Aggregated Dynamic Equivalent of a Distribution System Hosting Inverter-Based Generators

An equivalent, i.e. a reduced-order model, of active distribution networks is derived, for use in (phasor-mode) dynamic simulations of large-disturbances. In the unreduced model, the network hosts a large number of inverter-based generators, responding to the disturbances in accordance with recent or near-future grid codes. The aggregated equivalent is of the “grey-box” type and its parameters are tuned in the least-square sense to match the dynamic responses of the unreduced system to several training disturbances. Changes in operating point are easily reflected when initializing the reduced model. Simulations are reported on a detailed 75-bus distribution system. The accuracy of the equivalent has been checked with respect to untrained disturbances and changes of the operating point.