The electric power grid evolves at an accelerated pace with a significant new mix of generation and consumption such as smart loads and power electronic-based devices. As a result, the grid is seeing more renewable energy penetration and more active consumers (Figure 1). The new uncertainties and dynamics they bring in have significant impact on the grid behaviors. Figure 2 shows the grid’s frequency responses to both emergency and normal operation situations. Especially the trending shown in Figure 2(b) is worth further studies to see if there are any correlations to the grid evolution in generation mix and consumer participation.
Of great concern is the inter-area low-frequency oscillation that usually propagate through a large region and has a system-wide impact. Such oscillations may lead to unnecessary or inadvertent tripping of generators that may be simply reacting to the oscillations originating from geographically remote sites. Such tripping of generators can lead to cascading outages, system split and load loss events. In recent years, several system-wide oscillation events have been observed across all three North American interconnections.