Suppression of the Dynamic Interactions between a VSG and Dynamic Loads under Weak-Grid Conditions

The virtual synchronous generator (VSG) features more non-oscillatory stable performance under weak grid conditions than stiff grid conditions. However, as shown in this paper, a local industrial load with induction motors jeopardizes this fact and superimposes low-frequency oscillations on the outputs of the weak grid-connected VSG. Detailed small-signal models of a weak grid-connected VSG are developed and compared in the absence and presence of a local industrial load. This study shows that dynamic loads, e.g., induction motors, weaken the VSG damping and limit the stability ranges of the droop gains and virtual inertia constant, limiting the VSG's features and grid-supporting capabilities. Therefore, an active compensator is proposed to regain the VSG's damping and stability under weak grid conditions. With the proposed damping and stabilization compensator, the VSG dynamics and stability are highly improved under wide ranges of droop gains and virtual inertia. Multiple offline simulations and real-time tests are carried out to justify the existence of dynamic interactions between a VSG and an industrial load, considering diverse load compositions, and verify the proposed compensator's effectiveness in enhancing the overall system performance and stability under practical conditions, such as load switching, faults, and grid angle disturbances.