2023 journal article

Double Synchronous Unified Virtual Oscillator Control for Asymmetrical Fault Ride-Through in Grid-Forming Voltage Source Converters


By: M. Awal n, M. Rachi n, H. Yu n , I. Husain n & S. Lukic n 

co-author countries: United States of America πŸ‡ΊπŸ‡Έ
author keywords: Oscillators; Synchronization; Voltage control; Phase locked loops; Control systems; Frequency synchronization; Switches; Asymmetrical fault ride-through; fault-ride-through (FRT); grid-forming (GFM) converter; unified virtual oscillator controller (UVOC)
Source: Web Of Science
Added: May 30, 2023

In this work, a double synchronous unified virtual oscillator controller is proposed for grid-forming voltage source converters to achieve synchronization to the fundamental frequency positive- and negative-sequence components of unbalanced grid voltage without any phase-locked loop. The proposed controller leverages a positive-sequence virtual oscillator and a negative-sequence virtual oscillator, a double-sequence current reference generator, and a double-sequence vector limiter. Under fault conditions, the controller enables to limit the converter output current below/at the maximum value allowable by the converter hardware while retaining synchronization regardless of the nature of grid faults. Consequently, symmetrical and asymmetrical fault ride-through can be achieved without the need for switching to a backup controller. This article presents the implementation and detailed analysis of the double-synchronous structure, which enables simultaneous synchronization to both sequences during current-unconstrained and -constrained operations. Validation of the proposed controller is provided through laboratory hardware experiments.