An analysis of the potential impacts of electromechanical oscillations on the stability and power quality of distributed generation systems

The paradigm that distribution networks are free from problems related to electromechanical oscillations (due to their mainly passive nature and relatively large resistances) is about to change with the increase in the number of small generators connected to them. This paper shows a real situation in which the connection of a few small generators in the distribution network can significantly deteriorate the damping in the system response to small perturbations. The effects of the system response on the power quality across the network are also discussed. The analyzed system is located within the state of Sao Paulo, Brazil, having 3 feeders (comprising 57 kilometers of cables) and 32 buses distributed along these feeders. The need for an adequate assessment of the oscillations and their impacts over power quality is pointed out. It is shown that conventional PSSs can be a simple, cheap, and effective solution to keep the power quality standards as the number of generators entering the grid increases.