On the input admittance of a universal power synchronization controller with droop controllers

TL;DR

This paper derives the input admittance of a universal power synchronization controller integrated with droop controllers, analyzing its stability and passivity for grid-forming converters operating in parallel with generators.

Contribution

It provides a novel derivation of the input admittance for a unified control framework with droop controllers, enhancing understanding of stability and passivity in such systems.

Findings

Proportional components of QV and PV control improve passivity.

Sensitivity analysis demonstrates stability benefits.

Case study confirms practical applicability.

Abstract

Recent work has proposed a universal framework that integrates the well-established power synchronization control into vector current control. Using this controller for the parallel operation of grid-forming converters, and/or with loads that have strong voltage magnitude sensitivity, requires additional loops manipulating the voltage magnitude, e.g., $QV$ and $PV$ voltage-power droop controllers. This paper derives the input admittance of the resulting overall scheme. Sensitivity analyses based on the passivity index demonstrate the benefits of the proportional components of $QV$ and $PV$ control. A case study is presented where a grid-forming converter is operated in parallel with a generator.