Fault Current Limitation Based Photovoltaic DC Distribution System Fault Ride Through Control

The fault ride through (FRT) ability of the photovoltaic (PV) DC distribution system (PV-DCDS) is required during an AC system fault. However, due to the inherent calculation delay of grid connected converter (GCC), overcurrent may appear instantly in the fault initial stage (before the controller responding) and might trigger the GCC's instantaneous overcurrent protection, causing the failure of FRT. In addition, the capacities and control response speeds of converters in PV-DCDS differs to each other, leading to the active power fluctuation during FRT period, causing the fluctuation of DC voltage out of allowable range, which deteriorates the FRT control. To address the above issue, a current limitation based FRT control is proposed. Once the DC voltage reached the preset voltage threshold, the redundant sub-modules (SM) of GCC would be temporarily activated by arm controller. In the fault transient stage (controller responding), a synchronous link is designed to synchronize the reactive power regulating speed of GCC with that of active power of PVs. The simulation results demonstrate that the proposed strategy can achieve a smooth FRT under various grid faults.