Network-Independent Incremental Passivity Conditions for Grid-Forming Inverter Control

TL;DR

This paper demonstrates that Hybrid-Angle Control for grid-forming inverters ensures large-signal stability and passivity regardless of network topology, enhancing grid robustness with renewable sources.

Contribution

It establishes decentralized, network-independent passivity conditions for Hybrid-Angle Control, guaranteeing global stability in inverter-interfaced power systems.

Findings

Hybrid-Angle Control exhibits incremental passivity at AC and DC ports.

Decentralized conditions certify passivity regardless of network topology.

Passivity is preserved under both large-signal and small-signal analyses.

Abstract

Grid-forming inverters control the power transfer between the AC and DC sides of an electrical grid while maintaining the frequency and voltage of the AC side. This paper focuses on ensuring large-signal stability of an electrical grid with inverter-interfaced renewable sources. We prove that the Hybrid-Angle Control (HAC) scheme for grid-forming inverters can exhibit incremental passivity properties between current and voltage at both the AC and DC ports. This incremental passivity can be certified through decentralized conditions. Inverters operating under HAC can, therefore, be connected to other passive elements (e.g. transmission lines) with an immediate guarantee of global transient stability regardless of the network topology or parameters. Passivity of Hybrid Angle Control is also preserved under small-signal (linearized) analyses, in contrast to conventional proportional droop laws that are passivity-short at low frequencies. Passivity and interconnected-stability properties are demonstrated through an example case study.