Power grids: Subgrid impedance determination and its structural model parameterization

In the introductory part of the paper problems with power grid impedance determination and interpretation are discussed. Research instrumentation for getting the Thevenin grid model, with raw impedance descriptor in kHz/MHz frequency band is presented and compared. The essential part of this paper is focused on subgrid impedance parameterization which allows to get its physical, circuit based model. With the use of nonlinear fitting the model parameters are tuned to get the lowest discrepancy between the observed and circuit modeled impedance of the subgrid in selected frequency nodes. The physical based subgrid model delivers useful engineering information on the grid and can be easily integrated with simulation programs capable of running reliable software experiments on the simulated grid.