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International audience; The control of inverters has degrees of freedom that open the way to improve the output harmonic spectrum. Numerous works dealing with this objective have been proposed in the literature, particularly within the definition of switching angles. Among them, the well-known PWM techniques such as Quarter Wave Symmetry (QWS), Half Wave Symmetry (HWS), and Full Wave Symmetry (FWS) are based on Optimal Pulse Patterns (OPP) computation using symmetries angles constraints. In this paper to improve the harmonic quality, the symmetry angles constraints are not considered leading to a new OPP method: Phases Symmetry Relaxation (PSR). To highlight the interest in the proposed PSR method, an evaluation in terms of Weighted Total Harmonic Distortion (WTHD) is performed. Simulation and experimental tests are conducted in comparison with the well known FWS, highlighting the interest in the proposed PSR strategy.

In this paper, a new optimization problem is proposed for improvement of PWM control of an inverter that supplies a generic RLE load. Two objectives functions are studied separately: Weighted Total Harmonic Distortion (WTHD) of load voltages and total losses. The gap contribution is related to optimize the zero sequence component waveform by defining special decision variables. By doing so, the proposed PWM strategy allows to improve the WTHD and efficiency of converters by keeping a classical PWM implementation scheme. Moreover this approach has the same way of thinking than the two main different classes of PWM strategies that are Space-Vector-based PWM (SVM) methods and classic carrier-based PWM methods (CBPWM). It is well known that there is an equivalence between SVM and CBPWM through the zero sequence component injection. So, optimized zero sequences are proposed for the two objectives functions considered, and the simulation results show a significant improvement compared to classical CBPWM strategies. Moreover the proposed strategy allows an implementation on existing hardware by modifying only the modulation component software.

International audience

Control systems constitute a main part of energy efficiency studies on electric motors, where efficiency varies according to the operating point and the mechanical load of the motor. The purpose of this paper is to present an optimization technique to the classic scalar control of the squirrel-cage induction motor (IM), aiming to improve its energy efficiency while taking into consideration the effect of the core losses in the motor. A table defining the best efficiency flux reference is computed, based on an improved model of the IM including core losses. It gives the necessary stator flux reference for the scalar control system according to the operating point, in order to get the best efficiency and the lowest possible losses. Simulation results validate the proposed optimized scalar control and show the improved energy efficiency as well as a reduction in power losses.

International audience; An elegant way to exploit control redundancies available in multilevel converters is through the formulation of a constrained optimization problem. An interesting connection can be made with the so-called control allocation problems defined in over-actuated constrained systems. Redundancies and constraints are taken into account to achieve the best performance. In this paper, we introduce the first result of an investigation of control allocation methods for multilevel conversion. The method is dedicated to the flying-capacitor inverter with focus on the active balancing of capacitor voltages to ensure admissible blocking voltages for the switches. A linear program is formulated and solved by using the well-established simplex algorithm. Fast variations of the DC-bus voltage were applied in simulations. Disturbances are well rejected thanks to a highly reactive balancing, and a safe switching operation is ensured.; Une manière élégante d'exploiter efficacement les redondances de commande disponibles pour les convertisseurs statiques multi-niveaux est de formuler des problèmes d'optimisation contraints. Ces problèmes sont similaires aux problèmes dits d'allocation de commandes rencontrés pour les systèmes mécaniques sur-actionnés. Les redondances et les contraintes sont prises en compte pour obtenir les meilleures performances. Dans ce papier, nous présentons un des premiers résultats de l'étude de méthodes de commande par allocation pour la conversion statique multi-niveaux. Nous proposons une nouvelle méthode pour l'onduleur à condensateurs flottants avec une attention particulière portée sur l'équilibrage actif des tensions des condensateurs afin de maintenir des tensions de commutation admissibles pour les interrupteurs. Nous formulons un problème d'optimisation linéaire dont la résolution repose sur le célèbre algorithme du simplexe. En simulation, nous faisons subir de fortes variations de la tension continue d'entrée. Grâce à notre méthode, ces perturbations sont rapidement rejetées, garantissant une meilleure sécurité des interrupteurs de puissance et une bande passante élevée.