A calculation method for the short-circuit current contribution of current-control inverter-based distributed generation sources at balanced conditions

Abstract

When a grid-connected inverter-based distributed generation (IBDG) source behaves as a current source that can limit its magnitude in current loop control, the contribution from the inverter to the short-circuit current (SCC) is not as significant as those from conventional synchronous generators. However, the increased IBDG sources can change the magnitude and phase angle of the SCC, so they should not be ignored in SCC calculation. The objective of this study is to present a method for calculating the SCC of an IBDG source of acting as an internally either limited or unlimited current source at balanced conditions. For this purpose, negative- and zero-sequence networks are transferred to a positive-sequence network with balanced IBDG sources. Subsequently, SCCs and zero-, negative-, and positive-sequence induced voltage are determined by using zero- and negative-sequence current injection matrices. Then, new SCC calculation equations for a single line-to ground, line-to-line ground, line-to-line, or three-phase fault are also derived. As a result, the proposed method improves the conventional method in terms of taking the contribution from a balanced IBDG source to SCC into account.