Banca de QUALIFICAÇÃO: UCHENNA CHIBUZOR NGWU

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : UCHENNA CHIBUZOR NGWU
Date: 31/07/2026
TIME: 14:00
LOCAL: https://meet.google.com/nat-ajfg-rtk
TITLE:

Frequency-Deviation Based Adaptive Virtual Impedance for Fault Current Limitation in Grid-Forming Inverters Under Grid Disturbances

PAGES: 68
BIG AREA: Engenharias
AREA: Engenharia Elétrica
SUMMARY:

Grid-forming (GFM) inverters are essential enabling technology for future power systems with high penetration of inverter-based resources. However, their voltage-source nature makes them inherently vulnerable to overcurrent during grid faults, as semiconductor devices tolerate only 1.2–2 per unit of overcurrent for very short durations. This vulnerability is particularly severe under very weak grid conditions, where even moderate disturbances can induce fault currents exceeding the inverter’s safe operating limits.

This dissertation reviews existing overcurrent limiting methods for GFM inverters and proposes a novel frequency deviation based adaptive virtual impedance strategy for fault current limitation. The VSG frequency deviation signal ∆ω is adopted as the triggering variable, enabling immediate response to both voltage sag and phase-jump disturbances. Key parameters are optimally tuned using Particle Swarm Optimization (PSO) across a combined multi-disturbance simulation for robust cross disturbance performance.

The proposed method is evaluated against without-VI and constant-VI baselines across four disturbance scenarios: 50% voltage sag, 80% voltage sag, +45° phase shift, and −45° phase shift under SCR = 1.5 in a MATLAB Simulink and PLECS cosimulation. Results demonstrate peak fault current reductions of 21% to 33% versus the without-VI baseline and 14% to 26% versus constant VI, with superior reactive power management, prevention of active power reversal under phase jumps, and consistently fastest post-fault recovery all without degrading frequency stability.

COMMITTEE MEMBERS:
Presidente - Interno ao Programa - 2079380 - JOSE LUIS AZCUE PUMA
Membro Titular - Examinador(a) Interno ao Programa - 1545354 - RICARDO CANELOI DOS SANTOS
Membro Titular - Examinador(a) Externo ao Programa - 2200473 - JOSE ALBERTO TORRICO ALTUNA
Membro Suplente - Examinador(a) Externo à Instituição - ELMER OSMÁN HANCCO CATATA - UFAC