Browsing by Author "Ashraf, Haris Bin"

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    Vector Based Control for Power Electronics Dominated AC Power Grid
    Ashraf, Haris Bin (Virginia Tech, 2025-02-14)
    The global trend towards electrifying the grid has positioned power electronics at the forefront of modern power systems. To control power electronics in grid-connected applications, Grid Forming (GFM) control has become a focal point of research. GFM control utilizes control laws derived from steady-state relationships in the phasor domain. Although these control methods have historically performed well in traditional power systems dominated by electrical machines, they exhibit unexpected control issues in power electronics-dominant power systems. The root of these unexpected behaviors lies in the foundational assumptions of these control methods (Droop control and Virtual Synchronous Machine) i.e. frequency is considered to be a steady state quantity which is constant within the fundamental line cycle. This thesis critically examines these assumptions and elucidates their potential inapplicability in power electronics-dominated power systems. This thesis also introduces vectors as an alternative representation of voltages and currents. Unlike phasors, vectors are instantaneous and time-varying representation of electrical quantities at any point in time, defined by three time-varying values: Magnitude, Polar angle, and Azimuthal angle, using the spherical coordinate system. An initial attempt to demonstrate the capability of using these vectors to control the active and reactive power in inverters connected to the grid has also been presented in this thesis. The proposed vector-based control is able to track the commanded power setpoints within a fraction of the fundamental AC voltage cycle.