Low frequency oscillation analysis in parallel AC/DC system by a novel dynamic model

A novel approach is presented for efficiently modeling a power system, which includes parallel-connected HVAC, and HVDC transmission systems. The proposed model has been derived for a system in which an AC generator is connected to an infinite bus system through a parallel AC tie line and a HVDC link. In addition to state-space representation, a block diagram representation has been formed to analyze system stability. In this new block diagram representation, the dynamic characteristics of the system are expressed in terms of a newly developed H constant. The development of the block diagram and associated H constants are explained. The new model is evaluated using PSCAD/RTDS real time digital simulation. Based on this new model, the low frequency oscillation phenomenon in parallel AC/DC system is studied and the results are shown.