Quantifying and Mitigating Cascading Impacts in HVdc-Interconnected Power Grids

With the increasing penetration of HVDC technologies in today's power systems, especially for interconnecting neighboring grids—including those that are renewable-rich—there is a need to explore their contribution to system reliability and resilience in the context of cascading failures. This paper introduces a holistic framework for quantifying and mitigating cascading risks in HVDC-interconnected systems. It considers extreme events in addition to credible or expected events that threaten the resilience of interconnected systems, as evidenced by recent cascading blackouts with cross-border propagation impacts in Europe and worldwide. To achieve this, advanced dynamic cascading failure modelling is leveraged to simulate and quantify the cascading effects in HVDC-interconnected systems, particularly focusing on frequency stability and large-scale disturbances. This sheds light on the influence of HVDC on mitigating the propagation of non-local cascading events with cross-border impacts in interconnected systems, attributed to its “firewall” property. It also seamlessly integrates the dynamic cascading simulator with operational strategies, specifically controlled islanding, to further mitigate both local and non-local cascading impacts, especially addressing cross-border propagation, in interconnected systems. The simulation results on HVDC-interconnected test systems demonstrate the efficiency of the proposed work in significantly reducing cascade metrics, including Expected Demand-Not-Served (EDNS) and, notably, Conditional Value-at-Risk (CVaR) which captures tail risk events.