Impact of Reduced Synchronous Machine Capacity on Damping and Phase of Inter-Area Oscillations

This paper investigates the effect of reduced synchronous machine capacity in the system on inter-area oscillations considering its effect on the phase of oscillation. As a first step the process is approached solely from the perspective of inertia without affecting any other system parameter considering various scenarios in terms of location and size of the reduction. It is shown that the distribution of inertia within the system has a significant impact on the damping of the inter-area mode in particular considering the sensitivity to the inter-area power exchange. The effect on the damping is analyzed by examining the effect on the phase of oscillations in the different groups which reveals that the reduction of inertia typically advances the phase of oscillation of the reduced group towards the group with higher inertia. In the second step additional effects of the reduction are taken into account and it is shown that, apart from the oscillation phase, the power flow sensitivity plays an important role when trying to assess the damping contributions of machines as the sensitivity of the damping in respect to the power flow is greatly increased under these circumstances.