Strength assessment of electric power systems containing inverter-based distributed generation

Large-scale penetration of inverter-based distributed generation (IBDG) systems such as wind and solar PV plants into conventional power systems is raising concerns for traditional methods of power system operation and control. System strength at the point of interconnection (PoI) of the IBDG is one such concern, measured by the short circuit ratio (SCR). However, SCR and other SCR-based methods disregard interactions and electrical connections that exist amongst IBDGs. This study proposes an alternative method using the theory of power system network structural characteristics. The network response short circuit ratio (NRSCR) method captures the interaction among IBDGs and with nearby synchronous generators without having to solve the power flow problem. In addition, it does not require inversion of the systems' admittance matrix. Comparative analysis of the proposed method with other SCR-based methods is demonstrated by showing the relationship between system strength, voltage stability, and active power transfer.