Criteria-Aware EMT-Based Short-Term Voltage Performance Index for Dynamic Assessment of Inverter-Dominated Power Systems

Jul 16, 2026

Upload by Sage

Inverter-based resources (IBRs) have changed short-term voltage dynamics after disturbances, making steady-state strength metrics such as short-circuit capacity insufficient for judging post-fault bus voltage behavior. A criteria-aware, electromagnetic-transient (EMT) metric, the Short-Term Voltage Performance Index (STVPI), evaluates waveform quality against user-defined limits using a weighted log-amplitude ratio and half-cycle comparisons. Kullback–Leibler divergence yields directional indices (STVPI+ and STVPI−) combined into baseline-corrected severity scores, aggregated into bus- and event-level measures (BSTVPI, ESTVPI). Validation on IEEE 9- and 39-bus systems shows significant ranking mismatches versus SCC, highlighting the need for waveform-level assessment for contingency ranking and weak-bus identification.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages10

Reading Time25 min

Abstract

Introduction

Limits of SCC/SCR-based grid strength metrics

Short-term voltage stability assessment approaches

Need for EMT waveform-based criteria-aware indices

Criteria-Aware EMT-Based Short-Term Voltage Performance Index for Dynamic Assessment of Inverter-Dominated Power Systems Mohammad Almomani, Graduate Student Member, IEEE, and Venkataramana Ajjarapu, Fellow, IEEE arXiv :2607 .06825v1 [ ee ss . SY] 7 Jul 2026 Abstract—The increasing penetration of inverter-based resources (IBRs) into bulk power systems has fundamentally altered short-term voltage dynamics following disturbances. Conventional short-circuit capacity (SCC) metrics provide a useful screening indicator of grid strength but are unable to fully capture post-disturbance voltage behavior at buses with dynamic loads, converter controls, or protection interactions. A bus with high SCC may still experience deep voltage dips, delayed recovery, or transient overvoltage that violates operating criteria. This paper proposes the Short-Term Voltage Performance Index (STVPI), an electromagnetic-transient (EMT)-based, criteriaaware metric that quantifies the quality of the post-disturbance voltage waveform relative to user-defined performance limits. STVPI processes voltage signals at the half-cycle level by computing a weighted log-amplitude ratio between the actual waveform and an ideal half-sine reference. Monotonic recovery envelopeson the overvoltage and undervoltage sides are compared against half-normal reference distributions using Kullback–Leibler (KL) divergence, normalized by the KL divergence of the critical voltage envelope, yielding two directional indices—STVPI+ and STVPI −—whose combination produces a baseline-corrected scalar severity score. Bus-level and event-level aggregation derive BSTVPI and ESTVPI, enabling simultaneous identification of dynamically weak buses and critical fault contingencies. The framework is validated on the IEEE 9-bus and 39-bus test systems with IBR integration, demonstrating applications in contingency ranking, weak-bus identification, control and protection evaluation, model validation, and scenario reduction. Results reveal significant mismatches between SCC-and STVPI-based rankings (Kendall τK ≈ 0.41), confirming that dynamic interaction effects require waveform-level assessment beyond steady-state strength metrics. Index Terms—Electromagnetic transient simulation, inverterbased resources, short-circuit ratio, short-term voltage stability, voltage performance index, Kullback–Leibler divergence, contingency ranking, weak bus identification. I. INTRODUCTION The rapid integration of inverter-based resources (IBRs)—including utility-scale photovoltaic (PV) generation, battery energy storage systems (BESS), and Type III/IV wind turbines—into transmission-level power systems has substantially modified the dynamic voltage response following disturbances. Unlike synchronous generators, IBRs exhibit currentlimited, control-dominated fault behavior, fast reactive-current injection, and voltage-dependent power reduction, each of which interacts with the surrounding network in ways that The authors are with the Department of Electrical and Computer Engineering, Iowa State University, Ames, IA 50011 USA. Emails: {mmomani, [vajjarap](vajjarap}@iastate.edu. Website: {)[}](vajjarap}@iastate.edu. Website: {)[@iastate.edu. Website:](vajjarap}@iastate.edu. Website: {)[ {](vajjarap}@iastate.edu. Website: {)[https://mohammadalmomani.github.io/.](https://mohammadalmomani.github.io/.})[}](https://mohammadalmomani.github.io/.}) cannot be captured by quasi-static or phasor-domain metrics alone [1]–[3] . Short-circuit capacity (SCC) and related metrics, includingthe short-circuit ratio (SCR), multi-infeed effective SCR (MESCR), generalized SCR (gSCR), and more recent renewablecluster variants, were developed to characterize the electrical strength of the network seen by an IBR [4]–[7] . These indices remain important for interconnection screening and identifying weak-grid conditions; however, they are fundamentally steadystate, impedance-based measures. They do not explicitly represent the tr

FAQs

Why are SCC/SCR-type metrics insufficient for short-term voltage assessment with inverter-dominated systems?

They are steady-state, impedance-based measures and do not represent transient voltage trajectories after disturbances, including delayed recovery, transient overvoltage, or protection- and control-driven interactions.

How does the proposed STVPI quantify post-disturbance voltage performance?

STVPI processes voltage at the half-cycle level by computing a weighted log-amplitude ratio between the actual waveform and an ideal half-sine reference, then compares monotonic recovery envelopes to reference distributions using Kullback–Leibler divergence to form directional indices.

What do the IEEE test-system validations show compared with SCC-based rankings?

On IEEE 9-bus and 39-bus systems with IBR integration, the rankings produced by STVPI and SCC differ substantially (reported Kendall τ≈0.41), indicating that dynamic interaction effects require waveform-level, criteria-aware evaluation.

Jul 16, 2026

Upload by Sage