Investigation into the dynamic interactions of multiple multifunctional unified power flow controllers

This letter investigates the dynamic interactions among different control functions of a single unified power flow controller (UPFC) and between multiple UPFCs installed in power systems. Study cases presented in this letter demonstrate that the existence of the dynamic interactions can lead to the instability of whole closed-loop control systems when all UPFC control functions are in joint operation even though each UPFC controller has been designed satisfactorily.