چكيده به لاتين
Two-stage converters are among the converters in which the stage of changing the voltage level is separated from the stage of changing the waveform of the mentioned quantity, so that one stage performs the operation of changing the voltage level and the other stage performs the operation of changing the shape of the voltage waveform. One type of these converters is three-phase dual active bridge-based single-phase two-stage converter. The above-mentioned converter consists of a three-phase dual active bridge converter in the DC/DC stage and a single-phase full bridge inverter in the DC/AC stage. Single-phase converters, in general, due to the change of waveform from DC to AC and vice versa, always have second harmonic current on the DC side, which reduces the power quality of the converter on that side. In order to solve this problem, various solutions have been proposed so far, however, in the literature, the reduction of the second harmonic current in the presence of uncertainties caused by the converter has been less discussed. In the research carried out in this thesis, by using H∞ robust control theory, a controller is presented that reduces the second harmonic current on the battery side in the presence of the uncertainty caused by the capacitance of the DC link, which previously has not been investigated in any research. In the same way, for further development, the uncertainty caused by load changes at the output of the converter has also been applied to the model, so that the controller, in addition to increasing the system robustness against the uncertainty caused by the capacitance of the DC link, also increases the system robustness against the uncertainty caused by the load. In this thesis, in the initial chapters, the previous researches in the field of second harmonic current reduction in two-stage converters and then the working principles of the three-phase dual active bridge-based single-phase two-stage converter have been discussed. Then, in the following chapters, the H∞ robust controller has been developed for the conditions in which the three-phase dual active bridge-based single-phase two-stage converter suffers from uncertainty in the area of DC link capacitance. In this method, the controller is applied to the three-phase dual active bridge converter, so first the generalized average model of the dual active bridge converter is obtained, then the small signal model of the converter is developed and the necessary uncertainties are modeled. Finally, H∞ robust control has been applied to the final model obtained. In the end, the performance of the proposed controller along with the mentioned two-stage converter is simulated in the MATLAB/Simulink environment and the results are compared with the previously developed methods.
