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Contribution à l'étude des convertisseurs multi-niveaux moyenne tension : réduction d'harmoniques BF et linéarisation de leur tension

Abstract : This thesis deals with multi-level power converters for electrical drive applications, used in particular in the field of Oil & Gas and marine propulsion, or for network applications such as reactive energy compensation. The objective is to optimize the controls of these converters in order to reduce the harmonic content of the output voltage and therefore of the current, a very important parameter for the sizing of both the output filters and the electrical machines connected to them. In the first part of this thesis, the different multi-level topologies are analyzed and three selected five-level topologies are compared in terms of the number of semiconductor components, losses, harmonic content and the energy stored in the passive elements. Depending on the application type, one of them is preferred over the others. In the second part, we proposed a method for reducing low frequency harmonics of the multilevel converter output voltage, which consists in controlling the phase of the PWM carriers for integer ratios of the switching frequency and the fundamental frequency. The minimization of low-frequency harmonics of the converter output voltage by optimizing the carrier phase is first validated by numerical simulations and then practically implemented and validated using a real time simulator RT-Lab. To overcome the problems of non-linearities introduced by the classical clamping methods of the reference voltages of multi-level converters, limiting the amplitude of the maximum achievable output voltage, we propose a new linearization method in the last part of this thesis. This involves adding an optimized zero-sequence component to the reference voltages of multi-level converters to linearize the fundamental of their output voltages, which makes it possible to increase their amplitude to its maximum achievable value. This method is tested by numerical simulation in the control of a complete electric drive system allowing it to operate over the entire speed range, without affecting the voltage balancing of the main DC bus capacitors.
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Hamza El Jihad. Contribution à l'étude des convertisseurs multi-niveaux moyenne tension : réduction d'harmoniques BF et linéarisation de leur tension. Energie électrique. Université de Lorraine, 2019. Français. ⟨NNT : 2019LORR0175⟩. ⟨tel-02517597⟩



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