Stability analysis using poincaré map in the time-domain for grid-connected inverter

It is necessary to analyze stability of a grid-connected system. There are two types of the stability analysis methods; one in the frequency domain and the other in the time domain. In this paper, the time domain method using the Poincaré map is investigated because it can analyze the system precisely even if it has nonlinear effects. First its basic principle and physical meanings are described. The proposed time-domain method is based on simple eigenvalue analysis of a sensitivity matrix between the periodic boundary values. However, generally an inverter is a nonlinear system and its switching instances are dependent on operating conditions. It is necessary for computation of the sensitivity matrix to consider sensitivities of these instance variations. The computation algorithm of the sensitivity matrix is precisely described. Then application examples of a grid-connected inverter are analyzed, and the results are investigated for validation of the proposed stability analysis method.