| Abstract | This paper proposes a generic steady-state modeling and power-flow analysis approach for droop- and isochronously-controlled microgrids. The proposed framework adopts symmetrical sequence component models, rather than phase-coordinate models, of microgrid components. Such approach immensely reduces the power-flow execution time, as it breaks down the system model into independent equation sets with considerably reduced sizes. To render the proposed approach practical and generic, it incorporates unbalanced loads and feeders, transformer connections, different load characteristics and configurations, as well as microgrid droop features. Furthermore, it models and integrates different types and control schemes of distributed generation (DG), including synchronous generator-based DG (SGDG) and electronically-interfaced DG (EIDG) units. A novel power-flow algorithm based on a modified Newton-Raphson (NR) method is proposed to solve for the microgrid steady-state voltage magnitudes, angles, and frequency. The accuracy of the models and algorithm is verified through comparison with detailed time-domain simulations in MATALB/Simulink. Additionally, the proposed algorithm is shown to outperform the reported Newton-Trust Region (NTR) approach in accuracy and computational cost. Two case studies, incorporating IEEE 123-node test microgrid, are further performed to examine the effectiveness of the proposed approach in solving complicated droop-controlled microgrids, and to investigate the behavior of droop-controlled DGs in isochronous microgrids. |
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