An adaptive fuzzy logic controller for three-phase PWM boost rectifiers: design and evaluation under transient conditions

Fuzzy logic controllers (FC) have been implemented and studied on various types of static power converters. However, their improvement in converters´ performance is not clear compared to classical control theory controllers. This is especially true in systems where precise models exist, such as the PWM boost rectifier (PWM-BR). Hence, another use of FC has ensued, which is to tune and adapt controllers synthesized by classical control theory. This paper takes advantage of this trend and proposes an 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, gains, and by using an inner AFC to adapt the output normalizing gain. Thus, the AFC is capable of reducing the PWM-BR overvoltage and settling time by 65% and 80% compared to a conventional FC. Consequently improving the switches´ voltage utilization factor by 9.1%. The converter´s fast response is attained by using a dynamic space vectors modulation that 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 a detailed and thorough evaluation under transient conditions. All these show the feasibility of the proposed control scheme