A new approach for the dynamic control of unified power flow controller (UPFC)

This paper presents a new approach for the dynamic control of FACTS apparatus, such as the UPFC and the STATCON. With the new control strategy, the capabilities of the UPFC can be exploited not only for steady state power flow control but also to improve damping and transient stability assuring a good behavior during contingencies and the protection of the equipment. To achieve optimal UPFC behavior during the dynamic phenomena, the controllable system parameters are determined on-line based on the local instantaneous voltage and current measurements. The strategy is based on the theory of instantaneous powers defined in the positive, negative and zero sequence with real and imaginary components. The power flow calculation should not involve any conventional definitions of power. The Fortescus transformation will be used to conform the relation of the instantaneous active and reactive power (p,q) with the conventional active and reactive power (P-3phi,Q(3phi)). A complete model of the UPFC and the transmission system has been implemented in a digital simulator to demonstrate the versatility of the new control strategy. Interesting results have been obtained, which are presented in this paper.