap. The advantages of the proposed method are multiple. The space and time harmonics can be taken into account. It can also be extended for the analysis of faulty induction machines. Magnetic saturation, skin effect, skewed rotor, and slotting effects can be integrated in the calculation of the machine inductances by introducing some techniques to the basic coupled circuit theory. This method reduces strongly the time simulation because of the simple numerical representation of the inductances and their derivatives. The obtained results show good agreement with other results, which have been obtained using finite elements method and symmetrical components approach. The particularity of this work is that it takes in consideration the increase of the common point voltage during unbalanced supply conditions. Simulation results show the consistency and the applicability of the proposed method for the modeling of induction motors operating under unbalanced power system.
The paper describes a vector fault tolerant control of squirrel cage induction machines (IM). The field oriented control (FOC) was combined to robust sliding mode control (SMC). This last is a technique to adjust feedback by previously defining a surface. The controlled state variables will be forced to move on this surface, then the behavior of the machine slides to the desired equilibrium point. We have taken the stator interturn fault, which is the most frequently encountered in practice. An analytical method for the modelling of this fault has been presented including space harmonics effect. This method is based on the calculation of the magnetic field distribution through the machine air-gap. The obtained model is less complicated to be implemented for condition monitoring or to validate fault tolerant control algorithms. Simulation results show, on the one hand that the proposed control scheme provides highperformance dynamic characteristics, and on the other hand the applicability and the tolerance of this control.
This paper describes a Fault Tolerant Control (FTC) of a doubly-fed induction generator (DFIG) based wind turbine model suitable for the simulation of this generator in the mode faulty mode. The dynamic model of a DFIG with stator inter-turn short circuit fault is proposed. A model (abc) is developed, which can represent both the healthy and faulty conditions. The DFIG is directly connected to the grid whereas the rotor winding is fed by back-to-back PWM converters .the Control schemes for active and reactive power regulation are designed firstly. Under different wind speed, maximum power point tracing (MPPT) control is implemented to ensure the optimum active power output. The numerical simulation developed in Matlab/Simulink studies the effects of stator inter-turn short-circuit in the DFIG. Afterward, the application of Approach technique of Adaptive Obs
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