A UNIFIED POWER QUALITY CONDITIONER WITH VOLTAGE SAG/SWELL COMPENSATION CAPABILITY

Traditionally, Unified Power Quality Conditioners (UPQCs) are designed for simultaneous compensation of voltage and current harmonics and imbalances. Moreover, the shunt active filter of the UPQC behaves as a controlled current source to compensate the load current, whereas the series active filter behaves as a controlled voltage source to compensate the supply voltage. Here, a dual configuration of UPQC, denominated as the iUPQC, is presented. In contrast to the conventional UPQC, the shunt active filter of the iUPQC behaves as an ideal ac voltage source and the series one as an ideal ac current source. One negative aspect in the conventional approach of UPQC is the voltage and current PWM controls of the power converters. The PWM controls must deal with nonsinusoidal compensating voltage and current references, with aleatory frequency spectra. In this case, it is impossible to theoretically unsure zero steady-state error in all frequencies components. Contrarily, the iUPQC has a fundamental positive-sequence current reference for the series active filter and a fundamental positive-sequence voltage reference for the shunt active filter. Beside all those compensation characteristics of the UPQC, the iUPQC can also keep the load voltage constant, at the nominal value. In other words, it has voltage sag/swell compensation capability, with fast response, comparable to that of a Dynamic Voltage Restorer (DVR). Simulation and experimental results are presented to validate the proposed iUPQC controller.