A three-phase four-leg DVR using three dimensional space vector modulation

In this paper a three-phase four-wire Dynamic Voltage Restorer (DVR) is proposed to inject required compensating series voltage to the electric power system in such a way that continuous sinusoidal voltage is seen at load side ever at heavy fault occurrences at utility side. The proposed DVR is composed of a three-phase four-leg inverter and a three-phase high frequency harmonic filter that are connected to the utility by three single-phase power transformers. Three dimensional space vector modulation (3DSVM) is applied to the proposed DVR to generate switching pulses for power switches. Fourth added wire enables the DVR to compensate unbalance voltage sag and swell that are custom power quality problems in electrical utility. The performance of the structure and applied switching scheme under both balanced and unbalanced sag and swell are validated by simulations in PSCAD-EMTDC software.