Estrategias de control y sincronización para convertidores estáticos en sistemas de frecuencia y voltaje variable

Abstract

This document presents a power converter study working in a weak grid source, where the source voltage may vary significantly from its nominal condition. This kind of sources are typical of micro grid system working in islanding mode, aircraft, ship electric power systems, where the heavy loads cause a significant impact on the system variables. The impact is mainly due to the low short circuit capability on the power supply, and therefore every equipment connected to this kind of grids should be able to operate under the aforementioned conditions. As a consequence of the problems tied to weak grid sources, this work presents power converter control techniques skilled to work in a wide frequency range but keeping stability and dynamic. Indeed, linear and nonlinear techniques are employed under conditions of frequency variations, where the linear algorithms –based on resonance control- are modified in order to work in a wide frequency range, without the need of change the controller parameters, i.e. grid frequency independent of. On the other hand, nonlinear techniques –based on the predictive methods- are also included on the study, under the presence of a weak grid source. Regardless which control is used –linear or nonlinear- all of them show accurate results in a wide frequency range, also including unbalanced voltage situation. The algorithms are developed with especial emphasis in the computing time reduction in order to work even in high frequencies keeping a fixed number of samples per cycle, which allows to fix the discrete resolution of sinusoidal regardless the actual frequency. The algorithms presented with a strong mathematical base are validated by simulation and experimental results, including frequency variation, sag, swell, unbalance voltage source, among others. In addition, the designed controllers are capable to inject currents with a desired shift angle with respect to the voltage to impose