Abstract
The proposed research topic in the general area of power system stability analysis focuses in the development of a simplified model for the representation of systems with Distributed Energy Resources (DER), in which undesirable electromechanical oscillations may occur. This is a problem in grids with distributed generators, as in the case of Brazil, especially in the state of Sao Paulo, where the waste recovery of the ethanol production process is a significant source of electric power through cogeneration facilities. Most of these generators are connected to sub-transmission or distribution power grids, near consumer centers. Furthermore, photovoltaic systems in distribution grids are increasing rapidly, and hence this generation sources are becoming an important part of DER. Distributed generation is changing the characteristics of distribution systems, since passive loads are not the only components of these systems as it used to be in the past. Thus, stability studies of Electric Power Systems (EPS) must consider the inclusion of generators at distribution system level, considering their associated dynamics. Quite frequently these studies, aiming at simplifying the problem and related simulations, consider the DER as negative loads ignoring their dynamics. These simplifications have a significant impact on stability studies, resulting in considerable differences between simulations and reality. Although the representation of the generation dynamics is important, the level of detail in the equations used to model them cannot be high, since that would increase significantly the complexity of the simulations and, consequently, their execution time. Thus, the modeling of a synchronous generator through a complete model, which takes into account the electromechanical dynamics of the generator and the imbalance of distribution systems, is infeasible for studies of large EPS. Hence, the main focus of this research project is the development of a simplified model of distribution feeders with synchronous-machine generators through the use of controlled voltage sources, which does not consider frequency and rotor angle variations, since from the perspective of the EPS, these do not have a significant impact on the large grid, as observed from actual field measurements. The validation of this model will take place by comparing real measurements for distributed generation systems and the response of the proposed model. (AU)
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