Inverter-based microgrids: small-signal modelling and testing

In this paper, a systematic way of developing a small-signal state-space model of the inverter-based microgrids is presented. Each sub-module is modeled in state-space form and all are combined together on a common reference frame. The complete model is linearized around an operating point and the resulting system matrix is used to derive the eigenvalues. The eigenvalues (termed 'modes') indicate the frequency and damping of oscillatory components in the transient response. A sensitivity analysis is also presented which helps identifying the origin of each of the modes and identify possible feedback signals for design of controllers to improve the system stability. Results from the model are verified against a prototype microgrid experimental setup.