Tese
Contribuições ao projeto de controladores robustos a variações paramétricas aplicados a conversores conectados à rede
Fecha
2021-05-12Autor
Osorio, Caio Ruviaro Dantas
Institución
Resumen
This Ph.D. thesis provides contributions to the design of robust current controllers
for grid-connected converters, including: i) a time-varying model to deal with the
magnetic soft saturation in the filter inductors and the possible variation of the grid impedance;
ii) systematic procedures to design the gains of state feedback controllers robust
against magnetic soft saturation, obtained by means of linear matrix inequalities; iii) an
optimization of the performance of controllers by means of pole location robust against
uncertainties in the grid impedance, taking into account a trade-off between transient performance
and control effort. For the design of the robust controllers, the plant is modeled
in a polytopic way, in the discrete time domain, including the delay due to the digital
implementation of the controller. An arbitrary number of resonant controllers are also
included to ensure tracking of sinusoidal references and rejection of harmonic disturbances
from the grid voltages, for instance. In the sequence, two strategies based on linear
matrix inequalities (robust pole location and H2 guaranteed cost) are used to obtain robust
state feedback gains. These gains are implemented in practice in a digital signal
processor, leading to real-time simulation results based on hardware-in-the-loop and also
on experimental results based on a prototype which exhibit high quality transient and
steady state performances. The currents injected into the grid meet the requirements of
the IEEE 1547 Standard, in the case of magnetic soft saturation of the filter inductors,
and also in the case of uncertain and possibly time-varying grid impedances.