Amélioration de la sûreté de fonctionnement d’un actionneur électrique à réluctance variable

Abstract : The work proposed here focuses on the improvement of the energy efficiency and the safety of the Switched Reluctance Machine (SRM). First, the control of the SRM in motor and generator modes is presented. In motor mode, the speed and the torque are regulated, while in generator mode, the objective is to keep constant the DC bus voltage. An iterative optimization algorithm is proposed formaximizing the global efficiency. The analysis of the electromechanical energy conversion has shown that there is an optimal combination of the control variables - turn on angle (Ψ), conduction angle (Θp) and reference current (Iref) – to maximize the efficiency. The strategy is evaluated using intensive numerical simulations and experimental validation. Thanks to the optimization, the global efficiency reaches 70% almost from half the nominal speed to the maximum speed. Then, the Switched Reluctance Generator (SRG) is used as an AC generator for a Wind Energy Conversion (WEC) application. The produced DC power is converted into AC power by means of voltage inverter and delivered to the AC grid. The first issue of the WEC control is to maintain constant the output DC voltage despite the wind speed variations and the load uncertainty. The second issue is to control the quality of the current. In single-phase AC network, three controllers are tested to regulate the AC current (PI controller, Resonant controller, Proportional-Resonant controller). In three-phase AC network, a VQ control in Park’s frame is adopted: The DC bus voltage is controlled through the direct current and the reactive power injected into the grid is controlled through the quadrature current. Simulation results show that quasi-sinusoidal currents with a harmonic distortion rate less than 1% are obtained in both cases. Finally, we address the problem of sensorless control. In fact, the control of the SRM requires that the rotor position is known. A mechanical encoder is used generally to measure the position. The elimination of this position sensor would reduce the cost and packaging requirements of the drive. Three methods to estimate the rotor position are presented. The first one named inductance-method is an active as it is based on the pulse injection technique. The second one named flux-method is a passive one as it used the current measurement. The third one is based on the state observers for the flux, position, and velocity and load torque estimation. The simulations results have shown that the inductance-based method is efficient in low speed region and the flux-based one is more efficient in high-speed region. It is also shown that, observers are exponentially convergent even when a simple analytical modelling, that neglects saturation effect, is used to design the observer.
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Abdoulaye Sarr. Amélioration de la sûreté de fonctionnement d’un actionneur électrique à réluctance variable. Energie électrique. Université Paris-Saclay, 2018. Français. ⟨NNT : 2018SACLS533⟩. ⟨tel-02145225v2⟩

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