Modeling and analysis of multilevel inverter based dynamic voltage restorer with dc-dc converter

Voltage, current, frequency deviations and waveform distortions that causes equipment failure, economical loss and several negative effects are known as power quality problems. Among the power quality problems, voltage sags and swells are the most significant disturbances. The dynamic voltage restorer (DVR) is the most effective and economical custom power device applied to protect sensitive loads from voltage sags and swells. In this thesis, dynamic voltage restorer with dc-dc converter is modeled in PSCAD/EMTDC. DC-DC converter is used to maintain and control the dc voltage of the inverter during voltage sag. The developed topology permits to use in medium power systems. Multilevel inverter is used to allow high power-handling than the two-level inverter. EPLL, SRF and SOGI-PLL is used to detect and extract the voltage sag and swell. SOGI-PLL is a new method to extract voltage magnitude and phase angle simultaneously. The comparison results of EPLL, SRF and SOGI-PLL are presented in thesis. The performance of DVR is evaluated through simulations for compensation of balanced and unbalanced voltage sags. The main purpose of this thesis is analyzing and modeling of DVR, which protects a 1-MVA nonlinear load. The performance results of the proposed topology are presented with different cases by PSCAD/EMTDC program.