Emerging distribution systems: Modeling challenges in faulted conditions

The objective of this paper is to summarize the challenges imposed by emerging technologies, such as distributed energy resources (DERs), to modeling and online calculations of faulted distribution systems. In the last decade, the connection of DERs to the system through power electronic devices has become increasingly popular. These DERs have controlled fault currents, with predefined current limits. Therefore, they cannot be modeled with traditional voltage source behind impedance models, used for modeling synchronous and induction machines in online calculations. However, most of the software packages for managing distribution systems still use these models for modeling all types of DERs, including electronically coupled ones. In this paper it is shown that this practice could introduce extremely high errors to calculation results, and cause the system model to be an inadequate representation of the system. Therefore, there is an urgent need for global standardization of recently introduced models that more adequately represent these emerging DERs. The results from our previous studies were used to numerically support this claim.