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Jordi Espina i Masramon

Ph.D. Thesis title:
Estudio e implementación de nuevas técnicas de modulación para la reducción de perturbaciones EMI en convertidores matriciales

Author:
Jordi Espina i Masramon

Director:
Antoni Arias, Josep Balcells, Carlos Ortega

Reading date:
7 de novembre de 2012 

Abstract:
The energy processing using power converters has taken a remarkable importance in the last decade, and in the future it might become one of the engineering fields with greater projection.

The continuous evolution in the field of power electronics has made possible to manufacture more compact switched converters, capable of managing higher voltage and currents levels switching at higher frequency. These improvements, however, lead to the generation of electromagnetic perturbations (EMI) which fail the electromagnetic regulations.

On the other hand, the converter design using new layout topologies and a regulation law that is becoming more restrictive about EMI emissions makes essential to develop new tools capable to analyze the effects of the EMI generated.

One of the emerging power converters which is currently acquiring special relevance is the matrix converter (MC). The rise of interest on this topology in recent years has been determined by different aspects, such as direct AC/AC conversion, its high power density and the absence of large reactive components for energy storage.
The work presented in this document tries to cover the study and the reduction of EMI generated by the MC.

This Phd thesis has divided in two research lines: The study of the EMI produced by MC and the prevention of the adverse effects produced by EMI.

The first research line has mainly focused on the study of EMI generated by MC of direct topology. In this study, a model to predict the conducted EMI has been developed. One of the main objectives of this model is to deliver good approximation results in short time. The strategy used has been the conducted perturbation calculation using the classification of the EMI as common mode (CM) and differential mode (DM). The method used is based on extraction of the equivalent impedance circuit. This equivalent circuit provides a true representation of the generation and propagation of EMI without the need of complex mathematical methods.

The second research line has mainly focused on the reduction of electric discharges which is produced inside of the motor bearings, which are the main cause of motor life time reduction. These electrical discharges are produced by the common mode voltage (CMV) levels and its fast time transitions (dv/dt). In order to reduce those levels, a new modulation based on the traditional Space Vector modulation (SVM) has been developed replacing the zero vectors, normally used, for the rotating ones. This vector exchange has shown a significant reduction of the CMV amplitude, and therefore the probability of electrical discharge appearing inside the motor drops considerably. Furthermore, the study analyzes the use of the active vectors with smaller amplitude to improve the modulation when small modulation index is used.