Sub-Transient Response of the DSC Controlled Inverter under Fault

The most important element of the new active distribution system concept is the grid connected converter that needs to offer fault ride through capabilities. The new system topologies require new tools for fault state calculation that would consider different control methodologies. In that regard, this paper investigates the initial response of the grid connected inverter under fault that operates using new control methodology based on the integration of the delay signal cancellation. Using modern laboratory setup for testing of renewable energy sources and their integration in the power system the technique is weighed against the classical technique that does not provide the adequate control under unbalanced faults. Furthermore, through a set of specific experiments the paper demonstrates the behavior of the converter under fault, preparing the outline for the fault response modeling of distributed energy resources. Experimental results present the sub-transient period and the transient period of the response, giving the attention to the inrush current (initial peak current) of the converter. It has been shown that the new technique has similar behavior as the classical control for the balanced faults (symmetrical voltage states), while the values of the peak current for different type of unbalanced faults (asymmetrical voltages where classical technique can be proven to be ineffective) has also been demonstrated.