Single-Phase Universal Active Power Filter Based on Four-Leg AC–DC–AC Converters

This paper presents two universal active power filters (UAPFs) configurations using single-phase four-leg ac-dc-ac converters. The proposed topologies are used for disturbance compensation in the power supply, such as voltages sags/swells, and to compensate harmonic distortions in the current. The operation of the proposed configurations is compared with the conventional single-phase four-leg UAPF. The harmonic distortions, semiconductor losses, and average switching frequency are used as comparison parameters. Compared to the conventional configuration, the proposed topologies use a transformer with lower power, provide lower average switching, and reduced current total harmonic distortion (THD) and voltage weighted THD. The pulsewidth modulation (PWM) strategy was designed based on a space vector modulation technique, and a control system for the grid current and dc-link bus voltage regulation was also developed. Simulation and experimental results are presented showing the efficiency of the PWM and control strategies and validating the proposed topologies.