The influence of grid-forming loads on transient stability

With the integration of renewable energies the share of inverters in the grid increases and thus the inertia of the system is weakened. Grid-forming inverter coupled loads can contribute to system inertia. Handling of short circuits becomes a challenge. In contrast to synchronous generators, a grid-forming inverter coupled load decelerates during a fault, in dependence on the gridforming control, and can shorten the critical clearing time of the system. In this paper, we present a control scheme based on the virtual synchronous machine for a grid-forming inverter coupled load and propose different methods that change the frequency behavior during fault. Therefore, different current limitation methods and the adjustment of parameters during fault are analyzed. Good transient stability can be achieved with the help of the appropriate method and parameterization. Changing the inertia constant and adjusting the active power setpoint have proven to be particularly effective which is shown in MATLAB/Simulink simulations.