Effects of High Level of Penetration of Renewable Energy Sources on Cascading Failure of Modern Power Systems

In this paper, we incorporate the dynamical process of frequency control in modeling cascading failure and assessing the robustness of power systems with a high level of penetration of renewable energy sources. Triggered by an initial failure, a power system may be decomposed into multiple subnetworks, where the power imbalance between generation and load can be induced. Frequency control functions including primary, secondary, and emergency frequency control are employed to reduce the frequency deviation to balance the generated power and consumed power. In our simulation model, the power flow process maintains power balance in the steady-state, and a power redistribution process is triggered each time the network changes with the next failure event. The process reiterates until no overloaded component is generated. In the dynamical frequency control process, we differentiate the traditional synchronous machine-based generators from the renewable energy sources that are integrated with power electronic devices and exhibit low inertia. As power electronics integrated renewable sources do not contribute to frequency response, they can be disconnected from the grid due to unexpected frequency deviation. Applying to the IEEE 39-bus power test system, our model captures the salient frequency response process in a failure propagation chain similar to historical scenarios. The frequency deviation is found to increase with the percentage of integrated renewable energy sources, intensifying the cascading failure events. Furthermore, using the IEEE 300-bus test system, we show an increased risk of power outage as the level of penetration of renewable sources increases in the absence of an adequate protective measure.