Power Electronics Modeling Fidelity: Impact on Stability Estimate of Micro-grid Systems

Stability analysis of AC and DC distributed power systems dominated by power electronics devices is a challenge for designers of connected or isolated micro-grids, due to the ideal conditions considered by the manufacturers; this should cause that the system reach an unstable state. This paper focuses in the analysis based on impedance representation of a single phase inverter operating as voltage source, where the Nyquist criteria is realized for a renewable energy micro-grid isolated configuration. Also, three small signal input impedance modeling methods are described, the first is the reduced order modeling methodology or steady state variables averaged model, the second is based on the assumption of no energy storage at the AC and DC side of the inverter, and the third uses an approximation of the impedance with current frequency components. For the three methods a comparative evaluation with the impedance obtained was realized by the application of a voltage perturbation to the DC side. The obtained results show that the proposed method of no energy storage can be employed in the studies of stability for micro grid systems.