Stabilising influence of a synchronous condenser in low inertia networks

Abstract

Power systems have to be reinforced to accommodate a high penetration of renewable energy sources. Recent research shows that the stability margin of the grid degrades with the penetration of grid-tied photovoltaic generators into the grid. In the model presented in the study, the critical level of photovoltaic penetration is associated with a Hopf bifurcation in the field dynamics of the synchronous generators which severely limits the operating domain of the grid. It is shown that the judicious introduction of synchronous condensers in the modelled grid delays this dynamic instability. A small-signal analysis is performed for a system where the reactive power and inertial response is supplemented using a synchronous condenser. The study shows that the modified network tolerates much higher participation of photovoltaic generation in the grid. It is shown that the modified network retains the classical power system control approach and also does not demand a change in the way the photovoltaic generation is injected, thereby making it a natural implementation. The synchronous condenser augments the operational domain of the system significantly, nearly eliminating the need for renewable energy curtailment. A case-study approach is used to present results on improvements in damping ratio, feasibility domain and transient stability.