Modelling and computer simulation of dispersed generation in distribution networks. Measures to prevent disconnection during system disturbances

Dispersed generation (DG) from renewable resources and mini-cogeneration in public MV and LV distribution networks has so far been a small part of total installed capacity of power systems. This situation has justified the requirement in the technical standards in force in various countries that DG must be automatically disconnected at the occurrence of faults or abnormal operation conditions of the public network. A massive installation of DG is encouraged in many countries. If this target will be achieved, the automatic disconnection of large amounts of DG in an area initiated by network short circuits would drastically reduce the expected benefits of DG. The paper presents models for simulation of DG and investigates the possibility of keeping DG in service during network disturbances, in particular: assumptions are made on possible future extensive applications of DG in regional networks. Dynamic simulations of distribution networks with adequate models of DG using various interfacings (synchronous generators (SGs); asynchronous generators (AGs); static power converters (SPCs)) are set up. Results of parametric analyses are presented for significant case studies and conditions to be fulfilled are identified for avoiding or minimizing disconnection of DG during short circuits in HV, MV and LV networks. Simulations are made with PSAF program for the comprehensive study of DG interfaced with SGs, AGs, and SPCs. The ATP-EMTP is used for the analysis of special transients. Results show that it is possible to ride through the network faults by keeping in service DG and loads except SGs connected to faulty distribution lines.