Ahmad Afif Nazib
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Preferred name
Ahmad Afif Nazib
Official Name
Ahmad Afif, Nazib
Alternative Name
Nazib, Ahmad Afif
Nazib, A. A.
Nazib, Ahmad A.
Main Affiliation
Scopus Author ID
56125536300
Researcher ID
DLD-1667-2022

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Autonomous Current Sharing Control with Integrated Virtual Impedance and Self Synchronisation for Unbalanced Islanded Microgrids

2020-10-11 , Ahmad Afif Nazib , Holmes D.G. , McGrath B.P.

This paper proposes a new autonomous current sharing control strategy for islanded microgrids that is simple and robust under unbalanced load conditions. The strategy estimates the distributed generator output voltage and current positive sequence components from the internal variables of a resonant current and resonant voltage regulator, and then uses them to create an integrated virtual impedance sharing mechanism. This avoids control complexity and the need for output current measurements, while maintaining a balanced voltage and accurate current sharing. The approach has been verified using a detailed switched simulation.

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Virtual flux-based grid-forming current controller for flexible operation of voltage source converters

2022-01-01 , Ahmad Afif Nazib , Holmes D.G. , McGrath B.P.

This paper presents a novel approach to incorporate a grid forming capability into a grid-following voltage source converter, while maintaining the high-bandwidth current control capability that is typical of such a converter. The approach uses the resonator outputs of a stationary frame current regulator as a virtual flux estimation of the converter output voltage, and integrates this estimation into an electrical model of a virtual synchronous generator without requiring integration and derivative operations. The generator and converter models are then combined to achieve a robust grid-forming response under grid islanding conditions, without requiring direct grid-side voltage measurements. The proposed strategy is validated using a detailed switching simulation model of the converter and its control processes.

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Enhanced Transient Performance of a Self-Synchronising Inverter during Start up and Severe Grid Fault Conditions

2020-11-29 , Ahmad Afif Nazib , Holmes D.G. , McGrath B.P.

This paper explores the process of transient inrush current associated with inverters during grid connection startup and grid fault events. The analysis presented identifies the equivalence between both scenarios and investigates the influence of the filter impedance and current controller bandwidth on these current transients. A novel strategy is then proposed to minimise the impact of such transient events, which achieves both a seamless start up, and is capable of riding through a solid short circuit (i.e. zero voltage or crowbar) grid fault. The strategy has been verified via detailed switched simulation and experimental investigations.

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Self-synchronizing stationary frame inverter-current-feedback control for lcl grid-connected inverters

2022-04-01 , Ahmad Afif Nazib , Holmes D.G. , McGrath B.P.

Current regulation of inductive-capacitive-inductive (LCL) grid-connected inverters usually requires multiple current sensors to actively damp the filter resonance. Inverter-side current regulation avoids this issue because of its inherent LCL filter damping properties but does not accurately control the grid-side current, particularly with distorted grids. Furthermore, both strategies typically require high-quality voltage sensors to maintain precise grid synchronization. This article proposes a novel current control strategy for LCL grid-connected inverters that only requires inverter-side current sensors. The strategy uses the resonator output states of a stationary reference frame (SRF) proportional resonant (PR) current regulator to estimate the grid voltage phase and filter capacitor current and, thus, achieve self-synchronized indirect regulation of the grid-side current. The effectiveness of the approach has been verified using simulation and matching experimental investigations.

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