  With increasing installation of wind and solar generation, conventional
synchronous generators in power systems are gradually displaced resulting in a
significant reduction in system inertia. Maintaining system frequency within
acceptable ranges becomes more critical for the stability of a power system. In
this paper, we first study the impact of inter-area oscillations on the system
rate-of-change-of-frequency (RoCoF) security; then, the limitations on
locational RoCoFs accounting for G-1 contingency stability are derived. By
enforcing these frequency related constraints, a location based RoCoF
constrained security constrained unit commitment (LRC-SCUC) model is proposed.
Furthermore, an effective piecewise linearization (PWL) technique is employed
to formulate a RoCoF linearization problem and linearize the nonlinear function
representing the location based RoCoF constraints in SCUC. Simulation results
reveal that the inclusion of inertia-related constraints can substantially
improve the system stability at the cost of higher operation cost. The results
also show that deploying virtual inertia techniques not only reduces the total
cost, but also improves the system market efficiency.
