Anotace:
In this paper, a comparative study between nonlinear sliding mode controller (SMC) and standard PI controller for stabilizing bridgeless AC/DC converter under uncertain parameters is presented. This type of converters is widely used in harvesting low energy systems as in wind turbine, piezoelectric transducers and heat exchange transducers. Designing robust controllers to enhance the efficiency and accuracy of these converters has become a promising track in control engineering field. The traditional bridge rectifier is widely used in the majority types of AC/DC conventional converters to gain the rectified DC voltage from the low AC input voltage source. However, these traditional converters are not effective for the low output voltage of renewable sources due to the voltage drops across rectifier’s diodes. The proposed SMC-PI controller is used to enhance the stability and the response of these converters under uncertain parameters comparing with the standard PI controller. The proposed approach consists of both Boost and Buck-Boost converters with two controllers in order to maximize the useful output energy from the source. The graphical method has been used to obtain the limitation of the coefficients of the standard PI controller. A parameter space approach is used to find all robust stabilization PI coefficients and the stability regions. A comparative study using simulations in MATLAB is presented to ensure the effectiveness and robustness of the proposed SMC-PI controller under some external disturbances.