Photovoltaic (PV) distributed generation (PVDG) has grown significantly in the recent years due to the rapid development of power electronic technologies. The PVDG is usually integrated to distribution systems. The integration of PVDG can alleviate energy demand effectively while reduce air pollution and greenhouse gas emissions. However, with the increasing integration, the PVDG systems inevitably lead to significant challenges on operation of power systems, including protection of distribution systems. In the existing literature, only a few papers discussed the impact of the integration of PVDG on the protection of distribution systems, and the corresponding technical challenges are not fully clarified. To fill the gap, this paper develops a generic distribution system with the integration of a PVDG system to analyze the impact of integration of PVDG on the overcurrent protection of the distribution system. It is found that the control of PV inverters can limit the fault current significantly during a short-circuit (SC) fault. This makes the SC current of the faulted feeder too low to trigger the circuit breaker, leading to a protection failure (should operate but does not). To verify this conclusion, a comparison case with the connection of a traditional synchronous generator is provided in this paper.
Keywords PV generation, protection of distribution systems, current control, PV inverter, SC fault