Application of unified power flow controller for improvement of power quality

The control scheme and characteristics of the unified power flow controller (UPFC) installed at the substation connecting the transmission system with the distribution network, are studied in relation with the power quality improvements for the loads. A simplified model of UPFC with network is introduced on the basis of the instantaneous power and reactive power function to design the control system and evaluate the effect to improve power quality in the load system. The effectiveness of UPFC is concluded for the power quality control in the substation connected to the distribution network both for the voltage dip and harmonics distortion. It would function with the same principle to suppress the interaction between the distant high power supply and the distributed small power generator in the load network.