Dynamic Model of a Virtual Air Gap Reactor

Abstract

Variable reactors have been a vital component of power networks for decades, where they have been used as fault-current limiting devices or for reactive power compensation. Traditionally, modifying the inductance of predominantly mechanically operated variable reactors requires seconds to minutes. In contrast, virtual air gap (VAG) reactors can change the inductance within milliseconds, potentially improving power system stability. Existing dynamic models of VAG reactors cannot capture the entire system dynamics, limiting their applicability for simulations in the time-domain. This research presents two dynamic VAG reactor models, one with and one without core losses. The models capture all significant system dynamics using electromagnetic principles and VAG reactor flux linkage behavior. The proposed models were experimentally validated using a small VAG reactor. Over a broad operating range, both models accurately reproduce the dynamic behavior, transient response, and dominant harmonics of the small VAG reactor. Consequently, the models may be used for a variety of applications, such as timedomain simulations, harmonic analysis, and the development of suitable controllers for VAG reactors. In addition, engineers may use the core loss omitting model as a VAG reactor design tool, as the actual reactor is not required for modeling.Index Terms-Dynamic model, finite element method (FEM), variable reactor, virtual air gap (VAG).