Application of the normal forms to analyze the interactions among the multi-control channels of UPFC

One of the most important features of the unified power flow controller (UPFC) is its multiple control functions, which are implemented by multiple controllers. However, recent simulation studies have demonstrated the existence of the dynamic interactions among different controller channels of UPFC, i.e. power flow controller, AC voltage controller and DC voltage controller. This paper is concerned with the application of the normal forms to analyze the interactions among the multi-controller channels of UPFC in power systems. Moreover, a non-linear interaction index is developed to investigate the interactions among these UPFC controllers. The employed approach has been applied to two test systems: a single machine infinite bus power system (SMIB) and the New England test power system (NETPS). The simulation results validate the proposed approach.