Stable Limit Cycles Induced by the Interaction of HVDC Limiters and PSSs

This paper studies the appearance of stable limit cycles in a power system model with a HVDC link near a synchronous generator unit. The HVDC system studied in this paper is a simplified version of the transmission system between the 50 Hz sector of Itaipu power plant and the Brazilian interconnected system. We show that the limit cycle coexists with a stable equilibrium condition and the system reaches the oscillation condition after a large perturbation. We also show that the limit cycle appears as a consequence of the interaction between the HVDC and PSS controllers. More precisely, the limit cycle is induced by the action of the Rectifier Alpha Minimum Limiter (RAML) of the HVDC controller interacting with the action of the PSS controller. This oscillating condition is undesired and understanding its cause is the main aim of this paper.