System-wide Dynamic Performance Metric for IBR-based Power Networks

TL;DR

This paper introduces a unified system-wide dynamic performance metric for power networks with inverter-based resources, capturing the combined effects of voltage and frequency dynamics for improved grid assessment.

Contribution

It proposes a novel weighted sum metric based on local voltage variations and complex power, decomposed into device and network components, for comprehensive dynamic performance evaluation.

Findings

The metric effectively captures dynamic behavior in inverter-based power systems.

Sensitivity analysis shows the metric's applicability across different grid configurations.

Case study demonstrates the metric's ability to distinguish performance variations.

Abstract

In power networks based on Inverter-Based Resources (IBRs), fast controllers cause frequency and voltage dynamics to overlap. Thus, it becomes critical to assess the overall dynamic performance of such networks through a combined system-wide metric. This letter presents a unified metric designed to evaluate dynamic performance in such cases. The proposed metric consists of a weighted sum of local voltage phasor variations at each bus, where the weights are the complex powers injected at the buses. The proposed metric is further decomposed into device-driven and network-driven components, enabling a more comprehensive assessment of grid dynamics. A case study based on a modified version of the IEEE 39-bus system is presented, in which synchronous machines are replaced by inverter-based resources. A sensitivity analysis of the R/X ratio is utilized to evaluate the metric in conventional grids, as well as in those characterized by strong voltage-frequency coupling with complex power flows.