An Improved Direct AC-AC Converter for Voltage Sag Mitigation

Dynamic voltage restorer (DVR) is a definitive solution toward compensation of voltage sag with phase jump. Conventional DVR topologies, however, have dc links and two-stage power conversions. This increases its size, cost, and associated losses. Therefore, topologies without the dc link, mitigating sag by utilizing direct ac-ac converters, are preferable over the conventional ones. As no storage device is employed, compensation by these topologies is limited only by the voltages at the point of common coupling that is feeding the converters. In this paper, a direct-ac-ac-converter-based topology fed with line voltages is proposed. The arrangement provides increased range of compensation in terms of magnitude and phase angle correction. Detailed simulations have been carried out in MATLAB to compare the capability of the proposed topology with other similar topologies. Experimental results are presented to validate the capability of the topology to compensate various sags.