Bus-based indices for assessing the contribution of DG to the voltage security margin of the transmission grid

Due to the expected growth in the interconnection of distributed generation around the world, power system operators are now faced with the challenge of looking beyond the distribution networks and consider the transmission grid when assessing the impacts of integrating large amounts of DG. This paper focuses on the analysis of the contribution that aggregated DG may provide to the voltage security of the grid. In particular, a systematic voltage stability analysis is applied to develop bus indices that measure the individual contributions of each aggregated DG to the voltage security margin of the transmission grid in normal operating conditions and during contingencies. Simulations show that the combination of the proposed individual bus indices provides good estimates of the total contribution of DG to the voltage security margin of the grid.