A Two-Level Simulation-Assisted Sequential Distribution System Restoration Model With Frequency Dynamics Constraints

TL;DR

This paper introduces a two-level simulation-assisted restoration model for unbalanced distribution systems with inverter-based microgrids, ensuring load recovery while maintaining frequency stability during system restoration after extreme events.

Contribution

It develops a novel MILP-based optimization model that integrates frequency dynamics constraints with transient simulation, addressing low-inertia issues caused by inverter-dominated microgrids.

Findings

Improved frequency dynamic performance during restoration.

Validated effectiveness on a modified IEEE 123-bus system.

Enhanced load restoration with frequency stability guarantees.

Abstract

This paper proposes a service restoration model for unbalanced distribution systems and inverter-dominated microgrids (MGs), in which frequency dynamics constraints are developed to optimize the amount of load restoration and guarantee the dynamic performance of system frequency response during the restoration process. After extreme events, the damaged distribution systems can be sectionalized into several isolated MGs to restore critical loads and tripped non-black start distributed generations (DGs) by black start DGs. However, the high penetration of inverter-based DGs reduces the system inertia, which results in low-inertia issues and large frequency fluctuation during the restoration process. To address this challenge, we propose a two-level simulation-assisted sequential service restoration model, which includes a mixed integer linear programming (MILP)-based optimization model and a transient simulation model. The proposed MILP model explicitly incorporates the frequency response into constraints, by interfacing with transient simulation of inverter-dominated MGs. Numerical results on a modified IEEE 123-bus system have validated that the frequency dynamic performance of the proposed service restoration model are indeed improved.