Analysis of Series Compensation and DC-Link Voltage Controls of a Transformerless Self-Charging Dynamic Voltage Restorer

This paper describes a transformerless self-charging dynamic voltage restorer (DVR) series compensation device used to mitigate voltage sags. A detailed analysis on the control of the restorer for voltage sag mitigation and dc-link voltage regulation are presented. A nonlinear element is shown to exist in the regulator, the activation of which can adversely affect its stability. Active cancellation for this element is recommended. Simulation and experimental results are presented for a 1-kVA prototype to validate the analysis as well as demonstrate the DVR's performance under both voltage restoration and self-charging operating conditions.