QFT robust controller for Buck-Boost DC-DC converters in solar PV applications

This paper shows the design of a controller using Quantitative Feedback Theory (QFT) and a modified Smith predictor. The controller is applied to a Buck-Boost DC-DC converter in continuous conduction mode that regulates the voltage supplied by a PV Generator, considering variations of load, voltage fluctuations of the solar panel, and parameters of the converter such as irradiation and temperature. Control strategies are designed using model-based techniques, using the Matlab® Toolbox Simscape for physical systems modeling. The QFT control scheme has been modified from a Smith Predictor structure for non-minimum phase systems, and the PID controller is designed using a two-degree-of-freedom structure. A comparative analysis of performance indices of the temporal response and the error are shown. The results obtained in simulation show the QFT controller has a better dynamic response and robustness, with a lower effort of the control signal when compared with a two-degree-of-freedom PID controller.