A case study of calculating the short-circuit current of high-capacity power electronics-based distributed energy resources and loads

Since high-capacity distributed energy resources (DERs) are connected to the electric power grid, their short-circuit current (SCC) contribution should not be neglected. That is, the SCC caused by power electronics-based distributed energy resources (PEDERs) can change the magnitude and angle of the SCC of the power grid without PEDERs because the fault current is superposed to that flowing from the conventional rotating synchronous machines. Thus, the objective of this study is to analyze the effect of the SCC caused by relatively high capacity PEDERs on the power grid. For this purpose, this study modifies the current inj ection method so that the SCC flowing from PEDERs that function as a current source can be more accurately evaluated. The results of the case study show that the relatively high capacity of PEDERs (i.e., even up to 2.0 p.u. of a base MV A in the simple radial power grid) do not significantly increase the SCC level. However, the unbalanced PEDERs acting as a current source can cause an increase in overvoltage (e.g., 1.5 p.u.) after a fault. Thus, to increase the capacity of PEDERs, their contribution to SCCs should be taken into account.