Small-Signal Stability Modeling of Islanded Microgrids with Distributed Energy Resources

Abstract

The growth in integration of distributed energy resources (DERs) has added impetus on the implementation of islanded microgrids that bring complicated dynamic interactions understanding system stability. The current paper has provided the general stability modeling strategy of small-scale microgrids comprising several inverter-based DER units in a model. This is achieved through the creation of a single state-space model with inverter dynamic equations, hierarchical control loops, and network equations, modeled about the synchronous dq reference frame. To obtain small-signal model, where stability can be easily analysed using eigenvalues, the nonlinear system is linearised about a steady-state operating point. The suggested framework assesses how the parameters of the key system (such as droop control gains, line impedance and variations of the loads) determine the stability of the system. To detect the prevalent oscillatory modes, key states of the system, eigenvalue migration, damping ratio analysis and participation factor evaluation are applied. Simulation experiments with MATLAB/Simulink have shown that a higher load demand and an incorrect Control tuning of the control system leads to the damping becoming less important and shifting eigenvalues to more unstable eigenvalues areas. These findings also indicate that a system resilience and stability margin are enhanced in case of optimization of the choice of control parameters. The suggested modelling framework offers a convenient analytical framework to assess stability and control design in an islanded microgrid with a high level of DER penetration to facilitate the creation of stable and resilient decentralized power systems.