Title:
Parametric Small-Signal Modeling of Grid Forming and Grid Following Inverters in 100\% Renewable Based Grid
Parametric Small-Signal Modeling of Grid Forming and Grid Following Inverters in 100\% Renewable Based Grid
Author(s)
Bagherzadeh Karimi, Araz
Advisor(s)
Saeedifard, Maryam
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Abstract
Due to the concerns about global warming and its critical environmental consequences, nearly all power systems in the world are or will aim to become 100 \% renewable-energy-based to prevent the use of fossil fuels in the near future. This future grid with 100\% inverter-based generation is structurally different in response to various phenomena. Therefore exact modeling of inverters in this new structure is a crucial task. In this thesis, a new parametric exact small-signal model of the \gls{GFM} and \gls{GFL} is introduced. Different control strategies for GFM such as virtual-inertia-based, synchronvertor, power synchronization control, and droop are considered. New control loops that relate the measured signals to the angle generation block in GFM are introduced. To obtain the exact model, all inverter block diagrams are converted to matrix form, and nonlinear blocks such as power measurement, DC-side dynamics, $dq/abc$ frame transform, PLL, and GFL droop are linearized to be converted to matrix form. Then, a set of first-order algebraic equations are formed based on the matrix equations and computationally solved in MATLAB. After derivation of output admittance in matrix form, derived block components are replaced to form four transfer functions that define the dynamics of the inverter. The results show the significant dependency of inverter stability on a steady-state angle obtained via load flow and current loop proportional gain, and therefore a stability margin for steady-state angle is derived, which is analogous to the angle stability of synchronous generators. The synchronvertor controller shows a very complex transfer function with the most unstable and challenging behavior among the rest of the inverters.
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Date Issued
2022-09-06
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Text
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Thesis