A Markov Tree Model for Cascading Failure Risk Assessment in Power Grid with Uncertain Renewable Energy Generation

The increasing penetration of renewable energy generation (REG) introduces significant uncertainty into power grids, posing heightened risks for cascading failures. In this paper, a Markov tree model is proposed to assess the risk of cascading failure in power grid with uncertain REG. The model captures the diverse failure paths caused by REG uncertainty, representing the cascading failure process as a sequence of state transitions with probabilities reflecting the likelihood of state transitions. To identify critical tripping branches during cascading failure propagation, a hybrid probability-interval method is introduced. Probabilistic power flow analysis identifies branches with overload risk, while interval positional relationships rank their severity. To improve the efficiency of risk assessment, a risk-based depth-first search (R-DFS) method is proposed. This method uses estimated risk indices to prioritize high-risk failure paths while pruning low-risk paths, significantly reducing simulation time while maintaining assessment accuracy. Compared with existing models, the proposed model balances simulation efficiency and accuracy, effectively identifying high-risk failure paths under REG uncertainty. Simulation results demonstrate the impact of threshold selection on the retention of high-risk paths and simulation performance, providing insights into managing cascading failure risks in power grid with high REG penetration.