A simple adaptive fuzzy logic controller for three-phase PWM boost rectifiers

Fuzzy logic controllers (FC) have been implemented and studied on various types of static power converters. However, their improvement of converters´ performance is not clear compared to classical control theory controllers. This is especially true in systems where precise models exist, such as in the PWM boost rectifier (PWM-BR). Another use of FC has been to tune and adapt controllers synthesized by classical control theory, where they have achieved good results. This paper takes advantage of these trends and proposes a simple adaptive fuzzy controller (AFC) which offers an improved dynamic response when compared to conventional FC. The AFC adaptive nature is achieved by modifying its normalizing factors and gains, and by using an inner loop which adapts the output normalizing gain. Thus, the AFC is capable of reducing the PWM-BR overvoltage and settling time by 75% and 90% compared to a conventional FC. Consequently improving the switches´ voltage utilization factor by 11.3%. The converter´s fast response is attained by using a space vectors modulation which also improves the converter´s voltage utilization by presenting a unity AC-DC gain. The paper presents a complete analysis and design procedure of the AFC and PWM-BR system, together with an extensive evaluation under transient conditions. All these show the feasibility of the proposed control scheme