A grid simulator to evaluate control performance of grid-connected inverters

Grid simulators are used to test the control performance of grid-connected inverters under a wide range of grid disturbance conditions. In the present work, a three-phase back-to-back connected inverter sharing a common dc bus has been programmed as a grid simulator. Three phase balanced disturbance voltages applied to three-phase balanced loads has been considered in the present work. The developed grid simulator can generate three phase balanced voltage sags, voltage swells, frequency deviations and phase jumps. The grid simulator uses a novel disturbance generation algorithm. The algorithm allows the user to reference the disturbance to any of the three phases at any desired phase angle. Further, the exit of the disturbance condition can be referenced to the desired phase angle of any phase by adjusting the duration of the disturbance. The grid simulator hardware has been tested with different loads - a linear purely resistive load, a non-linear diode-bridge load and a grid-connected inverter load.