Unified power flow controller is a power electronics-based device
utilised to improve transmission line capacity and control power flow
transmitted by power transmission systems. This paper presents the application
of the decoupled control strategy to control independently active and reactive
power in the event of changes in the step points of the powers. Two types of
controllers are used to handle the control strategy proposed: conventional PI
regulator and fuzzy logic PI regulator. The fuzzy logic controller must have
high performance to handle the problem of adjustment of power decoupling.
Also, a three level neutral point controller inverter is used in both series and
shunt parts of the UPFC to get multistep voltage wave and improve the power
quality.