A novel measure to characterize bus type assignments of realistic power grids

Electric power engineers and researchers need appropriate randomly generated grid network topologies for Monte Carlo experiments to test and demonstrate new concepts and methods. Our previous work proposed a random topology power grid model, called RT-nested-small-world, based on a comprehensive study of the real-world grid topologies and electrical properties. The proposed model can be used to produce a sufficiently large number of power grid test cases with scalable network size featuring the same kind of small-world topology and electrical characteristics found in realistic grids. However, the proposed RT-power grid model has a shortcoming that is its random assignment of bus types. And our recent study has shown that the bus type assignment of a realistic power grid is not random but a correlated one. Generally speaking,the buses in a power grid can be grouped into three categories: generation buses (G), load buses (L), and connection buses (C). When studying the dynamics of a grid we need to take into account not only its "electrical" topology but also the generation and load settings including their locations, which are equivalent to the bus type assignments in our model. In this paper we define a novel measure to characterize typical bus type assignments of realistic power grids. The proposed measure will enable the recognition of the specific set of bus type assignments, consistent with that of a realistic grid, from those generated from random permutation. This will prove useful for designing an optimal algorithm to improve our random topology power grid modeling. The proposed measure, called the Bus Type Entropy, incorporates both bus type ratios and the link type ratios. Therefore it provides a quantitative means to identify the presence of correlation among the bus type assignments of a realistic grid. We then experiment with this entropy measure on a NYISO system and the IEEE 300-bus system. The numerical results from both test cases verify the effectiveness of the proposed measure to characterize the bus type assignment of a real-world power grid.