Small-signal modeling and analysis of microgrids including network and VSI dynamics

A systematic approach for the small-signal modeling and stability analysis of microgrids is developed in this paper. The proposed methodology is intrinsically modular, in the sense that models for the system components are individually derived and then aggregated into a single model for the entire microgrid. The latter includes the representation of fast dynamic phenomena that arise with the widespread use of electronically interfaced microsources typical of microgrid applications. Therefore, the dynamics of (i) Voltage Source Inverters (VSIs) and companion LCL output filters; (ii) loads, and (iii) the electrical network, can all be taken into account. The proposed modeling method is applied to a particular microgrid, and the resulting linearized dynamic model is used to perform controller design, microgrid small-signal stability analysis and to investigate dynamic interactions between microsource controllers. The corresponding results are then validated through time-domain nonlinear simulations performed with the PSCAD/EMTDC software package.