The sub-transient, transient, and steady-state models for three-phase inverter based distributed generators for the purpose of real-time short-circuit analysis

Abstract

In this paper the sub-transient, transient, and steady-state short-circuit models for inverter based distributed generators (IBDGs) are proposed. Until the last two decades the only active elements connected to the distribution systems were synchronous and induction machines. The dynamic behaviour of these machines has been approximated by three steady-state time periods: sub-transient, transient, and steady-state, in order to have real-time short-circuit calculations. In recent years deployment of IBDGs is constantly increasing. Currently, the IBDGs do not have generally accepted short-circuit models. Therefore, there is an urgent need for development of these models, in order to have accurate short-circuit calculations of modern distribution systems. The IBDG models proposed in this paper are based on Fault Ride Through requirements of the currently existing Distribution Codes. The proposed models are divided on sub-transient, transient, and steady-state models, in order to simulate their dynamic behaviour and to comply with the models of traditional generators. To validate the proposed models, they were integrated in the recently developed real-time short-circuit calculation procedure for active distribution systems. The IEEE 13 test feeder and several large-scale distribution systems consisted of as many as 5200 three-phase busses and 50 IBDGs were used as the cases studies. The simulation results showed that the proposed models provide desirable results for real-time short-circuit calculations in active distribution systems.