A Control Scheme for Storageless DVR Based on Characterization of Voltage Sags

Voltage sag remains a serious power-quality (PQ) problem by being the most common and causing more economic losses. The dynamic voltage restorer (DVR) is a definitive solution to address the voltage-related PQ problems. Conventional topologies operate with a dc link, which makes them bulkier and costlier; it also imposes limits on the compensation capability of the DVR. Topologies with the same functionality, operating without the dc link by utilizing a direct ac-ac converter, are preferable over the conventional ones. Since no storage device is employed, these topologies require improved information on instantaneous voltages at the point of common coupling and need flexible control schemes depending on these voltages. Therefore, a control scheme for DVR topologies with an ac-ac converter, based on the characterization of voltage sags is proposed in this paper to mitigate voltage sags with phase jump. The proposed control scheme is tested on an interphase ac-ac converter topology to validate its efficacy. Detailed simulations to support the same have been carried out in MATLAB, and the results are presented. The results of real-time testing of the scheme on a single-phase model of the topology to compensate various sag types using DSPF28335 are also presented.