Control Structure with Fuzzy Supervision of PI Parameters in a Multilevel Converter Application

This paper presents a novel control structure based on mixed techniques (fuzzy and PI's) for the control of a neutral-point-clamped converter. This structure implies three PI regulators with an adaptative fuzzy self-tuning regulator. The constants of the proportional and integral actuators (k_p and k_i, respectively) are simultaneously adjusted for the voltage and current control loops. This method achieves optimal performance of the system under load steps regarding dc-link voltage regulation and ac currents. A theoretical stability analysis is also performed. The system is tested by simulation and experiment under rectifier operation mode