On Overvoltage Instability

In this paper, a case study is presented to demonstrate the mechanism of overvoltage long-term instability in a simple test system subject to increased penetration of converterinterfaced generation with unity power factor. It is shown that due to the underexcitation limit of a synchronous generator, a local minimum of net power transfer may exist, below which local equilibrium is lost through a limit-induced bifurcation. In this case the system is attracted to a non-viable high-voltage solution possibly leading to a blackout. Countermeasures are discussed including load tap changer blocking and reactive power absorption by the electronic converter.