Load Shedding Schemes in Presence of DER

This poster presents a summary of issues related to load shedding schemes implementation in presence of DER. It discusses the question for Under Frequency Load Shedding (UFLS) as well as for Under Voltage Load Shedding (UVLS). The first obvious inconvenience with load shedding schemes is their implementation at HV – MV sub-station level or at MV feeder level. This means that load shedding trips simultaneously load and generation, this is not a good option. Further, principles of operation can be affected in presence of DER. The poster considers how DER influences frequency control during emergency situations for different UFLS parameters. For this example the Baltic States power system was selected. The higher level of DER the lower instant value of underfrequency is observed. These results can be the base for conclusions and recommendations. The performances of UVLS are also evaluated. Detailed studies showed that whereas implementation of UVLS in public system is rather difficult with present schemes, it can become quite easy when implemented at domestic customer level. These developments constitute interesting elements for the future of power system. This is clearly a way for increasing reliability of supply as load shedding does no longer mean “zero voltage” at customer level