Utilising parametric sensitivity of unified power flow controller during voltage emergency situations

The main purpose of this paper is to investigate regulating characteristics of an UPFC and possible benefits during voltage emergency situation by using all three UPFC´s control parameters simultaneously. The control system of the UPFC´s injection model is developed and its contributions to avoiding a voltage collapse are explored on a multimachine test system. The analysis is carried out from dynamic and static aspects. During dynamic time-domain simulations, the extended Jacobian and state matrices are evaluated utilising a linearised differential-algebraic system model. With the UPFC being embedded in the system using static approach, the analysis is concentrated on the sensitivities of the UPFC´s set of control parameters. The sensitivities concern minimisation of total power loss or maximisation of critical singular value of the matrices. In addition to voltage support capability, usually achieved using two of UPFC´s parameters, possible ways of utilisation of the third parameter are shown through sensitivity analysis.