A soft-switching single-phase three-arm unified power quality conditioner

This paper presents an FPGA-based control circuit for controlling the soft-switching single-phase three-arm unified power quality conditioner (UPQC). The proposed soft-switching UPQC employs three-arm topology and uses simple resonant units. All main switches of the high-frequency arm operate at zero-voltage-switching (ZVS) turn on, while the auxiliary switches operate at zero-current-switching (ZCS) turn off. Moreover, operating at a constant switching frequency, a unipolar PWM scheme is used to reduce the input current and the output voltage harmonics. The proposed UPQC contains a series-active and a shunt-active filter. The series-active filter can compensate for the ac source voltage fluctuation. Also, it can be used to regulate the under-voltage and voltage sag situations. On the other hand, the shunt-active filter can compensate for the current harmonic and improve the power factor. Finally, some simulation results are presented for demonstration.