Contribution to Bulk System Control and Stability by Distributed Energy Resources connected at Distribution Network

The penetration of Distributed Energy Resources (DER) within the Distribution Network (DN) increases worldwide. This increase of local generation has led to various changes in the philosophy of DN operation. The changing nature (higher participation of power electronic components) of connected system loads and distributed generation (DG) is creating new challenges for the operation of transmission and distribution networks and DG units will be requested to provide more ancillary services.
When DER reach a certain level of penetration, they have an impact on the overall steady state and dynamic performance of the bulk electric power system. Moreover, the increased power injections at the DN can cause overvoltage problems and reverse power flows that may affect the protection settings within the distribution system. A DN with high penetration of DERs responds dynamically to system disturbances and therefore affects overall power system stability and dynamic behavior.
DER, when properly controlled can provide support to the upstream network by supporting the reactive power needs of the loads (at the distribution level) and flow reduction in case of congestions by supplying the demand at the distribution level. Control can be basically exercised by exploiting the power electronic converters used to interconnect most types of DER. The provision of support to transmission network (TN) operation by DER is already required by operating codes in some countries.