Optimal Emergency Frequency Control Based on Coordinated Droop in Multi-Infeed Hybrid AC-DC System

TL;DR

This paper introduces a decentralized emergency frequency control method for multi-infeed hybrid AC-DC systems, using coordinated droop control and optimal parameter selection to enhance frequency stability during emergencies.

Contribution

It proposes a novel decentralized emergency frequency control strategy with optimal droop coefficient allocation for MIDC systems, ensuring stability and improved frequency regulation.

Findings

The control strategy effectively stabilizes frequency during emergencies.

Lyapunov analysis confirms local asymptotic stability.

Simulations demonstrate improved frequency response.

Abstract

In multi-infeed hybrid AC-DC (MIDC) systems, the asynchronous interconnection between regional grids, the complicated system dynamics and possible cascading failures have an enormous effect on the frequency stability. In order to deal with the frequency instability problems in emergency situations, this paper proposes a decentralized emergency frequency control strategy based on coordinated droop for the MIDC system. First, a P-f droop control for LCC-HVDC systems is introduced and the coordinated droop mechanism among LCC-HVDC systems and generators is designed. Then, to reasonably allocate the power imbalance among LCC-HVDC systems and generators, an optimal emergency frequency control (OEFC) problem is formulated, and the optimal droop coefficients are selected in a decentralized approach, which can deal with various control objectives. A Lyapunov stability analysis shows that the closed-loop equilibrium is locally asymptotically stable considering the LCC-HVDC dynamics. The effectiveness of the proposed emergency control strategy is verified through simulations.