Voltage Quality Enhancement and Harmonic Reduction using DVR

The quality of delivered power at the user terminals is one of major areas of concern in the modern power systems. It has now days become very important and essential, due to the drastic increase in the use of the sophisticated electrical devices, whose performance parameters are highly dependent and sensitive to the quality of power being delivered. Poor quality of power means nonstandard voltage, current and frequency and due to this many electrical equipment may fail in their desired operation. The major problem is linked to quality of supplied voltage which often deteriorates due to common sag in voltage amplitude and also swells in voltage. The problem of sag in voltage can be solved by use of multiple FACTS devices. Dynamic voltage restorer (DVR) is one of the extremely powerful and reliable FACTS devices for improving the profile of voltage in existing distribution systems. Different types of VSC are used in DVR to inject voltage during voltage sag by using injection transformer and different controllers. This paper provides a comprehensive survey of the researches done in the field of DVR till date. The comparative study has been done among different controllers which are used in DVR systems. This review paper also shows the performance of DVR and comparison of DVR with other FACTS devices. It has been established that DVR has got superior capability to improve the quality of voltage being delivered at the user premises as compared to other FACTS devices and also that it helps in improving the distortion in the supplied voltage.