Improved dynamic model of small stand-alone diesel generators to assess the stability of autonomous microgrids

Many remote, isolated communities rely on diesel generators to meet their electrical demands because connecting to conventional electrical grids is either too expensive or technically impractical. In such situations, microgrids made up of diesel gensets and renewable energy sources are most appropriate. However, when diesel generators operate with reduced operating reserve margins, these isolated systems do not have sufficient capacity to withstand large electrical transients, which can lead to instability. As a result, a more detailed evaluation of acceptable levels of renewable energy penetration is required. Hence, the focus of this work is to develop a high-fidelity model for small three-phase diesel generators (SDG), incorporating adaptations to the traditional IEEE Exciter and the Woodward Diesel Engine-Governor Model, with the goal of enhancing the accuracy of dynamic frequency and voltage responses. The effectiveness of the proposed SDG model is validated using field test data of a three-phase genset of 40 kVA–220 V that is part of an operational microgrid. The results show that the accuracy of the proposed model is satisfactory, presenting Normalized Mean Squared Error (NMSE) values around 16% and 10% for speed and voltage responses, respectively.