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

Rodrigo Bernal, Taulant Kerci, Federico Milano

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.

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

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.
Paper Structure (5 sections, 14 equations, 1 figure)

This paper contains 5 sections, 14 equations, 1 figure.

Table of Contents

  1. Introduction
  2. Nomenclature
  3. Proposed System-wide Dynamic Metric
  4. Case Study
  5. Conclusions

Figures (1)

  • Figure 1: 39-bus system: load outage at bus 8 for $R/X\in\{0.1,1.0\}$. Panels (a) and (e): magnitude of the apparent system losses and frequency of the coi. Panels (b) and (f): real and imaginary parts of the cf of the local components. Panels (c) and (g): real and imaginary parts of the cf of the network components. Panels (d) and (h): real and imaginary parts of the cf of the losses.