Adaptive fuzzy control of a single-phase sinusoidal rectifier with step-up/down characteristics

This paper proposes an adaptive fuzzy logic controller for feedback output voltage control of a single-phase sinusoidal rectifier with step-up/down characteristics. These rectifiers, with a sliding mode current controller, ensure a near unity power factor operation and an input current with low harmonic content. The reference of the current controller is a sinusoidal waveform whose amplitude is modulated by the external voltage controller. Usually, the classical proportional integral (PI) controller is used for the voltage controller, however the relation between the amplitude of the input current and the output voltage is nonlinear and depends on the load. Thus, the adaptive fuzzy controller has an advantage in coping with the time varying nonlinearity of the switches in the rectifier. In order to evaluate the performance of the fuzzy controller, two suitable performance indices were developed. Based on those variables, a supervisory look-up table was constructed and used to change the parameters of a fuzzy controller to accommodate the variations of system parameters. Simulation results are presented, and the performances of the adaptive fuzzy controller are compared with the behaviour of the conventional proportional integral (PI) output voltage control, aided by an inner loop, with a sliding mode robust modulator for the input current control.