Fault Current Response of Grid-Following Converters Interfaced with Different Transformer Connections

Converter-interfaced renewable sources regulate the current to their rated value during a fault, unlike synchronous generators. Such sources are generally connected to the grid through filter and transformer. The different winding connections of the transformer have an additional effect on the network voltage and current during fault. This paper presents an analytical information on the presence of positive, negative, and zero sequence components of the current and voltage for various connections of transformer and fault types with converter interfaced sources. The effect of different types of winding such as delta-wye grounded, delta-wye ungrounded, and wye grounded-delta on the voltage and current is enquired. The availability check of different sequence components of voltage and current during different fault types helps in deciding the existing protection schemes for the system. A summary of the performance of overcurrent and voltage based protection in a system with converter interfaced sources accompanying different transformer connections is made.