Abstract
With an increasing capacity of inverter-based generation and with a 100% renewable energy power system on the horizon, grid forming converters have the potential to become the prevalent control mode in the grid. Thus, the correct performance of these devices is going to be crucial for system stability and security of supply. Most research related to the grid-forming control is focused on normal operating conditions, although significant effort has been devoted to current limitation strategies to ensure Low Voltage Ride Through (LVRT) capability. However, most contributions usually consider only balanced faults. This paper, proposes a new current limiting method based on the well-known threshold virtual impedance (TVI) that keeps the voltage source behaviour associated to the grid forming (GFM) capability, even when the current limit is reached, while reducing the voltage unbalance according to user-defined settings.
Highlights
The majority of the inverter-based generation (IBG) connected to the grid is presently based on grid following (GFL) technology
The three different methods for current limiting a grid forming inverter presented in the previous section are compared under unbalanced voltages and faults
The peakLookcurcurrent is estimated taking account the negative sequence, the peak current is ing at FFT of the current without the actuation and when the peak iscurrent actuating, the rent is the estimated taking intointo account the Threshold Virtual Impedance (TVI)
Summary
The majority of the inverter-based generation (IBG) connected to the grid is presently based on grid following (GFL) technology These devices have a phase locked loop (PLL) in order to synchronize with the grid voltage and behave as current sources. As the share of IBG increases, large parts of the system may be operated without synchronous machines In such a scenario, grid-forming (GFM) controls may be required to endow the converter with a voltage source behaviour and so provide the reference for frequency and voltage. Grid-forming (GFM) controls may be required to endow the converter with a voltage source behaviour and so provide the reference for frequency and voltage This change comes at a price: the current exchanged with the grid depends on the impedance between the grid and the converter (two voltage sources). Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
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