Resilience-Driven Modeling, Operation and Assessment for a Hybrid AC/DC Microgrid

Abstract

High-impact and low-probability extreme events can cause severe damage to power systems, especially for distribution systems. Microgrids (MGs) with distributed generation resources provide a viable solution for local load survivability via islanding schemes during extreme events. Recently, much research has focused on resilience-driven modeling and operations of MGs. In this paper, a resilience-driven operational model incorporating two operational modes (grid-connected and islanded) and detailed technical characteristics, such as voltage-related operational constraints, is developed for the resilience enhancement of a hybrid AC/DC MG. A detailed AC optimal power flow (OPF) algorithm is employed to model operational constraints and the power exchange between AC and DC subgrids. Preventive power importing is utilized for better preparedness before extreme events and demand response is employed to reduce load shedding during emergency mode. Existing literature on resilience assessment is reviewed and a modified multi-phase curve is proposed to fully represent the influence of limited generation resources and uncertain event duration on resilience. Extensive case studies capturing the distinction of critical loads and non-critical loads and two types of contingencies (multiple line faults and interrupted connection between AC subgrid and DC subgrid) are conducted to demonstrate the effectiveness of the proposed resilience strategy on protecting critical loads and reducing total load shedding. Particularly, a sensitivity analysis considering different event occurrence time has been simulated to capture, in a simple but rather effective way, the effect of the uncertainty surrounding event occurrence.

Keywords

• AC/DC hybrid microgrids
• resilience
• extreme events
• AC optimal power flow
• preventive power importing
• demand response