Abstract: This paper gives emphasis on comparative study of compensating devices used for power quality improvement. In distribution system, power quality problem has become a big issue in recent years. Lack of power quality affects consumers in many ways such as transients, short duration voltage variation, long duration voltage variation, voltage imbalance, waveform distortion etc.The power quality improvement is mandatory for the newer sensitive to power quality disturbances especially with interruptions, harmonics and voltage sags. These problems are offered flexible solutions by custom power. The custom power devices can be divided into two categories network reconfiguring type and compensating type. SVC, STATCOM, IPC, DVR, UPFC, TCSC, TCPST and DSTATCOM are the different types of FACT devices which can be used to solve these types of problems.

Keywords: Power quality improvement, Harmonics and Interruption, Custom power, FACT devices.