For power grid operators, wind farms and solar farms are black boxes since details of inverter technologies, the main component of renewables, are proprietary info. Then, how can a grid operator assess a power grid's stability? We aim to design a toolbox to address this challenge. Julia Admittance will process experiment data and come up with admittance models for wind, solar, etc. With admittance models available, eigenvalues of the system will be computed to assess system stability.