The influence of inverter-based DGs and their controllers on distribution network protection

The ever growing penetration of distributed generation (DG) in a distribution network has a profound impact on the network protection and stability. Traditional protection schemes and algorithms need to be extensively investigated as more and more DGs get introduced into the network. The current version of IEEE Std 1547 does not present a comprehensive solution for fault current detection in the presence of various kinds of DGs. Power electronic inverter-based DGs are of special concern in distribution network protection as they are often incapable of providing sufficient fault current and their controllers play a principal role in the DG behavior. In this paper, the effects of voltage and current controllers for inverter-based DGs on industrial and commercial power system distribution network protection schemes are investigated. It is shown that the type of controller and its design parameters during the fault have a direct impact on fault current levels and duration. A simplified distribution network model with inverter-based DG operating under voltage and current control modes was tested to verify the effects of these controllers. This paper also proposes an adaptive relaying algorithm to detect the faults in the presence of inverter-based DGs with various types of controllers.