Advanced Modelling of Equivalent Networks Considering Full-Size Converters in Short-Circuit Current Calculations According to IEC 60909-0:2016

Abstract:
In 2016 the second edition of the standard IEC 60909-0:2016 has been published and for the first time the fault current contribution of full-size converters is considered. This accounts for the growing share of converter-interfaced generation connected to the grid. Currently, an equivalent network based on a voltage source model with an internal impedance comparable to the modelling of a synchronous machine. However, this procedure needs to be re-evaluated, because a growing share of full-size converters alters the behaviour of the network. An advanced modelling approach for equivalent networks is presented in this paper. As a first step, full-size converters within the equivalent network are modelled as ideal current sources, which allows to consider their short-circuit current contribution. As a second step, the voltage dependency of the reactive current infeed of the full-size converters is modelled in order to get more accurate results. This analysis will show if full-size converters within an equivalent network can be generally neglected. A special method for modelling remotely fed grids is used to account for the voltage-dependent current infeed of power plants with full-size converters within the equivalent network.