A Power quality problem is an occurrence manifested as a nonstandard voltage, current or frequency that results in a failure or a mis-operation of end user equipments. Utility distribution networks, sensitive industrial loads and critical commercial operations suffer from various types of outages and service interruptions which can cost significant financial losses. With the restructuring of power systems and with shifting trend towards distributed and dispersed generation, the issue of power quality is going to take newer dimensions. In developing countries like India, where the variation of power frequency and many such other determinants of power quality are themselves a serious question, it is very vital to take positive steps in this direction .The present work is to identify the prominent concerns in this area and hence the measures that can enhance the quality of the power are recommended.

This paper describes the techniques of correcting the supply voltage sag, swell and interruption in a distributed system by three power electronic based devices i.e., Dynamic Voltage Restorer, Distribution Static Compensator and Solid State Transfer Switch. A new PWM-based control scheme has been implemented to control the electronic valves in the two level VSC used in D-STATCOM and DVR. A DVR injects a voltage in series with the system voltage and a D-STATCOM injects a current into the system to correct the voltage sag, swell and interruption. The SSTS ensure continuous high quality power supply to sensitive loads by transferring the load from a faulted bus to healthy one. Comprehensive results are presented to assess the performance of each device as a potential custom power solution.