Power quality improvement using a power electronic transformer based DVR

In this paper a three-phase four-wire Dynamic Voltage Restorer (DVR) with bi-directional power electronic transformer structure 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 structure is composed of a three-phase four-leg inverter, three single-phase high frequency transformers, three cycloconverters and high frequency harmonic filter that are connected to the utility. Three dimensional space vector modulation (3DSVM) method is used for pulse generation. Fourth added wire enables the DVR to compensate unbalance voltage disturbance that are custom power quality problems in electrical utility. The performance of the structure and applied switching scheme are verified under both balanced and unbalanced disturbances via simulation study in PSCAD/EMTDC software.