SMIB system PSCAD simulation

This is the PSCAD simulation for the article "Grid Impedance Adaptive VSG Control Based on Accurate Small-Signal Modelling".Abstract — The wide integration of renewable energy sources results in a higher penetration of inverter-based generators, which leads to reduced grid strength and inertia that expose challenges to power system stability. Virtual synchronous generator (VSG) has been developed recently as a promising grid-forming (GFM) technology to address these stability issues under weak grid conditions, which can autonomously provide active and reactive power support as well as inertia to the power network in response to disturbances. However, when a VSG inverter interacts with a strong power grid, energy oscillations tend to propagate between the inverter and grid, and the traditional stability analysis method based on dynamic response is not sufficient in this case since the inverter has problems reaching steady state under certain conditions. Therefore, new stability assessment methods based on impedance analysis have been developed, and an accurate impedance model is critical to the effectiveness of these methods. This paper proposes a closed-loop approach to capture the variations of the overall impedance of a single-machine infinite bus (SMIB) system for analyzing and controlling the small-signal stability of a virtual synchronous generator (VSG), with two separate approaches to model the impedances on the inverter side and the grid side. The grid-forming inverter-side impedance is represented by a small-signal model under the dq reference frame, while the grid-side impedance is estimated from the frequency scan result. A VSG stability control method adaptive to grid impedance is also developed based on the close-loop modeling framework. The proposed system has been validated by PSCAD simulations and comparative studies with existing techniques, and the testing results demonstrate high fidelity of impedance modeling and the capability of adaptive VSG control against a wide range of grid impedance variations.