Conditions for increasing DER anti-islanding protection frequency range

Abstract

The changing of the traditional generation profile from TSO-connected to DSO-connected can have the potential to amplify system frequency events if due care is not taken.Commission Regulation (EU) no. 2016/631 established a wider frequency range that Distributed Generation (DG) modules need to comply with, being the driver for increasing the DER contribution to grid stability and security in case of system disturbances. However, those changes may increase the chance of unwanted islanding in the distribution network. Islanding, by itself, does not constitute a situation that needs to be totally prevented. When planned, or controlled, it may be a useful mode of operation in some cases.Currently, frequency protections at the DG level, among other functions, are used by the DSO not only to respond to a systemic event, but also to eliminate unwanted islanded systems. Extending frequency parameters may not be a reliable solution for both systemic and local events. Especially in the presence under-frequency load shedding schemes which will tend to adapt the load to the generation in the network. Hence, other ways for unwanted islanding detection may be required.An extensive study on islanding formation was carried out considering real and simulated scenarios based on two sections of EDPD’s grid connected to different types of generation. It was found that unwanted islanding may occur even without active frequency control generation.Considering the results, this paper will also present the strategy envisioned for the Portuguese grid aiming to contribute to an European synchronous system resilience using additional communication-based anti-islanding detection methods.