Approximated Power Flow for AC Islanded Microgrids

This paper proposes a new approximated power flow method for islanded AC microgrids. The proposed linear power flow is based on the expansion and improvement of the well-known approximated model for voltage drop calculation in distribution networks based on power injections and the Zbus matrix. The accuracy of this conventional approximation has been improved through the following strategies: linearization based on warm-start and post-solution correction to include the imaginary part of complex voltages. Furthermore, droop controls were embedded into the original approximated model to consider the microgrids islanded operation. The accuracy of the proposed method was assessed using nonlinear optimization models. The tests results with 69 and 906 nodes microgrids demonstrated that the proposed approach is generally more accurate than existing approximated algorithms for solving power flow in islanded microgrids. Furthermore, a computational cost assessment of the proposed technique was performed using a Probabilistic Power Flow (PPF) based on Monte Carlo Simulation. The results revealed that the PPF based on the proposed approach can estimate probabilistic performance indices with high precision, but with reductions of 97% in CPU time.